f

.tH-f 0'^ Co

NBS TECHNICAL NOTE 969

^-^fAU 0^

U.S. DEPARTMENT OF COMMERCE/ National Bureau of Standards

S Reactor:

umtnary of Activities

^ 1976 to June 1977

53

969

'8o

!^^TMm
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards^ was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and

technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the

Office of Experimental Technology Incentives Program.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Center for Radiation Research — Laboratory Astrophysics'' — Cryogenics^ — Electromagnetics '^ — Time and Frequency'.

THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational insti- tutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists Of the Office of Standard Reference Materials, the Office of Air and Water Measurement, and the following divisions:

Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services developing and promoting the use of avail- able technology; cooperates with public and private organizations in developing technological standards, codes, and test methods; and provides technical advice services, and information to Government agencies and the public. The Institute consists of

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THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus wthin the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer

languages. The Institute consist of the following divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE OF EXPERIMENTAL TECHNOLOGY INCENTIVES PROGRAM seeks to affect public policy and process

to facilitate technological change in the private sector by examining and experimenting with Government policies and practices in order to identify and remove Government-related barriers and to correct inherent market imperfections that impede

the innovation process. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS; promotes the development of the National Standard Reference Data System and a system of in- formation analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services

to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units:

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1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

' Located at Boulder, Colorado 80302.
APR 2 6 1978

oo

NBS Reactor: Summary of Activities

July 1976 to June 1977

fJO .9W

Frederick J. Shorten, Editor

Reactor Radiation Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

^.^^^^ °^ ^o,

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

U, 6 . NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued April 1978
National Bureau of Standards Technical Note 969

Nat. Bur. Stand. (U.S.), Tech. Note 969 Ibh pages (Apr. 1978) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1978

For sale by tJie Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20434

Stock No. 003-003-01907-1 Price $3.50

(Add 25 percent additional for other than U.S. mailing).
FOREWORD

The National Bureau of Standards Reactor was built not only to serve the needs of the NBS but also those of other government agencies

and the greater Washington Scientific Community. The Reactor Radiation

Division was established to operate the reactor and to foster its scientific and technological use. Toward this end, the Division has a small

nucleus of scientists experienced in the use of reactors for a wide range

of scientific and technical problems. In addition to pursuing their own research and developing sophisticated experimental facilities, they ac- tively seek out and encourage collaboration with other scientists, engaged

in challenging programs, whose work can benefit from use of the reactor,

but who as yet do not have the reactor experience necessary to take full

advantage of the facilities available. The Division also provides irradiation services to a wide variety of users as well as engineering and

other technical services.

The reactor operates at 10 MW and is designed to provide more than

25 experimental facilities ranging from intense neutron beams to extensive

irradiation facilities, making it one of the most versatile high flux

research reactors in the country. Thus it is able to serve a large number

of scientists and engineers in a broad range of activities both within

and outside the NBS.

This report attempts to summarize all the work done which is dependent on the reactor including a large number of programs outside the

Division. The first section summarizes those programs based primarily

on Reactor Radiation Division (RRD) initiatives whereas the second and

third sections summarize collaborative programs between RRD scientists

and other NBS or non-NBS scientists respectively. The fourth section

summarizes NBS work originating entirely outside the RRD which requires

no collaboration with RRD scientists. The section entitled, "Service

Programs" covers those programs originating outside NBS but for which

RRD provides irradiation services. The remaining sections are selfexplanatory.

iii
FOREWORD

Appreciation is extended to F. J. Shorten of the Reactor Radiation

Division for his extensive contributions to the editing, organization

and preparation of this report, and L. Sprecher, C. O'Connor, D. Davitt

and P. Lewis for efforts in typing manuscripts.

R. S. Carter

Chief, Reactor Radiation Division

National Bureau of Standards

IV
ABSTRACT

This report summarizes all those programs which depend on the NBS

reactor. It covers the period from July 1976 through June 1977. The

programs range from the use of neutron beams to study the structure and

dynamics of materials through nuclear physics and neutron standards to

sample irradiations for activation analysis, isotope production,

radiation effects studies, neutron radiography and nondestructive

evaluations

Key words: Activation analysis; crystal structure; diffraction: isotopes;

molecular dynamics; neutron; neutron radiography; nondestructive

evaluation; nuclear reactor; radiation.

V
TABLE OF CONTENTS

FOREWORD iii

ABSTRACT v

A. REACTOR RADIATION DIVISION PRO^IRAMS 1

The Lattice Dynamics of 6-PdD 1

X

The Lattice Vibrations of CeD 2 Measurement of the Crystal Field Splitting in

Cerium Dihydride 5

Crystal Dynamics, Phase Transitions and Orientational

Disorder in Ionic Crystals 8

Neutron Diffraction Determination of the Crystal

Structure of TiCuD 11

Application of Robust/Resistant Techniques to Crystal

Structure Refinement 13

Isotope Shifts of Phonons lA

Construction of a Neutron Flat-Cone DiffTactometer 16

Development of a Triple-Axis Polarized Beam

Spectrometer 18

Cold Neutron Source 19

Neutrino Scattering 19

Neutron Radiography 23

B. RRD COLLABORATIVE PROGRAMS . . .

.' 39

Studies of the Effects of Hydrogen in Titanium 39

Studies on the Structure of "Defect" Apatites 39

The Structure of Guanidinium Tetramolybodimethyl

Arsenate Monohydrate ^2

Crystal Structure of Triaminogaunidinium Nitrate by

Neutron Diffraction 45

The Structure of NH,N„ 48

Study of the Crystalline Components of Portland Cements ... 50

Battery Electrode Structure 51

A Study of the Phase Transformation in Trinitrotoluene ... 55

vx
Phonon Dispersion Curves of KN„ at 1 bar and 6.6 k bar .... 55

Aramoniuin-ion Dynamics in NH.CIO, 56

A Search for the Central Mode in Lithium Tantalate 59

Deformation of Uniform Polybutadiene Rubber Network 61

Small Angle Magnetic Scattering From Amorphous Rare-Earth

Iron Alloys 63

Magnetic Scattering in Dilute Pd(Fe) Alloys 64

Crystal Field Effects in the Superconductor

(Ce ^^Ho 27^^^2 ^^ Excited State Spin Waves in ErFe„ 68

Magnetism in ErFe_-H 72

Application of Neutron Diffraction to Non-Destructive

Testing Problems 73

C. NON-RRD NBS PROGRAMS 77

Activation Analysis: Summary of 1977 Activities 77

The Intermediate-Energy Standard Neutron Field (ISNF) 120

Fission Rate Intercomparisons with the Reactor Physics

Group at Argonne National Laboratory 123

U-235 Cavity Fission Irradiation Facility 125

Absolute Measurement of the DT Thick Target Yield at 191.3

KeV Using a Thermal Neutron Beam 126

Filtered Beam Facility 127

Precision Measurement of the Wavelength of Nuclear Gamma Lines

and the Compton Wavelength of the Electron 129

D. SUMMARY OF REACTOR OPERATIONS 132

Summary of NBS Reactor Health Physics Activities and

Services 132

E. SERVICE PROGRAMS 135

The Neutron Activation Analysis Program of the Food and Drug

Administration at the NBSR 135

Activation Analysis Program of the U. S. Geological Survey . . 149

The Use of Activation Analysis in Scientific Crime Detection

by the Federal Bureau of Investigation 152

VXi
ATF's Activation Analysis Program 153

Trace Elements in the Environment and Radioactive Decay

Studies 15A

Neutron Transmutation Doping of Silicon 163

Positron Annihilation Studies 164

Neutron Activation Analysis of Lunar Samples and

Meteorites 166

F. STAFF ROSTER 167

G. PUBLICATIONS 172

viii
A. Reactor Radiation Division Programs

THE lattice dynamics OF /3-PdD

X

C. J. Glinka, J. M. Rowe and J. J. Rush

Efforts are continuing to study in detail the lattice dynamics

of the beta phase of palladium deutride PdD (0.6 £ x <^ 1.0). For

X > 0.8, PdD becomes superconducting and there is currently much

interest in the role of the lattice vibrations, particularly the optic

modes, in the inducement of superconductivity in this system. Present

efforts are aimed at comparing previous coherent scattering measure1 2

ments of the phonon dispersion curves and phonon lineshapes m

PdD ,„ with similar measurements on a crystal which is a superconductor.

A single crystal of PdD was prepared by H. Flotow, Argonne

National Laboratory, by slowly admitting D^ gas to a crystal of Pd at

350°C (to avoid the two-phase region of the phase diagram and facilitate diffusion) . The sample was then cooled to room temperature over

a period of days under a pressure of 70 atmospheres deuterium and

transferred to a high pressure sample container for further loading

and examination with neutrons. The concentration of the sample was determined by weighing before and after loading and subsequently con- firmed by measurement of the lattice constant. Selected inelastic

scattering measurements at this concentration showed no change in the

position of the peak of the optic phonon density of states from that

for PdD , . Also, the optic phonon lineshapes were severely broadened

as had been observed in PdD ,_. The only notable difference from

. b J PdD ,„ was an upward shift of about 5 to 10% in the frequencies of

. b J the highest energy longitudinal optic modes.

To further raise the concentration, the sample cell containing

the PdD ^ crystal was cooled to -70 °C and pressurized with D„ to

26,000 psi. The cell was then sealed off and allowed to warm to room

temperature to reach a final estimated pressure of 2.4 kbar. After

allowing several days for the crystal to reach equilibrium, the lattice

o constant was measured at 80K to be 4.063 ± .001 A which corresponds to

a D/Pd ratio of 0.87 ± 0.01. At this concentration the crystal is ex-
REACTOR RADIATION DIVISION PROGRAMS

pected to be a superconductor with a T of about 5K. A thorough examination of the phonon spectrum in this crystal will begin shortly.

1. J. M. Rowe, J. J. Rush, H. G. Smith, M. Mos toller and H. E. Flo tow

Thysioal Review Lettevs _33, 1297 (1974).

2. C. J. Glinka, J. M. Rowe, J. J. Rush, A. Rahman, S. K. Sinha and

H. E. Flotow, to be published.

THE LATTICE VIBRATIONS OF CeD2 -,2

C. J. Glinka, J. M . Rowe and J. J. Rush

The complete phonon dispersion relation including both optic and

acoustic modes has been measured along the major symmetry axes of a single crystal of CeD„ _ at 295 K by coherent neutron scatterirg.

This work has been done in collaboration with A. Maeland and G. G. Libowitz

of the Allied Chemical Corporation and represents our first efforts to

study in detail the dynamical properties of the cerium-hydrogen system,

CeH„ . where -0.2 < 6 < 1.0. The hydride phase of cerium is isostructural

with other rare-earth hydrides and can thus be considered a prototype

for a class of materials which has been widely studied in recent years.

There have been a number of studies of the dynamics of transition

metal and rare-earth hydrides by neutron incoherent scattering. The

results of many of these studies have been analyzed in terms of simple

2 central force models as first proposed by Slaggie for ZrH„ . However,

finite resolution and the inherent limitations of the incoherent scattering

technique did not permit detailed conclusions to be drawn, and single

crystals have not previously been available for coherent scattering

measurements to critically test the models. As a result of our measure- ments on CeD„ _, which are the first coherent inelastic scattering

measurements on a rare-earch hydride, we have been able to test Slaggie 's
REACTOR RADIATION DIVISION PROGRAMS

model in both its original (four parameter) and more general (eight

parameter) form.

The results of our measurements of acoustic phonons in CeD„ ^„ are shown in figure 1 where the phonon energies are plotted versus one cartesian component of the phonon wave vector, expressed in units of

2TT/a. The dashed dispersion curves in the figure were calculated from

Slaggie's simplified central force model in which the so-called

bond-bending force constants are neglected and only four near neighbor

bond-stretching force constants are treated as parameters. The dashed

curves are seen to fail to fit the transverse branches. The solid curves

in figure 1 were calculated by including bond-bending forces in the

model and give an adequate fit to the measured dispersion curves except

for the [111] LA branch near the zone boundary.

Figure 1,

^

UJ

LjJ o

o

X

Q.

0.4 0.8 0.8 0.4 02 04

REDUCED WAVE VECTOR COORDINATE e =qa/27r

Acoustic phonon energies measured in CeD_ -i 9 ^t 295K along

the [100], [110] and [111] directions. The dispersion curves

in the figure were calculated from the four parameter (dashed

lines) and eight parameter (solid lines) central force model

due to Slaggie (Ref. 2).
REACTOR RADIATION DIVISION PROGRAMS

E

>-

tr

LU

UJ

o

X

Q.

0.2 0.4 0.6 0.8 1.0 0.8 0.6 0.4 0.2

REDUCED WAVE VECTOR COORDINATE C

Figure 2. Optic phonon dispersion curves in CeD„ „ along the [ lOO]

and [110] directions. The solid lines'are guides to the eye

where the data deviate from the dispersion curves (dashed

lines) calculated from the Slaggie central force model.

Although satisfactory to describe the acoustic modes, a second near neighbor central force model fails almost entirely for the optic modes.

Optic mode energies along the [100] and [110] directions are shown in

figure 2 together with dispersion curves (dashed lines) calculated with

the Slaggie central force model, including bond-bending forces. The

model results reproduce the splitting between the two optic mode

frequencies at the zone center (F) , but progressively deviate from the

measured frequencies (solid curves) as one proceeds across the zone. The data in figure 2 point out most clearly the need for a more sophisticated model for the lattice dynamics then has previously been supposed.

Calculations based on a screened shell model are currently in progress.

Further inelastic scattering experiments are planned on samples with

deuterium concentrations near the metal to semiconductor transition which

occurs near CeD„ . It is hoped that changes in the lattice dynamics

may be correlated with the striking changes in the electronic properties

which take place as a function of absorbed hydrogen.

1. C, J. Glinka, J. M. Rowe, J. J. Rush, A. Maeland and G. G. Libowitz,

Solid St. Conmun. 2_2, 541 (1977).

2. E. L. Slaggie, J. Phys. Chem. Solids 19_, 923 (1968).

4
REACTOR RADIATION DIVISION PROGRAMS

MEASUREMENT OF THE CRYSTAL FIELD SPLITTING

IN CERIUM DIHYDRIDE

C. J. Glinka, J. M. Rowe and J. J. Rush

3+

In cerium dihydride, the ground state multiplet of the Ce ion,

2 F_/^ due to a single 4f electron, is split into sublevels by the

electrostatic field of the crystal. This crystal field splitting may

be measured directly by inelastic neutron scattering whereby information

regarding the effects of hydriding on the 4f electron, as well as the

3+

symmetry and strength of the electric field at the site of the Ce ion,

may be inferred. Thus as part of our program to study this prototype

rare-earth hydride system in detail, we undertook an investigation of

the crystal field splitting in the same single crystal of CeD„ ^ ^ used

to study the lattice dynamics (previous section). An additional motivation

for a careful measurement on this system arose from the conflicting

1 2 results for the crystal field splitting obtained recently by two groups '

from measurements on polycrystalline CeD„ „^ and CeH, qq.

Constant-Q scans made with a triple-axis spectrometer over energy

transfers (neutron energy loss) from zero to over 100 meV revealed only

a single peak at "hoa = 20 meV which could not be ascribed to a vibrational

mode of the crystal. This single resonance, which showed no dispersion,

was positively identified as a crystal field transition from both its

temperature and Q-dependence, which are shown in figures 1 and 2. In

figure 1, the intensity of the peak is seen to decrease with increasing

temperature as expected for a crystal field transition and contrary to

the behavior of a phonon excitation. Figure 2 shows that the scattered

intensity (measured at reciprocal lattice points to avoid interference

from coherent phonon scattering) decreases with Q although not as sharply

3 3+

as suggested by a calculation of the Ce free ion magnetic form factor

(solid curve in figure 2)

The observation of a crystal field transition demonstrates that the

4f electron remains localized on the Ce ion and is thus little affected

by hydriding. The single transition observed corresponds to a crystal

5
REACTOR RADIATION DIVISION PROGRAMS

00C

Z3O

O

C

o

300

200

100

200

100

T= 15 K

T = 150 K

Q =(2,0.0)

T = 80 K

J^ J^

T = 300 K

.Ax v^^

-//-

10 20 30" 10 20

Energy Transfer (meV)

30

Figure 1. Neutron groups observed in constant-Q scans in the vicinity

of l!^ = 20 meV in CeD at various temperatures. The peak

intensity decreases with increasing temperature as expected

for a crystal field transition.

field of cubic symmetry which splits the F , level into a quartet (^n)

D / Z O and a doublet (T ) . A transition energy of 20 meV, however, contradicts

1 the suggestion that a nearest neighbor point charge model, in which the

hydrogens have the charge -le, is adequate to explain the crystal field

splitting. In this model a transition energy of 20 meV would correspond

to a charge of -0.6e. Our results suggest that screening effects are important and must be considered in any realistic calculation of the

crystal field.
REACTOR RADIATION DIVISION PROGRAMS

Figure 2,

0.2

(002)

(220)

CeD2,2

T = 15 K

(004) V 1 (333) (335)

0.2

Q

0.4 0.6

Sine

4 TT

(A-)

Data points are proportional to the square root of the integrated intensity of the crystal field peak (figure 1) in

in CeD_ „ measured at several reciprocal lattice points at

15K. Data are plotted relative to a calculation (solid curve)

of the Ce free ion magnetic form factor.

1. D. G. Hunt and D. K. Ross, J. Less-Common Met. 45^, 229 (1976).

2. P. Vorderwisch, S. Hautecler, J. B. Suck and H. Dachs, "Crystal

Field Effects in Metals and Alloys," A. Furrer ed . , Plenum Press

p. 47 (1977).

M. Blume A. J. Freeman and R. E. Watson, J. Chem. Phys. 2Z.> 1245

(1962).
REACTOR RADIATION DIVISION PROGRAMS

CRYSTAL DYNAMICS^ PHASE TRANSITIONS AND

ORIENTATIONAL DISORDER IN IONIC CRYSTALS

During this past year, we have achieved a breakthrough in our understanding of the high temperature phase transition in KCN, which is

a widely studied prototype of a large number of inorganic solids of

formula M XY which exhibit similar transitions. In addition, we have

begun measurements on the (KCN) (KBr)-_ alloy system with x = 0.25.

1. The 168K Phase Transition in KCN J. M. Rowe, N. J. Chesser,

J. J. Rush, and K. H. Michel, J. Naudts , (University of Saarlande,

W. Germany.)

We have completed detailed high-resolution studies of the [100] TA

mode in KCN as a function of temperatures. There is no "central" peak

for this soft mode system. However, we have been able to fit out data

to a model which treats the interactions of the non-spherical (CN) ions

with the elastic strains in the system. This model was first proposed

by Naudts and Michel to successfully explain the temperature dependence

of the elastic constant C,, observed by ultrasonic techniques.

In figures 1 - 3 we show the fit of this new model to our data for

KCN at various temperatures and wavevectors. As can be seen, the

agreement is good - the remaining discrepancies are likely due to an over-simplified resolution correction applied to the theory. With

these latest results and the new model, we can now describe the 168K

phase transition in a manner consistent with all of the data.

This is a first order phase transition from a disordered NaCl

structure to a partially ordered orthorhombic structure. However, in a limited sense, the phase transition can be thought of as almost second

order and the strain associated with the elastic constant C, , is the

order parameter in the high temperature phase. Although this phase

transition has been described as ferroelastic, our earlier diffraction

studies clearly preclude such a model since there is very little change

in preferred orientation of (CN)ions and no occupation of the low

8
REACTOR RADIATION DIVISION PROGRAMS

-0.6 -02 02

tiw (meV)

Figure 1. Neutron scattering lineshapes for KCN fitted to model of

nickel (note no central peak)

.

240

160

80,

296

KCN

Q=(0,l,2O,0,0)

. A.:

Q7meV / \

•,

'

1 200 A^

KCN

0=(0.2,2O,0O)

160

120

- n

\

*

*•*

RO -it \ 296 K y\. / " V «l = l3meV .' \

40' V--^^ V

•J

^al (meV) Figure 2. Neutron scattering lineshapes foi^ KCN at different wavevectors

and reciprocal lattice points.
REACTOR RADIATION DIVISION PROGRAMS

KCN Q = (-.5,2.0,0.0)XXX eV

-I I

tio) (meV)

Figure 3. Neutron scattering lineshapes for KCN for wavevectors of 1/2

the distance to the Brlllouln zone edge. Note that softening

point persists.

temperature orientation as one approaches the transition temperature.

In the present model, which agrees with the neutron, ultrasonic and

Brillouin data, the elastic constant C, , is driven soft by fluctuations

in the local (CN) ion orientations. There is no critical scattering.

Thus, a more correct analogy is to a Jahn-Teller system, rather than a ferromagnetic system. A final paper on KCN is being prepared in which

all available data will be presented.

2. (KCN) (KBr) J. M. Rowe, J. J. Rush, N. J. Chesser, Argonne

National Laboratory.

As a first step in a program to study mixed cyanide-bromide

crystals, we have begun to study the lattice dynamics of (KCN) -^ (KBr)„ t- Preliminary results of these studies indicate that

where the widths and centroid frequencies of the neutron groups observed

10
REACTOR RADIATION DIVISION PROGRAMS

in this crystal are presented for three temperatures as a function of

momentum transfer for the [100] TA mode. (This branch is soft in pure

KCN as one approaches 168K) . Since there is no phase transition in

this mixed crystal we can cool the sample down to lOK. The neutron

groups increase in width as T is decreased to lOOK and the centroid

frequency decreases, in analogy with KCN, showing an interaction between the (CN) ions and the C,, elastic constant. However, at lOOK

and lOK the widths do not change but the frequencies increase. Although

we cannot yet explain these results in detail, we do believe that the

model used above for KCN can be adopted to these mixed crystals and

work is proceeding along these lines.

NEUTRON DIFFRACTION DETERMINATION OF THE CRYSTAL

STRUCTURE OF TiCuD

A. Santoro and J. J. Rush

and

A. Maeland

(Allied Chemical Research Center, Morristown, NJ)

As a part of a research effort involving compounds potentially

useful for hydrogen storage, the crystal structure of the compound

TiCuD has been determined and refined with neutron diffraction powder

techniques using the total profile analysis proposed by Rietveld

.

The experimental conditions used to take the neutron powder pattern are;

Monochromatic Beam: reflection 220 of a Cu monochromator

o Take-off angle and mean neutron wavelength: 42.5° and 0.925 A

Horizontal divergences of collimators (in min arc) 20,23,24

Mosaic spread of monochromator '^^10 min arc Theorectical values of full-width at half maximum parameters

U = /200, V = -4650, W = 2420 x 10~^deg^

Sample container: Vanadium can of "^1 cm diameter

11
REACTOR RADIATION DIVISION PROGRAMS

The results of refinement are indicated below:

TICuDq g, PA/nmm; a = 3.0324(7), c = 6.847(2) A

'

20. . . ^ = 5.0°, 20-. ^ = 90.0°, step - 0.1 initial final ' ^ No. of ind. reflections = 102, no. of observation above background = 584

R = [(Z|l , - I - |)/EI ^ ] = 0.092 ' obs cal ' obs

R = [(Ely , - Y ^ |)/Iy , ] = 0.13

p 'obs cal ' -^obs

O Ti • Cu 3 D

2861(7)

>-b

Figure 1. The crystal structure of TlCuD„ „. The Ti-D distance of

1.934(4)A compares well with the structure of 1.923(3)A found

in TiD ., by Sidhu, Heaton and Zauberis (Acta Cryst. 9^, 612,

1956).-^'^

Atom X y z N((Dccupancy factor)

Ti 1/4 1/4 0.6753(9) 1.0

Cu 1/4 1/4 0.0932(5) 1.0

D 3/4 1/4 1/2

°2

0.89(1)

Overall temperature factor = 0.64(2) A

The D atoms are located at the center of slightly distorted tetrahedra of

Ti atoms.

1. Rietveld, J. Appl. Cryst. 2, pp. 65-71 (1969)

12
REACTOR RADIATION DIVISION PROGRAMS

APPLICATION OF ROBUST/rESISTANT TECHNIQUES TO

CRYSTAL STRUCTURE REFINEMENT

W. L. Nicholson

(Battelle Pacific Northwest Laboratories, Richland, WA)

and

E. Prince

The philosophy of robust/resistant statistical estimation and its

application to crystal structure refinement was described in NBS

Technical Note 939 (1977) . The program of refinement outlined there

has been completed on 12 data sets of the single-crystal intensity project of the International Union of Crystallography. Specifically,

each data set consisting of measured structure factors on 1) (A) tartonic acid has been analyzed four times with various options of RFINE4:

1) attempt to "recreate" the literature results of Hamilton and

Abrahams;

2) add secondary extinction to the classical weighted least

squares refinement; incorporate the biweight w-function and do robust/

resistant refinements with outliers cutoff 3) at estimated six sigma;

and 4) at estimated four signs.

The results of Hamilton and Abrahms are not reproduced exactly

partially because of a difference in convergence criteria and inclusion

or not of several extreme outliers in each data set. For a selected

subset of six good data sets the recreation has more consistant parameter estimates. Over all experiments the recreation has a tendency to

give larger diagonal thermal coefficients possibly because of small

differences in the treatment of atomic scattering factors.

Inclusion of the Zachariasen model for secondary extinction significantly improved the seven refinements which had descrepant strong re- flections. Again there was a reduction of variability across parameter

estimates for the six good experiments (four of these were among the seven with strong extinction.

Inclusion of biweight with estimated six sigma cutoff did not

13
REACTOR RADIATION DIVISION PROGRAMS

change the results significantly. Inclusion of biweight with estimated

four sigma cutoff increased the variability of parameter estimates

across the six good experiments.

Further data analysis is in progress on the calculation of parameter estimate precision and agreement measures for the biweight

approach to refinement. The most obvious advantage of the biweight

procedure is associated with resistance. In the classical refinement

with secondary extinction subjective decisions were required to eliminate extreme outlier reflections, whereas biweight performs the same function automatically and objectively. The affect of the robust aspect

of the procedure, dealing with error distributions with tails that are thicker than three of a gaussion distribution, is subtler, and more

difficult to document in real experimental data sets, although studies

3 of synthetic data sets have shown that there are advantages here also.

Hamilton and Abrahams noted strong biases in parameter estimates

for several data sets. These biases were not removed by inclusion of

either secondary extinction or biweight. Thus biweight compensates for

lack of careful screening of the data base, and for non-gaussian error

distributions, but not for bias in the experimental data.

1. E. Prince and W. L. Nicholson, mS Teoh. Note 939 (1977).

2. W. C. Hamilton and S. C. Abrahams, Acta Cryst. A26, 18 (1970).

ISOTOPE SHIFTS OF PHONONS

R. C. Casella

Recently H. Prask and G. Rosasco have studied isotopic shifts between the Raman spectra of hydrogenous and deuterated ammonium perchlorate

at NBS . The work is part of a broader program for determining the phonon

spectra of ammonium perchlorate, also involving inelastic neutron-scattering studies by H. Prask and N. Chesser. This experimental work has

motivated a theoretical study of the general isotopic shift problem in

crystals for the case when more than one atomic species is involved with

14
REACTOR RADIATION DIVISION PROGRAMS

a given sjmunetry type, i.e. irreducible representation of the little group

at wavevector q. We also consider the case where the rigid molecule

approximation applies (e.g., to the ammonium and perchlorate complexes)

and where nonvanishlng components exist for both translational and librational motions (involving several molecular species) in association

with a given observed eigenmode. When only one molecular type is involved and the motion is either purely translational or purely librational,

~ 1/2 ~ 1/2 then the well known relations, c6 = (M/M) oj and w = (l/l) co apply to

the translational and librational frequencies respectively. Here,(jo and

w denote the frequencies associated with the molecular masses M and M

involved in the substitutions; I and I are the corresponding moments of

inertia (assumed isotropic). For the general case mentioned earlier,

the product rule of molecular systems is extended to translatlonally

invariant crystalline solids at arbitrary wavevector q, making use of

properties of the projected symmetry states elucidated by Rao and Trevino.

We find that the frequencies cjo(qrY) and co(qrY) associated with irreducible

representation r at q are related by the following expression:

N N

n a)(qrY) = ^^ ( y^;^ x^ ( [1 Ygx ) " w(qrY)- (D

Y = l \^ / \\ / Y = l

The quantities x, , x„ , ... , y.,, y„, , ... appearing in Eq.(l) refer to

A D AA DA

the mass and principal moment ratios associated with the isotopically

substituted molecular species, A, B, ... . That is.

''a '^"a'^a^''

^^^

^AA = ^h,'h/'' (^)

where, in Eq.(l), X runs over inequivalent principal moment axes. P ,

P.,, ... , Q.,, Q„, , ... denote the number of symmetry states (belongin

D AA BA

to a given row of the r th irreducible representation at q) associated

15
REACTOR RADIATION DIVISION PROGRAMS

with translations and rotations of molecular species A, B, . N is

r the dimension of the symmetry reduced block diagonalized dynamical matrix

2 associated with the representation, r. Work continues in this area.

1. K. K. Rao and S. F. Trevino, J. Chem. Phys. 5_3, 4624 (1970) and

S. F. Trevino, private communication.

2. R. C. Casella, Phys. Rev. Ml, 4795 (1975).

CONSTRUCTION OF A NEUTRON FLAT-CONE DIFFRACTOMETER

A. Wlodawer, E. Prince and A. Santoro

The principles of construction of a flat-cone dif f ractometer

utilizing a position-sensitive detector have been presented two years

ago. Such an instrument has now been constructed. It was designed as

a modification of an existing four-circle dif fractometer, in which a

Figure 1. Flat-cone dif fractometer . The position sensitive detector is

housed in a vertical shield, visible on the right. All other

components are those of a standard form-circle dif fractometer

.

16
REACTOR RADIATION DIVISION PROGRAMS

counter was replaced with aim long position-sensitive detector

placed in the vertical plane as shown in figure 1. The flat-cone

diffractometer is capable of counting several diffracted beams simultaneously. The software for on-line control by the PDP-11/40 computer

has been written. The system was tested by collecting preliminary

diffraction data using a Ta-O^ single crystal, which with one long unit

cell axis (40. 4A) serves as a model of macromolecular samples. An

example of diffraction intensities obtained by rotating the crystal

around c* axis in 1° increments is given in figure 2. It is clear that

the intensities are well resolved along the shortest reciprocal axis

(fe*) . We are planning to start the data collection using a protein

crystal very soon.

1200

800

400

4800

4200

ii 3600 zz

2 3000

£g 2400

Q.

!^ 1800 zo" 1200

600

ii' 30* 60sec

^ I -•**>.

Ji^

800

400

64 126 192 256 320 384 448 512 576 640 704 768 832 896 960 1024 CHANNEL NUMBER

Figure 2. Output of the position sensitive detector in three orienta

sec, X=2.4A

tions of the Ta„0 crystal. Each frame was counted for 60

1. E. Prince and A. Santoro, BBS Teoh. Note 896, 17 (1976).

A. Wlodawer and A. Santoro, "Flat-cone Dif fractometer Utilizing a Linear Position Sensitive Detector," to be published.

17
REACTOR RADIATION DIVISION PROGRAMS

DEVELOPMENT OF A TRIPLE-AXIS POLARIZED BEAM SPECTROMETER

C. Glinka, J. Rhyne

and

R. Williams

(Naval Surface Weapons Center, Whiteoak, MD)

A state of the art triple-axis neutron spectrometer utilizing

polarization-sensitive crystals as monochromator and analyzer is under

development at NBSR. With such an instrument not only the momentum and

energy dependence of the neutron cross section but also its spin dependence may be determined in a scattering experiment. For many

measurements, particularly on magnetic systems, this added capability

can be used to discriminate against unwanted sources of scattering and

thus greatly improve the precision of the measurement. Many other

experiments, in which the spin dependence of the cross section is of

chief interest, are possible only with polarization analysis of the

scattering.

Although the methodology of polarized neutron scattering has been

known for several years, use of the technique has been limited by the

relatively low intensities obtained from polarizing crystals. Recently,

however, we have tested single crystals of the Heusler alloy Cu„MnAl

and have found these crystals to have both good reflecting and polarizing properties. For example, the integrated reflectivities of these

crystals are comparable to those of "good" copper crystals and are some three to five times greater than were measured for typical Co(Fe)

crystals, which are the crystals most often used in polarized beam

work. With the Cu^MnAl crystals magnetized in a field of 3 kilogauss,

polarization efficiencies up to 99% could be attained when care was

taken to eliminate stray magnetic fields. Thus, use of these crystals

should significantly improve the practicality of polarized beam experiments .Samples to be studied will be mounted between the coils of a 60

kgauss superconducting magnet. Also incorporated in the spectrometer

18
REACTOR RADIATION DIVISION PROGRAMS

is an rf neutron spin resonance flipper coil for reversing the direction of polarization. The flipper coil has been tested and a flipping

efficiency of 99% is easily attainable. The spectrometer is expected

to be completed and become fully operational in the near future.

COLD NEUTRON SOURCE

E. Guglielmo

The cold source facility consists of a cryostat, bismuth tip, main

shield plug, cryostat shield plug, helium refrigerator, and associated

transfer lines.

The major components for the facility are nearing completion. All

parts of the bismuth tip have been fabricated and the final pairing of

lead and bismuth should be accomplished by December, 1977.

The cryostat was damaged in testing but has since been repaired and vacuum tests have been run. Only final tests remain before assembly.

The cryogenic plug needs to be filled with concrete and this will be

accomplished after final tests on the cryostat. Final tests on the whole

assembly with associated hook-up equipment remain to be completed.

NEUTRINO SCATTERING

R. C. Casella

The scattering of neutrinos and antineutrinos from nucleons is

analyzed within the (V - A) charged-current four-quark model of Glashow,

Illipoulos, and Maiani. Neutral current processes are obtained within

the Weinberg-Salam picture utilizing model parameters determined from

the charged-current processes. Rather pronounced scaling violations in

the small x region observed in weak and electromagnetic lepton-nucleon

interactions are accounted for via an energy dependent parameter

19
REACTOR RADIATION DIVISION PROGRAMS

2 1/2

5 = <

p_|^ > /k, where k is the center of mass momentun and

2 1/2

< p > - 0.3 GeV is the r.m.s. parton transverse momentum. Letting

X and y be the customary scaling variables, the naive parton model is

assumed to hold (in some average sense) for x >> ^, whereas for x < ^ quark-antiquark (qq) binding is expected to play an important role. The

model leads to an increasing number of sea quarks being freed as the

neutrino energy E increases and the region x < ^ recedes towards zero as

-m-1/2 m-, vN , vN ,^. ^, , V ,^. „. E . The cross section ratio a la (figure 1) and < y > (figure 2) are found to rise with energy in the range 10 GeV < E < 150 GeV, but less

so than indicated by earlier experiments, maintaining values closer to

2

the recent CIT and CERN data. The ratios of neutral to charged current

cross sections vary even less (figure 3) . The weak angle 6^ is found to

2 V / assume its canonical value, sin 9^^ = 0.3. Nevertheless, the da /dy model

W c distributions exhibit an increase near y = 1 as E increases. Within the

1.2

1.0

1 nT

[l \ 1 A

T

--<|—

C

] <»

• • 0.51

20 40 60 80 100

Ej, (GeV)

Figure 1. Ratio of antineutrino (v) to neutrino (v) charged-current

nucleon cross sections vs. energy E. Data from HPWE (Ref . 1)

At 150 GeV we obtain 0.51 for this ratio with an upperbound,

0.55. Recent CERN and CIT determinations lie in the range

0.4 to 0.5 (Ref. 2).

20
REACTOR RADIATION DIVISION PROGRAMS

model, analysis of dimuon experiments implies semimuonic branching ratios

for the decay of charm in the range 5% to 10%, assuming an SU(3) invariant

3 sea (figure 4) . The calculated mean number of strange particles per

neutrino induced dilepton event is 1.4 for the broad-band sources em- ployed at Fermilab in these experiments. The amount of qq sea in the

model increases from - 10% at 10 GeV to - 30% at 150 GeV. A paper is in

preparation.

l;^

0.5

0.4

0.3

T—I—I—I—I—I—I—I—I—I—I—I—

X<0.6

0.2^^ I I I J_L

50 100

E (GeV)

150

Figure 2. Average energy loss <y> of the lepton in v-nucleon scattering

vs. energy E. Earlier H§WF data (Ref. 1) are shown. Recent

CERN and GIT results lie between 0.3 and 0.35 (Ref. 2).

21
REACTOR RADIATION DIVISION PROGRAMS

E (GeV)

Figure 3. Ratios of charged to neutral current cross sections, R

R- . _ Agreement occurs when the weak angle 9 satisfies

sin e =0.3. Data from HPWF (Ref.l), CIT yRef.2), and

Gargamelle (low E)

.

0.04

and

U.UH 1 1

1— T A 1/ CITFR DATA

^°' » u CITF DATA

y V HPWF DATA

i

b"

::: 0.02 - ^.

-^

, ,

-

b" /

' ^ -

/ . 1 /<;

1 /I ^.,^'^'BACKGROUND n ^

50 150

(GeV)

250 250

Figure 4, Model predictions for the ratio of dimuon to single muon production for values of the semimuonic branching ratio B (treated

as an unknown parameter) equal to 5%, 7%, and 9%. CIT and HPWF

data are shown (Ref. 3). Employing the (recent) CERN data

(Ref. 3), the model leac^s to B - 10%, in satisfactory agreement

with the value obtained from the e e DORIS colliding ring

experiments (B =10% - 15%).

22
REACTOR RADIATION DIVISION PROGRAMS

1. A. Benvenuti et al., Phys. Rev. Lett, ri, 189 (1976); 36, 1^78 (1976);

37^, 1039 (1976).

2. J. Steinberger and C. Cundy, in papers presented at the Conference

on Particle Physics, Budapest (July 1977); F. Scuilli, M. Shaevitz,

private coiranunications.

3. B. C. Barish et al., CIT preprint (1977); M. Holder et al. , CERN

preprint (1977).

NEUTRON RADIOGRAPHY

D. A. Garrett

and

W. L. Parker

(Reed College, Portland, OR)

1. Technique and Facility Development

a. Thermal Neutron Xeroradiography

Xeroradiography was developed to take advantage of an edge enhancement inherent in the method which emphasizes small discontinuous changes

in object density with resulting improved contrast and accuracy of interpretation. The "image" is produced on the surface of a layer of

selenium which is non-conducting and has been given a uniform surface

charge. Spatially-modulated ionizing radiation renders the selenium

conducting so that the charge leaks off to the grounded backing plate

in an amount proportional to the exposure, provided that saturation does

not occur. The image is developed by spraying on graphite particles which

adhere to the selenium and are then transferred to a special paper producing an opaque radiograph. It can operate in either the positive or negative mode. At a discontinuity in the surface charge density the

electric field has a tangential component which produces lateral motion

of the particles with a resulting "starvation" at the discontinuity.

This is the edge effect.

23
REACTOR RADIATION DIVISION PROGRAMS

Since neutrons by themselves are non-ionizing, it is necessary to

employ a converter which emits ionizing radiation following neutron

capture. The converter cannot be in contact with the selenium surface

or the charge pattern will be destroyed. Good results have been obtained

using a standard gadolinium oxysulfide screen separated from the selenium

by about 0.5 mm. There is considerable evidence that the image is produced primarily by the 70 keV electrons resulting from thermal neutron

capture by the Gd nuclei. In the positive mode the optimum exposure

(10 n-cm ) is comparable to AA film used with a 25.4 ym Gd foil. The

resolution is also comparable. In the negative mode the resolution is

markedly poorer. At this point this behavioral characteristic is unexplained.

The resulting radiographs definitely show edge enhancement which

could prove very valuable in certain applications such as the detection

of corrosion. Other advantages are the absence of a darkroom and the

ability to have the final radiograph within two minutes after exposure,

b. Background Subtraction

The gamma ray contamination in collimated neutron beams used in

neutron radiography often results in a gamma radiograph being superimposed on the regular neutron radiograph. The result is a reduction

in radiographic contrast due to this gamma background. Although in

general, the energetic gamma rays generated from radiative capture of

thermal neutron have little or no effect on the film, the softer gamma

components can result in a gamma image on the film. Indeed these soft

gamma rays can be filtered with polycrystalline bismuth or lead, however

at the expense of some neutron flux. This loss can be an important

factor especially in the case of transportable neutron radiography

systems.

Although the technique of background subtraction has been employed

for a number of years for medical application in the subtraction of

x-ray images, no use has been made in the field of industrial radiography.

The technique has been successfully applied to the subtraction of

24
REACTOR RADIATION DIVISION PROGRAMS

the gamma fogging from neutron radiographs. Basically the principle of

background subtraction is as follows. Referring to figure 1, a positive

neutron radiograph utilizing on metal foil converters is produced having

gamma background fog. This is denoted by n + g. The converter is then

removed from the cassette, a positive gamma radiograph, denoted by g, is

produced of the object under inspection. Subtraction film having a film

U a - a

t

- a = u

k

-a

u-i-a

Figure 1. Block diagram illustrating the principles of background

subtraction.

25
REACTOR RADIATION DIVISION PROGRAMS

gamma of 1, i.e. the D-log E curve has a slope of 1 over a range of

radiographic densities, is employed to produce a negative image -g of

film g. Film -g is superimposed on film n + g to produce n + g - g = n. A negative film -n is then produced to furnish the finished neutron

radiograph with the gamma ray effect eliminated.

The method will have a significant impact in the area of field

neutron radiography since it is unfeasible to employ lead or bismuth

filters to eliminate the gamma ray background at a sacrifice in neutron

beam intensity. The technique is rapid, inexpensive and simple requiring

no computerized subtraction techniques. For the purposes of field neutron

radiography film registration can be sufficiently well produced to satisfy

the needs at hand for field applications.

c. Corrosion Detection In Aluminum Airframe Components

The primary objective of these investigations was to determine

the feasibility of detecting corrosion in aluminum Naval aircraft

components with neutron radiographic interrogation and the use of standard

corrosion penetrameters . Secondary objectives included the determination

of object thickness on corrosion image quality, the defining of minimum

levels of detectability and a preliminary inventigation of a means whereby

the degree of corrosion could be quantified with neutron radiographic

data.

The nondestructive detection and visualization of environmentinduced corrosion in aircraft presents an important maintenance problem

and economic impact in both the civilian and military sectors. Since

there is no reliable instrumental method by which corrosion can be

detected in inaccessible areas of aircraft structures, visual and

destructive inspection methods must presently be employed.

Corrosion in aircraft generally is induced by the presence of

moisture and oxygen. The corrosion products so generated oftentimes,

but not always, contain hydrogen in the forms of hydrated oxides or

26
REACTOR RADIATION DIVISION PROGRAMS

hydroxides. In the case of salt water Induced corrosion, chlorine may

also be present. Because of the high attenuation of thermal neutron by

hydrogen and chlorine, it should be possible to visualize corrosion

areas using neutron radiographic interrogation.

The basic procedures governing the neutron radiographic inspection

methods employed in these studies are outlined in this section. In

addition, the results of preliminary experiments at the NBS to establish

minimum levels of corrosion detectability and proposed methods to quantify

the degree of corrosion were investigated.

All radiographic data generated in these investigations was obtained using direct neutron imaging methods with various converter

screens. Manual film development was performed throughout with standard

industrial radiography chemistry. A 7 in. -thick section cut from an uncorroded C-2 aircraft vertical fin was used as a standard object to

be radiographed. The fin, which was obtained from the NAVAIR Rework

Facility at North Island, San Diego, California.

All radiographic data generated in these investigations was obtained using direct neutron imaging methods. Manual film development

was performed throughout with Eastman Kodak standard industrial radiography chemistry. A 7 in. -thick section cut from an uncorroded C-2

aircraft vertical fin was used as a standard object to be radiographed.

The fin was obtained from the NAVAIR Rework Facility at North Island,

San Diego, California.

Standard corrosion penetrameters were fabricated from aircraftgrade aluminum which had been corroded under controlled environments

for predetermined periods of time. The penetrameter samples were obtained form the Naval Air Development Center, Warminster, Pennsylvania.

Two types of penetrameters were employed in these investigations.

The first was fabricated from aircraft-grade aluminum which had

been subjected to a super-saturated saltwater spray for 6.5 hrs. Nominal

step thicknesses were 0.125 in. and 0.87 in.

27
REACTOR RADIATION DIVISION PROGRAMS

The second set of four penetrameters was fabricated from 0.062

in. -thick aircraft-grade aluminum plates which had been subjected to a salt water spray/SO„ gas environment for zero, four, eight and fifteen

days

.

Using a 0.0005 in. -thick vapor deposited Gd converter, we were

able to form the following conclusions.

(1) Salt water induced corrosion signatures in aircraft-grade

aluminum can be visualized with neutron radiography using a 200:1 L/D

ratio. The effect of the 7 in. -thick fin thickness is to degrade the

image quality. However, the signature can still be discerned.

(2) The time required for the exposure was 50 min . for a L/D

ratio of 200:1.

(3) With the penetrameter on either side of the fin, analog edge

enhancement aids in identifying the corrosion signature.

(4) When the L/D ratio is reduced to that of a field system, e.g.,

43:1, the corrosion signature can only be visualized when the penetrameter

was placed on the cassette side of the fin, making it necessary to inspect each side of an airfoil of 7 in. thickness individually.

(5) The time required for the exposure was 90 sec. for a L/D ratio

of 43:1.

(6) With a L/D ratio of 43:1, image edge enhancement aids in

visualizing the corrosion penetrameter when placed on the source side

of the film, however, paint could possibly produce a similar signature.

To compare the results of another conventional direct imaging

method utilizing a gadolinium oxysulfide converter, the following results were obtained.

(1) Corrosion signatures can be visualized using Gd_0_S converters

with the penetrameter placed on either side of the 7 in. -thick fin, using

an L/D ratio of 200:1. The apparent contrast was not as high as that

obtained with Gd foil.

28
REACTOR RADIATION DIVISION PROGRAMS

(2) The exposure time required using a Gd„0„S converter was 15

min. for a L/D ratio of 200:1.

(3) Image edge enhancement aided in identifying the corrosion

signature on either side of the fin with a L/D ratio of 200:1.

(4) When the L/D ratio was reduced to 43:1 using a Gd„0 S con- verter, the corrosion signature could only be visualized with the penetrameter placed between the cassette and the fin. All image detail was eliminated due to geometrical unsharpness when the corrosion penetrameter

was placed on the source side of the fin.

(5) The exposure required 45 sec. to complete.

(6) Edge enhancement did aid in the visualization of the penetrameter when it was placed between the fin and cassette, however,

played little role in the detection of the corrosion signature when

the penetrameter was placed on the source side of the cassette.

A third direct imaging technique was employed utilizing a lightemitting LiF/ZnS converter in conjunction with a light sensitive x-ray

film. This was the fastest imaging technique tested, however, the

experimental results left much to be desired where image quality was concerned

(1) Using a LiF/Zns light-emitting converter in conjunction with

photographic film and a L/D ratio of 200:1, it was possible to visualize

the corrosion signature when the penetrameter was placed between the

vertical fin and cassette. The image quality was so poor however, that

it could easily be confused with the scintillator mottling.

(2) The exposure time required was 5 sec.

(3) When the corrosion penetrameter was placed on the source side

of the fin section, it was impossible to differentiate accurately between the corrosion signature and the background mottling.

(4) Edge image enhancement provided no useful purpose in the

visualization of the corrosion signature with the penetrameter on either side of the film.

29
REACTOR RADIATION DIVISION PROGRAMS

(5) When the L/D ratio was reduced to 43:1, it was impossible to

accurately distinguish between the corrosion signature and the background

mottling with the penetrameter on either side of the vertical fin.

(6) The exposure time required for this radiograph was approximately 0.2 sec. A fourth set of investigations was conducted employing a 0.0001 in.'

thick Gd converter foil in an effort to define the lower limit of

corrosion detectability in aircraft-grade aluminum utilizing reactorbased neutron radiographic procedures. A set of four calibrated cor- rosion penetrameters were fabricated from 0.062 in. -thick aluminum plates

which had been subjected to a salt water spray/SO„ gas environment for

0, 4, 8 and 15 days. Thermal neutron radiographs were made of the seven

in. -thick C-2 vertical fin with calibrated penetrameters placed on the

cassette side of the C-2 vertical fin. As a result of these investigations we concluded that:

(1) In the corrosion radiographs taken of the and 4 day

corrosion penetrameters, the corrosion cannot be distinguished from

the background noise as observed in the edge enhanced inspection. It

is likely that the mottled background noise is due to the neutron

response to the fin paint.

(2) Environment induced corrosion can be observed without image

enhancement in the 8 and 15 day corrosion samples. Image enhancement

serves to render the corrosion images more observable.

Based on the experience gained in these preliminary investigations,

empirical quantification of corrosion appears to be a possibility,

either by isodensity scanning of neutron radiographs and comparison of scans of the corrosion areas with sound aluminum, or by digital image

enhancement techniques. This conclusion is based on the fact that

differences in corrosion density in the penetrameter could be visualized and that a minimum level of detectability could be established with

the plague penetrameters.

30
REACTOR RADIATION DIVISION PROGRAMS

The significant results of these investigations at the NBS may be

summarized conclusively in the following statements.

(1) Environment-induced corrosion in aircraft-grade aluminum can be detected with a high degree of sensitivity with thermal neutron

radiographic interrogation.

(2) The fluence (integrated neutron flux) at the image plane

required to visualize corrosion with conventional imaging methods e.g.,

gadolinium converter in conjunction with a medium contrast industrial

X-ray film at density of 2.5, is approximately 4 x 10 n-cm . Assuming

that a transportable neutron radiography system were capable of producing

4 -2 -1

1.5 X 10 n-cm -sec at a L/D ratio of 40:1, an exposure of 7.2 hrs.

would be required.

(3) At a L/D ratio of 40:1, the corrosion signature of both sur- faces of a thick object, e.g., a wing or airfoil, must be interrogated

Individually. This is due to the fact that geometrical unsharpness

tends to obliterate signature detail on the surface opposite the cassette,

(4) The possibility of corrosion quantification does exist, based

on investigation with standard corrosion plaque penetrameters .

>

(5) Although the use of LiF/ZnS light emitting converters is the

most efficient method by which thermal neutron beams can be imaged, the

results are inadequate for unambiguous corrosion signature analysis.

In light of these investigations we propose that the following

ongoing programs in corrosion detection be initiated, i.e., converter

development, real-time imaging methods evaluation for corrosion detection

and corrosion quantification and standard penetrameter development.

The most efficient light-emitting neutron imaging system in so far

/I as speed is concerned consists of a physical mixture of LiF and ZnS

powders. The components are held in suspension with a binder and settled

on a thin aluminum substrate. The nuclear reaction which takes place is

6 , Li(n,T)a, the tritons and alpha particles producing light in the ZnS

scintillator.

31
REACTOR RADIATION DIVISION PROGRAMS

The neutron radiographic images produced when this type of imaging screen is placed in intimate contact with light-sensitive film is quite

grainy, exhibiting poor resolution. This is due, in fact, to several

factors which include:

(1) The fact that the matrix is composed of powders having a finite grain size. If this grain is too coarse, a granular image will

result

(2) The LlF/ZnS is partially transparent to light generated

within the matrix, making it possible for light generated at one point

to be scattered and emitted at a neighboring site.

(4) Light sensitive films generally tend to exhibit greater grain

than industrial x-ray films.

We propose that a funded R&D program be initiated at NBS to

develop a neutron sensitive scintillating converter which will overcome

the aforementioned problems of the presently available continuous

/I LiF/ZnS thermal neutron imaging screens. Specifically, (1) we propose

f. to size the LlF/ZnS components so that only the finest grains available

are employed to mix the final matrix using a fluorocarbon binder and

(2) to break the initial continuous screen into a myriad of discrete

information centers, or cells in order to eliminate the cross-talk

generated as a result of the light transmission within the scintillator

screen matrix. We have in mind to deposit the converter matrix in

individual cells using chemically milled meshes having cells of approximately 0.0001 in. on a side separated by 0.005 in. walls to minimize

cross-talk.

Pending the outcome of the screen development work, we propose

that an evaluation of state-of-the-art real-time imaging systems be con- ducted for corrosion detection under field conditions. It would be most

cost effective to evaluate the available real-time imaging systems on a lease basis.

32
REACTOR RADIATION DIVISION PROGRAMS

This method has the advantage of speed and high sensitivity,

based on the assumption that a suitable fast imaging screen can be

developed which would provide the required resolution.

The quantification of detectable corrosion could produce an economic

impact on military aircraft maintenance costs. By being able to quantify

the corrosion, it should be possible to predict the time at which a defective area of skin or component should be replaced, rather than re- placement on a preventative maintenance basis.

We propose that several avenues of investigations towards this end

be pursued, e.g.

(1) Automated radiographic image analysis based on the isodensity

pattern comparison with standard corrosion penetrameters or edge enhanced

shadow analysis.

(2) Microchemistry of actual aircraft corrosion samples to aid in

the fabrication of standard corrosion penetrameters.

(3) Subtraction of x-ray data from neutron data to eliminate the

radiographic interferences caused by structural airframe members.

d. Facility Design and Fabrication

The thermal neutron radiography facility design was frozen in

February 1977 and fabrication begun in March 1977. The pneumatically

operated dual shutter mechanism has been completed, however problems

have been experienced in stripper threads on the pneumatic pistons

caused by severe momentum transfer when the 100 lb. shutters are stopped.

The shutter design has been modified so that double acting oil-filled

shock absorbers can be added to the system.

The cart employed to support the exposure cave has been completed.

The exposure cave itself is approximately 80 percent complete.

33
REACTOR RADIATION DIVISION PROGR!\MS

2. Applications

a. NASA Langley Research Center - Neutron Interrogation of ResinImpregnated Graphite Fiber Reinforced Polyimide Composites

Several samples of of resin-impregnated polyimide panels were

submitted by the NASA Langley Research Center for neturon radiographic

interrogation. This material is a high-strength graphite reinforced

composite material that is capable of withstanding temperatures of

approximately 600°F and will be employed for the aft body flap of the

orbited space shuttle.

The purposes of these investigations were (1) to detect resin

depletion in the samples and (b) tc determine the graphite reinforcing

fiber distribution in the composite matrix. Using microdensitometer

scanning of neutron radiographs, it was possible to both detect resin

depletion and in spite of the fact that the base matrix was a long

N-0-CH„ chain, it was possible to discern the carbon fiber distribution.

b. Smithsonian Institution - Thermal Neutron Radiography of Ancient

Lead on Artifacts

The Chinese Yu shown here is a ceremonial vessel made of lead

dating from the Western Chou period, approximately 1,000 B.C. It is

part of the collection of the Hermatage Foundation Museum, Norfolk, Va

.

and is now on loan to the Freer Gallery of the Smithsonian Institution

in Washington, DC.

Members of the Smithsonian brough the Yu to NBS, where Bureau

researchers used it to test their new nondestructive evaluation technique—neutron xeroradiography . The result (original in color) can be com- pared with the photograph and the x-ray.

Unlike x-rays, neutrons can penetrate lead. Thus, the radiograph

shows the mottled areas between the cap and the vessel where corrosion

has sealed the urn. Note too the corroded area near the base. Also

34
REACTOR RADIATION DIVISION PROGRAMS

Figure 1. The Chinese Yu shown here is a ceremonial vessel made of

lead dating from the Western Chou period, approximately

1000 B.C.

Figure 2. The Yu was brought to NBS where researchers used it to test

their new nondestructive evaluation technique - neutron

xeroradiography . The result can be compared with an x-ray

shown on the right.

35
REACTOR RADIATION DIVISION PROGRAMS

visible in the radiograph on the left side is the outline of some material—paper or perhaps fabric —that may have been used in repairing

the vessel. Other repair work can be distinguished without the aid of

neutrons: Near the center, a triangular portion has been patched,

possibly with bronze.

The exact purpose the vessel served and how it was damaged are,

of course, matters of speculation. One theory is that this Yu was made for a burial service as one of the items to be included in the

grave. The damage could have been done by early excavators, possibly

grave robbers, who searched by poking the ground with sharp objects

until they struck metal.

Evidence of corrosion product formation which holds the urn lid

shut can be visualized in the neutron radiograph.

c. Smithsonian Institution - Thermal Neutron Radiography of Wooden

18th Century Harpsichord Lid

A 18th century harpsichord lid was radiographed both with thermal

neutrons and x-rays ranging in energy from 40 pkv to 160 pkv. The

purpose of these investigations was to visualize paint layers and

internal details of the method employed to fasten individual boards together. The results of these experiments may be summarized as follows:

(1) X-radiography could discern paint layers on the harpsichord

with good clarity.

(2) X-radiography permitted visualization of details of the nails

employed to fasten individual boards of the lid together.

(3) The adhesive applied between the individual boards was radioopaque.

(4) The nails were also discernable using neutron radiography,

however appeared to differ in detail from that obtained with x-radiography

(5) Details of artifacts in the wood matrix could be visualized

with neutrons which could not be with x-rays.

36
REACTOR RADIATION DIVISION PROGRAMS

(6) The adhesive employed to glue the individual boards of the

lid was also neutron opaque.

(7) The migration of corrosion products formed on the nail surface

into the wooden matrix could be visualized with neutron radiography.

Subtraction of x- and neutron radiographs also lead to new image

information. However because of stringent demands on available personnel,

it was not feasible to pursue this work further.

d. Smithsonian Institution - Neutron Radiography of a 3,000 Year-Old

Bronze Chisel

A bronze chisel was subjected to neutron radiography in an attempt

to visualize laminations of the bronze employed in the original fabrication. Extensive corrosion product formation on the chisel surface,

however was thermal neutron opaque making visualization of the chisel

matrix internals impossible.

It was determined using gamma-ray spectroscopy on the slightly

radioactive chisel that the base bronze matrix was fabricated from a copper arsenic alloy instead of a copper-tin alloy as one might have

expected.

3. Observations

a. Beam Gamma Contamination and Pair Production

The effect of the high-energy gamma ray contamination in the thermal

column neutron radiography beam was discovered accidently when an image

of a high pressure nitrogen valve was observed in spite of the fact that

no thermal neutrons were present in the beam. It was found that the

intensity of the image varied markedly with cassette entrance window

thickness.

Preliminary experiments were conducted with and without thermal

neutrons in an attempt to determine the nature of this phenomenon.

A number of exposures were made with samples of high atomic number

materials. In all cases, film darkening was observed on those cases in

which a light area should have been.

37
REACTOR RADIATION DIVISION PROGRAMS

A gamma ray spectral examination of the beam was made using lithiun

carbonate to filter the neutrons from the beam with a 3" x 3" NaI(T£)

crystal spectrometer. Well-defined gamma ray photopeaks were observed

to energies as great as 10 MeV, although no attempt was made to correct

the data for detector efficiency. The gamma intensity (under normal

operating conditions) at an L/D ratio was approximately 2R-hr

All indications point to the fact that the observed effects are due to pair production generated in the object under inspection by

gamma rays having energies in access of 1.02 MeV. Final conclusions

concerning the observed phenomenon have not been reached pending spectral

anlaysis of the observed decay products.

38
B. RRU Collaborative Programs

STUDIES of the EFFECTS OF HYDROGEN IN TITANIUM

H. Alperin

(Naval Surface Weapons Center, White Oak, MD)

and

H. Flotow

(Argonne National Laboratory, XL)

and

J. J. Rush

Quasielastic incoherent scattering by hydrogen in titanium metal

can be used to determine the true internal hydrogen diffusion rate.

Neutron time-of-f light measurements on a-Ti and on the same sample

loaded with 'v7% hydrogen at temperatures from room temperature to 540 °C

have been performed. At each temperature, separate runs were also made

to measure the inelastic scattering. Preliminary analysis of the results

indicates that the diffusion of hydrogen in the a-phase is very low.

Experiments have also begun to develop a method to measure residual

stress in bulk samples by neutron scattering. It has been shown possible

to focus on a volume of interest as much as 3 cm below the surface of a specimen. Measurement of strains with a relative sensitivity of

"^2 X 10 has been achieved.

STUDIES ON THE STRUCTURE OF "dEFECT" APATITES

A. Santoro

and

L. W. Schroeder

(Polymers Division)

The interpretation of the results previously obtained on "defect"

hydroxyapatite requires comparison with a well characterized "standard"

apatite. Fluoroapatite (PAP) was chosen because it has been studied

several times by single crystal methods and because a well crystallized

39
RRD COLLABORATIVE PROGRAMS

powder (particle size 3-20 ym) of high phase purity was available.

Powder diffraction data was collected under conditions of high

o resolution; neutron wavelength = 1.518(1)A, Cu monochronator TOA = 74°.

Horizontal divergences; in-pile collimator - 10', beam collimator - 23'

and diffracted beam collimator - 10'. Peak FWHM appeared to be about

15'. The region from 26 = 5° to 100° was scanned in 0.1° steps. Background points were available up to 29 = 90°. A plot of the background

intensity against 26 values Indicated a minimum around 45° and then a slight rise although the variation was barely significant in terms of

counting statistics. Some support for this observation comes from the

fact that refinements utilizing the well known parameters of the apatite

structure and this background did not require an overall temperature

factor.

At convergence the agreement factor was 10% compared to an expected

o value of 7%. All constants agreed within 0.001 A of values obtained

from single crystals of FAP. All positional parameters agree within

2a(a = .0005) of those obtained previously by x-ray diffraction studies.

Table 1 gives values of the isotropic temperature factors obtained in

this study. For comparison temperature factors obtained by neutron

diffraction on a single crystal of hydroxapatite (HA) and by x-ray

diffraction on a crystal of FAP are also given. Table 1 shows, with the

possible exception of B(P), that temperature factors obtained by the

neutron powder profile method are comparable to those obtained by single

crystal methods. The trends in temperature factor, i.e. B(P) is smallest,

B(0) largest, are reasonable for the apatite structure.

As a test of the sensitivity of the method to composition a rea- sonable temperature factor for fluoride was used and the occupancy

allowed to vary. The refined value is 0.176(3); the theoretical 0.166

and the difference is barely significant. This would give 2.1 fluoride

ions per unit cell instead of the stoichiometric 2.0.

In conclusion, these results indicate the neutron powder profile

method is well-suited for the crystal chemical study of apatite powders

provided the sample is well crystallized. It may be applied to non40
RRD COLLABORA.TIVE PROGRAMS

stoichiometric samples and may be expected to give results good to 5%,

Table 1. Isotropic temperature factors for apatites as obtained

by powder profile and single crystal methods. Estimated

standard errors for all methods are 0.01-0.02.

ATOM B(FAP) B(FAP)* B(HA)**

Cal 0.55 0.73 0.66

Ca2 0.56 0.63 0.33

P 0.04 0.34 0.19

01 0.77 0.85 0.30

02 0.65 0.78 0.50

03 0.77 0.99 0.63

F(or OH)*** 0.61 1.2 0.87

(*) From x-ray diffraction studies of single crystals of f luoroapatite

(Mackie and Young, J. Appl. Cryst. 6^, 26, 1973).

(**) From a neutron diffraction study of a crystal of hydroxyapatite

(Kay, Young and Posner, Nature, 204 1050, 1964).

(***)The isotropic thermal factor is a poor approximation of the motion

of the F or OH ion in apatites and this probably accounts for some of the variation among the three studies.

At present, the technique is being used to study a sample of manganese

containing f luoroapatite in order to test the capability of the method

for determining cation distributions.

1. Schroeder, L. W. and Prince, E., "Hydrogen Bonded Dimers in Tin (II)

Hydrogen Phosphate," Acta Cryst., B32, 3309 (1976).

41
RRD COLLABORATIVE PROGRAMS

THE STRUCTURE OF GUANIDINIUM TETRAMOLYBODIMETHYL

ARSENATE MONOHYDRATE

K. M. Barklgia and C. 0. Quicksall

(Chemistry Department, Georgetown University)

and

E. Prince

The title compound, (CN^Hg)^ [ (CH2)2AsMo^O^^(OH) ] -H^O, is one of a new class of heferopoly complexes in which organic groups are linked to

1 2 a heteroatom through stable covalent bonds. ' As part of the continuing

program at Georgetown University to develop and understand these complexes,

3 4 an x-ray crystal structure of the compound was undertaken. ' The results

of the x-ray investigation show that the anion is a remarkably compact

and symmetrical structure which consists of a ring of four alternately

face and edge-shared MoO, octahedra capped by the (CH„)-AsO_ tetrahedron.

o J z z This compound is one of the smallest heteropoly compounds yet reported

and is only the second heteropoly in which face-sharing of octahedra has

been found to exist.

A unique feature of the title compound is the tightly bound, crystallographically ordered proton. Its presence was indicated by stoichio4

metry and confirmed by IR and NMR spectroscopy. Although the x-ray data

did not directly reveal its position, the presence of a water of hydration

2.8A° from the unique basal oxygen suggested that the proton was bound to

this site. In light of the unusual features of this anion, a single

crystal neutron diffraction study was undertaken with the particular aim

of verifying the location of the unique proton.

A total of 4297 reflections were measured to 29max = 106° with a neutron wavelength of 1.22A°. Of these, 3216 unique reflections for

which I >^ 2a (I) were used in the solution and refinement of the structure.

The initial parameters for the heavy atoms were taken as the final

coordinates from the x-ray analysis. The protons were easily found in

the first difference map and after exhaustive least squares refinement,

the final valves of R and Rw were 0.047 and 0.037 respectively. The

final positional and thermal parameters along with their corresponding

42
RRD COLLABORATIVE PROGRAMS

Table 1. Final positional and tttermal panmeters for (CN^ll^ )2l(<:Hj)2AsMo^o^^(nn)i-ii,n

Atom X y '- '^11 ^22 ''33 ''12 ^3 H,

Mol .1718(2) .1156(2) .44591(6) 59(3) 59(3) 5.6(2) -14(2) 29.5(6) -1.4(6)

Mo 2 .3705(2) .1076(2) .35501(6) 51(3) 65(3) 6.1(2) -14(2) 4.0(6) -1.2(6)

Mo 3 .1900(2) -.1993(2) .32033(6) 55(3) 60(2) 6.7(2) 7(2) 4.1(6) -5.0(6)

Mo4 -.0036(2) -.1943(2) .41143(6) 53(3) 56(2) 6.0(2) 10(2) 2.0(6) .1(6) As -.0367(2) .1377(2) .34125(6) 45(3) 60(2) 6.2(2) 10(2) 1.3(6) 1.9(6)

01 .3467(3) .0938(3) .47816(8) 85(4) 149(5) 8.7(3) -28(4) -6.8(9) 3.3(10)

02 .0770(3) .2637(3) .47003(8) 135(5) 7J(3) 8.6(3) -9(3) 12.3(10) 7.0(8)

03 .0721(3) -.0735(3) .46224(7) 74(3) 74(3) 5.5(2) -14(3) 3.8(8) 1 .0(7)

04 -.0302(3) .0655(3) .39415(7) 52(3) 66(3) 5.9(2) 3(3) 3.4(7) .7(7) 05 .2540(3) .2193(2) .39603(8) 74(4) 56(3) 6.8(3) -11(3) 5.5(8) -2.5(7)

06 .2440(3) -.0956(2) .39266(7) 48(3) 67(3) 6.7(3) 0(3) 2.3(8) .6(8) 07 .5414(3) .0766(3) .38839(9) 59(4) 145(4) 9.4(3) -5(4) -1.1(9) -4.8(10)

08 .4124(3) .2535(3) .31929(9) 117(5) 90(3) 9.8(3) -27(4) 13.6(10) 3.4(9)

09 .3775(8) -.0760(3) .31717(8) 58(3) 77(3) 7.6(3) -4(3) 8.4(8) -3.8(8)

010 .1262(3) .0684(2) .31913(7) 50(3) 66(3) 5.6(2) 2(3) 3.2(7) -.1(7)

Oil .1166(3) .2178(3) .26587(8) 119(5) 139(4) 7.1(3) -24(4) 4.8(10) -11.7(9)

012 .2747(3) -.3754(3) .33469(10) 90(4) 74(4) 15.3(4) 11(3) 11.2(11) -3.4(10)

013 -.0050(3) -.2133(3) .34739(7) 47(3) 78(3) 5.9(3) -12(3) 1.7(7) -1.5(7)

014 .0798(3) -.3687(3) .42773(9) 126(5) 66(3) 9.5(3) 3(3) -.8(10) 3.1(8) 015 -.2018(3) -.2193(3) .41540(9) 68(4) 134(4) 9.7(3) -33(4) 7.7(9) -.7(10)

016 .5050(3) .2657(3) .05735(9) 76(4) 95(4) 9.1(4) -5(4) 2.1(10) -.6(10)

Nl .2411(3) .4827(2) .51621(8) 176(4) 117(3) 18.5(4) -55(3) -19.0(10) 2.5(9)

N2 .4646(2) -.4225(2) .56135(6) 138(3) 93(3) 13.3(3) 1(3) -9.2(8) -1.4(7)

N3 .3006(2) -.2261(2) .53206(6) 124(3) 89(3) 13.7(3) -8(3) -7.4(8) .7(7) N4 .4575(2) .0057(2) .23075(5) 101(3) 148(3) 7.0(2) 51(3) 3.1(6) 3.5(6)

N5 .3758(2) .1138(2) .16306(6) 101(3) 192(4) 7.5(2) -6(3) 1.3(7) 11 .2(7) N6 .2291(2) .1511(2) .22256(6) 88(3) 117(3) 10.2(2) 35(2) 1.7(7) .1(7)

CI -.0346(3) .3602(2) .34385(9) 149(5) 55(3) 11.0(3) 29(4) -.6(11) 3.6(8)

C2 -.2212(3) .0614(3) .30747(8) 60(3) 120(3) 8.4(3) -8(3) -2.4(8) 5.3(9)

C3 .3340(3) -.3758(2) .5368(7) 87(3) 91(3) 8.4(3) -22(3) -1.8(8) .7(7) U .3540(3) .0903(2) .20587(7) 68(3) 93(3) 7.5(2) -3(3) 2.2W) 1.1(7)

HI .3303(5) -.1551(5) .4094(1) 89(7) 102(6) 8.2(5) 11(6) 2(2) 3(1) H2 .4982(7) -.1821(7) .4704(2) 229(13) 210(10) 8.8(6) 41(9) 5(2) -8(2)

H3 .5878(6) -.1997(6) .4312(2) 117(8) 168(9) 14.2(7) -31(8) 7(2) 0(2)

H4 -.1281(13) .3937(7) .3592(3) 500(28) 144(11) 43.3(22) 60(15) 79(7) -12(4)

H5 -.0489(12) .4021(8) .3119(2) 608(29) 142(10) 15.5(9) 25(12) -2(4) 2(3) H6 .0613(11) .3985(7) .3604(4) 361(21) 95(9) 55.9(25) 14(12) -91(7) -6(4)

H7 -.2756(8) -.0235(9) .3267(2) 175(11) 316(14) 19.0(9) -108(11) -11(3) 29(3) H8 -.1899(8) .0131(11) .2780(2) 160(11) 513(22) 13.8(8) -93(13) 1(13) -37(4)

H9 -.2987(8) .1528(8) .2996(3) 159(10) 198(11) 34.4(15) 15(10) -43(3) 8(3) HIO .2076(6) .1263(6) .2533(2) 161(9) 207(9) 9.2(16) 82(8) 7(2) 0(2)

Hll .1483(6) .2063(6) .2020(2) 141(9) 173(9) 12.9(7) 42(8) -6(2) 9(2) H12 .3034(7) .1804(7) .1431(2) 160(10) 258(12) 10.2(6) -1(9) -7(2) 19(2) H13 .4780(7) .0894(9) .1530(2) 168(11) 347(15) 10.6(7) 41(12) 14(2) 16(3) HIA .4360(6) -.0217(5) .2621(1) 141(8) 159(8) 6.9(5) 51(7) 5(2) 4(2) H15 .5366(7) -.0561(7) .2158(2) 167(10) 249(11) 9.5(6) 104(9) 6(2) 2(2) H16 .2011(8) .1920(6) .5150(2) 188(12) 158(9) 18.5(9) -4(9) -18(3) 3(2) H17 .3622(8) .1499(6) .5512(2) 212(12) 134(8) 23.9(11) 16(9) -27(3) -11(3) H18 .2628(10) -.5940(7) .5208(3) 344(20) 142(11) 32.5(15) 76(12) -36(4) -3(3) H19 .4965(7) -.5374(6) .5606(2) 189(11) 124(8) 16.1(8) 21(8) -5(2) 5(2) H20 .1565(9) -.4531(8) .4945(3) 268(16) 208(13) 29.1(14) -95(12) -45(4) 4(3) H21 .5427(7) -.3477(7) .5739(2) 160(10) 170(10) 19.5(10) -7(9) 19(3) -4(2)

The form of the anisotropic thermal ellipsoid is exp (R^^h^+p22l<^+S^2'-^+2p^2hk+2B^5h!l+2e23he)

43
RRD COLLABORATIVE PROGRAMS

Table 2. Selected bond lengths in (CN H ) [(cH ) AsMo.O . (OH)] -H yr 4 14

Atoms No. Averaged Type Range

Mo-O 8 Terminal 1.699(3)-1. 719(3)

Mo-0 8 Doubly Shared

by 2 Mo atoms

1.906(3)-1. 941(3)

Mo-O 4 Triply Shared

by 3 Mo atoms

2.252(3)-2.346(3)

Mo-0 4 Quadruply Shared

by 4 Mo atoms

(unique basal)

2.360(3)-2.527(3)

As-O 2 1.704(3);1. 704(3)

As-C 2 1.906(3);1. 899(3)

C-H 6 Methyl .972(9)-l. 060(7)

N-H 12 Guanidinium .961(8)-1. 018(6)

0(6)-]H(l) .991(5)

0(16).-H(l) 1.779(5)

0(16).-H(2) .945(6)

0(16).-H(3) .941(7)

Mean

1.707

1.920

2.290

2.416

1.704

1.903

1.021

.989

Figure 1. Tetramolybdodimethyl arsenate ion,

44
RRD COLLABORATIVE PROGRAMS

standard deviations are presented in table 1.

Figure 1 shows the results of the neutron study. As hypothesized,

proton H(l) is indeed located on the unique basal oxygen 0(6). The

0(6)-H(l) bond distance is .991(5)A° and the hydrogen-bonded distance

of H(l) to 0(16) is 1.779(5)A°. Although a number of oxometallate cotn- plexes have been shown to contain protons by spectroscopic means, this

study presents the first structural data for a proton in these species.

A list of selected bond distances is given in table 2.

1. W. Kwak, L. M. Rajkovic, J. K. Stalick, M. T. Pope, and C. 0. Quicksall,

Inorg. Chem. ,15_, 2778 (1976).

2. W. Kwak, M. T. Pope, and T. F. Scully, J. Am. Chem. Soo.^ 9_7, 5735

(1975).

3. K. M. Barkigia, M. S. Thesis, Georgetown University, 1975.

4. K. M. Barkigia, L. M. Rajkovic, M. T. Pope, and C. 0. Quicksall,

J". Am. Chem. Soc.,91_, 4146 (1975).

5. D. D. Dexter and J. V. Silverton, J. Am. Chem. Soc, 90, 3589 (1968).

6. See, for example, M. T. Pope and G. M. Varga, Jr., Chem. Commim.j

653 (1966).

CRYSTAL STRUCTURE OF TRIAMINOGAUNIDINIUM

NITRATE BY NEUTRON DIFFRACTION

C. S. Choi

(Energetic Materials Division, AARADCOM, Dover, NJ)

and

E. Prince

Triaminogaunidinium nitrate (hereafter called TAG-nitrate)

,

(NH„ .NH) _C.NO„, is a fuel, and is used as an additive for propellants.

The crystal structure has recently been determined by A. J. Bracuti at

ARRADCOM by using x-ray diffraction, but least squares refinement was

not satisfactory, mainly because of very large amplitudes of thermal

motion of the oxygen atoms. This neutron diffraction study was aimed

45
RRD COLLABORATIVE PROGRAMS

w en e CN o PQ

4-1 03a

3

O

!-i &0 m

r-i OJ pq

4-1 03

!-i 4-1 •HC

01 CM ^ i-H

4-1 PQ

M-lO

CO

5-1 01

4-1 en

OJ m

e «

0)

S-i 03CL 4-1 C

<U OJ H 0) •H

• U-l 0) 0)

4-1 !-i 03

!-i >^

4-1 TJ

•H O

d rQ

I O t3 < -H H 60

•H

M-l >J O

QJ cn x:

!-i +-1 Q)

4-1 U-t <u O

e

03 0)

)-i cn

CO O

4-1

0) E

u o

03 !-i 3 M-l a"

cn Id

4-1 4-1

Cfi J-l 03 QJ

(U

03c

•H

i^ 03

m <r

o> 00 CNJ r rH

•

in

CNJ

CO <r

LO in m

1* r 1-1

CN

Csl P3

PQ

in in

I—liHrHi—ii—iro<rc^CNrocNi ^-'^-'^—'^-^~—'"~-'--^^^^-^"—'^~'CX) r~~ rH cN^^<rocNr^.^cN^-~cNoooocJ^

I r-l I I I I CM I l' CN

rHCN —icNCNCNCN^vcmLninin

o^<3^^^^~~^^cNLnooooLno-)r^Oc3^<J•

cN<r<j-~d-in^inr^r~~vr>r^oor^ininin

CN

I—ii—ii—ii—irHcsii—iro<rr^m<r~cr

^oOlnr-~cNlnmo^mcJ^>^ln^-llnoO(^^

CNCNCnojfO<3-rOC^incN<rvO^CNCNC»

rH i-H i-H *.-H iHi-Hi—i-<r<r<rfOfOro

cjNrHoOi—ir-^<ro<rMrofna>r^invDro

cNcncNooc^oororo^rmMDinvjcNcncTN

o

cno

o I—

1

>o 00 ON 00

CN CN CN

>^

CO CN cn CN cn cn CN r~~ ON in vC

ON a^ <i- O O <T I-H 00 00 ON 0-) 00 r^ C7N 00 <r

ON o ON O ON <r r-- ^D r-- cn <r r- 00 r^ vO CN cn <r in Ol in vC ON CN ON o^ I—

1

r-^ CM ON <r eg CN iH CN cn o cn CN .H iH ro o cn cn o o rH

CO CO

CO Csl CO t^ 0^ vO CO

s—

o r-- -d- ON <r vD in Csl o cn in CO .H CO 00 o CO <r O r^ 00 ON r^ CO

00 CO CM 00 CN r^ <r in -d- <t o- O CTN CO in 00

CM CO iH CO CM o in <r o CO CM O in CvJ CO .-1

03 H

o

4-1 o

C\l IS CO in CN CO in

PC 3

.H CN O O

46
RRD COLLABORATIVE PROGRAMS

at completing the structure by determining the hydrogen positions in

the structure, as well as studying the thermal motions of the nitrate

group.

Table 2. Hydrogen bonds in TAG-nitrate.

Bond N-H(A°) H...O(A°) N...0(A°) N-H...O(°)

N(l)-H(l). ..0(1) 1.001(9) 1.847(10) 2.793(6) 156.4(7)

N(3)-H(3). ..0(1) 0.994(10) 1.932(10) 2.864(7) 155.1(8)

N(5)-H(5). ..0(2) 0.981(10) 2.104(10) 3.058(7) 163.6(8)

Figure 1. Interatomic distances in the TAG nitrate molecule.

TAG-nitrate crystallizes in the orthorhombic space group Pbcm,

with cell constants at room temperature, a=8.389, b=12.684, and

o c=6.543A, There are four molecules per unit cell. A total of 875 re- flections were measured within the limiting sphere defined by a maximum

o 2 9 angle of 106° using 1.23A wavelength neutrons. Among these, 613

reflections had observable intensity. All hydrogen atoms were located

by a Difference Fourier synthesis. An attempt to refine this structure

47
RRD COLLABORATIVE PROGRAMS

by means of the conventional method based on the harmonic oscillation

model again failed to give a reasonable fit to the large thermal

motion of the oxygen atoms. To accomodate such large, and therefore

markedly curvilinear thermal motions, the nitrate group was constrained

to have an ideal planar trigonal shape, and its size (N-0 bond length)

and the rigid body motion was refined with the use of third cumulant.

This constrained rigid body refinement converged normally and reduced

the R-indices to wR=0.054 and R=0.058.

The crystal structure of TAG-nitrate is composed of an infinite

network of hydrogen bonds running between the planar ions. The TAG

cation (except the amino hydrogens) lies in the mirror plane. The

nitrogen atom and one oxygen atom of the nitrate anion also lie in

the mirror, while the other two oxygen atoms are symmetrically placed

on either side. Each ion is linked to four surrounding ions with

opposite charge by strong N-H. . .0 type hydrogen bonds (see table 2).

The TAG cation has essentially trigonal symmetry, and the C-N bond

o lengths, as given in figure 1, are about 1.33A indicating partial

double bonding. This is an indication of the resonance structure of

the gaunidinium ion. The N0„ ion also has similar resonating electronic structure, and hence it's true (unconstrained) structure

should be very close to the trigonal model. The nitrate anion undergoes an intense librational motion with amplitude of 20° for one principal axis, and about 6° for the other two axes. The orientation

of the largest principal axis is not perpendicular to the plane of the

group but tilted about 26° in the mirror plane.

THE STRUCTURE OF NH4N3

E. Prince

and

C. S. Choi

(ARRADCOM, Dover, NJ)

Ammonium azide crystallizes in the orthorhombic space group Pmna,

o o o with cell constants a=8.948A, b=3.808A, c=8.659A. The structure,

48
RRD COLLABORATIVE PROGRAMS

Table 1. Selected bond distances and angles in ammonium azide. Corrected distances and angles are determined from the rigid body

model.

Atoms Uncorrected Corrected

N(l)-N(2) 1.168A 1.186(4)1

N(3)-N(4) 1.171A 1.186(4)A

N(5)-H(l) 1.036A 1.073(9)A

N(5)-H(2) 0.998A 1.021(9)A

N(5)-N(2) 2.974A 2.967(3)1

N(5)-N(4) 2.981A 2.974(3)A

H(l)-N(5)--H(l)^ 105.8° 107.2(1.2)

H(l)-N(5)--H(2)^ 110.3 109.6(0.0)

H(2)-N(5)--H(2)^ 109.9 110.2(1.1)

N(5)-H(l)--N(2) 177.6 178.9(8)

N(5)-H(2)--N(4) 177.9 178.2(9)

determined originally by Frevel , consists of two crystallographically

independent, symmetric azide ions bound to the ammonium ions by strong

N-H...N hydrogen bonds. The central introgen atom of each azide ion

occupies a center of symmetry, but one ion lies in a mirror plane,

while the other lies along a 2-fold rotation axis perpendicular to the

mirror plane.

We have refined the structure from single crystal neutron diffraction data. Of 359 independent reflections within the limiting sphere

o defined by a wavelength of 1.230A and a maximum 20 angle of 106° 234

had observable intensities. Using the robust/resistant techniques

2 described previously, an unconstrained refinement gave a weighted

agreement index of 5.5%, and a constrained refinement treating both

azide groups and the ammonium group as rigid bodies gave a weighted

agreement index of 6.0%. It may be that the assumption of rigidity in

the ammonium group is not justified. Table 1 gives selected bond dis49
RRD COLLABORATIVE PROGRAMS

tances in the structure. The N-N bond length in the azide groups is

o 1.186 (4) A, in excellent agreement with the values found in the azides

O of monovalent metals. The N-N distances in hydrogen bonds, 2.974(4)A

o and 2. 967 (3) A, are indicative of unusually strong hydrogen bonds.

1. L. K. Frevel, Z. Krist. 94, 197 (1936).

2. W. L. Nicholson and E. Prince, NBS Tech Note 939, p. 23 (1977).

STUDY OF THE CRYSTALLINE COMPONENTS OF PORTLAND CEMENTS

A. Santoro

and

P . Brown

(Center for Building Technology)

Studies on the crystalline components of Portland cements have

continued during the past year. The first problem at hand has been to

find components sufficiently pure to be used as standards in subsequent

investigations.

A powder sample of 3-2CaO'SiO„ (B-C<^S) has been refined with the

method of total profile analysis to a value of the R factor of 0.05.

This refinement seems to be better than that carried out with x-ray

single crystal techniques mainly because all the crystals used in the

x-ray experiment were twinned. The analysis of this compound is still

in progress.

50
RRD COLLABORATIVE PROGRAMS

BATTERY ELECTRODE STRUCTURE

P. D 'Antonio

(Naval Research Laboratory, Washington, DC)

and

J. J. Rhyne and A. T. Santoro

The basic questions of electrochemical activity, as related to the

atomic arrangement of the active constituents in the electrodes of the

lead-acid battery, are being investigated. The structural information

is being derived from the radial distribution function, which is the

Fourier sine transform of the experimental total intensity after the

1 2 atomic background scattering has been determined and removed ' , and the

3 total profile procedure. We plan to systematically analyze the interatomic distance distribution and correlate structural changes with - electrochemical activity changes as the battery is cycled and its

capacity declines.

The structure of chemically prepared beta-PbO„ has been determined

4 5 by x-ray and neutron diffraction. The alpha modification has only

<^ been studied by x-ray diffraction and we are planning to verify the

3

oxygen parameters using the profile refinement method.

Figure 1 illustrates the advantages of a neutron diffraction ex- periment over an x-ray diffraction experiment when the atomic number of

the atoms present is not very different.

At the top of figure 1 the spatial atomic arrangement of beta-PbO^

is shown with the unit cell outline. The table in the middle of the

figure 1 describes which atom pairs contribute to the first four peaks

in the G(r) curve and lists the coordination numbers (N) . For example,

the first peak is a cluster of the 2.157 and 2.165A distances. The

2.157A distance arises from origin atom Pb(A) and target atoms of type

0(B). There are four of these distances. In addition, two more distances

at 2.157A occur between origin atom 0(B) and target atome of type Pb(A)

,

namely, Pb(A) and Pb(D).

51
RRD COLLABORATIVE PROGRAMS

Figure 1. Beta-PbO,

TOP Spatial Atomic arrangement with unit cell outline.

In the theoretical neutron diffraction (ND) G(r) curve, in the lower

part of figure 1, the first four resolved peaks are numbered.

As can be seen by comparing the neutron diffraction (ND) and x-ray

diffraction (XD) G(r) curves, G(r) (XD) is missing the second and third

oxygen-oxygen peaks due to the fact that the scattering factor for Pb is

about 10 times that for 0, for x rays, whereas only 1.6:1 for neutrons.

As a control and test of the applicability of the radial distribution

procedure, chemically prepared beta-PbO„ was examined by neutron diffraction. In figure 2 we see the calculated G(r) curve for beta-PbO_ using

5

^ the atomic coordinates given by Leciejewicz. The experimental G(r)

1 2 curve was determined from a data reduction least-squares program '

, which determines the scale and shape parameters of the atomic background

which minimize the spurious detail in the inner region of the radial

52
RRD COLLABORATIVE PROGRAMS

G(r)

DISTANCE

r

ORIGIN Pb(A)

TARGET N

ORIGIN 0(B)

TARGET N

1) 2.157

2.165

2) 2.677

3) 3.056

,4) 3.383

0(B)

0(0)

Pb(D)

4

2

Pb(A) 2

Pb(E) I 0(G) I 0(C) 8

0(F) 2

Figure 1. (Continued)

10r

15 20

MIDDLE - Table listing atom pairs contributing to the first four

peaks in the G(r) curves and coordination numbers (N)

.

BOTTOM - Theoretical G(r) curves computed for the atomic arrangement shown at the top of this figure. The ND curve is

predicted for an x-ray diffraction experiment.

distribution curve, where the probability of finding an internuclear

distance is zero. The procedure isolated the interatomic interference

scattering from the total intensity scattered and also determines the

interatomic distance thermal or disorder parameters, and coordination

numbers of the short resolved distances in the sample. The bottom curve

shows the isolated distances after they have been characterized by the

analysis. The agreement between experiment and theory is quite good and

further experiments are being carried out on actual formed and failed

53
RRD COLLABORATIVE PROGRAMS

Figure 2,

TOP - Calculated G(r) for beta-PbO_ using atomic arrangement

shown at the top of figure 1.

MIDDLE - Experimental G(r) for chemically prepared beta-PbO_ from

a neutron diffraction experiment.

BOTTOM - This curve illustrates the resolution that can be achieved

for the short resolved isolated distances in the sample once they are characterized.

battery plates in the hope of correlating electrochemical activity with

electrode structure.

1. J. H. Konnert and J. Karle, Acta. Cvyst. A29, 702 (1973).

2. P. D' Antonio, P. Moore, J. H. Konnert, and J. Karle, Tvansactions

of the American Crystallogrccphia Assooiation^ 13_, 43 (1977).

3. H. M. Rietveld, J. Appt. Cvyst. 2, 65 (1969).

4. A. Tolkalev, Vestnik Leningradskogo Univ. No. 4, 152 (1958).

5. J. Leciejewicz and I. "Padlo , Natunoissenshaften , _49, 373-4 (1962)

6. R. W. G. Wyckoff, Crystal Struatures, Volume 1, pg. 259, second

edition, Interscience.

54
RRD COLLABORATIVE PROGRAMS

A STUDY OF THE PHASE TRANSFORMATION IN TRINITROTOLUENE

S. F. Trevino, C. S. Choi and H. Prask

(Energetic Materials Division, ARRADCOM, Dover, NJ)

Trinitrotoluene (TNT) can be crystalized from the melt into two

phases, an orthorhombic phase and a monoclinic phase. Both phases are stable at 25 °C but upon annealing at 70 °C the orthorhombic phase transforms into the monoclinic. It has been thought that this transformation is the cause of cracking and void formation in castings of munition containing TNT. In the present study, neutron diffraction was used to detect the presence of the two phases in samples cast under

varying conditions. The samples were cast in two containers one a 1 cm diameter aluminum tube and the second a thin wall large diameter (6 cm)

aluminum cup. The orthorhombic phase could be obtained from the melt

only if the TNT was quenched from 85 °C in the melt to 0°C (ice bath) in

'^ 2 sec. One can conclude that in the process of casting munitions,

any orthohombic TNT formed will very quickly transform to the stable

monoclinic and therefore this phase transition is not the cause of the

cracking and void observed. Further studies on samples from actual

munition will be performed.

PHONON DISPERSION CURVES OF KN3 AT 1 BAR AND 6.6 kBAR

N. J. Chesser

and

S. F. Trevino

(Energetic Materials Division, ARRADCOM, Dover, NJ)

The acoustic and low-lying optic modes of KN^ have been determined

55
RRD COLLABORATIVE PROGRAMS

TYPE Eu Azu Biu

I BAR A o o KN

6.6KBARA • .

1.00 0.75 0.50 0.25 0.00 0.25 0.50

(oot) (eco)

Figure 1. Measurements along the [110] and [001] directions for 1 bar

and 6 . 6 kbar

.

using inelastic neutron scattering. Measurements were made along the

[110] and [001] directions at both 1 bar and 6.6k bar. The results

are shown in figure 1. The mode Griineisen constants of several modes

are found to be substantially larger than in KBr and very anisotropic.

A rigid ion model is being formulated in an attempt to reproduce the

measurements

.

AMMONIUM-ION DYNAMICS IN NH4CIO4

N. J. Chesser and H. J. Prask

(Energetic Materials Division, LCWSL, ARRADCOM, Dover, NJ)

Our studies of ammonium-ion dynamics in ammonium perchlorate (AP)

56
RRD COLLABORATIVE PROGRAMS

Figure 1. Temperature dependence of the very low-lying optic mode observed in d-AP, measured at the (0,2,1) zone-center lattice

point.

have continued in two areas: 1) quasi-elastic neutron scattering (QNS)

has been used to re-examine the character and directional dependence of

NH, re-orientations in single-crystal AP in the 80 to 120K temperature

range; 2) dispersion curves have been measured for the first time for

deuterated-AP. In both cases analyses of the measurements are in progress; however, preliminary results are summarized below.

Earlier QNS measurements made with '^ 0.09 cm thick crystals showed

differences in the Lorentzian-component width for momentum transfers

°-l along the three crystallographic-axis directions (iQJ'v^l.SA ). However,

for higher Qs (|q| > 2.6A ) expected differences were not observed. This was attributed to significant multiple scattering. In the present series

of measurements, crystals '^'0.04 cm in thickness were used. Multiple

scattering still lessens the observed differences compared to expected

57
RRD COLLABORATIVE PROGRAMS

10 T I 1 1 1 r "1

1 1 r

0.4 0.2 0.2 REDUCED WAVE VECTOR

04

Figure 2. Partial dispersion curves of d-AP at IIK. The curves are guides

to the eye.

values at higher Qs, but distinct differences are observed. At lower

Qs, both magnitudes of Lorentzian widths and their "degree of anisotropy"

differ from the values obtained with the thicker crystals. Results for

80 and lOOK are compared in table 1.

Because of the complexity of AP (orthorhombic, Pnma, with four

formula units per primitive cell) our dispersion curve measurements

have focused, primarily, on two modes (B^ at 4.2 meV, B„ at 5 . 7 meV

Ig 3g

at r) the temperature-dependence of which was found to be anomalous in

2

earlier Raman-scattering measurements. We have made use of the neutron

3 scattering selection rules formulated by Casella and Trevino to examine

lattice points in deuterated AP at which the modes of interest would be

expected to dominate the scattering. The results for several temperatures

are consistent with the results of the Raman scattering study. In addition, we have observed a very low frequency optic mode (1.5 meV at IIK) not

4 observed in the Raman measurements, the temperature dependence of which

58
RRD COLLABORATIVE PROGRAMS

Table 1. Lorentzian-widths of QNS profiles for single-crystal NH.CIO,

80K lOOK Previous Work Present Rest lts2 Previous Work Present Results

rj(y-axi8) 0.11 + 0.01 meV 0.07 + 0.01 meV 0.20 + 0.02 meV 0.20 + 0.02 meV

FjCx-axls) 0.14 + 0.02 0.12 + 0.01 0.28 + 0.02 0.23 + 0.04

r^Cz-axls) 0.11 + 0.01 0.12 + 0.81 0.31 + 0.03 0.29 + 0.03

1. From Ref. 1; 0.09 cm chick crystals.

2. 0.04 cm thick crystals.

is also anomalous. The fact that the three modes "conserve" energy

among themselves (i.e. E^+E„-E„ = 0) and exhibit similar behavior with

temperature is suggestive of a particularly strong cubic anharmonic

interaction among the three modes. The temperature dependence of the

previously unobserved mode is shown for the r-point in figure 1; partial

dispersion curves are shown in figure 2

1. N. J. Chesser and H. J. Prask, Proa, of Conf. on Neutron Scattering

,

Gatlinburg, TN, (1976).

2. G. J. Rosasco and H. J. Prask, Sol. St. Cornm. 16, 135 (1975).

3. R. C. Casella and S. F. Trevino, Phys. Rev. 6B, 4533 (1972).

4. A peak has been observed in incoherent scattering spectra of

polycrystalline AP at '^^ 2 meV (H. J. Prask and J. J. Rush;

H. G. Smith, M. Nielsen and H. A. Mook; unpublished work).

A SEARCH FOR THE CENTRAL MODE IN LITHIUM TANTALATE

S. F. Trevino

(Energetic Materials Division, AARADCOM, Dover, NJ)

and

J. M. Rowe

Lithium tantalate is a ferroelectric which undergoes a phase

transition at '^^620°C. Penna, Chaves and Porto have reported the

59
RRD COLLABORATIVE PROGRAMS

observation, by Raman scattering, of a very broad ('^4 meV) central

mode whose intensity increases as a functions of temperature until it

disappears at the phase transition. This central mode is only observed

in the (zz) configuration thus corresponding to long range fluctuations

along the z-axis. These observations are interpreted as the first

experimental observation of a Debye-like relaxation in a ferroelectric.

In the present work, a single crystal of LiTaO approximately

cylinderical (10mm diameter, 25mm height) was alligned with the [110] zone axis vertical at the BT-6 triple axis spectrometer. The reciprocal lattice point (0,0,3) which has zero structure factor for Bragg

scattering was used to search for the central mode as a function of q

and temperature. The incoherent elastic peak (at room temperature)

from the Li was used to measure the resolution which was '^l.l meV.

The crystal was maintained at a temperature of 550 °C and energy scans were made at Q's of (-.1,-.1,3), (-.3, -.3, 3), (0,0,2.75) and (0,0,2.25),

There was no sign of a broadened component in any of these scans. We

are not certain as to the source of the central mode observed by the

above authors but it is not due to a phenomenum associated with microscopic long range order. Perhaps very small Q inelastic measurements

might reveal such a mode.

1. A. F. Penna, A. Chaves and S. P. S. ?ovto, Sol. State Comm. 19_ 491

(1971).

60
RRD COLLABORATIVE PROGRAMS

DEFORMATION OF UNIFORM POLYBUTADI ENE

RUBBER NETWORK

C. Han

(Polymers Division)

and

B. Mozer

and

J. Hinkley and H. Yu

(University of Wisconsin, Madison, WI)

In this study, an attempt is made to compare the molecular deformation of a polymer chain in a rubber network with its macroscopic

deformation in order to evaluate the affine postulation of the kinetic

I theory of rubber elasticity.

Uniform polybutadiene rubber networks have been prepared for this

study. This is done by mixing anionically prepared polybutadiene (PB)

with a certain fraction (1-3%) of molecular weight matched perdeuterated

ij polybutadiene (dPB) and end cross-linked in bulk by tri-isocyanate. The

radii of gyration of the same dPB molecule before and after cross-linking

I have been studied. A typical Zimm plot for the mixture (before crosslinking) is shown in figure 1. From this plot, a radius of gyration

2

I <R„ > = 44 + 10 A has been obtained. This can be compared with the radius

I G o —

of gyration of dPB after cross-linking. Our preliminary data indicate

the radius of gyration before and after cross-linking are approximately

<CR ^ > 2 equal (~ G o/<R > '^^ 1) , which agrees with Floy's predication instead

<R 2> 2 of Guth's predication ( G /<R^ > = 2) . G

I The 3% network was then subjected to a unidirectional deformation

in the scattering plane and perpendicular to the incident beam. The 3%

network with 0%, 22%, 43%, and 60% extension ratios has been studied.

An inverse intensity plot for the 22% extension is shown in figure 2.

Our initial data indicate the chain segment deformation is smaller than

the affine prediction of a Gaussian chain.

61
RRD COLLABORATIVE PROGRAMS

c=o

/ f

- 1

1

/

/

/

/

J / 1

^

1 / /

MIXTURE OF

dPB in HPB (3-41

/ 1 /__x 0-0 —_i200.0 300.0 qixio' + CI%|X102

400.0 SOO.O

Figure 1. A Ziiran plot for the mixture before cross linking.

3,000

o /

/

2,C00 3% dPB in HPB (3^) 22% STRETCH WITH

COLLIMATION CORR.

1.000

20 40 60 80

q'xIO"

Figure 2. An inverse intensity plot for a 22% extension,

62
RRD COLLABORATIVE PROGRAMS

SMALL ANGLE MAGNETIC SCATTERING FROM

AMORPHOUS RARE-EARTH IRON ALLOYS

H. Alperin

(White Oak Laboratory, Naval Surface Weapons Center, White Oak, MD)

and

S. J. Pickart

(University of Rhode Island, Kingston, RI)

and

J . Rhyne

The anomalously large small-angle scattering reported previously,

which appears at low temperatures in a sample of amorphous Tb_ _.

_

U . (Jio

Fe„ Qj,„ has been analyzed further. This magnetic scattering below the

curie temperature which is undoubtedly due to some sort of distribution

of small magnetic "particles" (micro-domains) , has an inverse power low

dependence of the intensity on the scattering vector q with an exponent

of 2.4 at 77K. After correction for vertical and horizontal resolution,

-3

the power law becomes q which is the same as that observed previously

for amorphous TbFe„ and TbHo . It is to be noted that this is not the

-4

correct dependence for a distribution of spheres (q ) nor the more

-4

general Porod Law dependence, (also q ) which would be valid for any

shape of particle with random orientation as long as qL>>27T (L = any

particle dimension) . This implies that some dimensions are as small as

o 40A while others are much larger. The actual interpretation is therefore difficult and suggests that no distribution of simple particle

shapes and sizes applies. An appealing possibility is an interconnected

sponge-like arrangement with partially one-dimensional character.

63
RRD COLLABORATIVE PROGRAMS

MAGNETIC SCATTERING IN DILUTE Pd(Fe) ALLOYS

J. W. Lynn

(University of Maryland, College Park, MD)

and

J. J. Rhyne

and

J. I. Budnick

(University of Connecticut, Storrs, CT)

Although pure palladium does not exhibit a magnetic phase transition, the high density of d-states at the Fermi level leads to a large

magnetic susceptibility for the system. The introduction of magnetic

impurities such as iron into a high susceptibility host matrix results in

the formation of "giant-moment" clusters ('\^12y /Fe atom) . In the range

B of concentration where individual clusters do not interact with each

other the system is thought to form a spin-glass type of state at low

temperatures, whereas for higher concentrations a transition to conventional ferromagentism is observed. We have undertaken an investigation

of the magnetic scattering in such a dilute ferromagnetic alloy:

Pd(1.5% Fe) . Preliminary measurements were taken on a polycrystalline

sample '^^1/2 ml in volume, with a measured Curie temperature of T = 65K.

°-l ^ In the small wavevector (Q<0. 3A ) region the observed magnetic critical

scattering was diffusive in appearance both above and below the phase

transition, with the intensity peaking at T - T in a conventional

manner. The wavevector dependence of the scattering at fixed temperature

obeyed an Omstein-Zernike correlation function within experimental

error. No evidence of spin wave excitations was observed at any temperature, although this aspect will be investigated in more detail. Quantitative measurements of the critical and spin wave scattering are now

in progress on a new sample of larger volume.

64

111
RRD COLLABORATIVE PROGRAMS

CRYSTAL FIELD EFFECTS IN THE SUPERCONDUCTOR

^^^ .IS^"" .Zl^^^'Z

J. W. Lynn

(University of Maryland, College Park, MD)

and

D. E. Moncton

(Bell Laboratory, Murray Hill, NJ)

and

W. Thomlinson and L. Passell

(Brookhaven National Laboratory, Upton, NY)

For most superconductors the introduction of magnetic impurities

is very detrimental to the superconducting state since the magnetic

impurities provide spin-flip scattering centers which can break the

Cooper pairs. The most evident effect is a precipitous decrease of the

superconducting transition temperature with increasing impurity concentration. It has thus been particularly intriguing that there are some superconducting materials, notably CeRu„, which readily accept large

concentrations of heavy rare-earth metals substitutionally without

adversely affecting the superconductivity. For example, 'v.35% of the

Ce can be replaced by Ho before the superconducting state is suppressed,

and small concentrations of Ho actually enhance T . On the other

hand, HoRu„ is a ferromagnet with a Curie temperature T of 14 K, and

the substitution of Ce for Ho gradually reduces T . The magnetic phase

boundary as determined by susceptibility and MBssbauer measurements,

however, appears to intersect the region of superconductivity at a finite

temperature, raising the interesting possibility of these two cooperative

phenomena coexisting.

The neutron scattering technique is ideally suited to study the

magnetic properties of these superconductors since the magnetic state

can be microscopically probed without being affected by the screening of

the superconducting electrons. A particularly favorable system for study

is (Ce, Ho )Ru», both because of the large moment of the Ho and because

1-x X 2

the coexistence region has the highest concentration of rare-earth ions

('\^30%).

65
RRD COLLABORATIVE PROGRAMS

Crystal Field Levels

-(2)

8.75 meV

T~l

15.00 meV

.(1

1 1 .25 meV

M

3.75 meV

Figure 1: Crystal field levels for Ho

3+

Our initial studies were on a sample with x = 0.27. The superconducting transition temperature was measured to be 1.6 K, and a Curie

constant of 2.2 K was obtained from paramagnetic susceptibility measure2

ments. Below 'x^A K we observed the appearance of small angle elastic

or quasielastic scattering, indicating the development of ferromagnetic

correlations. These correlations could be described to a first approximation by an Ornstein-Zernike correlation function, with the corre- lation range § (=1/k) increasing steadily with decreasing temperature

o down to 0.5 K, but then saturating at a value of 80 A. There was no evidence in the magnetic scattering of the onset of superconductivity,

and there was no transition to long range ferromagnetic order.

One of the most important characterizations of this system is to

deteirmine the ground state of the 4f electrons of the Ho ion. The

66
RRD COLLABORATIVE PROGRAMS

3+

degeneracy of the J = 8 Ho free ion will be at least partially

removed by the effects of the crystalline electric field, and we may

expect this to be the dominant effect since the magnetic energy is small

('V'0.5 K). CeRu„ and (Ce-Ho)Ru2 form the C15 structure for x $.4. In

this structure the crystallographic point symmetry of the Ho (or Ce) site

is cubic (43m) , with 12 Ru ions as nearest neighbors and four nextnearest neighbors of Ce (or Ho) . Locally the site symmetry of each Ho

ion will be lower than cubic due to substitutional disorder on the Ce

type of site, but since these are next-nearest neighbor (and more distant) sites we Anticipate that the crystal-field splitting will reflect

the cubic symmetry to a first approximation. We may then compare our

3 observations with the predictions of Lea, Leask and Wolf (LLW) for

3+

Ho in a cubic field.

Investigations of the inelastic neutron scattering at low temperatures revealed two transitions from the ground

state at 3.75 meV and 15.0 meV. This is consistent with the LLW

diagram if the LLW parameters | X | '^^1, W X >0. We note that |x| '^1

implies that a triply-degenerate r^ state is lowest, so the ground state

is magnetic. With increasing temperature two additional transitions

appear at 8.75 meV and 11.25 meV. This is only consistent with the LLW

diagram if X M-l, and the appropriate crystal field levels and corres- ponding transitions are shown in figure 1.

Additional measurements were carried out on pure CeRu„ to determine

if any of the Inelastic scattering could be due to the Ce. No crystal

field transitions or magnetic inelastic scattering was detected up to an energy transfer of 35 meV.

Further measurements are in progress on a series of samples with

differing Ho concentration to establish the concentration dependence of

the magnetic correlation range and crystal field splittings, and the

influence of the Ce site disorder on the Ho ground state.

1. M. Wilhelm and B. Hillenbrand, Z. Nature 26a, 141(1972).

67
RRD COLLABORATIVE PROGRAMS

2. J. W. Lynn, D. E. Moncton, W. Thomlinson and L. Passell, Bull. Am.

Phys. Soa. Tl, 339(1976). Measurements of the correlation range were carried out at Brookhaven National Laboratory.

3. K. R. Lea, M. J. M. Leask and W. P. Wolf, J. Phys. Chem. Solids 22,

1381(1962).

EXCITED STATE SPIN WAVES IN ErFe2

J . J . Rhyne

and

N. C. Koon

(Naval Research Laboratory, Washington, DC)

The group of compounds RFe^, where R is a heavy rare earth, crystallize in the close packed Laves phase or MgCu„ structure. These compounds

have high Curie temperatures (>550K) and show extraordinarily large

magneto-elastic interactions. The iron moments are f erromagnetically

aligned, and are antiparallel to the R moment (ferrimagnetic order).

The iron moment as determined from both bulk measurements and neutron

2 scattering on polycrystalline samples shows an anomalous reduction

from the expected 2y„ to approximately 1.6y^. The rare earth moments

have their free ion values. We have studied in detail the magnetic

excitations in the compound ErFe„

.

ErFe„ has 6 atoms per unit cell with the Er atoms arranged on sites

of tetrahedral S3nmnetry and the Fe atoms on octahedral sites. One thus

expects six spin wave branches, one acoustic and five optic. As the

results in figure 1 show, only three of these branches have energies

easily studied by neutron scattering. The remaining three modes (two are degenerate) are expected to have energies of approximately

200-300 meV. The data in figure 1 for spin waves propagating in the

[q,q,o] and [q,q,q] directions at room temperature show isotropic

spectra consisting of (1) an acoustic mode with no measurable anisotropy

energy gap, (2) a very flat optic mode of energy 5.1 meV degenerate with

68
RRD COLLABORATIVE PROGRAMS

the acoustic mode at the zone boundary and (3) a highly dispersive

higher optic mode starting from an energy gap of 8.75 meV. This latter

mode has quadratic dispersion (!ioj=Dlq| ) in the q range shown with

2 3

D = 240 meV-A only slightly smaller than pure iron metal (D = 280

2

meV-A ) and would represent the iron acoustic mode in the absence of rare earth spins and the R-Fe exchange interaction. This mode is shown

0.8 0.4 0.2 0.4

REDUCED WAVE VECTOR (X comp.)

Figure 1. Magnon dispersion of ErFe„ along [q,q,0] and [q,q,q] symmetry

directions. The acoustic mode was measured about the (111)

and (220) lattice reflections, the lower optic mode at (200),

and the higher optic mode at (220) and (222) reflections. The

solid line is the result of a nearest neighbor spin wave calculation described in the text.

over only a small portion of the Brillouin zone due to the very high

energy transfers involved. The vanishing dispersion in the lower optic

mode is a consequence of negligible Er-Er exchange in this compound;

rather the Er simply sits in the molecular field from the iron spins.

69
RRD COLLABORATIVE PROGRAMS

ErFej

(200) CALC. INTENS5 10 15 5 10 15 AE (meV) AE (meV)

(mcV)

.)|jj^|(n),|

6 31

4 78

3 64

5.10

905

8 01

656

4 66

Figure 2

.

(a)

(b)

(c)

Experimental lower optic mode neutron intensities for q=0

Calculated neutron intensities.

Single ion energy levels and transition matrix elements.

Parameters used in the calculation are^B^^ = 3.3 x 10~^meV,

B = 1.5 x 10-^ meV, B,0 = -9.0 x 10

^ 4 o

~~' meV, gy^H ,=5.1 meV ° B exch

At low temperatures the basic spectra remain essentially unchanged,

except for a giant q = gap of 8.3 meV for the spectra taken at lOK.

It was expected that the 8.3 meV gap would simply decrease continuously

as the temperature was raised. The data, however, show that the energies

renormalize very little with temperature. Instead, the modes change in

intensity, coexisting at all measured temperatures except lOK and below,

where the two lowest energy modes vanish. Typical data on the zone center lower optic mode are shown in figure 2a as a function of temperature. At lOK the only transition observed has an energy of 12.7 meV

and a width roughly equal to the experimental resolution. As the

temperature is raised, however, another peak appears which has an energy of about 5 meV and which has a width considerably greater than

the instrumental resolution. At room temperature the peak at 12.7 meV

is much weaker than the one at 5 meV. Data for the acoustic mode are qualitatively similar except that the broadening appears to be some- what greater. The intensity data shown in figure 2a are typical of

those due to crystal field population effects, although in the present

70
RRD COLLABORATIVE PROGRAMS

case the overall level splitting due to exchange is much greater than

that due to the crystal field. Since the q independent lower optic

mode corresponds to localized excitations of the rare earth spins only, our initial attempt at explaining these results was to try to calculate

the scattering intensity for that mode using the independent spin model

assuming that the rare earth spins experience a crystal field plus an exchange field from the iron. The form of the Hamiltonian for cubic

sjrmmetry and a [111] easy axis is

H = ^^A.:U ^-h\- !b,°[0,°-20/2 0,^]^B,0[0,° 4=^ O/^ O/] (1)

where are the Stevens operator equivalents. ^ The term involving

O2 is included because of the spontaneous rhombohederal distortion due

to magnetostriction. For independent spins in the dipole approximation

the cross-section for the crystal field transition corresponding to the zone center optic mode scattering intensity including instrumental

resolution is given approximately by

lCw,T) a I p^[<n+llj In>|^exp[-(co-E +E )^/a^] (2)

where |n> are eigenstates of the Hamiltonian (1) and J is the component

of the total angular momentum operator perpendicular to the scattering

vector, p is the Boltzman population factor, and a is the energy

^

Z

resolution width. Since the eigenstates are almost pure J states, the

only transitions with significant matrix elements are those between

I n> and | n+l>

.

Values of the crystal field and exchange parameters were determined

using a combination of magnetization and neutron data and led to the

crystal field scheme shown in figure 2c. Using equation (2) the

scattering intensity was calculated and is shown in figure 2b. The

calculated curves are remarkably similar to the experimental data of

figure 2a. Examination of the crystal field levels, gives an

71
RRD COLLABORATIVE PROGRAMS

immediate qualitative explanation of the observed data. The separation

between the ground and first excited state is 12.7 meV, much greater

than either the exchange splitting or the splitting between excited

states, which fluctuates about an average value of approximately 5 meV.

The observed low temperature optic mode is sharp because it involves

only one transition. The high temperature lower optic mode, on the

other hand, is significantly broadened because it consists of a number

of excited state transitions with different energies. It is interesting

to note that the transition matrix element from the ground state to the

first excited state is several times smaller than those between the

excited states which produces the observed intensity distribution.

1. A. E. Clark, A. I. P. Conf. Proa. Series 18^, 1015 (1974).

2. J. J. Rhyne, to be published; M. 0. Bargouth and G. Will, Journal

de Physique CI, 32, 675 (1971).

3. H. A. Mock and R. M. Nicklow, Phys. Rev. B7, 336 (1973).

K. W. H. Stevens, Proa. Phys. Soa. London^ Sect. A, 65_, 209 (1952).

MAGNETISM IN ErFe^'H

J. J. Rhyne

and

S. G. Sankar and W. E. Wallace

(Chemistry Dept., University of Pittsburg, Pittsburgh, PA)

The close-packed Laves phase crystal structure compounds R Fe-

(1) (where R is a rare earth) have been shown to absorb hydrogen readily

forming stable hydrides. One such phase has composition near R Fe„H,

.

We have begun an investigation of the compound ErFe^H using elastic

scattering techniques to examine the sublattice magnetization and its

temperature dependence. At low temperature the magnetization does not

72
RRD COLLABORATIVE PROGRAMS

saturate even in fields as large as 120 kOe. This precludes an accurate

determination of the sublattice magnetization from bulk magnetic measurements.

The Curie temperature of ErFe H determined from neutron

experiments is 450K which is significantly depressed from the 574K found

for pure ErFe_. The sublattice magnetization also indicates several

anomalies. At lOK, the Er moment was found to be only 5.5 Bohr magnetons

(y ) which is significantly lower than the free ion value of 9 y^ found

in pure ErFe„ . The Er moment decreases rapidly as the temperature is

raised and is essentially zero at 300K, well below the overall Curie

temperature of 450K.

The iron moment on the other hand is 1.6 y at low temperatures in

agreement with that found in pure ErFe„ and remains essentially constant

up to 350K before dropping rapidly to zero at the bulk Curie temperature.

These results suggest a significant reduction in the Er-Er and Er-Fe

exchange interactions on hydriding lending to a structure in which the rare earth is very loosely coupled. The marked reduction in low temperature Er moment also suggests a predominance of crystal field terms

in the magnetic energy.

1. D. M. Gualtieri, K.S.V.L. Narasimhar, and W. E. Wallace. AIV Conf.

Proc. Series 34, 219(1977).

APPLICATION OF NEUTRON DIFFRACTION TO

NON-DESTRUCTIVE TESTING PROBLEMS

H. J. Prask and C. S. Choi

(Energetic Materials Division, LCWSL, ARRADCOM, Dover, NJ)

and

H. A. Alperin

- (Naval Surface Weapons Center, White Oak, MD)

and

E. Prince

73
RRD COLLABORATIVE PROGRAMS

The Army group at the NBSR has been engaged in a continuing program to use neutron diffraction to determine texture (i.e. grain orientation) in the copper liner component in shaped-charge munitions. The

need for this information arose because of difficulties in procurement

and quality control for these items. Our most recent v7ork In this area

has been directed toward the determination of texture as a function of

depth. In principle, the penetrating power of neutrons and the ability

to adjust incident wavelength continuously permits texture determination

directly as a function of depth in extended samples. However, in the

liner application, the thickness is only 0.28 cm so that a "difference"

method has been developed and tested, which consists of the following.

One makes use of the fact that for a given set of planes, and appropriate

masking, different depths are sampled for different wavelengths, as illusSAMPLING DEPTH VS NEUTRON WAVELENGTH

-(90'-702')

i„_m\M/-

XCAJ ds 0//) ^s^^^OJ

/.2

Z.4-

/C.7°

35.2°

73.8°

28.1°

lO-Z"

Figure lA. Schematic illustrating "difference" technique for texture

vs. depth measurement in shaped-charge liners. The cross- hatched area in each figure (defined by masking with Cd or

Gd) corresponds to the volume examined for the (220) re- flection for wavelengths of 1.2 and 2.4 A, respectively.

The angle a is between the normal to the surface and a vector

perpendicular to the scattering plane. An appropriately

weighted difference of the two measurements should give a rough profile of the pole figure for the lower part of the

liner.

74
RRD COLLABORATIVE PROGRAMS

trated in figure lA (alternatively, the same effect is achieved by ex- amining different order reflections for the same plane)

.

This concept has been tested by examining grain orientation in two

Cu plates each 0.08 cm thick. Texture was determined in each plate

separately, and then together using (111) and then (222) reflections.

The results are shown in figure IB, for 45° £ a £ 90°; <_ & <_ 360°.

The agreement between the pole figures for the bottom plate determined

alone and determined from the difference is reasonable. We attribute

the discrepancies to the fact that optimum conditions (i.e. wavelength

and planes) were not utilized and beam divergence was not taken into

account.

Top Plate

Both Pates Shallow Scan

Bottom Plate

Both Plates Deep Scan

0.032 "Copper Plates

Bottom Plate from difference

Figure IB. Pole figures (45° £ a £ 90°) for two copper plates (each

0.08 cm thick) taken together and separately. In this case

the "shallow" scan corresponds to a (111) pole figure, the

"deep" scan to a (222) pole figure. The heavier contour in

each figure corresponds to "random" grain orientation; the

lighter contours correspond to steps of 50% of random.

a = 90° is at the center of each figure.

75
RRD COLLABORATIVE PROGRAMS

•<

c

'uO

Q.

1 1

1.22370

>

1.22365 "

1.22360^ - -

- L i 2000 4000

Applied Force (lbs)

6000

Figure 2. Change in d-spacing vs. loading for a 6061-T6 aluminum

cylinder (2.54 cm diameter) as measured by neutron diffraction

using the (113) reflection of aluminum. The scattering

geometry was such that the measured change in d-spacing

reflects the radial strain (tensile) in an axially compressed

cylinder

.

In the area of residual stress measurement with neutrons, results

are very preliminary. The principal problem lies in the lower intensity - relative to x-ray sources - of even a high-flux research reactor. This

necessitates relatively coarse collimation to achieve reasonable counting

times. Our initial studies in this area have concentrated on careful

lineshape analysis of Bragg peaks from samples of simple geometry to

which an external load is applied. In figure 2 is shown results for a 2.54 cm diameter Al 6001-T6 cylinder loaded axially, with strains measured radially. The results suggest that the neutron technique may be

sufficiently sensitive to strain as induced by residual stress to have

practical utility.

76
C. NoN-RRD NBS Programs

ACTIVATION analysis: SUMMARY OF 1977 ACTIVITIES

Harry L. Rook and Thomas E. Gills

(Analytical Chemistry Division)

In the Act of Congress which provides the basic authority of the

National Bureau of Standards (NBS), an essential function of the National

Bureau of Standards is the "preparation and distribution of standard

samples and their use in chemical analysis ..." and the "development of

methods of chemical analysis ...". These two functions are basic to the

Neutron Activation Analysis (NAA) program, at NBS. As a part of the

Analytical Chemistry Division, Institute for Materials Research, the NAA

Section has performed numerous measurements that require the systematic

and random errors to be known sufficiently well enough to state the

concentration of an analyte within required uncertainty levels. The

majority of these measurements are in support of the Standard Reference

Materials programs which include the certifications of inorganic and

organic compounds for the chemical composition (major, minor, and/or

Ij trace elements). Congruent to the support of SRM certification, the NAA

Section continually develops or modifies new procedures to insure that

the necessary accuracy is obtained during the certification of SRM's.

In addition to rendering support to the NBS Analytical Chemistry

i Division's program, the NAA Section has made significant contribution to

other agency programs wherein an improved methodology must be developed

or demonstrated. Such interaction mechanism allows the NAA Section and

NBS as well to transfer analytical expertise where needed.

This report summarizes the activities of the Activation Analysis

Section during the period of July 1976-June 1977. Included are contributions in the areas of basic research, applied research, radiochemical

separations, certifications, and non-NBS research programs.

77
NON-RRD NBS PROGRAMS

1. Basic Research in Activation Analysis

a. Fast-Neutron Flux Determination and Optimized Measurement of

Aluminum in High-Purity Silicon

R. M. Lindstrom and R. F. Fleming

Measurement of small quantities of aluminum in silicon of semiconductor

or solar grade is complicated by production of Al-28 by an (n,p) reaction

on the matrix, in competition with the (njy) reaction on the trace Al

sought. In selecting the optimum irradiation facility, the conflicting

requirements of high thermal flux for greatest signal and of low fast

flux for smallest noise must be balanced. The present work outlines a simple experimental procedure for assessing and correcting for interferences. No a priori knowledge of fast fluxes or cross sections is

required; these are often poorly known. The procedure is generally

applicable to other cases of competing reactions.

For a given facility, relatively pure Si and Al monitors are irradiated both bare and cadmium covered. The ratio of observed activity

bare to that in cadmium is determined for each of the two standards,

from which an apparent Al concentration X in absolutely pure Si may be

calculated for that facility. Subsequently, an unknown Si sample is

irradiated bare with an Al monitor and an apparent Al concentration in

the sample (S^ ) derived. The true concentration of Al is then X=X--X . 1 1 o Except for sample weights and the well-determined half -life of Al-28,

all parameters in the calculation are experimental numbers, usually I ratios. Once X has been determined, it need not be done again as long

as the neutron spectrum in that facility is unchanged.

Once the facilities available have been characterized, the optimum

one may be chosen. The "best" measurement is the one for which the

relative error in the concentration X is a minimum. We assume that the

uncertainty in X can be made negligible, by replicate measurement if

necessary. Therefore, if we ignore the half -life uncertainty and assume

that counting statistical error is dominated by the sample and not the

monitor, we can estimate the relative uncertainty in the measurement as
NON-RRD NBS PROGRAMS

a(x) a(x^) a(x^)/x^ l/^/c^

X^-X 1-X /X, 1-X /Z1 o o 1 o 1

where C is the observed number of counts from the silicon sample. For

samples with an aluminum concentration X»X the relative uncertainty becomes 1/v^cT which is proportional to l//(}) for the given irradiation

facility. For samples whose concentrations X<X , the uncertainty quickly

becomes very large. For a given facility, the value of X is proportional ' o to the neutron flux above 4 MeV.

The present method has been used to characterize the pneumatic tube

facilities in the RT4 facility ((j) =1.2x10 -"""^.R =560), X =48±4 yg/g Si,

in excellent agreement with paired irradiations in RT4 and the thermal

column (R =3400), and also in agreement with calculation from the measured

fission flux and the tabulated fission-averaged cross section.

The fission flux has been measured in four rabbit tubes, by irradiating bare titanium and silicon (quartz), counting on a calibrated Ge(Li)

detector, and deriving fluxes from tabulated fission-averaged cross sections (Handbook on Nuclear Activation Cross Sections, Technical Reports

series 156, IAEA, Vienna 1974). The results are as follows:

Fission Fluxes in Pneumatic Tubes

Radionuclide RTl RT2 RT3 RT4 RT5

28a1 2E12 - 1E12 7E10 4E8

29a1 1E12 - 7E11 3E10 - «Sc 2E12 1E13 8E11 2E10 - "so 2E12 1E13 4E11 IE 10 - 'ho 2E12 2E13 3E11 3E10 _

79
NON-RRD NBS PROGRAMS

b. The Quantitative Determination of Volatile Trace Elements in NBS ; Biological Standard Reference Material 1569, Brewers Yeast

H. L. Rook and W. Wolf.

The accurate analysis of chromium in biological samples has historic

ally been difficult. Analytical methods such as atomic absorption spectroscopy and neutron activation have the required sensitivity to determine

nanogram levels of chromium, but reported analytical data on biological

materials, such as NBS Standard Reference Materials (SRM) 1577, Bovine

Liver, has been widely discrepant (1). More recent data has indicated that

the current status of chromium analysis has not greatly improved (2) . It

has been suggested that part of the analytical error may be due to the

presence of a volatile organic species which may be lost upon certain

preparation procedures in samples of biological origin (3,4).

Analytical verification of volatile trace elemental species in biological systems has been, in general, limited. Elements such as mercury

and lead have been shown to form elemental or simple molecular species

which vaporize upon mild thermal treatment. The awareness and confirmation

of possible vaporization losses of other metals, which are not noirmally

considered volatile, is becoming of increasing importance. Two recent

studies have reported no chromium losses during ashing and acid digestion

of biological samples to which radiotracers of Chromium-51 were added (1,2)

A more recent study has reported as much as 30 percent volatilization

loss of chromium from neutron activated brewers yeast samples during

dissolution with concentrated acids (5).

Detectable amounts of six trace elements were observed in trapped

fractions distilled from the brewers yeast. The amount of each element

trapped was dependent upon the maximum temperature to which the sample was heated. The quantity of those trace elements observed was normalized to the weight of yeast used in individual experiments and is given

in table I. The amount of each element in the trapped fraction increased with increasing temperature in all cases except silver. However, the

quantity of the element volatilized and the dependence on temperature

varied among the individual elements

,

80
NON-RRD NBS PROGRAMS

Table I. Trace Elementa1 Loss from Brewers Yeast by ^i^acuum D:LSt xllatio

yg Trapped/Gram Sample (Temperature ''C)

Element 150 190 205 250 295 - 305

Mercury 0.0014 0.006 0.017 0.10 0.055

Selenium 0.0013 0.0027 0.0018 0.036 0.16 0.23

Chromium 0.0028 0.0021 0.0021 0.0050 0.0038 0.0052

Arsenic 0.064 0.060 0.050 0.10 0.22 0.32

Silver 0.0045 0.0005 0.0028 0.0027 0.0010 0.0042

Gold 0.00010 —_— 0.00006 0.00040

The data in table II reflect elemental concentrations in the yeast

residue relative to those in the initial unheated yeast sample. These data

are corrected for total weight loss of material from the sample due to the

vacuum distillation.

Table II. Relative Elemental Composition of Yeast Residue

- - Concentrations Relative to Unheated Yeast - - - Temperature °C

Element 200 265 290 305

Scandium 0.996 1.01 0.992 1.00 1.00 1.02

Iron 1.00 0.983 1.00 1.00 1.01 0.983

Cobalt 1.00 1.00 0.905 1.01 0.910 0.933

Chromium 1.01 0.990 1.06 0.920 1.02 1.06

Mercury . 990 1.01 1.01 1.06 0.74

Selenium 1.04 0.960 1.12 0.64 0.44 0.57

Percent

Weight Loss 7% 22% 39% 32%

The elemental data are given relative to initial yeast concentration

because the absolute trace element content of the SRM Yeast has been

determined only for chromium. Approximately 50 percent of the total

selenium, about 25 percent of the total mercury, and less than one percent of the total chromium content was lost at the 300 °C temperature. This was with a total weight loss from the material of between 30

81
and 40 percent at that temperature. For chromium, these data are consistent with the observed volatility data. Although there was a volatile chromium component observed, the quantity, approximately .003-

.005 yg/g, was within measurement error of the total certified chromium

content in the yeast. For the elements scandium, iron, and cobalt,

which were not detected in the trapped fraction, correspondently no difference was observed in the residue compared to the initial sample.

The analytical portion of the experiment was conducted by non- destructive neutron activation. For analysis, four of the sealed quartz

tubes containing the condensed volatile material were irradiated together

with one quartz tube containing 300 yl of a mixed trace element water

standard. Samples were placed in one irradiation container so that one sample from each different temperature level, from 150-300 °C, were

irradiated together. The samples and standards were irradiated for four

13 -2 -1

hours at a thermal neutron flux of "^ 6x10 n*cm sec . After irradiation,

the samples were allowed to decay for two days to eliminate short halflived radioactivity, and counted on a large volume Ge(Li) detector

coupled to a 4096 channel nuclear analyzer. The samples were then

allowed to decay for two weeks and were recounted to determine those

elements with half lives greater than a few days. The resultant gammaray spectra were output onto magnetic tape and processed off line by

computer code QLN-1. The individual photopeaks were quantified by the

total peak area method. Quantitative results were obtained by direct

comparison of the specific activity of the samples and standards.

In an effort to resolve the question of chromium volatility, a vacuum distillation experiment has been designed and conducted on a new

NBS Standard Reference Material, SRM 1569, Brewers Yeast, which is

certified for total chromium content. The experimental design allowed

for the collection of all volatile species in the range of 150 to 325

°C, and for the quantitative determination of those elemental species

amenable to neutron activation. In addition to chromium, volatile

82
NON-RRD NBS PROGRAMS

losses were found and quantified for the elements Hg, Se, and As. Other

elements such as Br and I were observed to volatilize but were not

quantified due to experimental conditions of the neutron activation.

Sample

Combustion Tube

Figure 1. Vacuum Distillation and Collection System

The basic experimental system is pictured in figure 1. The system

consists of a tube furnace used to heat a 19 mm i.d. quartz combustion

tube containing the sample and a thermometer for temperature measurement.

One end of the quartz tube was enclosed with a standard taper ground

glass removable stopper. The other end was fitted with a second standard

taper joint, the inner portion of which was tapered to an 8 mm i.d.

quartz tube. A 10- to 12-inch piece of similar quartz tubing was fused

to the 8 mm tube. This extension, which was used for collection of the

distillate, was passed straight through a liquid nitrogen trap. The

trap was constructed out of styrofoam with holes bored through the sides

to seal to the collection tube. The collection tube was connected to a vacuum pump with rubber vacuum tubing. A second liquid nitrogen trap was placed between the pump and the collection tube to prevent back

streaming of pump oil vapors and other contaminants.

83
NON-RRD NBS PROGRAMS

1. McClendon, L. T. , "Proceedings VIII Trace Substances Conferences,"

University of Missouri, Columbia, Missouri (1974).

2. Parr, R. , International Conference on "Modern Trends in Activation

Analysis," (to be published).

3. Wolf, W. , W. Mertz, and R. Masironi, J. Agr. Food Chem., 12, 1037

(1974). —

4. Wolf, W. , "Proceedings of 7th Materials Research Symposium," NBS

Special Publication 422, 605-610. U.S. Government Printing Office

(1976).

5. McClendon, L. T. , Radio Anal. Chem. , 8, (to be published).

c. Study of the Chemical Dissolution of Different NBS Environmental

Matrices. Recovery of Cd, As, Sb, Se, and Cr.

M, Gallorini, T. E. Gills, R. R. Greenberg

One of the most important problems in the field of trace elemental

analysis using the nuclear activation technique coupled to radiochemical

separation, is to dissolve the sample easily, completely, and without

losses of volatile elements.

The purpose of this research is to find the most suitable conditions

under which the complete dissolution of all environmental matrices can be

obtained without losses of volatile elements such as arsenic, cadmium,

antimony selenium, and chromium.

Because of different chemical composition of matrices several

methods and techniques of dissolution will be tested so as to correlate

the volatile elements losses with the chemical nature of the matrix.

For this study, a list of the environmental correlated matrices

in different groups with similar chemical composition is grouped. The

following general scheme shows a possible subdivision:

Biological Botanic : Orchard Leaves, Spinach, Pine Needles,

[B. B. matrices] Wheat Flour, Rice Flour, Tomato Leaves,

Brewers Yeast.

84

IB
NON-RRD NBS PROGRAMS

Biological Physiological:

[B. P. matrices]

Biological Tissue : [B. T. matrices]

Environmental Related

Samples

Serum, Blood, Urine.

Tuna Fish, Bovine Liver, Human Tissue,

Oysters

.

Inorganic : Fly Ash

Mixed: River Sediment, Air Particulate,

Coals.

Typically, different matrices may require different dissolution

methods, i.e. different acid mixtures. Teflon bomb, and fusion with

appropriate flux.

Determination of Trace Element:

In order to determine As, Sb, Se, Cd, and Cr losses, a selective

radiocchemical separation is necessary to measure the losses of these

elements after chemical dissolution. After dissolution of the sample,

the next schematic procedure will be followed:

Sample solution in HNO3 ^^

Hydrated Manganese dioxide

Sb As Se Cr

Cd extraction with Zn

Diethyldithiocarbamate

Figure 2. Radiochemical Separation Scheme

85
NON-RRD NBS PROGRAMS

Proposed Study of different dissolution methods:

Biological Matrices

Environmental Related

Coals

Environmental Related

Fly Ash

River Sediments

Air Particulate

1)

2)

3)

1)

2)

3)

HNO_ HCIO,

H„SO, HNO^ Ik 3

HF (3:1:03)

H2O2 HF (5:3:3:0.3)

Teflon Bomb using H^SG,, HNO , HCl, HF

HNO„ HCIO,

J 4

Teflon Bomb

HF

Na^O^ NaOH

Fusion with Pyrosulfate (Bisulfate)

Other

During the dissolution, parameters such as temperature, ratio and amount of

acids, length of attack, fusion in a fused silica tv:be under different gases

will be tested and measured. Using radioactive tracers and standards, re- covery yield will be determined. This work should be valuable to many

procedures currently used in the SRM Certification Program.

d. Determination of Os, Ru, and Hg in Inorganic Matrices and Environmental Samples by Destructive Neutron Activation Analysis.

M. Gallorini and T. E. Gills

Because of the very low concentrations in nature, elements such as osmium and ruthenium have been studied only by geologists and metallurgists

Consequently, the analytical methodology of those two elements must be

developed to determine accurately their concentration in matrices such

as rocks, particular alloys, and as impurities in noble metals (1,2,3).

Recently, the noble metals have been found in many environmental related

materials (such as air particulate and ashes) and their determination

have become very interesting in relation to many environmental problems.

For this research, a method for analysis, at trace levels, of mercury,

osmium, and ruthenium using thermal neutron activation analysis followed

by radiochemical separation has been developed.

86
NON-RRD NBS PROGRAMS

Different kinds of matrices of geological interest, e.g. (rocks

PCC-1, G-2, DTS-1 from U. S. Geological Survey) and inorganic-environmental

materials (Air Particulate, Fly Ash, from the National Bureau of Standards)

were analyzed. Because of the low contents of Hg, Os, Ru, and the

matrix radioactivity from neutron irradiated materials, a radiochemical

separation was necessary. Thus, the dissolution of the very difficult

matrices was required. During sample dissolution procedure, the most

delicate step is to prevent the losses by volatilization of mercury as metal and osmium and ruthenium as tetroxides (4) . A fusion with sodium

peroxide and sodium hydroxide in a quartz tube under particular conI ditions was developed so as to obtain, simultaneously, a quantitative

separation of mercury and an easy dissolution of the matrices followed

by distillation of osmium and ruthenium tetroxides. The general procedure

followed can be subdivided into two subsequent stages:

a. A fusion attack and quantitative separation of mercury. The

samples with carriers and the fusion mixture were carefully

mixed in a quartz boat which was placed in a Vycor tube joined

to a liquid nitrogen cold trap. During the fusion, the mercury

is quantitatively distilled and condensed while the matrix is

completely dissolved.

b. Distillation of OsO, and RuO, : The boat and the melt content

4 4

were then placed in a distillation flask and ruthenium and

osmium tetroxides were distilled from sulfuric acid by the

addition of a sodium bromate solution.

In order to ascertain the quantitative separation of mercury and the

complete retention of osmium and ruthenium during the fusion step, a study using radioactive tracers of Os-191, Ru-103, and Hg-197 was carried

out. The temperature, length of fusion, different kinds of transporting

gas, amount of reagents were tested. The results are shown in table 1.

For the distillation procedure, a similar test using radioactive tracers

was carried out, obtaining a complete recovery of two tetroxides.

87
NON-RRD NBS PROGRAMS

Table 1. Results of a Series of Fusions in Different Conditions

Os Ru Hg Oven

Retent Retent Recovered Temp* Length* Traap. Sample

Z X Z 'C Mln. Gas* g

^^2°2 NaOH

97.82 99.8 100 900

97.97 100 100 850

99.91 100 100 850

99.92 100 100 800 5

99.90 100 100 800 8

*P«Taaetera Beasured during the oven heating phase.

5 Air

5 Air

5 H^

"2

»2

River Sed. 0.367

River Sed. 0.273

River Sed. 0.300

PCC-1

0.380

PCC-1

0.305

2 —

1.5 -

1 0.150

1.2 0.200

1.2 0.200

Conclusions.

In conclusion, this fusion-distillation method is rapid, simple,

and quantitative. It permits the determination of mercury and the

simultaneous control of eventual losses of osmium and ruthenium as tetroxides. Analysis of materials such as rocks, dust, and fly ashes

can be completed in 2-3 hours. Furthermore, accuracy can be achieved

even at the nanogram level.

1. Nadkarui, R. A., and G. H. Morrison, Anal. Chem. , 46_, 2, (1974).

2. Chung, K. S., and F. E. Beamish, Anal. Chem. , 43, 357-368 (1968)

3. Gijbles, R. , and H. Hoste, Anal. Chem.^ 41, 419-429 (1968).

4. Apt, R. E., and E. S. Gladney, Anal. Chem.j, 47 (1975).

88
NON-RRD NBS PROGRAMS

e. Lithium Analysis by Use of Tritons

B. S. Carpenter and L. J. Pilione

A method of lithium analysis is accomplished by allowing alpha

particles from the thermal neutron induced Li(n,a) H reaction to damage

a nuclear track detector which is then chemically etched to enlarge the

damaged region to a size easily discernable in an optical microscope.

The measurement of the etched track density yields information on the

amount and distribution of lithium in the host matrix. Unfortunately,

elements such as boron and oxygen also undergo (n,a) reactions which can lead to serious background problems if they occur in significant amounts

relative to lithium.

Below is a listing the characteristics of the above mentioned

reactions:

Thermal Alpha

Isotopic Neutron Cross Particle

Element Abundance Reaction Section (bams) Energy (MeV)

^Li 7.5% ^Li(n,a)^H 942 2.05

1°B 19.8% •'-°B(n,a)\i 3838 1.41(96%);

1.78(4%)

^^0 . 0A% '^0(n,a)-^^C 0.24 1.41

The damage produced by the B-10 and 0-17 alpha particles is not sufficiently

different from that of the lithium alphas to be easily recognized with the

nuclear track technique. Therefore, unless one can identify the

different alphas a serious error can be made in the determination of lithium.

A technique recently developed at the NBS facilities utilizes the

O

ft

"^ H(trlton) particle from the Li(n,a) H reaction. The lithium-triton is a penetrating particle as compared to the alpha particle and is unique since

thermal neutrons do not produce exothermic nuclear reactions for light

elements where a by-product is triton. The lithium reaction is an exception since the second product particle is an extremely well bound

alpha particle.

This new technique used an absorber between the host matrix and the

plastic detector thus stopping all the alpha particles from reaching the

89
NON-RRD NBS PROGRAMS

plastic detector but allows some of the tritons to pass through with

degraded energies.

The initial studies had to resolve the following related problems:

(a) to find a plastic detector sensitive to triton damage,

(b) to find an absorber free of oxygen and boron and be of sufficient

thickness to stop the alpha particles and allow penetration by some of the tritons.

Two track recorders (cellulose nitrate and cellulose acetate) were

chosen for this study because of their reported ability to register triton

particles. However, it was found that the triton energy needed to damage

the plastics was <_ 0.6 Mev. This critical energy was determined by slowing

down lithium tritons with various thicknesses of absorber and measuring the

triton energy with a solid state detector. The plastic detectors where

then exposed to the different energy tritons and subsequently etched.

It was found that tritons with energies >0.6 Mev did not cause sufficient

damage in the plastics.

This energy constraint placed a range on the absorber thicknesses

from 35-45 ym. Two readily available plastics were used as absorbers: a polycarbonate and a linear polyethylene. The polycarbonate was not free

of oxygen but was available in a wide range of thicknesses. The linear

polyethylene was free of oxygen (<100 ppm) but is currently available in one thickness (25 ym) . Even though the polycarbonate has an oxygen

content the range of the alpha particle

configuration of the system is as follows:

content the range of the alpha particles is <25 ym. Thus the

Host matrix 10 to 20 ym -25 ym -plastic detector:

(Li) polycarbonate linear polyethylene (cellulose nitrate or cellulose acetate)

This combination has been used to successfully form triton images of

Luminum backed LiF targe

NBS glass standard (SRM-961)

.

an aluminum backed LiF target (^0.1 yg/cm ); a 21% Li glass and a

90
NON-RRD NBS PROGRAMS

f. Non-Destructive Determination of Trace-Element Concentrations by

Neutron-Capture y-Ray Spectrometry

D. Anderson, M. Failey, W. H. Zoller, G. E. Gordon and W. B.

Walters (Dept. of Chemistry, University of Maryland, College

Park, MD 20742)

R. M. Lindstrom

Instriomental neutron activation analysis (INAA) , in which one irradiates samples with neutrons and observes yi^a^ys from the radioactive products formed, is a very powerful technique that is capable of

measuring concentrations of typically 30 to 40 elements in complex

environmental or geological samples. However, there are some important

elements that are difficult or impossible to measure even with INAA.

There are several reasons why some elements don't lend themselves

easily, if at all, to INAA: neutron-capture cross sections may be too

small, the products may have extremely short half lives or such long

half lives (or they are stable) that they can't be observed, or their

decay may involve emission of few or no observable yrays.

One of the great strengths of many nuclear methods of analysis is

the fact that matrix effects such as self-absorption of radiations by

the sample are usually negligible, since both the projectiles and the

emitted radiations have very long ranges in the material. Thus, when an element of interest cannot be measured by one nuclear technique it is

often helpful to try a different projectile. For example, some of us,

in collaboration with Dr. George Lutz of the Activation Analysis Section,

developed instrumental photon activation analysis (IPAA) in which one bombards samples with high-energy bremsstrahlung from an electron linac

and observes decay of the products (1,2). In general, one produces a different set of products by (Y,n), (YjP\ etc. reactions than are produced in INAA. We found that IPAA could be used to measure con- centrations of about 17 elements in environmental samples, of which

about half were difficult or impossible by INAA, including Pb, Ni and

Si.

91
NON-RRD NBS PROGRAMS

Even with INAA and IPAA combined, there are still some important

elements that cannot be measured routinely to the desired accuracy,

e.g., Cd, B and S. Therefore, we are investigating the potential of

neutron-capture y-ray spectrometry as a new analytical tool. Instead of

looking at Y-i"ays from radioactive decay, we will observed prompt y-rays

emitted from the samples while undergoing neutron irradiation. It may

make possible the observation of many elements that are not observable

by INAA and IPAA. Take Cd as an example: it has one of the highest

cross sections of any element, but is not usually observable in INAA

114 because most of that cross section leads to stable Cd. However, we

can take advantage of the high cross section by observing prompt y-rays

during irradiation. One of us (William Zoller) observed Cd, as well as Na, CI, B and Gd , in a variety of samples via prompt y-rays in preliminary experiments at Lawrence Livermore Laboratory in 1973. Gladney

et al. have also reported measurements of Cd, B, S, C. N, H, Si, Al, Fe

and Na in various samples (3).

We have designed and are now setting up a system at the NBS Reactor

in order to thoroughly investigate the prompt y-ray technique and, if

successful, to use the set-up for routine measurements on many classes

of samples. We will use a vertical beam tube in the reflector, which

Q

will give a reasonably high flux (^2.2 x 10 n/ cm2 -sec) with good

thermalization (CR.,,~20) and a low flux of scattered y radiation.

AU

Targets will be external to the reactor, which will allow for unusual

sample size and shape, good counting geometry, cooling if needed for

unstable materials, etc. The y-ray spectra will be taken with a Ge(Li)

detector that can be surrounded with a Nal(Tl) anti-Compton shield. The

detectors will be coupled to a computer-based pulse-height analyzer

system capable of storing "singles" spectra Compton-suppressed spectra,

pair-escape spectra, etc. in order to give maximum flexibility for

observing y rays from about 100 keV up to 8 MeV. The analyzer system,

which is programmable, will also be used for reduction of most of the

data.

92
NON-RRD NBS PROGRAMS

The components of the beam facility are nearlng completion. The

beam thimble and shutter inserts, consisting mainly of steel, lead,

boral, borated polyethylene and Li-loaded polystyrene annuli have been

fabricated and/or machined. Only the machining down of a few welds on the outer Al beam tube and the final working of the Hevimet shutter plug

remain to be done before insertion into the reactor, which is scheduled

for 3-5 September 1977.

The beam stop is now being assembled. A large block of (natural)

Li CO„-loaded polystyrene containing Li^CO--loaded polyethylene plug

has been fabricated. A Pb jacket and the supporting structure will be

added over the next few weeks. Aluminum tubing and a slit box have been

obtained for use as the upper beam tube and sample holder.

A TP-5000 pulse-height analyzer system delivered in March, 1977 has

been undergoing de-bugging. The system is built around a PDP-11/34

computer with 80K words of core and uses an LA-34 Decwriter for programming and output, as well as magnetic tapes and discs. Software has

been written which is easily adaptable for complete analysis of singles,

Compton-suppressed and pair spectra. A Nal(Tl) Compton -suppressor

shield has been ordered. Until it is installed preliminary experiments

will be conduced with a smaller suppressor alreadly available at the

University of Maryland. As soon as the system is operational we will

irradiate many pure elements and a wide variety of typical complex

samples in order to explore the capabilities of the method.

1. N. K. Aras, W. H. Zoller, G. E. Gordon and G. J. Lutz, Anal. Chem. ^ 45, 1481 (1973).

2. I. Olmez, N. K. Aras, G. E. Gordon and W. H. Zoller, Anal. Chem.

,

46, 935 (1974).

3. E. S. Gladney, E. T. Jurney and D. B. Curtis, Anal. Chem. , 48 , 2139 (1976); Gladney, Curtis and Jurney, Paper presented at American Chemical Society National Meeting, New Orleans, (1977).

93
NON-RRD NBS PROGRAMS

2. Applied Research in Activation Analysis

a. Standarization of Thin Gold Films

R. M. Lindstrom and S. H. Harrison

A set of seven gold films on silicon substrates have been calibrated for absolute gold content, in conjunction with the surface physics

research group of the California Institute of Technology. These calibrated films are now being used by the Gal Tech group to substantially

improve the worldwide intercomparison of Rutherford-backs cat tering film

thickness measurements.

The gold assay was performed by instrumental neutron activation in

the RT4 position of the NBSR, followed by gamma-ray counting with a Ge(Li) detector. Sources of systematic of error in the procedure were

eliminated or compensated, with the result that the average total error was 0.3%, as determined by independent gravimetric analysis of the

sample set. Bias due to unequal neutron flux for the sample, as com- pared with the standard, was compensated by reversing the rabbit and for

end midway during irradiation; this procedure reduces the longitudinal

flux gradient to less than 0.5%. Matching the weights of standards to

the samples was necessary to compensate changes in counting efficiency

4

due to pileup losses, which may amount to as much as 10% at 10 counts /sec

(25% dead time)

.

The results obtained by activation analysis and by gravimetry are given in the accompanying table. Agreement is excellent.

94
NON-RRD NBS PROGRAMS

A Comparison of Results Obtained by Activation Analysis and Gravimetry

Au Measured (yg)

Sample NAA*

356.3 ± 1.0 355.7 +

Grav

0.7

NAA/Grav

A 1.0017 ± 0.0034

B 835.8 ± 1.6 836.1 + 0.7 0.9996 ± 0.0019

BB 832.4 ± 1.7 834.4 + 0.7 0.9976 ± 0.0019

C 1067.8 ± 2.0 1060.2 + 0.7 1.0072 ± 0.0020

CC 872.8 ± 1.8 878.0 + 0.7 0.9941 ± 0.0022

D 1384.2 ± 2.3 1377.8 + 0.7 1.0046 ± 0.0017

DD 1491.7 ± 2.4 1491.7 0.7 1.0000 ± 0.0017

mean = 1.0007 s = 0.0043

k

Errors quoted for NAA determinations are the standard deviations based

on counting statistics alone.

b. Trace Elements in Solar Cell Silicon

R. M. Lindstom, R. F. Fleming and H. L. Rook

The process by which silicon solar cells are currently made requires

silicon of "semiconductor grade", as a starting material. This high

purity material is very expensive, costing about $70 per kilogram. It

is possible to make solar cells from less pure, therefore less expensive

silicon, but usually the efficiency of the resultant solar cells de- creases as the general impurity level increases.

In an effort to reduce the cost of producing silicon used in solar

cells while maintaining a reasonable efficiency, the Jet Propulsion

Laboratory (JPL) has undertaken a project to define the quantitative

affects of selected trace elements on the conversion efficiency of

silicon solar devices. One fundamental requirement of this project is

the ability to accurately measure trace element concentration at the

13 15

10 to 10 atoms/ ml level. Methods for accurate analyses at these

levels are not presently available for all trace elements of importance.

The NBS program is designed to develop and provide credible analytical

procedures for materials specific to JPL's needs. These procedures

95
NON-RRD NBS PROGRAMS

should provide a mechanism to generate accurate data from all contractor

laboratories. The elements to be included in this study will be Cu, Ni,

Al, Cr, V, Ti, Fe, Mn, Mg, Zn, Sn, and Zr. The established procedures

will be evaluated for the accurate measurements of elemental concen13 15 trations in 10 to 10 atoms /ml range.

c. National Environmental Sample Bank

T, E. Gills, S. H. Harrison and H. L. Rook

The United States as well as many other Nations, has been con- cerned about the potential dangers to human health and the environment

by the ever increasing influx of new man-made substances into our ecosystem. The U.S. Environmental Protection Agency is especially aware

of this situation and is presently studying the feasibility of establishing a program, the National Environmental Specimen Bank (NESB)

,

that would provide a formalized, systematic approach to assess the

environmental impact of these substances at a national as well as an international level.

The concept of the NESB is that of a well defined system of

collection, analysis and long term storage of selected environmental

samples. This system would provide two important outputs. First, the

analytical portion of the NESB will provide real time monitoring data

for pollutant trend evaluation. Second, the specimen bank will provide

properly stored samples for retrospective analysis enabling health

scientists to determine accurate levels of substances that would be

either undetectable or poorly analyzed by today's less sensitive techniques .For an NESB type of system to be of any value, the credibility of

the scientific protocols must be above reproach. Research into analytical

methodologies has been undergoing extensive laboratory testing over the

past three years. The scientific effort is at the point now where it is

necessary to scale up the developed protocols from the "lab-bench"

operation to a modified banking program—the Environmental Pilot Bank.

This pilot bank effort will give the scientists actual working experience through all stages of the banking effort. The specimen

96
NON-RRD NBS PROGRAMS

program would concentrate on a limited number of samples, collected,

analyzed and stored in a central facility. This approach would allow

for strict control and constant evaluation over all operational procedures. Problems encountered in any aspect of the program would

undergo extensive review in order to determine the areas of deficiencies

so that corrective measures may be taken.

The specimen bank concept was recently evaluated at two workshops,

one sponsored by NBS and EPA, the other, an international workshop,

sponsored by the World Health Organization, the Commission on European

Communities and the Environmental Protection Agency. The conclusions of

both workshops were in agreement; that the NESB is a viable concept,

both from the standpoint of need and by the availability of present

specific knowledge. However, it was felt by scientists at EPA and NBS

that it would be premature to initiate a full scale storage and analysis

banking effort until a pilot bank program had been initiated and all

aspects of sample banking had been fully evaluated.

The interaction of the Neutron Activation Analysis Program has

been primarily in obtaining the best possible assessment of proper longterm storage and proper analysis of important samples through accurate

measurement of the trace constituents, a critical need which has mandated

the Section's involvement. The overall research plan or objectives for

neutron activation analysis program can be formalized as following:

(1) Tissue sampling and sample handling techniques will be investigated to insure that during the process of sampling, alteration

of trace components within the sample does not occur.

(2) The development and evalution of tissue storage techniques

has been and will continue to be investigated for short-term and

long term storage. These techniques will minimize changes in

chemical constituents within the sample.

(3) Improved analytical techniques have been and will be developed

for the determination of trace elements of interest in human and

animal tissues. These techniques allow the accurate determination

of trace constiuents of importance to human health.

97
NON-RRD NBS PROGRAMS

(4) The accuracy and precision of the proposed analytical

techniques have been and will be determined on real samples so that

appropriate erv ors may be applied to data in future banking systems

evaluating long-term storage systems. This program is concurrent

with existing research programs in analytical measurement carried

on in the Analytical Chemistry Division, and therefore there is a natural mating of scientific interest within NBS with that of

the EPA.

The benefits of the sample bank research will be most readily

evident in the continuing programs on health related research within

EPA. However, other agencies will have direct benefit from the program,

including the Department of Agriculture and the Food and Drug Administration. The NBS sample bank research will greatly benefit their

programs in assessing the effects of changes in human diet patterns

required in studies over long periods of time.

The main support for this program is derived from an interagency

agreement of support and understanding between the EPA and NBS.

d. Environmental Effects of Used Oils

R. F. Fleming and H. L. Rook

The disposal of used oils has become a significant environmental

problem in modern society. A recent article stated that waste oil from

automobiles and industrial machinery alone accounted for over 40 percent

of the total amount of crude oil and petrolevnn products introduced into

the ocean each year [Science, 194, 791 (19 November 19760]. These used

oils contain high concentrations of inorganic elements and organometallic

compounds from lubricant additives, fuel additives, and wear debris.

Consequently, the deleterious effects on the ocean environment due to

used oils may very well exceed the harmful effects of all other sources

of crude petroleum and petroleum products, including oil tanker accidents

and cleaning operations, all offshore oil drilling and production, and

all natural seepage.

Alternatives of disposal of used oil include: (1) removal of the

decomposition products, additives and contaminants from the used oil to

98
NON-RRD NBS PROGRAMS

allow improved disposition of the concentrated impurities and reuse of the

pertroleum basestock (reprocessing or re-refining) ; or (2) burning of

used oil with minimal or no pretreatment to recover the heat energy,

with concurrent increased production of toxic species which may be

emitted to the environment. Both the above alternatives appear to be an improvement over straight disposal of the used oil in the environment.

However, both of the alternatives also suffer from a lack of basic information on the chemical contaminants of used, virgin, processed, and re- fined lubricating oils including, especially, their source, speciation,

and ultimate fate in the environment.

Neutron Activation Analysis techniques have been developed or modified for non-destructive analysis for a variety of trace elements in

virgin, used, processed, and re-refined lubricating oils. In particular,

correlation of trace element content with chemical speciation is being

attempted in conjunction with other speciation techniques. Efforts to

establish the degree of processing by means of the trace element con- centration will also be made. Finally, preliminary studies will be made

on samples of typical oils in preparation for selecting one or more for

lubricating oil research materials.

e. Radiochemical Separation for Cd

Robert R. Greenberg

A radiochemical separation using the diethyldithiocarbamate (DDC)

ion was adopted for the analysis of Cd. The procedure involves the

extraction of Cd by Zn(DDC)- in CHC1„. Tracer experiments indicated

that this procedure was >99 percent quantitative for a shaking time of

two minutes over a pH range of 1-12.

In addition to Cd, several other elements were found to be ex- tracted by Zn(DDC)^. In some instances, Cu was found to interfere with

the determination of Cd by producing a high background level of radiation.

This problem was eliminated by first extracting with Bi(DDC)„, which

removes Cu. Cd in SRM 1571 (Orchard Leaves) and Atmospheric Particulate

material was determined using an extraction with Bi(DDC)^, followed by

extraction with Zn(DDC)». Good results were obtained.

99
NON-RRD NBS PROGRAMS

In addition to the determination of Cd, several other elements can

be determined using this two-extraction procedure. Preliminary results

indicate that Ag, Cu, and Hg are extracted quantitatively (>99%) by

Bi(DDC)- for a pH of 1, and a shaking time of 30 minutes. This group

separation can also be used as part of a larger multielement analysis

scheme by using an ion exchange resin, such as HMD, prior to the ex- tractions .

3. Cooperative Research Projects

a. Boron Measurements in Silicon using the Nuclear Track Technique.

B. Stephen Carpenter and W. Robert Thurber

In the semiconductor field, boron is used as a dopant to make ptype silicon devices. These devices are usually single crystal of

Czochralski-processed silicon wafers with polished <111> faces. In each

wafer the resistivity is a function of the boron dopant concentration

and homogeneity. Electrical methods of four-probe, metal-oxide-semiconductor, and capacitance-voltage measurements are used for resistivity

and concentration determination of active boron sites and not the total

dopant in the silicon wafers. However, the total boron dopant con- centration and distribution is determined in this study by the nuclear

track technique (NTT) . Silicon wafers with boron concentrations ranging

15 20 -3 over five orders of magnitude, 10 to 10 atoms cm , were analyzed

and correlated with the resistivity measurements . Figure 1 indicates

the extent of the correlation of the results. In addition, comparisons

of the NTT characteristics to other methods of determining boron are given in table 1.

100
NON-RRD NBS PROGRAMS

15 „16 17 18 19 ^^20 21 10 10 10 10 10 10 10

Boron Density (cm~

Figure 1. Resistivity Versus Boron Doping in Silicon Semiconductors.

Table 1. Characteristics of Methods Used to Determine Boron in Doped

Silicon Wafers

^tlechnique

Characteristi^"^^

Secondary Ion

Mass Analyzer

Nuclear Track

Technique

Resistivity

Measurement

Detection Limit

(B Atoms /CM ) lo" lo" <io"

Spatial

Resolution Excellent Good Good

Specificity Excellent Excellent Poor

Quantitation

Requirements

Material

Standards

Material

Standards

R Calibrated Probes

& Irvin-Wagner Curve

Precision 5-10% 2-5% 1%

Accuracy 20% 10% <_20%

101
NON-RRD NBS PROGRAIIS

4. Other Agency Research Programs with Activation Analysis,

a. Nuclear Safeguards - NDA-NRC Research Program.

B. S. Carpenter, R. F. Fleming and H. L. Rook

Current measurement technology is neither accurate nor precise

enough to meet the national (and international) goals of insuring the

safety of fissionable materials. Through this program NBS is to provide

leadership in the improvement of this measurement technology, as well as

to provide the access of standards to transfer this technology. NBS was requested to provide the necessary standards to ensure traceability to

NBS. At the present time there are no SRM's specifically for NDA of

nuclear materials (although a few counting standards may be applicable

in some cases). To provide these, along with the appropriate methodology,

is clearly an NBS role.

The procedure to be used is to establish an NDA counting facility

at NBS and to complete a priority assessment of the needed SRM's.

Following this, prototype standards will be produced and after both

laboratory and field evaluation, certified SRM's will be produced. The

effective utilization of the SRM's will be assessed by providing a Measurement Assurance Program (MAP).

NBS personnel in the Activation Analysis Section are experienced

in state-of-the-art nuclear measurements and in addition are currently

advising on suitable techniques that may be used for NDA. The Section

has extensive experience in the production and certification of a wide

variety of Standard Reference Materials for a wide variety of elements

in a wide range of matrices. Below is listed an outline of NDA safeguard objectives for the coming year:

102
NON-RRD NBS PROGRAMS

(1) Establish an NDA Gamma-Ray Spectrometry System

(i.e., modified Segmented Gamma Scan),

(2) Measure attenuation and absorption coefficients of

various matrix materials,

(3) Design and prepare homogeneous standards - relative to

density (bulk and tap), particle size, etc.,

(4) Design and prepare heterogeneous standards

a) variation of density

b) variation of geometry and configuration

(5) Gamma Scan- Segmented, and Others

a) transmission measurements

b) direct measurements

c) evaluation of gamma/x-ray coincidence

counting,

(6) Study absorption edge measurements,

(7) Investigate limited applications of the nuclear track

technique.

The most urgent transfer of technology will be through the certification of SRM's. Effective utilization of SRM's will be aided by

providing a Measurement Assurance Program for users.

b. Adhesive Bonding of Various Materials to Hard Tooth Tissues

XVII Tracer Study of Mordant Adsorption on Enamel.

T. E. Gills and R. L. Bowen

For improving adhesion between resins and hard tooth tissues, a mechanism has been proposed which calls for chelate bonding of polyfunctional monomers with surface calcium ions or, preferably, with

cations that have higher chelate stability constants. For clinical

utility, the substitution (ion exchange) must be very rapid and re- latively irreversible. The present study evaluated selected metal ions

simultaneously for their sorption (adsorption or absorption) on enamel

103
NON-RRD NBS PROGRAMS

surfaces. The test solution contained 2M phosphoric acid and 1/6 M each

of cupric, zinc, cobaltous, and ferric chloride, spiked with radioactive

tracers. Eight noncarious premolar tooth crowns were cleaned, exposed

to the solution for 60 seconds, rinsed with water, and then dried. The

residual radioactivity was measured to quantify each element sorbed.

The copper ion concentration was as high after a second, extensive

washing as it was before, indicating irreversible adsorption. The

copper was slightly higher than the zinc, and more than ten times

higher than the retained cobalt ions. That these ions can be sorbed

during an etching or "conditioning" treatment from a phosphoric acid

solution is very important to the development of practical therapeutic measures for both restorative and preventive dentistry.

c. The Analysis of Archaeological Obsidian and Geological

Source Sample

M. J. Blackman

The use of trace and minor element profiling to determine the

geological sources of archaeological obsidian is well established in the

archaeological literature. A variety of analytical techniques have been

used, including XRF, AA, INAA, and optical emission spectroscopy. Many

of the studies, while internally valid, have suffered because data has

not been published in concentration units or lacked an indication of the

precision of the analysis. Both of these shortcomings result in the

necessity of duplicating source analyses for each new investigation.

lOA
NON-RRD NBS PROGRAMS

In this project thirty-two obsidian artifacts from the archaeological site of Tall-i Malyan, Iran, and twenty geological source

samples from central and eastern Turkey were analyzed for nineteen

elements by instrumental neutron activation analysis (table 1) . The

objectives of the research

Table 1. List of Elements Determined

Gamma -Ray Energy

Nuclide

Mn

Half-Life

2.587 H

(KeV) Decj

1

ly Time

846.7 hour

2^Na 14.96 H 1368.6 1 hour

«Sc 83.9 D 889.26 14 days

55Fe 45.6 D 1099.22 14 days

8^Rb 18.66 D 1076.77 14 days

i «Zr 65.5 D 756.72 14 days

"^Sb 60.4 D 1690.94 14 days

"iBa 12.0 D 496.37 14 days

"*Cs 2.046 Y 795.84 14 days

"^La 40.22 H 1596.17 14 days

^"Ce 32.5 D 145.44 14 days

"3g^ 46.8 H 103.18 14 days

1"eu 12.7 Y 1408.02 14 days

^ "Sb 72.1 D 879.36 14 days

"5^ 4.21 D 396.29 14 days

"hu 6.74 D 208.36 14 days

"^f 42.5 D 482.18 14 days

l^^la 115.1 D 1221.38 14 days

"3pa 27.0 D 311.9

105

14 days
NON-RRD NBS PROGRAMS

project were: 1) to determine the number and location of geological

sources of obsidian used to make artifacts found at the site; 2) to

evaluate the usefulness of the published source data in the identification of obsidian sources; and 3) to compare the precision and

accuracy of the twenty geological source samples previously analyzed at

the University of Michigan (Keene and H. T. Wright, n.d) and reanalyzed

in this study.

Two irradiations and counting schemes were employed (table 1).

Elements whose nuclides have half lives of less than 24 hours were

determined by irradiating about 20 mg of the samples and standards for

30 seconds in the RT-3 facility of the NBSR. Samples and standards were

allowed to decay for one hour and counted twice for 10 minutes each.

The standards used in the short irradiations were U.S.G.S. rock standard

GSP-1 and NBS SRM 1633 "Fly Ash", Elements whose nuclides had half

lives of greater than 24 hours were determined by irradiating about 100

mg of the samples and standards for 8 hours in the RT-3 facility.

Samples and standards were allowed to decay for 14 days and counted for

100 minutes. The standards used in the long irradiations were U.S.G.S.

rock standards AGV-1, GSP-1, and BCR-1, and NBS SRM 1633 "Fly Ash".

The concentration of each element was determined by taking the mean of the standard values was determined by the counting statistics

or the standard deviation of the mean of the standard values, whichever

was the higher.

The artifacts could be assigned to one of five compositional

groups consisting of two or more members, representing five separate

sources (table 2). Three samples did not fit well into any of these

groups and therefore may represent three additional sources. Caution

should, however, be used when postulating a separate source based on only one sample.

Comparison of the artifact groups with the analyses of the

geological source samples allowed artifact group A (table 2) be assigned

to the Nemrut Dag obsidian source (table 3). The remaining four artifact groups and the three unassigned samples could not be identified

with any of the six geological sources availabe for analysis. Attempts

106
NON-RRD NBS PROGRAMS

to compare the results of this project to published obsidian source data

proved unsuccessful.

The work of Renfrew et al. (1966 and 1968) employed optical

emission spectroscopy. The set of elements determined in these studies

was, therefore, somewhat different from those determined in this project. Where the same elements were reported (Ba, Zr, La, Rb , and Fe)

lack of statement of the precision in the Renfrew et al. analyses

hampered comparisons. In the other major published work (G. A. Wright,

196), although instrumental neutron activation analysis was the an- alytical technique used, only a limited number of elements were reported

in concentration units. The remainder of the elemental data was given

as ratios of counts. This method of reporting data made meaningful

comparisons impossible.

Table 3. Concentration Data for Source Sample SND/105/521

Element

This Study

(ppm)

0.35 ± 0.02

Keene and Wright

(ppm)

So 0.32 + 0.02

Fe 24376 + 245 24987 + 299

Co not detected 1.89 + 0.25

La 110.3 + 1.9 94.9 + 1.5

Sm 20.0 + 0.9 19.4 + 0.2

Yb 14.8 + 2.4 2.3 + 1.9

Lu 2.25 + 0.16 3.26 + 0.91

Hf 28.4 + 2.1 22.9 + 1.6

Ta 5.01 + 0.62 5.26 + 1.03

Th 31.7 + 1.5 33.9 + 2.0

Na 41890 + 801 38477 + 158

The geological source samples analyzed in this study were part of

a group of source samples analyzed at the University of Michigan and

reported by Keene and H. T. Wright (n.d.). The two studies compare

favorably in precision and accuracy for most elements, however, there

are some discrepancies (cf Table 3 for an example). Cobalt, reported in

107
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Table 2. Obsidians: Malyan Artifact Groups (given in ppm)

Croup

QUO.) Sc

0.008

Hn Sigma Fe Sigma Rb Slgaa Ma Sigma Zr Slsna Sb Sl^ma

A (18) 0.241 — — 21121 986 223.3 8.4 38331 412 943.0 110.3 1.32 0.14

B (2) 1.95 0.03 456.0 26.7 5301 101 181.4 5.4 31413 9 165.8 13.4 0.275 —

e O) 0.533 0.019 459.7 14.1 16532 828 118,7 4.7 37547 67 599.8 73.5 0.428 0.057

) 2.56 0.22 307.2 15.5 13494 902 227.0 19.1 36033 380 311.9 69.0 0.932 0.043 K (3) 2.07 0.10 552.4 14.9 10045 562 198.6 8.2 36939 365 233.4 25.5 0.422 0.068

S«pl« Sc Sigma Mn Sigma Fe Sigma Rb Sigma Na Sigma Zr Sigma Sb Sigma

003« 3.33 0.23 571.4 ~~ 8858 435 153.0 17.43 29814 — 224.0 26.1 0.438 0.085

012 1.76 0.10 510.6 16528 511 122,9 14.04 35120 — 390.3 32.2 0.611 0.105 026 0.182 0.017 — — 25825 1883 231.6 19.3 — — 962.7 54.8 2,32 0.136

Croup Ba Sigma Cs Sigma La Sigma Ce Sigma Sa Slgna Eu Sigma Tb Sigma A (18) 84.1 26.8 8.77 0.89 100.4 1.8 194.5 18,3 21.16 1.23 0.486 0.047 4.03 0.52

B (2) 121.7 7.0 3.83 0.28 40.3 1.8 57.6 6.1 2.75 0.10 0.205 0.010 0.260 0.059 C (3) 681.3 7.8 1.53 0.15 81.5 3.0 172.7 10.3 18.64 0.33 2.66 0.05 4.04 0.92

(3) 509.3 15.7 11.93 0.53 47.8 1.9 78.0 9.2 , 7.31 0.95 0.493 0.047 0.846 0.163 K (3) 171.1 45.4 11.24 0.39 37.4 2.6 71.4 4.7 8.81 1.33 0.436 0.030 1.73 0.10

Saaplc Ba Sigma Ca Sigma La Sigma C« Sigma Sm Sigma Eu Sigma Tb Slgna 003* 517.0 34.12 6.10 0.38 35.8 1.15 63.1 7.68 3,92 0.19 0.561 0.041 0.693 0.137 012 723.3 51.2 1.54 0.06 110.1 3.23 196.8 23.94 17.94 0.84 2.132 0.116 3,76 0.745

026 140.7 13.5 17.23 1.55 110.5 4.0 192.6 10.77 22.24 2.51 0.652 0.037 4.61 0.482

Croup Tb Sigma Lu Sigma Hf Sigma Ta Sigma Th Sigma

t. (18) 14.94 0.77 2.28 0.15 25.13 3.24 4.36 0.35 27.20 0.73

B (2) 1.92 0.04 0.339 0.006 4.37 0.25 2.64 0.00 33.33 0.68

C (3) 12.08 0.31 1.85 0.14 19.69 2.41 8.37 0.89 17.46 0.57

» (3) 4.31 0.10 0.701 0.029 8.24 0.77 1.73 0.19 26.73 1.20

I (3) 6.53 0.56 1.04 0.073 8.30 0.30 2.57 0.20 24.53 0.36

Savpl* Tb Slgaa Lu Sigma Hf Sigma Ta Sigma Th Sigma 003a 3.08 0.58 0.527 0.062 3.43 0.85 3.51 0.34 14.94 1.36 OU 10.15 1.84 1.50 0.129 15.37 2.39 8.47 0.81 19.93 2.08 026 16.41 2.74 2.53 0.30 24.69 1.93 4.08 0.28 34.48 2.67

the Keene and Wright analyses, was not detected, and the lanthanum and

sodium concentrations were significantly higher in this study. Work is

presently underway in an attempt to explain these differences

.

108
NON-RRD NBS PROGRAMS

5. Standard Reference Materials Certification Program in Activation

Analysis

a. NBS Food Grain SRM (Rice and Wheat Flour)

H. L. Rook, T. E. Gills and M. Gallorini

Increasing concern with possible toxic trace elements in the food

chain plus growing recognition of the importance of a number of trace

elements in nutrition makes the accurate determination of these trace

elements essential. The National Bureau of Standards is an interagency

agreement with the Food and Drug Administration are in the process of

developing and certifying certain elements in food grain as part of

their Standard Reference Materials Program. These SRM's Rice and Wheat

flours, will allow the FDA to trace the results of their district and

regional laboratories to SRM's in support of their regulatory programs.

This will increase accuracy, and hence the comparability of these

analyses

Neutron Activation Analysis was used for both the homogeneity

testing and certification analysises of those SRM's. Both destructive

and instrumental NAA using radiochemical separations were used for

analysis

b. Surveys of Proposed SRM's by Instrumental Neutron Activation

Analysis

R. R. Greenberg

Surveys of four proposed SRM's were performed to determine the

approximate levels of various elements in these materials, and to

determine which of these elements could be certified using this technique. The proposed SRM's included oil shale, urban atmospheric particulate material and two different coals. Approximate concentration of

elements having intermediate or long-lived neutron irradiation products were determined using primary standards and SRM 1632 (Coal). The

elemental concentrations used for SRM 1632 were the certified values and

those appearing in the literature . The results of these surveys are listed in table 1.

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Table 1. Approximate Concentration (yg/g unless % indicated)

Eastern Western Oil Air SEM

Coal Coal Shale Particulate 1632

Na(%) 0.089 0.22 1.6 0.42 0.040

K(%) 0.39 0.12 1.0 0.95 0.27

Rb 30 63 52 20

Cs 2.2 0.012 3.4 3.4 1.4

Ba 140 73 540 920 330

Br 56 0.76 510 19

Sc 5.9 0.53 4.6 6.6 3.7

Cr 35 2.4 32 400 20.2

Fe(%) 1.1 0.20 1.8 3.8 0.87

Co 6.3 0.53 9.0 18 5.6

Zn(%) 0.45

As 9.1 0.35 64 110 5.9

Se 2.4 0.79 3.5 25 2.9

Ag 6.4

Cd 71

Sb 0.52 0.12 2.8 45

La 16 1.7 20 38 11.3

Ce 30 2.9 34 55 20.4

Sm 2.6 0.23 2.5 4.0 1.83

Eu 0.55 0.058 0.52 0.83 0.38

Tb 0.45 0.22

Yb 0.91 0.15 0.85 1.6 0.70

Lu 0.19 0.030 0.18 0.29 0.14

Hf 1.7 0.22 1.5 4.4 0.95

Ta 0.34 0.34 0.30 5.9 0.21

W 4.9

Th 4.4 0.52 4.7 7.4 3.0

As Received (not dried)

.

Reference values used.

110
NON-RRD NBS PROGRAMS

c. SRM-Na in Bovine Serum

S. H. Harrison

The objective of this work was to determine the concentration of Na

in the proposed SKM-Na in bovine serum to an accuracy and precision of

less than 0.6% relative. Instrumental neutron activation analysis

(INAA) is not routinely used for high accuracy and precision analyses.

However, for carefully chosen matrices, INAA has been shown to be

capable of the accuracy and precision desired in this study (1) . Before

the actual analysis of the proposed SRM Na in bovine serum, it was necessary to demonstrate that this matrix could be analyzed to produce

the desired statistical criteria. The precision was demonstrated by

analyzing 13 samples from a pooled lot of bovine serum for the relative

24

A ( Na)/g soln. The results showed that precisions of 0.5% or better

could be achieved.

To assess the accuracy, the primary solution standard made from

NBS-SRM 919 NaCl was used to analyze to other standard solutions, one made from NBS-SRM 40h Na^C^O, and the other from a commercial source of Ilk

high purity NaCl. The relative difference between the experimentally

determined concentration of the sodium oxalate solution and the gravimetrically calculated value was ^0.4%. For the high purity NaCl standard solution, the relative difference between the experimentally

determined concentration and the gravimetrically calculated value was

^0.2%. Potential sources of error from a sample and standard preparation,

irradiation and counting were investigated during the course of the

experiment. Finally, the SRM-serum with nominally 3000 yg/g Na was accurately analyzed for Na content on duplicate samples of six bottles.

d. SRM's for Water Pollution Program

H. L. Rook and L. T. McClendon

The national effort in water pollution abatement involves municipal

and state government agencies, industries, water suppliers, and nearly

every department of the federal government. Although all industry and

government have been engaged in water pollution measurement since the

previous century, added urgency has resulted from the passage of the

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NON-RRD NBS PROGRAMS

Federal Water Pollution Control Act Amendments of 1972 (P. L. 92-500)

and the Safe Drinking Water Act of 1974 (P. L. 93-523). The later

legistation (P. L. 92-523) set limits on the concentration of some trace

elements in water. Thousands of analyses for trace inorganic elements

in water are performed annually, both by governmental and industrial

laboratories. However, due to the lack of standards, many of these

analyses are of questionable accuracy, casting serious doubts on the

intercomparability of data between laboratories. Without accurate

measurements, scientists cannot relate health efforts to levels of

pollution correctly, engineers cannot assess the effectiveness of control

techniques correctly, and regulatory agencies cannot relate levels of

pollution effluents with ambient water quality correctly, nor can com- pliance with water pollution regulations be fairly and equitably tested.

The National Bureau of Standards (NBS) was asked (by the Environmental Protection Agency) to develop a multi-element in water Standard

Reference Material (SRM) which would consist of 16 trace elements and 4

major elements and be representative of trace element concentrations

found in the natural environment. Additionally, the NBS was asked to

develop an industrial sediment SRM for testing the methodology of 16

elements and selected bulk properties in polluted water sediments.

These two materials will make it possible to evalutate the accuracy of

methods for the elements certified in the presence of interfering

substances.

Two different analytical methods were used: instrumental neutron

activation analysis (INAA) for the determination of some elements (Na,

K, Mn, Al, V and As) and a "semi-destructive" neutron activation technique (DNAA) for other elements (Cu, As, Co, Mo and Cr).

1. Multielement, instrumental

a. Short Half -Lives

Vandium was determined ins t rumentally. Approximately 6 gram

samples of the water were placed in precleaned polyethylene vials.

Standard solutions of vandium were made by dissolving the metal in high

purity acid and diluting to volume with high purity water. Standards

112
NON-RKD NBS PROGRAJIS

were then packaged in same manner as samples. Each sample and standard was irradiated for 60 seconds in RT-3 of the NBSR and allowed a constant

three minute decay. This decay period allowed the analyst time to

transfer the samples into clean counting vials and positions on the 66

ml Ge(Li) detector system for assaying. Data were recorded on magnetic

tape and quantified using QLN-1 computer program.

b. Medium Half-Lives

Manganese, sodium and potassium were determined simultaneously.

Approximately 1.5 gram samples of the water were placed in polyethylene

bags, and the air evacuated. Four samples and one standard were placed

in a "rabbit" and irradiated for 30 minutes in RT-3 of the NBSR. The

samples were allowed to decay for five hours to minimize short-lived

activities. The samples were transferred to petri dishes, post-weighed

and counted on the 75 ml Ge(Li) detector-automatic sample changer

system. Data was recorded on magnetic tape and quantified using the

QLN-1 computer program with the exception of potassium which was hand

calculated.

2. Multielement, radiochemical separation

High levels of gold, sodium and arsenic made it difficult to

determine other elements of interest in the water sample without some radiochemical separation. Therefore, a procedure using a multiple

inorganic ion exchange technique based on work by Girardi, et. al., and

further developed in this laboratory by Gills, was adopted to separate

elements of interest in the water. The procedure was as follows:

Standards and samples were double sealed in polyethylene bags, irradiated for 1 hour in RT-3 and decayed 8 hours. The samples were postweighed into 100 ml beakers five milligrams of appropriate carriers

added, 5 ml concentrated HCIO, added and heated to near dryness.

Samples were allowed to cool and 5 ml of 6M HCIO, added to each column

4

mounted in series. Two 10 ml portions of 6M HCLO, was used to wash

4

columns. Copper and gold are retained on the CUC column. As and

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NON-RRD NBS PROGRAMS

Mo on the TDO column and the remaining elements in the effluent. The

effluent was allowed to decay for an additional seven days to reduce Na24 activity and then counted on the 75 ml Ge(Li) detector system.

The results for those elements determined using INAA are shown in

table 1. The results for those elements determined using radiochemical

separation are shown in table 2. Arsenic and zinc will be re-determined

in the water samples and the results reported at a later date.

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Table 1. Elemental Concentrations in Low-Level Multielement Water

(INAA) yg of Element /Gram Water

Spl Na K Mn V

1001 A 10.052 1.871 0.0306 0.0500

1001 B 10.155 1.813 0.0301 0.0510

1078 A 10.319 1.758 0.0300 0.0510

1078 B 10.473 1.745 0.0306 0.0507

1121 A 10.120 1.810 0.0296 0.0512

1121 B 9.971 1.803 0.0303 0.0509

1186 A 10.269 1.858 0.0295 0.0510

1186 B 10.427 1.928 0.0297 0.0506

1228 A 9.879 1.831 0.0299 0.0501

1228 B 9.926 1.878 0.0297 0.0503

10.159 1.829 0.0300 0.0507

X

± 0.028 ±0.056 ±0.0004 ±0.0004

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NON-RRD NBS PROGRA>IS

Table 2. Elemental Concentration in Low-Level Multielement Water

(xvr/separation) .

lig of element /gram water

Spl Cu As Co Mo Or

1001 A 0.0167 0.0707 0.0186 0.100 0.0141

1001 B .0171 .0711 .0184 0.099 .0150

1078 A 0.0174 0.0703 0.0198 0.100 .0156

1078 B .0168 .0702 .0184 0.105 .0148

1121 A 0.0160 0.0707 0.0181 .0140

1121 B .0715 .0184

1186 A 0.0168 0.0695 0.0184 0.099 0.0146

1186 B .0164 0.0690 .0182 .0155

1228 A .0164 0.0735 0.0186 0.099 0.0147

1228 B .0163 .0710 .0184

X

0.0166 0.0707 0.0185 0.100 0.0148

±0.0004 ±0.0012 ±0.0005 ±0.002 ±0.0006

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NON-RRD NBS PROGRAMS

e. Analysis of Copper Benchmarks SRM's

G. J. Lutz

In response to industrial needs for standards for determination of

trace elements in scrap copper, which is to be recycled, NBS has prepared a series of eleven copper "Benchmark" Standard Reference Materials

(SRM's). Using instrumental neutron activation analysis, it is possible

to determine in many of the samples, selenium, chromium, silver, zinc,

antimony, cobalt and iron, the activation products of these elemtns

being long lived and hence measurable after Cu-64 (t ,„= 12.9hr) has

decayed to low levels

.

Since the matrix in all cases is copper and the samples only vary

in trace element composition, a different approach to their analysis was

taken. Only the first group of the series was analyzed by primary

methods, i.e., those known or assumed to be reliable for the seven

elements. This group is then used as a standard for the other ten with

an enormous saving of effort.

These standards are available in both rod and chip form. A major

consideration in the analysis is homogeneity of the various constituent

samples of each group of the series. We are conducting homogeneity

testing for the seven elements in approximately 150 samples. Duplicates

are run on each of the these rod and chip samples. The variance of

value obtained for the duplicates is statistically compared with the

variance of the individual component samples of each group. The use of

automatic sample changers in gamma ray counting and computers for data

reduction keep the time involved for these determinations within

reasonable bounds.

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NON-RRD NBS PROGRAMS

6. Multielement Standard in Neutron Activation Analysis

a. Preparation of Multielement Standards for Instrumental Neutron

Activation Analysis

R. R. Greenberg

For accurate instrumental analysis it is essential to have good

standards. Concentrated stock solutions of each element were prepared

from pure materials. A small portion of each solution was irradiated

and counted to check for contamination. Contamination of one element

with a second element to be used in the same multielement standard is

especially significant. While preparing these standards, the concen- tration of Cs in one bottle of high purity RbCl was found to be com- parable to the amount of Cs required for the standard. This bottle of

RbCl was therefore rejected and another Rb compound was used. Various

multielement standards were prepared in the following manner. Appropriate amounts of the stock solutions were combined to form various mixed

standard solutions. These solutions were then pipetted onto Whatman 41

filters and allowed to dry. The blank values in the filters were

determined and the standards checked by analyzing SRM 1632 (Coal)

and comparing the results with the certified and published values.

b. Freeze-Drying Studies of Oysters and Salt Water

S. H. Harrison

In conjunction with the National Environmental Specimen Bank

project on evaluating sample storage procedures, a study of freezedrying as a pre-treatment for room temperature storage of oyster and

water samples has begun. For oysters, the concern is whether some trace

elements are volatilized during the freeze-drying process. For salt

water there are several different reasons for investigations. First, is

the possible loss of trace elements from the sample due to actual mass

loss (sputtering during freeze-drying) . The second is the loss of some

trace elements which may exist in volatile chemical forms. CThese first

two factors have been investigated for fresh water by Harrison et al.)

(1). A final reason for studying freeze drying of salt water is an interest in the ability to reconstitute the sample to the original

118
NON-RRD NBS PR0GRAI4S

volume while retaining properties such as salinity.

Fourie and Pusach (2) have evaluated freeze drying and oven drying

oysters using radioactive tracer techniques. In their study, oysters were placed in water containing various radioactive species for 1 month

and then counted before and after preconcentration. It must be pointed

out that one possible difficulty with this method is in shucking the

oyster in such a way that only oyster meat and body fluid are collected

and water (usually greater than 50% of the volume inside the shell

containing the radioactive tracer, is drained off. Fourie and Peisach

find that only for cadmium are significant losses from freeze drying

detected.

It was felt that in this laboratory a similar, but perhaps more

definitive, study could be made without the use of radioactive tracers.

By careful sample packaging techniques, instrumental analysis of wet

tissues could be done with the NBS Reactor. Therefore, in this ex- periment a collection of 40 oysters about the same size and from the same bed would be split into two groups; 20 will be freeze dried and

analyzed and 20 will be analyzed wet. A comparison of elemental con- centration means and standard deviations should definitively determine

if losses from freeze-drying occur for these biologically incorporated

trace elements. Colby et al. (3) have studied the variability of Zn in

oysters for individuals from a single bed and groups from different beds

and conclude that 20 individuals is a valid sampling of oysters.

The salt water study will entail a similar comparison of a set of

freeze-dried samples to liquid samples, all from the same bottle.

1. S. H. Harrison, P. D. LaFleur and W. H. Zoller, knal. Chem. , ^1_,

1685 (1975).

2. H. 0. Fourie and Max Peisach, Analyst^ 102^, 193 (1977).

3. D. R. Colby, F. A. Cross and R. J. Huggett, "Variability of Zinc in

Oysters (Crassostrea viginica) : Implications for Sampling Design,"

(to be published)

.

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THE INTERMEDIATE-ENERGY STANDARD NEUTRON FIELD (ISNF)

D. M. Gilliam,, C. M. Eisenhauer, J. A. Grundl

(Center for Radiation Research)

The Intermediate-Energy Standard Neutron Field (ISNF) Facility

has become operational and initial experimental results have been

1 2

reported, ' The objectives of this measurement program are as follows : to develop an irradiation facility which will produce a well-characterized neutron field with a strong spectrum component in

the energy range 5 keV to 4 MeV relevant for studying fast neutron

reaction rates. Specific applications include:

1. Measurement of basic fission and capture cross sections.

2. Calibration of activation and other passive neutron detectors

employed in reactor fuels testing.

3. Long-term measurement assurance and detector performance

studies for power reactor neutron dosimetry.

A. Validation of neutron spectrometers and related energysensitive neutron detectors.

The ISNF arrangement is fundamentally simple as can be seen in

figure 1: a spherical cavity in the graphite thermal column of the

NBS reactor, a thin shell of boron-10 lightly supported at the cavity

center, and fission source disks of U-235 placed symmetrically around

the periphery of the cavity. Thermal-neutron- induced fission neutrons

in the source disks - both the uncollided and those returning from the

graphite - are transmitted by the boron-10 shell and give rise to the

ISNF field at the center of the cavity. Summary properties of the

ISNF field are as follows:

8 —2 —1

Total neutron flux intensity: '^ 7 x 10 n . cm .s 14 -2

Typical maximum fluence :

'V' . 5 x 10 n . cm Neutron field gradient: < 2% over 4 cm

Spectrum:

average and median neutron energies: 1.0 MeV and 0.56 Mev,

respectively

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NON-RRD NBS PROGRAMS

energy range: 90% of spectrum between 8 keV and 3.5 MeV

Response range of 1/v-detector : 90% between 0.5 keV and

1.5 MeV

Initial measurements of fission cross section ratios for U-235,

U-238, and Pu-239 have been completed. The flux and spectral gradients

along the axis of the system have been checked, and thermal-neutroninduced background and leakage have been measured, also. These

results are presented in tables 1, 2, and 3 below.

Figure 1. A schematic drawing of the ISNF spherical cavity.

121
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Table 1. Measured Fission Cross Section Ratios and Comparisons with

Calculated Values.

x:U-238

x:Pu-239

Measured*

0.0923 + 1.1%

1.155 + 1.8%

a^(x)/a^(U-235)

Calculatedt

0.0843

1.113

(Calc/Meas -1) x 100%

8.7%

3.6%

*The cross section values and error estimates given here were derived

without taking into account possible perturbations due to epithermal

neutron leakage.

tCalculated cross section ratios are derived by folding together the

ENDF/B-IV cross section data and the neutron energy spectra given in

the compendium by Grundl and Elsenhauer (Ref. 2).

Table 2. Measured Residual Thermal-Neutron-Induced Response with Fission

Source Disks Removed.

Fission Rate Fission Rate Background and

in ISNF Due to Thermal Thermal- Induced

Fissionable Spectrum Neutrons plus Fission Rate/

Isotope Background Fast--Induced

(s mg ) (s mg ) Fission Rate

U-235 3170 45 + 11 1.4%

U-238 290 8 + 0.5 2.8%

Pu-239 3660 47 + 10 1.3%

Table 3. Spatial Gradients in the ISNF Central Test Region.

Measured Fission Rate Change

from ISNF center to a point

2.5 cm away from the center

Isotope Observed

U-235 U-238

-(2.3 + 0.5)% -(2.9 + 0.8)%

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NON-RRD NBS PROGRAMS

1. D. M. Gilliam, "Integral Measurement Results in Standard Fields,"

Proceedings of the International Specialists Symposium on Neutron

Standards and Applications, Gaithersburg, MD (1977).

2. J. S. Grundl and C. M. Eisenhauer, "Benchmark Neutron Fields for

Reactor Dosimetry," Proceedings of the IAEA Consultant's Meeting

on Integral Cross Section Measurements in Standard Neutron Fields

for Reactor Neutron Dosimetry, Vienna, (1976).

FISSION RATE I NTERCOMPARISONS WITH THE REACTOR PHYSICS

GROUPS AT ARGONNE NATIONAL LABORATORY

D. M. Gilliam

(Center for Radiation Research)

and

R. J. Armani

(Argonne National Laboratory, Argonne, IL)

A round robin test series was undertaken to intercompare fission

rate measurement capabilities at NBS-Neutron Standards and ANL-Reactor

Physics. The first series of planned intercomparison measurements have

been made, and some results are reported here from NBS and ANL-E

(Argonne National Laboratories; Argonne, IL) . A set of 18 fissionable

deposits was prepared by R. J. Armani of ANL-E including the three

isotopes U-235, U-238, and Pu-239. Six deposits of each isotope were

made with nominal masses ranging from 23 yg to 85 yg. Armani also alpha

counted the entire set. Two deposits of each isotope were compared to

the NBS Reference Deposits by fission counting. For the U-238 deposits,

this comparison was carried out at the NBS Cf-252 facility. For the other

isotopes, the comparison was carried out in a beam from the thermal

column of the NBS Research Reactor. All six of the U-235 and Pu-239

deposits were counted relative to NBS Reference Deposits and alpha

emission standards, but corrections for alpha emissions from minor isotopic

constituents have not been completed as yet so that only relative masses,

normalized to the fission comparison results can be given from the alpha

123
NON-RRD NBS PROGRAMS

Table 1: Comparison of results: NBS vs. ANL-E

Total Elemental Mass*

Inter comparison

Fission Deposit NBS ANL-E Discrepancies

Label Value Value (NBS/ANL-1)

(yg) (yg) (%)

N-U5-1 27.11(38) 26.92(13) 0.7

N-U5-2 28.62(39) 28.51(14) 0.4

N-U5-3 53.1(7) 52.67(25) 0.8

N-U5-4 50.8(7) 50.39(24) 0.8

N-U5-5 75.2(11) 74.51(36) 0.9

N-U5-6 73.7(10) 73.19(36) 0.7

N-P9-1 22.79(30) 22.81(13) -0.1

N-P9-2 24.37(32) 24.52(14) -0.6

N-P9-3 43.0(6) 43.38(24) -0.9

N-P9-4 45.2(6) 45.13(26) 0.2

N-P9-5 69.6(9) 70.17(39) -0.8

N-P9-6 74.5(11) 75.00(42) -0.7

N-U8-5 80.4(13) 80 (Nominal) 0.5

N-U8-6 84.0(14) 85 (Nominal) -1.2

*The number in parentheses is the uncertainty in the least significant

digit.

data at this time.

As may be seen in table 1, the ANL-E and NBS mass comparisons agree

within 1.2%, well within the estimated errors of the comparison.

124
NON-RRD NBS PROGRAMS

U-235 CAVITY FISSION IRRADIATION FACILITY

V. Spiegel, Jr.

(Center for Radiation Research)

The U-235 thermal-neutron-induced fission neutron spectrum is a key standard neutron field for the validation of differential nuclear

data needed for fast reactor physics or for neutron dosimetry. At the

NBS this fission spectrum is produced in a 30 centimeter diameter

spherical cavity in the reactor thermal column. As an example cadmiumcovered nickel-iron detectors of 1/2 inch diameter were sandwiched between two U-235 disc of 5/8 inch diameter, which weighed about 500

milligrams each. For a separation distance between the two U-235 discs

of about 8 millimeters, the average source to detector separation is

about 1 centimeter. Since the average source-to-detector separation is

small relative to the size of the cavity, a negligible fraction of

fission neutrons produced in the uranium discs were returned to the

detectors from the cavity walls compared to the direct flux. The U-235

neutron flux obtainable in this facility was about 100 times more

2 intense than is available from our Cf-252 irradiation facility.

Three discs of SRM-1158 (36% nickel, 63% iron) were irradiated in

the U-235 Cavity Fission Irradiation Facility for approximately 24

hours. The ratio of the nickel to iron cross section in the U-235

fission spectrum is to be determined by three participating laboratories

of the Interlaboratory Reaction Rate (ILRR) program, namely, Argonne

National Laboratory, Idaho National Engineering Laboratory, and Handford

Engineering Development Laboratory.

A. Fabry, J. A. Grundl, and C. Eisenhauer, "Fundamental Integral

Cross Section Measurements in the Thermal-Neutron- Induced

Uranium-235 Fission Neutron Spectrum," Proceedings of the Conference

on Nuclear Cross Sections and Technology, (1975)

.

J. A. Grundl, V. Spiegel, C. M. Eisenhauer, H. T. Heaton II,

D. M. Gilliam, and J. Bigelow, "A Californium-252 Fission Spectrum

Irradiation Facility for Neutron Reaction Rate Measurements,"

I^ucl. Tedh., 32., 315 (1977).

125
N0N-:^JID NBS PROGRAMS

ABSOLUTE MEASUREMENT OF THE DT THICK TARGET YIELD AT

191.3 KeV USING A THERMAL NEUTRON BEAM

R. F. Fleming and R. B. Schwartz

(Center for Radiation Research)

The thick target yield of the reaction D(t,a)n for tritons of

initial energy 191.3 KeV slowing down in deuterium gas has been measured.

This yield is defined as the number of DT reactions occurring per triton

and can be expressed as

Eo

(1)

where a(E) is the reaction cross section and S(E) is the stopping power

for tritions in deuterium. This reaction is important since

deuterium-tritium will be the fuel in any foreseeable first generation

fusion reactor.

10'

^ 10 CO Q

O

oO

10 -

10 -

(1 - ^

He {n,p) T Thick Target Yield

" /

E = 191 keV

"nJ

Pile Up

Backgrou nd

J-

\ 3 Fold Pile Up V/ D (T,a)n ^^

.L .. ^r~^

50 1 00 1 50 Channel Number

200 250

Figure 1. Pulse height spectrum from thermal neutrons on gas proportional

counter filled with 5 atm. of D and 10 torr of He-3.

126
NON-RRD NBS PROGRAMS

The measurement was done by placing a standard end-window, gas proportional detector filled with five atmospheres of D„ and about 10 torr

of He-3 in a Bragg-scattered thermal neutron beam. The tritons are produced by the reaction He-3(n,p)T which gives a count in the 763.8 keV

4

peak for each reaction. About once in every 10 times the triton, in

slowing down, reacts with a deuterium atom to give a D(t,a)n event. The

"14 MeV" neutron escapes the detector without interacting, but the alpha

particle will produce a broad high energy distribution in the pulse

height spectrum. The ratio of the number of alpha counts to the number

of He-3 counts is an absolute measure of the thick target yield. (See

figure 1.) The preliminary result is in reasonable agreement with the

value calculated from equation 1. The final result will be available as soon as we calculate the correction for the counter end effect.

1. Stewart, L. and G. M. Hale, "The T(d,n)He-4 and T(t,an) Cross

Sections at Low Energies," LA-5828-MS (1975).

FILTERED BEAM FACILITY

Robert B. Schwartz

(Center for Radiation Research)

1. Improvements to 25 keV Beam

The 25 keV beam has been rebuilt using larger diameter collimators

and higher purity aluminum. We now have a neutron intensity of 1.0 x 10

neutrons/sec, which represents a factor of 12 improvement over the

previous configuration.

2. Measurement of the B-10 ISNF Shell

The low energy flux distribution of the ISNF (Intermediate-Energy

Standard Neutron Field) is carefully "tailored" by means of the B-10

content of the shell. Knowledge of this flux distribution is essential

for proper interpretation of the results from this facility. The flux

distribution must be calculated, since direct measurement is a formidable

127
NON-KRD NBS PROGRAMS

problem. The calculations in turn, require accurate knowledge of the B10 content of the shells. While this datum was supplied by the shell

fabricators at LASL, it is obviously desirable to check both the B-10

content and its uniformity experimentally. A simple transmission experiment is probably the most reliable method. The B-10 shells are (by

design) black to thermal neutrons; hence a transmission measurement at

thermal won't give any information. The transmission at 2 keV is,

however, almost ideal: 'x^ 30%.

Accordingly, a transmission experiment was done at the 2 keV filtered

beam. The results of the uniformity measurements were most gratifying:

the B-10 content does not vary by more than +0.5% over the shell surface.

Our measured value for the absolute B-10 content differs from that given

by LASL by '^^ 4%. This difference, while small, is significant and will

be remeasured.

3. Use of the Filtered Beams for Dosimeter Calibrations

The filtered beams have been funded by ERDA as a dosimeter calibration facility. Although the facility is not yet quite open for

business, several calibrations have been performed by ERDA contractors.

In general, the facility seems to serve the function for which it was

funded. The 144 keV beam provides an overlap with existing calibration

facilities, the 24 keV beam fixes the low energy end of these facilities,

and the 2 keV beam allows calibrations to be extended a decade lower in

energy than had previously been possible. There is good agreement (where

appropriate) with other calibration facilities and with calculations.

Work is continuing to improve the quality of the beams and our calibration

of them.

R. B. Schwartz, "Calibration and Use of Filtered Beams," Proc. Int,

Specialists Symp. on Neutron Standards and Applications.

Gaithersburg, MD, to be published.

128
NON-RRD NBS PROGRAMS

PRECISION MEASUREMENT OF THE WAVELENGTH OF

NUCLEAR GAMMA LINES AND THE COMPTON

WAVELENGTH OF THE ELECTRON

R. D. Deslattes, E. G. Kessler, W. C. Sauder, and A. Renins

(Optical Physics Division)

A unique facility has been established at NBS which permits precision measurement of wavelengths of spectral lines in the 50 keV to 1 MeV

range in terms of the wavelength of a visible molecularly stabilized

laser. The radiation is diffracted by nearly perfect Ge and Si crystals

in a two crystal transmission spectrometer. The lattice spacings of the

crystals have been accurately determined in terms of the stabilized

laser in a separate experiment, while the diffraction angles are measured with angle interferometers. Experimental arrangements have been

12 3 documented in more detail elsewhere. '

'

Most precision measurements require detailed investigation of

systematic errors, and this experiment is no exception. During the past

year we have made significant progress in understanding the vertical

divergence correction, the shape of recorded line profiles, and the

dependence of the angle interferometer calibration on temperature and

the aging of the invar interferometer structure.

Because the radiation cannot be sufficiently confined parallel to

the plane of dispersion without unacceptale loss of intensity, we must

work with an appreciable vertical divergence. The effect of vertical

divergence on the line profile is to introduce a slight asymmetry in the

dispersive position which has now been modeled in an analytical form.

We have used a convolution of this vertical divergence smearing function, the crystal diffraction patterns and an empirically determined

Gaussian component to fit the observed data and thereby extract directly

the Bragg-Laue angles. In early trials, the fit for data recorded with

Si crystals was satisfactory, while data recorded with Ge crystals

showed an asymmetry which could not be explained by other than imperfection in at least one of the Ge crystals which was subsequently

129
NON-RRD NBS PROGRAMS

replaced with good effect.

The angle Interferometers were calibrated at different temperatures

and at different times of the year in order to determine the temperature

coefficient of the calibration and the growth of the invar corner cube arm with time. Improvements of the analysis of the calibration data to

compensate for second order errors resulting from the tip of the optical

polygon and the autocollimator slit have provided a calibration constant

accurate to 0.1 ppm.

Understanding of the above mentioned systematics brought to light a significant discrepancy between wavelengths measured with Ge and Si

crystals. The Ge lattice spacing was then remeasured in a more care- fully controlled experiment with the result that the discrepancy has

been eliminated.

During the past year we irradiated three Au samples for additional

measurements on the 412 keV line and new measurements on the 675 keV

line. By employing the combination principle, a precise standard at 1.09

MeV is thereby available. Final wavelengths for the Au lines along with

9 lines from Ir-192 (205, 295, 308, 316, 468, 484, 588, 604, 612 keV)

will soon be available and will provide accurate standards in the 100

keV to 1 MeV range.

Our measurement of the Au 411 keV y-ray line brought to light a difficulty involving the WKa line. Another route to the 411 keV line

is as follows: A previous (1 ppm) measurement of A(MoKa-) in terms of a visible standard is combined with the (2 ppm) ratio X(WKa^)/ X (MoKa,

)

5 from Bearden et at. to obtain a value for A(WKa^). When this is com- bined with the ratio A( Au 411)/ A(WKa^) from Borchert et at. a 198 value for X( Au 411) results which differs by more than 100 ppm from

our measurement.

In order to resolve this difficulty we directly measured the wavelength of the WKa.. line first with Ta-182 radioactive source and later

and more successfully with a W x-ray tube. Our measurements suggests

that the ratio A(WKa^)/ A(MoKa^) is in error in that combining the new measurement of WKa^ with Au/W ratio of reference 6 gives quite satis130
NON-RRD NBS PROGRAMS

factory agreement with the direct route.

Very recently a Tm foil was activated and profiles of the 84 keV

line from the decay of Tm-170 were recorded. Measurements of this line

were undertaken because it has been used as a secondary energy

[le9

7 8

standard ' particularly in measurements of pionic x-rays from which

pion mass values are deduced.

1. R. D. Deslattes, E. G. Kessler, W. C. Sauder, and A. Renins, Atomic

Masses and Fundamental Constants 5, J. H. Sanders, A, H. Wapstra,

eds.. Plenum Press, New York, p. 48 (1976).

2. R. D. Deslattes, E. G. Kessler, W. C. Sauder, and A. Renins, Nat.

Bur. Stand. (U.S.), Teoh Bote 896, 114 (Jan. 1976).

3. R. D. Deslattes, Course //LXVIII, "Metrology and Fundamental Con

stants", Enrico Fermi School of Physics, July 12-24, 1976.

4. R. D. Deslattes and A. Renins, Phys. Rev. Lett. 31, 972 (1973).

5. J. A. Bearden, A. Renins, J. G. Marzolf, W. C. Sauder and

J. S. Thomsen, Phys. Rev. 135 , A899 (1964).

6. G. L. Brochert, W. Scheck, and 0. W. B. Schult, Nual. Instr. and

Meth. 124, 107 (1975).

7. W. Beer and J. Kern, /VweZ. Instr. and Meth. 116 , 183 (1974).

8. G. L. Borchert, W. Scheck, and K. P. Wieder, Z. Naturforsoh 30a,

274 (1975).

9. R." E. Shafer, Phys. Rev. D 8, 2313 (1973).

131
D. Summary of Reactor Operations

All aspects of reactor operations continued to be excellent.

Once again, outstanding on-line performance and full utilization

efficiency were achieved. A new major in-core facility located in the

center of the reactor was installed and is already being utilized. A

summary of the overall operating statistics for this and previous

years is presented in the following table.

NBSR Operating Summary

Reactor Operations to date, MWh

Reactor Operations for year, MWh

Hours Reactor Critical

Number of Days at 10 MW

On-line Time at 10 MW

Number of fuel elements used

Average U-235 Burnup

Number of Refueling Operations

Number of Unscheduled Shutdowns

Number of Irradiations

Irradiations, Total Hours

Hours per irradiation

Number of Visitors

1974 1975 1976 1977

290,000 328,000 396,000 459,000

61,000 38,000 68,000 63,000

6,000 3,900 6,900 6,400

254 157 283 262

70% 43% 78% 72%

24 16 24 24

54% 53% 55% 56%

6 4 6 6

6 2 3

3,000 1,550 2,360 2,255

4,300 1,800 7,250 7,400

1.4 1.2 3 3.3

5,000 3,000 7,000 3,000

SUMMARY OF NBS REACTOR HEALTH

PHYSICS ACTIVITIES AND SERVICES

T. Hobbs

(Health Physics)

During the past year, the NBS Reactor Health Physics group provided

radiation safety surveillance and support services for all radiological

activities which occurred at the reactor facility. Among the activities

and services performed on a continuing basis by NBSR Health Physics were

the following:

132
SWWARV OF RFACTOR OPERATinNS

(1) Film badge monitoring of all personnel at the NBSR for radiation

exposure control;

(2) Routine bioassay sampling of all Reactor Operations personnel

and, as necessary, other individuals for internal nuclide monitoring and

exposure control;

(3) Radiation surveys of areas and equipment and monitoring of

irradiated samples;

(4) Contamination control at the facility by regular swipe surveys

of the radiological laboratories, experimental and maintenance equipment,

and other areas of the reactor;

(5) General sampling and surveillance activities required for NBSR

effluent monitoring; personnel exposure control, and environmental monitoring;

(6) Consultation on all matters involving radiation safety at the

NBSR;

(7) Indoctrination of all new employees in the radiological safety

practices and emergency procedures to be followed at the facility; and

(8) Health physics activities and services of a general nature,

such as radioactive waste collection and disposal, laundering and decontamination of anti-contamination clothing, and calibrating radiation

survey instruments.

Table 1 presents a summary of NBSR Health Physics surveillance and

sampling activities for the five-year period, 1972-1976.

133
SmiMARY OF REACTOR OPEPATIONS '

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134
E. Service Programs

THE NEUTRON ACTIVATION ANALYSIS PROGRAM OF THE

FOOD AND DRUG ADMINISTRATION AT THE NBSR

J. T. Tanner and M. H. Friedman

(Food and Drug Administration, Washington, DC)

The activation analysis unit of the Food and Drug Administration

(FDA) is located at the National Bureau of Standards in the Reactor

Building. Neutron activation analysis (NAA) has been used by the FDA

for trace metal analysis of foods, drugs, hair, laundry aids, and cosmetics. The service of this group is available to anyone within the

FDA both in the headquarters laboratory and in the field. The program

described below accounts for the main effort of NAA at the FDA during

the past year.

Solid waste from farm animals has traditionally been used as cropland fertilizer. In recent years municipal sewage sludge is also

being increasingly used as crop fertilizer. The safety with respect

to animal and human health of cropland application of sewage sludge is

currently the subject of considerable research activity. The

broader aspects concerning management of sludge use on land to assure

safety and wholesomeness of the food supply have also been discussed.

While an environmentally and energy conscious public seeks to

maximize waste production utilization, the volume of solid waste from

animal feedlot operations and municipal waste treatment plants is

growing steadily. Because of the large amount of undigested protein

and high levels of several nutrient elements in these wastes, they are currently being considered as animal feed ingredients to be mixed with

the more traditional grain and forage animal feeds.

The practices of feeding "wastelage" (derived from ensiling

ground grass hay and manure) , or mixtures of dried animal waste and

7-9

feeder lot rations appears to be commonplace. Although several

states have approved use of animal waste as a feed ingredient for meat

producing animals sold in intrastate commerce, the U. S. Food and Drug

135
SERVICE PROGRAMS

Administration has recently decided to delay issuing proposed guidelines

for the safe use of animal waste in feed, because legitimate questions

about safety remain unanswered. While sewage sludge has not been

formally approved for use in feed by any governmental agency, several

federal and state supported projects are studying the effects of

feeding sewage sludge to animals on an experimental basis.

Most feeding studies with animal wastes or sewage sludge being

fed to animals have been conducted with the objective of showing the

nutritive value of the material being fed, and not for the purpose of

12

determining possible effects on human health. Blattacharga and

12

Taylor have recently reviewed the use of recycled animal waste as a feed ingredient. Their review summarizes available information on:

(i) the nutritional value of different kinds of animal waste; (ii) the

possible human and animal health hazards from pathogens, drug and

nutritional supplement residues, pesticides, and contaminant industrial

chemicals, and (iii) the effects of processing methods on the safety

of animal waste feed. They also give literature referenced levels of

Al, As, B, Ca, CI, Co, Cu, Fe, K, Mg, Mn, Na, P and Zn in poultry,

swine, and cattle manure with respect to the nutrient composition of

these wastes. Their review indicates that little work has been done

to determine typical trace element content of animal wastes for other

elements. Nor has much work been done to determine whether trace

elements accumulate in edible tissue, or edible products, from animals

fed diets containing animal wastes. Studies of the potential for

tissue accumulation in steers of As, have been done in which feeding

of broiler litter containing As as a feed additive residue resulted in

13 tissue levels proportional to the amount of As ingested. Smith and

14 Calvert have recently reported on the levels of Cu, Zn, Fe, Cd, and

Pb in diets containing 88% com meal supplemented with either cottonseed

meal (control diet) or dried poultry excreta (DPE) , and on the effects

of accumulation of these metals in liver, kidney, muscle, and blood

from steers fed the two diets. Reported levels of Zn, Cu, and Fe were

136
SERVICE PROGRAMS

2-4 higher in the DPE diet than in the control diet, but were essentially the same for Cd and Pb. The levels of Cu in liver and Fe in kidney

were significantly higher for steers on the DPE diet. Otherwise no other significant differences in tissue levels were seen. The levels

of elements in the bones of the animals on the two diets were not

reported.

In another recent study Furr, et at. fed Swiss chard grown on soil treated with municipal sewage sludge to guinea pigs for 28 days.

The Swiss chard had elevated levels of many trace metals compared to

Swiss chard grown on a control soil containing no sludge. Analyses of

liver, kidney, muscle, adrenal and spleen from the guinea pigs showed

increased deposition of specific elements (including As, Cd, Ce, Co,

Cr, Cs, Cu, Hg, K, La, Mg, Mn, Na, Pb, Sb, Sn, Ti, V, and W) in tissues

from animals fed the sewage sludge amended Swiss chard compared to

those fed the control Swiss chard. Depending on the element and the

tissue, increased deposition ranged up to the high of a 10.8 fold

Increase for Sn in the kidney. The authors concluded that similar

feeding studies over longer time periods for a greater number of

animals are needed.

Numerous papers have appeared in the literature reporting the

elemental content of sewage sludges for various numbers of

elements. ' However, the most comprehensive report is that of

Furr, et al. , who reported the levels of 68 elements in sewage

sludges from 16 American cities and in a dehydrated bagged commercial cow manure product. The mean value for the 16 cities for each element

determined by Furr, et al. is shown in table 1. The analytical techniques for the 68 elements included spectrophotometry, neutron activation, emission spectroscopy, spark source mass spectrometry, anode

stripping voltammetry, furnace atomic absorption, flameless atomic

absorption and flourescence. In that study each element was determined

by the alternate analytical technique. The authors state that the

samples were air-dried, mixed in a Lucite twin shell blender, and

137
SERVICE PROGRAMS

subsampled for analysis. However, no precision data is reported to

indicate the homogeneity of the samples analyzed.

The macroelement (Ca, P, Mg, S, K, Na, and CI) and the microelement (Co, Cu, I, Fe, Mn, Se and Zn) contents of traditional animal

feeds and mineral supplements are available in the literature along

with the dietary levels of most of these elements required for normal

18 19

growth in cattle, horses, sheep, swine, rats and dogs. ' However,

little information is available on typical levels of many other elements

in traditional animal feeds.

The purpose of our study was to determine the levels of as many

elements as possible in typical dried animal wastes having a documented

history and to compare these levels with those of the same elements in

animal feeds and sewage sludges . From this comparison we hoped to

develop the data necessary to support conclusions about the desirability

or relative safety of using animal wastes and sewage sludges and

animal feed ingredients. Such data should assist in choosing among

the various possible alternatives for beneficial use of animal wastes

and sewage sludge, including cropland application, conversion to

methane, and animal feed ingredients.

1. Samples

The samples analyzed were all received from the same source

(Colorado State University) and included: (I) A typical feedlot

ration without animal waste products added. The dry weight composition

of this ration was 70% corn, 3% hay, 5% beet pulp, 20% com silage and

2% mineral supplement; (II) oven dried cattle manure from feeder lot

heifers fed a low fiber diet containing 59% com, 2% alfalfa hay, 3%

molasses, 33% com silage and 3% mineral supplement; (III) oven dried

cattle manure from feeder lot heifers fed a high fiber diet containing

24% com, 29% alfalfa hay, 3% molasses, 41% com silage and 3% mineral

supplement; (IV) a commercial high-protein feeder lot animal waste

product similar to (III) in which a portion of the fiber and ash was

138
SERVICE PROGRAMS

removed and the product was pelletized; (V) dried poultry waste with

litter consisting of wood shavings mixed with excreta from hens fed a layer ration; (VI) dried poultry waste from caged laying hens without

any litter; (VII) dried sewage sludge from Denver Metro District.

These samples correspond to columns I through VII respectively in

table 1.

2. Sample Preparation

The feedlot ration was analyzed without further homogenization.

Portions of the animal wastes and sludge samples (100 g) were initially

blended with a blender and subsamples were analyzed by neutron activation analysis (NAA) , flame atomic absorption spectrometry (AAS) , and

andoic stripping voltammetry (ASV) as described below. However,

because most of the waste samples were still visibly inhomogeneous

,

additional portions of the as received unhomogenized waste and sludge

samples (70 to 105 g each) were mixed in the ratio of 4 parts distilled

deionized water to 1 part dry material and homogenized at high speed

with a homogenizer equipped with sonic probe type generator until a homogeneous slurry was obtained (usually about 5 minutes) . The slurries

were then freeze dried. The resulting dry samples were analyzed using

I AAS, ASV, NAA, and induction coupled plasma optical emission

spectroscopy (ICP). Details of the NAA analyses were reported in last

|i years NBSR report and will not be repeated here. Information about

20-23

the other analytical methods may be found elsewhere.

3. Results

The analytical results from determination of 30 elements in the

animal feeder lot ration, animal wastes, sewage sludge, and the NBS

Reference Materials Orchard Leaves, Bovine Liver, and Spinach are re- ported in table 1. Values are reported only for those elements whose

concentrations fell in the reliable quantitation range for the method

indicated. In the case of the highly toxic elements Be and Hg less139
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than values are reported when quantitation was not possible.

The mean levels of the same elements in sewage sludges from the

16 city study reported by Furr, et al. are also tabulated in table 1

for comparison with the data obtained in this study.

Among the animal wastes, the low fiber diet manure has a slightly

lower content of most metals than the high fiber diet manure. The

processed waste pellets, which were derived from a high fiber diet

manure, also contained a lower content of most metals than did the

high fiber diet manure. During processing of the pellets, some of the

fiber and ash was removed from the manure, which probably accounts for

24

the lower metals content. In general the poultry waste without

litter contains higher levels of most elements than the poultry waste

with litter. The lower levels in waste with litter probably are due

to dilution by the litter (mostly wood chips)

.

The order of magnitude of the levels of elements found in the

Metro Denver sewage sludge compares well with the average level calculated from the 16 city study by Furr, et al . With a few exceptions

the levels of elements found in the NBS Reference Materials agree well

with the certified or uncertified NBS values.

Whenever comparisons of the levels found in the same sample by

different determinative step techniques are possible the results are generally in good agreement. Two exceptions are the lower Se and Sb

values obtained by AAS compared to NAA. Because AAS analyzes only the

acid soluble portion of the sample while NAA analyzes the whole sample,

these analyzes indicate that part of the Se and Bb is associated with

the acid-insoluble portion of the samples.

Considering the gross inhomogeneity of the samples as received by

the laboratory, including the wood chips, feathers, undigested grain,

small rocks, and other identifiable particles normally present in

animal waste and sewage sludge, the precision of the analytical results

and the agreement of analyses of a given sample by several techniques

are quite good. The extensive amount of data does not permit re140
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porting precision data for individual elements by all techniques.

One problem with trying to achieve homogeniety with the waste and

sludge samples is that abrasion of the homogenizer blade metal by

small rocks or other solid material can contaminate the sample.

Homogenization of the waste and sewage sludge samples with the homogenizer resulted in measurably higher levels of Co, Cr, and Ni compared

to the unhomogenized samples. Thus the values reported for Co and Cr

in table 1 are for blended samples. The blender does not produce the

shear action of the homogenizer and thus does not produce measurable

comtamination due to abrasion.

4. Discussion

The levels of the macroelements Ca, CI, Mg, P, K, and Na, and of

the microelements Co, Cu, Fe, Mn, Se, and Zn found in the animal

wastes and sewage sludge are considerably above the levels of these

1

8

elements reported in the literature as being necessary for normal

growth in cattle, horses, sheep, swine, rats and dogs. The levels of

As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Sn, Ti, V, and Zn are all at least

a factor of 5 higher in animal wastes than in the feeder lot ration.

The levels of some of these may be high enough to raise concern about

continuous use of animal wastes as a animal feed ingredient. The

j levels of Al, As, Cd, Co, Cr, Cu, Eu, Fe, Hg, Pb, Sb, Sn, Ti, and Zn are all at least a factor of 100 higher in sewage sludge than in the

feeder lot ration. Toxicity could be expected to occur in some animals

if feeds were fed having the levels of Cd, Cr, Cu, Fe, Mn, Pb, Se and

1 Q ^ A Zn shown in table 1 for sewage sludge. ' ' Whether any of the

above elements would concentrate in animal tissues, similar to that

demonstrated in previous studies ' ' ' sufficiently to present a human health hazard can only be determined by appropriate feeding

studies with animal wastes or sewage sludge as feed ingredients. It

27 xs known that Cd accumulates in beef liver and kidney and that the

current level of Cd in the American food supply already approximates

141
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the World Health Organization maximum tolerable intake. Multiple

recycling of animal wastes should also be studied for the effects on animal health and tissue elemental levels. Assuming a more or less

constant concentration factor for each element with each pass through

the animal and a more or less constant fractional absorption of each

element during each pass, the potential exists for significantly

elevated absorption for most elements after only a few passes. Whether

multiple recycling of animal wastes actually results in elevated

tissue elemental levels can only be determined by appropriate feeding

studies.

Any widespread use of animal wastes or sewage sludge as animal

feed ingredients could be expected to be accompanied by a need for

periodic multielement and multiresidue organic analysis of the mixture

being fed. Because of the gross variability, both with time and

location, of animal wastes and especially sewage sludge, obtaining

representative samples for analysis, which accurately reflect the

average level of each element or residue being fed, would be a difficult

problem. The cost of such representative analyses would detract from

the economic gain of using these waste products as animal feed ingredients.

The results of this work indicate that the levels of most inorganic

elements are considerably higher in animal wastes and sewage sludge

than in traditional animal feeds. These findings suggest that the

safety of using animal wastes, sewage sludge, and multiple recycled

animal wastes, both with respect to animal and human health, should be

thoroughly investigated by animal feeding studies.

Acknowledgement

This report is a condensed version of paper submitted to Environmental Science and Technology entitled, "Multielement Analysis of Animal

Feed, Animal Wastes, and Sewage Sludge," by S. G. Capar, J. T. Tanner,

M. H. Friedman, and K. W. Boyer from the Division of Chemistry and

Physics, U. S. Food and Drug Administration, Washington, DC, 20204.

146
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1. A. F. Furr, C. S. Sloewsand, C. A. Bache, and D. J. Lisk, "Study

of Guinea Pigs fed Swiss Chard Grown on Municipal Sludge-Amended

Soil," Archives of Environmental Eealth, ^, 87 (1976).

2. M. B. Kirkham, "Trace Elements in Corn Grown on Long-Term Sludge

Disposal Site," Environ. Soi. Teahnol. , 9^, 765 (1975).

3. W. J. Garcia, C. W. Blessin, G. E. Inglett, and R. 0. Carlson,

"Physical-Chemical Characteristics and Heavy Metal Content of Corn

Grown on Sludge-Treated Strip-Mine Soil," J. Agr. Food Chem. , 22^,

810 (1974).

4. T. D. Hinesly, R. L. Jones, E. L. Ziegler, and J. J. Tyler, "Effects

of Annual and Accumulative Applications of Sewage Sludge on Assimilation of Zinc and Cadmium by Corn (Zea mays L.),"

Environ. Sci. Teahnol. , n, 182 (1977).

5. A. K. Furr, W. C. Kelly, C. A. Bache, W. H. Gutenmann, and D. J.

Lisk, "Miltielement Absorption by Crops in Pots on Municipal

Sludge-Amended Soil," J. Agric. Food Chem. , 24, 889 (1976).

6. C. F. Jelinek and G. L. Braude, "Management of Sludge Use on Land,

FDA Considerations," Presented at Third National Conference on Sludge Management, Disposal and Utilization, Miami, Florida,

December 14-16, 1976.

7. E. F. Knight, T. A. McCaskey, W. B. Anthony and J. L. Walters,

"Mocrobial Safety of Fermented Manure-Blended Feed," Presented at

71st Annual Meeting American Dairy Science Association, North

Carolina State University, Raleigh, N. C, June 20-23, 1976.

8. L. W. Smith, "Waste Utilization as Animal Feed in the U. S.,"

Conference Proceedings: Commercial Uses of Wastes as Animal Feed^

p. 185, Toronto, April 24-25, 1975.

9. L. W. Smith, "Animal Waste Reuse-Nutritive Value and Potential

Problems from Feed Additives - A Review," Agricultrual Research

Service, USDA, Publication APS 44-224, February 1971.

10. J. C. Taylor, "Provisions of State and Federal Regulations on Refeeding," presented at the Seminar on Feedlot Manure Recycling

for Nutrient Recovery, East Central University, Ada, Oklahoma,

April 7, 1977.

11. G. S. Smith and H. D. Sivinski, "Recycling Sewage Solids as Feedstuff s for Livestock," presented at the Third National

Conference on Sludge Management, disposal and Utilization, Miami,

Florida, December 14-16, 1976.

147
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12. A. N. Bhattacharya and J. C. Taylor, "Recycling Animal Waste as a Feedstuff: A Review," J. Animal Soienae ^ hl^ 1438 (1975).

13. C. C. Calvert, "Feed Additive Residues in Animal Manure Processed

for Feed," Feeds tuffs , 45, 32 (1973).

14. C. C. Calvert and L. W. Smith, "Heavy Metal Differences in Tissues

of Dairy Steers Fed Either Cottenseed Meal or Dehydrated Poultry

Excreta Supplements," Presented at American Dairy Science Associa

tion 71st Annual Meeting, Raleigh, N. C, June 1976.

15. A. K. Furr, A. W. Lawrence, S. S. C. Tong, M. C. Grandolfo,

R. A. Hofstader, C. A. Bache, W. H. Gutenmann and D. J. Lisk,

"Multielement and Cholorinated Hydrocarbon Analysis of Muncipal

Sewage Sludges of American Cities," Environ. Soi. Teohnol. ^ 10 , 683 (1976).

16. A. Chattopadhyay, "Optimal Use of Instrumental Neutron and Photon

Activation Analyses for Multielement Determinations in Sewage

Sludges," Fvooeedings of 1976 International Conference on Modem

Trends in Activation Analyses , p. 493, Munich, Germany, 13-17 Sept.,

1976.

17. D. S. Scott and Harry Horlings, "Removal of Phosphates and Metals

from Sewage Sludge," Environ. Sci. Technol. , 9_, 849 (1975).

18. E. S. E. Hafez and I. A. Dyer, Editors, Animal Growth and Nutrition,

p. 385 Lea and Febiger, Philadelphia, (1969).

19. Nutrient Requirements of Domestic Animals, 5th Rev. Ed. National

Academy of Sciences, Washington, D. C. , (1976).

20. J. W. Jones, Gajan, K. W. Boyer and J. A. Fiorino, J.A.O.A.C. , 60,

in press (1977) .

21. J. A. Fiorino, J. W. Jones and S. G. Capar, "Sequential Determination of Arsenic, Selenium, Antimony, and Tellurium in Foods via

Rapid Hydride Evolution and Atomic Absorption Spectrometry,"

Anal. Chem.,U8, 120 (1976).

22. M. H. Friedmann and J. T. Tanner, "An Automated Activation Analysis

Data Aquisition System," J. Radioanal. Chem. , Z5, 269 (1975).

23. M. H. Friedmann, E. Miller and J. T. Tanner, "Instrumental Neutron

Activation Analysis for Mercury in Dogs Administered Methylmercuric

Chloride: Use of a Low Energy Photon Detector," Anal. Chem. , 46 , 236 (1974).

24. G. M. Ward, personal communication, March 1976.

25. L. A. Maynard, and J. K. Loosli, Animal Nutruition^ 6th Ed., p. 193,

McGraw-Hill, N. Y., (1969).

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26. J. J. Dulka and T. H. Risby, "Ultratrace Metals in Some Environ

mental and Biological Systems," Anal, Chem. ^ hO_, No. 8., 640A

(1967).

27. M. R. S. Fox, "Cadmium Metrabollsm - A review of Aspects Pertinent

to Evaluating Dietary Cadmium Intake by Man," in Tvaae Elements in

Human Healthy A. A. Prasad, Ed., p 26, Academic Press, N.Y. , (1976)

ACTIVATION ANALYSIS PROGRAM OF THE U. S. GEOLOGICAL SURVEY

J. J. Rowe, P. A. Baedecker and J. W. Morgan

(U. S. Geological Survey, Res ton, VA)

The Geological Survey is actively involved in a large scale program

providing analytical data for coals from various parts of the U. S. Coals

are being analyzed for Na, Fe, As, Ba, Br, Co, Cr, Cs, Hf, Rb, Sb, Se,

Ta, Th, Zn, W, Sc, La, Ce, Nd, Sm, Eu, Tb , Yb and Lu at the rate of more

than 1,000 samples per year. Other geochemical studies involve neutron

activation analysis of about 1,000 samples of rocks and minerals per

year.

The rare-earth elements have been useful in characterizing the

magmatic history and crystallization-differentiation for use in wide

variety of studies of ore deposition, alteration and trace element distribution in coexisting minerals. The computer generated reports of

analysis now include a plot of chondrite: sample rare earth ratios as shown in figures 1 and 2,

The analytical procedure routinely determines uranium, via Np-239

to apply corrections for fission product interference. These corrections

are processed via a modification of the computer data reduction procedure of Baedecker. If the uranium content is low or near detection

limits, the correction is negligible. For higher uranium contents an asterisk indicates those results which have a fission product correction

of 20% or more of the concentration of that element.

A study was made of the effects of thermal and epithermal neutron

irradiation of rocks using both Ge(Li) and LEPD detector systems. The use of epithermal irradiation improved the determination of tungsten,

cesium, rubidium, barium, uranium and thorium in rocks, minerals and

coals

149
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The analytical facilities of the U.S.G.S. in Reston, Va. consists

of 5 Ge(Li) detectors (18%-2.0 keV; 12%-2.3 keV; 11%-1.9 keV; 11%-1.7 keV;

12%-1.7 keV) and 3 planar intrinsic germanium detectors. All detectors

are equipped with sample changers. Samples are counted twice on planar

and Ge(Li) detectors to utilize the maximum gamma and x-ray spectra.

Instruments operate 24 hours/day, seven days/week.

Method developments in process include group separations of rare earths to permit the analysis of ultramafics: separations of Cs, Rb, Ta,

As and Sb for application to studies of submarine basalts and methods

for the analysis of fluid inclusions.

THE USE OF ACTIVATION ANALYSIS IN SCIENTIFIC CRIME

DETECTION BY THE FEDERAL BUREAU OF INVESTIGATION

J. W. Kilty

(Federal Bureau of Investigation, Washington, D. C.)

The FBI Laboratory continues to use neutron activation analysis

(NAA) to analyze for antimony and barium in cotton swabs which have been

applied to the hands of suspected shooters. The reliability of NAA for

these measurements in materials which are often heavily contaminated

with soil, blood, grease, etc., makes it our method of choice. From

July 1976, to June 1977, the FBI Laboratory has conducted these examinations on over 1,000 persons.

NAA is used extensively in doing compositional analyses of lead,

copper, steel and aluminum. A recent application of the technique has

been to analyze small ore samples for gold, silver and platinum. The

concentrations of these metals in these ores is so low and the amount

of sample so limited that the conventional assay methods are inadequate.

The value of NAA in conducting trace element analysis in materials

such as synthetic fibers and biologicals is well known.

The FBI Laboratory considers NAA to be a valuable tool in determining elemental composition of evidentiary materials.

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atf's activation analysis program

J. M. Hoffman, W. Kinard and L. Reid

(U. S. Treasury Department, Washington, DC)

Neutron Activation Analysis (NAA) continues to be a valuable tool In

the crime laboratory. The ability to analyze microscopic amounts of

evidentiary material non-destructlvely is a distinct asset in those cases where evidentiary materials must be preserved for courtroom presentation.

During the fiscal year 1977, the following types of evidentiary

materials were examined by NAA. The Irradiation time shown represents

the total reactor utilization for samples of each type.

Total Irradiation

Sample/Type Number of Samples Time (Hours)

Hair 40 136

Paint 17 42

Gunshot Residue 96 2

Explosives 8 4

Glass 6 1

In addition to our use of NAA for forensic purposes, wines and distilled spirits were examined for their trace elemental content using the

NAA technique. This work was done in connection with our regulatory

enforcement program of monitoring the composition of alcohol containing

products.

On-going research using NAA includes the examination of writing inks

for the purpose of identifying the product, its manufacturer, and the

date of the ink's production. This is accomplished by tagging the inks

during the production process with selected elements amenable to detection by NAA and other techniques.

The value of NAA in examining paints and human hair is being critically assessed. Additional analytical data will be accumulated during

FY78 for this purpose and it is intenced that this work will be reported

in mid-1978.

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TRACE ELEMENTS IN THE ENVIRONMENT

AND RADIOACTIVE DECAY STUDIES

W. H. Zoller, G. E. Gordon and W. B. Walters

(Department of Chemistry, University of Maryland,

College Park, MD)

Our group has made extensive use of the NBSR for the irradiation

of numerous samples for trace-element analysis using instumental

neutron activation analysis (INAA) . We have had our computer-based

analyzer system and two Ge(LI) y-ray detectors at the Reactor for

periods of several weeks during the last year to count short-lived

radioactive products. Most of the other samples are returned to the

university for counting long-lived activities.

1. Urban Air Pollution Studies

For several years we have been using instrumental neutron activation analysis (INAA) at the NBS reactor, augmented with other analytical methods, to measure concentrations of 30 to 40 elements in atmospheric particulate material and in suspended particles released from

several classes of major air pollution sources. In past years we have

measured size distributions and compositions of particles released by

two coal-fired power plants, an oil-fired power plant, three municipal

incinerators, two sewage-sludge incinerators, and by vehicles passing

through the Baltimore Harbor Tunnel.

In order to determine if the particles from these sources can account for the composition of material present in urban atmospheres,

we analyzed samples collected from ambient air in Washington, D. C.

during the Summer of 1974. We then "resolved" the average elemental

concentration pattern of Washington aerosols into six components:

soil, marine aerosols (sea salt), and particles released by coal and

oil-fired plants, refuse incineration and motor vehicles. Except for

marine aerosols, the elemental compositions of particles form these

sources, were obtained mainly from our own studies that made use of

the NBS reactor, including the soil component, which was an average of

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28 soil samples from around the Washington area. The strengths of the

six sources were determined by a weighted least-squares fit to the

observed concentrations of eight elements listed at the top of table 1.

Columns 2-7 show the predicted contributions of each source to the

atomospheric concentration of each element. Columns 8 and 9 list the

total predicted concentrations and the observed concentrations and the

final column gives the observed/ predicted ratio. The first eight

elements are forced to fit rather well by the least-squares procedure.

Most of the 15 non-volatile elements among the remaining 19 are fitted

to within a factor of two - a considerable improvement over previous

attempts to account for these very minor, but important elements in

the atmosphere.

Despite the generally good fits obtained by the resolution, there

are some outstanding problems that must be investigated more carefully

and much of our current work at NBS is directed towards that end.

First, we are obtaining much more detailed information on the Washington

atmosphere. An extensive set of samples was taken at several sites

during the Summer of 1976, including both whole-filter and cascadeimpactor samples, the latter to give us more information about the

size distributions of particles bearing the elements. Most of these

samples were analyzed at the reactor during the present year. We're

soon going to collect more samples from the Baltimore Harbor Tunnel to

look for recent changes in emissions. W. R. Pierson of Ford Motor

Company has found increases in emissions of Mg and Ca from trucks that

may account for some of the unexplained amounts of these elements in

Washington. Also, a manganese additive, MMT, is being phased into some gasolines as a replacement for tetratethyl lead and we need to

monitor that change. Furthermore, the group of sources included in

the resolution is incomplete. We know that some air-filter samples

taken in Frederick Coimty, Maryland, contain contributions from a cement plant. Samples in Washington may have contributions from a large steel mill in Baltimore when the wind is from the Northeast.

For these reasons, we have collected filter samples with an airplane

from the plumes of a cement plant and a steel mill and analyzed them

with use of the reactor and will be collecting and analyzing more

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samples soon. One of the problems implicit in our analysis is the assumption

that, once particles leave a plant, they are not modified. But we

know, for example, that some elements from coal combustion are on large particles and other, preferentially on small particles. The

former would be expected to settle out of the atmosphere more rapidly

than the latter after release, thus altering the composition of particles from that source. To investigate those and related questions we have collaborated with Dr. John Ondov et at. of Lawrence Livermore

Laboratory (LLL) on a study of emissions from a large, isolated power

plant in New Mexico. The LLL Group did collections in the stack and

our group collected particles at various distances in the plume. One

set of experiments was done in February 1976 and a second in August

1975. Most samples from the first set were analyzed at LLL, as well

as the in-plant samples from the second set. The pliime samples from

the second set are now being analyzed at the NBS reactor. A preliminary report on the February 1976 experiment was presented at the

Spring Meeting of the American Chemical Society in New Orleans, March

1977 and a final report on both sets of studies will be written when

sample analysis is complete.

T\'7o other small projects are now in progress. For some years it

has been known that lichens (fungi that are attached to trees and

other objects) are sensitive indicators of air pollution such as S0„

.

A group at University of Maryland-Baltimore County is studying damage

to lichens in the vicinity of the Dickerson Generating Station. We

have obtained samples of healthy and damaged lichens from the UMBC

group and are irradiating them for INAA. We want to see if the diseased

lichens show evidence for collection of trace elements that we know

are associated with coal-fired power plants (e.g.. As, Se, Hg) . Also, our entire group is participating in the analysis of the new NBS coal

Standard Reference Materials.

2. Global Air Pollution Studies

For the past several years we have been collecting particles from

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very remote areas of the Earth, especially the South Pole, and analyzing

them, primarily by INAA. at the NBS reactor, in order to determine the

composition of particles that are in global circulation. During the

past year, we analyzed a number of samples collected at the South Pole

during the period October 1975 to February 1976.

Recently we have begun studies of possible major sources of

globally circulating particles, starting with volcanoes. During the

past year we performed INAA of samples collected during the eruption

of the Mt. Augustine volcano in Alaska in January /February, 1976.

Samples were collected using the National Center for Atmospheric

Research's Lockheed Electra during periods of different types of

volcanic activity. In table 2, concentrations of seven common crustal

elements and six volatile elements are listed for volcanic ash (Ag)

and four air filters. The first two ot these filters were collected

on February 1 close to and distant from the volcano vent. The last

two filters were collected later on February 18 and 20, respectively,

following an eruption characterized by steam instead of by volatile

compounds of sulfur, etc. that are usually associated with volcanic

eruptions. The higher concentrations in the last two samples for the

"crustal" elements indicates a higher ash content in the volcanic

;i plume.

A comparison of the varying composition of the plume samples can be obtained by calculating enrichment factors relative to the ash

I sample. The calculation is made by using the following equation:

' (X/A1).._

FT- filter

ash = (X/Al) ^ ash

I,

j where x refers to the concentration of the trace element of interest

and Al refers to the Al concentration. An EF , value near unity

ash ^

\ indicates that this element is associated with bulk ash. The EF , ash

i values for these samples are given in table 3. The EF values of the

non-volatile elements (table 3a) are all quite close to unity and re- present ash in the plume. The difference for these elements on the

two sample sets represents compositional variations of the ash during

the eruptive cycles. The volatile elements (table 3b) show higher

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Table 3. Enrichment Factors Relative to Ash for Elements on Suspended Particles.

Element AW

AW-6 AW-13 AW-16

a. Non-volat:ile Elements

Fe 1.7 1.8 1.3 1.0

Co 2.1 2.1 1.2 0.9

V 1.4 1.7 0.8 0.8

Ti 2.3 2.1 1.0 1.0

So 1.5 1.6 1.0 0.8

Mh 1.2 1.4 1.2 1.0

b. Volatile Elements

An >290 >260 >390 >280

CI 1070 520 42 2.3^

Br >360 >120 >3.4^ >1.6^

As 1100 700 7.5 38

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a_ , . Sea salt is primary source.

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enrichments on the first samples relative to the later sample, again

pointing to chemical variation between the two periods of the eruption.

It appears that the volatile elements are lost early in the eruption

as the primary magma chamber is initially vented, and their concentration decreases throughout the period of volcanic activity.

3. Radioactive Decay Studies

In our studies of the decay of radioactive nuclides, we have

published the results of our discovery of a new isomer, 47-min Eu-154m

and presented preliminary results from our studies of the decay of

100-min Pm-149 and the decay of 12-min Nd-151 to levels of Pm-151. As

Pm-151 is clearly a deformed nucleus and Pm-149 shows shell model

characteristics in its ground state, these studies are useful in

characterizing the transition from spherical to deformed nuclear

shapes. We have also measured the half life of the 376.6-keV level in

Ag-111 populated in the beta decay of Pd-111 isomers. The value of

16+ nsec suggests that this level has a l-particle-2-hole configuration

and a deformed shape.

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NEUTRON TRANSMUTATION DOPING OF SILICON

J. W. Cleland, R. D. Westbrook, R. F. Wood and R. T. Young

(Oak Ridge National Laboratory, Oak Ridge, TN)

Normal isotopic silicon contains 3.05% of Si-30 which transmutes

to P-31 after thermal neutron absorption, with a half-life of 2.6 hrs

This reaction can be used to introduce extremely uniform concentrations

of P, a standard n-type dopant in Si, thus eliminating the areal and

spatial inhomogeneities characteristic of conventional melt-growth doping

techniques. It has been demonstrated that the performance and yield of

high power Si rectifiers and thyristors can be significantly improved by

the use of neturon transmutation doped (NTD) Si, and the rate of introduction of P in NTD Si is such that doping concentrations of interest to

2 the semiconductor industry are readily attainable in many reactors.

Significant improvements in the performance of many types of Si

electronic devices may be attainable through the use of NTD Si but many

applications are still in the research stage. One interesting use is in

3 solar cell development, and another is that of obtaining a uniform dopant

distribution in polycrystalline Si regardless of the sample or polycrystal4 line grain size. It has been demonstrated that there is no aggregation

of P at the grain boundaries in NTD polysil as a consequence of annealing

to remove lattice damage, and macroscopic and microscopic spreading

resistance measurements on NTD Si epitaxial layers indicate that any

fluctuations in dopant distribution are virtually nonexistent.

The program of basic research on Photophysical Precesses of Solar

Energy Conversion in the Solid State Division at ORNL has been established

with the objective of finding methods for increasing the efficiency of

conversion of solar energy into forms suitable for terrestrial applications.

The program thus far has been concentrated on the study of NTD Si, and

particular attention is being given to studies of the characterization

and annealing of lattice damage introduced in both single crystal and

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polycrystalline Si. The vertical G-2 facility In the NBSR has been used

to introduce '^10 to 6 x 10 P cm in 1.25-in, dlam x 8-10 in. long

single or polysil ingots or ingot sections as a consequence of 1, 11, 7,

21, and 42 day irradiations, and the new vertical G-4 facility has been

used to introduce 10 to 10 P cm in 3-in. diam x 8-10 in. long single

or polysil Ingots or ingot sections as a consequence of 7, 21, and 42 day

irradiations. This program has benefited from the capable assistance

provided by the NBSR personnel.

1. W. E. Haas and M. S. Schnoller, J. Electron. Mater. 5^, 57 (1976).

2. See the first four articles in IEEE Trans. Electron Devices, Vol.

ED-23 , No. 8 (1976).

3. R. F. Wood, R. D. Westbrook, R. T. Young and J. W. Cleland, Proceedings,,

High Efficiency Radiation Damage Silicon Solar Cell Meeting^ NASA

Lewis Research Center, April 1977 (in press).

4. R. T. Young, J. W. Cleland, and R. F. Wood, Proceedings of the I2t'h

IEEE Photovoltaic Specialists Conference - 1976, (IEEE, New York,

1976), 76CH1142-9 ED, p. 65.

5. R. F. Wood, J. W. Cleland, P. H. Fleming, T. L. Polgreen,

R. D. Westbrook, and R. T. Young, Solid State Division Annu. Prog.

Rep. for Period ending April 50^ 1977, ORNL-5328 (in press).

POSITRON ANNIHILATION STUDIES

A. C. Ehrlich

(Naval Research Laboratory, Washington, DC)

The Metals Physics Branch of the Naval Research Laboratory has an ongoing program in the electronic structure of metals and alloys. One of

the very few methods available for direct study of the electronic structure of alloys is the angular correlation of positron annihilation radiation. This provides a direct measurement of the momentum spectrum of

the electrons in the material. From this one can deduce detailed information regarding the electronic structure.

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The goal of this work Is twofold; first, by determining the evolution of the electronic structure of a simple method like pure Cu as it

is alloyed with Zn it is hoped to deduce general information regarding

the electronic structure of alloys. Second, delineation of the CuZn

system should provide a basis for understanding one of the Hume-Rothery

rules, i.e.; the well known phase transition that occurs in a very large

number of Cu, Ag and Au based alloys at a conduction electron concentration of approximately 1.35 electrons/atom. In the CuZn alloy system

this occurs at 35 atomic percent Zn.

Due to the proximity and unique facilities of the NBS Nuclear

Reactor Facility to NRL, it has been possible to design a unique positron

annihilation apparatus which takes advantage of the fact that Cu can be

rendered strongly positron emitting by exposure to a flux of slow

neutrons. Thus the sample under study and the source of positrons are

one and the same and the effective positron source strength is much

greater than could be obtained using external positron sources. This in

turn permits the resolution of the yi^ay momenta in two directions

(rather than the usual resolution in only one direction) while still re- taining a sufficiently high count rate to obtain the necessary statisical

precision.

During the past year measurements have been carried out on single

crystals of Cu, Cu_ Zn and Cu^^Zn„- in various crystallographic

oj Ij 11 Li

orientations. From these measurements it has been possible to deduce

the maximum conduction electron momentum in the crystallographic directions studies. This is closely related to the dimensions of the so called Fermi surface. What is found is that as Zn is added to Cu the

Fermi surface growth in the [100] direction is less than that in the

[110] direction in contrast to what has been generally assumed. Further,

the growth in both directions is greater than expected on the basis of

the rigid band model of electron structure. In contrast, the growth of

the well known "necks" in the [111] direction is slower than predicted

by the rigid band model.

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It has been suggested that possible contact of the [100] Fermi

radium and the BrilloiunZone boundary at 1.35 electrons/atom might be

responsible for the phase transformation undergone by many noble metal

alloys. Extrapolation of our data indicates that no contact will take

place at this electron concentration. Thus, future research will ex- amine other aspects of the conduction electron structure as well as possible anisotropies in the more tightly bound 3d electrons in Cu.

NEUTRON ACTIVATION ANALYSIS OF LUNAR SAMPLES AND METEORITES

Jan Hertogen, Marie- Josee Janssens, Herbert Palme,

Hiroshi Takahashi, Edward Anders

(Enrico Fermi Institute, University of Chicago, Chicago, IL)

We have continued our analysis of breccias from the lunar highlands,

in order to identify meteoritic material from the intense bombardment

four billion years ago. The elements analyzed are: Ag, Au, Bi, Br, Cd,

Cs, Ge, In, Ir, Ni, Os , Pd, Rb , Re, Sb , Se, Te, Tl, U. and Zn. Nine

discrete meteorite types have been recognized, each apparently derived

from an impacting body in the 10-100 km size range. Several of these

bodies have compositions complementary to that of the Moon, and may

comprise left-over planetesimals from the Earth's neighborhood.

166
F. Staff Roster

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167
STAFF ROSTER

NON-RRD NBS STAFF LOCATED AT REACTOR

Division 240.01

P. R. Cassldy

K. Eggert

T. Hobbs

F. Moore

J. J. Shublak

Division 240.05

M. Baler

R. A. Dallatore

C. Elsenhauer

D. Gilliam

J. A. Grundl

E. McGarry

I. G. Schroder

R. Schwartz

V. Spiegel

Division 310.08

D. Anderson

J. Bailey

J. Blackman

B. Carpenter

R. Fleming

M. Gallorini

T. Gills

C. Grabnegger

S. Harrison

G. Hyde

R. Lindstrom

G. Lutz

J. Maples

L. Pilione

H. Rook

N. Sato

GUEST WORKERS AND COLLABORATORS

Division 232.06

R. D. Deslattes

E. G. Kessler

W. C. Sauder

J. Snyder

Division 240.05

C

.

Bowman

K. Duvall

H. Heaton

G. Tamaze

Division 300.00

H. Berger

L. McClendon

Division 310.00

P. LaFleur

Division 310.01

D. Sweger

Division 311.03

C. Han

Division 311.05

R. Bowen

M. Mathew

L. Schroeder

Division 312.02

J. Early

R. Reno

Division 313.03

D. B. Monor

R. S. Roth

Division 313.04

G. J. Rosasco

168
STAFF ROSTER

Division 313.06

A. B. Mighell

W. Thurber

Division 461.02

P . Brown

Argonne National Laboratory

R. Armani

H. Flotow

ARahman

K. Skold

S Susman

Battelle, N. W.

W. Nicholson

Bell Laboratory

D. Moncton

Brookhaven National Laboratory

L. Passell

W. Thomllnson

Federal Bureau of Investigation

D. B. Davies

J. Haverkost

J. W. Kilty

E. Mitchell

J. P. Riley

Food and Drug Administration

D. Daly

M. Friedman

J. T. Tanner

Harry Diamond Laboratory

C. Heimbach

NASA-Langley Research Center

R. Buckingham

National Institutes of Health

D. Davies

R. Frank

W. Hagins

W. Robinson

Naval Air Defense Command

M. Stellabotte

W. Williams

Naval Air Rework Facility

R. Chavez

Naval Research Laboratory

P. D 'Antonio

B. Das

A. Ehrllch

J. Karle

N. Koon

F. Lepple

Naval Surface Weapons Center

(White Oak Laboratory)

H. Alperin

D. Polansky

R. Williams

Oak Ridge National Laboratory

J. Cleland

M. Mostollor

H. Smith

R. Westbrook

R. Wood

R. Young

Picatinny Arsenal

N. Chesser

C. S. Choi

H. J. Prask

S. Trevino

169
STAFF ROSTER

Smithsonian Institution

M. Blackman

T. Chase

J. Mishara

S. O'Dell

L

.

Zacherman

U. S. Geological Survey

P. Baedecker

J. Morgan

J . J . Rowe

U. S. Treasury Department

J. M. Hoffman

W. Kinard

L. Reid

American University

R. Abbundi

R. A. Segnan

Colorado State University

C. E. Patton

Georgetown University

K. Barkigia

C. Quicksall

Harvard University

D. O'Brien

R. Wilson

Howard University

G. A. Ferguson

Reed College

W. Parker

Royal Canadian Military Academy

L. Bennett

University of California

(Lawrence Livermore Laboratories ) J . Browne

S . Hankins

University of Connecticut

J. Budnick

University of Chicago

E. Anders

J. Hertogen

M. Janssens

H. Palme

H. Takanashi

University of Maryland

D. Anderson

C. Choquette

W. Cunningham

M. Failey

P. Gallagher

M. Germani

B. Glagola

M. Glascock

D. Glotfelty

G. Gordon

G. Kowalczyk

E. Lepel

J. Levkoff

J . Lynn

J. Muhlbaier

D

.

Reamer

E. Schneider

M. Small

P. Solomon

E. Sombrito

K. Steffansson

W. Walters

M. Yiu

W. Zoller

U. S. Naval Academy

C. S. Schneider

170
STAFF ROSTER

University of Paris

B. Le Neindre

University of Pittsburgh

S . Sankar

W. Wallace

University of Rhode Island

S. J. Pickart

University of Saarlande

(West Germany)

K. Michel

J. Naudts

University of Salford (U.K.)

D. Martin

University of Wisconsin

J. Hinkley

H. Yu

Allied Chemical Corporation

G. Liebowitz

A. Maeland

R. 0' Handy

Caterpillar Tractor Company

W. P. Evans

General Electric Company

F. Lubursky

Monsanto Research Corporation

W. Brotherton

Oldelft Corporation

D. Bracher

Zerox Corporation

E. Stein

171
G. Publications

COLLABORATIVE PROGRAMS

ALPERIN, H. A., CULLEN, J. R. , CLARK, A. E. and CALLEN, E., "Amorphous

Magnetism in Bulk Samples of Terbium Iron Alloys," Physioa^ 86-88B,

767 (1977).

CHOI, C. S. and PRINCE, E., "Refinement of a-Lead Azide by Neutron

Diffraction," (to be published).

CHOI, C. S., PRASK, H. J., PRINCE, E. "Ammonium Percholorate: Reinvestigation of the Crystal Structure at 298K," Acta Cryst. 1332 , 2919 (1976).

GLINKA, C. J., ROWE, J. M. , RUSH, J. J., RAHMAN, SINKAR, and FLOTOW, H.,

"Inelastic Neutron Scattering Lineshapes in PdD^ f;q'" ^^° ^^ published)

.

GLINKA, C. J., MINKIEWICZ, V. J., and PASSELL, L., "Small-Angle Critical

Neutron Scattering," (to be published).

GLINKA, C. J., ROWE, J. M. , RUSH, J. J., LIBOWITZ , G. G., and MAELAND , A.,

"The Lattice Vibrations of CeD -i 9

» " Solid State Communications

3

22, pp. 541-544 (1977).

MARTIN D. J., and RHYNE, J. J., "Re-analysis of Dysprosium Magnetostriction,

(to be published)

.

MASSA, N. E., MITRA, S. S., PRASK, H., SINGH, R. S., and TREVINO, S. F.,

"Infrared-Active Lattice Vibrations in Alkali Azides," J. of Chem.

Phys., 6_7, 1, 173-179 (1977).

PICKART, S. J., ALPERIN, H. A., RHYNE, J. J., "Small Angle Magnetic

Scattering from a Dilute Amorphous Fe(Tb) Alloy," (to be published).

PICKART, S. J., "Small Angle Magnetic Scattering in Amorphous TbFe^."

Proc, of Conf. on Magnetic Scattering^ Troy, NY (1977).

RHYNE, J. J., "Magnetic Materials," Encyclopedia of Physics, edited by

R. G. Lerner and G. L. Trigg, Dowden, Hutchinson and Ross, Inc.

(to be published)

.

RHYNE, J. J., "Amorphous Magnetic Rare Earth Alloys," Chapter 16, Handhook on the Physics and Chemistry of Rare Earth3 edited by

K. A. Gschneidner and L. Eyring, (1977).

172
PUBLICATIONS

ROWE, J. M. and RUSH, J. J., "The Dynamics of Hydrogen in Metals,"

IAEA Conf. on Neutron Inelastic Scattering^ Vienna, Austria, (1977).

ROWE, J. M. , RUSH, J. J. and PRINCE, E., "Neutron Diffraction Study of

the Structure and Phase Transitions of Alkali Cyanide Crystals,"

J. Chem. Phys., 61, 11, 5147-49 (1977).

SANTORO, A., ROTH, R. S. and MINOR, D., "Neutron Powders Diffraction

Study of M-LlTa„Oo, Acta. Cryst., (to be published).

SCHROEDER, L. W. , PRINCE, E., "Hydrogen-Bonded Dimers in Tin (II) Hydrogen

Phosphate," 4cta. Cryst.^ B32, 3309, (1976).

SHORTEN, F. J., "NBS Reactor: Summary of Activities, July 1975 to

June 1976," NBS Techniaal Note, 939, (1977).

TREVINO, S. F., FARR, M. K. , GIGUERE , P. A., ARNAU, J. L., "The Lattice

Dynamics of the Deuterium Peroxide Crystals," (to be published).

WLODAWER, A., SANTORO, A., "Flat Cone Diffractometer Utilizing a Linear

Position Sensitive Detector," (to be published).

WLODAWER, A., ROBERTS, J. and HOLCENBERG, J. S., "Characterization of

Crystals of L-Glutaminase-Asparaginase from Acinetobacter Glutamlnasiflcans and Pseudomonas 7A," J. Mol. Biol. 112, 515-519 (1977).

173
PUBLICATIONS

INDEPENDENT PROGRAMS

BARNES, I. L,, ROOK, H. L., MURPHY, T. J., "The NBS Program for Standards

for Trace Inorganic Analysis in the Marine Environment," Proc. Tech.

Review of Interagenay Marine Res. Prog. Associated with Energy

Development (1977)

.

BOWEN, R. L., MCCLENDON, L. T. and GILLS, T. E., "Adhesive Bonding of

Various Materials to Hard Tooth Tissues XV: Sorption of Mordant

Ions Evaluated by Neutron Activation Analysis," (to be published).

BOYER, K. W., TANNER, J. T. and GAJAN, R. , "Multielement Analysis

Techniques at the Food and Drug Administration," American Laboratory

(to be published)

.

CAPAR, S., TANNER, J. T., FRIEDMAN, M. H. and BOYER, K. W. , "Multielement

Analysis of Animal Waste Material," Environmental Science and

Technology 3 (to be published)

.

CARPENTER, B. S. and REIMER, G. M. , "Uranium Analysis of Natural Waters

by Fission Tracks," ANS Transactions, 2_6, (1977).

CARPENTER, B. S., "Mapping ana Detecting Selective Elements by Nuclear

Track Technique," Proc. of the Buclear Methods in Environmental

and Energy Conf. (1977)

.

CARPENTER, B. S. and REIMER, G. M., "Homogeneity Considerations in Trace

Analysis Using the Nuclear Track Technique," Proa, of the Seventh

Materials Research Symposium, NBS (1976)

.

CARPENTER, B. S., SAMUEL, D., WASSERMAN, I., and YUWILER, A., "A Study

of Lithium Uptake and Location in the Brain Using the Nuclear Track

Technique," Proc. of the 1976 Modern Trends in Activation Analysis

Conference, Munich, Germany (1976).

CARPENTER, B. S. and MYKLEBUST, R. L., "Comparative Analysis for Boron

in Steel by Ion Microprobe Mass Analyzer and the Nuclear Track

Technique," Analytica Chimica Acta. Vol. 91, p. 409-411 (1976).

DOWTY, E., KEIL, K. , PRINZ , M. , GRAY, J., and TAKAHASHI , H. , "Metoritefree Apollo 15 KREEP , " Proc. 7th Lunar Sci. Conf. Geochim. Acta,

Suppl. 7, 1833-1844 (1976).

EISENHAUER, C. M. , GRUNDL, J. A. and FABRY, A., "Neutron Transport

Calculations for the Intermediate-Energy Standard Neutron Field

(ISNF) at the National Bureau of Standards," Proc. of International

Specialists Symposium on Neutron Standards and Applications, (to j be published)

.

j 174 '
PUBLICATIONS

FARBER, T. M. , RITTER, D. L., WEINBERGER, M. A., BIERBOWER, G.

,

TANNER, J. T., FRIEDMAN, M. H. , CARTER, C. J., EARL, F. L., and

VANLOON, E. J., "The Toxicity of Brominated Sesame Oil and

Brominated Soybeam Oil in Minature Swine," Toxicology _5, 319-336

(1976).

FILBY, R. H. and CARPENTER, B. S., "Application of Nuclear Techniques

to the Characterization of Trace Elements in Petroleum and Coal

Conversion Products," ANS Transactions 26^, (1977).

FRIEDMAN, M. H. and TANNER, J. T., "A Computer Language for Reducing

Neutron Activation Analysis Data and Its Application to the Prolems of the Food and Drug Administration," Journal of RadioanaZytical

Chemistry3 (to be published)

GILLS, T. E. and MCCLENDON, L. T., "Role of Neutron Activation Analysis

in the Evaluation of Sampling, Storage and Analysis Methodology on Samples for the National Environmental Banking System," Proc. of

the 1976 Modern Trends in Activation Analysis, (1976) .

GILLS, T. E., ROOK, H. L. and LAFLEUR, P. D., "Assessment of Gunshot

Residue Detection Using Neutron Activation Analysis, Report to the

Law Enforcement Standards Prograrrij LESP Report (1976) .

GILLS, T. E., "Selective Radiochemical Separation for the Activation

Analysis of NBS Botanical Standard Reference Materials," (to be

published)

GILLS, T. E., GALLORINI, M. and GREENBERG, R. R. , "The Measurement of

Selected Toxic Elements in Biological Matrices Using Radiochemical

Activation Analysis, Proc. of the Third International Conf. on Nuclear Methods in Environmental and Energy Research, {1.^11^ .

GILLIAM, D. M., "Integral Measurement Results in Standard Fields,"

Proc. of International Specialists Symposium on Neutron Standards

and Applications, pp. 209-303 (1977).

GLADNEY, E. S., SMALL, J. A., GORDON, G. E. and ZOLLER, W. H.,

"Compositions and Size Distribution of In-Stack Particulate

Material at a Coal-Fired Power Plant," Atmos. Environ. 10,

1071-1077 (1976).

GORDON, G. E., ANDERSON, D., FAILEY, M. , WALTER, W. , ZOLLER, W. H. and

LINDSTROM, R. M. , "Prompt Gamma-Ray Neutron Activation Analysis,"

Proc. of Srd International Conf. Nuclear Methods and Environmental

Energy Research, (to be published)

175
PUBLICATIONS

GREENBERG, R. R. , ZOLLER, W. H. and GORDON, G. E., "The Contribution of

Refuse Incineration to Urban Aerosols," Proc. of the Fourth Joint

Conf. on Sensing of Environmental Pollutants^, (to be published).

GREENBERG, R. R. , ZOLLER, W. H. and GORDON, G. E., "Composition and

Size Distributions of Particles Released in Refuse Incineration,"

(to be published)

.

GROS,^J., TAKAHASHI, H. , HERTOGEN, J., MORTAN, J., ANDERO, E.,

"Composition of the Projectiles That Bombarded the Lunar Highlands,"

Geoohim Cosmochim. Aata^ Suppl. 7, 2402-2425 (1976).

GRUNDL, J. and EISENHAUER, C, "Fission Reaction Rate Standards and

Applications," Proa, of International Specialists Symposium on Neutron Standards and Applications, pp. 156-164 (1976).

GRUNDL, J. A., SPIEGEL, V., EISENHAUER, CM., HEATON II, H. T. and

GILLIAM, D. M. , "A Californium-252 Fission Spectrum Irradiation

Facility for Neutron Reaction Rate Measurements," Nucl. Tech. Vol. 32,

pp. 315-319 (1977),

HARRISON, S. H. and BLANCHARD, D., "Fine Paper Identification by Trace

Elements Profiles of Clay Fillers," (to be published).

HARRISON, S. H., "Determination of Vanadium and Manganese in NBS-SRM

Tissues, Sediments, and Waters by Neutron Activation Analysis,"

mS SPEC. PUBL. 260(1977).

HARRISON, S. H., LAFLEUR, P. D. and ZOLLER, W. , "Sampling and Sample

Handling for Activation Analysis of River Water," Proc. of the

Seventh Materials Research Symposium, NBS (1976)

.

HERTOGEN, J., JANS SENS, M. , TAKAHASHI, H. , PALME, H. and ANDERS, E.,

"Lunar Basins and Craters: Evidence for Systematic Compositional

Changes of Bombarding Populations," (to be published).

HERTOGEN, J., JANS SENS , M. , "Is Osmium Chemically Fractionated on the

Moon?" (to be published)

.

HOPKE, P. K., GLADNEY, E. S., GORDON, G. E., ZOLLER, W. H. , and JONES, A. G.

"The Use of Multivariate Analyses to Identify Sources of Selected

Elements in the Boston Urban Aerosol," Atoms. Environ. 10, 1015-1025

(1976).

HUGHES, :E. E., rook, H. L., DEARDORFF, E. R., MARGESON, J. H. and

FUERST, R. G., "Operational Characteristics of Nitrogen Dioxide

Permeation Devices," (to be published).

176
PUBLICATIONS

ROOK, H. L., MOODY, J. R. , PAULSEN, P. J. and RAINS, T. C, "Stability

of Elemental Components in a Multi-trace Element Water Standard,"

Vvoc. of the Mineval Cycling Symposium, Savannah River Laboratory

(1977).

ROOK, H. L., "The Determination of Iodine in Biological and Environmental

Standard Reference Materials," J. of Radioanal . Chem. , 39, 1-2,

p. 351-358 (1977).

ROOK, H. L. and WOLF, W. , "The Quantitative Determination of Volatile

Trace Elements in NBS Biological SRM 1569, Brewers Yeast," Proa,

of 11th Annual Conf. on Tvace Substances in Environmental Health,

Columbia, MO (1977)

ROOK, H. L., "Environmental Water Standards Applied to Health Effects

Studies," Fvoc. of the 1976 Modern Trends in Activation Analysis,

(1976).

SCHNEIDER, E. W., GLASCOCK, M. D., GALLAGHER, P. W., WALTERS, W. B.

and MEYER, R. A., "Identification of Low-Lying 0^ State in ^'^^Y.e Populated in the Decay of ^'^^Cs,'' Bull Am. Phys. Soc. 22, 596 (1977)

SCHWARTZ, R. B., "Calibration and Use of Filtered Beams," Proc. Int.

Specialists Symp. on Neutron Standards and Applications, NBS,

(to be published)

SEGEBADE, C, LUTZ , G. J. and REIMERS , P., "Photon Activation Analysis

of Coins and Objects of Art," 1976 Modern Trends p. 1171 (to be

published)

SEGEBADE, C, LUTZ, G. J. and WEISS, P., "Quantitative Evaluation of

Interference Reactions in Photon Activation Analysis," 1976 Modern

Trends (to be published)

TANNER, J. T. and FRIEDMAN, M. H. "Neutron Activation Analysis for Trace

Elements in Foods," Proc. of Conf. Modern Trends in Activation

Analysis, Munich, Germany (1976).

TANNER, J. T. and FRIEDMAN, M. H. , "Neutron Activation Analysis for

Trace Elements in Foods," Journal of Radioanalytical Chemistry

37, 529-38 (1977).

THURBER, W. R. and CARPENTER, B. S., "Determination of Boron in Silicon

by the Nuclear Track Technique and Correlations with Resistivity

and Capacitance-Voltage Measurements," (to be published).

WAGNER, G. A. and CARPENTER, B. S., "Liquid Nitrogen Enhancement of

Partially Annealed Fission Tracks in Glass," Nature, 261 , p. 182

(1977).

178
PUBLICATIONS

KOWALCZYK, G. S., CROQUETTE, C. E. and GORDON, G. E., "Chemical Element

Balances and Identification of Air Pollution Sources in

Washington, DC, Atoms. Environ, (to be published).

LINDSTROM. R. M. , "Radial Efficiency Gradients in Ge(Li) Gamma Detectors,"

Proa, of the 1976 Modern Trends in Activation Analysis (1976)

.

LINDSTROM, R. M. and FLEMING, R. , "Optimized Determination of Aluminum

in High Purity Silicon," (to be published).

LUTZ, G. J., STEMPLE, J. S. and ROOK, H. L., "Evaluation by Activation

Analysis of Elemental Retention in Biological Samples After Low

Temperature Ashing," J. of Radioanal. Chem. ^ 39^, 1-2, p. 277-283

(1977).

LUTZ, G. J., "Evaluation of Elemental Retention in Biological and Organic

Samples After Low Temperature Ashing by Activation Analysis,"

Proa, of the 1976 Modern Trends in Activation Analysis, (1976)

.

MCCLENDON, L. T. and GILLS, T. E. , "Trace Element Characterization of

Automobile Headlamp Glass Using Neutron Activation Analysis,"

(to be published)

.

MCGARRY, E. D. and GILLIAM, D. M. , "Standardization of Fast Pulse

Reactor Dosimetry," Proc . of International Specialists Symposium

on Neutron Standards and Applications, pp. 335-341, (1977).

MOODY, J. R. and LINDSTROM, R. M. , "The Selection and Cleaning of

Containers for Trace Element Samples," (to be published).

MOODY, J. R., PAULSER, P. J., RAINS, R. C. and ROOK, H. L. , "The Preparation and Certification of Trace Mercury in Water Standard

Reference Materials," Proc. of the Seventh Materials Research

Symposium, NBS (1976).

MORGAN, J., HIGUCHI, H. , TAKAHASHI , H. and HERTOGEN, J., "A Chrondritic

Eucrite Parent Body: Interface From Trace Elements," (to be

published)

.

MORGAN, J., GROS, J., TAKAHASHI, H. , and Hertogen, J., "Lunar Briccia

732 is: Siderophile and Volatile Elements," Proc. 7th Lunar Sci.

Conf. Geochim. Cosmochim. Acta., Suppl. 1 2189-2199 (1976).

ROOK, H. L. and GOLDSTEIN, G., "Environmental Specimen Bank Workshop,"

ms Spec. Puhl. (to be published).

177
PUBLICATIONS

YULE, H, P. and ROOK, H. L. , "A Comparison of Photopeak Area Computation

Methodologies," J. of Radioanal. Chem.j 39 (1977).

ZOLLER, W. H., WALTERS, W. B., GALLAGHER, P. W. and MEYER, R. A.

"Radioactive Decay of 47-min IS^^uin^M p]^yg^ ^^^^ C13^ 2024-2032

(1976).

179
NBS-H4A (REV, 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-969

2, Gov't Accession

No.

4. TITLE AND SUBTITLE

NBS REACTOR: Summary of Activities

July 1976 to June 1977

3. Recipient's Accession No.

5. Publication Date April 1978

6. Performing Organization Code

7. AUTHOR(S)

Frederick J. Shorten

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as item 9

13. Type of Report & Period Covered

7 /1/76 to 6/30/77

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less (actual summary of most si^iticant information. If document includes a significant

bibliography or literature survey, mention it here.) This report summarizes all those programs which depend on the NBS reactor.

It covers the period from July 1976 through June 1977. The programs range from

the use of neutron beams to study the structure and dynamics of materials through

nuclear physics and neutron standards to sample irradiations for activation analysis,

isotope production, radiation effects studies, neutron radiograohy and nondestructive

evaluations.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Activation analysis; crystal structure; diffraction; isotopes; molecular dynamics;

neutron; neutron radiography; nondestructive evaluation; nuclear reactor; radiation

18. AVAILABILITY |^ Unlimited

I ! For Official Distribution. Do Not Release to NTIS

I x! Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C. 20402, SD Stock No. SN003-003 -

I I Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

,19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

UNCLASSIFIED

188

20. SECURITY CLASS

(THIS PAGE)

22. Price $3.50

UNCLASSIFIED

USCOMM.DC 29042-P7

i> U. S. GOVERNMENT PRINTING OFFICE : 1978 261-238/57
NBS TECHNICAL PUBLICATIONS

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of the National Bureau of Standards reports NBS research and development in those disciplines of the physical and

engineering sciences in which the Bureau is active. These

include physics, chemistry, engineering, mathematics, and computer sciences. Papers cover a broad range of subjects, with major emphasis on measurement methodology, and

"i the basic technology underlying standardization. Also in- cluded from time to time are survey articles on topics closely

. related to the Bureau's technical and scientific programs. As

a special service to subscribers each issue contains complete

citations to all recent NBS publications in NBS and non- NBS media. Issued six times a year. Annual subscription: domestic $17.00; foreign $21.25. Single copy, $3.00 domestic;

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This monthly magazine is published to inform scientists, engineers, businessmen, industry, teachers, students, and

consumers of the latest advances in science and technology,

with primary emphasis on the work at NBS. The magazine

highlights and reviews such issues as energy research, fire protection, building technology, metric conversion, pollution

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and others engaged in scientific and technical work.

National Standard Reference Data Series—Provides quantitative data on the physical and chemical properties of

materials, compiled from the world's hterature and critically evaluated. Developed under a world-wide program co- ordinated by NBS. Program under authority of National Standard Data Act (Public Law 90-396).

NOTE: At present the principal publication outlet for these data is the Journal of Physical and Chemical Reference Data (JPCRD) published quarterly for NBS by the American Chemical Society (ACS) and the American Institute of

Physics (AIP). Subscriptions, reprints, and supplements

available from ACS, 1155 Sixteenth St. N.'W., Wash., D.C.

20056.

Building Science Series—Disseminates technical information developed at the Bureau on building materials, components,

systems, and whole structures. The series presents research

results, test methods, and performance criteria related to the

structural and environmental functions and the durability and safety characteristics of building elements and systems. Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a subject.

Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often

serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures

published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The purpose

of the standards is to establish nationally recognized require- ments for products, and to provide all concerned interests with a basis for common understanding of the characteristics of the products. NBS administers this program as a supple- ment to the activities of the private sector standardizing

organizations.

Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and

illustrations provide useful background knowledge for shopping in today's technological marketplace.

Order above NBS publications from: Superintendent of Documents, Government Printing Office, Washington, D.C.

20402. Order following NBS publications—NBSIR's and FIPS from

the National Technical Information Services, Springfield, Va. 22161.

Federal Information Processing Standards Publications (FIPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register.

Register serves as the official source of information in the Federal Government regarding standards issued by NBS

pursuant to the Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat. 1127), and as implemented by Executive Order 11717

(38 FR 12315, dated May 11, 1973) and Part 6 of Tide 15 CFR (Code of Federal Regulations).

NBS Interagency Reports (NBSIR)—A special series of

interim or final reports on work performed by NBS for outside sponsors (both government and non-government).

In general, initial distribution is handled by the sponsor;

public distribution is by the National Technical Information

Services (Springfield, Va. 22161) in paper copy or microfiche form.

BIBLIOGRAPHIC SUBSCRIPTION SERVICES

Hie foDowing current-awareness and literature-survey bibli- ographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A litera- ture survey issued biweekly. Annual subscription: Domestic, $25.00; Foreign, $30.00.

Liquified Natural Gas. A literature survey issued quarterly.

Annual subscription: $20.00.

Superconducting Devices and Materials. A literature survey

issued quarterly. Annual subscription: $30.00. Send subscription orders and remittances for the preceding bibliographic

services to National Bureau of Standards, Cryogenic Data

Center (275.02) Boulder, Colorado 80302.
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington. DC. 20234

OFFICIAL BUSINESS

Penalty for Private Use. $300

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