NUREG/CR-4736

PNL-5999

Combustion Aerosols Formed

During Burning of. Radioactively

Contaminated Materials - .Experimental Results

Manuscript Completed: February 1987

Date Published: March 1987

• Prepared by

M. A. Halverson, M. Y. Ballinger, G. W. Dennis

Pacific Northwest Laboratory

Richland, WA 99352

Prepared for

Division -of Fuel Cycle and Material Safety

Office of Nuclear Material Safety and Safeguards

U.S. Nuclear Regulatory Commission

Washington, DC 20555

NRC FIN B2481

EXECUTIVE SUMMARY

Pacific Northwest Laboratory conducted two series of experiments to measure aerosols generated by burning contaminated combustibles. Data from these

experiments will replace or expand models currently in FIRIN, a fire compartment computer code that predicts source term releases from fires in nuclear

fuel cycle facilities.

Four materials were burned in the combustible solid experiments: polychloroprene (PC), polystyrene (PS), polymethylmethacrylate (PMMA), and cellulose. In two runs a combination of fuels was burned. Contaminant form,

configuration, and concentration; heat flux; percent oxygen air flow; and type

of ignition were varied in the experiments. The highest releases, up to

4.5 wt% uranium, came from PMMA with powder contaminant. Cellulose burns had

the lowest fraction releases, approximately 0.01 wt%. Most of the uranium

released from PMMA and PS burns came off during the melting and bubbling preignition, stage before the material burned. Uranium release rates from polychloroprene correlate well with smoke release rates. Cellulose seemed to give

off uranium at a steady rate 'throughout the burn. Uranium release rates correlated well with mass loss rate for that material. One particle size distribution was measured for each of the fuels. For cellulosic material, more than

97% of the particles carrying uranium were less than 10 iim. However, only 16%

of the particles less than 10 ýim carried uranium for PC. Sizes of radioactive

particles from burning contaminated PS and PMMA were between the two extremes.

A mixture of 30% tributyl phosphate in kerosene was burned in the contaminated combustible liquid experiments. The fuel was combined with nitric acid

in the following four configurations:

1. acid/fuel with uranium

2. acid with fission products/fuel with uranium

3. acid with fission products and uranium/fuel

4. acid with fission products and uranium/fuel with uranium.

Weight percent of uranium airborne ranged from 0.2 to 7.1, with the highest releases coming from a burn of pure organic fuel over acid with fission

products and uranium. In all configurations, the mass rate of uranium airborne

seemed to be proportional to the mass rate of smoke airborne. Fission product

analysis failed to provi.de accurate data, so it is not included in this report.

One particle size distribution was measured. An aerodynamic mass median diameter of 0.6 pm was calculated for airborne particles containing uranium from

burning contaminated combustible liquids.

iii

CONTENTS

EXECUTIVE SUMMARY LPO S............................. . . . . ................. i3

INTRODUCTION SOLIDEXPERMENT .... ............ ........... 5

EXPERIMENTAL PROCEDURESn Paamte.....o..... ........... 3........... 3

AP PAR AT U S• . 3

COMBUSTIBLE SOLID EXPERIMENTS .... ........ .... 5

Experimental Parameters ...................... • 5,

Sample Preparation .............. . ....... .............. 7

COMBUSTIBLE LIQUID EXPERIMENTS ............. ....... 12

ANALYSIS OF FILTER SAMPLES FOR URANIUM AND FISSION PRODUCTS ......... 14

RESULTS" ... . . .• . . . . . . .. . . . . . . .. . . . 17

COMBUSTIBLE SOLIDS -............. ................. ...... . ..... . 18

Polychloroprene ................ ........ . ... . ................. . 18

Polysty rene .... o..o ....... o .. .... o....20

Polymethylmethacryl ate ............... . .......... 22

Cellulose .... 0*0 ... .* .... 25

Mixed Fuels .. . . . . . . . . .o. . . I. . . ..4. . . . . .o 27

COMBUSTIBLE LIQUIDS ... .0..... .. ..... 0....0.... ............ 0...... .. *. 28

Pure-Acid/Organic with Uranium...............o.......o.......... 28

,Acid with Fission Products/Organic with Uranium ................ 29"

Acid with Fission Products and Uranium/Pure Organic ............ 29

Acid with Fission Products and Uranium/Organic

with Uranium ........................... o..........o............... 30

Fission Product Release ..... ..... ...... . .................... 30

.SIZE DISTRIBUTION OF AEROSOLS ................ oo ....... ...... 30

V
REFERENCES A PEE ARR ROBNGOANT MU..".BLE 33

APPENDIX A -PERCENT AIRBORNE FROM BURNING CONTAMINANT COMBUSTIBLES ...... ý. A.1

vi
FIGURES

1 CARE Combustion Apparatus ................... ........ ........ 4

.2 Results from Burning Contaminated Combustibles ..................... 0. 17

3 Fractional Release of Uranium from Contaminated Polychloroprene .. .. .. " .... 19

4 Fractional Release of Uranium from Polychloroprene

Contaminated With Powder ...... ........... s. ................... 20

5 Fractional Release of Uranium from Polystyrene Contaminated with Liquid • -21

6 Fractional Release of Uranium from.Contaminated PMMA ................. 23

7 Fractional Release of Uranium from PMMA Contaminated with

DUO Powder ". .. :....... ........ 10. 000 ... 24

8 Fractional Release of Uranium from Contaminated Cellulose .. ....... 25

9 Fractional Release of Uranium from Cellulose

Contaminated with Powder '................... ....... ......... 26

TABLES

1 Contaminant Combustible Solid Experiments ....... .................. 6

2 DUO Particle Size Distribution o..o.ooo.o.o..o ..... 9. 0. 0-0. 6 8

3 Contaminated Combustible Liquid Experiments ..... ,.................... 13

4 Size of Aerosols fromBurning Contaminated Combustibles ............... 31

A.1 Results from Burning Contaminated Polychloroprene (PC) ..... .... .... A.1

A.2 Results from Burning Contaminated Polystyrene (PS) .................. A.2

A.3 Results from Burning Contaminated Polymethylmethacrylate (PMMA) ..... A.3

A.4 Results from Burning Contaminated Cellulose .......................... A.5

A.5 R Results t from f. Burning Mixed Fuels ..... ........ ...... ............ e A.7

A.6 Results from Burning 30% Kerosene/Tributylphosphate (TSP) ........... A.8

vii

INTRODUCTION

Aerosol generation characteristics of accidental particle releases in

nuclear fuel cycle facilities are being investigated at Pacific Northwest

Laboratory (PNL). The work is sponsored by the U.S. Nuclear Regulatory Commission, Office of Nuclear Materials Safety and Safeguards. Safety analysis

reports and environmental impact statements must evaluate, the consequence of

postulated accidents in or involving the facility in question. During an accidental release from a nuclear fuel cycle facility, the dominant pathway to man

is usually through airborne particles, so it is necessary to determine an aerosol source term (i.e., the quantity of material initially airborne from an

accident).

.This report presents the results of two series of experiments investigating the release of radioactive aerosols in fuel cycle facility fires., The

first series consists of 40 experiments involving combustible solids contaminated with uranium dioxide powder, uranyl nitrate hexahydrate (UNH) solutions,

and UNH salt. The second series consists of 16 experiments involving combustible liquids [kerosene/tributyl phosphate (TBP) mixtures] with solutions of

nitric acid. The acid contains uranium, cesium, strontium, and ruthenium,

while the kerosene/TBP was used both in a pure state and contaminated with

uranium.

The purpose of the experimental program is to provide time-dependent radioactive aerosol source term data for safety analyses and for the FIRIN computer

code. FIRIN is a fire compartment source term code for fuel cycle facility.

fires. The current FIRIN radioactive source term models are based on the

results of a series of experiments measuring the fractional release from specific types of fire accidents (Mishima and Schwendiman 1973a,b,c). The results

obtained in these experiments were not time dependent and are applicable mainly

to the accident configuration for which they were performed. The subject series of experiments was done to develop models that can be applied to many fire

situations and to provide information on the rate and particle size of radioactive particles released in a fire.

Experimental procedures and results are discussed in this report for the

burning of contaminated combustible solids and liquids.

1

EXPERIMENTAL PROCEDURES

Two series of. experiments were performed to determine the rate and amount

of airbornelmaterial and the aerodynamic particle size of the aerosols generated by burning contaminated combustibles. Four solid combustibles were burned

in a set. of 40 experiments in which contaminant form, configuration, and concentration; airflow; heat flux; and type of ignition system were varied. In a

second series consisting of 16 exper•iments involving combustible liquids, a

mixture of 30% TBP in kerosene was burned over a nitric acid solution. Four

configurations were examined: acid/fuel with uranium, acid with fission products/fuel with uranium, acid with fission products and uranium/fuel, and acid

with fission products and uranium/fuel with uranium. The apparatus, sample

preparation, procedures, and analysis are described in the following sections.

APPARATUS

The experimental apparatus used in the burn experiments is called the Combustion Aerosol Release Equipment (CARE). Figure 1 is a diagram of the equipment. An adjustable-height aluminum plate supports a milled aluminum base.

The base was machined to prov~ide support for a 0.8-m-long, 18-cm inside-dia

quartz tube. Burning of solid combustibles takes place in a shallow pan positioned approximately midway in the tube. Air (or oxygen) enters the base and

travels through a 13-cm layer of glass beads, which disperse and equalize the

airflow in the tube. The combustion gases exit through the top of tube and are

drawn into a'hood where they are diluted with air. The combustion gases and

air enter an insulated pipe and the filtration manifold. Four 8- x 10-in, filter holders in the manifold sequentially sample the aerosol in a predetermined

order. After leaving the manifold, the gas velocity is measured with a hot

wire anemometer. A High-Efficiency Particular:Air (HEPA) filter bank is

located downstream to trap any remaining aerosol. Except for the filtration

manifold, the CARE was designed to be similar to small-scale burn apparatus at

Factory Mutual Research Corporation, Norwood, Massachusettls (Steciak, Tewarson,

'andNewman 1983).

The CARE is located within the Radioactive Aerosol Release Tank (RART.),

which acts as a secondary containment system. The RART is a stainless steel

cylindrical enclosure approximately 3 m high and 2.9 m in diameter with a 20-m3

volume, about, the size of a small room.

Radiant heat flux to simulate nearby fires or other heat sources is provided by-four radiant panels .mounted symmetrically around the quartz tube above

the sample. A radiometer is used to calibrate the output of these panels.

3
To

Off-Gas

Analysis

Hot Wire

Anemometer

To Exhaust

Filtration

Manifold

To

Aerosol

Analyzers

Collection

Hood

I m

Quartz

Radiant

Heat

Panel

Sample

Holder

Base

Glass

Beads

Air Load Cell

Inlet (Water-Cooled)

FIGURE 1. CARE Combustion Apparatus

4
For combustible liquids, the apparatus was modified slightly. A metal or

glass beaker was used in place of the shallow pan. A heat tape was used to

provide an external heat flux to the liquid. A single radiant panel provided

external heat flux to the top surface of the liquid in several experiments.

The mass loss rate of the burning material is measured by a load cell coupled to the sample holder. Aerosol number concentration and particle size distribution is measured using an optical particle counter. A cascade impactor is

also used for particle sizing. Data from the particle analyzer are fed to a

computer. Combustion gases are analyzed with real-time analyzers for oxygen,

hydrocarbons, carbon dioxide, and carbon monoxide. Temperature profiles are

measured by thermocouple rakes located above the quartz tube and in the off-gas

ducts. Data from the off-gas analyzers and thermocouples are fed to a data

logger.

Air flow in the apparatus varies with location. Air velocity in the large

duct below the filtration manifold is about 15.24 m per minute (fpm). This

duct has a diameter Sf 25.4 cm, so the total airflow is 'about 0.013 cubic.

meters per second (m /s). This number is fairly constant throughout the

apparatus, although there is some air leakage around the valves in the

filtration manifold. The highest air velocities are in the 15-cm ducts

directl,• below each filter holder. The air vTlocity here is about

0.066 m /s. The lowest air velocity, 0.002 m /s, occurs across the face

of the 0.9-m outside-dia (OD) dilution hood.

COMBUSTIBLE SOLID EXPERIMENTS

Parameters for the combustible solid experiments are shown in Table 1.

A total of 40 experiments were performed.

Experimental Parameters

Four combustible materials were burned in these experiments; each is

listed below along with its use in nuclear fuel cycle facilities.

* polymethy~lmethacrylate (PMMA)--glove box walls, hood windows

* polychloroprene (PC)--rubber gloves, window gasketing

* polystyrene (PS)--ion exchange resins

" cellulose--paper towels, rags, glove box liners.

The contaminant material used in all the experiments was depleted uranium

in various chemical forms. Depleted uranium dioxide has been shown to be a

suitable surrogate for plutonium and mixed oxides in previous studies (Sutter

1983). The depleted uranium was used as a powdered dioxide, in solution with

nitric acid, and as a salt of uranyl nitrate hexahydrate.

5
TABLE 1. Parameters for Contaminant Combustible Solid Experiments

Run#

3

4

5

6

7

8

9

10

11

12

13

14

15

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41-

51

55

Material

cel I ul ose

cel lul ose

cel 1 ul ose

PMMA

PC

PC

PC

PMMA

PC

cellulose

PMMA

PMMA

cel I ul ose

PS

cel 1 ul ose

PMMA

cel I ul ose

PMMA

cel l ul ose

cellulose

PC

PS

cel l ul ose

cel lul ose

cel lul ose

PMMA

PMMA

PMMA

PMMA

PMMA

PMMA

cellulose

PMMA

cellulose

PS

cellulose

mixed

mixed

PMMA

PS

Contaminant

liquid

powder

liquid

powder

powder

liquid

powder

liquid

powder

powder

powder

salt

powder

liquid

liquid

liquid

salt

liquid

salt

powder

salt

liquid

powder

powder

powder

powder

powder

powder

powder

powder

powder

powder

.powder

powder

liquid

powder

powder

liquid

powder

liquid

Heat

Flux, %

100

50

100

100

100

100

100

70

100

100

100

70

100

100

100

100

100

70

100

100

100

10

100

100

100

100

100-.

100

100

0

0

100

0

100

0

100

1 00

0

100

Ignition(a) Oxygen, %

Y 21

N 21.

N 21

Y 21

Y 21

Y 21

N 21

Y 21

Y 21

Y 21

N 21

Y 21

Y 21

Y 21

Y 21

Y 21

N 21

Y 21

Y 21

Y 21

Y 21

Y 21

Y 12

Y -6

Y 6

Y 21

Y 21

Y 21

Y .21

Y 21.

N: 21

Y 21.

Y 21

Y 21

Y 21

N 21

Y 21

Y V 21

Y * 21

Y 21

Comments

Data incomplete

High .air flow

Thick layer

Thick layer

Pile

-Pile PMMA over powder

Background

Data incomplete

Data incomplete

Data incomplete

Data incomplete

Background

Data incomplete

Data incomplete

(a) Y indicates an ignitor was used, N-indicates

used..

(b) 100% heat flux is 24 kW/m 2 .

that no ignition system was

6
External radiant heat fluxes of 13 and 24 kW/m 2 were used to simulate various-sized fires. Oxygen concentrations were kept at 21% (ambient) except for

three experiments (26, 27, and 28). Twelve percent oxygen was used in run 26.

Six percent oxygen was used in runs 27 and 28. In one run air flow through the

tube was raised from 8 Lpm to 11 L'pm.

Two different ignition systems were used. Both. systems used a methane gas

flame to provide ignition, but one nozzle gave a flame approximately 2.5 cm

above the surface of the sampile, while the other nozzle could be adjusted to

give a flame that impinges on the sample surface, Using thefirst nozzle,

ignition occurred when a flammable mixture of vapors formed above the sample.

and was ignited, causing flashover to the surface. With the second nozzle, the

flame impinging on the surface caused higher surface temperatures and higher

vapor generation rates than the first nozzle and also ignited the vapors as

soon.as they left the, surface. of the sample. Much shorter ignition times were

observed with the second nozzle.

Sample Preparation

The configuration of combustible and contaminant can have;.a significant

effect on uranium release. Configuration was varied for each contaminant material and is described in the following paragraphs. Specific details for indivi-dual. runs are also given.

Three-contaminant materials were used in these experiments. The first was'.

a depleted uranium dioxide (DUO) powder,. Previous work by Sutter, Johnston,

and M~ishima (1981) using sedimentation methods characterized the powder as having a mass median diameter (MMD)'of 1.0 ýim and a a of 2. Table 2 gives the

particle size distribution of the powder. Scanning electron microscope (SEM)

measurements of the agglomerates on a PMMA slab were also made and are shown in

Table 2. SEM measurements show an MMD of 5.0 Lm. and a ag of 2.

The second contaminant material was a solution of uranium as UNH in' nitric

acid. Uranium concentration is 208.7 g/L,(Sutter, Johnston, 'and Mishima 1981).

Other properties characterizing UNH include a density of 1.54 g/cm3, viscosity of 1.70 cp, and a surface tension of 62.88 dyne/cm (Sutter 1983).

The third contaminant material was an air-dried salt cake of the UNH solution.. The cakes were prepared by.placing a known amount of UNH solution on the

combustible material and placing the sample in a warm oven with forced air circulation. The samples were left in the oven until no liquid was visible and

then allowed to sit at room temperature for at least a day. The uranium is

presumably in'the form of UNH crystals, but the exact amount of hydrated water

is'not known.

7
TABLE 2. DUO Particle Size Distribution

Size, ýim

20

10

8

6

4

2

1

0.8

Measured ,

Cumulative Mass~a), %

97

95

94

'93

92

85

50

40

Measured (

Cumulative Mass(b) %

96

92

82

60

32

13

2

0.2

(a) Sutter, Johnston, and Mishima (1981) -, liquid

sedimentation.

(b) SEM analysis of agglomerators on PMMA Slab.

Four combustible-materials were used in these experiments: cellulose, PS,

PC, and.PMMA. Cellulose was used in the form of paper towels. Preliminary

testing showed that about 1 g of powder could be picked up on each towel using

reasonably good laboratory practice... This amount was used as an upper limit

for the amount of powder placed on a towel. Other tests showed that up to

60 cc of UNH solution saturated a'towel,. A towel that was wrung, out before

disposal might have about 20 ccof solution still in it. 'These numbers were

used in setting the amount of contaminant solution to add to each towel. Each

towel was 0.3 x 0.4 m and folded in quarters. -Towels contaminated with powder

were usually contaminated on one side only and then folded to expose only

uncontaminated sides. Towels soaked in liquid were crumpled to a ball shape

before burning. Towels with air-dried solutions were left flat and folded in

half again (a total folding into eighths).

Polystyrene was burned in the form of small angular beads. Enough UNH

solution was added to each pile of beads to coat them without leaving free liquid in the void space.

Polychloroprene was cut in the form -of approximately 8- x 8-cm pieces out

of an actual glove box glove." The PC was placed flat in the bottom of the

burni~ng~pan and contaminated to a level of 7.5g/m2 uranium, the amount corresponding to a coating of powder visible to the unaided eye (Mishima,

Schwendiman, and Ayer 1979, p. 44).

8
Polymethylmethacryl ate was used in the form of 5-715-cm-dia circles of

1.27-cm-thick Plexiglas@. This particular form of PMMA not only supports combustion, but is also combustible. The PMMA normally used in glove box windows

will not support combustion by itself but can supply fuel. The contaminant

material was poured or spooned onto the top surface of the PMMA slab and then

either spread out with a spatula to obtain an approximately even layer or left

in a pile. In an actual facility the contaminant material would probably settle out of the air onto the surface. The amount of powder contaminant used

ranged from 0.02 (a level of 7.5 -g/m 2 ) to 1.7 g. Liquids were poured on the

surface to form pools of various thicknesses.

The following is a description of the sample preparation for each run in

which data were successfully collected. Amounts of combustible material and

contaminant material, and a brief description of the preparation process are

given.

" Run #3 - Three paper towels were soaked in 100 mL of UNH solution.

The towels were crumpled.

* Run #4 - Three paper towels were contaminated with -1 g of DUO each.

The DUO was placed in a stainless steel pan and wiped on the surface

of the towels. The towels were then crumpled to expose only uncontaminated surfaces.

* Run #5 - Three paper towels were soaked in 75 mL of UNH solution and

crumpled.

* Run #6 - A 7.6-cm-dia, 1.3-cm-thick PMMA slab was coated with 0.05 g

of DUO. The DUO was weighed out, placed on the surface of the slab,

and-evenly spread with a spatula on the surface.

* Run #7 - A piece of PC, approximately 8 by 8 cm, was coated with

0.08 g of DUO. The DUO was weighed out, placed on the surface, and

spread with a spatula.

* Run #8 - 5 mL of UNH solution were placed on a piece of PC. Because

the PC was larger than the bottom of the burning pan, the UNH col-,

lected at, the bottom, giving non-uniform coverage of the PC surface.

* Run #9 - Sample preparation same as Run #7.

® A registered trademark of the Rohm and Haas Company.

9
* Run #10 - A 5.7-cm-dia, .1,3-cm-thick PMMA slab was coated with 5 mL

of UNH solution. The solutilon covered the'whole surface in a continuous layer.

* Run #11 - Sample preparation same as Run #7.

* Run #12 - Sample preparation same as Run #G, except that 0.3 g DUO

per towel was used."

* Run #13 - Sample preparation same as Run #6, except that a 5.7-cm-dia

PMMA slab with 0.02 g DUO was used.

* Run #14 - A PMMA slab similar to that of Run #10 was coated with UNH

solution, placed in a low-temperature forced convection oven for several days, and air dried in a ventilated hood for several more days.

Approximately 1.2 g of UNH salt were deposited in a fairly even layer

over the surface of the slab.

Run #15 - Sample preparation same as Run #1.

* Run #17 - 35 g of PS beads were soaked in 6 mL of UNH solution. No

free liquid was observed on the surface of the beads.

Run #18 - One fourth of a paper towel was soaked in 10 mL of UNH

solution. The remainring3/4 of the towel was left dry and uncontaminated and was wrapped around the wet 1/4 towel. Another uncontaminated towel was crumpled and placed next to this towel in the burning

pan.

Run #19 - Sample preparation similar to.Run #10 except that 2 mL of

UNH solution wereused.

* Run #20- A paper towel was soaked in 8 mL of UNH solution, placed in

a low-temperature forced convection oven for several days, and air

dried in a ventilated hood for several days. The towel has -3.5 g

UNH salt in it. The now stiff towel was broken in half and the two

halves piled on top of each other in the burning pan.

Run #21 - Sample preparation same as Run #10 except that 0.1 mL UNH

was used on a 5.7-cm-dia PMMA slab..

* Run #22 - Sample preparation similar to Run #20.

* Run #23 - Sample preparation similar to Run #1 except that two towels

and 2 g DUO were used.;

10
Run #24 - A p-iece of PC, approximately 8 x 8 cm, was coated with 3 mL

UNH, placed in a low-temperature forced convection oven for several

days, and air dried in a ventilated hood for several days. The PC

had -1.5 g of UNH salt on it.

Run #25 - Sample preparation similar to Run #17 except that 10 g of

PS beads and 4 mL of UNH solution were used.

* Run #26 - Sample preparation similar to Run #23.

" Run #27 - Sample preparation

* Run #28 - Sample preparation

* Run #29 - Sample preparation

DUO was used.

" Run #30 - Sample preparation

DUO was used.

" Run #31 - Sample preparation

DUO were used in a pile.

* Run #32 - Sample preparation

DUO were used in a pile.

" Run #33 - Sample preparation

DUO were placed under slab.

" Run #34 - Sample preparation

DUO was used.

" Run #35 - Sample preparation

* Run #36 - Sample preparation

" Run #37 - Sample preparation

brand of paper towel used.

similar

similar

similar

to

to

to

Run

Run

Run

#23.

#23.

#13 except that 0.44 g

similar to Run #13 except that 0.36 g

similar to Run #13 except that 1.13 g

similar to Run #13 except that 1.35 g

similar to Run #13 except that 1.66 g

similar to Run #13 except that 0.05 g

similar

similar

similar

to

to

to

Run

Run

Run

#1.

#34.

#35 except a different

* Run #38 - Sample preparation similar to Run #17 except that 6 g of PS

beads and 3 mL of UNH solution were used.

* Run #39 - Sample preparation similar to Run #1.

11
" Run #40 - 1 g. of DUO, was placed on a paper towel, and 1 g DUO was

placed on 15 g of PC.

" Run #41 - 25 mL of UNH liquid was absorbed by a paper towel, and 3 mL

UNH liquid was placed on a PMMA slab.

0 Run #51 - Sample preparation similar to Run #13.

" Run #55 - Sample preparation similar to Run #17 except that 25 g of

Amberlite IRA-900 ion exchange resin was soaked in 15 mL of UNH solution.

COMBUSTIBLE LIQUID EXPERIMENTS

The complete combustible liquid experiments are shown in Table 3. A total

of 15 experiments were performed, and complete sets of data were obtained for

11 experiments.

The combustible liquid used in these experiments was a mixture of 30% TBP

in normal paraffin hydrocarbon (NPH) (a kerosene-like.diluent). This liquid

was chosen because of its use as a solvent in the plutonium uranium reduction

oxidation extraction (PUREX) process. Other combustible liquids that might be

found in fuel cycle facilities include fuel oils, lubricating oils and greases,

and other solvents. Properties of the NPH solvent (Mishima and

Schwendiman 1973b) are:

Specific Gravity 60/60°F or 15.6/15.6 0 C 0.76

Viscosity at 25°C

Flash point ,C

The TBP/NPH mixture was burned as a layer over a -3 M nitric acid solution. Nitric acid is present in large quantities in fuel reprocessing facilities, and it was felt that in many accidents both nitric acid and the TBP/NPH

mixture could be involved.

The TBP/NPH mixture was used in both a "pure" form (no simulated radioactive contamination) and containing 101.2 g/L depleted uranium, The nitric acid

was used in pure form, containing simulated fission products (as listed in,

Table 3), and containing both simulated fission products and depleted uranium.

The TBP/NPH mixture was placed over a layer of nitric acid in a glass or

metal beaker. A heat tape was wrapped around the outside of the beaker to

12
TABLE 3. Contaminated Combustible Liiqui:d Experiments

Run # Acid P.hase Organic Phase. Comments

42 pure pure Data incomplete

43 pure pure Data iJncompl ete

44, pure spiked (a) Data incomplete

45 pure spiked (a)

46 pure spiked (a)

47 spiked (b) spiked (a)

48 spiked (b) spiked (a)

(b) 49 spiked (b) pure

50 spiked(c) pure Data incomplete

52 spiked (c) pure.

53 spiked (c) pure

54 pure pure

56 spiked (c) spiked (a) 150 mL acid/50 mL organic (d)

.:57 spiked (c) spiked (a) 100 mL acid/50 mL organic

58 spiked (c) pure 150 mL acid/5OmL organic

(a) Organic phase contains 101-,-2 g/L, uranium.

(b) Contains 0.16 g/L ruthenium, 0.50 g/L cesium,.

1.76 g/L st-rontium.

(c) Acid phase contains 0.43 g/L ruthenium, 1.34 g/L cesium,

4.69 g/L strontium, 188 g/L uranium.

(d) 100 mL acid/QO0 mL organic in other experiments.

provide initial vaporization of the TBP/NPH. Ignition was provided by a methane flame located approximately..8 cm above the beaker. Oxygen .concentration

was not controlled but was left at ambient (~-21%).

All of the combustible liquid experiments were made using combinations of

the five liquids described below. In each experiment, one-organic liquid was

paired with one inorganic acid.

The liquids were mixed to specification and have the following

compositions:.

* 30% .TBP in NPH - This is the primary organic solvent used in the

PUREX process.

30% TBP in NPH with 101.2 g/L uranium'- This solution represents the

used solvent that contains separated heavy metals.

2.5 M nitric acid - The primary dissolution acid in the PUREX

process.:

13
• 2.54 Mnit-ric acid-with:188 g/L -uranium, 0.43 gIL ruthenium, 1.34 g/L

cesium, and 4.69 g/L strontium- This solution simulates the PUREX

acid solution after dissolution and bef,ore contact with the organic

phase.

*2.88 M nitric acid with 0.16 g/L ruthenium, 0.50 g/L cesium, and

1.76 g/L strontium - This solution simulates the PUREX acid solution

after contact with the organic phase.

Any of these liquids could be present in an .accident in a fuel reprocessing facility. The organic liquids are the only combustible liquids, and only

the NPH fraction is combustible. The acid phases were included in these experiments to see if fire and heating would cause migration of the fission products

or transuranic elements across the phase boundaries. For example, as a contaminated organic liquid burns, some-of the.contaminant (uranium in this case) may

be driven out of the organic and into the underlying acid phase. The driving

force for this would be the change in solubility of uranium in the organic liquid-because of changes in temperature and composition.

The liquids chosen for each experiment were placed in metal or glass

beakers, and the beakers were wrapped in heat tapes. In some cases, a heat

lamp was also used to provide heat flux; 'however, external heat flux was not a

measured or controlled -variable in these experiments.

ANALYSIS OF FILTER SAMPLES FOR URANIUM AND FISSION PRODUCTS

A mixed acid leach solution was prepared in the following manner: approximately 400 mL of deionized water were placed in a 1-L flask. Approximately

310 mL of 5N HNO 3 were added to the flask and swirled. Two mL of O.05N HF were

added and swirled. The mixture was allowed to cool to room temperature before

Sadding water to bring the flask to volume.

Each filter was placed in a large glass-beaker and covered with 300 mL of

the mixed acid leach solution. A stirring rod was used to help break up the

filter. Beakers were-placed in a water bath at 45 to 55°C for approximately

30 h to aid filter digestion.

Filters were separated from the leachate by vacuum filtration using a

large buchner funnel.. Leachate was poured into a,500-mL volumetric ,flask and

brought to volume with deionized water.,,

The amount of uranium in the samples ,was analyzed using laser.fluorometry.

This method employs a pulsed nitrogen laser to excite uranium in a solution

containing a pyrophosphate reagent. The-fluorescent signals are amplified and

integrated, and the results are displayed on a meter.

14
Samples from the contaminated combustible liquid experiments underwent

additional analysis to detect ruthenium, cesium, and strontium. Atomic absorption was used for the cesium analysis, while inductively coupled plasma was

used to detect ruthenium and strontium.

A separate extraction process was used to separate uranium and fission

products from the organic leftover after some of the burns. In this process

10 mL of organic sample were placed in a 100-mL volumetric flask with 20 mL of

a solution containing 64.05 g of ammonium carbonate and 27.54 g of sodium

bicarbonate/L. The solution was heated to 75C in a water bath for about 30 h

with air bubbling through each sample. In some samples a precipitate occurred.'

Approximately 30 mL of 2 M HN0 3 were added to these samples and shaken. The

aqueous and organic phases of the sample were then separated by decanting, and

the volume of the aqueous phase was brought up to 100 mL with 2 M HNO 3.

In all the samples in which fission products were involved in the burn,

mass balances of the release and residue indicated a recovery of more than 200%

for cesium and strontium and a total lack of ruthenium. The ruthenium absence

may be caused by the formation of a ruthenium oxide precipitate in the analytical samples. The excess of cesium and strontium could be attributed to contamination in the sample solution interfering with analysis. Because of the

unreliability of the analysis data, fission product release is not presented in

this report.

15

RESULTS

. Weigit percent airborne ranged from less than 0.01 to 7. Figure 2 shows

the range of values for each of the contaminated fuel types burned., As shown

by the figure, PMMA gave the highest releases of the solid burn experiments.

10.0

1.0

aC

(D

W

a, a..

C,,

0

E

Il

0.1

Co

0

-a;

x

w

a.I

I)0 X

0-

xI 'N

.0 0

0.01

0.001

FIGURE 2. Results from Burning Contaminated Combustibles

17
Cellulose burns gave the lowestreleases. Fuel mixtures both from these and

previously reported experiments (Mishima and Schwendiman 1973a) gave airborne

releases of uranium similar to those of the cellulose burns.

Uranium released from the contaminated combustible liquid burns reached as

high-as 7%. Much higher releases were achieved in this set of experiments than

in similar previously reported experiments (Mishima and Schwendiman 1973b).

Because uranium release is highly dependent on fuel type, results are discussed and presented by fuel type in the following sections. Detailed data on

cumulative fractional uranium and smoke releases are given in Appendix A.

COMBUSTIBLE SOLIDS

Results are presented for 46 experiments in which combustible solids were

contaminated, then burned. Results are presented by fuel type in the following

order: PC, PS, PMMA, cellulose, and mixed fuels.

Polychloroprene (PC)

Five runs (#7, #8, #9, #11, and #24) burned PC contaminated with either

DUO powder, UNH solutions, or UNH salt. The smoke fractional releases (weight

of smoke produced divided by weight of fuel burned) ranged from 7 to 15%. The

uranium fractional release raaged from about 0.4 to 3.5%.

Run #8 was the only PC run with UNH solution. The uranium fractional

release of 3.5% was the highest of all contaminant forms, as shown in Figure 3. Most of the uranium was released during the flamning combustion period

(between the first and third data points'on the graph). The release seems to

correlate fairly well with the smoke production rate.

Runs #7, #9, and #11 burned PC with DUO powder. These runs are shown in

Figure 4. Runs #7 and #9 were identical except that an ignitor was used in

Run #7. These two runs were virtually identical in smoke production and were

close to each other in uranium fractional release. The ignited run had a uranium fractional release of 1%, while the release for no ignition was 0.7%.

Both runs showed close correlation between uranium and smoke release rates.

Appreciable amounts of both smoke and uranium were released before sample ignition. The difference between uranium fractional release for these two runs is

small, so the presence of an ignition system may not be important. In these

cases, the PC burned for only 30 s even when an ignitor was used. This time is

small compared to the 7 min in which the material smoldered and changed shape

before flaming combustion.

'18
cE

w- 0.02

E•

#7 - Powder

0.01 - --- -----------

/ #24 - Salt Cake

0.00

0 1 2 3 4 5 6 7 8 9 10

Time (minutes)

FIGURE 3. Fractional Release of Uranium from Contaminated Polychloroprene

The third powder run, Run #11, was similar to the first two runs with powder, but a lower heat flux was used in the early part of the run. A lower uranium fractional release of 0.4% resulted. The heat lamps were run at 70% power

for the first 13 min of the run. The lamps were then increased to 100% power,

and ignition occurred 25 s later. The sample flamed for 45 s and then smoldered for about 1 min. The majority of uranium and smoke was released during

the time of the lower heat flux; that is, before ignition.

Run #24 burned PC with an air-dried UNH salt cake. The uranium fractional

release of 0.4% from this run was lower than the corresponding run with powder

contamination. Cohesive forces between the particles in the salt cake are probably greater than cohesive forces in the loose powder. The salt cake may also

have greater cohesion to the PC. Most of the uranium release occurred during

the flaming period. Uranium release also appears to correlate well with smoke

production.

19
0.010

0.009

E- 0.008 -- 0 #9 - No Ignition Source

0.0

c 0.007

C

.0

®= I

- 0.005

LL.

0.004 #11 -Lower Heat Flux

E - M 0.003 0 0

0.002

0.001 0.0011 . 10000

.0.000

0 4 8 12 16 20

Time (minutes)

FIGURE 4. :Fractional Release of Uranium from Polychloroprene

Contaminated with Powder

Polystyrene (PS)

Four runs (#17, #25, #38, and #55) burned PS beads covered with UNH solution. The uranium cumulative fractional release is shown in Figure 5.

Run #25, with a contaminant concentration more than twice that of Run #17,

had a uranium fractional release only slightly higher (0.18% versus 0.16%).

Run #25 was considerably smokier than Run #17 in terms of smoke fractional

20
0.0020

#25

0.0018

#17

0.0016 4P

S

0.0014

0

' 0.0012 / cc

,a 0.0010 /

.0o

LL 0.0008

" 0.0006

E

4 8 12 16 20

Time (minutes)

FIGURE 5, Fractional Release of Uranium from Polystyrene Contaminated

with Liquid

release, although both runs provided considerable amounts of smoke. A much

larger amount of PS was used in Run #25, which could lead to an underventilated, smokier fire. Run #38 had an even higher contaminant concentration and

gave a uranium fractional release of 0.8%. Thus, contaminant concentration

appears to have some effect on the fractional release of uranium, with higher

concentrations giving higher releases.

Essentially all the uranium was released prior to ignition of the PS.

Because half (or less) of the mass loss in each run occurred before ignition,

it appears that the uranium release rate will not correlate well with mass loss

21
rate. The uranium release rate does not appear to correlate with smoke release

rate, either. Most of the mass loss before ignition is caused by evaporation

of water from the UNH solution. Apparently, it is this mass flux that is

transporting the uranium. Just before ignition, the mass of PS beads and UNH

solution melted to a thick, viscous mass of molten PSthat had the appearance

of mincemeat. The fact that little uranium comes off after ignition would tend

to indicate that the majority of uranium has sunk down into the bulk molten

mass and been trapped inside. The uranium is therefore not released and

remains in the residue left over after the fire burns out.

One observation is that while the uranium and smoke release rates do not

correlate well, the total uranium fractional release correlates reasonably well

with the total smoke fractional release. This could be. useful for estimating

uranium-release in situations where the rate of release is not important.

Run #55 was made with actual ion-exchange resin *rather than just PS

beads. It was anticipated that the difference in structure between commercial

PS beads and specially designed, cross-linked resins might have an effect on

the release. Preliminary lab results indicate that the uranium fractional

release is about 0.1%, or about the same as. Run #17, which had approximately

the same contaminant concentration. Thus, the type of resin is probably not an

important factor in the release of uranium in PS fires.

Polymethylmethacrylate (PMMA)

Fourteen runs (#6, #10, #13, #14, #19, #21, #29 through #34, #36, and

#51), burned PMMA contaminated with UNH solutions, uranium dioxide powders, and

dried UNH solutions. Smoke fractional release ranged from 0.6 to 1.2%, while

uranium fractional releases ranged from about 0.25 to 4.5%. The cumulative

fractional release of uranium versus time is shown in Figures 6 and 7.

Runs #6, #13, #29 through #34, #36, and #51 burned PMMA with powder contaminant. The first two runs were essentially identical except that Run #6

used an ignition system and Run #13 did not. The uranium fractional releases

were 3.2 and 3.0% for Runs #6 and #13, respectively. The difference is slight

and is probably caused by experimental variation. Runs #29 through #33 were

done as a special study of the PMMA-powder system. Runs #29 and #30 used a

layer of DUO similar to Run #6, but much thicker. Runs #31 and #32 used a pile

of DUO in the center of the PMMA slab as opposed to a layer. Run #33 used a

layer as in Run #6 but for this run the PMMA was placed on top of the layer of

DUO. The uranium fractional releases were 3.5% for the runs with thick layers

of powder, 4.5% for the runs with piles of powder, and about 1.3% for the single run with DUO under PMMA. Run,#34 was a background run involving PMMA and

powder but no ignition system. In the absence of a flame, 0.2% of the powder

was removed. This amount seems to represent aerodynamic~entrainment by the air

flow in the system.

22
0.04

0.03 000-

#21

"6 0.02 -.

0.01

0.00

vO 8 16 24 32

Time (minutes)

FIGURE 6. Fractional Release of Uranium from'Contaminated PMMA

The DUO was released before ignition or early in the burning, period. The

,mechanisms that contribute to the release before ignition are probably

entrainment caused by the increase in vapor pressure"of the PMMA as it heats up

and the explosive ejectionwof particles by the explosion of gas bubbles in the

PMMA slab. These explosions were observed to occur during all PMMA runs.

Run.#36 was madelspecifically to identify how early in the experiment the

powder was released. It had been noticed in earlier experiments that most ofý

the powder came off before ignition. IhRun #36, two of the filter samples

were dedicated to the early part of the run instead of one. The results"from

this run showed about 31% of the total release coming off before the gas

bubbles formed and exploded in the PMMA and another 47% of the total release

coming off before ignition. The remaining 21% of the release came' off during

the flaming. period.

Ru'n #51 was made to investigate the effects of different types of ignition. In this run, no external heat flux was applied, and the PMMA slab Was

23
0.04

0.03

"•E

o .2

U.~

U_

0.02

0

-w

C-)

0.01

0.00

0 8 16 - 24 32

-Time (minutes)

FIGURE 7. Fractional Release of Uranium from PMMA

DUO Powder

Contaminated with

ignited on two sides simultaneously..: The uranium fractional

1.5% in this run is somewhat lower than earlier experiments,

cantly lower.

.release of about

but not signifiRun #14 burned PMMA contaminated with an air-dried UNH solution. Once

again, the release of uranium occurred before ignition. The uranium fractional

release of 0.65% is much lower than the '3% obtained from the powder-runs.

This is probably because of the stronger cohesive forces between the salt cake

and.PMMA slab.

Runs #10, #19, and #21 all burned PMMA with UNH solution contaminant. The

differences in the runs were-mainly in the amount of UNH solution placed on top

of the PMMA slab. Run #10 used 5 mL, Run #19 used.2 mL, and Run #21 used

0.1 mL. The results were quite similar for Runs #10 and #21, but Run #19 gave

a much lower uranium release. The analytical results of Run #19 are suspect,

however, so this run will not be considered further.- Run #10 had a uranium

24
fractional. release of 1.9%, while Run #21 had a release of 2.0%. This difference is quite small-and is probably caused by experimental variation. Once

again, the release occurred before ignition.

Cellulose

Seventeen runs (1, 2, 3, 4, 5, 12 ,15, 18, 20, 22, 23, 26, 27•, 28, 35,

37, and 39) burned cellulose contaminated with powders, solutions, or salt

cakes. Smoke fractional release ranged from 0.45 to 19%. Uranium fractional

released ranged from 7 x 10-5 to 3 x 10-3 and are shown in Figures 8 and 9.

Data from Runs #1 and #2 are incomplete and are not presented.

Runs #3, #5, and #18 used UNH solutions as the contaminant. Run #3 had

the highest contaminant concentration, and an ignitor was used. Run #5 had a

slightly lower concentration, no ignitor, and a slightly lower heat flux.

Run #18 had a much lower contaminant concentration and an ignitor, Run #3 gave

the highest uranium fractional release of the liquid runs at 1.5 x 10-4, twice

that of the other two runs. The effect of not having an ignitor was about the

same as using -a much smaller concentration of contaminant. Uranium fractional

releases of 7.5 x 10-5 and 7.1 x-10-5 were obtained in Runs #5 and #18,

respecti vely.

0.0003 - Ck

#20 -Salt Cake

r 0.0002

U. D•

0l .. #3- Liquid

#22 - Salt Cake oe

E 4) 0.0001 r p #5-Liquid

.w .•.,O#18- * Liquid

0 8 16 24 32 .40

Time (minutes),

FIGURE 8. Fractional Release of Uranium from Contaminated Cellulose

25
0.0010,

0.0009 #28 - High Air Flow

0.0008

E

._2

C

p 0.0007

0

4) Base Case

(A 0.0006

#26

0.0005 r #23

o #27

,, 0.0004 JK

0D #4

.>a.

_ No Ignition

0.0003 / " E #12

0.0002 . 2 /

#15

Iwo" - Lower Heat Flux.,

0.0001 . -0'. .9

0.0000

0 8 16 24 32

Time (minutes)

FIGURE 9. Fractional Release of Uranium from Cellulose Contaminated

with Powder

Runs #20 and #22 involved air-dried UNH solutions. The uranium fractional.

release was highest for Run #20, where no ignitor was used. The:.value of'2.9 x

10-4 is slightly higher than the value for the comparable powder -run (Run #4).

The uranium fractional release for Run #22 is 9.6 x 107,5 which-is lower than

the comparable powder run(Run #12). Part of the difference may be in fire

scaling, as one towel was burned in Runs #20 and #22, while three towels were

burned in Runs #4 and #12. The overall range varies by a factor of 3 on'these

releases, which are the smallest releases measured in these experiments.

26
Runs #4, #12, #15, #23., #26, #27, #28, #35, and #37 all burned Cellulose

with DUO powder contamination. Smoke fractional releases ranged from 1.1 to

4.2%. Uranium fractional releases ranged from 1.9 x 10-4 to 1 x 10-3. Figure 9 shows the release rate of uranium from these runs.

Run #28 gave the third highest uranium fractional release of 9 x 10,4 from

burning towels. This appears to be caused by the much higher air flow used in

this run. A lower oxygen concentration was used with twice as much. air flow.,

As will be seen later, oxygen concentration did not appear to have a large

effect, so air flow appears to be responsible for the release. Runs #23, #26

and #27 had approximately equivalent uranium fractional releases of 4.8 x 10-

to 5.5 x 10-4. The only difference in these runs was that the oxygen concentration was varied from 6 to 21%. Runs #4 and #12 were variations of Run #23,

with Run #4 having no ignitor and Run #12 having an ignitor but a lower contaminant concentration. Both runs had lower uranium fractional releases as a

result of the changes, with the fractional uranium release being about half the

release of Run #23. Run #15 was also similar to Run #23, but with a lower heat

flux. The uranium fraction release decreased to about 3 x 10- from this

effect.

Runs #35 and #37 involved the use of an ignitor but no external heat flux.

Runs #35 and #37 gave the highes• uranium fractional releases of all cellulose

runs. The releases were 3 x 10- and 1.1 x 10- , respectively. The high

releases may have been caused by the cellulose immediately beginning flaming

combustion instead of charring/smoldering'followed by flaming combustion. The

releases during flaming combustion for all runs seem to be higher than releases

during smoldering or after flaming combustion. The smoldering period may allow

the powder to react with the mineral residue and bind to it strongly enough to

reduce releases.

Run #39 was a background run involving cellulose and powder but no heat

flux or ignition.. The uranium fractional release of 1 x:lO- 4 measured the

effect of aerodynamic forces from the air flow in the system.

Mixed Fuels

Runs #40 and #41 were burns of combinations of various fuels. Run #40

involved cellulose and PC, while Run #41 involved cellulose and PMMA. The uranium fractional releases were 9.5 x 10-4 and 3.6 x 10- , respectively.

The order of magnitude of these fractional releases are similar to releases

from cellulosic materials.

27
COMBUSTIBLE LIQUIDS

Five different liquids, two combustible and three noncombustible, were

used in these experiments. These liquids-were used in combinations of one combustible and one noncombustible liquid, which resulted in six categories of

experiments.. Two. categories, one where both nitric acid and organic are uncontaminated and the other where nitric acid is spiked with fission products and

organic is uncontaminated, did not involve any uranium and are discussed in a

later paragraph on fission product release results. The remaining four categories are discussed below. Overall, the experiments .in each category were

fairly reproducible (with one exception discussion below), and there were obvious differences between the categories.

Pure Acid/Organic. with Uranium

Runs #44, #45, and #46 involved uncontaminated nitric acid.and 30% TBP in

NPH with uranium. Uranium fractional releases ranged from 0.004 to 0M0056 (0.4

to 0.6%). These runs: resulted in the lowest uranium fractional releases of the

four categories.

The relatively low fractional release of the uranium may be caused by the

experimental configuration and apparatus. In-these experiments, 100 mL of

organic liquid was placed..on top of 100 mL of acid in a metal beaker. The

beaker, was heated to simulate an external heat flux, and the organic vapors.

were ignited above the beaker. If the beaker was continually heated during the

run, the acid eventually boiled over and quenched the burning organic. If

heating of.the beaker was stopped at the time of .ignition, the acid boilover

was delayed but not eliminat-ed. Boilover in this case was caused by conductive

heat transfer through the walls of the beaker from the flame to the acid. The

substitution of a glass beaker for the metal beaker just delayed the boilover.

All three runs ended with a boiling acid layer quenching the flame and cooling

the organic".layer. Significant amounts (from 40 to 60%) of organic layer

remained unburned.

While these experiments may show that fires of organic liquid on:t.op of

aqueous liquids may put themselves out if sufficient heat is transferred to the

aqueous liquid, the numerical values of the uranium fractional releases may not

adequately describe those expected from the same configuration without boilover. However, uranium seemed to be released with smoke in these experiments.

Under the experimental conditions, the organic fuel typically ignited in

10 to 20 min and burned for another 10 to 20 min. No great differences were

seen in the releases for the shorter runs versus the longer. runs. This may be

because the run times were only different by a factor of 2, and the actual burn

time differences were less. than that. Based on these three experiments, a

28
uranium release of 0.6% may represent a lower boundary for the release. If

heat transfer from the flame to the acid is reduced, the fire could burn

longer, and the release may be higher.

Acid with Fission Products/Organic with Uranium

Runs #47 and #48 involved the nitric acid spiked with fission products and

30% TBP in NPH with uranium. Uranium fractional releases were from 0.025 and

0.027 (2.5 to 2.7%), respectively.

The uranium fractional releases obtained in these experiments are 5 to

6 times greater than those described in the previous section involving uncontaminated nitric acid. The presence of fission products in the acid phase

seems to enhance uranium release from the organic phase. The length of these

runs is similar to the previously described runs, both in total time and total

burn time, so no effect from burn time is noted. Similar quantities of organic

material remained after burning, indicating similar amounts of organic consumed. Other than a slight change in the difference in molarity between the

two acid solutions (the uncontaminated acid was 3 M, while the acid with fission products was 2.88 M), the difference in the results must be attributed to

the addition of fission products in the acid.

One theory is that when fission products are not present in the acid, heat

causes some of the uranium to migrate to the acid from the organic. When fission products are present in the acid, this migration is stopped, and more uranium can be released from the organic. However, analysis of the remaining acid

layer did not support this theory. Comparable amounts of uranium were found in

both the uncontaminated acid and the acid with fission product experiments.

Acid with Fission Products and Uranium/Pure Organic

Runs #52, #53, and #58 involved nitric acid with fission products and uranium with 40% TBP in NPH. Run #58 had a much lower release (0.2%) of uranium

than Runs #52 and #53 (6.0 and 7.1%, respectively). Runs #52 and #53 burned to

a dry residue, presumably consisting of TBP, residue from the NPH, and salts

from the acid. Run #58 did not burn to dry residue, and some of the NPH (-40%)

remained after the flame died out. The major differences in the three runs

were the amount of liquid used, the beaker material, and the heat input method.

Runs #52 and #53 used 100 mL each of acid and organic in a metal beaker with a

heat tape around the beaker. Run #58 used 150 mL of acid with 50 mL of organic

in a glass beaker with a heat lamp to provide external heat flux.

The high uranium releases appeared to be caused by production of a solid

residue. The heat necessary to evaporate the acid probably came from the flame

by way of metal beaker, while the glass beaker kept this heat transfer to a

minimum. These results give a spectrum of release that might be expected in a

29
fire. As in. the earlier liquid :runs, heat transfer from. the flame to the acid

seems to be a critical parameter. Also of significance is the complex uranium/

acid/organic material interactions noted in the previous section. Even in

Run #58, where very little of the acid layer was boiled off, the fractional

release was significant. The uranium may be released during vaporization of

the acid and, at the same time, transferred to the organic layer with release

during subsequent combustion of the organic.

Acid with Fission Products and Uranium/Organic with Uranium

Runs #56 and #57 involved solutes in both the organic and aci'd layers.

uranium releases were 1.6% and-0.8% for Runs #56 and #57, respectively. Note

that these runs did not burn to a solid residue, so the high releases of Runs

#52 and #53 would not be expected, which was indeed the case. The releases

obtained in Runs #56 and #57 are lower (by a factor of 3) but higher (by a factor of 5) than Run #58 where no solid residue was produced. Strangely enough,

however, the-release is less than the release in runs whereuranium was present

in the organic phase only. No reason can be given for thisý other than experimental variation.

Fission Product Release

Fission product simulants consisting of cesium, strontium, and ruthenium

in "typical" fuel reprocessing concentrations were added to four of the com-;-

bustible liquid experimental subsets (a total, of nine experiments). The analytical method used was not adequate to provide reliable data. Overall mass

balances of the release and residue indicate an excess of 200 to 300% in the

case of cesium and strontium and a total lack: of, ruthenium. The ruthenium

absence may be caused by the formation of a ruthenium oxide precipitate in the

analytical samples. The excess of cesium and strontium could be attributed to

a contaminant in the solution that interfered with analysis.

Because of the lack of data, no conclusion as to the airborne-release of

fission product can be made.

SIZE DISTRIBUTION :OF AEROSOLS

The size distribution of airborne particles, was measured in at least one

run. for each of the fuels burned., Table 4' lists the airborne mass.,median diameter (AMMD) and geometric standard deviation for the runs in wh~ich particle

size was taken.

30
TABLE 4. Size of Aerosols from Burning Contaminated Combustibles

Run # Fuel AMMD, pým 2_ Less than 10 ptm

10 PMMA(a) 4.3 2.3 84

11 PC(b) 19.9 4.6 16

12 Cellulose >0.1 97

14 PMMA 4.9 4.6 63

23 Cellulose 10.5 5.7 40

28 Cellulose 7.8 5.2 47

30 PMMA 3.9 2.5 84

38 PS(c) 1.7 3.8 90

51 PMMA 1.4 4.3 95

56 TBP/NPH 0.6 3.1 99

(a) Polymethylmethacrylate.

(b) Polychl orop rene.

(c) Polystyrene.

31

REFERENCES

Mishima, J., and L. C. Schwendiman. 1973a. Fractional Airborne Releases of

Uranium (Representing Plutonium) During the Burning of Contaminated Wastes.

BNWL-1730, Pacific Northwest Laboratory, Richland, Washington.

Mishima, J., and L. C. Schwendiman. 1973b. Interim Report: The Fractional

Airborne Release of Dissolved Radioactive Materials During the Combustion of

30 Percent Normal Tributyl Phosphate in a Kerosene-Type Diluent. BNWL-B-274,

Pacific Northwest Laboratory, Richland, Washington.

Mishima, J., and L. C. Schwendiman. 1973c. Some Experimental Measurements of

Airborne Uranium (Representing Plutonium) in Transportation Accidents.

BNWL-1732, Pacific Northwest Laboratory, Richland, Washington.

Mishima, J., L. C. Schwendiman, and J. E. Ayer. 1979. Estimated Airborne

Release of Plutonium from Westinghouse Cheswick Site as a Result of Postulated Damage from Severe Wind and Seismic Hazard. PNL-2965, Pacific Northwest Laboratory, Richland, Washington.,

Steciak, J., A. Tewarson, and J. S. Newman. 1983. Technical Report: Fire

Properties of Combustible Materials Commonly Found in Nuclear Fuel Cycle

Facilities. FMRCJ.1.063R8.RC, Factory Mutual Research, Norwood,

Massachusetts.

Sutter, S. L. 1983. Aerosols Generated by Releases of. Pressurized Powders and

Solutions in Static Air.. NUREG/CR-3093, Prepared by Pacific Northwest

Laboratory for the U.S. Nuclear Regulatory Commission, Washington, D.C.

Sutter, S. L., J. W. Johnston, and J. Mishima. 1981. Aerosols Generated by

Free Fall Spills of Powders and Solutions in Static Air. NUREG/CR-2139.

Prepared by Pacific Northwest Laboratory for the U.S. Nuclear Regulatory

Commission, Washington, D.C.

33

APPENDIX A

PERCENT AIRBORNE FROM BURNING

CONTAMINATED COMBUSTIBLES

TABLE A.1. Results from Burning Contaminated Polychloroprene (PC)

,Cumulative %

Release

Run # Time, min Uranium Smoke Notes

7

9

11

8

24

0

1.0

1.5

2.8

7.5

0

1.2

2.3

4.0

10.0

0

8.3

13.6

15.1

15.7

0

0.7

1.3

2.3

9.0

0

1.0

2.0

4.4

7.5

0.0

0.48

0.97

1.01

1.03

0.0

0.64

0.76

0.78

0.80

0.0

0.24

0.31

0.35

0.37

0.0

0.11

2.27

3.23

3.47

0.0

0.12

0.39

0.42

0.42

0.0

4.4

11.5

12.9

13.9

0.0

8.6

13.1

14.2 14.8

0.0

1.5

5.0

6.7

7.0

0.0

1.5

5.8

7.5

10.3

0.0

1.2

6.9

9.6

10.0

DUO powder

Heat flux = 23 kW/m

2

DUO powder

Heat Flux = 23 kW/m 2

No ignition

DUO powder

Heat Flux = 13 kW/m 2

UNH liquid

Air-dried UNH

A.1
TABLE A.2. Results from Burning Contaminated Polystyrene (PS)

Cumulative %

Release

Run # Time, min Uranium Smoke Notes

17

25

38

55

0

9.0

10.0

13.5

18.5

0

6.7

7.8

9.3

12.8

0

5.3

6.5

12.8

0

4.0

7.5

20.0

0.0

0.15

0.15

0.16

0.16

0.0

0.17

0.18

0.18

0.18

0

0.74

0.7 6

0.77

0.78

0.0

0.5

2.1

4.7

5.9

0.17 mL UNH/g PS

0.0

0.6

2.9

7.0

9.6

0

0.8

2.3

2.7

3.0

0.0

1.1

3.8

4.0

4.1

0.4 mL UNH/g PS

0.5 mL UNH/g PS

0.6 mL UNH/g PS

Amberlite ion exchange

resin

A.2
TABLE. A.3. Resultsi- from:Bu'rning Contami'nated

Cumulat ive,-.,*%

ý Release4.,

# Time, mi n .Uranium .. Smoke

Polymethylmethacrylate (PMMA)

Run Notes

6

13

0

14.5

18.0

2405 31.5

0.

9.0

19..0

27.,3

34.6

0.0

2.9

3L2

3.2

3.2

00

2.3

:2.8

2.9

3.0

0.0

0.1

0.4

0.8

0.9

DUO powder

No ignition

DUO powder

0'.0.

0.1

0.3

0.5

0.6,

29

30

31

32

0

4.4

9.1

14.4

18.4

0

5.0

7.9

13.7

17.0

:. 0

7.8 14.0

19.5

0

4-.5•

9..3

14.3

19.3

0.0

1.0

3.3 3.4

3.5

0.01

2.0

3.3 3.5

... 3.6

-0.0

0.4 .0. .4, "

4.2

4.4

4.4

0

* 0.6

*4.1"

4.3 -- 4.5

0.0

0..3 - 1.1

1.3

1.3

0.0 -0..I 0.5

1.0

1,1

0.0

0.1

0.6 1 .1

1I.1o

0.0

0.6

1.1-

0.0 0.1-

0.5

1.1

1.1'

0.0

•0.7

1.1

1.1

DUO powder

Thlick layer

DUO powder

,Thick l ayer-

,DUO. powder

Pile,

DUO powder ,!i

Pil e

33 0-

10.3

13.3

15.5

21.0

DUO powder

:Under PMMA

A.3
TABLE A.3. (contd)

Run #

34

Time,; min0

5.0

10.0

15.0

20.0

Cumulative Release %

Uranium Smoke

0.0 0.0

0.07 0.003

0.13 0.003

0.21 0.063

0.25 0.063

Notes

DUO Powder

No burn, only entrainment

36

51

10

19

21

14

0

5.0

7.3

12.8

18.6

0

4.5

14.5

20.5

30.3

0

13.8

15.4

20.3

26.0

0

6.5

9.6

12.8

15.5

0

4.1

7.5

13.3

16.7

0

7.3

10.5

13.3

16.6

0.0

1.2

2.9

3.2

3.7

0

-0.42

1.10

1.30

1.52

0.0

I .9

1.9

1.9

1.9

0.0

0.1

0.2

0.2

0.2

.0,

1.1

1.6

1.8

2.0

0.0

ý0.3

0.6

0.6

0.6

0.0

0.07

0.17

0.7 5

1.09

0

0.02

0.35

0.56

0.56

0.0

0.2

0.4

1.0

1.1

0.0

0.1

0.5

0.9

1.2

0.0

0.1

0.4

0.8

1.1

0.0 0.04

0.3

0.6

0.9

DUO powder

Early sampling to detect

spike

DUO powder

Liquid UNH

0.12 mL UNH/g PMMA

Flame above sample

Liquid UNH

0.05 mL UNH/g PMMA

Impinging flame

No. 3 uranium sample

suspect

Liquid UNH

0.12 mL UNH/g PMMA

Impinging flame

Air-dried UNH

A.4
TABLE A.4. Results from Burning Contaminated Cellulose

Ti me,

Run # min

.Cumulative %

Release

Uranium Smoke

Cumul ative

Mass Loss, - Notes

4 0

3.0

7.5

11.0

14.0

12 0

7.4

8.5

12.2

17.0

15 0

21.3

22.3

29.3

33.5

23 0

3.2

4.0

7.7

11.0

26 0

3.3

5.0

7.3

10.4

27 0

4.1

5.9

7.7

12.7

28 0

3.7

6.1

6.8

11.4

35 0

1.0

3.0

7.0

0

0.0014

0.0084

0.0161

0.0188

0.0

0.0033

0.0086

0.0154 :•0.0239

1 0

0.0127 0.0144

0.0278

0.0303

0

0 .0123

0 .0328

0 .0475

0.0478

0

0.0254

0.0430

0.0515

0.0546

0

0.0204

0.0381

0.0431

0.0478

0

0.0566

0.0761

0.0860

0.0903

0.0

0.273

0.297

0.299

0.301

0

0.1

0.3

1.6

0

2.5 20.0

30.0

31.0

DUO powder

0.1 g DUO/g

Smoldering

cel lulose

0.0

0•1

0.3

0.4

1.7

0.0

1.1

1.2

1.4

1.5

0.0

0.8 0.9

1.0

1.1

.0

1.9

2.1

2.2

2.2

0.0

14.7

21.9

31.1

31.1

0.0

5.4

9.2

26.8

27.8

0.0

5.7

11.3

24.4

23.9

0.0

5.3 15.9

21.6

22.5

0

10.9

20.4

23.0'

21.8

0

4.5

20.7

22.4

23.2

DUO powder

0.03 g DUO/g cellulose

DUO powder

Heat flux - 13 kW/m(a)

0.09 g DUO/g cellulose

DUO powder

0.09 g DUO/g cellulose

'DUO powder

0.08 g DUO/g cellulose

0

3.2

3.7

3.9

4.2

DUO powder

0.09 g DUO/g cellulose

0.0

1.2

1.3 :1.4

1.5

0.0

0.2

0.4

0.4

0.4

DUO powder I

Airflow = 17.5 lpm(b)

0.095 g DUO/g cellulose

DUO powder

No heat flux

-0.1 g DUO/g cellulose

A.5
TABLE A.4. (contd)

Ti me,

Run # min

37 0

1.8

3.8

6.3

10.3

39 0

5.0

10.0

15.8

20 0

2.6

4.5,

9.8

22 0

1.0

2.31

8.3

3 0

7.00

12.0.

17.0

20.5

5 0

20.0 ::" 32.0

39.0

44.5

18 0

4.9

16.0 ~8.3

15.3

Cumulative %

Release

.Uranium Smoke

-Cumulative

Mass Loss, g Notes

0.0

0.018

0.077

0.144

0.153

0.0

0.006

0.0085

0.0098

0.0108

O0.0 011 0.019

0.021

0.029.

0.0

0.008.

0.009

0.010

.0

0.003

.0.009 0,013.

0.014

0.0

0.0003

0.0005

0.0043

0.0075

0.0-

0 .0015

-0,0023

0.0042

0.0070

0.0 t

0.03

0.1

0.3

0.3

DUO powder No heat flux

-0.1 g DUO/g .cellulose

0.0 0.01

0.03

0.03

0.0

3.7

4.8

4•.9

5.1

0.

0.3

0.4

0.5

2.3

12.0

18.1 19.0

0.0

0.3

0.5

0.8

1.1

0.0

5.3

.11.7

13.2

14.5

0

8 *2

12.0

14.'6

0

25.8

.62.5

93.8•

101.7

29.9

64.1

8449

108.8

0.0

6.9

13.2

24.3

38.0-,

DUO powder

No heat flux

No i gn it ion

Entrainment only

Airflow.= 1-1 lpm.

-0.2 g DUO/g cellulose

Ai r-dried UNH

Ai r-dried UNH

Heat flux =.13 kW/m 2

Liquid, UNH i

Liquid UNH

Heat flux = 7 kW/m 2

Liquid UNH

(a) Heat flux = 23 kW/m 2 *in all other runs.

(b) Airflow = 8 1 pm in all ,other runs.

A.6
TABLE A.5. Results from Burning Mixed Fuels

Cumulative %

Release

Run # Time, min Uranium Smoke Notes

40 0

1.0

3.0

4.5

9.0

0

5.0

8.8

14.5

25.8

0

0.016

Q.045

0.067

0.095

0

0.012

0.017

0.031

0.035

0.0

0.7

2.2

3.5

4.5

0

0.2

0.4

0.8

1.2

Cellulose and PC

DUO powder

41 Cellulose and PMMA

DUO powder

A.7
TABLE A.6. Results from Burning 30% Kerosene/Tributylphosphate (TBP)

Cumulative %

Release

Run # Time, min Uranium Smoke Notes (a)

44 Pure acid/organic with uranium

45

46

47

0

13.2

16.3

22.5

27.5

0.0

14.7

18.0

25.5

34.8

0.0

19.0

25..5

35.7

53.3

0.0

13.3

16.0

19.0

24.8

0.0"

0.009

0.040

0.132

0.404

0.0

0.054

0.395,

0.529

0.557

0.0

0.006.

0.081

0.031

0.434

0.0

0.032

3.105

0.343

2.517

0.0

0.034

0.335

2.054

2.697

0.0

0.068

0.170

0.606

5.978

0.0

0.097

0.206

2.620

7.088

0.0

0.10

0.53

1.32

1.89

0.0

0.10

0.70

1.00

1.10

0.0

0.04

0.17

0.33

0.76

0.0

0.15

0.69

1.46

3.18

0.0

0.10

0.69

2.28

2.88

0.0

0.18

1.10 2.03

8.11

0.0 0.22

1.1

4.64

8.94

Pure acid/organic with uranium

Pure acid/organic with uranium

Acid with fission product/

organic with uranium

48 0.0

17.0

22.0

26.3

34.0

Acid with fission product/organic

with uranium

52

53

0.0

8.3

12.5

20.5

61.3

0.0

9.3

14.2

37.0

65.0

Acid with uranium and fission

product/pure organic A ,

A.8
TABLE A.6. (contd)

Cumulative %

Release

Run # Time, min Uranium, Smoke Notes

56

57

58

42

43

49

50

54

0.0

24.8

31.5

39.3

57.3

0.0

19.2

28.5

39.5

.51.0

0.0

16.0

23.0

30.0

40.0

.0

17.3

19.2

23.0

36..8

0.0

0,032

0.060

0.330

1.563

0.0

0.010

0.028

0.621

0.809

0.0

0.003

0.006

0.012

0.170

0.0

0.18

1.15

2.45

6.51

0.0

0.10

0.83

2.52

3.03

0..0

0.20

2.04

4.55

6.44

0

0.25

0.79

1.60

2.53

Acid with uranium and fission

product/organic with uranium

150 mL acid/50 mL organic

Acid with uranium and fission

product/organic with ur

100 mL acid/50 mL organic

anium

;Acid with uranium and fission

product/pure organic

150 mL acid/50 mL organic

Pure acid/pure organic

0

14.8

18.5

30.0

0

12.5

17.0

21.0

31.5

0

12.3

16.8

27.0

32.0

0

1.06

1.94

2.87

0

0.28

1.36

2.79

4.51

0

0.16

1.10

2.74

3.81

No ignition. Slight boiling

loss. Pure acid/pure organic

Acid with fission product/

pure organic

Acid with fission product/Pure

organic

Pure acid/pure organic

(a) 100 mL of acid/lO0 mL organic unless otherwise noted.

A.9

NUREG/CR-4736

PNL-5999

DISTRIBUTION

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43 Pacific Northwest Laboratory

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G. W. Dennis (5)

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NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION I. REPORT NUMBER (Amwged by TIDC. add VOa. No.,ifsa.nyj

12.841 NRCM 1102. 32N1.3202 BIBLIOGRAPHIC DATA SHEET NUREG/CR-4736

SEE INSTRUCTIONS ON THE REVERSE. PNL-5999

2. TITLE AND SUBTITLE 3. LEAVE BLANK

Combustion Aerosols Formed During Burning of Radioactivel

Contaminated Material s-Experimental Results 4. DATE REPORT COMPLETED

MONTH YEAR

5. AUTHORIS) February 1987

M. A. Halverson 6. DATE REPORT ISSUED

M. Y. Ballinger MONTH YEAR

G. W. Dennis March 1987

7. PERFORMING ORGANIZATION NAME AND MAILING ADDRESS (In.de Zip Cod.) B. PROJECT/TASK/WORK UNIT NUMBER

Pacific Northwest Laboratory

P.O. Box 999 9. FIN OR GRANT NUMBER

Richland, WA 99352 B2481

10. SPONSORING ORGANIZATION NAME AND MAILING ADDRESS (Include, Zip Codel 1 Ia. TYPE OF REPORT

Division of Fuel Cycle and Material Safety

Office of Nuclear Material Safety and Safeguards

U.S. Nu•lear Regulatory Commission b. PERIOD COVERED .Inusiv d=J

-Washington, DC 20555

12. SUPPLEMENTARY NOTES

13. ABSTRACT (200 wolrd or Ianl

Safety assessments and environmental impact statements for nuclear fuel cycle facilities

require an estimate of potential airborne releases. Radioactive aerosols generated by

fires were investigated in experiments in which combustible solids and liquids

were contaminated with radioactive materials and burned. Uranium in powder and liquid

form was used to contaminate five fuel types: 1polychloroprene, polystyrene, polymethylmethacrylate, cellulose, and a mixture of 30% tributylphosphate (TBP) in kerosene.

Heat flux, oxygen concentration, air flow, contaminant concentration, and type of

ignition were varied in the experiments. The highest release (7.1 wt%) came from ..burning TBP/kerosene over contaminated nitric acid. Burning cellulose contaminated

with uranyl nitrate hexahydrate liquid gave the lowest release (0.01 wt%). Rate of

release and particle-size distribution of airborne radioactive particles were highly

dependent on the type of fuel burned.

14, DOCUMENT ANALYSIS - a. KEYWORDS/DESCRIPTORS 15. AVAILABILITY

STATEMENT

combustion, radioactivity, aerosols

b. IDENTIFIERSIOPEN-ENDED TERMS

unl imi ted

16. SECURITY CLASSIFICATION

fThi/ POg.)

unclassified

(Thn, roort)

unclassified

17. NUMBER OF PAGES

18 PRICE