Selection and Investigation of Sites for 

the Disposal of Radioactive Wastes in 

Hydraulically Induced Subsurface Fractures

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1215

Prepared in cooperation with the 

U. S. Department of Emr$ for the 

International Atoffiic.Energy Agency
Selection and Investigation of Sites for 

the Disposal of Radioactive Wastes in 

Hydraulically Induced Subsurface Fractures

By REN JEN SUN

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1215

Prepared in cooperation with the 

U. S. Department of Energy for the 

International Atomic Energy Agency

UNITED STATES GOVERNMENT PRINTING OFFICE, W AS HINGTON : 1 98 2
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Sun, Ren Jen.

Selection and investigation of sites for the disposal of radioactive wastes in hydraulically induced subsurface fractures.

(Professional paper-U.S. Geological Survey ; 1215)

Bibliography: p.

Supt. of Docs, no.: I 19.16:1215

1. Radioactive waste disposal in the ground. 2. Waste disposal sites-Location. 3. Nuclear facilities-Waste disposal.

I. Title. II. Series: United States. Geological Survey. Professional paper ; 1215. 

TD898.S873 621.48'38 80-607180

AACR1

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, B.C. 20402
CONTENTS

Page

Nomenclature ____________________________ VI 

Conversion table __________________________ VII

Abstract __

Introduction _________________________________________

Purpose and scope of the report ______________________

Acknowledgments _________________________________

Theory of fracture mechanics ____________________________

Factors controlling the injection of radioactive wastes in

hydraulically induced fractures ______________ 7

Earth stresses _________________________ 7

Vertical earth stress ___________________ 8

Horizontal earth stress __________________ 8

Tectonic stress _______________________ 9

Mechanics of hydraulic fracturing ______________ 9

Stresses around uncased boreholes ___________ 10

Fracturing in cemented and cased holes _________ 11

Fracturing in bedded rocks ________________ 11

Fracturing in fractured and jointed bedded rocks ___ 12

Suitability of various rock types for hydraulic fracturing

and waste injection ___________________ 13

Shale ____________________________ 13

Sandstone and limestone 14

Crystalline igneous and metamorphic rocks ______ 14

Site evaluation ___________________________ 14

Geology _____________________________ 14

Hydrology ____________________________ 14

Geologic stability _______________________ 15

Interference with resources exploitation __________ 15

Site investigation _________________________ 15

Test drilling __________________________ 15

Geophysical logging ____________________ 15

Core analyses _______________________ 16

Strikes and dips of host rocks ______________ 16

Hydraulic fracturing tests __________________ 16

Interpretation of hydraulic-fracturing test data ______ 17

Interpretation of pressure data ______________ 17

Interpretation of uplift data _______________ 18

Interpretation of gamma-ray logs ____________ 19

Safety considerations _______________________ 19

Waste migration due to separation of liquid from grout __ 19

Leaching of grout by ground water ______________ 20

Creation of vertically oriented fractures ___________ 21

Triggering earthquakes by hydraulic fracturing ______ 21

Historical manmade earthquakes ____________ 22

Mechanism for triggering earthquakes _________ 22

The possibility of triggering earthquakes by hydraulic

fracturing and grout injection _____________ 23

	Page

Safety considerations-Continued

Isolation time required for injected wastes 24

Conclusion ___________ 24

References cited _________ 25

Appendixes: Case histories _____ 27

Hydraulic fracturing at West Valley, N.Y _________ 27

Site geology ______________ 27

Well construction _____________________ 29

Injections _________________ 30

Water injection ______________ 30

Grout injection ________________ 41

Summary _____________________ 45

Radioactive waste disposal at the Oak Ridge National

Laboratory, Tenn ____________________ 45

Geology and hydrology _____________ 46

Seismicity ______________________ 52 

Nature of radioactive wastes produced at the Oak Ridge

National Laboratory _____________ 52

Summary of disposed radioactive wastes ____ 54

Injection processes and the disposal plant _______ 55

Injections _____________ 60

Experimental injections _______________ 61

Operational injections ________________ 64

Bleed back through the injection well _____ 64

Position of grout sheet ______________ 67

Monitoring system _____________________ 68

Site evaluation ____________ 70

Test drilling ______________________ 71

Well deviation __________________ 71

Stratigraphy of the injection shale _______ 71

Tensile strength of the injection shale _____ 74

Test injections _____________________ 75

Test grout injection _______________ 76

Interpretation of injection data ______ 77

Altitude of induced fractures ________ 79

Past waste grout sheet intercepted by

the North-observation well _____ 79 

Grout sheet produced by the test grout

injection ________________ 79

Test water injection _______________ 83

Potential for the exhumation of wastes _________ 86

Summary ___________________ 87

ILLUSTRATIONS

FIGURE 1. Photographs of core samples illustrating the typical appearance of grout sheets integrated with shale after grout 

solidification_______________________________________________________________________________________

2, 3. Maps of observed uplift, extent, and thickness of the grout sheet resulting from an injection, at the second experimental site, Oak Ridge National Laboratory, Tenn., on:

2. September 3, 1960 ________________________________________________________________________

3. September 10, 1960 ____________________________________________________________________________

4. Diagram showing the fracturing of a perfect crystal under tensile stresses ______________________________________

5. Schematic diagram showing molecular structures around a fracture tip _________________________________________

Page

2

in
IV CONTENTS

Page

FIGURES 6, 7. Diagrams showing:

6. Two regions of a brittle fracture ______________________________________________ 7

7. Stresses on a small rectangular parallelepiped element located at depth z _______________________ ___ 8

8. Graphs showing hysteresis during loading and unloading in uniaxial compression tests of Bearpaw Shale _________ 9

9. Diagram showing stresses on an infinitely large plate containing a circular hole _______________________ 11 

10, 11. Graphs showing:

10. Stresses on a bedding plane of rock with respect to the axis of an injection well ___________________ 12

11. Tensile stresses on a fracture plane of a natural fracture and bedding plane of rock with respect to the axis of

an injection well _____________________________________________________ 13

12. Diagram of Coulomb-Navier fracture criteria showing how rock failure can be affected by an increase in pore pressure 23

13. Locations of the hydraulic-fracturing test site, West Valley, N.Y ________________________________ 28

14. Diagram showing the observed trend of three principal joint sets, West Valley, N.Y ______________________ 29

15. Schematic diagram of the injection well, West Valley, N.Y __________________________________ 31

16. Well locations, West Valley, N.Y _______________________________________________ 32 

17-23. Graphs, for the water injection at 442 m, West Valley, N.Y., on: 

17-20. Oct. 9, 1969, of:

17. Pressure plotted against time _____________________________ _ 34 

18, 19. Pressure plotted against injection rate:

18. Before a 45 minute pause _________________ ____ _ 34

19. After a 45 minute pause ______________________________ __ 36

20. Pressure decay plotted against time ___________________________ __ 36 

21-23. June 26, 1970, of:

21. Pressure plotted against time _______________________________ ___ 37

22. Pressure plotted against injection rate _________________________ __ 38

23. Pressure decay plotted against time __________________________ __ 40 

24, 25. Gamma-ray activities observed in observation wells along the casing axis, after the water injection at 442 m, West Valley, 

N.Y., on:

24. July 6, 1970 ________________________________________________________ 40

25. Aug. 24, 1970 ________________________________________________________ 41 

26-30. Graphs, for the water injection and the grout injection at 152 m, West Valley, N.Y., on: 

26-28. May 29, 1971, of (water injection):

26. Pressure plotted against time ______________________________ _ 43

27. Pressure plotted against injection rate ___________________ _ 44

28. Pressure decay plotted against time _______________ ___ _ 44 

29, 30. July 23, 1971, of (grout injection):

29. Pressure plotted against time ______________________________ __ 45

30. Pressure plotted against injection rate _________________________ _ 46

31. Gamma-ray activities observed in observation wells along the casing axis, after the grout injection at 152 m, West Valley,

N.Y., on July 28, 1971 ______________________________________________________ 46

32. Uplift produced by the grout injection at 152 m, at West Valley, N.Y ______________________________ 47

33. Calculated and surveyed uplift produced by the grout injection at 152 m, West Valley, N.Y _________________ 49

34. Location of hydraulic-fracturing-experiment sites, present fracturing site, and proposed site, Oak Ridge National

Laboratory, Tenn _________________________________________________________ 50

35. Section showing subsurface geology near the hydraulic fracturing sites, Oak Ridge National Laboratory, Tenn ______ 51 

36, 37. Graphs of:

36. Temperature plotted against depth at the present fracturing site, Oak Ridge National Laboratory, Tenn __ 52

37. Average monthly temperatures and precipitation, Oak Ridge, Tenn _______________ __ 52

38. Location of epicenters near Oak Ridge, Tenn., 1699-1973 ____________________________________ 53

39. Schematic diagram of the hydraulic-fracturing and waste-grout injection facility, Oak Ridge National Laboratory, Tenn _ 55

40. Artist's sketch of the hydraulic-fracturing and waste-grout injection, Oak Ridge National Laboratory, Tenn _______ 56

41. Photograph showing equipment for proportioning and blending dry solids for waste-grout injection, Oak Ridge National

Laboratory, Tenn _________________________________________________________ 57

42. Diagram showing the arrangement of the mass flowmeter in a mixer cell for waste-grout injection, Oak Ridge National

Laboratory, Tenn _________________________________________________________ 58 

43-45. Photographs showing:

43. Conveyors for moving preblended solids from storage bins to a mixer for waste-grout injection, Oak Ridge

National Laboratory, Tenn __________________________________ _ 58

44. Cell enclosing the wellhead of the waste-injection well, Oak Ridge National Laboratory, Tenn _ __ 59

45. Bins, waste-injection wellhead cell, injection pump, and standby injection pump, Oak Ridge National

Laboratory, Tenn ________________________________________ _ 60 

46-48. Schematic diagrams showing:

46. Construction of the waste-injection well, Oak Ridge National Laboratory, Tenn _______ _ 61

47. Wellhead arrangement for slotting by hydraulic jet, Oak Ridge National Laboratory, Tenn _______ 62

48. Slotting operation for hydraulic-fracturing and waste-grout injection, Oak Ridge National Laboratory,

Tenn ________________________________________________________ 63
CONTENTS V

Page

FIGURE 49. Schematic diagram showing wellhead arrangement for waste-grout injection, Oak Ridge National Laboratory, Tenn __ 64 

50. Photograph showing wellhead of an injection well, Oak Ridge National Laboratory, Tenn __________________ 65 

51-53. Calculated and surveyed surface uplift, Oak Ridge National Laboratory, Tenn., produced by: 

51, 52. Grout injection, at the second experiment site, on:

51. Sept. 3, 1960 .________________________________________________ 66

52. Sept. 10, 1960 ________________________________________________ 67

53. Experimental injections 1-7, at the present fracturing site ____________________________ 67 

54, 55. Location at the present fracturing site, Oak Ridge National Laboratory, Tenn., of:

54. Benchmarks .______________________________________________________ 68

55. Observation wells.__________________________________________________- 69

56. Cross section showing the grout sheets formed by waste injections ILW-8 through ILW-14, interpreted from gamma-ray 

logs made in observation wells after the injections and projected on a line in the direction along dip and passing 

through the center of the injection well, Oak Ridge National Laboratory, Tenn ______________________ 69

57. Schematic diagram showing the injection well, .observation wells, and waste grout sheet in shale, Oak Ridge National

Laboratory, Tenn ________________________________________________________ 70

58. Locations of wells at the proposed disposal site, Oak Ridge National Laboratory, Tenn ___________________ 71 

59-61. Graphs, for the test grout injection at 332 m, at the proposed disposal site, Oak Ridge National Laboratory, Tenn., on 

June 14, 1974, of:

59. Pressure plotted against time ____________________________________________ 78 

60, 61. Gamma-ray activities observed, along the casing axis, in the:

60. North-observation well __________________________________________ 80

61. West-observation well ___________________________________________ 81 

62. Location of point of injection and altitudes of gamma-ray peaks observed in observation wells after the test grout injection June 14, 1974, at the proposed disposal site, Oak Ridge National Laboratory, Tenn ________________ 82 

63-65. Graphs of:

63, 64. Gamma-ray activities observed along the casing axis on June 14, 1974, at the proposed disposal site, Oak 

Ridge National Laboratory, Tenn., in the:

63. South-observation well, before and after the test grout injection ___________________ 83

64. New East-observation well, 85 days after the test grout injection __________________ 86 

65. Pressure decay plotted against time, the test water injection at 332 m, Oct. 30, 1975, at the proposed

disposal site, Oak Ridge National Laboratory, Tenn _____________________________ 87

TABLES

Page

TABLES 1-6. Water injection, West Valley, N.Y., on date shown: 

1-4. At 422 m:

1. Injection pressure, Oct. 9,1969 __________________________________________ 32

2. Pressure decay, Oct. 9, 1969 ____________________________________________ 35

3. Injection pressure, June 26, 1970 _________________________________________ 38

4. Pressure decay, June 26,1970 ___________________________________________ 39 

5,6. At 152m:

5. Injection pressure, May 29,1971__________________________________________ 42

6. Pressure decay, May 29,1971 ___________________________________________ 42

7. Injection pressure of the grout injection at 152 m, July 23,1971, West Valley, N.Y _______________________ 43

8. Ground elevation affected by the grout injection at 152 m, July 23,1971, West Valley, N.Y __________________ 48

9. Instantaneous shut-in pressure, calculated overburden pressure, tensile strength of shale, average cohesive force at

fracture tip, and value of/, West Valley, N.Y ________________________________________ 49

10. Approximate waste composition produced at the Oak Ridge National Laboratory, Tenn ____________________ 54

11. Radioactive waste injected in Pumpkin Valley Shale, Oak Ridge National Laboratory, Tenn, 1964-78 ____________ 54

12. Physical properties of grout, injection pressure, calculated grout radius, and maximum fracture separation, September

1960, Oak Ridge National Laboratory, Tenn __________________________________________ 61

13. Chemical composition of waste disposed of by injections, September-December 1972, Oak Ridge National Laboratory,

Tenn_________________________________________________________________ 64

14. Specific activity of major radionuclides contained in wastes disposed of by injections, September-December 1972, Oak

Ridge National Laboratory, Tenn ________________________________________________ 66

15. Bleed back from injections, September-December 1972, Oak Ridge National Laboratory, Tenn ______________ 66

16. Specific activity of radionuclides in bleed back solution, September-December 1972, Oak Ridge National Laboratory, Tenn 67

17. Altitude of grout sheet determined from gamma-ray logs made in observation wells, September-December 1972, Oak

Ridge National Laboratory, Tenn _____________________________________ __ 68

18. Rock-cover wells having positive or negative differences in pressures measured before and during an injection and results

of gamma-ray logs, September-December 1972, Oak Ridge National Laboratory, Tenn _____________ 70

19. ORNL coordinates and altitude of wells at the proposed disposal site, Oak Ridge National Laboratory, Tenn __ 71

20. Data on observations and calculations for a deviation survey at the proposed disposal site, Oak Ridge National Laboratory, 

Tenn., made in the injection well, Old East-observation well, New East-observation well, South-observation well, 

West-observation well, and North-observation well __________________________________ 72
VI CONTENTS

TABLE 21. Observed contact between rock units and calculated dip and strike at the proposed disposal site, Oak Ridge National

Laboratory, Tenn ________________ 74

22. Tensile strength of rocks at the proposed disposal site, Oak Ridge National Laboratory, Tenn 75

23. Injection pressure of the test grout injection at 332 m, June 14, 1974, at the proposed disposal site, Oak Ridge National

Laboratory, Tenn ___________________ 76

24. Waste-grout sheet intercepted by North-observation well from past waste injections made at the present fracturing site,

Oak Ridge National Laboratory, Tenn _________ 79

25. Grout sheet from the test grout injection at 332 m, June 14, 1974, intercepting observation wells at the proposed disposal

site, Oak Ridge National Laboratory, Tenn ______ _ 81 

26, 27. Test water injection at 332 m, Oct. 30, 1975, at the proposed disposal site, Oak Ridge National Laboratory, Tenn.:

26. Injection pressure _____________ 84

27. Pressure decay ___________ _ 85

NOMENCLATURE

D

d

E

F(Q,L,W)

F(Q,r,W)

fT

f

9

H

h 

K

Ka

K,

K

k

L

MD

n

ri

P

PP 

AP

Linear regression constant; instantaneous shut-in

pressure

Radius of induced fracture

Internal radius of a thick wall cylinder; radius of stressaltered fracture region, as shown in fig. 6 

Constant; maximum fracture separation 

Intermolecular distance; external radius of a thick-wall

cylinder 

Constant; activity of a particular radionuclide in waste at

time t; horizontal distance measured perpendicular to

the average strike of shale beds 

Activity of a particular radionuclide in waste at disposal

time

Inside diameter of a pipe; denudation rate 

Diameter of a tested sample; edge region of a fracture, as

shown in fig. 6 

Young's modulus 

Friction loss in a vertical fracture 

Friction loss in a horizontal fracture 

Average cohesive force at a fracture tip 

0</< 1; Fanning factor 

Acceleration due to gravity 

Ratio of basin relief to length; horizontal displacement of

a hole

Depth of induced fracture; length of a tested sample 

Horizontal stress coefficient (ohlo^ 

Coefficient of "active earth pressure" 

Coefficient of "earth pressure at rest" 

Fluid consistence index (kg-force-secTC7m2 ) 

Constant

Fracture length; length of casing 

Depth measured along a casing axis 

Number of half-lives of a particular radionuclide 

Fluid flow behavior index (dimensionless) 

Internal pressure in a thick-wall cylinder; bottom-hole

pressure in injection well; load at rock failure during

tensile-strength test; pressure decay 

Initiation pressure or breakdown pressure to induce a

fracture

Propagation pressure to extend a fracture 

Pressure loss due to friction 

Pore pressure

r 

T

Ta 

Tn

T°y 

T°z

Til/2 

t

u

V

w 

w

Pore pressure

Injection rate; total injection volume

Reynold's number

Radial distance

Tensile strength of rock

Tensile strength of rock parallel to bedding planes

Tensile strength of rock normal to bedding planes

Tensile strength of rock parallel to stress a

Tensile strength of rock parallel to stress az

Half-life of a particular radionuclide

Time

Horizontal movement of ground surface

Flow velocity

Fracture opening

Surface uplift

x-axis; horizontal departure, distance east or west of 

north-south axis

y-axis; horizontal departure, distance north or south of 

east-west axis

True vertical distance between two adjacent measured 

points

z-axis; vertical depth

a'/a; vertical deviation angle; angle with the direction of 

the least principal stress as

Angle of joints with respect to a well axis; magnetic bearing

Weight density of rock

Polar angle from x-axis; dip angle

Poisson ratio

Density

Normal stress

Stress parallel to bedding planes

Stress normal to bedding planes

Horizontal earth stress

Vertical earth stress

Radial stress

Tangential stress

Stress along x-axis

Stress along y-axis

Stress along z-axis; overburden pressure

Principal stresses, the order of magnitude represented 

by subscript numbers, as being the least stress

Shear stress

Angle of internal friction of clastic sediments

Angle of bedding planes with respect to well axis
Multiply metric (SI) unit

CONTENTS

CONVERSION TABLE

VII

to obtain inch-pound unit

Millimeter (mm) 3.9370 x lO'2

Centimeter (cm) 3.9370 x 10'1

Meters (m) 3.2808x10°

Kilometers (km) 6.2137 x 10'1

Square kilometers (km2 ) 3.8610 x 10'1

Cubic meters (m3) 3.5315 x 101

Cubic meters (m3) 2.6417 x 102

Millileters (mL) 2.6417 x 10'4

Millileters (mL) 3.5315 x 10~5

Meters per second (m/s) 3.2808 x 10°

Kilograms per second (kg/s) 2.2046 x 10°

Cubic meters per second (m3/s) 3.5315 x 101

Cubic meters per second (m3 /s) 1.5850 x 104 

Kilogram per cubic meters

(kg/m3) 6.2427 xlO'2 

Kilogram per cubic meters

(kg/m3) 8.3454 xlO-3

Pascal (Pa) 1.4504 xlO'4

Megapascal (MPa) 1.4504 x 102

Curies per liter (Ci/L) 2.8317 x 101

Curies per liter (Ci/L) 3.7854 x 10°

inch (in.)

inch (in.)

foot (ft)

miles (mi)

square miles (mi2)

cubic feet (ft3)

gallons (gal)

gallons (gal)

cubic feet (ft3 )

feet per second (ft/s)

pounds per second (lb/s)

cubic feet per second (fts/s)

gallons per minute (gal/min)

pounds per cubic feet (lb/ft3)

pounds per gallons (Ib/gal) 

pounds per square inch (lb/in2) 

pounds per square inch (lb/in2) 

curies per cubic feet (Ci/ft3) 

curies per gallon (Ci/gal)

SELECTION AND INVESTIGATION OF SITES FOR

THE DISPOSAL OF RADIOACTIVE WASTES IN 

HYDRAULICALLY INDUCED SUBSURFACE FRACTURES

By REN JEN SUN

ABSTRACT

Injection of intermediate-level radioactive wastes (specific activity of 

less than 6x 103/tCi/mL, consisting mainly of radionuclides, such as 

strontium and cesium, having half-lives of less than 50 years) mixed 

with cement into a thick shale formation is a promising and feasible 

disposal method. Hydraulic fracturing provides openings in the shale 

to accommodate the wastes. Ion exchange and radionuclide-adsorption 

materials can be added to the grout during mixing to further increase 

the radionuclide-retaining capacity of the grout. After solidification of 

the grout, the injected wastes become an integral part of the shale formation, and therefore the wastes will remain at depth and in place as 

long as the injection zone is not subjected to erosion or dissolution.

Problems concerning safety of the disposal method are (1) the potential for inducing vertical fractures, (2) phase separation during and 

after the injections, (3) the reliability of methods for determining the 

orientation of induced fractures, (4) the possibility of triggering earthquakes, and (5) radionuclides being leached and transported by ground 

water.

In bedded shale, a difference between tensile strength normal to and 

that parallel to bedding planes favors the formation of fractures along 

bedding planes that are nearly horizontal. Even in areas where vertical 

stress is slightly greater than the horizontal stresses, nearly horizontal 

bedding-plane fractures can be hydraulically induced in shale at depths 

less than 1,000 meters. Test injections should be made during site 

evaluation to determine if horizontal bedding-plane fractures can be induced.

The orientation of induced fractures can be indirectly monitored by 

recording injection pressures during injection time and by measuring 

the decay of water injections and the uplift of ground surface after the 

injections; however, it can be directly determined by gamma-ray logs 

made in observation wells before and after each injection, if the injected fluid or wastes contain enough gamma-ray emitting radionuclides.

If waste grout is properly mixed, phase separation should be less 

than one percent of the total amount injected. The mobility of waste in 

the separated liquid is further decreased by the low permeability (less 

than 10 ~ 6 darcy) and the large ion-exchange and adsorption capacity 

of shale, which thus reduce the potential for contamination.

Grout injections do not cause extensive increases in pore pressure 

within shale, and a disposal site should be located in a geologically 

stable and tectonically relaxed area, that is, an area lacking local active 

faults. Thus a disposal in shale in such areas can avoid the two 

necessary and essential conditions for triggering earthquakes by fluid 

injections, an increase in pore pressure and rock already stressed near 

its breaking strength.

Waste injections are made in several stages at different levels 

through an injection well. After the first series of injections at the

greatest depth, the well is plugged by cement at that depth. The second series of injections are made a suitable distance above the first. 

The repeated use of the injection well distributes the cost of constructing injection and monitoring wells over many injections, thereby making hydraulic fracturing and grout injection economically attractive as 

a method for the disposal of radioactive wastes.

Theoretical considerations about inducing nearly horizontal beddingplane fractures in shale are discussed, as are field procedures for site 

selection, safety, and the monitoring and operation of radioactive 

waste disposal. Case histories are used as examples to demonstrate the 

application of the theory and techniques of field operations.

INTRODUCTION

Radioactive waste is the inevitable byproduct of the 

generation of electricity by nuclear reactors, as well as 

of other nuclear applications. An effective solution to 

the problem of disposing the long-lived and highly toxic 

radioactive waste is essential if the use of nuclear 

energy is to be expanded. Numerous methods for the 

disposal of radioactive waste have been proposed or 

studied in the last two decades. These methods include 

disposal on or in suitable geologic formations, in the 

ocean bottoms (including subduction zones), in polar ice, 

by shooting the wastes into space, and by transmutation 

(Winograd, 1974; Interagency Review Group on Nuclear 

Waste Management, 1979). Judged by existing 

technology, disposal of waste in geologic formations is 

probably the most feasible and practical method among 

the proposed alternatives.

One of the geologic disposal methods is to inject a mixture of intermediate-level radioactive wastes (specific 

activity of less than 6 x 103 /^Ci/mL, consisting mainly of 

radionuclides having half-lives of less than 50 years, 

such as strontium and cesium) and cement and additives 

through a deep well into fractures that have been induced in nearly impervious formations (permeability 

< 10~6D (darcy)) by hydraulic pressure during the injection. The injected grout is allowed to solidify under 

pressure to form grout sheets, which become an integral 

part of the rock (fig. 1); thereby the wastes are immobilized in a desired horizon of the low-permeability 

medium.
SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

GROUT SHEET INTEGRATED 

WITH SHALE AFTER SOLIDIFICATION

GROUT SHEET INTEGRATED WITH 

SHALE AFTER SOLIDIFICATION

1234 

CENTIMETERS

w 5

GROUT SHEET INTEGRATED WITH SHALE AFTER SOLIDIFICATION

456 

CENTIMETERS

10

FIGURE 1. -Photographs of core samples illustrating the typical appearance of grout sheets integrated with shale after grout solidification. Arrows 

indicate the grout sheets. The cores shown here were obtained from different boreholes and are of sheets formed from several injections. 

(Courtesy of Oak Ridge National Laboratory, Tenn.)

The techniques of hydraulic fracturing have been 

widely used in the petroleum industry since 1947 for 

recovery of oil (Clark, 1949; Howard and Fast, 1970). 

However, disposal of wastes by grout injection using 

hydraulic fracturing had not been tested until 1959. In 

1958, D. A. Shock of the Continental Oil Co. suggested 

to the U.S. Atomic Energy Commission (AEC, presently 

the U.S. Department of Energy) that hydraulic fracturing combined with grout injection into impermeable 

rocks might be used for the disposal of highly toxic

radioactive waste (deLaguna and others, 1968). The 

AEC accepted the suggestion, and the Oak Ridge National Laboratory (ORNL), Tenn., was chosen for an experimental site.

Requirements for radioactive waste disposal by this 

technique include the following items: (1) The induced 

fractures should be horizontal or nearly horizontal, and 

(2) the wastes should be contained in a known and welldefined horizon for a sufficient time until the radiation 

emissions from the wastes decay to innocuous levels.
INTRODUCTION

From 1959 through 1960, three experimental injections without wastes were made into the Conasauga 

Shale by hydraulic fracturing at two different locations 

at the ORNL. The grout was tagged with radioactive 

isotope 137Cs. The first injection was at a shallow depth, 

88 m below the land surface. After the injection, 22 core 

holes were drilled near the injection well. The cores provided data that showed the solidified grout sheet to be 

formed nearly parallel to the bedding planes (fig. 1). The 

second and third experiments were made at a new well 

that was drilled 1,830 m east of the first injection well. 

Similar grout was used in these two injections, which 

were made at depths of 285 m and 212 m, respectively. 

After the injections, 24 core holes were drilled near the 

experimental site. The core-hole data confirmed again 

that the grout sheets were formed parallel to bedding 

planes and became an integral part of the shale (fig. 1). 

The grout sheets are confined to an area having a maximum radius of 100 m, and the observed range in 

thickness of the grout sheets is from 3 to 12 mm (figs. 2, 

and 3). A third well having a 14-cm casing was drilled in 

the Conasauga Shale to a depth of 329 m, 0.8 km west of 

the second experimental site. From 1964 through 1965, 

seven experimental injections containing liquid radioactive wastes produced at the ORNL were made. The injections were at progressively shallower depths, from 

288 m to 265 m. From 1966 through 1978, regular waste 

disposal was carried out through the well from depths of 

265 m to 245 m. A total volume of 11,000 m3 of grout 

containing 7,000 m3 of radioactive wastes produced at 

the ORNL was injected. These wastes contained 

640,000 Ci (curies) of radionuclides. Core drilling and 

gamma-ray logs for observation wells constructed near 

the injection well also indicated that the grout sheets 

were formed parallel to bedding planes (deLaguna and 

others, 1968, 1971; Weeren, 1974, 1976).

The demonstration at the ORNL shows that disposal 

of intermediate-level radioactive wastes in bedded shale 

by hydraulic fracturing is feasible. However, most experience with hydraulic fracturing in oil wells indicates 

that hydraulically induced fractures are generally vertical (Hubbert, 1971). Because of this experience, Earth 

scientists advised the AEC, through the U.S. National 

Academy of Sciences, not to extrapolate the results obtained at the ORNL site to other locations (Belter, 

1972).

In view of this advice, the AEC sponsored an experimental program at the Western New York Nuclear 

Fuel Service Center near West Valley, in Cattaraugus 

County, N.Y., carried out jointly by the ORNL and the 

U.S. Geological Survey (USGS), with the permission of 

the State of New York, to test further the concept of disposing radioactive wastes into shale by hydraulic fracturing. The objectives of the program were (1) to demonEXPLANATION

t~J Grout sheet

__3 Q__ Line connecting points

of equal uplift, millimeter

X 1A Benchmark

 so Core hole; number

is measured thickness 

of grout sheet, millimeter

Injection well

6B

0 50 100 METERS 

I____I____i

FIGURE 2. -Map of observed uplift, extent, and thickness of the grout 

sheet resulting from an injection, at the second experiment site, Oak 

Ridge National Laboratory, Tenn., on Sept. 3,1960 (from deLaguna 

and others, 1968).

strate at another location the feasibility of inducing 

bedded-plane fractures in nearly horizontally bedded 

shale through hydraulic fracturing, (2) to develop an 

economical yet practical method for estimating and 

monitoring the orientation of hydraulically induced fractures, and (3) to develop site-evaluation procedures 

(Belter, 1972).

From 1969 through 1971, six hydraulic-fracturing injections, all of water, except the last, which was of 

grout, were made at the West Valley, N.Y., site. Most of 

the injections were tagged with radioactive tracers. The 

injection depths ranged from 152 to 442 m. Conclusions 

reached on the basis of the test results are as follows:

1. At certain shallow depths (less than 1,000 m) 

bedding-plane fractures can be induced 

hydraulically in an approximately horizontally bedded shale in which tensile strength normal to the 

bedding planes is much less than that parallel to 

the bedding planes.

2. The injected grout can be kept within a short 

distance vertically from the injection depth.
SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

EXPLANATION

-xIOD 

\

x9D x

\

\

\

x8D

\

f j Grout sheet

 3.0 Line connecting points

of equal uplift, millimeter

x 1A Benchmark

'3.6 Core hole; number

is measured thickness 

of grout sheet, millimeter

3C

)^

/

/ 

/

/

/ /

/' ~~-^

/ *7D ^

/

/ x6D

7 5D

/ 5 |> -^

2C / x 4D

x / y^!77^

/ ^x3D ^

/ K ?n !2 '° / 1C K tu '2-0 

\

N \

XN \ 

\

\

\

^\ Tfe^ \

^>^ \

X ^

® Injection wel

\

\

\

\ 

x\3E

\

\

50 100 METERS

FIGURE 3.-Map of observed uplift, extent, and thickness of the grout sheet resulting from an injection, at the second experimental site, Oak Ridge National Laboratory, Tenn., on Sept. 10,1960 

(from deLaguna and others, 1968).

3. Existing joints and (or) high-angle fractures in the 

formation may be extended by injection pressure if 

they are intercepted by induced fractures; 

however, the extension will cease when the vertical 

fractures reach weak bedding planes.

4. The orientation of induced fractures can be indirectly 

monitored by recording injection pressures during 

the injection time and by measuring the pressure 

decay of water injections and the uplift of ground 

surface after injection. It can be directly determined by gamma-ray logs made in observation wells 

that were constructed within the area where the 

grout is expected to reach, if the grout contains 

gamma-ray-emitting radionuclides (Sun, 1973; Sun 

and Mongan, 1974).

The present hydraulic-fracturing disposal facility (in 

1981, this facility is still being used for disposal of 

wastes) at the ORNL was designed for experimental injections. Because of the experiments' success, the facility was modified in 1966 to allow for the routine disposal 

of radioactive wastes having a specific activity of less 

than 530 /iCi/mL. Without extensive equipment 

modifications, the facility can not be used for disposal 

either of sludge, of which 1,500 m3 has been accumulated at the ORNL, or of wastes having a specific 

activity greater than 530 /iCi/mL. Also, the disposal 

capacity of the shale underlying the present facility will 

be exhausted between 1985 and 1988 if the present 

waste-generation rate at the ORNL is maintained (U.S. 

Energy Research and Development Administration 

(ERDA), 1977).

In 1973, the ORNL proposed to establish a second 

hydraulic-fracturing disposal facility having the capacity 

to dispose sludges, as well as wastes having a specific activity as great as 6xl03 /iCi/mL. The proposed site is 

245 m south of the present existing site. A site-
THEORY OF FRACTURE MECHANICS

feasibility study was made jointly by the ORNL and the 

USGS in 1974, the study methods applied being those 

developed during the experiments conducted at the 

ORNL and at West Valley, N.Y.

Since enactment of the National Environmental 

Policy Act in 1969, all major government projects require environmental-impact statements, which should 

evaluate all possible environmental impacts of a proposed action, as well as the feasible alternatives to the 

proposed action. The environmental-impact statement 

for the proposed waste-disposal facility at the ORNL 

concluded that the hydraulic-fracturing disposal of 

radioactive wastes at the ORNL is the safest method 

and has the least cost among the alternatives, such as 

tank storage and fixation in glass (ERDA, 1977).

PURPOSE AND SCOPE OF THE REPORT

The feasibility of subsurface disposal by grout injection of certain types of radioactive wastes in hydraulically induced fractures in shale has been studied and well 

demonstrated in the United States. The purpose of this 

report is to provide information to authorities who are 

responsible for planning, approving, and executing 

radioactive-waste management programs to help them 

determine if disposal of intermediate-level radioactive 

wastes (specific activity of < 6 x 103 /iCi/mL consisting 

mainly of radionuclides having half-lives of less than 50 

years, such as strontium and cesium) by hydraulic fracturing is an acceptable alternative. The information 

herein is also intended to be used for the selection and 

evaluation of suitable sites. Safety assessment of the 

disposal method is also discussed. The safety assessment 

is important and necessary for waste-management 

authorities who use the information to compare the 

hydraulic-fracturing disposal technique with other alternatives, so that they can determine if the disposal waste 

can be isolated in a geologic formation, at least for the 

desired length of time.

The report contains sufficient theoretical discussions 

and case histories (in the Appendix) to allow the reader 

to evaluate whether the presented conclusions are 

justified.

ACKNOWLEDGMENTS

This report was sponsored for the International 

Atomic Energy Agency by the Division of Waste 

Management of the U.S. Department of Energy.

The author wishes to thank R. A. Robinson and H. 0. 

Weeren, ORNL, for providing information on hydraulicfracturing disposal at the ORNL. The author also is indebted to R. A. Farrow, USGS, for the determination 

from cones during a site-evaluation study at the ORNL, 

of the tensile strength of shale.

THEORY OF FRACTURE MECHANICS

Rock deformation can be classified into three main 

categories: (1) folds, (2) shear fractures, and (3) extension fractures. Ideally, folds are produced where rock 

under deformation responds without failure (in a 

macroscopic sense) to stresses. Shear fractures result 

where stresses produce movements parallel to the 

plane of the fracture. Faults are special cases of shear 

fracturing. Extension fractures are separations of rocks 

across a surface normal to the direction of the least principal stress without offset or movement parallel to the 

fracture surface. Extension fractures involve loss of 

cohesion, separation into two parts, and release of 

stored elastic strain energy (Badgley, 1965). Joints and 

hydraulically induced fractures are extension fractures.

Three well established theories that can be applied to 

rock fracturing are (1) the Coulomb-Navier, (2) the 

Mohr, and (3) the Griffith (Jaeger and Cook, 1969). The 

first two theories are applicable to rock failure under 

maximum shear stress. The last discusses rock failures 

under tension and can be used to explain extension fractures. Therefore, only the Griffith theory is used to 

discuss hydraulic-fracturing mechanics.

Two stages are involved in fracturing, namely fracture initiation and fracture propagation. Fracture initiation is defined as the failure process by which one or 

more preexisting fractures in rocks start to extend. 

Fracture propagation is a stage subsequent to initiation, 

in which a fracture is extending. Two kinds of propagation may be defined, stable and unstable (Bieniawski, 

1967).

Stable propagation is the process of rupture by which 

the extension of a fracture involves definite relationship 

between the applied stress and the length of the fracture, and the fracture extension can accordingly be controlled. If the extension is governed by factors other 

than stresses-for example, the velocity of propagation-it becomes uncontrollable, and the fracture expands rapidly to complete a rupture of the material, 

where the applied load is constant-for example, a fracture in glass. This kind of propagation is called unstable 

propagation and has dynamic characteristics.

The extension of hydraulically induced fractures is 

dependent on the applied hydraulic pressure; a fracture 

will cease extending when the applied pressure falls 

below a critical level. Therefore, the extension of a 

hydraulically induced fracture is a stable propagation.

When sediments are deposited, individual grains are 

discrete and the sediments are without cohesion. As 

sediments are buried beneath younger deposits, they 

become compacted and cemented, resulting in the cohesion of grains, so that the rock takes on cohesive or 

tensile strength. The greater the cementation and compaction the greater is the cohesion.
6 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

In the propagation of extension fractures, work must 

be done against the stress normal to the fracture plane 

and against the cohesive force of the grains at the fracture tip. As the hydraulic pressure is applied, the preexisting fracture in the rock does not extend while the 

pressure is small. Upon reaching a certain pressure that 

overcomes the sum of the normal stress and the maximum cohesive force at the fracture tip, the fracture 

begins to extend.

The cohesive force under tensile stresses in perfect 

crystals is a function of the intermolecular distance 6 

(Cottrell, 1964; Kunz, 1971), as shown in figure 4. Consider two atomic planes under tensile stresses: the

b 

it

T 

b

(T (tensile stress)

B

Ideal 

tensile 

strength

INTERMOLECULAR DISTANCE

FIGURE 4. -Diagram showing the fracturing of a perfect crystal under 

tensile stresses (from Cottrell, 1964).

molecular cohesive force is zero before the tensile 

stresses are applied; then it rises in proportion to the 

amount of separation between the separated molecules 

and reaches the maximum value when the separation 

has reached approximately one intermolecular distance 

from the equilibrium condition. Further separation will 

reduce the cohesive force, which diminishes nearly to 

zero when the separation between the molecules is 

greater than three intermolecular distances from the 

equilibrium condition. The maximum molecular cohesive 

force defines the ideal tensile strength of the material 

under consideration, that is, the tensile strength of a 

material if it were a perfect crystal. The actual tensile 

strength of a material is commonly several orders of 

magnitude less than the ideal tensile strength because of 

(1) defects of crystal structure, (2) variation in the 

mineralogy of constituent detrital grains and in the extent of cementation in a granular medium, and (3) variation in the type of cement.

Figure 5 shows a schematic, idealized structure of 

molecules around a fracture tip. Consider the fracture 

extending from the left towards the right; the first pair 

of molecules at the fracture tip begin to separate as the 

tensile stresses increase. An increase in the applied 

stresses will increase the separation between the pair. 

The intermolecular distance increases from the 

equilibrium condition 6 to 26, then to 46; at this stage, 

the fracturing process is completed, the fracture extends one molecular distance 6, and the applied stresses 

fall. The second pair of molecules now becomes the new

Fracture surface 

(Inner region)

Fracture surface 

(Inner region) 

A

FIGURE 5.-Schematic diagram showing molecular structures around a 

fracture tip.
THE INJECTION OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

fracture tip. The applied stresses again rise and fall. The 

fracturing process goes on from one pair of molecules to 

the next.

To avoid solving complex nonlinear integral equations 

applied to the fracture problem, Barenblatt (1962) 

divided the fracture area into two regions (fig. 6). In the 

inner region the opposite fracture walls are relatively 

far apart; hence, there is no molecular cohesive force, 

and the fracture walls can be considered as free from 

such stress. The linear theory of elasticity is fully adequate to describe this region. In the edge region, the opposite fracture walls are sufficiently close to each other 

that the molecular cohesive force between them is 

strong. Plastic yielding occurs in this region. To avoid 

the complex nonlinear theory of elasticity and to work 

within the framework of the linear theory, Barenblatt 

made two assumptions to solve the fracture problem: (1) 

The size of edge region of the fracture is small compared 

with the size of the whole fracture, and (2) when the 

fracture extends, the shape of the section normal to the 

fracture surface in the edge region (and consequently 

the local distribution of the cohesive force over the fracture surface) does not depend on the pressure in the 

fracture and is always the same for given conditions of 

temperature and composition. These assumptions are 

here considered to be realistic.

On the basis of these assumptions, the average 

cohesive force at a fracture tip is defined as/77, where T 

is the average tensile strength of the rock and/is a constant that depends on physical properties of the rock. 

The value of/is 0</<1 (Barenblatt, 1962; Kenny and 

Campbell, 1967; Perkins and Krech, 1968; Goodier, 

1968; Rice, 1965).

FACTORS CONTROLLING THE INJECTION OF

RADIOACTIVE WASTES IN HYDRAULICALLY

INDUCED FRACTURES

The technique of disposing radioactive wastes in a 

geologic formation by hydraulic fracturing is to first mix 

the waste with cement and additives and then to inject it 

through a well under pressure. The injection well 

penetrates the host rock and is fully cased and pressure 

cemented between the casing and the formation. A 

horizontal 360-degree slot that cuts the casing and the 

cement wall and penetrates the host rock is made by a 

hydraulic-sand jet before the injection. The applied 

hydraulic pressure separates the rock to form openings 

into which the waste is injected. The fracture at the tip 

of the precut slot is usually initiated by water injection. 

After a fracture has been initiated, waste grout is then 

injected. The injected grout solidifies under pressure. 

After solidification the injected grout becomes an integral part of the host rocks, thereby immobilizing 

waste and restricting it to a definite area. Two or three 

consecutive injections can be made through the same

PLAN VIEW CROSS-SECTION VIEW

FIGURE 6. - Diagram showing two regions of a brittle fracture (from 

Barenblatt, 1962).

slot; thereafter, the well is plugged by cement up to the 

next injection depth, and again a horizontal slot is made. 

Waste injections are made in a sequence from bottom 

upward until the disposal capacity of the injection formation is exhausted.

The major concern about the hydraulic fracturing 

waste-disposal technique is whether horizontal fractures 

can be induced in the host rocks, so that the injected 

waste can be immobilized and restricted to a desired 

horizon. The overwhelming experience of hydraulic fracturing in oil wells indicates that hydraulically induced 

fractures are generally vertical (Hubbert, 1971), an 

orientation that is unfavorable for the disposal of 

radioactive wastes. The possibility of inducing horizontal fractures by hydraulic pressure is discussed in the 

following sections.

The discussions are based on the assumption that the 

injection formation is isotropic and homogeneous. Admittedly this is not the case. Geologic formations, 

especially shale, are generally heterogeneous and 

anisotropic; however, the simplifying assumption appears to be valid in general, as the experiments made at 

the ORNL and West Valley, N.Y. indicate (Sun, 1969, 

1973, 1976; Sun and Mongan, 1974). These experiments 

are presented in the appendix.

EARTH STRESSES

In the propagation of a fracture at depth, the applied 

pressure in the fracture must overcome the stress normal to the fracture plane and the cohesive force at the 

fracture tip. Therefore, during hydraulic fracturing the 

amount of earth stress normal to the fracture plane 

must be considered.

The amount of stress at a given point and at a particular depth generally results from three types of stress 

components. They are (1) gravitational stress, (2) tectonic stress, and (3) fluid pressure within the rock.

Gravitational stress results fundamentally from the 

weight of overlying rock. Two aspects of this stress need 

to be differentiated: (1) stress effects that result from
SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

the present topographic conditions and (2) stress effects 

that result from past topographic conditions. Tectonic 

stresses are induced by mobility of the Earth's crust 

resulting from various influences as temperature and 

geochemical effects, and fluid pressure is caused by fluid 

in pores, such as oil, gas, and water.

VERTICAL EARTH STRESS

Consider a small element of rock at a depth z in a 

Cartesian coordinate system having its z-axis vertical 

(fig. 7). The equation of equilibrium in terms of vertical 

stress (Jaeger and Cook, 1969) is given by

dz dy dx

where az is the vertical stress, ryz and rxz are shear 

stresses, and p and g are density of the rock and acceleration of gravity, respectively. 

Integrating equation (1) with respect to z:

a =yz dy

tdrxz

- \z-^dz, 

Jox

0

(2)

where y is the weight density (pg) of overlying rock. 

Howard (1966) stated that there are only three special 

cases of equation 2 in which the vertical stress is equal to 

the weight of overlying rock per unit area, but only two 

of them are considered to be geologically acceptable.

Case L -In regions of gentle topography and simple 

geologic structure there are no shear components along 

the air-earth interface; then

T« = T,a = 0, (3)

and the vertical stress is simply equal to the weight of 

overlying rock per unit area.

Case £.-Through relaxation of rock by creep over 

long periods of time the shear stress diminishes; then

dz = 0, (4)

and the vertical stress is again equal to the overburden 

pressure.

Case 3. -The shear stresses along the x and y axes are 

equal to each other but in opposite directions; thus,

a

f^Z 

J dy

0

dz. (5)

This case is geologically improbable, and the condition is 

very restrictive, especially when compounded by the 

choice of geographic direction for the x and y axes.

Air-Earth interface

FIGURE 7.-Diagram showing stresses on a small rectangular 

parallelepiped element located at depth z.

Therefore, it can be concluded that in a relatively flat 

area having a simple geologic structure, the vertical 

stress can be calculated as the weight of overlying rock 

per unit area. However, in a topographically irregular 

area or in a region having a complex geologic structure, 

the vertical stress may or may not be the overburden 

pressure alone.

HORIZONTAL EARTH STRESS

No adequate analytical models are available to 

estimate horizontal stresses. However, experiences in 

soil mechanics can be used to help explain the relation 

between the horizontal and the vertical stresses.

Consider, for example, the simple case of an accumulation of clastic sediments subject to a principal stress 

solely derived from overburden pressure. The stressstrain relationship is a function of the mobilized friction 

coefficients between individual clastic particles, the 

structural arrangement of the particles, and the elastic 

constants of the particles. The ratio of horizontal to vertical intergranular stresses corresponding to a condition 

of zero lateral strain is called the coefficient of "earth 

pressure at rest" and is denoted by K0 (Voight, 1966). 

The empirical relationship is given by

= 0.95 -sin 0, (6)

where 4> is angle of internal friction of the clastic 

sediments (Brooker and Ireland, 1965; Voight, 1966).
THE INJECTION OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

It should be emphasized that very small strains have a 

marked effect on the value of horizontal stress. It was 

found that strains on the order of 10~3 are sufficient to 

fully mobilize the shear strength-that is, to reduce the 

ratio of horizontal to vertical stress to the coefficient of 

"active earth pressure," Ka (Voight, 1966), where

Ka = (1 - sin 0)/(l + sin 0). (7)

Very little is known about the precise nature of lateral 

restraint to be found at a geologic scale. Voight (1966) 

believed that horizontal strains may in fact vanish for 

certain types of sedimentary basins. The horizontal 

stress coefficient^, which is defined as ah/av, must lie between the limiting values of the "active earth pressure" 

and "earth pressure at rest" and is given by

(1-sin 0)/(l + sin 0)<<7h/av < (0.95-sin 0). (8)

In general, the angle of internal friction, 0, is 27-30° 

for unjointed hard sedimentary rocks, such as sandstone 

and limestone, and 0-20° for soft sedimentary rocks, 

such as shale and clay (Fenner, 1938; Harrison and 

others, 1954; Perkins, 1967; Jaeger and Cook, 1969). 

Then, the ratio of horizontal to vertical stresses, ahlav , 

can be considered to be between 0.33 and 0.55 for hard 

sedimentary rocks and between 0.49 and 0.95 for soft 

rocks. The average measured ohlov in sedimentary basins 

in the United States containing sandstone and shale is 

0.6 (McGarr and Gay, 1978).

Laboratory experiments show that a hysteresis effect 

exists during loading and unloading of rocks (Brooker 

and Ireland, 1965; Voight, 1966); therefore, horizontal 

stress is higher during unloading than loading (fig. 8). If 

this hysteresis effect exists in areas that have 

undergone significant denudation or ice-sheet unloading 

in the Quaternary Period, then horizontal stress 

probably would be higher than that calculated on the 

basis of the present overburden pressure.

TECTONIC STRESS

The earth stresses discussed in the preceding sections 

are only gravitational. In addition, rocks are also subjected to tectonic stress. Unfortunately, no analytical 

theory is available to estimate tectonic stresses. It also 

should be noted that regions subjected to current tectonic stresses are not only those that are seismically active. Nor are such regions necessarily characterized by 

tectonic structures that reflect the past stress distribution. Current stresses need not bear a geometrical relation to structures produced in prior deformational 

phases. There is much geologic evidence for areas subjected to multiple deformations that indicates 

characteristically significant changes in stress orienta12r46 8 10 12 14 

VERTICAL STRESS, IN MEGAPASCALS

18

FIGURE 8.-Graph showing hysteresis during loading and unloading in 

uniaxial compression tests of Bearpaw Shale (from Brooker and 

Ireland, 1965).

tion over time. Moreover, significant current tectonic 

stresses can exist in regions regarded as geologically 

stable (Voight, 1966). Thus, although the observation 

and description of geologic deformational structures 

provide irrefutable evidence of past tectonic activity and 

the past distribution of stresses, geologic structures can 

be used only as guides in studying the current earth 

stresses; the actual stresses can only be determined in 

place.

MECHANICS OF HYDRAULIC FRACTURING

The mechanics of hydraulic fracturing are well 

documented (Hubbert and Willis, 1957; Haimson, 1968; 

Haimson and Fairhurst, 1969; Howard and Fast, 1970; 

Daneshy, 1967, 1973), and only the conditions that are 

needed for inducing horizontal fractures are discussed 

herein.

Fracture walls can be classified in two categories on 

the basis of the lithologic characteristics of an injection 

formation: (1) Both walls are relatively impermeable as 

are those of fractures formed in thick shale, and (2) one 

or both walls are permeable, as are those of fractures 

formed along the interface of shale and sandstone or 

within sandstone. One of the required conditions for the 

disposal of radioactive wastes is that there be a 

minimum possibility of grout leaching by ground water 

and of grout dilution during injection; therefore, it is 

mandatory to select low permeability formations (< 10~6 

D) as injection host rocks. Also the injection well should 

be cased and pressure cemented along its full length. 

Therefore, only the case of fractures having relatively 

impervious walls induced by nonpenetrating fluid is considered in the following sections.
10 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

STRESSES AROUND UNCASED BOREHOLES

During injections, hydraulically induced stresses 

around the well can be determined by thick-wall-cylinder 

stress equations (Timoshenko and Goodier, 1951). The 

induced radial stress ar, tangential stress at , vertical 

stress az, and shear stress r of a thick-wall cylinder subject to internal pressure P, are given by

ar = [a2P/(&2 - a2)][(62/r2) - 1],

o= -

and

(9)

(10)

(11)

where a is the internal radius of the thick-wall cylinder, 

b is the external radius, r is the radial distance from the 

center of the cylinder to a desired point, and 6 is the 

polar angle from x-axis. The negative sign represents 

tension.

Because the injection well is constructed in a thick impervious formation that extends radially to a great 

distance, the value of b can be considered to be very 

large as compared with the value of well radius a. Equations 9, 10, and 11 can be rewritten as

and

ar =P(a2lr2), 

at =-P(a2/r2 ),

(12)

(13)

(14)

The induced radial and tangential stresses will reach 

maximum (the value of P) at the well face and diminish 

abruptly away from the well.

The effects of a well on a preexisting stress field can 

be calculated by analogy with an infinitely large plate 

subjected to uniaxial stress and containing a circular 

hole whose axis is perpendicular to the plate, the equation for which was solved by Kirsch in 1898 (Timoshenko 

and Goodier, 1951). The stresses near a well subjected to 

two horizontal stresses ax and ay , can be obtained by the 

Kirsch solution and the law of superposition (fig. 9). The 

results are given by

-4a2/r2)cos20, (15) 

r4) cos20, (16)

and

Mr^-Ko,-^

ar9 = [(ox - a )/2Xl - 3a4/r4 + 2a2/r2) sin20, (17)

where a is the radius of the well, r is the radial distance 

from the center of the well, and 6 is the polar angle 

counterclockwise from the x-axis (fig. 9).

From equations 15 and 17, it can be seen that the 

radial and shear stresses are zero at the well face and increase abruptly toward the undisturbed earth stresses 

over a distance equal to a few well diameters. Equation 

16 shows that at the well face (r=a) the tangential 

stress reaches a minimum value at 6 = 0° and 0 = 180°, 

with a magnitude of (3oy -ax) if ax >ay . This minimum 

stress can be either compressional or tensional depending on the ratio of ax/ay . When ax is greater than 3ay the 

stress is in tension. The maximum stress on the well face 

is at 0=90° and 0 = 270°, with a magnitude of (3ax - oy) 

and is always in compression. In the case where both 

horizontal stresses are equal (ax = ay), the tangential 

stress around the well face is the same everywhere, with 

a magnitude of 2ah .

In conclusion, the effect of a well on horizontal 

stresses is localized to within distance equal to a few well 

diameters. Beyond that distance, earth stresses will be 

undisturbed.

The linear theory of elasticity is assumed to be approximately valid in hydraulic fracturing, and therefore 

stresses around the injection well can be superimposed; 

that is, the resultant of the induced stresses around the 

injection well is the algebraic sum of the induced 

stresses produced by the hydraulic pressure in the well 

and the distorted stresses due to the presence of the 

well.

In the initiation of a vertical fracture, the initiation 

pressure P., which is commonly called "breakdown 

pressure," should be equal to or greater than the sum of 

the minimum effective tangential earth stress at the 

well face and the tensile strength of the rock in the 

direction normal to the fracture plane. The 

mathematical expression for initiation of a vertical fracture can be obtained from equations 13 and 16, and 

when r=a, 0 = 0°, and 0 = 180°, the result is

Pi-P^(0y -P^-(ox -P^-To , ifax >ay, (18) 

or

P.*3a,-as -P0 -Tv (19)

where Ta is the tensile strength of the rock in the direction of a^and is considered to be negative, and P0 is the 

pore pressure at a depth where the hydraulic fracturing 

is being made.

Because the presence of a well distorts the existing 

stresses only in an area within a distance of a few well 

diameters from the well, the required "propagation 

pressure," Pp to extend the initiated vertical fracture is 

the sum of the minimum effective earth stress, the 

cohesive force at the fracture tip, and the fluid frictional 

loss in the fracture. The mathematical expression is 

given by

+F(Q,L,W),ifax >ay, (20)

or

PP >oy -fTa +f\Q,L,W), (21)
THE INJECTION OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES 11

i i r i i i

rtt

FIGURE 9.-Diagram showing stresses on an infinitely large plate containing a circular hole.

where F(Q,L, W) is the fluid frictional loss in the fracture 

and is a function of injection rate, Q, the length, L, and 

the opening, W, of the fracture.

Without packers, a horizontal fracture cannot be induced at the well face, because no vertical stress can be 

produced in the injection well. Only if there is an artificial horizontal cut or some existing horizontal fractures at the well face is it probable that horizontal fractures can be induced.

FRACTURING IN CEMENTED AND CASED HOLES

In the case that the injection well is cased and 

pressure cemented over its full length, before injection, 

a horizontal 360° cut is made by hydraulic sand jetting. 

The cut, which extends about 30 cm into the host rock, 

serves as a plane of weakness. During an injection, the 

wellhead is enclosed, and the injection fluid enters the 

cut and creates vertical stresses.

Due to the additional tensile strength (at least several 

tens of megapascals) provided by casing and cement and 

to the precut weak horizontal plane at the well face, the 

induced fracture is undoubtedly in the horizontal direction, at least within moderate depths of several 

thousands of meters, in spite of the horizontal direction 

of the least principal stress. However, at greater depths, 

the additional tensile strength provided by the casing 

and cementing may be overcome by the great overburden pressure, and thus a vertical fracture could be induced at cemented and cased wells.

In areas where the least stress (sum of the earth stress 

and the cohesive force at the fracture tip) is in one of the 

horizontal directions, even if the fracture initiated at the 

well face is horizontal the induced fracture should 

become vertical as the fracture propagates away from 

the injection well, so that the plane of the fracture will

be normal to the least stress and the required work to 

rupture the rock is minimum.

The breakdown pressure to form a horizontal fracture 

is equal to or greater than the sum of the vertical stress 

(a) and the tensile strength of the rocks in the vertical 

direction. The mathematical expression is given by

The propagation pressure is

(22)

(23)

where Ta is the tensile strength of the rock in the vertical direction and F(Q,r, W) is the fluid frictional loss in 

the fracture and is a function of injection rate, Q, the 

radial distance, r, and the opening, W, of the fracture.

FRACTURING IN BEDDED ROCKS

Experimental results and geological observations 

show that bedded rocks have strength anistrophy or 

directional tensile strength. Because of low cohesion 

between bedding planes and because of the lineation of 

clay mineral and microfractures parallel to bedding 

planes, bedded rocks frequently have the smallest tensile strength normal to bedding planes and have the 

greatest tensile strength parallel to bedding planes. 

Laboratory data indicate that the value of the tensile 

strength of bedded rocks, such as shale, normal to bedding planes ranges from about 20 to 80 percent of the 

values parallel to bedding planes, but in most cases the 

value is on the order of 30 percent (Hobbs, 1964; 

Chenevert and Gatlin, 1965; Youash, 1965; Obert and 

Duvall, 1967).

Let ap a2 , and a3 be three principal stresses of different magnitudes. The order of magnitude is 

represented by the subscript numbers, respectively, a3 

being the least stress. If the stress condition that is the 

most favorable for producing vertical fractures is 

assumed, then the maximum principal stress, ap should 

be vertical and the least stress, a3 , lies in one of the 

horizontal directions. Also if the bedding planes of the 

host rock make an angle of co with the well axis (fig. 10), 

then the stresses along the bedding planes, aa , and normal to bedding planes, an , can be calculated by Mohr's 

stress circle and are given by

aa = (ffl + a3 )/2 + [(ffl - <73 )/2]cos2u, 

on = (ffl + a3)/2 - [(ffl - <73)/2]cos2o;,

and

(24)

(25)

(26)

Pressure required to initiate a fracture along or normal to bedding planes should be equal to or greater than
12 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

v=V'-

P=^*\

RADIAL DISTANCE

FIGURE 10.-Graph showing stresses on a bedding plane of rock with 

respect to the axis of an injection well.

the sum of the stress given by equations 24 or 25 and the 

tensile stength of the rock parallel to (Ta ) or normal to 

the bedding planes (Tn). The mathematical expressions 

are given by

Pt > (a, + a3 )/2 + [(a, - a3 )/2]cos2o, - Ta (27) 

for a fracture initiated parallel to the bedding planes and

P, > (ffj + a3)/2 - [(ffl - a3)/2]cos2a3 - Tn (28)

for a fracture initiated normal to the bedding planes.

The pressure required to propagate a fracture along 

or normal to bedding planes should be equal to or 

greater than the sum of the stress given by equations 24 

or 25, the cohesive force at the fracture tip, and the fluid 

frictional loss in the fracture. The mathematical expressions are

PP >(a1 + (73)/2-[(a1 -(73)/2]cos2a3 -/rw +F(Q,r,^) (29) 

for a fracture extending normal to bedding planes and

PP > (a, + a3)/2 + [(ffl - a3)/2]cos2o3 -fTa +F(Q,r, W) (30)

for a fracture extending parallel to bedding planes. The 

condition for extending a bedding-plane fracture is as 

follows:

(a1 + a3)/2 - ((a, - <73)/2]cos2o> -fT^fa + a3)/2

+ [(ffj - a3)/2]cos2a> -fTa (31)

When co is equal or less than 45°, a bedding-plane fracture is always to be extended. However, when o> is

greater than 45°, then the condition for extending a 

bedding-plane fracture is

(32)

Let/= 0.3 (Perkins and Krech, 1968; Sun and Morgan, 

1974); ah /av = 0.7 (see the section Horizontal earth 

stress); and Ta = W MPa, Tn = 2 MPa (table 27), and 

av = 25 MPa/km (Hubbert, 1957). The following table 

summarizes the probably depth that bedding-plane fractures would be induced hydraulically (eq 32):

Bedding-plane angle with well axis, in 

degrees, o>

Depth, in meters, for extending beddingplane fractures in areas where the least principal stress is horizontal

0-45 ______________________________ All depths. 

50 _________________________________ < 1,800

60 _________________________________ < 640 

75 _________________________________ <370 

90 (horizontal bedding) ______________________ < 320

FRACTURING IN FRACTURED AND JOINTED 

BEDDED ROCKS

Virtually all rocks, including glacial tills, have fractures or joints. Some investigators have believed that 

hydraulic pressure in the injection well causes joints or 

existing fractures to extend (Bugbee, 1953; Heck, 1955, 

1960) and, therefore, that the orientation of hydraulically induced fractures is controlled by joints or by existing natural fractures; hence, the orientation could be 

predicted by studying the surface joint patterns (Overby 

and Rough, 1968). However, laboratory studies by 

Lamont and Jessen (1963) showed that the orientation 

of hydraulically induced fractures would be determined 

primarily by the orientation of the least principal stress; 

hence hydraulic fractures can extend across preexisting 

joints or fractures. The location of an existing plane of 

weakness as joints and fractures does not alter the 

orientation of induced fractures appreciably. Are the 

latter statements true; if so, under what conditions?

Again it is assumed that (1) the dominant principal 

stress, alf is vertical and the least principal stress, a3 , 

lies in one of the horizontal directions and that (2) the existing fracture or joint plane makes an angle f3 and the 

bedding planes make an angle 03 with the well axis (fig. 

11). Under such conditions the pressure required to 

propagate an existing vertical fracture is given by

PP > (a, + a3)/2 - [(ffl - a3)/2]cos2j8 -/ Tncos(u - 0)

, r,

The pressure required to extend a bedding-plane fracture is given by

, r, W).(34)
THE INJECTION OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES 13

RADIAL DISTANCE

FIGURE 11.-Graph showing tensile stresses on a fracture plane of a 

natural fracture and bedding plane of rock with respect to the axis of 

an injection well.

The condition for propagating a bedding-plane fracture without extending an existing fracture is that the 

value of Pp calculated by equation 34 should be less than 

that calculated by equation 33. The result is given by

[(a, - a1 )/2]cos2o) -/ Tn < [(as - a1 )/2]cos213 -

In the case of vertical joints, that is, 0 = 0°, equation 35 

can be written as

[(a3 - a1 )/21cos2o> -/ Tn < (a8 - aJ/2 -

In the case of horizontal bedding planes containing vertical joints, that is o> = 90° and |S = 0°, then equation 35 

can be reduced and is given by

Based on the same values discussed in the previous 

section, the following table summarizes the probable 

depth at which vertical joints would not be extended by 

the bedding-plane fractures. It can be concluded that at 

a shallow depth (<400 m), vertical joints would not be 

extended in a formation having strong directional tension strength, even in an area where the maximum principal stress is vertical.

SUITABILITY OF VARIOUS ROCK TYPES FOR HYDRAULIC 

FRACTURING AND WASTE INJECTION

The host injection rock should be of very low intrinsic 

and fracture permeability (<10~6 D), so that groundwater movement in the injection zone is extremely slow.

Bedding-plane angle with well axis, 

degrees a

Depth, in meters, for not extending vertical 

joints when bedding-plane fractures are induced in areas where the, least principal, 

stress is horizontal

0 (vertical bedding) _______ Bedding plane coincides with

joints; Therefore, vertical 

joints are extended at all 

depths.

15 _________________________________ < 1,500 

30 ___________________________________ < 750 

45 ___________________________________ < 510 

60 ___________________________________ < 400 

75 ___________________________________ < 350 

90 (horizontal bedding) _______________________ < 320

The injection rock also should be characterized by appreciably lower tensile strength normal to rather than 

parallel to bedding planes, so that bedding-plane fractures can be induced hydraulically. The suitability of 

various rock types for radioactive waste disposal by 

hydraulic fracturing is discussed on the basis of these requirements in the following sections.

SHALE

The permeability of shale lacking closely spaced fractures or joints is low, generally ranging from 10 ~ 6 to 

10- 9 D (Magara, 1978; Davis, 1969; Young and others, 

1964).

Layered sedimentary rocks commonly have directional tensile strengths (Hobbs, 1964); however, the difference in tensile strength between that normal to and 

that parallel to bedding planes is more dominant for 

bedded shale than for other sedimentary rocks. Field 

evidence indicates that joints or fractures in shale 

generally stop at well-bedded and poorly cemented 

zones.

Direct measurements of in-situ stresses in sedimentary rocks suggest that the minimum horizontal principal stress in shale is nearly equal to the overburden 

pressure in geologically stable areas; however, the 

horizontal stresses measured in other sedimentary 

rocks, such as sandstone, are generally much less than 

the overburden pressure (Simonson and others, 1978).

Shale also contains a large amount of clay minerals, 

which commonly have a large adsorption capacity for 

radionuclides. Therefore, if some radionuclides are 

leached out of a grout sheet, the clay minerals in shale 

can further retard their movement.

To summarize, shale typically provides the following 

properties favorable for radioactive-waste disposal by 

hydraulic fracturing: (1) Susceptibility to the induction 

of nearly horizontal bedding-plane fractures, (2) bedding 

planes that probably inhibit the extension of existing 

vertical fractures and joints, (3) extremely slow groundwater movement, and (4) further retardation by clay 

minerals of most radionuclides leached from the grout.
14 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

Therefore, shale is an excellent host rock for the 

disposal of radioactive wastes by grout injection and 

hydraulic fracturing.

SANDSTONE AND LIMESTONE

The permeability of sandstone and limestone generally ranges between 10- 1 and 10~ 4 D (Davis, 1969), 

which is about five orders of magnitude greater than the 

permeability of shale. Further, the difference in tensile 

strength normal to and that parallel to bedding planes is 

small; therefore, except under particular circumstances, 

sandstone and limestone are not recommended as host 

rocks for disposal of radioactive wastes by hydraulic 

fracturing.

CRYSTALLINE IGNEOUS AND METAMORPHIC ROCKS

The permeability of most crystalline igneous and 

metamorphic rocks is probably of the same order of 

magnitude or even lower than that of shale; however, 

the differences between the directional tensile 

strengths, as related to bedding planes, diminish. On the 

other hand, most crystalline rocks are considerably fractured vertically. Nearly horizontal fractures probably 

can be induced hydraulically only in the areas where the 

least principal earth stress is vertical, that is, in areas 

having residual stresses evidenced by earth movements 

or in areas undergoing large induced isostatic rebound. 

Unless field evidence or in-situ stress measurements indicate that the least principal earth stress is vertical and 

that closely spaced vertical fractures are lacking, 

crystalline igneous and metamorphic rocks should not be 

considered as host rocks for radioactive-waste disposal 

by hydraulic fracturing.

SITE EVALUATION

The geohydrologic investigation during site evaluation 

should cover an area of at least several square 

kilometers beyond that of the site under consideration 

and should include items discussed in the following sections.

GEOLOGY

Well-bedded shale containing nearly horizontal and 

loosely cemented bedding planes, and lacking known 

faults or closely spaced joints or natural fractures appears to be the best injection formation. Shale is frequently interbedded with other sedimentary rocks, such 

as sandstone or limestone. If possible, densely interbedded shale should not be selected as host rock.

To insure inducing nearly horizontal bedding-plane 

fractures and to reduce the complexity of interpreting

investigation results, areas of simple geologic structure 

and flat topography are preferred. Areas of great 

topographic relief and complex geology should be 

avoided if possible. The host rock should be at depth 

shallower than 1,000 m, thus reducing the potential for 

inducing vertical fractures.

The possibility of chemical and physical changes of 

rock characteristics by waste injection needs to be 

evaluated. Normally, characteristics of shale will not be 

changed or altered by wastes as long as radioactive 

decay does not raise the temperature above 100° C. 

However, at elevated temperatures in shale, 

montmorillonite-illite undergoes a phase transition involving an increase in illite and the liberation of free 

water. This water plus preexisting pore water is probably in the form of steam or, at least, hot water. Oxygen, 

carbon dioxide, hydrogen sulfide, and other gases may 

also be released. Interaction among preexisting 

minerals, volatile components, and waste is promoted by 

high temperatures. Experience indicates that hot moving fluids may alter existing minerals and form new 

ones, thus causing significant changes in permeability 

(Bredehoeft and others, 1978) and adsorbability. 

Because of limits in knowledge, it is recommended that 

radioactive waste whose decay results in temperatures 

greater than 100° C at the disposal depth should not be 

disposed in shale or other rocks by grout injection and 

hydraulic fracturing without further studies.

HYDROLOGY

The major concern about hydrology related to the 

disposal of radioactive wastes by hydraulic fracturing is 

ground-water movement. It is preferable to know the 

regional and local ground-water flow in the host rock. 

Based on this information the average travel time of 

ground water to points of discharge can be estimated. 

Ground-water investigation methods have been well 

documented (Hantush, 1964, Walton, 1970; Bear, 1972; 

Prickett and Lonnquist, 1971; Freeze and Cherry, 1979) 

and are not discussed in this report.

Information on total sediment load carried by streams 

in the area of a proposed disposal site is also valuable. 

This information can be used to estimate long-term erosion rates.

Surface runoff not only is one of the major forces for 

erosion but also can be a source or sink of local groundwater flow. Therefore, it is important to understand the 

interaction between streamflow and ground-water flow 

and the depth of the interaction. Ideally interaction is 

limited to approximately the upper few tens of meters 

below the ground surface, well above the injection rock, 

which should be at a depth of at least several hundred 

meters.
SITE INVESTIGATION 15

GEOLOGIC STABILITY

The chance of successfully immobilizing radioactive 

wastes in injected rocks depends on the disposal site 

being geologically stable for many thousands of years so 

that radionuclides can decay to a point at which their 

concentrations no longer constitute a health hazard. 

Tectonism, diapirism, volcanism, glaciation, climatic 

change, seismicity, and erosion are the major activities 

causing geologic instability. Presently no reliable 

methods can be used to predict these activities over 

millions of years. However, if injected wastes are diluted 

to produce lower concentrations (below the specific activity 6 x 103 ^Ci/mL, as done at the ORNL) and are 

limited to radionuclides, such as 90Sr and 137Cs, having 

half-lives of less than 50 years, then the time period for 

which geologic stability has to be anticipated can be 

reduced to about one thousand years. The reliability of 

predictions is increased considerably for this time period 

(Interagency Review Group on Nuclear Waste Management, 1979). It is still impossible to predict precisely the 

behavior of the grout and the ability of rocks to adsorb 

the radionuclides of the waste. However, the degree of 

uncertainty of prediction is reduced greatly.

Past geologic events such as faulting, glaciation, and 

seismicity have not been random; therefore, past 

records might be used for estimation. Regional on-site 

stress measurements are used not only to estimate or 

determine whether nearly horizontal bedding-plane 

fracture can be induced but also to evaluate geologic 

stability. Any evidence of local tectonic instability or of 

seismicity should be a definite cause for the area's 

elimination from consideration for disposal sites.

INTERFERENCE WITH RESOURCES EXPLOITATION

Resources beneath the injection zones can be 

developed after the disposal of wastes as long as precautions are taken during the construction of mining shafts 

or drill holes. Because the solidified grout sheet becomes 

an integral part of the host rock, penetration of radiation to mining shafts can be avoided or reduced to 

acceptable levels by sealing off the injection zone by use 

of strong casing and thick cement walls. If doubts remain on the acceptability of placing mining shafts 

through the injection zone, the future value of potential 

resources must be weighed against the benefits of 

disposing the radioactive wastes.

SITE INVESTIGATION

After a site is selected, the site must be investigated 

specifically to see whether nearly horizontal beddingplane fractures can, in fact, be induced without the 

possibility of inducing vertical fractures and whether 

the permeability of the host rock is sufficiently low. The

site investigaton should follow the procedures discussed 

in the following sections.

TEST DRILLING

At least one core hole is needed to obtain geophysical 

logs and to determine on-site subsurface geology, including lithology, frequency and condition of joints or 

fractures, the elastic constant, and the directional tensile strength of the host rock.

If possible, the core hole should be drilled using air. 

The core hole should be tested by injected water to 

determine formation permeability; if a significant 

amount of water is transmitted by interconnected joints 

or fractures, then the selected site should be abandoned. 

The core hole should be drilled to the full depth in which 

injection is to be made. If all evidence indicates that the 

selected site is suitable for waste disposal then the core 

hole can be constructed to be either a future injection 

well or one of the observation wells. An injection well is 

cased with fairly heavy casing and pressure cemented to 

its full depth. An observation well also should be cased 

with strong tubing or casing and pressure cemented to 

its full depth. The size of observation wells should be 

large enough to allow free movement of a logging probe 

along the well and free movement of drilling tools if a 

well is to be serviced after completion.

If the core hole is converted to an injection well, then 

at least four observation wells should be constructed in 

the same manner as the injection well at a radial 

distance of about 50 m from the injection well but of a 

smaller diameter of casing. These observation wells are 

to be used in locating the position of induced fractures 

after each fracturing, if the injection fluid is tagged with 

gamma-ray-emitting radionucludes.

GEOPHYSICAL LOGGING

In addition to such geophysical logs as an electric log, 

a caliper log, and a fracture televiewer log for lithologic 

identification, determination of borehole conditions, and 

presence and altitude of joints and fractures, gammaray logs and borehole-deviation logs must be run in all 

wells. Deviation logs are used to obtain the true position 

and vertical distance of the well at any desired depth. 

The following formulas (Gatlin 1960) are suggested to be 

used in calculating the true positions:

Z=MDcosa,

H=MDsina,

y=Hcos(3,

(38)

(39)

(40)

(41)

where

Z=the true vertical distance between well survey 

points 1 and 2,
16 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

= the measured distance along the well axis between points 1 and 2,

H=the horizontal displacement of the well at any 

desired depth from the well center at the surface,

y = the horizontal north or south departure distance 

from the east-west axis at any desired depth

# = the horizontal east or west departure distance 

from the north-south axis at any desired 

depth (the origin of the east-west and the 

north-south axis is located at the surface of the 

well).

a = the vertical deviation angle determined from the 

deviation log, and

jS = the bearing (compass direction) determined 

magnetically during logging.

A whole well-length gamma-ray log should be carefully run in all wells before and after each injection. The 

logs should be recorded on paper, rather than by visual 

inspection during logging. A full-length gamma-ray log 

not only gives opportunities for careful office studies but 

also serves as a public documentation of the site investigation.

The initial gamma-ray logs made during well construction are used not only to identify rock units but also to 

serve as baseline information on the natural gamma 

radiation of the rock. The baseline information is to be 

compared with the logs made after an injection to determine the location and depth of the induced fractures 

near the observation wells.

To reduce the complexity of comparing the preinjection and postinjection gamma-ray logs, logs should be 

run at the same speed and instrumental settings. Variation of instrumental settings during logging not only increases the complexity of data interpretation but also increases chances of missing evidence for the determination of induced fractures.

CORE ANALYSES

Cores obtained at a potential injection zone should be 

used for determining the tensile strengths, the elastic 

constants, the permeability (vertical and horizontal), 

and the radionuclide-adsorption capacity of the rock. 

These data are useful for the study of the safety of the 

radioactive-waste disposal at the site.

STRIKES AND DIPS OF HOST ROCKS

The average strike and dip of the selected host rock 

should be measured or estimated. These data are used in 

the prediction and confirmation of induced beddingplane fractures near observation wells. This prediction 

and confirmation increases the reliability of siteinvestigation results and the confidence in the disposal 

method.

Strike and dip of rock units can be calculated from 

gamma-ray logs and the three-point method described 

by Lahee (1952, p. 711-714) and from surface-mapping 

data. The results discussed in the appendix (p. 74) indicate that the method was reliable when used in the 

ORNL site evaluation.

HYDRAULIC FRACTURING TESTS

The selected site should be tested by actual injections. 

At least one water injection and one grout injection, 

each having a total volume of about 400 m3 , should be 

made to determine whether bedding-plane fractures can 

be induced. Each of the injection tests should be made 

with a short-lived gamma-ray-emitting radioactive 

isotope. The probable altitude and orientation of induced 

fractures should be projected before injection by using 

the calculated strike and dip of the rock unit. After injection, the predicted altitudes and orientation of the induced fractures should be checked using the gamma-ray 

logs made in observation wells after the injection.

A water injection should be made first. The purpose of 

a water injection is to ascertain whether the injected 

shale has very low permeability and no interconnecting 

fractures and to determine the vertical earth stress, 

which may or may not be the weight of overburden at 

the site. (For example, Moye (1958) pointed out that the 

field-measured vertical earth stress is about 1.3 to 2.1 

times greater than the calculated overburden pressure 

at Tumut Valley, Snowy Mountains, Australia.) The 

wellhead of the injection well should be closed under 

pressure upon termination of the water injection, so that 

pressure decay in the well can be observed thereafter. If 

the pressure decay is very slow (wellhead pressure is 

maintained for weeks or months), it indicates that the 

injection rock is sufficiently impermeable to groundwater movement. If nearly horizontal bedding-plane 

fractures have been induced, as indicated by gamma-ray 

logs made in observation wells after the injection, the 

vertical earth stress can be calculated from the pressure 

decay-time data (see the next section). The information 

on vertical earth stress at the site is useful for safety 

monitoring during waste injections. If the injection 

pressure falls below the calculated vertical earth stress 

during a waste injection, the injection should be terminated immediately to ascertain whether induced fractures have intercepted an extensively interconnected 

joint system or have become vertically orientated.

Some investigators may question the wisdom of 

having a water injection during a site investigation 

because they believe that several hundred cubic meters 

of water may be left in the host rock. The water could
SITE INVESTIGATION 17

mix with the injected grout during future waste injections and adversely affect the retention of radionuclides. 

However, the host rock is probably already saturated 

with water. The injected water eventually leaks out of 

the induced fractures, despite the low permeability of 

the rock, into the rock mass during the period of constructing the disposal equipment, if the site is selected. 

The volume of water injected would be small compared 

with the total volume of water held by the host rock in 

the injection zone. Therefore, the water left in the host 

rock by a water injection should not disturb the formation and, thus, no adverse effect would be anticipated 

during waste injection.

The importance of a grout injection during a site investigation is that it not only will simulate actual waste 

injections but also can confirm the results obtained from 

the water injection. Such a confirmation is important for 

increasing confidence in the suitability of a site for 

waste disposal.

INTERPRETATION OF HYDRAULIC-FRACTURING 

TEST DATA

Injection pressure, pressure decay, and uplift produced by injections give indirect evidence of the orientation of the induced fractures. Gamma-ray logs made in 

observation wells after and before each injection give 

the actual orientation of the induced fractures within 

the area between the injection well and the observation 

well, if the injection fluid is tagged with gamma-rayemitting radionuclides.

INTERPRETATION OF PRESSURE DATA

Injection pressure, pressure decay, rate of injection, 

and volume of injection should be observed at the 

wellhead of an injection well. Pressure decay of a water 

injection is a complicated phenomena. At the present 

time, no analytical solution has been established. An 

empirical relation between pressure decay and time has 

been found during field experiments at West Valley, 

N.Y. (Sun and Mongan, 1974); the relationship is given 

by

P-PQ = Ct~k , (42)

where P is the observed pressure decay at a particular 

time t and P0 is the formation fluid pressure at the injection depth. C and k are constants. Plotting (P-P0 ) 

against t on a log-log graph paper should result in a 

straight line if k remains unchanged. However, if the 

geometry of the induced fractures changes, then the 

value of k will change.

As the well is shut in, the fluid pressure in the induced 

fracture is much higher than the fluid pressure in the 

formation surrounding the fracture; thus, water starts 

to flow from the induced fracture into the formation, 

despite the low permeability of the host rock. Fluid

pressure in the induced fractures declines, thus 

affecting the fluid pressure in the injection well, and the 

plot of the observed (P-P0 ) against t on a log-log graph 

paper will fall on a single line. As soon as the fluid 

pressure in the induced fracture is reduced to a value 

that is less than the effective earth stress normal to the 

fracture plane, the fracture is reduced in size. The 

pressure decay in the induced fracture is thus affected 

not only by water leaking out of the fracture but also by 

the reduction of the fracture volume; therefore, the 

slope of the line of (P-P0 ) plotted against t will change. 

The pressure at the discontinuity point of the (P-P0 ) 

and t curve can be interpreted as the effective earth 

stress normal to the fracture plane. If the evidence obtained from gamma-ray logs made in observation wells 

after the injection indicates that nearly horizontal 

bedding-plane fractures have been induced, then the 

vertical earth stress, az, can be estimated as the pressure 

at the discontinuity point shown by the (P-P0 ) and t 

curve.

Injection pressure is composed of three elements: 

(1) breakdown pressure, (2) propagation pressure, and 

(3) instantaneous shut-in pressure. Breakdown pressure 

and propagation pressure have been defined previously 

(p. 10). Instantaneous shut-in pressure is the pressure at 

the instant the injection pump is stopped. At this time, 

no fluid is entering the injection well; therefore, the flow 

resistance in the induced fracture is zero, and the instantaneous shut-in pressure is equal to the sum of earth 

stress normal to the fracture plane and cohesive force at 

the fracture tip. From equation 23, it can be shown that 

the propagation pressure is equal to the instantaneous 

pressure after the injection pump has stopped.

If flow through induced fractures is assumed to be 

laminar and to obey Darcy's law, at least for water injection, then the injection pressure at the well should be 

linearly proportional to the injection rate. This assumption has been proved to be correct by using a polynomial 

regression on the injection data observed at the West 

Valley site, N.Y.; F-tests on data for the site showed 

that only the linear term of injection rate, Q, has 

significance statistically (Sun and Mongan, 1974).

During the stage of fracture initiation, the injection 

pressure must be built up to overcome the tensile 

strength of the rock. After the rock is broken, the injection pressure gradually decreases to the required propagation pressure. During this transitional stage, the injection pressures are not linearly proportional to the injection rates. Excluding these pressures, a linear regression equation can be established and is given by

PP =A+BQ, (43)

where Pp is the bottom-hole injection pressure, Q is the 

injection rate, and A and B are regression constants. If a
18 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

nearly horizontal bedding-plane fracture has been induced, then A is the sum of the vertical earth stress and 

the cohesive force,/?7, at the tip of the induced fracture. 

The reliability of the regression constant A can also be 

checked by observed instantaneous shut-in pressure; 

that is, when Q is equal to zero,

PP =A, (44)

where A is the instantaneous shut-in pressure.

If a nearly horizontal bedding-plane fracture has been 

induced, the tensile strength of the rock can be 

estimated from equation 22 and is given by

T.=«.-Pf (45)

where T0g is the tensile strength normal to bedding 

planes, az the vertical earth stress, andPi the breakdown 

pressure.

After the tensile strength normal to bedding plane 

and the vertical earth stress have been determined, the 

cohesive force at the tip of the nearly horizontal 

bedding-plane fracture can also be calculated by equations 23 and 44; it is given by

a-fT =A.

z J a

(46)

After the tensile strength normal to nearly horizontal 

bedding planes of the rock, the vertical earth stress at 

the site, the cohesive force at the fracture tip, and the 

pressure required to overcome flow resistance have 

been determined or estimated, then the breakdown and 

propagation pressures can be forecast. The predicted 

values are to be used in safety monitoring during waste 

injection. The foregoing discussions are illustrated by 

the case histories presented in the Appendix.

INTERPRETATION OF UPLIFT DATA

A large amount of foreign material is injected into a 

host rock, which must yield space to accommodate the 

injected material. Because only nearly horizontal 

bedding-plane fractures are expected to be induced at a 

waste-disposal site, the dominant force applied to the 

host rock during injection should be nearly vertical. No 

significant amount of injected fluid is expected to leak 

out of the induced fractures during injection, and the 

fractures will not be closed completely by the vertical 

earth stress after solidification of the grout. Uplift of 

ground surface is expected to result from injections. 

Field experiments at the ORNL and West Valley, N.Y. 

indicate that ground surface had been uplifted by injections (deLaguna and others, 1968; Sun, 1969; Sun and 

Mongan, 1974; Weeren, 1974).

Sun (1969) demonstrated an example of the rational 

approach to the study of the uplift problem. He first 

assumed the host rock to be an impervious, 

homogeneous, isotopic, and elastic medium. He then 

developed a mathematical model for calculating the 

amount of uplift of ground surface, the separation of 

horizontally induced fracture, and radius of extension of 

fracture. From the analysis of field data, he obtained a 

reasonable agreement between predicted and observed 

data (Sun, 1969; Sun and Mongan, 1974). Several examples of predicted and observed uplift data are_shown 

in the case histories in the Appendix. The uplift, W, and 

the horizontal displacement, U, of the ground surface, 

the maximum fracture separation, B, and the radius of 

the induced fracture, a', can be estimated by the following equations (Sun, 1969):

sin (6/2))- ((h/a Vfe) cos (6/2)], (47)

fc sin (6/2))/[(h+a V& cos (0/2))2 + (a

+ a Vfe sin (0/2))2 ] - [h Vfe cos (6/2) - a V& sin (6/2) 

+ ak cos 6]/[(h V& cos (6/2) -a Vfe sin (6/2) + ak cos 0)2 

+ (a Vfe cos (6/2) + h^k sin (6/2) + ak sin 0)2 ]}, (48)

B = 8(1 - V2)(PP - az)a2 a/TrE, (49) 

(l- a^ = (Pp _ az)/Pp, (50)

and

where

a= a'/a= - v2)a5(PP - (51)

k = [(r2 /a2 + h2/a2 - 1)2 + (2h/a)2 ]*;

6= arc cot [(r2 + h2 - a2)/2ah];

h = depth of the induced fractures;

r = radial distance from the injection well;

a' = radius of an induced fracture from the injection well;

a = maximum radius of stress-altered fracture 

region, shown in figure 6;

a =a'/a;

v = Poisson ratio;

E = Young's modulus; 

Pp = injection pressure at the injection depth;

az = vertical stress or overburden pressure; and 

Q = total injection volume.

Comparison of the predicted value and core-hole data 

observed at the ONRL site indicated that the fracture 

area is sometimes elongated instead of circular (fig. 2). 

However, no grout sheet was observed beyond an area 

twice the calculated radius (Sun, 1969). Therefore, for 

safety monitoring purposes, some observation wells
SAFETY CONSIDERATIONS 19

should be constructed in a perimeter four to five times 

the calculated radius of the induced fractures. None of 

the injected grout sheets should be detected by gammaray logs as extending to those wells.

INTERPRETATION OF GAMMA-RAY LOGS

If bedding-plane fractures are induced, then the 

altitude of the induced fracture near an observation well 

can be estimated by the following equation:

Fracture altitude = altitude of the injection

level ±Ctan0, (52)

where C is the horizontal distance measured perpendicular to the average strike of the shale beds between 

the injection altitude and the altitude of an induced fracture at the observation well; 6 is the average dip angle. 

A plus or minus sign should be used according to the 

direction of dip. For observation wells located updip of 

the injection well, it should be a plus sign; otherwise it is 

a minus sign. The estimated altitude should be compared 

with the observed altitude of the induced fracture determined from gamma-ray logs made in the observation 

wells after an injection. Because of well deviations, the 

comparison of estimated and observed fractures should 

be made at the time after the true horizontal position 

and true depth are calculated from well-deviation 

records. The intensity of gamma-ray activity that indicates induced fractures reaching the observation well 

should be several orders of magnitude higher than the 

background value of the host rock. If the amplifier range 

of the logging unit is kept constant, the evidence of induced fractures reached the well should be clearly indicated by gamma-ray logs made in observation wells 

before and after an injection.

SAFETY CONSIDERATIONS

The potential for waste migration during and after 

waste injections and other adverse effects resulting 

from waste disposal, such as the triggering of earthquakes must be evaluated when the method of disposal 

of radioactive waste by grout injection and hydraulic 

fracturing is considered among other alternatives.

Ideally, after solidification of the grout, the injected 

wastes should become an integral part of the host rock 

and remain there as long as the host rock is not subjected to severe erosion and dissolution. However, a 

number of questions concerning the safety of the 

method have been raised. They are (1) whether liquid 

waste might separate from the grout during and after 

injection and migrate through existing fractures or 

joints, (2) whether waste can be leached out of grout 

sheet by ground water, (3) whether the method for

determining with certainty that the orientation of the induced fractures is horizontal, or nearly so, are reliable, 

(4) whether grout injection and hydraulic fracturing 

have potential for triggering earthquakes, and (5) what 

is the safe isolation time required for the disposed 

wastes. These concerns are discussed in the following 

sections.

WASTE MIGRATION DUE TO SEPARATION OF LIQUID 

FROM GROUT

One of the major concerns about waste migration and 

this disposal technique is radionuclide-loss from the injected grout while it is still in the liquid phase and 

radionuclide-loss from the fraction remaining in the liquid phase through phase separation during solidification. These two losses can be eliminated or reduced 

through a correct solids to waste mixing ratio and by 

carefully selecting solids through laboratory experiments with simulated or actual wastes. The criteria 

of mixing are as follows:

1. Slurry consistency must remain stable and pumpable 

for several hours during injection but must permit 

setting soon after completion of injection (24 hours 

or less).

2. Free liquid separated from grout during solidification 

should be as low a quantity as possible and should 

contain no, or only very small, quantities of radionuclides.

3. The leach rate of radionuclides from solidified grout 

should be low and decrease rapidly with time.

4. Within a tolerable compressive strength of grout, the 

weight of cement added to waste should be kept 

low, thus reducing cost and increasing volume of 

waste to be disposed.

The criteria can be achieved by a proper selection of cement and additives and of correct mixing ratios, as 

determined in a laboratory.

Experiments at the ORNL indicate that both 

radiocesium and radiostrotium reacted rapidly with 

solids in mixing. Very little 90Sr (less than 2 percent) was 

found in the liquid phase after contact with solids. The 

rapid reaction of 90Sr with small particles might be explained on the basis of the composition of Portland cement. Portland cement is composed mainly of calcium 

silicates, which react with water to form hydrated 

calcium silicates. Since strontium and calcium have 

similar chemical behavior, 90Sr rapidly entered into the 

reactions that are common to calcium (deLaguna and 

others, 1968).

Retention of radiocesium by cement solids has proved 

to be unsatisfactory (about 70 percent). Bentonite was 

used as an additive at the ORNL to provide the capacity 

for the retention of radiocesium in slurry and for reducing fluid loss; however, under a high molarity of salt
20 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

solutions-in excess of 5 M-bentonite flucuates and is 

ineffective as a suspending agent. Attapulgite, known to 

be more effective than bentonite as a suspending agent 

in such solutions, was therefore substituted for bentonite. To further improve radiocesium retention, illite 

clay was added to the ORNL wastes.

Pozzolanic material, such as fly ash, is also found to be 

effective and can improve radiostrontium retention and 

reduce required amounts of cement, thus reducing the 

cost of the mix.

Length of pumping time can be controlled by adding 

different amounts of delta gluconolactone (DGL). Phase 

separation was found to be highly sensitive to the composition of waste and of solids. Both DGL and attapulgite were found to affect phase separation. The 

greater the content of attapulgite, the lower the phase 

separation, but also the more viscous the slurry. Greater 

amounts of DGL can reduce the slurry viscosity-however, at the expense of increase phase separation. The ultimate blend of solids can only be determined 

through laboratory experiments. The following mixing 

procedure recommended by the ORNL for wastes 

similar to those produced in the ORNL is listed for 

reference (deLaguna and others, 1969; H. 0. Weeren, 

written commun., 1980).

1. Sample and analyze the waste to be injected.

2. Prepare a solids blend containing the following materials:

Percent by weight

Portland cement type I, gypsum retarded or equivalent ___ 38.45 

Pozzolan ______________________________ 38.45 

Attapulgite gelling clay _____________________ 15.38 

Illite ________________________________ 7.69 

Delta gluconolactone _______________________ 0.03

3. Prepare a slurry using 550 cm3 of waste in 1-L 

blender. Add the solids, using 15 seconds to pour 

into a blender and 35 seconds of additional stirring. 

Record the amount of solids. The blender is 

calibrated to rotate at 2,000 rpm at no load.

4. Pour the slurry into a 250-mL graduate to estimate 

the phase separation.

5. After 2-4 hours, determine the phase separation. 

The increase or decrease in the proportion of solids 

is dependent on the phase separation. If no phase 

separation occurs, decrease the amount of solids to 

obtain the minimum solids content necessary to 

prevent phase separation. Generally a 5-10 percent 

change in solids is sufficient to obtain a slurry having no phase separation.

6. Increase the addition of solids by 10 percent over the 

amount that yielded no phase separation, and mix 

as in step 3. (The increase over the minimum 

amount is suggested to allow a ± 10 percent in the 

control of the solids-to-liquid proportioning.) Determine the pumpable time (thickening time) of the 

slurry by measuring its viscosity. 

7. Increase or decrease the delta gluconolactone (DGL) 

content to obtain the desired pumpable time; 

redetermine the phase separation if the DGL content is changed. The desired pumpable time 

depends on the volume of waste to be disposed of 

and the rate of injection.

No matter how well or carefully the slurry is mixed, 

phase separation is unavoidable; however, the quantity 

of the unbound water in the injection zone can be reduced by back bleeding after the grout solidifies. Experience at the ORNL indicates that the concentration 

of radionuclides in bleed-back water is low (table 16). In 

rocks having low permeability, such as shale, unbound 

water probably would be trapped in the grout sheets; 

this has been indicated during drilling at the ORNL site. 

If some of the unbound water does move away from the 

grout sheet, then the small quantity of radionuclides in 

the unbound water would probably be further reduced 

by adsorption or by decay and dispersion if the flow path 

from the disposal site to the discharge area is long. 

Nevertheless, the disposal site should be monitored by a 

series of observation wells constructed along the 

perimeter of the disposal site, as well as in the overlying 

formation above the injection zone.

LEACHING OF GROUT BY GROUND WATER

In order to reduce the leaching of radionuclides from 

the grout by ground water to the lowest rate possible, 

studies using different minerals as additives over a wide 

range of particle sizes and size distribution are important. The overall results of the ORNL grout mixture 

tested by a modified IAEA (International Atomic 

Energy Agency) 1971 testing method (Moore and 

others, 1975; Moore, 1976) indicated that the grout 

could give leach rates comparable with those obtained 

for waste incorporated in borosilicate glasses. The leach 

rates of the radionuclides contained in the ORNL waste 

are in the following order: Cs> Sr>Cm>Pu. The maximum amount of radionuclides leached from the grout 

sheet seems independent of the type of water, such as 

tap water, ground water, or sea water (Moore and 

others, 1975). The cumulative fraction of cesium and 

strontium leached from grout depended on the time and 

manner of curing. The amount of leached radionuclides 

decreased with an increase in curing time. Short-term 

(140 days) leach studies at the ORNL indicated that increasing the overall waste concentration had little effect 

on the leachability of strontium or cesium (Moore, 1976).

Core grout (cured underground for about 10 months) 

was also used in leaching studies at the ORNL. Because 

the thin grout sheets in the core did not have a uniform
SAFETY CONSIDERATIONS 21

geometry, the grout was ground and sieved, and only 

those particles passing a mesh screen having a 

250-/*-diameter hole were used in the studies. Leaching 

was carried out in plastic bottles containing 1 g of solids 

per 100 mL of distilled water. The results from use of 

grout containing illite show that less than a few hundredths of a percent of the injected amount of radionuclides was leached out of the grout during a 

504-hour test (Tamura, 1971). Conditions of these 

leaching studies deviate greatly from those in the 

ground. Cores of the grout sheets obtained at the ORNL 

indicate that the solidified grout sheets are strongly integrated with shale (see fig. 1); therefore, the chance for 

groundwater to move through the solidified grout sheets 

is probably less than that implied by fine particles of the 

ground grout in contact with distilled water. On the 

other hand, the laboratory studies were made over extremely short periods, and the results may be different 

from those of long-term leaching by ground-water flow. 

However, the low permeability, high ion-exchange and 

adsorption capacity of shale, size of the shale body 

(several hundreds of meters in thickness), and low concentration of radionuclides in liquid during phase 

separation and leaching suggest that the possibility of 

contamination of the biosphere by injected radioactive 

wastes is likely to be remote. If a very low concentration 

of radionuclides did reach a water source, then the concentration of radionuclides would be further diluted by 

that water body.

CREATION OF VERTICALLY ORIENTED FRACTURES

Careful monitoring of injection pressure during injection time will give indirect indication of the orientation 

of induced fractures. Any sudden drop in injection 

pressure, especially when the pressure is near or below 

the estimated vertical stress, will be a positive signal to 

stop the injection in order to evaluate the cause. 

Gamma-ray logs made in observation wells will give 

positive evidence of the fracture orientation, and the 

more observation wells used the better the determination of orientation. The possibility of inducing vertical 

fractures should be fully evaluated during site investigations and carefully monitored during each injection.

TRIGGERING EARTHQUAKES BY HYDRAULIC FRACTURING

In 1965, Evans (1966) showed a correlation between 

pressure of fluid injection, the volume of liquid wastes 

injected into a 3,660-m disposal well at the Rocky Mountain Arsenal, Denver, Colo., and the number of earthquakes reported in the Denver area. He concluded that 

the waste injection at the arsenal well had caused the

Denver area earthquake. In December 1965, the U.S. 

Geological Survey, in cooperation with the Colorado 

School of Mines, Regis College, and the University of 

Colorado, undertook a series of studies to determine the 

relationship, if any, between the disposal of wastes in 

the arsenal well and the location and frequency of earthquakes. The results of these studies supported Evans' 

conclusion (Healy and others, 1966).

In February 1966 the disposal well was shut down. 

Despite the cessation of injection, earthquakes continued to plague the Denver area through August 1967. 

Two earthquakes (magnitude 5.0 of Richter scale, April 

10, 1967, at a depth of 5 km), the largest in Denver area 

since 1882, were strongly felt throughout the Denver 

metropolitan area. Because these seismic events occurred 14-18 months after termination of the well injection, Major and Simon (1968) concluded that the correlation between fluid injection and earthquake occurrence 

upon which Evans based his view had been reduced. The 

overall number of earthquakes in the Denver area, 

however, has declined exponentially since 1967. This 

reduction of earthquake occurrence suggests that 

tremors in the Denver area were caused by release of 

tectonic stresses and that deep-well injection was simply 

the triggering force (Sun, 1977).

In 1969, the U.S. Geological Survey in cooperation 

with the Chevron Oil Co. studied the relationship between fluid injection for water flooding of the Rangely 

Oil Field, Rio Blanco County, Colo., and the number of 

earthquakes in the area and installed 16 seismographs 

around the oil field. It concluded that (1) there is an apparent relation between the number of earthquakes and 

the annual volume of injected fluid, (2) changes in the 

quantity of injection of fluid are related to changes in 

the number of earthquakes recorded, and (3) parts of the 

field lacking natural faults do not produce earthquakes, 

even when the pore pressures in the rock are quite high 

(Gibbs and others, 1972). In November 1970, four injection wells straddling a fault zone were backflowed to 

reduce the pore pressure in the hypocentral region. The 

wells were backflowed and pumped for a period of 6 

months. Within a very short time following the initiation 

of backflowing, earthquake occurrence within an area of 

about a 900-m radius of the backflowing wells decreased 

markedly in frequency and ultimately almost ceased 

(Raleigh, 1972).

From the foregoing discussion it can be concluded that 

injection of fluid does have the potential to trigger 

earthquakes under certain conditions. It is important to 

know if disposal of radioactive wastes through grout injection and hydraulic fracturing also has the potential to 

trigger earthquakes. The following discussion evaluates 

this potential.
22 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRALILICALLY INDUCED FRACTURES

HISTORICAL MANMADE EARTHQUAKES

Manmade earthquakes associated with dam construction have long been acknowledged and well documented. 

Carter (1945, 1970) associated earthquakes near Hoover 

Dam, Boulder City, Nev., with the filling of Lake Mead. 

He suggested that the earthquakes around Lake Mead 

were directly or indirectly a result of fluctuation in surficial crustal loading. Anderson and Laney (1975), 

however, offered a different explanation. They suggested that a hydraulic connection between the lake 

water and the deep aquifer system, which includes 

buried faults, is needed to cause the release of seismic 

energy in the Lake Mead area. Where hydraulic connection between the lake and the aquifer is prevented by 

strata of very low permeability (evaporites), as in the 

eastern basin, seismicity does not occur despite the 

large volume of impounded water in the area.

The Palisades Reservoir, in southeast Idaho, also triggers earthquakes. Epicenters are concentrated near the 

reservoir, and the number of earthquakes is related to 

water fluctuations in the reservoir. Schleicher (1975) 

suggested that the area around the Palisades Reservoir 

would almost certainly be subject to earthquakes even if 

the reservoir were not there. The effect of construction 

of the reservoir was to trigger faulting when tectonic 

stresses were on the verge of causing it anyway.

Earthquakes attributed to the fluctuation of water 

levels and the filling of reservoirs are also reported and 

documented in other parts of the world. For example, 

Marathon and Kremasta Lakes in Greece, Vajont Dam 

in Italy, Lake Eucumbene in the Snowy Mountains in 

Australia, Kariba Dam in Rhodesia, and Koyna Dam in 

India were all in areas in which small to moderate earthquakes began a few months after river closure (Carter, 

1970). All these reservoirs are located in areas that were 

generally considered aseismic; however, potentially active or active faults are found in all these reservoir sites 

(Carter, 1970).

Even river flooding has been related to the occurrence 

of earthquakes. McGinnis (1963) observed that an abnormally large number of earthquake epicenters have been 

detected within 320 km of New Madrid, Mo. The area is 

composed of extensive alluvial valleys, is extensively 

fractured, and shows evidence of major and minor 

faults. McGinnis concluded that the correlation of the 

mean monthly river stage and the earthquake frequency 

in the alluvial valleys indicates that an increase in the 

rate of change of water-load variation tends to increase 

earthquake activity.

MECHANISM FOR TRIGGERING EARTHQUAKES

The mechanism by which earthquakes are triggered 

by man's activity is not clearly known. However most investigators (Healy and others, 1966; Carter, 1970; Gibbs 

and others, 1972; Schleicher, 1975) generally agree that 

the following conditions are associated with manmade 

earthquakes:

1. Rock at the site must be under high stress and near 

its breaking strength or on the brink of sliding on a 

preexisting fault plane or planes.

2. The rock is possibly associated with a potentially 

active fault or faults.

3. Change of pore pressure in the rock is probably the 

triggering force.

If rock pores are saturated with water, then the rock 

is also subject to a hydraulic pressure, P0 , throughout 

the interconnected pores. The three principal earth 

stresses, <TI, a2 , a3 will be reduced to <7i-P0 , a2 -P0 , and 

<73 -P0 , and the normal and shear stresses acting across 

a plane perpendicular to oi, a3 plane and making an arbitrary angle a with the direction of the least principal 

stress, <73 , are given by (Hubbert and Rubey, 1959) as

a= I cos2a-P0

and

T= .

sm2a.

(53)

(54)

The relation of pore pressure to rock failure is shown 

in figure 12. At first, the rock is assumed to be dry and 

under three principal stresses of differing magnitude 

and is not subject to fracture. Now, without changing 

the magnitude of the principal stresses, let the rock be 

saturated with water and the pore pressure in the rock 

increase from 0 to P0 . From equation 53, it is seen that 

the diameter of the Mohr circle remains constant but 

that the center of the Mohr circle is moved towards the 

left along the normal stress axis by a distance equal to 

the pore pressure, P0 , as shown in figure 12. If the pore 

pressure is continuously increased fromP0 to P0 + AP0 , 

the diameter of the Mohr circle still remains constant, 

but the center of the circle is translated farther left by a 

distance equal to the increment of the pore pressure 

AP0 . Obviously, if the pore pressure in the rock increases sufficiently, the Mohr circle will be continuously 

moved to the left until it touches the Mohr envelope (line 

of fracture), and then the rock starts to fracture (Hubbert and Ruby, 1960; Jaeger, 1962).

Injection of fluid and seepage from reservoirs certainly will increase pore pressure in the rock. If rock in the 

area of a potentially active fault or faults has already 

been stressed to the verge of breaking, then the increasing pore pressure would positively contribute to the 

fracturing or slippage of the rock. Fracturing and (or) 

slippage of rock would release elastic energy that had 

already been stored in the rock, thus triggering earth-
SAFETY CONSIDERATIONS 23

c/)

Fracture Region or 

region of unstability

( . I" ~~ Normal stress (o)

°r(% A$ 03-0, o3^

^ 2 <£+v

Oj+Oj

FIGURE 12. -Diagram of Coulomb-Navier fracture criteria showing how rock failure can be affected by an increase in pore

pressure (principal stresses are kept constant).

quakes. Therefore, fluid injection and reservoir seepage 

would simply modify earthquake timing, intensity, and 

location when the rock is already stressed to the verge 

of breaking by tectonic stresses or has the potential to 

slide on a preexisting fault plane or planes.

THE POSSIBILITY OF TRIGGERING EARTHQUAKES BY 

HYDRAULIC FRACTURING AND GROUT INJECTION

The mechanism of disposing radioactive waste by 

grout injection and hydraulic fracturing is different 

from that of disposing by the injection of fluid. The injected grout becomes an integral part of the host rock 

after solidification which occurs within one or two days. 

Owing to the very low permeability (10- 6 D) of the 

selected host rock and the quick solidification of the 

grout, pore pressure in the host rock is unlikely to be increased by injections except locally and for short times. 

Even during the injection stage, when the waste grout is 

in its liquid state, the injected waste grout is confined in 

the induced bedding-plane fractures because of the low 

permeability of the host rock and the high viscosity of 

the grout. In addition, the disposal sites are to be located 

in areas free of potentially active faults and lacking very 

closely spaced fractures and joints. Because the two required and necessary conditions for triggering earthquakes-potentially active faults and an increase of pore 

pressures-are not associated with the waste-groutinjection technique, the possibility of triggering earthquakes by grout injection and hydraulic fracturing does 

not occur.

In an attempt to obtain seismic signals during grout 

injection and hydraulic fracturing at the ORNL, at the 

first two of the four injections in 1972, an array of sixmicroseismometers was installed in an area approximately 450 m in diameter with the injection well in the 

center. During the last two injections, the diameter of 

the seismometer array was increased to 600 m, and a 

downhole seismometer was installed during the fourth 

injection to reduce surface noise and to improve sensitivity. All the four injections were made at a depth of 

254 m. No meaningful seismic signals were obtained 

from any of the four injections (Weeren, 1974). This indicates that seismic signals generated by grout injection 

and hydraulic fracturing, if any, are so small that they 

can not be differentiated from ambient ground noise. 

The inconclusive seismic result is expected because the 

energy required to induce fractures along weakly bedded shale to overcome the tiny cohesive force along the 

shale bedding planes is small (Sun and Mongan, 1974).
24 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

In conclusion, no earthquake should be triggered by 

hydraulic fracturing and grout injection, either during 

or after injection.

ISOLATION TIME REQUIRED FOR INJECTED WASTES

The length of isolation time required for injected 

waste is primarily dependent on the decay periods of radionuclides contained in the disposed waste and can be 

estimated by the following equation (U.S. Bureau of 

Radiological Health, 1970):

Cr =Cr e-°-693n \_/ v^0c , (55)

where C0 is the activity of a particular radionuclide contained in the waste at the disposal time; C is the activity 

remaining after a time interval, t\ n is the number of 

half-lives, n=t/Ti/2 ; Ti/2 , is the half-life of the radionuclide.

If the safe activity of radionuclides is assumed to be 

one millionth (10~ 6 ) of its initial activity, then the required containment time can be calculated as 20 halflives of a particular radionuclide (eq 55). For example, 

for waste containing 99 percent of 90Sr and 137Cs, only 

600 years of isolation is required. For the radionuclides 

having half-lives of only 28 and 30 years, respectively, 

the projection of geologic and hydrologic factors controlling such processes as erosion and leaching for the 

isolation period can probably be estimated with confidence on the basis of geologic and hydrologic 

knowledge and conceptual models. However, if 129 I is 

the major concern among the radionuclides, then even 

its one half-life (ITxlO6 years) is too long for any 

reliable prediction of the isolation time.

CONCLUSION

In a shale formation characterized by directional tensile strength, the pressure needed to induce a vertical 

fracture across horizontally orientated bedding planes is 

much greater than the pressure needed to form beddingplane fractures. Existing joints and (or) high-angle 

natural fractures may be extended by pressure if they 

are intercepted by induced bedding-plane fractures; 

however, vertical extension will cease where these 

natural fractures or joints intercept weak bedding 

planes. It is therefore concluded that horizontal 

bedding-plane fractures can be induced hydraulically in 

a nearly horizontally bedded shale at depths shallower 

than 1,000 m; deeper, the advantage of directional tensile strength may be overcome by the large overburden 

pressure. The injection experience at Oak Ridge, Tenn., 

and West Valley, N.Y., supports the conclusion that induced fractures may migrate up and down as much as 20 

m from the injected altitude over a distance several hundreds of meters from an injection well (see the Appendix).

The orientation of the induced fractures can be indirectly monitored by observing injection pressures during injection time and by measuring the pressure decay 

of water injections and the uplift of the ground surface 

after injections. The orientation, also can be confirmed 

by gamma-ray logs made in observation wells before and 

after each injection if the injected fluid or grout contains 

gamma-ray-emitting radionuclides.

At least one water-injection test and one groutinjection test should be made during a site evaluation. 

Pressure-decay data obtained from a water injection can 

be used, not only to evaluate the orientation of induced 

fractures and the permeability of the injection shale but 

also to determine the effective stress normal to the fracture plane. The vertical stress may or may not be equal 

to the calculated overburden pressure. At Oak Ridge, 

Tenn., the vertical earth stress is about twice that of the 

calculated overburden pressure, as indicated by the 

pressure-decay data for water injections (see the case 

histories for Oak Ridge in the Appendix). A grout injection not only confirms the conclusions made after a 

water injection but also simulates conditions encountered during waste injections.

Intermediate-level radioactive wastes (specific activity <6xl03 fiCilmL, consisting mainly of radionuclides 

having half-lives of less than 50 years, such as strontium 

and cesium) mixed with cement and ion-exchange and 

adsorption materials can be injected into shale by 

hydraulic-fracturing and grout injections. After the 

solidification of the grout, the wastes are immobilized 

and become an integral part of the shale and will remain 

at depth as long as the shale is not subjected to severe 

erosion and dissolution. The injected wastes will thus be 

kept within a known horizon. It can be concluded that 

grout disposal of radioactive wastes by hydraulic fracturing in shale is safe and feasible if the shale formation 

is carefully selected, tested, and evaluated and if the 

grout is properly mixed and the injection is cautiously 

conducted. However, risk analyses comparing with 

other alternatives should be carefully evaluated before 

the grout injection method is selected.

At least four observation wells made with strong tubing and pressure cemented should be constructed at a 

radial distance of 50 m in four directions from the injection well for determining the orientation of induced fractures after injections. Four or more additional observation wells should be constructed at radial distances far 

enough away from the injection well so that they are at a 

distance greater than that expected to be reached by 

any grout sheet. The distance beyond which the grout is 

not expected to extend can be estimated by equation 51. 

If the injected wastes contain gamma-ray-emitting ra-
REFERENCES CITED 25

dionuclides, these observation wells can be used for 

monitoring safety. More observation wells will increase 

confidence that the injected wastes are isolated in a 

known horizon.

Because a waste-disposal site must be in a geologically 

stable area lacking potentially active faults and because 

there is no general and extensive increase in pore 

pressure of the rock mass due to grout injections, there 

is no danger that grout injection would trigger earthquakes during or after the injections.

Waste disposal is conducted by injections in several 

stages through different levels. The first series of injections starts at the greatest depth, then the injection 

zone is plugged off by cement. The next series of injections are started at a suitable distance above the first injection zone. The repeated use of the injection well 

distributes the costs of constructing injection and 

monitoring wells over many injections, thereby making 

hydraulic fracturing and grout injection economically attractive as a method for disposing intermediate-level 

radioactive wastes.

REFERENCES CITED

Anderson, R. E., and Laney, R. L., 1975, The influence of late 

Cenozoic stratigraphy on distribution of impoundment-related 

seismicity at Lake Mead, Nevada-Arizona: U.S. Geological Survey 

Journal of Research, v. 3, no. 3, p. 337-343.

Badgley, P. C., 1965, Structural and tectonic principles: New York, 

Harper & Row, 521 p.

Barenblatt, G. L, 1962, The mathematical theory of equilibrium cracks 

in brittle fracture, in Dryden, H. L., and Von Karman, T., eds., 

Advances in applied mechanics: New York, Academic Press, p. 

55-129.

Bear, Jacob, 1972, Dynamics of fluid in porous media: New York, 

American Elsevier, 764 p.

Belter, W. G., 1972, Deep disposal systems for radioactive wastes, in 

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26 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

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APPENDIXES: CASE HISTORIES 27

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APPENDIXES: CASE HISTORIES

The technique of hydraulic fracturing has been widely 

applied since 1947 in the water flooding of oil fields 

(Howard and Fast, 1970); it was first proposed as a 

means to dispose of radioactive waste in shale by grout 

injection and has been used in experimental studies at

the Oak Ridge National Laboratory from 1959 through 

1965. A total of 10 experimental injections were made at 

three different injection wells. Since 1966 the hydraulicfracturing and grout-injection disposal techniques have 

become operational, 17 injections had been made up to 

1978. A total volume of 6,400 m3 of radioactive waste 

containing 641,300 Ci of radionuclides has been injected 

for disposal.

To further study the feasibility of this disposal method 

at another location and to devise economic and reliable 

methods for determining the orientation of the 

hydraulically induced fractures to insure that the disposed wastes are isolated in a desired horizon, experimental studies were made jointly by the Oak Ridge 

National Laboratory and the U.S. Geological Survey 

from 1969 through 1971 at West Valley, N.Y. Five 

water injections and one grout injection that was tagged 

with gamma-emitting radioisotopes as tracers were 

made into another shale formation. No actual waste was 

disposed during these experimental studies.

Because the methods developed during the West 

Valley studies can be applied to the ORNL disposal site, 

the West Valley case history, which has been fully 

discussed by Sun and Mongan (1974), is presented first.

HYDRAULIC FRACTURING AT 

WEST VALLEY, N.Y.

West Valley is located approximately 56 km southsoutheast of Buffalo, N.Y., and is in the north portion of 

Cattaraugus County with an altitude of about 457 m. 

The hydraulic fracturing study site is located on the 

property of Western New York Nuclear Service Center 

near the town of West Valley (fig. 13). The area is 

drained by Buttermilk Creek, which flows northward 

and enters Cattaraugus Creek, which enters Lake Erie.

The injection depths ranged from 153 m through 442 

m. Injections were made in the injection well in sequence from the bottom upward. For a given test the 

well was plugged by cement to the desired injection 

depth and a horizontal 360° slot was made near the bottom of the unplugged part of the wall (as described in 

detail on p. 59).

SITE GEOLOGY

Because the purpose of the study was to evaluate the 

feasibility of the disposal method and not to select a site, 

the regional geology and hydrology were not investigated 

for the study. Only the site geology that might affect the 

orientation of the hydraulically induced fractures was 

briefly examined.

The test site is underlain by sedimentary rocks of 

Cambrian through Devonian age and is within the Appalachian Plateaus province. The area has been only 

slightly affected by tectonic events. No faults or folds
28 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

78° 37' 30"

Base from U.S.G.S. o 1000 2000 sooo 4000 sooo sooo 7000 FEET 

West Valley and Ashford I ' H h ' H ' r ' 

Hollow Quadrangles ° ° 5 1 1 '5 2KILOMETEflS 

New York 1964 Contour interval 20 feet (6.1 meters)

Datum is mean sea level

FIGURE 13. -Location of the hydraulic-fracturing test site, West Valley, N.Y.

have been mapped at the site. The nearest mapped fault 

is the Clarendon-Linden Fault, approximately 45 km 

east of the site.

The rocks involved in the tests are mostly Devonian 

shales and some interbedded siltstone. The area is 

covered by glacial deposits as much as 60 m thick. The 

rocks involved in the fracturing injections probably 

belong to Devonian shale in the Canadaway Group (New 

York State usage). The shale involved in the first two injections (at 442 m depth) may belong to the older 

Rhinestreet Shale Member of the West Falls Formation

(Sun and Mongan, 1974). A layer of siltstone 30 m thick 

was found in a core hole at a depth of 290-320 m. The 

siltstone contains thin layers of silty shale. The bedding 

planes of the shale were nearly horizontal, probably dipping southward at the regional dip of 1-2°.

Three sets of principal joints have been identified by 

G. H. Chase, of the U.S. Geological Survey, at the outcrop area near the test site. The trends are N. 68° E., N. 

45° W., and N. 13° W. in descending order in frequency 

of occurrence (fig. 14). All joints are vertical or nearly 

so. The average joint spacing is about 60 cm, and the
APPENDIXES: CASE HISTORIES 29

330 30e

315 45'

300

60e

255

105'

240

225

210

20 JOINTS

FIGURE 14. - Diagram showing the observed trend of three principal joint sets, West Valley, N. Y. (written commun., G. H. Chase,

1969).

average wall separation is 3 mm wide and filled with 

sediments. The vertical length of the joints ranges from 

< 30 cm to 2 m. Most of them are 30 cm or less. From 

surface studies and cores and geophysical logs it was 

estimated by Chase that probably 20 percent of the 

joints are open (Sun and Mongan, 1974).

WELL CONSTRUCTION

A core hole was drilled to a depth of 463 m in order to 

obtain lithologic and petrophysical information. The

core hole was then cased with rather weak steel tubing 

and was pressure cemented in place. This well was used 

as one of the four observation wells during the study and 

was named the East-observation well. Before converting the core hole to an observation well, gamma-ray, 

electric, and 3-dimensional sonic, density, and caliper 

logs were made in the hole to obtain information on subsurface geology.

The injection well, which was constructed of good 

quality steel casing and was pressure cemented to a full
30 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

depth of 463 m, was located 46 m from the core hole 

(figs. 15, and 16). Density, caliper, gamma-ray, and holedeviation surveys were made in the injection well before 

the well was cased and was pressure cemented.

Three more observation wells were constructed to the 

south, the west, and the north, each 46 m from the injection well (fig. 16). These observation wells were also 

cased with strong tubing and were pressure cemented to 

a full depth of 463 m. Gamma-ray logs were made in all 

these observation wells before and after each injection 

to determine the orientation of induced fractures.

INJECTIONS

Only three water injections and one grout injection 

are discussed here as examples of the study. Two water 

injections were made through the same slot at a depth of 

442 m; one injection was made without tracer, and the 

other, with radioactive tracers. The grout injection was 

the last injection during the study and was made with a 

radioactive tracer and at a depth of 152 m. Before the 

grout injection a water injection without tracer was 

made at the same depth through the same slot. All injection results indicate that the theory and methods 

discussed in the text are approximately valid and that 

the orientation of induced fractures can be determined 

by direct surveys through observation wells or by 

evidence deduced from injection data. Results of injections made at the same depth and through the same slot 

are nearly duplicated.

WATER INJECTION

The first water injection was made on October 9,1969. 

About 433 m3 of water without tracer was injected 

through a precut slot at a depth of 442 m. The rock at 

this depth is a well-bedded petroliferous shale. A zone of 

vertical joints at a depth of 439-442 m had been determined by G. H. Chase, from a geophysical log.

Pressures discussed that apply to the theory are 

pressures at injection depth, commonly called "bottomhole pressures"; however, pressures observed during 

test injections were surface pressures measured at the 

wellhead of an injection well (fig. 15). Bottom-hole 

pressures used in the interpretation of water injections 

were computed from observed pressures by adding the 

calculated static pressure in the well casing and by subtracting the pressure loss due to friction in injection 

pipe. For water injections, the frictional pressure loss in 

the injection pipe was calculated by the Darcy-Weisbach 

equation (Davis and Sorensen, 1969), which is given as

AP=500/LVr2/D, (56) 

where

AP = pressure loss due to friction, in pascals; 

/= Fanning frictional factor of casing, dimensionless;

L = length of pipe, in meters;

D = inside diameter of pipe, in meters; and

V= flow velocity, in meters per second.

The injection was started at a very low rate that could 

not be detected on a flow meter near the wellhead. At 

this low rate the injection pressure increased rapidly. 

Twenty-two minutes after the injection started, the 

pressure near the wellhead reached 9.65 MPa 

(megapascals) (table 1), and a trace of flow was detected 

on the flow meter. The injection rate was progressively 

increased in two steps, from 0.001 m3/s to 0.002 m3/s 

and then to 0.003 m3/s. Each injection step lasted about 

10 minutes. After the increase to 0.003 m3/s, an injection pattern consisting of flow rates of 0.006 m3/s, 0.013 

m3/s, and 0.025 m3/s, each occuring for an interval of 

one-half hour, was established. This pattern was 

repeated over and over until the end of the injection (fig. 

17).

Six hours from the start, after a total of 223 m3 of 

water had been injected, the injection was stopped to 

allow for instrument adjustment. The injection was 

resumed 45 minutes later using the regular injection 

pattern, but this time starting at the rate of 0.025 m3/s. 

The observed pressures, injection rates, and calculated 

bottom-hole pressures are listed in table 1.

If flow through an induced fracture is assumed to be 

laminar and to obey Darcy's law, then the injection 

pressure at the well should be linearly proportional to 

the injection rate. This assumption has been proved to 

be at least approximately correct by using a polynomial 

regression of the injected data, which showed by F-tests 

that only the linear term of Q (injection rate) has 

significance (Ostle, 1954).

During the stage of fracture initiation, injection 

pressure must be built up to overcome the tensile 

strength of the rock. After the rock is broken, injection 

pressure gradually decreases to the required propagation pressure. During this transitional stage, injection 

pressures are not linearly proportional to the injection 

rates. Excluding these pressures, a linear regression 

equation fit to data collected before the injection pause 

and having a correlation coefficient of 0.88 has been 

found (fig. 18); the result is

P= 11.96 + 24.05 Q, (57)

where P is bottom-hole pressure, in megapascals, and Q 

is the injection rate, in cubic meters per second.

Because the regression coefficient of Q was determined from a small sample size of P and Q taken from 

the true population, it is possible that the values of P and 

Q may be independent in the true population and the 

regression equation has no meaning statistically. 

Therefore, it is essential to test whether the regression
APPENDIXES: CASE HISTORIES 31

Fluid from injection pump

Tracer 

Tank

^Concrete 

block

t

Flowmeter

Pressure 

gauge

r-7 ;. 1 .-. .-.. .' .- ' :

 1 « 

^feoQ7^^^;|i(7:^%p^ 

?S6.0Jm^^^Smfcj ^p^:^^®^p?^m '^^^^ f^B^/Ms^

~-^-^~- r_^S hale -~-~-r~_r-_j

_ _ _ _

_ _ _ _ _

- _ ^^-^

_ _ _ _ _ ^^^^ X i

__ __ __ __ _ _M ^^^*I«J j

;

'

/

/

/

/

/

'

/

/

/

/

/

/

/

/

/

/

/

/

f

/

^

/

,

/

^

^

^

>

<

1

//////

'V dlVC

§g|5i||Glac,al^rim|§g|||

/

^r 9*0 c m H o 1 p

/

/

*« 1 1 /"* m O ^» r» I K^ xv ^^^ j. J. t/ r r 1 w 9 s i n f[ ^

' ~_~_~Lr-_r-.^_-S h a 1 e-~i-~i-"^r^_r^_-

i^=-Cement 

%

^

^K^-^^SGO0 Precut slot . _ _ _ -

?

/

'

FIGURE 15.-Schematic diagram of the injection well, West Valley, N.Y.
32 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

NorthWe 

TABLE

Time 

(min)

2

20 -

99

23 -

25 -

26 -

28 -

31 -

QC

39 -

41

48

49

53

54

cc

56

57

58

59

60

62

64

68

69

70

71

72

73 -

7K

76 -

78 -

80 -

89. .

° East-observation Well 

observation Well (core hole) 

o

True North

O

Injection Well

South-observation Well

0 0

st-observation Well

0 10 20 30 40 50 METERS i , , , , i

FIGURE 16. -Well locations, West Valley, N.Y.

1. -Injection pressure of a water injection at 442 m, Oct. 9, 1969, 

West Valley, N.Y.

[tr., trace]

Observed Calculated R t f Accumulated 

wellhead bottom-hole 'n cti injection 

pressure pressure , 3j -.-IA-J, volume (MPa) (MPa) (m/sxlO ) (lf]3)

0.97 5.3 0 0

6.48 10.81 0 0

9.65 13.98 tr. tr.

7.65 11.91 tr. tr.

7.17 11.50 tr. tr.

7.58 11.91 tr. tr.

7.58 11.91 1.04

7.58 11.91 1.04

7.52 11.91 1.04 0.4

7.72 12.05 1.89

7.65 11.98 1.89

7.69 12.02 1.89

7.65 11.98 1.89

7.58 11.91 1.89

8.45 12.78 1.89

8.96 13.29 1.89 2.7

9.10 13.42 3.15

9.65 13.98 3.15

9.51 13.84 3.15

10.00 14.32 3.15

9.52 13.84 3.15

9.65 13.98 3.15

10.00 14.32 3.15 4.6

10.89 15.19 6.31

9.38 13.67 6.31

8.55 12.84 6.31

8.45 12.74 6.31 5.9

8.34 12.64 6.31

8.21 12.50 6.31

8.17 12.43 6.31 7.5

8.14 12.43 6.31

8.00 12.29 6.31 9.1

7.93 12.22 6.31

7.86 12.16 6.31

TABLE 1

Time 

(min)

00

8C

87

QQ

QQ

98

QQ

101

10°.

1 AB

118

1 OB

143 -

148 - 

150 -

1 1^ 0.

1 CQ

1 CQ

164 -

1 CQ

170 -

173 -

1 8°.

1 8^

1 88

£V/O 

206

91 Q

oOO 

OQB

941

<i4to 

iiOO 

LiOO 

LA i O 

9QQ

ov/o 

O AC

olo 

ooq

QO8

-Injection pressure of a water injection at442m, Oct. 9, 1969, 

West Valley, N. Y. -Continued

Observed 

wellhead 

pressure 

(MPa)

7.83

7 79

7 79

7 79

7.86

7.86

8.41

8.41

8.27

8.14

8.07

8.07

8.03

8.07

8.48

8.41

7 Q 0.

7.79 

7 7Q

7.76

7.76

7 7Q

7 7Q

7 7Q

8.00

8.07

8.07

8.07

S

A^

8.07

a A7

8 A7

8.00

8 AQ

8

AQ

a °./i

8.41

8 CO

8 CO

8 CO

a £.£,

8 CO

7 7Q

7

TC

7

rr/>

7

TC

7

r?f*

7

r-7f*

7

r7/~*

8.07

8

A7

8

1 A

8 (V7

8

IV7

8.10

8

1 n

8 8Q

8 QK

8

QQ

Q 70

Q rr/»

». 7Q

Calculated 

bottom-hole 

pressure 

(MPa)

12.12 

12.09 

12.09 

12.09

12.16 

12.16 

12.61 

12.61 

12.47 

12.33

12.27 

12.27 

12.23 

12.27 

12.33 

12.27

12.22 

12.09 

12.09 

12.05 

12.05

12.09 

12.09 

12.09 

12.20 

12.27

12.27 

12.27 

12.27 

12.27 

12.27 

12.27

12.20 

12.23 

12.23 

12.20 

12.27 

12.47

12.54 

12.54 

12.51 

12.47 

12.09 

12.05 

12.05

12.05 

12.05 

12.05 

12.05 

12.27 

12.27 

12.30

12.27 

12.27 

12.30 

12.30 

12.68 

12.82 

12.75

12.64 

12.61 

12.64 

12.64

Rate of 

injection 

(m3/s x 10'3)

6.31 

6.31 

6.31 

6.31

6.31 

6.31 

12.62 

12.62 

12.62 

12.62

12.62 

12.62 

12.62 

12.62 

25.23 

25.23

6.31 

6.31 

6.31 

6.31 

6.31

6.31 

6.31 

6.31 

12.62 

12.62

12.62 

12.62 

12.62 

12.62 

12.62 

12.62

12.62 

12.62 

12.62 

25.23 

25.23 

25.23

25.23 

25.23 

25.23 

25.23 

6.31 

6.31 

6.31

6.31 

6.31 

6.31 

6.31 

12.62 

12.62 

12.62

12.62 

12.62 

12.62 

12.62 

25.23 

25.23 

25.23

25.23 

25.23 

25.23 

25.23

Accumulated 

injection 

volume (m3)

11.1

2&.2 

24.0-

27.8 

31.8 

35.5 

39.4

55.6 

56.3

57.5 

59.9

62.0 

62.2 

63.9

69.9 

72.2 

73.9 

75.8 

79.6 

83.5

87.3 

90.6

95.5 

107.0

110.0 

125.4

139.1 

140.7

144.3 

148.6 

151.8

160.1

167.9 

171.7

185.8

202.4 

219.1
APPENDIXES: CASE HISTORIES 33

TABLE!

Time

(min)

QQli

QQO

qqq

qq/i

ooO 

QQG

007

338

QQQ

340

341 -

342

Q/1Q

348

353

QCQ

363

368

Q.7Q

376 3792

380 

381

383 

388 

QQQ

QQQ

403

406

408

411

413

418

493

428

d.OQ

/1Q.S

441

443

448

AK.Q.

458

463

468

471

/17Q

476

478

483

A 88

493

498

KA1

CflQ

CflQ

C-IQ

518

523

COQ

531

CQQ

538

K./1Q

KAQ

KKQ

CCO

561

563

568

-Injection pressure of a water injection at 442 m, Oct. 9, 1969, 

West Valley, N.Y. -Continued

Observed 

wellhead 

pressure 

(MPa)

8

nc

8

79

 i ,\J*J

7 Hfi

.55 

7 ^9

7.48

7.46

7.45

7 41

7 Q.S

7 QQ

7 9.^

7 97

7 91

7.16

7.10

7.07

7 09

7.00

11.51

 10.69 

10.20

 9.72 

 9.45

Q Q1

Q Q1

9 91

9 91

9 17

7 96

7

QQ

7.86

n Q.G

7 Sfi

7 Sfi

7

Q£?

8 £9

8

GQ

8

r*(\

8.69

8

(?Q

Q GQ

8.72

10.00

9 79

9

£C

Q C1

9 45

9 Q.S

9.38

9

QQ

7 9Q.

7.93

7 Q 0.

7.86

7.86

7 QQ.

7 QQ

8.83

8.83

8 79

8 7Q

8

00

8

00

8

QQ

10.14

10.07

979

Calculated 

bottom-hole 

pressure 

(MPa)

12.61

12.05 

11.98 

11.91 

11.88 

11.85 

11.81 

11.79 

11.78

11.74 

11.71 

11.71 

11.68 

11.60

11.53 

11.49 

11.43 

11.40 

11.35 

11.33 

15.37

14.54 

14.06 

13.58 

13.30 

13.16 

13.16

13.06 

13.06 

13.02 

12.26 

12.19 

12.16

12.16 

12.16 

12.16 

12.16 

12.82 

12.89 

12.89

12.89 

12.89 

12.89 

12.92 

13.85 

13.64 

13.51 

13.37

13.30 

13.23 

13.23 

13.23 

12.22 

12.22 

12.22

12.16 

12.16 

12.22 

12.22 

13.02 

13.02 

12.99

12.99 

12.99 

12.99 

12.99 

13.99 

13.92 

13.58

Rate of

injection 

(m3/s x 10-J)

25.23 

0 

0 

0 

0 

0 

0 

0 

0

0 

0 

0 

0 

0

0 

0 

0 

0 

0 

0 

25.23

25.23 

25.23 

25.23 

25.23 

25.23 

25.23

25.23 

25.23 

25.23 

6.31 

6.31 

6.31

6.31 

6.31 

6.31 

6.31 

12.62 

12.62 

12.62

12.62 

12.62 

12.62 

12.62 

25.23 

25.23 

25.23 

25.23

25.23 

25.23 

25.23 

25.23 

6.31 

6.31 

6.31

6.31 

6.31 

6.31 

6.31 

12.62 

12.62 

12.62

12.62 

12.62 

12.62 

12.62 

25.23 

25.23 

25.23

Accumulated 

injection 

volume (m3)

223.7

226.2

227.8 

230.8 

238.6 

246.4 

254.4

262.6 

270.6 

274.7

278.8 

280.9

284.6

295.2 

303.2

311.4 

319.2

334.9 

343.2 

351.3

358.8

362.6 

364.4 

366.3

368.7

376.6 

380.7

388.5 

394.1

TABLE I. -Injection pressure of a water injection at 44% m, Oct. 9, 1969, 

West Valley, N. Y. -Continued

Observed Calculated R . ,. Accumulated 

Time wellhead bottom-hole Kate 01 injection 

(min) pressure pressure , "/ ilv3\ volume (MPa) (MPa) (m/sxlO ) (m3)

573 9.72 13.58 25.23 409.5

578 9.65 13.51 25.23 415.7

583 9.58 13.44 25®3 432.7

586 9.52 13.37 25.23 428.4

5883 432.6

Notes: 

Calculated bottom-hole pressure (for injection)

Calculated bottom-hole pressure (for pressure decay) 

= observed wellhead presssure + static pressure in casing.

1 Injection stopped; 45-minute pause. 

2 Injection restarted. 

3 End injection.

coefficient determined from the sample size is significant in a statistical sense. The significance of the regression coefficient of 24.05 of Q in the regression equation 

has been tested statistically by assuming a probability of 

Type I error equal to 5 percent (95-percent level of confidence). The conclusion is that the values of P are 

dependent on the values of Q statistically (Sun and 

Mongan, 1964). 

Because of the simple geologic structure and the 

relatively flat topography at the test site (fig. 13), it is 

reasonable to consider that the vertical earth stress is 

equal to the overburden pressure. The average specific 

gravity of shale and glacial drift at the test site are 2.6 

and 2.0 respectively (deLaguna, 1972). Therefore, the 

overburden pressure at the injection depth can be 

estimated as 

oz = 9.8 xlO-3 (2.0x60 + 2.6 (442 -60)), 

= 10.9 MPa.

When Q was nearly zero, the observed injection 

pressure rose to 14 MPa (fig. 17), which was the 

breakdown pressure. As discussed previously, a horizontal fracture was probably initiated at the well face, owing to the high tensile strength provided by the casing 

and the horizontal slot cut through the casing and into 

the shale. The tensile strength of the shale in the vertical 

direction, Tffz, can be estimated by equation 45, and the

result is 

Taz = 10.9-14, 

= -3.1 MPa.

After 3 m3 of water had been injected, the injection 

pressures increased rapidly beyond the propagation 

pressures predicted by the regression equation (eq 57). 

These high pressures may suggest the formation of additional fractures. 

From equation 57, the normal propagation pressure at 

the rate of 0.006 m3/s is 12.1 MPa; however, the observed highest presure at 0.006 m3 /s was 15.2 MPa (fig. 

17). This pressure could be the breakdown pressure at 

tVip stao-p of formation of additional f raptures. The ten-
34 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

i l I i TT

16

^ 14

sr

13

§ 12

INJECTION RATE, (0), IN CUBIC METERS PER SECOND x 10-3

I I l l

-1 l l i I I I l i I l I i i I I l i i I I l l l I l l l l I l l I l I l l l i I l l l I I I I I I I l I l I I l I I I I I I I 

0 50 100 150 200 250 300 350 400 450 500 550 600 650

INJECTION TIME (t), IN MINUTES

FIGURE 17.-Pressure plotted against time, the water injection at 442 m, Oct. 9, 1969, West Valley, N.Y.

14

o

CO

^ 13

a:

CO 

CO

gj

o 

o

CD

12 P=11.96 + 24.05Q -

11

6 8 10 12 14 16 18 20 22 24 

INJECTION RATE (Q), IN CUBIC METERS PER SECOND x 10-3

26 28 30

FIGURE 18.-Pressure plotted against injection rate, before a 45-rriinute pause, the water injection at 442 m, Oct. 9,1969,

West Valley, N.Y.
APPENDIXES: CASE HISTORIES 35

sile strength of the shale calculated on the basis of this 

breakdown pressure is 4.2 MPa, which is about 1.1 MPa 

higher than the estimated value based on the first 

breakdown pressure.

When the injection is stopped, Q will be zero. The instantaneous shut-in pressure can be calculated from 

equation 57, resulting in 12 MPa. The observed instantaneous shut-in pressure during the 45-minute pause 

was 12.1 MPa (fig. 17), virtually the same as the value 

calculated by equation 57.

The average cohesive force at the fracture tip can be 

estimated by equation 46 if Q is equal to zero, and the 

result is

and

= -1.1 MPa,

/-0.35.

After the 45-minute pause, the injection was resumed 

at a rate of 0.025 m3/s. The calculated propagation 

pressure for this rate should be 12.6 MPa (eq. 57); 

however, the observed pressure was 15.4 MPa, which 

was probably the breakdown pressure at the reinjection 

stage. The tensile strength of the shale estimated on the 

basis of this breakdown pressure is 3.9 MPa, which is 0.8 

MPa higher than the first calculated value (3.1 MPa) but 

is close to the value calculated on the basis of breakdown 

pressure observed at 0.006 m3/s.

After the fracture was reinitiated, the injection 

pressure diminished to the normal propagation 

pressure. The regression equation (fig. 19), which has a 

correlation coefficient of 0.89, for the injection period 

after the pause is

P= 11.96 + 60.01 Q. (58)

Again the regression coefficient has been found to be 

significant at the 95-percent confidence level.

After completion of the injection, the well was shut in 

at the wellhead. The observed instantaneous shut-in 

pressure was 12 MPa, which closely matches the 

estimated shut-in pressure obtained by equations 57 and 

58. Pressure decay was observed for about 8 days; the 

results are shown in table 2 and figure 20.

The observed injection pressure at the end of the first 

part of the injection, before 45-minute pause, at an injection rate of 0.025 m3/s was 12.6 MPa, and the observed 

shut-in pressure was 12.05 MPa (table 1); the difference 

between the two pressures was 0.55 MPa. Therefore, 

the pressure needed to overcome friction loss of one unit 

of injection rate was 22 MPa/(m3/s), which is close to the 

regression coefficient of Q determined statistically -that is, 24 MPa/(m3/s) (eq 57). The observed injection pressure at the end of the injection at an injection rate of 0.025 m3/s was 13.4 MPa, and the observed 

shut-in pressure was 12 MPa (table 1); the difference

TABLE 2. -Pressure decay of a water injection at 442 m, Oct. 9, 1969,

West Valley, N.Y.

Time since end 

of injection (min)

0

1

2

3

4

5

10

15

20

25

30

45

60

75

90

105

120

135

165

195

225

255

285

315

345

375

405

435

465

495

525

555

585

615

645

705

735

765

795

825

885

915

945

1,005

1,185

1,305

1,575

2,205

2,415

2,625

2,985

3,705

3,930

4,295

5,065

5,775

6,585

7,185

7,995

8,745

9,465

10,065

10,905

11,265

Observed wellhead 

pressure (MPa)

7.65

7.58

7.52

7.48

7.46

7.46

7.32

7.25

7.21

7.17

7.15

7.07

6.99

6.94

6.89

6.85

6.82

6.78

6.72

6.67

6.63

6.61

6.59

6.56

6.54

6.49

6.46

6.42

6.39

6.34

6.30

6.27

6.23

6.19

6.16

6.09

6.05

6.01

5.97

5.94

5.87

5.83

5.79

5.73

5.56

5.45

5.29

5.03

4.98

4.93

4.83

4.67

4.62

4.53

4.41

4.27

4.15

4.07

3.96

3.88

3.79

3.73

3.66

3.63

Note: Static ground-water pressure at injection level

Calculated bottomhole pressure, 

P (MPa)

11.98

11.91

11.85

11.81

11.79

11.79

11.65

11.58

11.53

11.50

11.48

11.40

11.32

11.27

11.22

11.18

11.15

11.11

11.05

11.00

10.96

10.93

10.92

10.89

10.87

10.82

10.79

10.75

10.72

10.67

10.63

10.60

10.56

10.52

10.49

10.42

10.38

10.34

10.30

10.27

10.20

10.16

10.12

10.06

9.89

9.78

9.62

9.36

9.31

9.26

9.16

9.00

8.95

8.86

8.74

8.60

8.48

8.40

8.29

8.21

8.12

8.06

7.99

7.96

P0 = 4.09 MPa.

(MPa)

7.89

7.82

7.76

7.72

7.70

7.70

7.56

7.49

7.44

7.41

7.39

7.31

7.23

7.18

7.13

7.09

7.06

7.02

6.96

6.91

6.87

6.84

6.83

6.80

6.78

6.73

6.70

6.66

6.63

6.58

6.54

6.51

6.47

6.43

6.40

6.33

6.29

6.25

6.21

6.18

6.11

6.07

6.03

5.97

5.80

5.69

5.53

5.27

5.22

5.17

5.07

4.91

4.86

4.77

4.65

4.51

4.39

4.31

4.20

4.12

4.03

3.97

3.88

3.87
36 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

15

14

13

12

i i r

o

CO

CO 

CO

11

6 8 10 12 14 16 18 20 22 24 

INJECTION RATE (0), IN CUBIC METERS PER SECOND x 10-3

26 28 30

FIGURE 19.-Pressure plotted against injection rate, after a 45-minute pause, the water injection at 442 m,

Oct. 9, 1969, West Valley, N.Y.

10 1 10 2 103 104 

TIME AFTER END OF INJECTION, (t), IN MINUTES

FIGURE 20.-Pressure decay plotted against time, the water injection at 442 m, Oct. 9, 1969, West Valley, N.Y.

105

between the two pressures is 1.4 MPa. The pressure required to overcome frictional loss of one unit of injection 

rate was 56 MPa/(m3/s), which is close to the regression 

coefficient of 60 MPa/(m3/s) (eq 58). From these correlations, it probably can be concluded that the determined 

regression equations (eqs 57, and 58) are meaningful.

Water level in the core hole was measured by G. H. 

Chase (written commun., 1970) on May 22, 1969, and 

was found to be 18 m below the land surface. Adjusted 

by the difference in altitude between the core hole and 

the injection well, the depth to water was 24 m in the injection well. The hydraulic pressure P0 in the formation 

at the injection depth of 442 m was therefore calculated 

as 4.1 MPa (a meter of water produces 9,800 Pa 

pressure).

The log-log plot of (P-P0) against observation time t 

(fig. 20) appears to fall on two straight lines that intersect at £ = 500 minutes and (P-P0)=6.7 MPa. 

Therefore, the earth stress normal to the fracture plane 

is estimated to be 10.79 MPa (4.09 + 6.7=10.79 MPa), 

which closely correlates to the calculated overburden 

pressure which is 10.9 MPa. It can be concluded that the 

earth stress normal to the fracture planes is equal to 

simply the weight of overburden, and therefore the induced fracture is probably nearly horizontal.

The injection water was not tagged with gamma-rayemitting radioactive isotopes; therefore, no field 

evidence is available to indicate the orientation of the induced fractures.

The second water injection was made on June 26, 

1970, at the same depth and through the same slot 

where the first water injection was made. A total of 425 

m3 of water tagged with radioactive isotope of 

95Zr/95Nb was injected. The injection was started at a
APPENDIXES: CASE HISTORIES 37

very low rate, and injection pressure built up steadily. 

The rock was apparently ruptured at a bottom-hole 

pressure of 16.1 MPa (fig. 21; table 3). After the 

breakdown, the injection rate was increased to 0.002 

m3/s. This rate was maintained for 70 minutes. When 

the injection rate was increased again, the pressure rose 

quickly until it reached a peak of 24.2 MPa; at this time, 

the injection rate was 0.01 m3/s. This second peak may 

indicate the formation of additional fractures. 

Thereafter, the pressure dropped to a normal propagation pressure (fig. 21). The regression equation of P and 

Q, having a correlation coefficient of 0.73, is (fig. 22)

P=13.95 + 224.06Q. (59)

Instantaneous shut-in pressure determined from the 

regression equation is 14 MPa; however, the observed 

value was 13.3 MPa (fig. 21). The pressure drop within 1 

minute was 1.2MPa; thereafter the pressure decay was 

very slow (table 4). Therefore, the correct instantaneous 

shut-in presssure is probably around 12 MPa, which is 

the same as that obtained from the first injection test 

(table 2).

The injection well was shut in under pressure on Oct. 

9, 1969, after the first injection was stopped. Two weeks 

before the second injection, the injection well was bled 

and was shut in again on June 25, 1970, one day before 

the injection. A residual pressure of 1.1 MPa was noted 

at the well head (G. H. Chase, written commu., 1970). 

Therefore, there was at least 5.4 MPa (1.1 

x!06 + 442x9800 = 5.4 MPa) pressure remaining in the 

fractures, though it probably was higher than this value. 

The high regression coefficient of Q likely is the result of 

this residual pressure in the fractures.

If the shale is assumed to be ruptured at 16.1 MPa (fig. 

21; table 3), then the tensile strength of the shale in the 

direction normal to bedding planes at the injection depth 

can be estimated by equation 45. The result is given by

= -3.9 MPa,

which is close to the tensile strengths calculated from 

the first water injection on Oct. 9, 1969, at the same injection depth; the tensile strengths fall in the range of 

3.1 to 4.2 MPa.

32 -

30 -_o

28

26 -

I I I I I I 1 I | I I I I I I I I I | I 1 I I M II | I I 

INJECTION RATE (Q), IN CUBIC METERS PER SECOND X 10

200 250 300 350 400 

INJECTION TIME, (t), IN MINUTES

450 500 550 600

FIGURE 21.-Pressure plotted against time, the water injection at 442 m, June 26, 1970, West Valley, N.Y.
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BOTTOM-HOLE PRESSURE (P), I

6 81

RATE (Q

CUBIC

2024 

R SECOND x

2
APPENDIXES: CASE HISTORIES 39

TABLE 4. -Pressure decay of a water injection at 442 m, June 26, 1970,

West Valley, N.Y.

Time since end 

of injection (min)

1

2

3

4

5

6

7

8

9

10

12

13

14

15

18

20

24

29

34

39

44

49

54

64

79

94

109

124

139

169

199

229

259

299

319

349

379

439

469

499

529

559

589

619

649

679

709

739

799

859

987

1,024

1,039

1,219

1,399

1,639

2,269

2,359

2,419

2,479

2,584

2,629

2,689

2,749

2,809

2,839

Observed wellhead 

pressure (MPa)

8.96

7.79

7.65

7.58

7.52

7.45

7.45

7.38

7.38

7.34

7.31

7.31

7.27

7.24

7.17

7.17

7.12

7.10

7.03

7.00

7.00

6.95

6.93

6.89

6.86

6.83

6.79

6.76

6.72

6.69

6.62

6.58

6.55

6.48

6.48

6.45

6.41

6.38

6.34

6.31

6.27

6.24

6.21

6.21

6.17

6.17

6.17

6.17

6.14

6.10

6.03

6.00

6.00

5.93

5.86

5.72

5.47

5.45

5.43

5.40

5.38

5.38

5.34

5.32

5.31

5.31

Calculated 

bottom-hole 

pressure, P (MPa)

13.29

12.12

11.98

11.91

11.85

11.78

11.78

11.71

11.71

11.67

11.64

11.64

11.60

11.57

11.50

11.50

11.45

11.43

11.36

11.33

11.33

11.28

11.26

11.22

11.19

11.16

11.12

11.09

11.05

11.02

10.95

10.91

10.88

10.81

10.81

10.78

10.74

10.71

10.67

10.64

10.60

10.57

10.54

10.54

10.50

10.50

10.50

10.50

10.47

10.43

10.36

10.33

10.33

10.26

10.19

10.05

9.80

9.78

9.76

9.73

9.71

9.71

9.67

9.65

9.64

9.64

(MPa)

9.20

8.03

7.89

7.82

7.76

7.69

7.69

7.62

7.62

7.58

7.55

7.55

7.51

7.48

7.41

7.41

7.36

7.34

7.27

7.24

7.24

7.19

7.17

7.13

7.10

7.07

7.03

7.00

6.96

6.93

6.86

6.82

6.79

6.72

6.72

6.69

6.65

6.62

6.58

6.55

6.51

6.48

6.45

6.45

6.41

6.41

6.41

6.41

6.38

6.34

6.27

6.24

6.24

6.17

6.10

5.96

5.71

5.68

5.67

5.64

5.62

5.62

5.58

5.56

5.55

5.55

TABLE 4. -Pressure decay of a water injection at 442 m, June 26,1970, 

West Valley, N.Y. -Continued

Time since end Observed wellhead 

of injection (min) pressure (MPa)

3,079

3,509

3,769

3,979

4,234

4,489

5,164

5,389

5,899

6,619

6,799

7,339

7,999

8,359

8,839

9,469

10,219

10,969

11,134

11,629

12,439

13,039

13,729

14,269 _______

14,509

15,589

16,819

18,274

5.24

5.09

5.03

4.98

4.92

4.87

4.76

4.74

4.70

4.60

4.60

4.54

4.48

4.45

4.40

4.35

4.30

4.27

4.23

4.19

4.14

4.10

4.03

4.03

4.02

3.99

3.90

3.82

Calculated 

bottom-hole 

pressure, P (MPa)

9.57

9.42

9.36

9.31

9.25

9.20

9.09

9.07

9.03

8.93

8.93

8.87

8.81

8.78

8.73

8.68

8.63

8.60

8.56

8.52

8.47

8.43

8.36

8.36

8.35

8.32

8.23

8.15

P-Po 

(MPa)

5.48

5.33

5.27

5.22

5.16

5.11

5.00

4.98

4.94

4.84

4.84

4.78

4.72

4.69

4.64

4.59

4.54

4.51

4.47

4.43

4.38

4.34

4.27

4.27

4.26

4.23

4.23

4.06

Note: Static ground-water pressure at injection level, P0 = 4.09 MPa.

straight lines. (P-P0) at the point of intersection of the 

two lines is 6.4 MPa; therefore, the estimated earth 

stress normal to the fracture plane is 10.5 MPa (6.4 + 

4.09= 10.49 MPa), which is close to the estimated overburden pressure, 10.9 MPa. Therefore, it can be concluded that the induced fractures are probably nearly 

horizontal.

Ten days after the end of the water injection, July 6, 

1970, gamma-ray logs were made in all four observation 

wells. The East-observation well was found to be 

plugged at 424 m by cement, and the South-observation 

well was also blocked at 442 m. No significant radioactivity above the background level was recorded in either 

of the two wells. Strong gamma-ray activity however, 

was recorded in the North-observation well (fig. 24). The 

radioactivity was observed over a vertical distance of 6 

m (436-442 m), indicating that at least three layers of 

bedding-plane fractures were induced. Strong gammaray activity was also recorded in the West-observation 

well (fig. 24) and observed over a vertical distance of 2 m 

(442-444 m), showing that only one layer of beddingplane fracture was induced.

On Aug. 24, 1970, two months after the water injection and after the South-observation well had been 

cleaned out by a rig, gamma-ray logs were run again in 

the three observation wells. No efforts were made to
40 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

102 n i i i i i i i

t6.70MPa P0 =4.09MPa -

100 10 2 103 

TIME AFTER END OF INJECTION (t), IN MINUTES

104 105

FIGURE 23.-Pressure decay plotted against time, the water injection at 442 m, June 26, 1970, West Valley, N.Y.

API GAMMA-RAY UNIT

0 1000 3000 4000 0 1000 2000 5000 6000

1350

uo

*\\L420-

430- M f\ S\

-

_

440-

450-

-

<

!

 ;

^

r

\

/

 .

/

1

I

- j

1

Log of

Log of 

7-28-71 1400

1450

WEST-OBSERVATION WELL

1500

NORTH-OBSERVATION WELL

FIGURE 24. -Gamma-ray activities observed in observation wells along the casing axis, July 6,1970, after the water injection at 442 

m; depths to gamma-ray activity have been adjusted to the measuring point at the injection well, in accord with the altitude 

difference between the wells, West Valley, N.Y.
430"-

APPENDIXES: CASE HISTORIES

API GAMMA-RAY UNITS 

0 4008001200160020002400 0 400 80012001600 0 400 800 120016002000

41

440

Q_

LU

o

450

Log of 

8-24-70 _

Log of - 

7-28-71

FT T

Log of -1420

8-24-70 _

Log of --1430 

7-28-71

H440

1410

NORTH-OBSERVATION WELL WEST-OBSERVATION WELL SOUTH-OBSERVATION WELL

FIGURE 25. - Gamma-ray activities observed in observation wells along the casing axis, Aug. 24,1970, after water injection at 442 

m; depths to gamma-ray activity have been adjusted to the measuring point at the injection well in accord with altitude difference between the wells, West Valley, N.Y.

clean out the cement in the East-observation well 

because of the small-diameter well tubing. Strong 

gamma-ray activity was recorded in the Southobservation well at this time, and a vertical spread of 

less than 4 m (443-447 m) was observed (fig. 25), and 

two layers of bedding-plane fractures were induced. The 

gamma-ray activity observed at the other two observation wells, North- and West-observation wells, was approximately at the same depth as recorded before; 

however, the intensity was reduced to less than half of 

the values recorded on July 6, 1970, because of radioactive decay (figs. 24, and 25).

GROUT INJECTION

Only one grout injection was made at a depth of 152 m 

at the West Valley site during the study. Before the 

grout injection, a total of 195 m3 of water without a 

radioactive tracer was injected. The observed injection 

pressures associated with injection rates are shown in 

table 5 and figure 26. The regression equation of P and 

Q having a correlation coefficient of 0.91, was found (fig. 

27) and is given by

P=3.88 + 10.93Q. (60)

Observed shut-in pressure was 3.8 MPa (table 6), 

which is close to the value indicated by the regression 

equation. Pumping rate was kept at 0.002 m3/s during 

the first hour of the injection. It was then increased to 

0.028 m3/s over a 1V2 hour interval. The rock was ruptured at 4.3 MPa (fig. 26.)

The overburden pressure estimated from the density 

of rock at a depth of 152 m is 3.5 MPa. The difference 

between the overburden pressure and the rupture 

pressure is the value of the tensile strength of shale normal to the fracture plane. If nearly horizontal beddingplane fractures are assumed to be induced, then the tensile strength of shale normal to bedding planes at the injection depth was 0.8 MPa, which is one-fourth of the 

value determined from the data for water injections 

made at 442 m. By inspecting cores, the shale at 152 m 

depth was found to have been more easily ruptured 

along bedding planes than was the shale at 442 m depth.

Average cohesive force at fracture tip is calculated as

and

/7>3.5-3.9, 

= -0.4 MPa,

/=0.50.

The pore pressure at 152 m depth was found to be 1.3 

MPa. The differences between the observed pressure 

decay P and pore pressure P0 over time t are plotted on 

a log-log graph paper in figure 28. All data appear to fall 

on two straight lines. The two lines intersect at £=37 

minutes and P-P0 = 2.1 MPa. Therefore, the earth 

stress normal to the fracture plane is 3.4 MPa 

(2.1 + 1.25 = 3.35 MPa), which is nearly equal to the 

calculated overburden pressure. Therefore, it can be 

concluded that the induced fractures are probably 

horizontal. No radioactive isotopes were added to the injection water; therefore, no field evidence is available to 

support this conclusion.
42 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

TABLE 5. -Injection pressure of a water injection at 152 

1971, West Valley, N.Y.

Observed Calculated TJ , f 

Time wellhead bottom-hole -. [ 

(min) pressure pressure ^7^10-'^ (MPa) (MPa) (m/sxlO )

0

9 net A 9K c\

°, 9 fiQ 4 1 Q fiQ

5

O CO A 1 O O Aft

10 2.52 4.01 1.96

15 2.45 3.94 1.96

20 2.41 3.91 1.96

OK O QQ Q QQ O A9

on o QQ o. QQ 9 n9

QK O QQ O. QQ 9 n9

40 ____ 2.38 3.88 2.02

4K O QQ O QQ O n9

50 2.38 3.88 2.02

KK 9 QQ O QQ O n9

60 ____ 2.38 3.88 2.08 65 2.45 3.94 3.09

70 2.45 3.94 3.47

75 2.48 3.96 3.85

Sft 9 48 Q Qft A 7Q

OK O >*O O ftC K 1 ^7

on o />Q o Qft ft 1 Q

95 2.48 3.96 7.44

i nn 9 /to o Qft n oc

105 2.52 3.99 8.71

1 1 fi 9 £.9 Q QQ Q Q4

115 2.52 3.99 10.41

121 2.55 4.01 11.23

125 2.55 4.01 11.99

130 2.59 4.04 13.12

135 2.92 4.34 17.54

140 2.92 4.24 25.74

i/lK 9 Q9 49^ 9ft Q7

150 2.92 4.25 26.50

155 2.92 4.25 26.87

1 fiO 9 Q9 49^ 97 00

165 2.90 4.22 27.63

170 2.85 4.17 27.63

175 2.83 4.14 27.88

1 8^ 9 8Q A 1 A 98 Q9

190 2.85 4.16 28.14

195 2.85 4.16 28.51

200 2.85 4.16 28.51

205 2.85 4.16 28.64

210 2.85 4.16 28.39

215 2.85 4.16 28.89

220 2.84 4.15 28.51

2251 2.84 4.15 28.51

m, May 29,

Accumulated 

injection 

volume (m3)

0 

.4 

.8 

1.4 

2.0

2.6 

3.2 

3.8 

4.4 

5.0 

5.6

6.2 

6.8 

7.4 

8.4

9.4 

10.6 

12.0 

13.6 

15.4 

17.6

19.8 

22.4 

25.2 

28.4 

32.4 

35.3

39.2 

44.5 

52.2 

60.1 

68.1 

76.1

84.2 

92.5 

100.8 

109.2 

126.2 

134.6 

143.2

151.7 

160.3 

168.8 

177.5 

186.0 

195.0

JEnd of injection.

TABLE 6. -Pressure decay of a water injection at 152 m, May. 29, 1971, 

West Valley, N.Y.

Time since end Observed wellhead Calculated bottomof injection (min) pressure (MPa) P^MPa) 1*'

0 2.30 3.80

1 2.25 3.74

2 2.21 3.71

3 2.19 3.68

4 2.17 3.66

5 2.15 3.65

6 2.14 3.63

7 2.12 3.62

8 2.11 3.61

9 2.10 3.59

P-Po 

(MPa)

2.55 

2.49 

2.46 

2.43 

2.41 

2.40 

2.38 

2.37 

2.36 

2.34

TABLE 6. -Pressure decay of a water injection at 152 m, May 29, 1971, 

West Valley, N.Y. -Continued

Time since end Observed wellhead Ctotetresbsure°m" p-P° 

of injection (min) pressure (MPa) f>?MPa) (MPa)

10 2.09 3.58 2.33

15 2.03 3.53 2.28

20 1.98 3.47 2.22

25 1.93 3.42 2.17

30 1.89 3.38 2.13

35 1.84 3.34 2.09

40 1.81 3.31 2.06

45 1.77 3.26 2.01

50 1.73 3.23 1.98

55 1.70 3.20 1.95

60 1.67 3.16 1.91

65 1.63 3.13 1.88

70 1.60 3.09 1.84

75 1.57 3.06 1.81

80 1.54 3.04 1.79

85 1.51 3.01 1.76

90 1.49 2.99 1.74

100 1.45 2.94 1.69

110 1.40 2.90 1.65

120 1.37 2.86 1.61

130 1.33 2.83 1.58

140 1.31 2.80 1.55

155 1.26 2.76 1.51

170 _________ 1.23 2.73 1.48 

185 1.20 2.70 1.45

200 1.17 2.67 1.42

215 1.15 2.65 1.40

230 1.13 2.63 1.38

245 1.11 2.60 1.35

260 1.09 2.59 1.34

275 1.07 2.56 1.31

290 1.05 2.55 1.30

320 1.03 2.52 1.27

350 1.01 2.50 1.25

380 .99 2.48 1.23

410 .97 2.46 1.21

440 .94 2.44 1.19

470 .93 2.43 1.18

500 .91 2.41 1.16

530 .90 2.39 1.14

560 .88 2.38 1.13

590 .88 2.37 1.12

620 .87 2.36 1.11

650 .86 2.36 1.11

680 .85 2.34 1.09

710 .84 2.34 1.09

740 .83 2.33 1.08

770 _________ .83 2.32 1.07 

800 .82 2.31 1.06

830 _________ .81 2.31 1.06 

860 .80 2.30 1.05

890 .80 2.30 1.05

920 .79 2.29 1.04

950 .79 2.28 1.03

980 .78 2.28 1.03

1,010 .77 2.27 1.02

1,040 .77 2.26 1.01

Note: Static ground-water pressure at injection level, F0 = 1-25 MPa.

On July 23, 1971, a total of 155 m3 of water and grout 

tagged with gamma-ray-emitting isotope of 95Zr/95Nb 

was injected at the same depth, 152 m, through the same 

slot where the water injection was made on May 29, 

1971.
APPENDIXES: CASE HISTORIES 43

5.0

4.5

4.0 -

3.5 -

I I I I | I I I I | I I I I 

. INJECTION RATE (Q), IN CUBIC 

METERS PER SECOND x 10-3

M I I | I I I I

«-^J , (T.

I I

4.34

'1 4.25

I I I I I I I I I

50 100 150 200

INJECTION TIME (t), IN MINUTES

250 300

FIGURE 26.-Pressure plotted against time, the water injection at 152 

m, May 29, 1971, West Valley, N.Y.

The injection was started with 9 m3 of water, after 

which cement and bentonite were added. The volume of 

injected grout was 146 m3 (table 7).

Because grout has high viscosity, the friction loss in 

casing was calculated by using a non-Newtonian flow 

equation (Slagle, 1962; Melton and Saunders, 1957), 

which is expressed as

-' P )/[#'(800/Dn, (61) 

LP V*f

= 2.0xlO- (62) 4

D

where

and

/= 16/Re , for laminar flow when Re < 2,100; 

/= 0.0045 + 0.645(Re )-°- 7 for turbulent flow;

Re = Reynold's number, dimensionless; 

AP = fractional loss (or pressure drop), in megapascals;

p = fluid density, in kilograms per cubic meters; 

V = average or bulk velocity of fluid, in meters per

second;

D = inside diameter of tubing or casing, in centimeters;

/= Fanning friction factor, dimensionless; 

K' = fluid consistency index (or characteristic of

fluid), in N secTC 7m2 ; 

n' = fluid flow behavior index, dimensionless.

The values of K' and n' of the injected grout (July 23, 

1971) were 32.52 and 0.09, respectively (K. A. Slagle, 

written commun., 1971). The calculated bottom-hole

TABLE 7. -Injection pressure of a grout injection at 152 m, July 23, 

1971, West Valley, N.Y.

[tr., trace]

Time 

(min)

O 1

3

4

5

10

15

22

25302

45

50

55

60

65

70

75803

854

90

95

100

105

110

115

120 _____

125

130 _____ 

135

140

145

150

155

160

165

170

175

180

185

190

195

201

205

210

215 ______ 

220

225 _____ 

230

235

245

260

265 2755

280 2906

Observed 

wellhead 

pressure 

(MPa)

0.28

2.07 

2.38 

2.45 

2.21 

2.52 

2.59

2.55 

2.52 

2.48 

2.55 

2.55 

2.55 

2.55 

2.55

2.55 

2.55

2.17 

2.17 

2.38

2.28 

2.21 

2.21 

2.31 

2.14

2.21 

2.28 

2.55 

2.55 

2.62

2.55 

2.41 

2.21 

2.34

2.28

2.28 

2.28 

2.38 

2.41 

2.41

2.34 

2.34 

2.34

2.28 

2.14

2.21 

2.21 

2.14 

2.10 

2.14 

2.14 

2.07 

2.07 

2.07

Calculated 

bottom-hole 

pressure 

(MPa)

1.77

3.56 

3.87 

3.94 

3.70 

4.01 

4.08

4.05 

4.01 

3.97 

4.04 

4.04 

4.04 

4.04 

4.04

4.04 

4.04 

4.05 

4.05 

4.25

4.16 

4.07 

4.07 

4.17 

4.00

4.07 

4.14 

4.41 

4.41 

4.47

4.41 

4.27 

4.05 

4.19 

4.12

4.12 

4.12 

4.21 

4.25 

4.25

4.18 

4.18 

4.18 

4.11 

3.98

4.04 

4.04 

3.97 

3.94 

3.97 

3.97 

3.90 

3.90 

3.90

Rate of 

injection 

(mVsxlO-3)

0.32 

.32 

.32 

.63 

.32 

.95 

.95

1.14 

1.14 

2.93 

2.12 

2.73 

2.78 

2.78 

2.84

3.41 

3.41 

2.90 

2.52

2.84

2.46 

4.54 

3.66 

5.36 

4.98

6.43 

5.80 

8.20 

8.96 

9.08

8.77 

9.59 

9.78 

10.72 

11.54

13.69 

12.36 

14.64 

14.89 

15.90

14.95 

17.22 

15.90 

16.02 

15.01

15.65 

15.52 

15.65 

15.96 

15.65 

15.52 

16.60 

15.90 

15.27

Accumulated 

injection 

volume (m3)

0.1

.3 

.6 

3.3 

3.9

4.7 

5.5 

6.4 

7.2

8.3 

8.9 

9.8 

10.5 

11.4

12.1 

13.5 

14.6 

16.2

17.7

19.6 

21.3 

23.8 

26.5 

29.2

31.9

34.7 

37.7 

40.9 

44.3

48.4 

52.2 

56.5 

61.0 

65.8

71.2 

75.3 

80.1 

84.9 

89.4

94.1 

98.7 

103.4 

113.0 

127.0 

131.7 

141.3 

146.0 

155.2

1 Water injection.

2 Start isotope injection.

3 Start cement and bentonite.

4 Grout density (average) =1.44 g/cm3 . 

6 End isotope injection. 

6 End injection.

pressure and the observed wellhead pressure, and the 

injection rates and times are shown in table 7 and figure 

29.

The regression equation of P and Q, having a correlation of 0.65 was found (fig. 30) and is expressed as

P=4.0 + 13.12Q. (63)
44 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

53 

< 

o

CO

<

0-

<

C3

4.5

o 

o

DO

4.0

3.5

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

INJECTION RATE (Q), IN CUBIC METERS PER SECOND X 10- 3 

FIGURE 27. -Pressures plotted against injection rate, the water injection at 152 m, May 29, 1971, West Valley, N.Y.

O2 -i i i i i i i i i i i | i i i i i i i i | i i i i I i i i | r

P0 = 1.25 MPa

2,10 MPa

I I I L_L

10° 10 2 103 10*

TIME AFTER END OF INJECTION (f), IN MINUTES

FIGURE 28.-Pressure decay plotted against time, the water injection at 152 m, May 29, 1971, West Valley, N.Y.

No breakdown pressure was observed. However, 

several high pressures indicating the formation of new 

fractures were noted during the injection. The tensile 

strength of the rock at the injection depth probably 

could be estimated from these high pressures. The injection pressure at 0.003 m3/s was 4.3 MPa, from which the 

tensile strength of the shale normal to the fracture plane 

at the injection depth of 152 m was estimated as

Ta =3.5 + 13.12x0.0003-4.3, 

"=-0.8 MPa.

The tensile strength of the shale estimated from other 

high pressures is also near 0.8 MPa. The value of the

tensile strength estimated from this grout injection is 

similar to that estimated from the previous water injection at the same depth.

Gamma-ray logs were made on July 28,1971, five days 

after the injection, in three observation wells. The 

results are shown in figure 31. No gamma-ray survey 

was made in the East-observation well because its casing was ruptured during the injection. The well was 

plugged by grout at a depth of 151 m.

Gamma-ray logs obtained from the other three observation wells together with the evidence of plugging of 

the East-observation well strongly suggest that 

bedding-plane fractures were induced, at least within a 

distance of 46 m from the injection well.
APPENDIXES: CASE HISTORIES 45

5.0 -

4.5 -

4.0

3.5 -

I I I I | I II I I I I I | I I I I I I I I | I I I 

INJECTION RATE (Q), IN CUBIC METERS PER SECOND x 10-3

4.47

50 100 150 200 

INJECTION TIME (t), IN MINUTES

250 300

FIGURE 29. -Pressure plotted against time, the grout injection at 152 m, 

July 23, 1971, West Valley, N.Y.

Precise levels were surveyed by the U.S. Geological 

Survey before and after the grout injection. To insure 

that the level rods would be held on the highest point at 

all times, all bench-mark tablets were straightened and 

leveled by a hand level before the precise levelings were 

made. The leveling results are shown in table 8 and 

figure 32.

The correlation between the observed uplift and the 

uplift calculated by equation 47 is shown in figure 33. 

The calculated radius of the induced fracture is 110 m, 

and the calculated maximum separation of the fracture 

during injection time is 6.5 mm.

SUMMARY

Table 9 summarizes the results of all six injections 

made at West Valley, N.Y. (Sun and Mongan, 1974). 

Results from injections made at the same depth at different times are consistent. No actual data on tensile 

strength of the shale are available; therefore, there is no 

way to check whether the calculated tensile strengths 

are approximately right.

Bedding-plane fractures had been induced, as indicated by gamma-ray logs, within 10 m of the injection 

depth. Orientation of the induced fractures can be determined indirectly by monitoring injection pressure during injection time and by measuring the pressure decay 

of water injections and the uplift of ground surface. Constructing observation wells with strong tubing and good

cement helps prevent damage to the well by induced 

fractures, and the size of observation well needs to be 

large enough to accommodate drilling tools if the well 

needs to be serviced after completion. The unsuitability 

of the East-observation well during the study indicates 

the importance of proper well construction.

RADIOACTIVE WASTE DISPOSAL AT THE 

OAK RIDGE NATIONAL LABORATORY, TENN.

The Oak Ridge National Laboratory waste disposal 

site is located in Melton Valley, Oak Ridge, Tenn. (fig. 

34), within the reservation of the U.S. Department of 

Energy (DOE). The reservation is in the Tennessee section of the Appalachian Valley and Ridge province and 

occupies parts of Anderson and Roane Counties. The 

reservation is bounded on the northeast, southeast, and 

southwest by the Clinch River. The area is approximately 22 km long, 10 km wide, and comprises about 220 

km2 .

The first grout injection was made in 1959 at a shallow 

depth of 90 m. A total volume of 102 m3 of grout composed of water, cement, and bentonite tagged with 137Cs 

was injected. Twenty-two core holes were drilled, data 

from which indicated that bedding-plane fractures had 

been induced. In 1960, a second experimental well was 

constructed roughly 1.83 km east of the first injection 

site. Two injections were made through this well at 

depths of 212 m and 285 m, respectively. A total volume 

of 345 m3 of grout containing 137Cs was injected at a 

depth of 285 m. After this injection, the injection well 

was plugged with cement to a depth of 213 m. A new 

horizontal slot was cut through the casing and cement 

wall at a depth of 212 m. A total volume of 502 m3 grout 

also tagged with 137Cs was injected again into this well. 

Twenty-four core holes were drilled to determine the 

positions of the two grout sheets. Both grout sheets 

were found to be conformable to bedding planes. A third 

well was drilled to a depth of 329 m, 0.8 km west of the 

second experimental site (fig. 34), thereafter named as 

the present fracturing site. (In 1981 this well is still being used for waste injections.) From 1964 through 1965, 

eight experimental injections of actual radioactive 

wastes produced at the ORNL were injected through 

this well. The results strongly indicated that the disposal 

of wastes in shale by grout injection is safe and 

economical. Operational injections then began in 1966. 

The disposal site will reach full capacity between 1985 

and 1988. A new disposal site was selected at a distance 

of 245 m south of the present injection well (fig. 34), and 

a site evaluation study was conducted. The results indicate that the proposed site is acceptable. The following 

discussions summarize the experimental and operational 

injections and the site evaluation.
46 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

w 4.5

4.0

3.5

6 8 10 12 14 16 18 20 

INJECTION RATE (Q), IN CUBIC METERS PER SECOND x 10'3

22 24

FIGURE 30. -Pressure plotted against injection rate, the grout injection at 152 m, July 23,1971, West

Valley, N.Y.

0 400

API GAMMA-RAY UNITS 

800 1200 1600 0 400 800 1200 0 400 800 1200

CO

cc

148

150

152

154

156

158

160

Log of

7-28-71

Log of

8-24-70

^ Log of - 

< 7-28-71 _

\ Log of

' 8-24-70

_ i

-

* I I

S. Log of - 

I 7-28-71_

'-. Log of _ 

 I 8-24-70

-p>

 \

J I I

^ou 

-490

-500

-510

-520

con

LLJ 

Q

SOUTH-OBSERVATION 

WELL

WEST-OBSERVATION 

WELL

NORTH-OBSERVATION 

WELL

FIGURE 31.-Gamma-ray activities observed in observation wells along the casing axis, July 28, 1971, after the grout 

injection at 152 m; depths to gamma-ray activity have been adjusted to the measuring point at the injection well in accord with altitude difference between wells, West Valley, N.Y.

GEOLOGY AND HYDROLOGY

The Appalachian Valley and Ridge province in the Oak 

Ridge area is about 80 km wide and is marked by a series 

of major subparallel thrust faults that trend northeast 

and dip southeast. In each of the faults, layers of rock 

units roughly 3 km thick have moved as much as several 

tens of kilometers to the northwest. Older formations 

have been thrust over younger formations. Deformation 

of the rock strata of the Oak Ridge area resulted from 

compressional forces orginating during the Appalachian 

revolution at the end of Paleozoic time. The strata 

reacted to the pressure by faulting and folding (Eardley, 

1951; McMaster, 1963; deLaguna and others, 1968). At

least 3,000 m of rock has been eroded since the thrust 

faults were formed (deLaguna and others, 1968).

The thrust fault of immediate interest to the waste 

disposal at the ORNL is the Cooper Creek Fault, which 

affects four formations at the site (fig. 35). They are the 

Rome Formation (interbedded sandstone, siltstone, 

shale, and locally, dolomite) of Early Cambrian age, the 

Conasauga Group (calcareous shale interbedded with 

limestone and siltstone) of Middle and Late Cambrian 

age, the Knox Group (dolomite) of Late Cambrian and 

Early Ordovician age, and the Chickamauga Limestone 

of Middle and Late Ordovician age. Two thin-bedded red 

calcareous shales, each 60 m thick, were found in the
APPENDIXES: CASE HISTORIES 

J

47

TRUE NORTH

G *

EXPLANATION

 Injection well

* Survey benchmark

 1- 5 Line of equal uplift, in millimeters. 

Dashed where approximately 

located.

FIGURE 32.-Uplift produced by the grout injection at 152 m, West Valley, N.Y.

Chickamauga Limestone at the ORNL during the drilling of a test well (fig. 35).

The formation exposed at the ORNL waste-injection 

site is the Conasauga Group; all formations above the 

group have been eroded. The thickness of the Conasauga Group is 400 m at the injection site. The injection 

rock is the bottom 90 m of the Conasauga, the Pumpkin 

Valley, which is a dense argillaceous shale that is very 

thin bedded and dominantly red. The Pumpkin Valley is 

overlain by the Rutledge, 300 m thick, composed of gray 

calcareous shale interbedded with generally thin beds or 

lenses of limestone. The contact between the Pumpkin

Valley and the Rutledge is marked by three layers of 

limestone.

The formations all dip to the southeast. Near the outcrop area, the Rome formation dips 45°; however, away 

from the outcrop, dips flatten out to 10°-20°. The beds 

within the fault sheets are, in general, relatively little 

deformed. The Pumpkin Valley is generally undeformed, but locally it is marked by drag folds varying in 

amplitude from a few centimeters to as large as a couple 

of meters. The measured geothermal gradient is 1.34° C 

per 100 m; the average air temperature is 14.5° C, as 

shown in figures 36 and 37 (deLaguna and others, 1968;
48 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

U.S. Energy Research and Development Administration, 1977).

The permeability of the Conasauga Group determined 

from core samples in the laboratory ranges from 10~7 to 

10~8 D; even with fractures present in the core, the 

permeability determined is 10~5 D. Mineralogical examination of the Pumpkin Valley core indicates that clay 

minerals, kaolinite, illite, and chlorite make up the bulk 

of the samples. Quartz is present in moderate quantities, 

but calcite is conspicuous by its absence. The abundance 

of clay minerals indicates that the shale selected for injection has sufficient ion-exchange and adsorption 

capacity (deLaguna and others, 1968).

Records of 11 stations in and around the ORNL indicate that the annual precipitation is 130 cm for the 

water years 1936 through 1960. Maximum monthly 

runoff is likely to be in December through March, when 

rainfall is normally high and soil moisture and groundwater storage are at a maximum. Minimum runoff occurs in September through November, when rainfall is 

low and soil moisture and ground-water storage are at a 

minimum (McMaster, 1967).

The waste-injection site is located in Melton Valley, a 

part of the Whiteoak Creek drainage basin (fig. 34). 

Chestnut Ridge forms the northwestern drainage 

divide, and Cooper Ridge, the southeastern divide of the 

drainage basin. Most of Bethel Valley (the laboratory 

area) is drained by Whiteoak Creek; however, Melton 

Valley is drained by Melton Branch, a tributary to 

Whiteoak Creek. Whiteoak Creek flows southwestward 

through Bethel Valley to a water gap in Haw Ridge and 

enters Melton Valley, where it is joined by Melton 

Branch; it then flows southwestward through a small 

impoundment known as Whiteoak Lake before entering 

the Clinch River (fig. 34).

The dolomite of the Knox Group of Chestnut Ridge is 

the principal aquifer in the Whiteoak Creek drainage 

basin. Bethel Valley is underlain by the Chickamauga 

Limestone. A substantial quantity of water is probably 

stored in many small openings in the weathered zone of 

the limestone within 30 m of the land surface. Low-flow 

measurements (the flow equaled or exceeded 90 percent 

of time is 0.085 m3/s) show that 90 percent of the 

Whiteoak Creek low flow originates as ground-water 

discharge from the dolomite of the Knox Group of 

Chestnut Ridge and the Chickamauga Limestone of 

Bethel Valley, and as ORNL plant effluents (McMaster, 

1967).

The Rome Formation of Haw Ridge forms the northwestern water divide of Melton Branch. This formation 

has very little capacity for receiving, storing and 

transmitting water. In the weathered rock, the occurrence of ground water is largely limited to small openings that occur along joints and bedding planes. Melton

TABLE 8. - Ground elevation affected by a grout injection at 152 m, July 

23, 1971, West Valley, N.Y.

Bench 

mark

Al

A2

Bl

B2

B3

B4

B5

B6

B7

B8

B9

Cl

Dl _____ 

D2

D3

D4 _____ 

D5

D6 _____ 

D7 _____ 

D8

D9

El

E2

E3

E4

E5 _____ 

E6 _____ 

E8 ___ 

E9

E10 ____ 

Ell ____ 

E12 _____

Fl

F2

F3

F4

F5

Gl

G2

G3

G4

G5

G6

HI

H2

H3

H4

H5

H6

H7

H8 _____ 

Jl

J2

J3

J4

J5

J6

J7

J8

Distance 

from 

injection 

well 

(m)

16.89 

51.08

7.59 

15.30 

30.36 

68.34 

92.08 

159.11 

250.12 

340.58 

430.19

37.73

7.65 

22.95 

60.84 

92.84 

153.71 

245.39 

336.74 

428.21 

488.41

7.62 

30.51 

60.93 

91.41 

152.40 

243.81 

315.16 

399.29 

490.73 

593.14 

688.85

7.59 

15.24 

68.55 

144.72 

227.62

7.68 

38.04 

76.23 

152.46 

243.84 

676.66

7.65 

23.07 

60.81 

91.17 

160.57 

253.99 

341.86 

746.76

7.62 

15.24 

33.50 

90.28 

157.67 

242.19 

333.18 

424.83

Altitude of benchmark, in meters

Before 

injection

423.95586 

416.85725

423.56822 

423.65289 

422.64138 

419.50151 

424.90601 

428.23041 

434.91805 

449.27322 

468.33834

424.60810

423.81577 

423.89557 

423.05368 

423.80447 

422.60438 

423.14275 

424.93817 

427.21890 

428.61936

423.57760 

423.90603 

423.88317 

423.79273 

424.59713 

425.00410 

426.36396 

426.36811 

427.64775 

425.99863 

429.60950

423.41191 

423.38692 

424.10131 

425.59922 

424.28053

423.30758 

423.77731 

423.50271 

424.83265 

423.47092 

421.84518

423.39116 

422.82359 

423.14147 

423.28265 

422.48252 

422.82039 

423.10218 

421.03304

423.40996 

423.22903 

420.21697 

423.95431 

423.00427 

424.31345 

427.78747 

429.44055

After 

injection

423.95763 

416.85871

423.57007 

423.65469 

422.64266 

419.50276 

424.90702 

428.23114 

434.91878 

449.27383 

468.33940

424.60978

423.81751 

423.89719 

423.05515 

423.80514 

422.60514 

423.14311 

424.93863 

427.21926 

428.61994

423.57919 

423.90773 

423.88490 

423.79441 

424.59835 

425.00468 

426.36396 

426.36799 

427.64729 

425.99814 

429.60914

423.41374 

423.38884 

424.10277 

425.60029 

424.28157

423.30947 

423.77914 

423.50424 

424.83384 

423.47175 

421.84564

423.39314 

422.82554 

423.14342 

423.28448 

422.48371 

422.82121 

423.10285 

421.03292

423.41182 

423.23092 

420.21874 

423.95549 

423.00540 

424.31458 

427.78875 

429.44165

Uplift 

(mm)

1.77 

1.46

1.86 

1.80 

1.28 

1.25 

1.01 

.73 

.73 

.61 

1.06

1.68

1.74 

1.62 

1.47 

.67 

.76 

.36 

.46 

.36 

.58

1.59 

1.70 

1.73 

1.68 

1.22 

.58 

0 

-.12 

-.46 

-.49 

-.36

1.83 

1.92 

1.46 

1.07 

1.04

1.89 

1.83 

1.53 

1.19 

.83 

.46

1.98 

1.95 

1.95 

1.83 

1.19 

.82 

.67 

-.12

1.86 

1.89 

1.77 

1.18 

1.13 

1.13 

1.28 

1.10
APPENDIXES: CASE HISTORIES 49

3.6

3.2

28

2.4

2.0

1.6

1-2 

0.8 - 

0.4 -

0.0

800

Surveyed uplift along B and F 

Surveyed uplift along C,D, and H 

Surveyed uplift along A, J, and E 

Surveyed uplift along G

700 600 500 400 300 200 100 0 100 200 300 400 500 

RADIAL DISTANCE BETWEEN SURVEY BENCHMARKS AND THE INJECTION WELL, IN METERS

600 700

FIGURE 33.-Calculated and surveyed uplift produced by a grout injection at 152 m, West Valley, N.Y.

TABLE 9. -Instantaneous shut-in pressure, calculated overburden pressure, tensile strength of shale, average cohesive force at fracture tip, and

value offt West Valley, N.Y.

Injection

No. Date Depth Injection 

(m) fluid

1 Oct. 9, 442 Water

1969. 

Oct. 9, 442 Water

1969.

2 June 26, 442 Water

1970.

Total Calculate 

injection pr

(m>) % specific 

gravity 

(MPa)

433 10.90 

433 10.90

425 10.40

d overburden 

 essare

By 

pressuredecay data 

(MPa)

10.84 

10.84

10.43

Instantaneous shut-in Calculated 

pressure tensile

Observed 

(MPa)

12.05 

11.98

13.29

(MPa) 

Predicted 

(MPa)

11.96 3.09 

11.96 3.92

15.20 3.87

Calculated 

average cohesive force at 

fracture tip, 

/T1 (MPa)

1.06 

1.06

1.78

Value 

of Remarks

/

0.34 Before 45-minute 

pause.

.27 After 45-minute 

pause.

0.45

3 Aug. 27, 

1970.

374 Water 343 9.16 9.49 9.87 9.89 4.15 0.73 0.18

4

5

6

May 10, 308

1971.

May 29, 152

1971.

July 23, 152 

1971.

Water

Water

Water 

and grout.

374 7.48

195 3.52

9 (water); 3.52 

142 

(grout).

7.36 8.06

3.10 3.80

___ Did not 

observe.

Regression 3.12

equation has 

not been 

established.

3.88 0.73

4.00 0.76-0.83

0.58

0.36

0.48

0.19

0.49

0.58-0.63

'Average cohesive forces at the fracture tip,/ T, are calculated on the basis of the regression equations of P and Q. The value of/ T calculated on the basis of the observed instantaneous shutin pressures are essentially the same as those based on the regression equations.

Valley is underlain by the Conasauga Group. Ground 

water in the Conasauga occurs principally in the 

weathered zone, where openings along joints and bedding planes have been slightly enlarged by weathering 

and circulating water. Because these enlarged openings 

occur only at shallow depths, 0-10 m below land surface, 

the total capacity of shale of the Conasauga Group for 

receiving, storing, and transmitting water is small 

(McMaster and Waller, 1965). In the late fall, periods of 

no flow have frequently occurred in Melton Branch 

(McMaster, 1963).

There is no known movement of ground water below a 

depth of 100 m. The isolation of the Pumpkin Valley 

member of the Conasauga Group is further 

demonstrated by the fact that the Pumpkin Valley contains small amounts of disseminated sodium chloride 

and methane gas (U.S. Energy Research and Development Administration, 1977). Cores taken from 30 m 

below the land surface showed no signs of iron stains, 

weathering, and solution cavity. A geothermal measurement (fig. 36) also indicates that there is no significant 

movement of ground water deeper than 200 m.
50 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

84°J20' 

WF^~^m RESERVATION OF DEPARTMENT OF ENERGY

V//J1 Jf*/^ r£\ J??*->\ ) I/*! (FORMERLY U.S. ATOMIC ENERGY COMMISSION RESERVATION)

^,^Vk-

(Formerly Third Experiment

84°l 20'

BASE FROM U.S.G.S.

BETHEL VALLEY QUADRANGLE,

TENNESSEE 1968

1000 2000 3000 4000 5000 6000 7000 FEET 

0_______05_______1_______1.5________2 KILOMETERS

Contour interval 20 feet (6.1 meters) 

Datum is meon sea level

FIGURE 34.-Location of hydraulic-fracturing-experiment sites, present fracturing site, and proposed site, Oak Ridge National

Laboratory, Tenn.
APPENDIXES: CASE HISTORIES 51

(>(88J3
SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRALILICALLY INDUCED FRACTURES

30

450 600 

DEPTH, IN METERS

1050

FIGURE 36.-Graph of temperature plotted against depth at the present fracturing site, Oak Ridge National Laboratory, Tenn. (from 

deLaguna and others, 1968).

SEISMICITY

Available information for the period 1699 through 

1973 indicates that no earthquakes have been reported 

within 16 km of Oak Ridge; however, earthquakes have 

been reported in the area predominantly to the south 

and east (fig. 38). The largest earthquake (intensity 

Modified Mercali VII) was recorded near Luttrell, 

Tenn., March 28,1913 (McClain and Meyers, 1970; U.S. 

National Oceanic and Atmospheric Administration and 

U.S. Geological Survey, 1975). However, no field 

evidence or literature on active or potentially active 

faults in the vicinity of the ORNL site have been found.

NATURE OF RADIOACTIVE WASTES PRODUCED AT THE 

OAK RIDGE NATIONAL LABORATORY

Radioactive wastes disposed of by grout injection and 

hydraulic fracturing at the ORNL site are produced by a 

number of different research, development, and production programs conducted at the ORNL, including basic 

radiochemistry studies; development of reactor-fuel

25

20

15

10

-5

AUG

JUN 

SEPT

OCT

JUL 

NOV

9 11 13 15 

PRECIPITATION, IN CENTIMETERS

17

FIGURE 37.-Graph of average monthly temperatures and precipitation, 

Oak Ridge, Tenn. (from U.S. Energy Research and Development Administration, 1977).

reprocessing methods; production of radioisotopes for 

medical, industrial, and research uses; production of 

transuranium isotopes for research; and operation of 

research reactors. The wastes are neutralized with 

sodium hydroxide to reduce corrosiveness and are 

stored in underground stainless steel tanks, which are 

periodically pumped to underground concrete collection 

tanks. The addition of sodium hydroxide causes some of 

the dissolved materials to precipitate from the waste 

solution. The precipitates settle as sludge at the bottom 

of the storage tanks. The liquid above the sludge is fed to 

an evaporator, which concentrates the liquid waste by a 

factor of 20 to 30. The concentrated waste is stored in 

the underground concrete collection tanks for temporary storage; it is then periodically disposed in shale 

by grout injection. Roughly 300 m3 of concentrated liquid waste is produced at the ORNL each year (U.S. 

Energy Research and Development Administration, 

1977). The approximate chemical composition and radionuclide content of the ORNL waste are shown in 

table 10 (deLaguna and others, 1971; Weeren, 1976;
APPENDIXES: CASE HISTORIES 53

85'

LOCATION OF EPICENTER 

O 2 Intensity IM-IV 

1 Intensity IV-V 

Intensity V-VI 

<$)! Intensity VII

Intensity unknown 

Q2 Magnitude 1-3.5 

01 Magnitude 4.6-4.7

Intensity refers to modified Mercalli scale. 

Number beside symbol indicates number

of earthquakes that occurred between

1699 through 1973. 

Number in bracket indicates depth of

earthquake in kilometers.

35°

85° 84°

10

i

20

i

FROM USGS BASE MAP, 0 30 MILES

STATE OF TENNESSEE ' 

0 10 20 30 KILOMETERS

FIGURE 38. -Location of epicenters near Oak Ridge, Tenn., determined on the basis of available information 

(McClain and Meyers, 1970; U.S. National Oceanic and Atmospheric Administration and U.S. Geological 

Survey, 1975) for the period 1966 through 1973.
54 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULIC ALLY INDUCED FRACTURES

TABLE 10 -Approximate waste composition produced at the Oak Ridge 

National Laboratory, Tenn.

[From deLaguna and others, 1971; Weeren, 1976; ERDA, 1977. M, moles per liter]

Compound or element

NaOH

Al(N03 )s-9H2 0

NH4N03

NaN03

Na2S04

NaCl

NaaCOa

A12(S04 )3

(NH4)_S04

137Cs

90g r

244Cm

Long lived radionuclides (half life > 30 yrs)

Composition

0.05 0.7 M

.005-0.04 M

.003 0.06 M

.1 1.0 M

.09 0.2 M

.04 0.2 M

.01-0.2 M

.005 0.2 M

.01-0.2 M

.3 Ci/L

.03 Ci/L

.3 mCiyL

< 10 nCi/g

U.S. Energy Research and Development Administration, 1977).

SUMMARY OF DISPOSED RADIOACTIVE WASTES

During 1964 and 1965, seven experimental injections 

had been made through the present disposal well. The 

first two experimental injections were made with synthetic wastes and the last five injections were made with 

actual wastes. Experimental results have indicated that 

grout injection by hydraulic fracturing is suitable and 

economical for disposal of the radioactive wastes at the 

ORNL; therefore since 1966 operational injections have 

been made periodically. At the end of 1978, a total of 17 

operational injections were made.

From 1964 through 1978, a total volume of 6,400 m3 

(excluding synthetic waste) of intermediate-level

TABLE 11.-Radioactive-waste injected in Pumpkin Valley shale, Oak Ridge National Laboratory, Tenn., 1964-1978

[NA, not analyzed]

Name of 

injection

Injection 

date

Injection 

depth 

(m)

Injection 

altitude (m)1

Waste 

injected (m3)

Grout 

volume (m3)

Solids/ 

liquids 

(kg/m3)

90Sr

(in Ci,

mCs 10,

except 23i

3Ru

Radionuclides 

'Pu and 244Cm, which are in grams)

8 °Co 144Ce 198Au 239Pu 2"Cm

Test injection

12 _______

22

4 _______

5 

Feb. 13, 1964 

May 19, 1965 

Aug. 16, 1965 

OOO fl

O*7O fl

97 A q

971 Q

OfiO 9

-46.7 

-40.3

-33.0

-24.4 

-24.4

141.2 

107.1 

126.8 

135.9 

558.7 

16.7 

242.2 

263.3

152.8 

143.0 

247.2 

217.5 

799.7 

21.5 

351.2 

467.1

75.2 

813.0 

1,565.5 

1,329.8 

842.0 

454.8 

719.0 

828.7

4.9 

.9 

608.0

330.0 

492.0

74 

50 

193

1,562 

3,358

0.4 

1.2 

35.0

2.0 

2.0

30 

0.1 

.1 

4.0 4,099

1.0 

14.0

Operational injection

ILW-IA - 

ILW-1B 

ILW 2A

TT W 9R

ILW-3A3 -

TT \\J QT3

Water test 

ILW-4A3 -

ILW-4B 

ILW-5 

ILW-6 

TT W 7

ILW-8 

ILW-9 

ILW-10 

ILW-11

ILW-12 

ILW-13 

ILW-14 

ILW-15 

ILW-16 

ILW-17

Total -

Total radioa

Dec. 12, 1966 

Dec. 13, 1966 

Apr. 20, 1967 

Apr. 24, 1967 

Nov. 28, 1967 

Nov. 29, 1967 

Dec. 13, 1967 

Apr. 3,1968 

Apr. 4,1968 

Oct. 30, 1968 

June 11, 1969 

Sep. 23, 1970 

Sep. 29, 1972 

Oct. 17, 1972 

Nov. 8, 1972 

Dec. 5,1972 

Jan. 24, 1975 

Apr. 29, 1975 

June20, 1975 

JuneSO, 1975 

Nov. 17, 1977 

Sep. 1, 1978

262 7

 262.7

 250.5

 250.5

947 ^

24 4

-24.4 

-21.4 

-21.4 

-21.4 

-21.4

-18.3

-18.3

-15.3

1 9 Q

-12.3 

-12.3 

-12.3 

-9.2 

9 2

-9.2

-3.1

141.7 

98.4 

308.1 

243.5 

117.3 

196.8

90.9 

235.4 

309.6 

300.3 

314.2 

275.2 

258.5 

320.8 

286.8 

97.3 

306.6 

314.0 

344.4 

208.9 

311.5

6,672.1

208.2 

152.1 

461.0 

411.0

555.5 

169.2

494.6 

435.9 

478.2 

551.4 

411.1 

431.5 

503.3 

495.0 

159.3 

477.3 

525.0 

549.0 

300.9 

520.4

10,689.9

744.7 

742.4 

718.5 

773.4

659.1

611.2 

671.1 

647.1 

659.1 

874.8 

934.7 

850.9 

862.8 

791.0 

755.0 

802.9 

503.3 

862.8 

838.9

41.0 

38.0 

564.0 

474.0

9,000.0

4,300.0 

500.0 

8,900.0 

2,747.0 

45.0 

231.0 

1,331.0 

1,099.0 

1,324.0 

3,368.0 

2,874.0 

138.3 

1,618.0 

90.0

40,118.1

11,500 

7,600 

31,329 

26,350

17,000

51,900 

69,400 

89,000 

44,833 

27,917 

23,359 

18,817 

23,486 

12,752 

35,750 

30,592 

26,390 

14,964 

22,270

590,446

1.0 16.0 20 

8.0 3.0 13 

99.0 236.0 

83.0 199.0

400.0 200.0

200.0 

300.0 100.0 

100.0 200.0 

236.0 72.0 

2,523.0 

376.0 

593.0 

379.0

5,338.6 1,045.2 4,132

NA NA 

NA NA 

NA NA 

NA NA

17.8 

18.5 

3.9 

28.60 

2.13 

None 

None 

None 

None 

.49 

None 

10.75 

None 

1.19

30 83.36

NA 

NA 

NA 

0.230 

.002 

.068 

.346 

1.791 

.012 

.214 

.043 

None 

None 

.027

2.733

NOTE. - Data sources: Injections 1-7, ILW-IA through ILW-2B, deLaguna and others, 1968,1971; ILW-3A through ILW-7, deLaguna and others, 1971; ILW-8 through ILW-11, Weeren, 

1974; ILW-12 through ILW-14, Weeren, 1976; ILW-15 through ILW-17, Weeren, written commun., 1979.

1Mean sea level.

2 Synthetic waste.

3Stopped owing to difficulties. Activity merged with B.
APPENDIXES: CASE HISTORIES 55

radioactive waste (5.6 x 10~3 ^Ci/mL < specific activity 

< 5.3 x 102 jiCi/mL containing mainly of 90Sr and 137Cs) 

was disposed of through the present injection well at 

depths ranging from 244 to 288 m (table 11). The waste 

contained a total activity of 641,300 Ci among which 

were 590,400 Ci of 137Cs, 40,000 Ci of 90Sr, 80 g of 239Pu, 

3 g of 244Cm, and 10,500 Ci of other radionuclides, including 60Co, 106Ru, and 144Ce.

INJECTION PROCESSES AND THE DISPOSAL PLANT

The injection processes and disposal plant at the 

ORNL have been discussed by many investigators 

(deLaguna and others, 1968,1971; Weeren, 1974,1976). 

The following paragraphs are a summation of these 

reports.

The major equipment used in injection consists of a 

waste pump, a jet mixer, a surge tank, and an injection 

pump (fig. 39). An artist's sketch of the disposal plant is 

shown in figure 40. The injection capacity of the wasteinjection pump is 40 MPa at 3 m3/s and 7 MPa at 20 m3/s. 

A standby injection pump (fig. 39) having a similar injection capacity is equipped to flush the injection well with 

water to free it of grout in the unlikely event of a failure 

of the injection pump. Five underground waste storage 

tanks (figs. 39, 40) having a total capacity of 340 m3 

were constructed at the disposal site to receive wastes

delivered from storage tanks at the laboratory site 

before injection.

Solids that consist of cement, fly ash, attapulgite clay, 

illite or its equivalent, and a retarder, such as delta 

gluconolactone, are preblended before injection in accord with the desired proportion designed by laboratory 

tests. The solids are mixed by blowing them back and 

forth between two pressure tanks; they are then stored 

in four bulk storage bins for injection use (fig. 41). During each injection the preblended solids are aerated and 

allowed to flow through a metering hopper into a mixer. 

A mass flowmeter was installed below the metering hopper to continuously weigh the solids. Concentrated liquid waste is pumped into the mixer under pressure (0.7 

MPa). Preblended solids are then dropped into the mixer 

by gravity through a chute and are mixed thoroughly 

with the waste by a jet stream (figs. 42, 43,) thus forming the grout, which is continuously discharged to a 

surge tank, from where it is injected into shale by injection pump (fig. 42). The control of the proportion of 

waste with the preblended solids is critical. The variation should be within 5 percent of the designed proportion but not exceed 10 percent. The mix ratio is controlled manually by referring to mass-flow-meter and 

waste-flow-meter readings.

A considerable volume of water is required for casing 

slotting and equipment washing. The water is contaminPREBLENDED SOLIDS 

STORAGE

WASTE-STORAGE TANKS

STANDBY

INJECTION

PUMP

INJECTION 

WELL

FIGURE 39.-Schematic diagram of the hydraulic-fracturing and waste-grout-injection facility, Oak Ridge National Laboratory,

Tenn. (Courtesy of Oak Ridge National Laboratory.)
WASTE-STORAGE TANKS

GRAY SHALE ^^H^S^V- > **

LIMESTONE BED

RED SHALE

WELLHEAD CELL 

HIGH-PRESSURE PUMP

GROUT SHEETS

o

w

DOT TJ 

O Ul

o 

oC/2

H WC/2

sffi K; o » 

> d ro

2 Od o

FIGURE 40. - Artist's sketch of the hydraulic-fracturing and waste-grout injection, Oak Ridge National Laboratory, Tenn. (Courtesy of Oak Ridge National Laboratory.)
APPENDIXES: CASE HISTORIES 57

FIGURE 41.-Photograph showing equipment for proportioning and blending dry solids for waste-grout injection, Oak 

Ridge National Laboratory, Tenn. (Courtesy of Oak Ridge National Laboratory.)
58 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

PREBLENDED

SOLIDS -i 

METERING 

HOPPER -

kilogram /min

^ MASS 

FLOWMETER

© 

m 3/s

SURGE TANK

_^ GROUT TO

INJECTION PUMP

A WASTE 

T SOLUTION

FIGURE 42.-Diagram showing the arrangement of the mass flowmeter in a 

mixer cell for waste-grout injection, Oak Ridge National Laboratory, Tenn. 

(from deLaguna and others, 1968).

 I « I %»

FIGURE 43.-Photograph showing conveyors for moving preblended solids from storage bins to a mixer for waste-grout 

injection, Oak Ridge National Laboratory, Tenn. (Courtesy of Oak Ridge National Laboratory.)
APPENDIXES: CASE HISTORIES 59

FIGURE 44.-Photograph showing cell enclosing the wellhead of the waste-injection well, Oak Ridge National Laboratory,

Tenn. (Courtesy of Oak Ridge National Laboratory.)

ated and must be injected with waste. To achieve a maximum disposal efficiency, the contaminated water must 

be reused, and for this purpose a concrete-lined waste 

pit was constructed to temporarily store the contaminated water (fig. 40).

An emergency waste trench was also dug as a precaution against the possibility of a wellhead rupture (fig. 

40). During such an incident the pressurized grout would 

flow back from the injection well and discharge to the 

trench; the trench would then be covered with earth fill.

The mixer, surge tank, injection pump, waste pump, 

and injection wellhead are all enclosed in concrete cells 

constructed with 30-cm thick walls and roofed with 

sheet metal to avoid radiation exposure of operators and 

to limit areas that could be contaminated if the piping or 

equipment ruptures or leaks (figs. 44, 45). A safety-glass 

window was installed in a wall of the cell to allow inspection during injection.

The injection well consists of a surface casing 46 m in 

length and 25 cm in diameter. The surface casing was 

cemented by pressure over the entire length. A small 

casing, 14 cm in diameter and 320 m in length, was

placed inside the surface casing and was also pressure 

cemented for the entire length, as shown in figure 46.

Two different types of wellheads are used during injections. One is used for slotting, and the other, for injection. During slotting, a packoff flange is bolted to the 

14-cm tubing head (fig. 47). A string of tubing 64 mm in 

diameter with a swivel attached is placed at a desired injection depth and is supported by a crane. A stream of 

slurry consisting of sand and water is pumped down 

through the tubing under pressure and discharges out of 

a jet nozzle. The tubing string is slowly rotated by a 

hydraulic power swivel; therefore, the abrasive under 

high pressure can cut the casing, cement wall, and shale 

in a complete circle. The slurry, after most of its energy 

has been spent, returns to surface throught the annulus. 

The schematic diagram of the slotting operation is 

shown in figure 48. The contaminated water used in slotting is stored in a waste pit and can be used for fracture 

initiation or injected along with waste.

During waste injection the packoff flange is replaced 

by an adapter flange and shut-off valve (figs. 49, 50). 

The adapter flange supports the 64 mm tubing string,
60 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

FIGURE 45.-Photograph showing bins, waste-injection wellhead cell, injection pump, and standby injection pump, Oak Ridge 

National Laboratory, Tenn. (Courtesy of Oak Ridge National Laboratory.)

which is placed at a depth several meters above the 

desired injection depth. The annulus between the tubing 

string and the 14-cm casing is filled with water. Since 

the tubing string is open to the annulus near the bottom 

of the well, the pressure in the annulus is equal to injection pressure, excluding friction loss in the tubing. After 

a fracture is initiated by water, the grout injection 

follows. When the last of the waste solution has been injected, a small volume of fresh water is pumped down 

the well to "overflush" the grout out of the injection well 

for use in the next injection. The injection well is then 

shut in under pressure until the grout sets. Several injections can be made through the same slot (table 11); 

the old slot is then plugged with cement, and a new slot 

is made a few meters above the old slot.

INJECTIONS

By the end of 1978, 25 injections had been made 

through the present injection well. Seven were experimental injections, one was a water injection, and the

others were operational grout injections. Trouble with 

cement flow occurred during injection 6, an experimental injection. The injection was made in two stages, 

which were named 6A and 6B. Four operational injections were also named A and B (table 11) because the injection was interrupted either owing to the lack of 

storage capacity at the disposal site, such as during injections ILW-1A and ILW-1B, or because of difficulties 

of achieving desirable mixing ratio of solids and wastes, 

such as during injections ILW-2A and ILW-2B. After 

the fourth operational injection, the injection number 

was not subdivided again, even if the injection was interrupted.

Most of the injections have been discussed by many investigators (deLaguna and others, 1968, 1971; Sun 

1969; Weeren, 1974, 1976). The examples of injections 

discussed in the following sections are chosen to show 

the correlation between the grout size estimated on the 

basis of the uplift model (see p. 18) and that observed in 

the field and to show the results of operational grout
APPENDIXES: CASE HISTORIES 61

INJECTION WELL

fi 

fe

46 m of 241/2-cm 

surface casing

Cement

-320 m of 

14-cm casing

FIGURE 46. - Schematic diagram showing construction of the wasteinjection well, Oak Ridge National Laboratory, Tenn. (from 

deLaguna and others, 1971).

mixing, as well as the procedures for determining the attitudes of grout-sheets by gamma-ray logs.

EXPERIMENTAL INJECTIONS

Two experimental injections were made in September 

1960 through the second experimental well. Twentyfour core holes were drilled to determine the extent and 

thickness of the grout sheets. Precise leveling was run

after each injection. The injection data are summarized 

in table 12, and the thickness of grout sheets measured 

in core holes and the uplift of the ground surface are 

shown in figures 2 and 3. The calculated maximum grout 

thickness and radius of grout sheet are shown in table 

12, and a comparison of calculated with observed values 

for uplift are shown in figures 51 and 52. Generally 

speaking, the calculated uplift is in good agreement with 

the observed uplift.

The core-hole data indicates that the induced fractures 

were probably formed in the weakest bedding planes 

and grout did not flow radially from the injection well. 

The maximum thickness of grout sheet did not occur 

near the injection well (figs. 2, 3). This was probably owing to water injection at the end of each injection to 

clean grout out of the injection well. The thickness of 

grout sheet as measured in cores is less than the 

calculated fracture separation (table 12). This is not surprising in view of the fact that the induced fractures 

must have enough separation for slurry to flow during 

injection and because the calculated fracture separation 

is the condition that existed during the injection time. 

After the injection the separation of the induced fractures was reduced owing to compaction under overburden pressure. The grout in the cores appeared to be 

nearly as hard as the shale into which the slurry was injected (fig. 1).

The uplift model was further tested by a comparison of 

the uplift calculated with that observed during the experimental injections 1 through 7 at the present disposal 

site, 0.8 km west of the second experimental site. The 

comparison is shown in figure 53 and apparently indicates a good agreement. The locations of survey 

benchmarks are shown in figure 54. The uplifts were 

also surveyed after operational injections ILW-7 and 

ILW-11. However, the author has no detailed injection 

data for these injections; therefore, there are no calculations of uplifts for comparison.

TABLE 12. -Physical properties of grout, injection pressure, calculated 

grout radius, and maximum fracture separation, September 1960, 

Oak Ridge National Laboratory, Tenn.

Parameters Injection date

September 3 September 10

Inside diameter of injection casing - millimeters 

Injection rate cubic meters per second 

Injection volume cubic meters - 

Wellhead breakdown pressure megapascals 

Bottom-hole injection pressure do 

Calculated overburden pressure do 

Density of fluid kilograms per cubic meter 

285 

104 

.009 

346 

15.89 

12.75 

16.28 

13.58 1.8x10* 

.1 

1.38 x 10s 

mo

212 

104 

.016 

503 

15.20 

14.91 

17.56 

10.10 

1.8x10* 

.1 

1.44 x 10s

nfic;

1C newtons-sec per square meter - 

Calculated grout radius meters - 

Calculated maximum fracture

separation millimeters - 

Observed grout thickness do -

16.04

77

29.69

65
62 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

ROTATING SWIVEL

PACKOFF FLANGE

TUBING HEAD

TUBING SLICK JOINT

(SUPPORTED BY CRANE

CASING HEAD

SURFACE CASING

CASING

FIGURE 47. - Schematic diagram showing wellhead arrangement for slotting by hydraulic jet, Oak Ridge National 

Laboratory, Tenn. (Courtesy of Oak Ridge National Laboratory.)
APPENDIXES: CASE HISTORIES 63

1

ROTATING 

SWIVEL SAND

INJECTION 

PUMP

PUMP

CONTAMINATED 

WATER PIT

SPENT SAND

JET

FIGURE 48. - Schematic diagram showing slotting operation for hydraulic-fracturing and waste-grout injection, Oak 

Ridge National Laboratory, Tenn. (Courtesy of Oak Ridge National Laboratory.)
64 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

-PLUG CONTAINER

SHUT-OFF VALVE

TUBING-HEAD ADAPTER

TUBING STRING

TUBING HEAD

CASING HEAD

BULL PLUG ---

SURFACE CASING

FIGURE 49. - Schematic diagram showing wellhead arrangement for 

waste-grout injection, Oak Ridge National Laboratory, Tenn. 

(Courtesy of Oak Ridge National Laboratory.)

OPERATIONAL INJECTIONS

At the end of 1978, there had been 17 operational injections. A total volume of 5,000 m3 of radioactive liquid 

waste contained in 8,100 m3 of grout had been injected 

at depths between 244 m and 266 m (table 11). Half of 

the injections have been discussed by Weeren (1974; 

1976) and deLaguna and others (1968). The following 

discussions were summarized from these reports.

During September through December 1972, injections 

ILW-8 through ILW-11 were made at a depth of 254 m. 

Four tanks of waste were injected. The chemical composition of waste is shown in table 13. Waste contained 

in tank 1 and part of the wastes in tank 2 were injected 

during injection ILW-8. Only waste in tank 2 was injected during injection ILW-9. Injection ILW-10 included 38 m3 of waste remaining in tank 2 and of the wastes 

in tanks 3 and 4. The remaining wastes in tanks 3 and 4 

were injected during injection ILW-11. The composition 

of solids used in all four injections was approximately as 

follows:

Materials Percent by weight

Portland cement _________________________ 38.45 

Fly ash ________________________________ 38.45 

Attapulgite 150 _________________________ 15.38 

Grundite _____________________________ 7.69 

Retarder _____________________________ .03

The average solids and waste mixing ratio is indicated in 

table 11. The concentrations of radionuclides in the injected waste are shown in table 14. It was learned during the injections that bleed back after injection is an important factor, as is discussed in the following section.

BLEED BACK THROUGH THE INJECTION WELL

No matter how well the slurry is mixed there always is 

liquid separation. The unbound water eventually leaks 

through fracture walls into shale pores under pressure. 

To reduce as much as possible the amount of separated 

unbound water leaking from grout into a shale formation, it is necessary to bleed back the unbound water to 

the ground surface through the injection well after the 

grout has been solidified.

A summary of the bleed-back data is shown in table 

15. It is not surprising that both wellhead pressure and 

initial rate of bleed back decrease with increase in shutin time because the unbound water leaks through fracture walls under pressure during such time, despite the 

low permeability of the shale. The concentrations of raTABLE 13. -Chemical composition, in moles per liter, of waste disposed 

of by injections, September-December, 1972, Oak Ridge National 

Laboratory, Tenn.

[From Weeren, 1974]

Constituent

Na+

A13+ _

NH;

OHN03~

cisof

co32 -

1

1.66

.007

.003

.18

.84

.093

.094

.193

1

z

1.24

.037

.03

.28

1.03

.217

.183

.288

'ank

3

0.57

.002

.044

.15

.30

.049

.111

.093

4

0.59

.0011

.05

.16

.30

.044

.125

.10
APPENDIXES: CASE HISTORIES 65

FIGURE 50.-Photograph showing well-head of injection well, Oak Ridge National Laboratory, Tenn. (Courtesy of Oak

Ridge National Laboratory.)
66 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

EXPLANATION

Surveyed uplift along line between benchmarks 4A and 10D -I 

Surveyed uplift along line between benchmarks 3C and 3E 

Surveyed uplift along line between benchmarks 6B and 6F ~~j 

Calculated uplift

400 300 200 100 0 100 200 300 400 

RADIAL DISTANCE BETWEEN SURVEY BENCHMARKS AND THE INJECTION WELL, IN METERS

600

FIGURE 51. -Calculated and surveyed surface uplift produced by the grout injection, Sept. 3, 1960, second 

experiment site, Oak Ridge National Laboratory, Tenn. (Locations of benchmarks are shown in figs. 2 

and 3.)

TABLE 14. Specific activity, in curies per liter, of major radionuclides contained in wastes disposed of by injections, 

September-December 1972, Oak Ridge National Laboratory, Tenn.

[From Weeren, 1974]

Radionuclides

SOgj.

137Cs

106Ru

2<»Cm

239pu

Injection number

ILW-8

1.65x10-'

1.01 x 10'1

9.17 xlO"3

6.74 xlO'7

4.76 xH)-7

ILW-9

8.93 x 10-* 

9.04 x 10-2 

1.45 xlO'3 

2.18xlO-5 

None

ILW-10

4.15 xlO~3 

5.87 x 10-2 

1.85 xlO~3 

8.98 xlO'6 

None

1LW-11

3.83 x 10'3 

8.19 xlO'2 

1.32 x 10'3 

5.20 x 10-" 

None

dionuclides in the bleed-back water are shown in table 

16. Although the bleed back is only 4 percent of the total 

injected volume and the radionuclides contained in the 

bleed back are only several tenths of one percent of the 

total injected radionuclides, the concentration of radionuclides in the bleed back is still high, and the bleed 

back was therefore stored for use during the next injection. Because of the low permeability of the shale, some 

of the separated liquid that could not be bled back 

through the injection well would probably be trapped in 

induced fractures or in the shale. During the drilling of 

observation well S-100, when the grout sheet of experimental injection 3 was intersected at a depth of 276 

m, water flowed slowly from the grout seam. A sample 

of the flowing water was anaylzed, indicating the following results: Cl~, 36,500 ppm (parts per million); Na + , 

31,100 ppm; NO;, 28,600 ppm; Ca2+, 2,930 ppm; OH~, 

2,000 ppm; S042 -, 1,620 ppm; Mg2+ , 380 ppm; H3 , 

7.3xlO- 7 Ci/L; 90Sr, 6.8xlO- 8 Ci/L; and 137Cs, 

3.7xlO- 7 Ci/L, (deLaguna and others, 1968). This finding raises the concern that free radionuclides may be 

left in the shale, whether as a result of phase separation 

or of other causes. The bleed-back data and the water 

found in the grout seam indicate that the amount of free 

radionuclides in the shale is low. If the ground-water 

flow paths from the injection area to a nearby groundwater body as long and the shale's permeability is low 

and its adsorption capacity high, then the possibility 

that radionuclides in the unbound water could migrate 

into the nearby biosphere is further reduced by radioactive decay, as well as hydrodynamic dispersion. 

However, a series of observation wells constructed 

along the perimeter of the injection area and in formations lying above the injection zone are required to 

monitor the possible migration.

TABLE 15.-Bleed back from injections, September-December 1972, Oak Ridge National Laboratory, Tenn.

[From Weeren 1974]

Injection

ILW-8

ILW-9

ILW-10

ILW-11

Injection 

date

Sep. 29, 1972

Oct. 17,1972

Nov. 8, 1977

Dec. 5,1972

Date wellhead 

valve opened

Oct. 9,1972

Oct. 27, 1972 

^ov. 20, 1972

Nov.30, 1972 

iDec. 14, 1972 

iDec. 29, 1973

ifan 1Q 1Q7^

Apr. 4,1973

Days 

after 

injection

10 

10 

12 

22 

9 

24 

45 

120

Well-head 

pressure 

at time valve 

opened 

(MPa)

1.69 

2.14 

1.41 

1.03 

1.69 

1.17 

0.97 

0.57

Initial flow 

rate 

(ms/s)

1.16xlO-E 

1.26 xlO-4 

4.99 xlO-4 

2.71 x 10-4 

3.22 xlO-4 

1.70xlO-4 

1.01 x 10-4 

4.73 xlO-5

Final flow 

rate 

(m3/s)

6.52xlO-6 

7.57 xlO-5 

4.10xlO-4 

2.33 xlO-4

5.99 xlO-7

Recovered 

volume 

(m3)

4.40 

12.80

2.50 

2.20 

2.16 

1.60 

1.10 

243.90

"Valve closed again. 

2Measured on Apr. 22, 1973.
APPENDIXES: CASE HISTORIES 67

EXPLANATION 

Surveyed uplift along line between

benchmarks 4A and 10D 

Surveyed uplift along line between

benchmarks 3C and 3E 

Surveyed uplift along line between

benchmarks 6B and 6F

400 300 200 100 0 100 200 300 400 

RADIAL DISTANCE BETWEEN SURVEY BENCHMARKS AND THE INJECTION WELL, IN METERS

500 600

FIGURE 52.-Calculated and surveyed surface uplift produced by the grout injection, Sept. 10, 1960, second experiment site, Oak Ridge National Laboratory, Tenn. (Locations of benchmarks are shown in 

figs. 2 and 3.)

TABLE 16. -Specific activity, in curies per liter, of radionuclides in 

bleed-back solution, September-December 1972, Oak Ridge National 

Laboratory, Tenn.

[From Weeren, 1974. NA, not analyzed]

Injection

ILW-8 ILW-9 ILW-10 ILW-11

Radionuclides

Gross a

9oSr

106Ru

134Cs

6°Co

< 4.5X10-9 

9.8 xlO'6

NA 

NA 

NA

4.0 xlO-8 

4.8 xlO-6 

5.5 x lO'4 

6.9x10-" 

8.5 xlO-6 

6.6 xlO-6

NA 

1.4 xlO-4

NA 

NA 

NA

1.5xlO-8 

1.5 xlO-4 

6.6 x ID'4

NA 

NA 

NA

Other

Na*

ph

24 mg/mL 

12.3 mr

22 mg/mL 

11.4

35.3 mg/mL 

10.0

POSITION OF GROUT SHEET

The extent and altitude of the grout sheet can be 

determined by coring after the grout is solidified; 

however, this process is costly and time consuming. If a

series of observation wells has been constructed and if 

the injected wastes contain gamma-ray-emitting radionuclides, then one alternative would be to obtain 

gamma-ray logs in the observation wells before and 

after injection. Intensified gamma-ray peaks that are 

above those of background gamma-ray activity of shale 

would indicate that the induced fractures have intercepted the wells at the depth indicated. In logs made 

after two or three injections, it is difficult to associate 

the observed gamma-ray peaks with the appropriate injections.

Only logs made after each injection are available for 

injections ILW-8 through ILW-11 (Weeren, 1974). 

Figure 55 indicates the location of the observation wells 

in which the gamma-ray logs were run. Figure 56 shows 

the grout sheets found in the observation wells projected 

on a line passing through the injection well in the direction along the formation dip. The actual observed grout 

sheets intercept the observation wells at altitudes and 

locations listed in table 17. From figures 55, 56, and 

table 17, it seems that the grout sheets have formed

EXPLANATION 

Surveyed uplift along line between

benchmarks B9, X, and C8 

Surveyed uplift olong line between

benchmarks A9, X, and D7

400 300 200 100 0 100 200 300 400 500 600 700 

RADIAL DISTANCE BETWEEN SURVEY BENCHMARKS AND THE INJECTION WELL, IN METERS

FIGURE 53.-Calculated and observed surface uplift produced by the experimental injections 1 through 7, 

present fracturing site, Oak Ridge National Laboratory, Tenn. (Locations of benchmarks are shown in 

fig. 54.)
68 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

( A9

EXPLANATION

xA9

Benchmork

®

ln|edion well

xA8 

xA7 

xA6 

(A5

xA4 

:A3

cA2

<C2

xC3

xC4

X AI 

XX xBI B9

xC8 X C7

*C5

xB2 xB3 B5

xDI

xC6 CD1I5

D4x xD3 X D2 

xD5 

xD6

xD7

0 50 100 METBS

FIGURE 54. -Locations of benchmarks, the present fracturing site, Oak Ridge National Laboratory, Tenn.

TABLE 17.-Altitude, in meters referred to mean sea level, of grout 

sheet determined from gamma-ray logs made in observation wells, 

September-December 1972, Oak Ridge National Laboratory, Tenn.

[From Weeren, 1974. NF, not found]

Observation well

Injection 

altitude ___ 

W 300 _____ 

NW 100 ___ 

N 100

N 150

NE 125 _____ 

E 320

S100

S220 ____

Injection

ILW-8

-12

NF 

-5 

NF 

NF 

NF 

NF 

-14 to 

NF

ILW-9

-12

-12 to 

NF 

NF 

-10 

NF 

NF 

-16 -16 

NF

ILW-10

-12 

-14 -3 to -6 

14 

12

5 to 7 

4 to 10

NF 

NF 

NF

ILW-ll

-12

NF 

9 

7 to 12 

3 to 5 

-2 to 4 

NF 

-7

NF

along bedding planes and lie in an interval 20 m above or 

below the injection altitude; however, these data might 

not indicate the true altitude of the grout sheets because 

no data are available regarding well deviations. The experience obtained during a later site investigation indicated that measurements for unadjusted altitudes of 

grout sheets were commonly 7-8 m higher than those 

adjusted for well deviation, and that determinations of 

the location of the grout sheets also were shifted several 

tens of meters away from those of the surface location of 

the observation wells (see fig. 62). Therefore, these 

unadjusted results may be in error.

MONITORING SYSTEM

In addition to observation wells for gamma-ray logging, the ORNL also constructed a series of so-called 

rock-cover monitoring wells. The well location is indicated in figure 55. These wells are cased and pressure 

cemented to a depth of 152 m and have 30 m of open hole 

below the cased and cemented section (fig. 57). The purpose of these rock-cover wells is to determine the integrity of the shale formation lying above the wastedisposal zone to insure that no vertical fractures were 

formed owing to the injections and that surface water 

could not migrate to the waste-disposal zone by way of 

such fractures. The integrity test is done by pumping 

water into rock-cover wells at a standard wellhead 

pressure of 0.5 MPa to observe the change of rate of acceptance before and after injection. The tests are 

repeated after about every fourth injection.

Three types of response to the tests have been observed. First, wells may take no measurable amount of 

water; second, may take a small amount of water in the 

first hour and then a decreasing amount thereafter. In 

the third type of the response, the well may take the 

same small amount of water during the first and second 

hour of the test (deLaguna and others, 1971; Weeren, 

1974). During the experimental injections, pressure 

variations were observed in the rock-cover wells filled 

with water and equipped with pressure gages. In the
APPENDIXES: CASE HISTORIES 69

EXPLANATION

 Rock cover well

o Cased observation well

 N-275

NW-250

NW-175*

NW-100o

N-200

o N-150 NE-200

N-100 

o

o NE-125 

 NE-125

W-300 

(JOY WELL)

INJECTION WELL

W-300

S-100o

E-300 o E-320

0 10 20 30 40 METERS i _i i i i

 S-200 

o S-220

FIGURE 55. -Locations of observation wells, at the present fracturing site, Oak Ridge National Laboratory, Tenn. (Courtesy of Oak

National Laboratory.)

N150 W300 NW100 N100 NE125 Injection Well S100 S220

-53 30

CD

CD

w 20

in E 

S | 10

|I

LLJ

Q _

^ro 10

"* 1

| 20

O

m 30

_

~

_

X"

>^

0°°°°°^

1

/

/

/o°°°°

1

 v

 £J£I£.

°0 0

 "--iu'"°7~"~~"

........... «. s<.^.

°°

i

\ 

+ \

"" * X

***\

- ^^3T

0°°° '

Injection

level

Projected *

well location

Injection ^ 1 g 1 4 ooo0 oo 0 °°

/ei/e/ |L^^;o° 0 °°"

/oo° 0 °°°°°° ILW1 1 .,,,. ' "

**Vrr---l'_'lI,".'_ "-W8

"""" /- ...

I I

o0 o Well plugged, i Vertical

o^ out of service ; interval of

i grout

1 sheet

i . Well with nonintersectec

t . i line indicates no 

] grout sheet was found

in the well

" 0 ° 0o ° 0o °oo 0

1 1 1

_

_

-

300 200 100 200 300 500 600

NW SE

PROJECTED DISTANCE FROM INJECTION WELL, IN METERS

700

FIGURE 56.-Cross-section showing the grout sheets formed by waste injections ILW-8 through ILW-14, Oak Ridge National 

Laboratory, Tenn., as interpreted from gamma-ray logs made in observation wells after injections and projected on a line (AA1 , 

fig. 55), in the direction along dip and passing through the center of the injection well.
70 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

Rock Rock

cover Observation well for Injection Observation well for cover

well gamma-ray logging we)| gamma-ray logging Ground surface we||

t

t-

^Cement

 Open hole

Shale

t

Shale

/Waste grout sheets

t

I i

LJ

^Casing

^Cement

Shale

/Slotted by 

/ hydraulic jetting

I

t

r 

/ _ t

"^Tubing Cement /|

Xtement ;

Open hole*-!

Shale

Shale

away by water injection 

at end of grout injection

Shale

FIGURE 57. - Schematic diagram showing the injection well, observation wells, and waste grout sheet in shale, Oak Ridge National

Laboratory, Tenn.

area where the grout sheets were detected by gammaray logs, the pressure in the rock-cover wells rose, while 

in the area where the gamma-ray logs indicated no grout 

sheets, the pressure in the rock-cover wells dropped 

slightly (deLaguna and others, 1971). This evidence probably can be explained by changes in strain around the 

open-hole section of the rock-cover wells. In the groutsheet area the shale is probably compressed by uplift due 

to the accommodation of the injected grout thus increasing pressure in the rock-cover wells. The uplift does not 

stop at the edge of the grout sheet and must extend 

away from the edge without shearing the rock. 

Therefore, the volume of rock beyond the edge of the 

grout sheet should expand, thus increasing the rock 

porosity slightly, which causes the pressure in the rockcover wells to drop slightly. The pressure changes 

measured in rock-cover wells and the grout sheets indicated by gamma-ray logs for the injections ILW-8 

through ILW-11 are shown in table 18.

SITE EVALUATION

Because the present disposal site approaches its full 

injection capacity and the disposal facility can not handle the injection of accumulated sludge, a new fracturTABLE 18. -Rock-cover wells having positive or negative, difference in 

pressures -measured before and during an injection and results of 

gamma-ray-logs, September-December 1972, Oak Ridge National 

Laboratory, Tenn.

[From Weeren, 1974]

Injection

ILW-8

ILW-9

ILW-10

ILW-11

Results of 

gamma-ray log

Positive

NW 100

S 100 

W300

N 150 

SIOO

W300

NW100 

N 150 

N 100 

NE 125 

NW100

N 150 

N 100 

NE 125 

S 100

Negative

W300 

N 100 

N 150 

NE 125 

E 320 

S220 

NW 100 

N 100 

NE 125 

E 320 

S220 

E 320 

SIOO 

S 220

W300 

E 320 

S220

Pressure difference in rock cover well

Positive

NW175 

NW250 

NE 125

NE 125 

NE 200 

S200

NW175 

N275 

N200 

NE 125 

NE200 

NW 175 

N200 

NE 125 

NE 200

Negative

N275 

N 200 

NE 200

E 300 

N200

N275 

NW250 

W300 

S200 

E 300

NW250 

W300 

S200 

N275 

E 300

Ambiguous1

W300 

S200 

E 300

W300 

NW 175

NW250

'No clear sign of positive or negative pressure.

ing site was proposed, which is 245 m south of the present facility (fig. 34). The new site was evaluated jointly 

by the ORNL and the USGS in 1974 (Sun, 1976; Weeren 

and others, 1974). The following sections are a summation of the evaluation.
APPENDIXES: CASE HISTORIES 71

TEST DRILLING

Although the proposed site is only 245 m from the 

present disposal site, where numerous test holes and injections had been made in past years, one test hole with 

core was drilled at the proposed site to insure that the 

subsurface geology and hydrology would not deviate 

greatly from that at the present site. Cores were taken 

from depths of 212 to 362 m. In the interval from 212 to 

250 m the rock is gray shale interbedded with thin 

limestone layers. From 250 to 302 m the shale is purple 

and silty and lacks limestone layers. From 302 m to the 

top of the Rome Formation (357 m) the shale is gray or 

purple and increasingly sandy. From 357 to 362 m the 

rock is hard, white sandstone interbedded with shale 

and is part of the Rome Formation. Bedding planes are 

very evident and dip 10°-20° SE. The subsurface 

geology indicated by cores is similar to that at the present site. The purple and gray shale between 250 and 357 

m comprises the Pumpkin Valley Shale of the Conasauga Group, into which radioactive waste is scheduled 

to be injected.

The test hole was converted into an observation well, 

known as the South-observation well. Gamma-ray logs 

were made in this well before and after the well was 

cased and cemented. Three more observation wells, the 

East-, West-, and North-observation wells, were constructed at a radial distance of 60 m from the injection 

well and also were cased and pressure cemented. The injection well was constructed with a 14-cm casing and 

was pressure cemented in a way similar to that of the 

present injection well. The locations of all wells are 

shown in figure 58 and are listed in table 19. Gamma-ray 

logs were also made in all wells before they were cased 

and pressure cemented. Thereafter, gamma-ray logs 

were made again in only some of the wells. These 

gamma-ray logs were used to determine not only the 

background level of gamma-ray activity of the injection 

shale but also the contacts between rock units.

Laboratory determinations of rock tensile strength 

had never been made for shales at the New York and 

Oak Ridge sites. Therefore, the author took advantage 

of this site evaluation to determine, in the laboratory, 

the tensile strength of the shale scheduled for injection 

to make a comparison with tensile strength calculated 

from test injections.

Well deviation, determination of dip and strike, and 

tensile strength of the injection shale are discussed in 

the following sections.

WELL DEVIATION

All wells drift from the vertical axis, as indicated by 

deviation logs. All measured depths were corrected for 

the angle of deviation to obtain true vertical depths and

N17300

N17200

NI7100

N17000

§ N16900 

o

N16800

N16700

N16600

N16500

N16400

N16300

N16200

Joy we

Injection well 

at present 

frocturingfacility site

North-observation 

well

Injection well at 

proposed site East-observotion

West-observation 

well

New East-observation 

well

0 10 20 30 METERS

South-observation 

well

E27900 E28000 E28100 E28200 E28300 E28400 E28500 E28600 E28700 

OAK RIDGE NATIONAL LABORATORY COORDINATES

FIGURE 58.-Locations of wells, at the proposed disposal site, Oak 

Ridge National Laboratory, Tenn.

TABLE 19. ORNL coordinates and altitude, in meters above mean sea 

level, of wells at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn.

Well

Injection well at present site - 

Injection well at the proposed

Coordinates

N 17155

16503 

16503 

16445 

16304 

16502 

16702

E 28617

28178 

28378 

28307 

28179 

27978 

28172

Altitude

241.3

240.3 

240.2 

241.3 

243.6 

238.5 

235.1

true horizontal locations at the particular depths of interest. The corrections were made by using equations 38 

through 41. The calculated true vertical depths and true 

horizontal positions at 30 m intervals in all wells are 

listed in table 20.

STRATIGRAPHY OF THE INJECTION SHALE

Three rock units present in the Conasauga Group have 

been identified in the gamma-ray logs and cores. From 

top to bottom, they are gray limestone interbedded with
72 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

TABLE 20. -Data on observations and calculations for a deviation survey made at the proposed disposal site, Oak Ridge National Laboratory, Tenn.

[N, north; S, south; E, east; W, west]

Measured 

depth 

(m)

Course 

length MD 

(m)

Vertical 

deviation 

angle, a

Calculated vertical depth Calculated /_. > r horizontal 

^m' Hisplammfflit, )

Z Total ( )

Displacement from surface well center, in meters

Magnetic 

r, bearing,

0

y ^

N S E w

Total

y

N S E

X

W

Injection well

[Total depth after cementing and casing, 338 m]

30.48

60.96

91.44

121.92

152.40

182.88

213.36

243.84 _____ 

274.32

304.80

343.51

30.48 

30.48 

30.48

30.48 

30.48 

30.48

30.48 

30.48 

30.48

30.48 

38.71

1°45' 

4° 

8°

9° 12'

12° 

9°48'

10°36' 

21°30' 

16°

16°36' 

17° 18'

30.47 

30.41 

30.18

30.09 

29.81 

30.04

29.96 

28.36 

29.30

29.21 

36.96

30.47 0.93 

60.88 2.13 

91.06 4.24

121.15 4.87 

150.96 6.34 

181.00 5.19

210.96 5.61 

239.32 11.17 

268.62 8.40

297.83 8.71 

334.79 11.51

N. 30° W. 

N. 40° W. 

N. 55° W.

N. 73° W. 

N. 72° W. 

S. 85° W.

N. 72° W. 

N. 58° W. 

N. 52° W.

N. 35° W. 

N. 33° W.

0.81 

1.63 

2.43

1.42 

1.96

1.73 

5.92 

5.17

7.13 

9.65

0.45

0.47 

1.37 

3.47

4.66 

6.03 

5.17

5.33

9.47 

6.62

4.99 

6.27

0.81 

2.44 

4.87

6.29 

8.25 

7.80

9.53 

15.45 

20.62

27.75 

37.40

0.47 

1.84 

5.31

9.97 

16.00 

21.17

26.50 

35.97 

42.59

47.58 

53.85

Old East-observation well

[Total depth after cementing and casing, 334 m]

30.48

60.96

91.44 _____ 

121.92

152.40

182.88

213.36

243.84 _____ 

274.32

304.80

345.95

30.48 

30.48 

30.48

30.48 

30.48 

30.48

30.48 

30.48 

30.48

30.48 

41.15

0 

2°30' 

4°24'

5°36' 

2°30' 

4°

12° 

16°42'

15°24' 

16°30'

30.48 

30.45 

30.39

30.33 

30.45 

30.41

29.81 

29.19 

28.94

29.39 

39.46

30.48 0 

60.93 1.33 

91.32 2.34

121.65 2.97 

152.10 1.33 

182.51 2.13

212.32 6.34 

241.51 8.76 

270.45 9.57

299.84 8.09 

339.30 11.69

N. 35° E. 

N. 85° E.

S. 55° E. 

S. 30° E. 

S. 80° W.

N. 60° W. 

N. 55° W. 

N. 58° W.

N. 73° W. 

N. 63° W.

0 

1.09 

.20

3.17 

5.02 

5.07

2.37 

5.31

0 

.76 

2.33

1.71 2.44 

1.15 .66 

.37 2.09

5.49 

7.17 

8.12

7.74 

10.41

0 

1.09 

1.29

0.42 

1.57 

1.94

1.23 

6.25 

11.32

13.69 

19.00

0 

.76 

3.09

5.53 

6.19 

4.10

1.39 

8.56 

16.68

24.42 

34.83

New East-observation well

[Total depth after cementing and casing, 347 m]

45.72

76.20

106.68

137.16

167.64 _____ 

198.12

228.60

259.08 _____ 

289.56 _____

320.04

350.52

45.72 

30.48

30.48 

30.48 

30.48 

30.48

30.48 

30.48 

30.48

30.48 

30.48

1°

4°

4° 

3° 

2° 

4°30'

14° 

16° 

16°30'

20° 

14°

45.71 

30.41

30.41 

30.44 

30.46 

30.39

29.57 

29.30 

29.22

28.64 

29.57

45.71 0.80 

76.12 2.13

106.52 2.13 

136.96 1.60 

167.42 1.06 

197.81 2.39

227.38 7.37 

256.68 8.40 

285.91 8.66

314.55 10.42 

344.12 7.37

N. 60° E. 

N. 60° E.

N. 80° E. 

N. 70° E. 

N. 48° W. 

S. 85° W.

N. 80° W. 

N. 80° W. 

N. 64° W.

N. 56° W. 

N. 28° W.

0.40 

1.07

.37 

.55 

.71

1.28 

1.46 

3.79

5.83 

6.51

0.69 

1.84

2.10 

1.50

0.21

0.79 

2.38

7.26 

8.27 

7.78

8.64 

3.46

0.40 

1.47

1.84 

2.39 

3.10 

2.89

4.17 

5.63 

9.42

15.25 

21.76

0.69 

2.53

4.63 

6.13 

5.34 

2.96

4.30 

12.57 

20.35

28.99 

32.45
APPENDIXES: CASE HISTORIES 73

TABLE 20. -Data on observations and calculations for a deviation survey made at the proposed disposal site, Oak Ridge National Laboratory,

Tenn.- Continued

[N, north; S, south; E, east; W, west]

Measured 

depth 

(m)

Course 

length A/D 

(m)

Vertical 

deviation 

angle, at

Calculated vertical depth 

(m)

Z Total

Calculated 

(ml

Displacement from surface well center.

H Sf£

y

N S

r

E W

in meters

Total

y

N S

X

E W

South-observation well

[Total depth after cementing and casing, 338 m]

30.48

60.96

91.44

121.92

152.40

182.88

204.22

207.26

213.36

243.84

274.32

304.80

335.28

364.24

30.48

30.48

30.48

30.48

30.48

30.48

21.34

3.05

6.10

30.48

30.48

30.48

30.48

28.96

3° 30'

5° 48' 

4° 30'

8°36| 

12° 30'

13° 

13°36' 

14°24' 

14°36' 

16°

17°30' 

17° 

15°30'

30.42 

30.32 

30.39

30.14 

29.90 

29.76

20.79 

2.96 

5.91 

29.50 

29.30

29.07 

29.15 

27.91

30.42 

60.75 

91.14

121.28 

151.18 

180.94

201.73 

204.69 

210.60 

240.10 

269.40

298.47 

327.62 

355.53

1.86 

3.08 

2.39

4.56 

5.92 

6.60

4.80 

.72 

1.52 

7.68 

8.40

9.17 

8.91 

7.74

N. 88° 

N. 60° 

N. 65°

N. 65° N. 58° 

N. 58°

N. 62° 

N. 62° 

N. 63° 

N. 65° 

N. 65°

N. 62° 

N. 62° 

N. 62°

W. 

W. 

W.

W. 

W. 

W.

W. 

W. 

W. 

W. 

W.

W. 

W. 

W.

0.06 

1.54 

1.01

1.93 

3.14 

3.50

2.25 

.34 

.69 

3.25 

3.55

4.31 

4.18 

3.63

1.86 

2.67 

2.17

4.13 

5.02 

5.60

4.24 

.63 

1.35 

6.96 

7.61

8.10 

7.87 

6.83

0.06 

1.60 

2.61

4.54 

7.68 

11.18

13.43 

13.77 

14.46 

17.71 

21.26

25.57 

29.75 

33.38

1.86 

4.53 

6.70

10.83 

15.85 

21.45

25.69 

26.32 

27.67 

34.63 

42.24

50.34 

58.21 

65.04

West-observation well

[Total depth after cementing and casing, 342 m]

30.48

60.96

91.44

121.92

152.40

182.88

213.36

243.84

274.32

304.80

335.28

351.13

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

15.85

3°

5°

7°15| 

12° 30'

15° 

18°45' 

19°30'

15°

30.48 

30.44 

30.36

30.48 

29.87 

29.76

29.44 

28.86 

28.73

29.44 

29.87 

15.53

30.48 

60.91 

91.28

121.76 

151.63 

181.38

210.83 

239.69 

268.42

297.86 

327.73 

343.26

0.53 

1.60 

2.66

3.85 

6.08 

6.60

7.89 

9.80 

10.17

7.89 

6.08 

3.16

N. 90° 

S. 80° 

N. 80°

N. 85° 

N. 83° 

N. 82°

N. 72° 

N. 58° 

N. 58°

N. 55° 

N. 38° 

N. 45°

W. 

W. 

W.

W. 

W. 

W.

W. 

W. 

W.

W. 

W. 

W.

0 

0.28 

.46

.34

.74 

.92

2.44 

5.19 

5.39

4.52 

4.79 

2.23

0.53 

1.57 

2.62

3.83 

6.03 

6.53

7.50 

8.31 

8.63

6.46 

3.74 

2.23

0 

0.28 

.18

.52 

1.26 

2.18

4.62 

9.81 

15.20

19.72 

24.51 

26.74

0.53 

2.10

4.72

8.55 

14.58 

21.11

28.61 

36.92 

45.55

52.01 

55.75 

57.98

North-observation well

[Total depth after cementing and casing, 33U m]

30.48

60.96

91.44

121.92

152.40

182.88

213.36

243.84

274.32

304.80

341.38

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

30.48

36.58

3° 30'

5° 18' 

2° 42'

2°36' 

5°36' 

15°30'

23° 

25° 30' 

22° 30'

17°24' 

25° 12'

30.42 

30.35 

30.45

30.45 

30.33 

29.37

28.06 

27.51 

28.16

27.06 

33.10

30.42 

60.77 

91.22

121.67 

152.00 

181.37

209.43 

236.94 

265.10

292.16 

325.26

1.86 

2.82 

1.44

1.38 

2.97 

8.15

11.91 

13.12 

11.66

14.03 

15.58

S. 70° 

S. 55° 

S. 85°

N. 35° 

N. 28° 

N. 35°

N. 37° 

N. 43° 

N. 48°

N. 52° 

N. 50°

E. 

E. 

E.

E. 

W. 

W.

W. 

W. 

W.

W. 

W.

0.64 

1.61 

.13

1.13 

2.63 

6.68

9.51 

9.60

7.80

8.64 

10.01

1.75 

2.31 

1.43

.79 

1.40 

4.67

7.17 

8.95 

8.67

11.06 

11.93

0.64 

2.25 

2.38

1.25 

1.38 

8.06

17.56 

27.16 

34.96

43.60 

53.61

1.75 

4.06 

5.49

6.28 

4.88 

.21

6.96 

15.91

24.58

35.64

47.57
74 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

TABLE 21. -Observed contact between rock units and calculated dip 

and strike at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn.

[Depth of rock contact was observed from gamma-ray logs and adjusted by well deviation logs. 

N, north; S, south; E, east; W, west]

True Horizontal position from Altitude, 

Contact between Measured vertical surface well center, mean 

rock units depth depth in meters sea level

(m) (m) N S W E (m)

Injection well

Rutledge Limestone-Gray shale __ 167 165 8.0 18.5 75 

Gray shale-Rutledge Limestone __ 198 196 8.7 23.8 45

Rutledge Limestone-Pumpkin 

Valley Shale 234 230 13.6 32.9 10

Pumpkin Valley Shale-Rome Sandstone 338 330 34.0 51.6 -89

Old East-observation well

Rutledge Limestone-Gray shale __ 176 175 1.9 4.6 65 

Gray shale-Rutledge Limestone __ 205 205 0.2 0 36

Rutledge Limestone-Pumpkin 

Valley Shale 242 240 5.9 8.1 0

Pumpkin Valley Shale-Rome Sandstone 346 339 19.0 34.8 99

South-observation well

Rutledge Limestone-Gray shale __ 177 175 10.5 20.3 78 

Gray shale-Rutledge Limestone __ 209 206 14.0 26.7 37

Rutledge Limestone-Pumpkin 

Valley Shale 251 247 18.5 36.3 3

Pumpkin Valley Shale-Rome Sandstone 357 348 32.4 63.2 -105

West-observation well

Rutledge Limestone-Gray shale __ 158 157 1.4 15.8 82 

Gray shale-Rutledge Limestone __ 190 188 2.8 22.9 50

Rutledge Limestone-Pumpkin 

Valley Shale 227 223 6.9 32.3 15

Pumpkin Valley Shale-Rome Sandstone 334 326 24.3 55.6 -88

North-observation well

Rutledge Limestone-Gray shale __ 152 151 1.8 4.9 84 

Gray shale-Rutledge Limestone __ 187 185 9.4 0.8 50

Rutledge Limestone-Pumpkin 

Valley Shale 218 213 18.9 8.2 22

Pumpkin Valley Shale-Rome Sandstone 330 318 50.6 44.0 -83

Calculated dip and strike

Contact between rock units Dip Strike

Rutledge Limestone-Gray shale 10°30' N. 51° E.

Gray shale-Rutledge Limestone 9°24' N. 53° E.

Rutledge Limestone-Pumpkin Valley Shale 14°36' N. 70° E.

Pumpkin Valley Shale-Rome Sandstone 13°00' N. 71° E.

calcareous shale, 195 m thick; gray calcareous shale interbedded with less limestone, 34 m thick; and purple or 

gray argillaceous shale (Pumpkin Valley Shale), 100 m 

thick. Underlying the Conasauga Group is the Rome 

Formation. 

The strike and dip of the rock units were determined 

from gamma-ray logs and by the three-point method

described by Lahee (1952, p. 711-714). The calculated 

strikes and dips of all rock units are shown in table 21. 

The calculated average dip of the proposed injection 

shale (Pumpkin Valley Shale) at the proposed site is 13° 

SE. at a strike of N. 70° E.

TENSILE STRENGTH OF THE INJECTION SHALE

Rock samples were selected from cores taken from 

depths ranging from 214 to 360 m and shipped to the 

U.S. Geological Survey's rock mechanics laboratory in 

Denver, Colo., for a determination of the tensile 

strengths of the Pumpkin Valley Shale and the sandstone of the Rome Formation. One hundred and thirtyseven samples were selected, and 87 were used in the 

tensile-strength tests, which were supervised by R. A. 

Farrow of the U.S. Geological Survey. 

Three methods were used in the tests: line load, point 

load, and direct pull. Both the line and point loads were 

applied by using a device described by Reichmuth (1968). 

Direct-pull tests were made both parallel to and normal 

to bedding planes. Samples were cemented by epoxy to 

flat plates designed for the tests and then stressed to 

failure. Test loads, in all tests, were applied with a 

Baldwin Lima Hamilton Universal machine, Model 

FTG1 , at a rate of 0.69 MPa/s for the direct-pull test and 

of 440 N/s for other tests. 

Tensile strengths determined by line load were 

calculated by the following equation:

r=6.37xlO- 3 P/c^, (64) 

where 

T= tensile strength, in megapascals, 

P = load at rock failure, in newtons, 

d= diameter of tested sample, in centimeters, 

and 

h = length of tested sample, in centimeters.

The tensile strength determined by the line-load test is 

the tensile strength parallel to bedding planes. 

Direct-pull tests were made both parallel to and normal to bedding planes. The tensile strength parallel to 

bedding planes was determined by using an apparatus 

specially designed for this test. The apparatus consists 

of a thick-wall tubing 57 mm in inside diameter and 56 

mm long. The tubing was split axially and fitted with 

pulling flanges. Samples were oriented in such a way 

that the direction of pull would be along bedding planes, 

then cemented in place with epoxy. Masking tape, 

placed at the joint where the two halves of the tubing 

joined, prevented epoxy from cementing the tubing. 

Most of the test resulted in epoxy bond failure at

Any use of trade names and trademarks in this publication is for descriptive purposes only 

and does not constitute endorsement by the U.S. Geological Survey.
APPENDIXES: CASE HISTORIES 75

stresses ranging from 3 to 6 MPa, instead of rock 

failure. Direct-pull tests made along the axis of the core 

is not necessarily truly orthogonal to bedding planes 

because of the dip and deviation of the core hole. The 

samples were pulled in a direction 80° to the bedding 

planes. Therefore, the tensile strength normal to bedding planes is probably a few percent less than that 

determined in the laboratory.

The results of point-load tests were disappointing; 

only 9 of 29 samples produced results.

In summary, 83 samples of Pumpkin Valley Shale and 

4 samples of Rome Sandstone were tested. The average 

tensile strength parallel to bedding planes is 12.4 MPa 

for Rome Sandstone and 6.2 MPa for Pumpkin Valley 

Shale. The tensile strength normal to bedding planes 

ranges from 0 to 3.4 MPa for Pumpkin Valley Shale. The 

maximum, minimum, and standard deviation values of 

all tests are shown in table 22.

It is necessary to note that all rock samples used in the 

tests were weakened by expansion resulting from 

removal of confining stresses. The actual in-situ tensile 

strengths in all directions are probably greater than the 

values determined in the laboratory.

TEST INJECTIONS

The test injections were not carried out in the order 

suggested by the U.S. Geological Survey, which is that a 

water injection should be made before a grout injection. 

The ORNL was concerned that a certain amount of 

water would probably be left in the shale after a water 

injection and that water could adversely affect the 

retention of radionuclides during waste injections. The 

ORNL also considered that since the proposed site is only 245 m from the present site, where a water injection

was made in 1967, it would not have been necessary to 

conduct multiple injections, as suggested by the USGS, 

for site evaluations. The USGS objected to the ORNL's 

view for the following reasons:

1. The natural joint system can differ considerably within a distance of a few hundred meters.

2. All formations are already saturated with water to 

some degree, so that a small amount of water left 

by a water injection probably will not seriously affect the system.

3. A water injection not only indicates the degree of 

permeability of the injection zone but also can confirm the test results through a comparison of both 

water- and grout-injection results.

4. Local vertical earth stress can be determined from 

pressure decay of a water injection.

Nevertheless, ORNL decided to make only one grout injection.

After the grout injection, gamma-ray logs indicated 

that only two of the four observation wells, the Southand West-observation wells, had been intercepted by the 

induced fractures. The observed locations of the induced 

fractures correlated well with the calculated orientations. However, no gamma-ray peaks were noted in the 

East-observation well, presumably because the well was 

5 m shallower than the altitude where the induced fractures was calculated to intercept the observation well. 

The North-observation well is near the present fracturing site. A gamma-ray log made before the test grout injection indicates that some induced fractures formed by 

past waste injections at the present site had already intercepted the well. Therefore, unless some new gammaray peaks were formed outside of the depth range where 

the induced fractures formed during past waste injecTABLE 22. -Tensile strength of rocks at proposed site, Oak Ridge National Laboratory, Tenn., determined in the U.S. Geological Survey Denver

Rock Mechanics Laboratory, Colo.

m Tensile strength, in megapascals

.- ;? Arithmetic Maximum Minimum Standard metnou . mean value value deviation

Standard 98-percent confidence limit

error of mean Lower Upper

Rome Sandstone

Line load1 12.6 15.2 10.5 2.3 1.2 10.3 14.9

Pumpkin Valley Shale

Line load2 7.3 12.5 3.6 2.3

Direct pull3 1.6 3.4 .3 1.1

0.4 6.5 8.0 

.4 .9 2.4

Pumpkin Valley Shale, parallel to bedding planes6

6.0 12.5 1.9 3.0 0.4 5.1 6.8

'Four samples were tested, of tensile strength parallel to bedding planes, 

thirty-five samples were tested, of tensile strength parallel to beading planes. 

'Eight samples were tested, of tensile strength normal to bedding planes.

4Tensile strength parallel to bedding planes. Eleven samples were tested: 7 samples resulted in bond failure at stresses ranging from 3.0 to 6.3 MPa; 4 samples failed at 2.4, 2.9, 3.4, and 4.0 

MPa, respectively.

6Twenty-nine samples were tested; only 9 samples had poor results. Average tensile strength parallel to bedding planes is 1.9 MPa. 

6Tensile strength. Average results determined by different methods.
76 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRALILICALLY INDUCED FRACTURES

tions had intercepted the well, there is no way to 

distinguish the previously induced fractures from the 

newly formed fractures. The gamma-ray logs made in 

the North-observation well after the test grout injection 

nearly repeated the one made before the injection. 

Therefore, it cannot be concluded from the gamma-ray 

logs whether or not the injected grout had reached the 

vicinity of the North-observation well during the test 

grout injection.

It is not necessary that all four observation wells 

should be intercepted by the induced fractures; 

however, it is desirable and indeed necessary to have 

more than two of four observation wells yielding a 

positive sign that the induced fracture had reached the 

observation wells, because if only two observation wells 

were intercepted by the grout, it may be interpreted 

that the interception is accidental. Therefore, it was 

concluded that the test grout injection was not sufficient 

to make an affirmative conclusion, and the USGS suggested two more injections-a water and a new grout injection-be made after deepening the East-observation 

well (Sun, 1976). Since then, both the ORNL and the 

USGS have agreed that a water injection was needed.

Because the test grout injection was made before the 

water injection, the test grout injection is discussed first 

in the following paragraphs.

TEST GROUT INJECTION

A test grout injection was made on June 14, 1974. In 

April 1974, the author, using measurements of the 

pressure decay of a water injection made in 1967 at the 

present fracturing site and the shale tensile strength 

estimated on the basis of injections made at West 

Valley, N.Y. (Sun and Mongan, 1974), made calculations 

to predict wellhead breakdown and shut-in pressure for 

the test injection. On the basis of the pressure decay of 

the water injection of 1967, the vertical earth stress at 

the proposed site is estimated to be 1.8 times the value 

of the calculated overburden pressure. For purposes of 

the prediction, the injection depth was assumed to be 

335 m, and the density of shale, 2.7 (deLaguna and 

others, 1968); the vertical stress was then estimated as

(2) (2.7) (335) (9.8 x 10'3)= 17.7 MPa.

On the basis of experience obtained in West Valley, 

N.Y., the tensile strength of shale normal to bedding 

planes and the cohesive stress at fracture tip were 

assumed to be 4 MPa and 2.5 MPa (for/= 0.6) or 1.2 MPa 

(for /=0.3), respectively. The estimated wellhead 

breakdown pressure was calculated as 

wellhead breakdown pressure

= bottom-hole breakdown pressure static head 

in the casing,

= (17.7 + 4) - ((9.8 x 1C"3) x 335),

= 18.4 MPa.

The wellhead shut-in pressure was estimated as the sum 

of overburden pressure and cohesive stress at fracture 

tip less the static pressure in the casing and was equal to 

16 MPa (16.8 MPa for/= 0.6 and 15.6 MPa for/=0.3).

These predicted values were given to the Oak Ridge 

Operations Office, DOE (then U.S. Atomic Energy Commission), by the U.S. Geological Survey, April 29, 1974 

(letter by G. D. DeBuchananne addressed to J. J. 

Schreiber).

The shale was fractured at a 18.3 MPa wellhead 

pressure during slotting on June 12, 1974 (Weeren and 

others, 1974), virtually confirming the predicted value. 

The wellhead shut-in pressure of the grout injection was 

14.5 MPa (table 23), also closely approximately the 

calculated value. As this was the only prediction made so 

far, it may have coincided accidentally and therefore the 

accuracy of the prediction needs further testing.

TABLE 23. -Injection pressure of the test grout injection at 332 m., 

June 14, 1974, at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn.

Time

(min)

30 

AZl

46 

47 

48 - 

50 

55 ___ 

60 - -

62 - - 

65 

68 - 

70 

i O

80 

85 

90 _ ___ __

952 ____________

100 

1053 

no __ _ __ __ 

115 

120 

125 -

130 

1354 _________

140 

145 

150 

155 

ifift

165 

170 

175 

180 _ _ _

185 -

190 

195 

Observed

wellhead

pressure

(MPa)

5.72

1 Q 7Q

17.93

21.37

22.48

20.68

18.62

16.72

21.65

18.89

22.48

18.62

in 01

16.55

16.55

15.31

13.65

13.79

12.55

12.41

13.44

13.38

12.34

12.41

15.17

15.86

16.41

16.55

16.89

"1 /"* C C

16.27

16.20

16.27

16.27

16.27

16.13

16.13

Calculated

Bottom-hole Rate of injection

pressure (m3/sxlO~3 )

(MPa)

8.89

21.10

24.55

25.65

23.86

21.79

19.89

24.82

22.06

25.65

21.79

99 AS

19.72

19.72

18.48

16.82

16.96

15.72

15.58

16.62

16.55

15.51

15.58

18.34

19.03

19.58

19.72

20.06

1Q 79

19.44

19.37

19.44

19.44

19.44

19.31

19.31
APPENDIXES: CASE HISTORIES 77

TABLE 23. -Injection pressure of the test grout 

June 14, 1974, at the proposed disposal site, 

Laboratory, Tenn. -Continued

200

90^

2105

91 x.

990

225

930

OQC

240

94^

OCA

260

98O

9QC

3007

oU5 

01 A

01 C

OOA

ooc

OOA

ooc

340

Q/l C

0,-r

O/» A

370

Q.7C

Q8O

QQC

QQA

QQP.

400

410

415

420

49^

430 -

440 

445 -

450 -

460 

470 -

475 -

480 

485 

490

Observed 

Time wellhead 

(min) pressure 

(MPa)

1 C 1 Q

1 /* OA

1 / .«7O 

1 Q CO

i f* re*

1 4 8Q

 14.34

 14.07

1 A. 9O l*±.^U

 14.48

H I 0

lO.ol

1 C '^c

1 ^ 79

 13.44

17 58

 16.82

1 C QO

1 C QO

1 fi fiQ

1 £, £,Q

1 £, Qfi

1 /* n/*

1 C BO

 16.41

1 C CQ

1 ^ BC.

1 Q AC

1 / .OO

i 7 ci

1 7 Q7

1 / .Li<±

i 7 ci

1 7 7Q

i 7 p. i

.O-L

n Q7

i 7 CQ

18 OK

1 / .I/O

1 7 £,£.

1710

1 Q AC

1 / .t?O

1 fl 9A

-LO.4LI 18 97/ 

1 O Q/*

Calculated 

Bottom-hole 

pressure 

(MPa)

19.31

19.37 

20.13 

21.10 

21.79

19.86 

18.06 

17.51 

17.24 

17.37

17.65 

17.31 

17.79 

18.06 

18.48

20.13 

19.72 

18.89 

16.41 

16.62

20.75 

19.99 

19.86 

19.99 

19.99

19.86 

19.86 

20.13 

20.13 

19.99

19.58 

19.72 

19.86 

19.03 

21.24 

20.82 

20.96 

20.68 

20.55 

20.41

20.68 

20.96 

20.68 

20.68 

20.55

20.75 

21.10 

21.24 

21.10 

20.82

20.82 

20.82 

20.96 

20.27 

20.82

21.24 

21.10 

21.37 

21.44 

22.13

injection at 332 m., 

Oak Ridge National

Rate of injection (m3/sxlO-3)

15.27

16.72 

16.40

16.91 

16.72 

17.22

15.77

17.03 

16.72

16.40 

16.40

17.03 

16.59 

15.96 

16.40 

16.40

16.72 

16.40 

16.59

16.28 

15.46

16.40 

16.40 

16.59

16.40 

16.59

TABLE 23. -Injection pressure of the test grout injection at 332 m., 

June 14, 1974, at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn. - Continued

Observed Calculated 

Time wellhead Bottom-hole Rate of injection 

(min) pressure pressure (m3 /sxlO~3 ) 

(MPa) (MPa)

CAA 1Q31 9948 1577

CAC, iq QQ 93 1 7

CIA 9Q IA 9c 97 19 QQ,

ci c 94 41 97 £8

£.90 9013 9330 1451

coc i q cc, 99 co

530 18.27 21.44 15.01

noc i q 01 99 f^l

540 20.55 23.72 13.56

c/ic IQ 31 99 48

550 18.20 21.37 16.40

555 17.93 21.10

CCA 17Q3 91 10 1609

ccc, 1 7 QQ 9110

rr?A 1 T /* C OA OO 1C 'TO

C.7C 1 7 QQ 9110

580 17.93 21.10 16.40

r o rr -I rj r»C OA OO

CQA 1710 °0 97 1 R OQ

CQC 1C OA IQ ^7

600 16.89 20.06

14.48 7 17.65

a Start injection. 

2 Stop injection. 

'Injection was on and off irregularly. 

4Start injection, most of the time with water. 

''Normal injection started at hour 1310. Before this hour, the injection was run irregularly. 

6 Stop injection for cleaning surge tank window. 

'Instantaneous shut-in pressure.

Interpretation of Injection Data

The injection well was slotted by a hydraulic jet at a 

depth of 332 m measured along the casing (the true injection depth after adjustment for well deviation was 

324 m). The grout injection was started at 0940 hours 

(eastern daylight time) on June 14, 1974, and immediately ran into difficulties. The mixture of the grout 

could not be controlled, and the mixer was jammed with 

solids. The injection was interrupted at irregular intervals. When the injection pump was off, the instantaneous shut-in pressures were 14 MPa wellhead 

pressure or 17 MPa bottom-hole pressure. The normal 

injection was actually started at 1310 hours. The injection was then stopped again for a brief period from 1430 

hours to 1440 hours for cleaning the window of the 

surge tank (hereafter, this stop is referred to as a brief 

pause). A total volume of 370 m3 of grout tagged with 

radioactive tracer 198Au (half-life is 2.7 days) was injected into the Pumpkin Valley Shale. The injection was 

completed at 1940 hours. 

The grout was injected through a string of tubing that 

was placed 3 m above the injection level. The annulus between the casing and tubing was filled with water. Injection pressures were monitored in the annulus at the
78 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

wellhead of the injection well. The bottom-hole pressure 

could be calculated by adding static pressure in the well 

to the observed wellhead pressure. The calculated 

bottom-hole pressure, therefore, excludes the friction 

losses of the grout in the tubing.

Except for the 40-minute period from 1805 hours to 

1845 hours, the injection rate was kept constant at 0.015 

m3/s for the entire injection period. During this 

40-minute period, the injection rate dropped suddenly 

from 0.015 m3/s to 0.010 m3/s; thereafter the injection 

rate increased to 0.015 m3/s. The observed injection 

pressures and injection rates are listed in table 23 and 

graphed in figure 59.

Outside of the 40-minute period, the variation of injection rates was only 0.0006 m3/s, so that the statistical 

random variation of the injection rate cannot be 

separated from the observation error. In essence, the injection rate is equivalent to a single rate, consequently, 

the linear-regression method cannot be used to find the 

relation between the injection pressure and the injection 

rate. However it has been demonstrated that the coefficient of the injection rate in a linear equation can be 

found by using the difference between the injection 

pressure and the instantaneous shut-in pressure (Sun 

and Mongan, 1974).

28

The average injection rate was 0.015 m3/s at an 

average injection pressure of 20.7 MPa. The instantaneous shut-in pressure was 17.7 MPa. The coefficient 

of the injection rate, therefore, is calculated to be 196 

MPa/(m3/s). The linear equation is then established as

P = 17.7 +196 Q. (65)

As determined from the 1967 water-injection pressure 

decay data (deLaguna and others, 1968), the vertical 

stress at the actual injection depth was estimated to be 

15.4 MPa (1.8x2.7x9.8xlO- 3 x324 = 15.4 MPa). The 

bottom-hole breakdown pressure was 21.5 MPa (18.3 

MPa + 9.8 xlO-3 x 324 = 21.5 MPa). Tensile strength 

normal to bedding planes is estimated from the difference between the bottom-hole breakdown pressure 

and the estimated vertical stress, that is, 6.1 MPa 

(21.5-15.4 = 6.1 MPa). Because

fT= instantaneous shut-in pressure-vertical stress, 

= 17.7-15.4, 

= 2.3 MPa, 

therefore

/=0.38, for T= 6.1 MPa.

The tensile strength of shale normal to bedding planes 

as determined by hydraulic fracturing is three times

200 250 300 350 400 

INJECTION TIME (t), IN MINUTES

FIGURE 59. -Pressure plotted against time, the grout injection at 332m, June 14, 1974, at the proposed disposal site, Oak Ridge

National Laboratory, Tenn.
APPENDIXES: CASE HISTORIES 79

greater than the average value found in laboratory 

(table 27); as discussed before, this is probably due to 

stress relaxation when confining stress is removed from 

the core.

Altitude of Induced Fractures

The altitudes of induced fractures were determined by 

gamma-ray logs made in observation wells before and 

after the test grout injection. Repeated logs were made 

to confirm that the logs were reproducible. The logger 

amplifier has 7 sensitivity ranges; namely 0.001, 0.002, 

0.005, 0.01, 0.02, 0.05, and 0.1 milliroentgen per hour 

(mR/hr). The sensitivity to gamma-ray activity decreases as the number of sensitivity range increases. 

For example, at a sensitivity range of 0.001 mR/hr the 

logger is 100 times more sensitive to gamma-ray energy 

than it is at a sensitivity range of 0.1 mR/hr. The 

amplitude of a deflection of a gamma-ray log made with 

a sensitivity range of 0.001 mR/hr is, therefore, 100 

times greater than that indicated on a log of the same 

source made at a sensitivity range of 0.1 mR/hr. 

Therefore, it is necessary to keep the sensitivity range 

in mind when gamma-ray logs are compared.

Past waste grout sheet intercepted by Northobservation well-The location of the North-observation 

well is about 190 m, S. 45° W. from the present injection 

well. Four peaks of gamma-ray activity greater than the 

background activity level for shale were noted from the 

gamma-ray logs made in the North-observation well 

before the test grout injection. The peaks were at depths 

of 242, 246, 271, and 324 m, respectively (fig. 60, table 

24). These peaks indicate that the well has intercepted 

waste grout sheets made during past injections at the 

present injection well north of the observation well.

The strongest gamma-activity among the four peaks 

was at a depth of 271 m measured along the casing (fig. 

60). Adjusted for well deviation, the altitude of this peak 

is at - 27 m (27 m below mean sea level (msl)) (table 24), 

and if the calculated dip and strike (13° SE., and N. 70° 

E.) of the Pumpkin Valley Shale at the proposed site 

were used, then the bedding-plane fractures indicated 

by this peak would intercept the present injection well at 

an altitude of 16 m msl. Most of the wastes were injected at altitudes ranging from -12 to -18 m msl 

(table 11). Therefore, it can be concluded that this 

gamma-ray peak results from past waste injections 

made at the present injection well.

The second strongest gamma-activity peak was 

observed at an altitude of 4 m msl. On the basis of the 

same dip and strike the altitude at which the fracture indicated by this second peak may be projected to intercept the present injection well at 9 m msl. The 

altitudes of - 0.5 and 74 m msl observed for the other

TABLE 24. -Waste, grout sheet intercepted by the, North-observation 

well from past waste injections made at the present fracturing site. 

Oak Ridge National Laboratory, Tenn.

[Interpreted from gamma-ray logs made in the North-observation well at the proposed 

disposal site before the test'grout injection, June 14, 1974. N, north; S, south; W, west; E, 

east]

Depth measured 

along casing 

(m)

OAO Q

O A f* r\9

971 03

ooo 7

Vertical depth1 

(m)

235.5 

238.9 

262.0 

309.3

Altitude 

mean sea level 

(m)

0.5

-3.9 

-27.0 

-74.2

Horizontal position from surface 

well center, in meters

N

26.7 

27.7 

34.1 

48.8

s w

15.5 

16.5 

23.6 

41.8

E

'Measured depth adjusted by deviation survey. 

2 Second strongest gamma-ray activity peak. 

"Strongest gamma-ray activity peak.

two gamma-ray-activity peaks when projected to the 

present injection well are either 24 m above or 21 m 

below the past waste injection altitude. Table 11 indicates that all wastes were injected between 12 to

- 47 m msl; therefore, it may be concluded that some 

waste grout has probably migrated 20 m above or below 

the injection level during past injections over a distance 

at least 200 m from the injection site.

Grout sheets produced by test grout injection. -A comparison of gamma-ray logs made in the Northobservation well before and after the test grout injection 

shows no significant change in gamma-ray activity at 

any depth. Two of the logs obtained after the test grout 

injection were made by using sensitivity ranges of 0.002 

mR/hr and 0.01 mR/hr, respectively. If the gamma-ray 

activity shown by the log made using a sensitivity range 

of 0.002 mR/hr is reduced by a factor of 5, then the 

shape and the relative quantity of the gamma-ray activity indicated by the log would be similar to that recorded 

on the log made using a sensitivity range of 0.01 mR/hr. 

This indicates the reproducibility of the logs. If the log 

made using a sensitivity range of 0.002 mR/hr is reduced 

by a factor of 2.5, the activity recorded on the log would 

be very close to that recorded on the log made in the 

North-observation well before the test grout injection at 

a sensitivity of 0.005 mR/hr. Comparison of the logs indicates that no additional grout sheets have intercepted 

the North-observation well since the test grout injection. The probable altitude at which the Northobservation well would have been intercepted by the 

bedding-plane fractures induced by the test grout injection at the proposed disposal site was calculated to be

 67 m msl. A gamma-ray activity peak produced by past 

waste injections is at - 74 m msl, or about 7 m below the 

calculated altitude at which the induced fractures would 

be expected to have intercepted the well. Therefore, it 

cannot be determined whether the injected grout did not 

reach the vicinity of the North-observation well or 

whether the injected grout did reach the observation well
80 SI

238-

240- 

242- 

244

246- 

248-

250

252- 

254- 

256-

'BSURFACE DISPOSAL OF RADIOACTIVE WAS

GAMMA ACTIVITY INCREASES -

(

*

V

^~~

\

1

 

Log of 1- 

(Before c 

Amplifie 

0.02 m/?,

 -- 

7-74

ementing) 

- Range 

h

GAMMA ACTIVITY INCREASES

Log of 4-10-74 

(After cementing) 

Amplifier Range . 

0.005 mR/h 

Time constant 3 s

780

790

800 

810 

820 

830 

840 tL

l_LJ

870 E

nf i 

880 £ 

890

900

910

1050

1060

1070 

BEFORE TEST GROUT INJECTION BEFORE TEST GROUT INJECTION

NORTH-OBSERVATION WELL

FIGURE 60. Gamma-ray activities observed in the North-observation well along the casing axis before the test grout injection, June 14,1974, at

the proposed disposal site, Oak Ridge National Laboratory, Tenn.

O£ U

322-

324-

326-

^ >

£

<^

i

but followed weak planes between the older waste grout 

sheets and shale at -74 m msl; in the latter case, the 

gamma-ray activity produced by the tracer in the test 

grout injection could not be differentiated from that produced by older waste injections.

Six gamma-ray activity peaks were noted after the 

test grout injection on a gamma-ray log made in the 

West-observation well at depths ranging from 328 to 

332 m measured along the casing (table 25, and fig. 61).

Grout sheets were formed within a 5-m zone. The projected horizontal position of the six gamma-ray activity 

peaks and the altitudes of the grout sheets were 

calculated and are shown in table 25. The horizontal 

distance between the injection depth and the observed 

gamma-ray activity peaks was determined along a line 

perpendicular to the calculated strike of the Pumpkin 

Valley Shale and was estimated to be 12 m (fig. 62). The 

injection depth was - 84 m msl. If bedding-plane frac-
APPENDIXES: CASE HISTORIES 81

GAMMA ACTIVITY INCREASES GAMMA ACTIVITY INCREASES

318 _ 

3?0-

322- 

324 H

326^ 

328- 

330- 

332- 

334- 

336- 

338- 

340- 

342- 

344-

<;

<

<

|

{

|

t

> 

:r>

>

Log of 1-14-74 

(Before Cementing) 

Amplifier Range 

0.005 mR/ h

1040

1050

1060

1070

1080

Log of 6-15-74 

Amplifier Range 

0.1 mR/h

1090

BEFORE TEST GROUT INJECTION AFTER TEST GROUT INJECTION

WEST-OBSERVATION WELL

FIGURE 61. -Gamma-ray activities observed in the West-observation well along the casing axis, before and after the test grout injection, June 14, 1974, at the proposed disposal site, Oak Ridge National Laboratory, Tenn.

TABLE 25. -Grout sheet from the test grout injection at 332 m, June 

14, 1974, intercepting observation wells at the proposed disposal 

site, Oak Ridge National Laboratory, Tenn.

[The injection altitude was 83.7 m nisi. N, north; S, south; W, west; E, east]

Depth measured 

ng casing 

(m)

epth 

alon

Vertical Altitude Horizontal position from surface

depth1 mean sea level well center, in meters

(m) (m) N S W E

New East-observation well

341.1 335.0 19.7 31.4

South-observation well

349.0 

349.6 

 340.8

 341.4

 341.7 -97.8 

-98.1

31.5 

31.5 

31.1

61.4 

61.6 

61.7

West-observation well

qoo A

OQA 1

330.4 

QQI n

OQ1 Q

QQ1 Q

QOA Q

9,99 4

qoo 7

QOO Q

QOO £

 324.1

81 8

-83.9 

-84.2

84 8

-85.1

-85.7

23.3

23.7 

23.7 

23.8 

23.9 

24.0

54.9 

55.1 

55.2 

55.2 

55.3 

55.4

'Measured depth adjusted by deviation survey.

tures were induced near the West-observation well, then 

the altitude at which they would intercept the well can 

be estimated by using the calculated dip and strike of the 

shale. The calculation is

fracture altitude = -84 + 12 tan!3°,

= - 81 m msl.

This calculated altitude is close to the observed altitude 

of the gamma-ray activity peaks, which are from - 82 to 

-86m msl (table 25).

Three gamma-ray activity peaks were noted on a 

gamma-ray log made in the South-observation well at 

depths between 349 m and 350 m measured along the 

casing (table 25, fig. 63). The altitudes of the peaks, 

after adjustment for well deviation, are shown in table 

25. The horizontal distance between the injection 

altitude and the altitudes of the gamma-ray activity 

peaks in the direction of the dip was estimated to be 56 

m (fig. 62). Therefore, the altitudes at which the South-
82 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRA ULICALLY INDUCED FRACTURES

N17300

NI7200

N17100

NI7000

g N16900 

o

N16800

N16700

N16600

N16500

NI6400

N16300

N16200

Location of well at surface 

98 A. Position of interception of grout sheet 

at wells; number indicates altitude, 

m.s.l.in meters

80 O Position of bottom of East- and North - 

observation wells; number indicates 

altitude,m.s.i. in meters 

Position of point of injection; number 

indicates altitude m.s.l.in meters 

1~3 Dip and strike of Pumpkin Valley Shale at proposed site;

determined from gamma-ray logs; dip in degrees 

tr~ Horizontal distance along a line perpendicular 

t_ to strike, in meters

-84

Joy well

Injection well at

present fracturing

facility site

East-observation wel

5° _oo Injection well at 

/ proposed site

New East-observation 

well

0 10 20 30 METERS

South-observation 

well

E27700 E27800 E27900 E28000 E28100 E28200 E28300 E28400 E28500 E28600 E28700 

OAK RIDGE NATIONAL LABORATORY COORDINATES

FIGURE 62.-Location of point of injection and altitudes of gamma-ray peaks observed in observation wells 

after the test grout injection, June 14,1974, at the proposed disposal site, Oak Ridge National Laboratory, 

Tenn.

observation well would be intercepted by the induced 

bedding-plane fractures is calculated as

fracture altitude = -84-56 tan!3°, 

= - 97 m msl,

which is close to the observed peak altitudes, that is, 

-97m and - 98 m msl, respectively.

No significant change in gamma-ray activity was 

registered on logs made in the East-observation well 

before and after the grout injection. The projected 

horizontal distance along the dip between bottom of the 

East-observation well and the injection altitude was 

estimated to be 43 m (fig. 62). The altitude at which the

East-observation well would be intercepted by the induced bedding-plane fractures is calculated as

fracture altitude = -84-43 tan!3°, 

= - 94 m msl.

The depth corresponding to this altitude measured along 

the casing adjustesd by well deviation was 340 m. The 

total drilling depth was 344 m; however, after casing 

and cementing the well depth was reduced to 334 m, 

which is 6 m shallower than the calculated altitude 

where the East-observation well would be intercepted 

by the induced fractures. The gamma-ray log indicates 

two possibilities: (1) induced fractures intercept the well
GAMMA ACTIVITY INCREASES

APPENDIXES: CASE HISTORIES

GAMMA ACTIVITY INCREASES-*-

83

GAMMA ACTIVITY INCREASES'

340- 

342-

2 344-

5 

^ 346-

3C

S 348- 

350- 

352-

2

<

>

!

, Log of 1-8-74 

[, (Before cementing) 

| Amplifier Range 

^ 0.005 mP

£

/h

1

 * ~^

<=3

<^ ^

 ^: -s

>

- Log of 4-17-74 

 -j= (After cementing) 

Amplifier Range 

0.002 

>. Time c

~=» 

^* 

 Botto

nR/h 

onstant 5s

n of well

k

fLog of 6-17-74 

Amplifier Range 

0.02 mR/h

~~y Time con

t- 

_______5==^

 Bottom of

stant 3s

 

_-< 

well

: 

BEFORE TEST GROUT INJECTION BEFORE TEST GROUT INJECTION

SOUTH-OBSERVATION WELL

1110

1120

1130

1140

1150

1160

AFTER TEST GROUT INJECTION

FIGURE 63.-Gamma-ray activities observed in the South-observation well along the casing axis, before and after the test 

injection, June 14,1974, at the proposed disposal site, Oak Ridge National Laboratory, Tenn.

grout

beneath the well bottom or (2) no grout sheets reached 

the well.

Before the water injection made on October 30, 1975, 

gamma-ray logs were made again in all four observation 

wells in September 1975, 87 days after the test grout injection. All logs reproduced the pattern of the logs made 

immediately after the test grout injection. Gamma-ray 

activity peaks were still observed distinctly at the zones 

discussed, but these peaks could not have been due to 

the tracer, 198Au, which has a half life of 2.7 days. After 

32 half lives (87 days after the injection) the tracer 

should have decayed to below the detection limits. As explained by the ORNL personnel several hundred gallons 

of contaminated waste pit water containing 137Cs and 

90Sr were injected during the test grout injection (J. A. 

Lenhard, written commun., Nov. 16,1976), and thus the 

gamma-ray peaks observed on logs resulted from 137Cs 

not from tracer 198Au.

In 1976, a new East-observation well was drilled by 

the ORNL 30 m south-west of the old East-observation 

well. A single gamma-ray activity peak was noted on a 

gamma-ray log made in the new East-observation well 

at a depth of 341 m measured along the casing (fig. 64). 

Adjusted for well deviation, the altitude at which the 

observation well was intercepted by the induced fracture was calculated to be -94 m msl. The horizontal 

distance along the dip between the injection altitude and 

the altitude for the gamma-ray peak was estimated to be 

65 m (fig. 62). The projected altitude at which the new 

East-observation well could be intercepted by the test 

injection grout sheet is calculated as

fracture altitude = 84 - 50 tan!3°, 

= 96 m msl,

which is close to the observed altitude of - 94 m msl.

Thus, three of the four observation wells have been intercepted by the grout sheets produced by the test grout 

injection near the calculated altitudes, and it is concluded that bedding-plane fractures have been induced by 

the test grout injection.

TEST WATER INJECTION

A test water injection was made on October 30, 1975, 

through the same slot as the test grout injection made 

on June 14,1974. The scheduled injection volume was 378 

m3 of water tagged with 25 Ci of 198Au and 25 Ci of 

199Au. The injection rates were scheduled to start at 

0.003 m3/s, increase to 0.006 m3/s, then 0.013 m3/s, and 

finally increase to the full capacity of the injection pump 

(0.017 m3/s). The first three steps would last two hours 

for each step. Unfortunately one of the two injection 

pumps broke down after about one hour of injection at 

the pump's highest capacity, and the injection was 

stopped shortly thereafter. The final injection volume 

was 209 m3 tagged with half the prepared tracers. 

Pressure decay was observed for about 18 days after the 

injection. The injection and pressure-decay data are 

shown in tables 26 and 27, respectively. The linear 

regression equation of P and Q established from the injection data is given by

= 20 + 197Q. (66)

If Q = 0; then P = 20 MPa, which closely correlates with 

the observed shut-in bottom-hole pressure, 19.9 MPa 

(table 27).

The earth stress normal to the bedding-plane fractures determined from pressure decay is 16 MPa (fig. 

65), corroborating the previously estimated vertical 

stress of 15.4 MPa, determined from the 1967 water
84 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

TABLE 26. -Injection pressure of the test water injection at 332 m, 

Oct. 30, 1975, at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn.

1

3

5

6

7

91 

10 1392 

140

142

143

146

147

148

1503 

155

160

165

170

175 .

180 .

185 .

190 .

195

200 .

205 .

210 .

215 .

220

225 .

230 .

235 .

240

245

250 _

255 .

256 _

257 _

258 .

259

260 .

265 .

270 .

275 .

280 .

285 .

290 .

295 .

298 _

299 .

300 _

301 _

302 _

303 _

304 _

305 _

306 _

307 _

308

Ow<y

310

311 -

312

313 __

rji- Observed wellhead 

, ) pressure 

(rmn> (MPa)

13.17

13.44

13.72

12.93

11.93

11.10

10.69

11.76

13.20

14.62

14.82

15.00

15.10

15.24

15.27

15.51

15.79

15.96

16.10

16.20

16.31

16.48

16.51

16.58

16.69

16.79

16.86

16.93

17.00

17.06

17.10

17.10

17.10

17.10

17.00

18.13

18.44

18.62

19.13

19.31

19.44

19.86

20.03

20.24

on 07

20.42

20.42

20.34

20.27

20.24

20.24

20.24

19.44

19.20

19.00

18.79

18.62

18.48

18.31

lo.l 1

18.03

17.93

17.83

______ 17.72

Calculated bottom- D , - . . . hole oressure Rate of lnJectlon 

(MPa) (m»/BxlO«)

16.34 

16.62 

16.89 

16.10 

15.10 

14.27 0 

13.86 

14.93 0 

16.38 

17.79 1.89 

18.00 

18.17 

18.27 

18.41

18.44 

18.68 

18.96 

19.13 

19.27

19.37 

19.48 

19.65 

19.68 1.89 

19.75 2.40

19.86 

19.96 

20.08 

20.10 2.40 

20.17 2.65

20.24 

20.27 2.65 

20.27 2.84 

20.27 

20.27 2.84

20.17 2.65 

21.30 5.65 

21.62 

21.79 

22.30 

22.48

22.61 5.65 

23.03 8.45 

23.20 

23.41

23.55 

23.59 

23.59 

23.51 

23.44 

23.41

23.41 

23.41 8.45 

22.61 5.43 

22.37 

22.17 

21.96 

21.79 

21.65 

21.48 

21.34

21.20 

21.10 

21.00 

20.89

TABLE 26. -Injection pressure of the test water injection at 332 m, 

Oct. 30, 1975, at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn. -Continued

m. Observed wellhead

, . , pressure (mm) ^(Mpa)

315 17.48

318 18.27

319 18.55

320 18.86

325 19.41

330 19.62

335 19.79

340 19.89

345 19.89

350 19.87

355 19.82

360 19.79

365 19.75

370 19.68

372 19.79

373 19.82

374 19.86

375 19.89

376 19.93

377 19 99

378 20.03

379 20.06

380 20.11

385 20.13

390 20.10

395 20.06

400 19.96

405 19.86

410 19.75

415 19.65

AOf) 1 Q CO

425 19.51

430 19.41

435 19.20

450 19.06

A CC 1 Q AO

460 18.96

463 19.13

AC.A 1 Q 1 C

465 19.17

470 19.21

475 19.20

480 19.17

485 _______ 19.03 

490 18.96

495 18.87

5004 18.80

503 18.20

504 18.10

505 18.13

506 18.10

510 18.00

ci c 17 07

con i 7 77

525 17.66

5305 17.58

CQC 1 7 AQ

540 17.44

CAC 1 7 Q7

5506 17.34

Calculated bottomhole pressure 

(MPa)

20.65 

21.44 

21.72

22.03 

22.58 

22.79 

22.96 

23.06 

23.06

23.04 

22.99 

22.96 

22.93 

22.86 

22.96 

22.99 

23.03

23.06 

23.10 

23.17 

23.20 

23.24 

23.28 

23.30 

23.27 

23.24

23.13 

23.03 

22.93 

22.82 

22.77 

22.68 

22.58 

22.37

22.24 

22.20 

22.13 

22.30 

22.32 

22.34 

22.38

22.37 

22.34 

22.20 

22.13 

22.04

21.97 

21.37 

21.27 

21.30 

21.27 

21.17 

21.04 

20.95

20.84 

20.75 

20.66 

20.62 

20.55 

20.51

Rate of injection 

(rrWsxlO-3 )

5.43 

6.62

6.62 

7.95

7.95 

7.59

7.59 

9.90

9.90 

13.25

13.25

12.74 

12.74 

13.25

13.25

16.78 

16.78 

16.40

16.40 

9.21

'Shut down for repairing leaks. 

2Pressure gage was out of order. 

3Start injection of tracers. 

40ne pump was out of order. 

5 Stop injection of tracers. 

6End injection.
APPENDIXES: CASE HISTORIES 85

TABLE 27. -Pressure decay of the test water injection at 332 m, Oct. 

30, 1975, at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn.

Time since end

of injection (min)

2

5

10

15

20

25

30

35

40

45

50

55

60

65

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

225

240 ______

255

270 _______

285

300

315

330

860

890

920

970

1,035

1,140

1,200

1,260

1,430

1,675

1,930

2,160

2,400

2,640

2,880

3,120

3,360

3,600

3,850

4,105

4,315

4,560

4,800

5,040

5,335

5,490

5,760

Observed well-head

pressure (MPa)

16.72

16.44

15.93

15.62

15.31

15.07

14.86

14.65

14.48

14.31

._ 14.17

14.03

13.89

13.79

13.69

13.48

13.27

13.12

13.17

12.81

12.67

12.63

12.45

12.34

12.22

12.12

12.03

11.93

11.86

11.72

_ 11.62

11.51

_ 11.41

11.31

11.20

11.14

11.03

9.29

9.23

9.19

9.11

9.01

8.81

8.70

8.61

8.38

8.07

7.81

7.58

7.47

7.28

7.15

7.01

6.87

6.72

6.67

6.55

6.50

6.38

6.31

6.22

6.17

6.12

6.05

Calculated bottomhole pressure (MPa)

19.89

19.62

19.10

18.79

18.48

18.24

18.03

17.82

17.65

17.48

17.34

17.20

17.06

16.96

16.86

16.65

16.44

16.29

16.11

15.98

15.84

15.80

15.62

15.51

15.39

15.29

15.20

15.10

15.03

14.89

14.79

14.69

14.58

14.48

14.38

14.31

14.20

12.46

12.40

12.36

12.28

12.18

11.98

11.87

11.78

11.55

11.24

10.98

10.76

10.65

10.45

10.32

10.18

10.05

9.89

9.85

9.72

9.67

9.55

9.48

9.39

9.34

9.29

9.22

(P-Po)

(MPa)

16.77

16.50

15.98

15.67

15.36

15.12

14.91

14.70

14.53

14.36

14.22

14.08

13.94

13.84

13.74

13.53

13.32

13.17

12.99

12.86

12.72

12.68

12.50

12.39

12.27

12.17

12.08

11.98

11.91

11.77

11.67

U C7

11.46

11.36

11.26

11.19

11.08

9.34

9.28

9.24

9 Ifi

9.06

8.86

8.74

8.66

8.43

8.12

7.86

7.64

7.53

7.33

7.20

7.06

6.93

6.77

6.73

6.60

6.55

6.43

6.36

6.27

6.22

6.17

6.10

TABLE 27. -Pressure decay of the test water injection at 332 m, Oct. 

30, 1975, at the proposed disposal site, Oak Ridge National 

Laboratory, Tenn. - Continued

Time since end Observed well-head Calculated bottomof injection (min) pressure (MPa) hole pressure (MPa) (MPa)

6,000

6,240

6,480

6,720

6,960

7,200

7,440

7,650

7,920

8,400

8,700

9,180

9,625

10,140

10,620

11,320

11,580

12,080

12,540

13,020

13,500

14,460

15,360

15,655

16,795

17,080

18,225

18,555

19,680 __. 

19,972 ___ 

21,100 __. 

21,420 __. 

22,600 __. 

24,030 ___ 

25,448 ___ 

25,692 __.

6.00

5.90

5.83

5.83

5.76

5.72

5.67

5.62

5.59

5.48

5.45

5.37

5.32

5.24

5.17

5.09

5.03

5.00

4.96

4.90

4.84

4,76

4.69

4.67

4.60

4.56

4.48

4.47

4.38

4.37

4.30

4.28

4.21

4.14

4.08

4.05

9.17

9.07

9.01

9.01

8.94

8.89

8.84

8.79

8.76

8.65

8.62

8.54

8.49

8.41

8.34

8.26

8.20

8.17

8.14

8.07

8.01

7.93

7.86

7.84

7.77

7.74

7.65

7.64

7.55

7.54

7.47

7.45

7.38

7.31

7.25

7.22

6.05

5.95

5.89

5.89

5.82

5.77

5.72

5.67

5.64

5.53

5.50

5.42

5.37

5.29

5.22

5.14

5.09

5.05

5.02

4.95

4.89

4.81

4.74

4.72

4.65

4.62

4.53

4.52

4.43

4.42

4.35

4.33

4.26

4.19

4.13

4.10

Note: Static ground-water pressure at injection level, P0 = 3.12 MPa.

injection at the present disposal site. The permeability 

of the injected shale, indicated by the pressure decay 

data, is low, as expected. If the tensile strength of the 

shale is assumed to be 6.1 MPa, then/= 0.66.

A comparison of gamma-ray logs made before and 

after the water injection shows no indication that any of 

the four observation wells are intercepted by the induced fractures at any depth. The water injection was 

made at the same depth and through the same slot 

through which the test grout injection was made. It was 

anticipated that the injected water would probably flow 

along weak planes induced by the test grout injection 

between the shale and the previously formed grout 

sheets or that, in other words, a series of thin fractures 

would be induced in the grout sheet zone. Because the 

grout sheets are contaminated by 137Cs, which produces 

higher gamma-ray energy than that produced by the 

tracers in the injection water, it is not surprising that 

none of the gamma-ray logs made in the observation 

wells after the water injection show evidence that frac-
86 SUBSURFACE DISPOSAL OF RADIOACTIVE WASTES IN HYDRAULICALLY INDUCED FRACTURES

GAMMA ACTIVITY INCREASES + 

CO

DC 

LLJ

330-

332-

334-

336-

338-

Log of 10-17-76 

Amplifier Range 

0.002 mR/h 

Time constant 2 s

Bottom of well i

1080

1090

1100

m

1110 z

fc 340 H

- 1120

1130

346 -

1140

AFTER TEST GROUT INJECTION

NEW EAST-OBSERVATION WELL

FIGURE 64. -Gamma-ray activities observed in the new East-observation well along the casing axis, 85 days after the test grout injection, June

14, 1974, at the proposed disposal site, Oak Ridge National Laboratory, Tenn.

tures induced by the water injection intercepted the 

wells.

However, the water-injection pressure data confirm 

the conclusions reached from data gathered during the 

test grout injection.

POTENTIAL FOR THE EXHUMATION OF WASTES

The injected wastes become an integral part of the 

shale after the solidification of the grout and so remain

as long as the shale is not subject to erosion. Therefore, 

consideration should be given to the factors involved in 

eroding and possibly exposing the injected wastes.

Over 99 percent of radionuclides contained in the 

wastes generated at the ORNL are 90Sr and 137Cs (table 

11), which have half-lives of 28 and 30 years, respectively. Within 1,000 years, these radionuclides will decay to 

where the radiation-emission levels are innocuous.

On the basis of the dissolved and suspended sediment
APPENDIXES: CASE HISTORIES 87

10 2

10'

10'

Pn =3.12 MPa

13MPa

I i . i i i

10° 10 2 

TIME AFTER END OF INJECTION (t), IN MINUTES

103

FIGURE 65.-Pressure decay plotted against time, the water injection at 332 m, Oct. 30, 1975, at the proposed disposal site, Oak

Ridge National Laboratory, Tenn.

loads of streams, the climate, topographic, and geologic 

type, and the size of the drainage areas, Schumm (1963) 

concluded that denudation rates are an exponential 

function of the drainage-basin relief and length ratio. 

The mathematical form of this relationship is

log D = 26.966 #-2.2398, (67)

where

D = denudation, in meters per 1,000 years, and 

H= ratio of basin relief to length.

The relief-to-length ratio of Melton Branch 

basin (the injection site) is taken as 0.031 

((365.8-231.6)/4328 = 0.031); the denudation rate of the 

basin is then estimated to be 0.04 m per 1,000 years. 

Wastes are to be injected into Pumpkin Valley Shale, 

which is about 213 m below the surface. Using the 

estimated denudation rate, it would take 5.4 x 106 years 

to expose the wastes injected in the uppermost part of 

the Pumpkin Valley Shale by erosion. Even if the unlikely erosion rate of 1 m per 1,000 years is assumed, which

is the average maximum erosion rate for young mountain ranges of high relief, such as the Alps (Schumm, 

1963), it would still take 2 x 105 years to expose the grout 

sheets. This time interval would be sufficient for radionuclides contained in the wastes to decay to harmless 

radiation-emission levels, and thus the possibility of 

their contaminating the biosphere by erosion processes 

is negligible.

SUMMARY

On the basis of injection data, gamma-ray logs, and 

estimation of erosion rate, it is concluded that the 

hydraulic-fracturing disposal sites at the ORNL are safe 

for the purpose of disposing radioactive wastes 

generated at the ORNL by grout injections in shale. 

However, as a precaution, more monitoring observation 

wells need to be constructed in areas not expected to be 

reached by waste-grout sheet and in the formation lying 

above the injection zone, in order to increase confidence 

that the injected wastes are isolated and restricted to a 

known horizon.