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National Bureau of Standards

Library, E-01 Admin. Bidg.

OCT 6 1981

131137

ICO

NBS TECHNICAL NOTE 995

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

NBS Reactor:

ummary of Activities

uly 1977 to June 1978
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 promote public safety. The Bureau's technical work is performed by the National Measurement Laboratory, the National Engineering Laboratory,

and the Institute for Computer Sciences and Technology.

THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement; coordinates the system with measurement

systems of other nations and furnishes essential services leading to accurate and uniform

physical and chemical measurement throughout the Nation's scientific community, industry,

and commerce; conducts materials research leading to improved methods of measurement,

standards, and data on the properties of materials needed by industry, commerce, educational

institutions, and Government; provides advisory and research services to other Government

Agencies; develops, produces, and distributes Standard Reference Materials; and provides

calibration services. The Laboratory consists of the following centers:

Absolute Physical Quantities2 — Radiation Research — Thermodynamics and

Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical

services to users in the public and private sectors to address national needs and to solve national problems in the public interest; conducts research in engineering and applied science

in support of objectives in these efforts; builds and maintains competence in the necessary

disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities; provides engineering measurement traceability services; develops test methods and proposes engineering standards and code changes; develops and

proposes new engineering practices; and develops and improves mechanisms to transfer

results of its research to the utlimate user. The Laboratory consists of the following centers:

Applied Mathematics — Electronics and Electrical Engineering2 — Mechanical

Engineering and Process Technology2 — Building Technology — Fire Research —

Consumer Product Technology — Field Methods.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts

research and provides scientific and technical services to aid Federal Agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal Agencies; and

provides the technical foundation for computer-related policies of the Federal Government.

The Institute consists of the following divisions:

Systems and Software — Computer Systems Engineering — Information Technology.

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

2 Some divisions within the center are located at Boulder, Colorado, 80303.

The National Bureau of Standards was reorganized, effective April 9, 1978.
National TSr^ of Standard:

QlCJ

NBS Reactor: Summary of Activities

July 1977 to June 1978 ^

Frederick J. Shorten, Editor

Reactor Radiation Division

National Measurement Laboratory

National Bureau of Standards

Washington, D.C. 20234

^°P

Co,

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

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued May 1979
National Bureau of Standards Technical Note 995

Nat. Bur. Stand. (U.S.), Tech. Note 995, 147 pages (May. 1979) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1979

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Stock No. 003-003-02070-2 Price $4.50

(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 secientists

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, and C.

Freedman for efforts in typing manuscripts.

iR. S. Carter

Chief, Reactor Radiation Division

National Bureau of Standards

xv
ABSTRACT

This report summarizes all those programs which depend on the NBS

reactor. It covers the period from July 1977 through June 1978. 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.
TABLE OF CONTENTS

FOREWORD iii

ABSTRACT v

A. REACTOR RADIATION DIVISION PROGRAMS 1

The Lattice Dynamics of PdDn 00 1

(J . oo Influence of Hydrogen on the Magnetic Properties

of Rare Earth Compounds 3

Studies of Robust/Resistant Refinement Techniques

Observation of a Ferroelectric Transition in Zinc Cyanide ... 9

Construction of a Powder Dif f ractometer with 5 Detectors .... 10

Neutron Diffraction Powder Profile Analysis of

Manganese Fluoroapatite 10

Powder Diffraction Study of Ta„W0„ 12

Crystallography of Ribonuclease-A 20

Rotational Dynamics and Phase Transitions in

(KCN) (KBr) 22

X -L X

CN

- IONS in KC1, KBr 24

Neutrino Scattering and Weak-Interaction Gauge Theories .... 26

Isotopic Shifts of Phonons 28

Neutron Radiography 29

B. RRD COLLABORATIVE PROGRAMS 34

Application of Neutron Diffraction to Non-Destructive

Testing Problems 34

High Temperature Structure of NH,N0„ (Phase II) 39

Refinement of Dipara-Anthracene Structure 41

The Pressure-Induced Phase Transition in

Sodium Nitrate 43

The Structure of Sodium Zinc Chloride Trihydrate 46

Spin Excitations in Amorphous TransitionMetal Glasses 48

Magnetic Excitations in HoFe9 49

Magnetic Neutron Scattering From Amorphous TmFe_ 55

VI
TABLE OF CONTENTS

Measurements of the Crystal-Field Splittings

in Superconducting (CE HO )RU Alloys 58

Low Temperature Phase Transition in Cs NaPrCl 61

Crystal-Field Excitations in (RE)Mo,Se

fi 62

A Triple Axis Polarized Beam Spectrometer 66

Studies of the Effects of Deuterium in Titanium 68

Structure and Dynamics of 8 V~D 68

Chain Deformation in Rubber 69

C. NON-RRD NBS PROGRAMS 74

Activation Analysis: Summary of 1978 Activities 74

Fissionable Deposit Mass Assay 114

Precision Gamma-Ray Wavelengths 116

Cavity Fission Neutron Source Irradiation Facility 120

D. SUMMARY OF REACTOR OPERATIONS 123

E. SERVICE PROGRAMS • 124

Activation Analysis Program of the Food and Drug

Administration at the NBSR 124

ATF'S Forensic Activation Analysis Program 126

F. STAFF ROSTER 128

G. PUBLICATIONS 133

Vll

A. Reactor Radiation Division Programs

THE LATTICE DYNAMICS OF PdD .88

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

There has been considerable experimental and theoretical interest

in recent years in the role of the lattice vibrations, particularly the

optic modes, in the inducement of high T superconductivity in the

PdH (D) system when x approaches unity. Thus far, information on the

phonon spectra in these materials has derived from coherent neutron

scattering measurements of the phonon dispersion curves in PdDQ go

and incoherent scattering measurements of the phonon density of states

in PdHfi go • However, at this concentration, which is the equilibrium

concentration at atomospheric pressure, palladium hydride does not become superconducting.

In order to obtain phonon data on a sample which is a superconductor, we have prepared, in collaboration with H. Flotow of

Argonne National Laboratory, a single crystal of palladium deuteride

with the composition PdD og« To reach this concentration, the crystal

was loaded with D2 gas in a specially designed high pressure scattering

cell under a pressure of 2 kbars. The final composition was determined

by a careful measurement of the lattice constant at 80K. At the con- centration PdDQ go, the crystal is expected to have a superconducting

transition between 4 to 5K.

We have carried out coherent inelastic neutron scattering measurements of both the optic and acoustic phonon dispersion curves along the

[100], [110] and [111] symmetry directions in the PdDQ^g crystal at

80K. The results of these measurements are summarized in figure 1

where the squares and circles refer to transverse and longitudinal modes,

respectively. For comparison, the dispersion curves for PdDQ go are

shown as solid lines in figure 1. From the figure \t is apparent that

there is rather little difference between the phonon spectra at these

two concentrations. In particular, we observe no change in the position
REACTOR RADIATION DIVISION PROGRAMS

(£00) —PdD063 150K —

1—

r Mi)

Figure 1.

0.2 0.40.6 0.8 0.1 0.8 0.6 0.4 0.2 0.2 0.4

Reduced Wave Vector Coordinate (£= aq x /2ir)

Data points are phonon frequencies measured in PdDQgg at 80K.

Squares and circles refer to longitudinal and transverse modes,

respectively. The solid curves are the corresponding dispersion

curves for PdDQ^^.

of the peak in the optic phonon density of states which occurs at 37 meV

due to the several nearly flat transverse phonon branches near this energy.

Neither is there any shift in the critical points of the acoustic phonon

density of states. The only significant shift in phonon frequencies

occurs along the [100] longitudinal optic branch where the frequencies

are 5 to 10% higher in PdDQ gg than in PdDg go. These results suggest

that whatever features of the phonon spectrum of palladium hydride

that are related to superconductivity are already present in the spectrum

for PdDQ 53. Beyond this concentration, changes in the electronic

properties due to the added hydrogen, rather than changes in the phonons,

are responsible for the onset of superconductivity.

2
REACTOR RADIATION DIVISION PROGRAMS

1. J. M. Rowe, J. J. Rush, H. G. Smith, M. Mostoller and H. E. Flotow,

Physical Review Letters 11,1297 (1974).

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

and H. E. Flotow, Physical Review B17, 488 (1978).

3. A. Rahman, K. Skold, C. Pelizzari, S. K. Sinha and H. E. Flotow,

Physical Review MA' 3630 (1976).

INFLUENCE OF HYDROGEN ON THE MAGNETIC PROPERTIES

OF RARE EARTH COMPOUNDS

J. J. Rhyne and G. E. Fish

and

S. G. Sankar and W. E. Wallace

(University of Pittsburgh, Pittsburgh, PA)

In the last few years it has been found that a large variety of rare earth-intermetallic compounds absorb large amounts of hydrogen,

generally at only moderately increased temperature and/or pressure;

forming hydride phases. The density of hydrogen atoms in these compounds

+22 3 often exceeds that of liquid hydrogen, approaching 6 x 10 atoms/cm . Due to the influence of hydrogen on the electronic density of states,

lattice parameter, crystal field screening, etc. , profound changes in the

magnetic interactions in rare earth compounds can occur on hydriding. We

have studied the effect of H on the sublattice magnetization in several

RFe„ (R = heavy rare earth) Laves phase compounds.

These compounds readily absorb hydrogen up to a concentration of

approximately 4 hydrogen atoms per formula unit. The hydride can be

made stable against desorption of hydrogen at room temperature and

ambient pressure by poisoning the surface with S0» . X-ray diffraction

has shown that the materials remain in the Laves phase structure, but

exhibit a significant increase in lattice parameter a . For example,

a = 7.28 A for ErFe„ and is increased to a =7.83 for ErFe H„ _

o 2 o 2 3.9
REACTOR RADIATION DIVISION PROGRAMS

The heavy rare earth (RFe

?

) compounds (non-hydride) are ferrimagnetic

with the R moment equal to the free ion moment (at K) aligned antiparallel to the two Fe moments each equal to approximately 1.6 y . The

Curie temperatures of the RFe

? compounds range from 535 K for YFe

2 to

793 K for GdFe . 1

1 After hydriding, bulk magnetization data show the Curie temperatures to be significantly reduced from that of the pure compounds and to

be fairly sensitive to small change in hydrogen occupation and/or preferential occupation of sites. Because of the large crystal field

anisotropy (except for Gd) magnetic moment data on the compounds do not

saturate in normally available laboratory fields (-100 kOe) and thus a definitive determination of the full moment is not possible by convenSublattice Magnetic Moment

• ErFe 2 H 35 D ErFe 2

600

Figure 1. Sublattice magnetic moments as a function of temperature for

Er and Fe in ErFe£ and ErFe2H3 c. The uncertainty in the

moment shown is approximately + 0.3y]$ largely due to the effect

of the incoherent scattering of H.
REACTOR RADIATION DIVISION PROGRAMS

tional methods. Therefore, we have used neutron scattering to study the

effect of hydrogen on the sublattice magnetization and Curie temperature

of HoFe , ErFe and TmFe . In the hydride compounds, due to the unknown site occupancy of the

hydrogen, an absolute determination of the scattering intensity was made

by normalization to a copper powder. In the case of ErFe2H3 # 5 data were

taken on a deuterated sample which further reduced the incoherent con- tribution. Results for the sublattice moment on the R site are shown

in figures 1 and 2 for HoFe2D3,5, HoFe2, TmFe2H3 # 5, TmFe2, and on both

R and Fe sites for ErFe2H3.5 and ErFe2

_ 6

CD 4

- 5 c

u

EI 4

3

-

2 -

O TmFe 2 ^ • TmFe 2 H 35 D HoFe 2 HoFe 2 D 35 \D

\b

- \

o \

^vO

••\ \^

\B

, .. L. • ^~ ,x«l | 100 200 300

T(K)

400 500 600

Figure 2. Tm and Ho sublattice moment versus temperature for TmFe2

,

HoFe2, and for TmFe2Hq c and HoFe2D3 > 5

> The overall Curie

temperature of the Tm hydride is approximately 300 K and of the

Ho deuteride 320 K.
REACTOR RADIATION DIVISION PROGRAMS

As is evident from the figures, the overall Curie temperature is

reduced by more than 20% on hydriding. This reflects a reduction in

Fe-Fe exchange due to the increased lattice parameter and Fe-Fe exchange

due to the increased lattice parameter and Fe-Fe interatomic spacing.

The magnitude of the iron sublattice moment and its relatively flat

temperature dependence remain essentially unchanged. The effect on the

rare earth is much more dramatic. First, the K moment in the hydride

is sharply reduced from its free ion value. In addition the moment rapidly

decreases with elevated temperature, reaching essentially zero in ErFe2~

H3.5 below the overall Curie temperature. These features suggest a severe weakening of the R-Fe (and R-R) exchange coupling. The Fe-Fe coupling

may proceed by nearest-neighbor direct overlap exchange which would not

be strongly influenced.

The weaker rare-earth exchange in the hydride compound suggests also

that the crystal field interactions may perturb the energy levels away

from pure J states, effectively reducing the observed sublattice

moment. Inelastic neutron scattering studies are in progress to examine

the magnetic excitations. Alternately the loosely-coupled rare earth

moments may be "fanning" about the direction of the net iron exchange

field. The random occupation of the hydrogen sites can significantly

distort the local anisotropy field in a manner similar to that found in

2 amorphous rare earth alloys leading to a reduction in spatially

averaged moment as measured by the neutrons

1. Gualtieri, D. M. , Narasimhan, K.S.V.L., and Wallace, W. E., A. I. P. Conference Proceedings Series _34, 219(1976).

2. Rhyne, J. J., Schelleng, J. H. , and Koon, N. C, Phys. Rev. BIO , 4672(1974).
REACTOR RADIATION DIVISION PROGRAMS

STUDIES OF ROBUST/RESISTANT REFINEMENT TECHNIQUES

E. Prince

and

W. L. Nicholson

(Battelle Pacific Northwest Laboratories, Richland, WA)

Studies of the behavior of a robust/resistant modification of

the conventional least-squares algorithm used for crystal structure re- finement have continued. Previous work has shown the modified algorithm

to be "resistant", ie, that it is insensitive to small numbers of "outlier" points in the data, but a demonstration that the procedure is

also "robust", that it works for a broad range of error distributions,

requires that the error distributions in particular data sets be known.

Since the true error distribution in a real experimental data set is never accurately known, we have studied the behavior of the algorithm

for several synthetic data sets derived from the calculated structure

.factors for a known crystal structure by adding random errors generated

according to several error distributions.

Altogether, four data sets were refined:

1) The error distribution was Gaussian, with weights assigned

equal to the reciprocals of the variances of the individual

points;

2) An error distribution the same as in 1, but unit weights

used throughout;

3) A Gaussian error distribution contaminated by 10% of

another Gaussian distribution with a variance 9 times

greater; and

4) a long-tailed distribution derived by dividing a Gaussian

random variable.

Distribution 1 is the condition for which least-squares theoretically feives the best possible result.

For the other distributions, least-squares gives the best linear

estimates of the parameters of the model, but in general non-linear

estimates exist which are better. A robust procedure should nearly as well as least-squares for distribution 1, and as well or better for the

7
REACTOR RADIATION DIVISION PROGRAMS

other distributions.

Each data set was refined twice, once using the modified algorithm,

in which the weights are adjusted in each cycle according to the relation

w*=w(l-2X2+X4

) w'=0 >1,

where X=AF/ (ka) , and k is set equal to 9 times the median value of AF/a

in the previous cycle. The starting model in each case was the model

from which the error free structure factors were calculated. The standard deviations of the parameter estimates for the conventional refinement of distribution 1 were taken as a scale for comparison with all of

the others. The results are summarized in table 1. For each of the

8 refinements we give the unweighted R index (R=S | |Fo |-|Fc |

| /I JFo | )

,

the weighted R index (Rw=[E w ( |Fo

|

-|Fc | ) 2 /£w|Fo | 2

] 1 ^ 2>, and the slope

of a half-normal quantile-quantile plot2 of the differences between the

estimated parameters and their corrected values, divided by the standard deviations from distribution 1. For a properly weighted leastsquares fit to a linear model this slope should be 1.0. The fact that

it is not 1.0 for the least-squares refinement of distribution 1 is due

to the fact that the structure factor model is non-linear, so that

several iterations are required to find the minimum. It appears that

Table 1. Summary of results of refinement of synthetic data sets.

Distribution Conventional algorithm Robust/resistant algorithm

R Rw S R Rw S 1 0.018 0.023 1.2 0.018 0.021 1.2

2 0.018 0.020 1.4 0.017 0.017 1.2

3 0.022 0.028 1.8 0.022 0.024 1.6

4 0.082 0.137 9.9 0.028 0.032 1.6

the modified algorithm gives results almost identical to the conventional algorithm for distribution 1, slightly better results in cases 2 and

3, and very much better results in case 4. This suggests that the

8
REACTOR RADIATION DIVISION PROGRAMS

modified algorithm is seldom, if ever, inferior to the conventional one,

and is sometimes very markedly superior.

1. E. Prince and W. L. Nicholson, NBS Tech. Note 969 3 13 (1978).

2. S. C. Abrahams and E. T. Keve, Acta. Cryst. A27 , 157 (1971).

OBSERVATION OF A FERROELECTRIC TRANSITION IN ZINC CYANIDE.

E. Prince and J. M. Rowe

and

C. S. Choi

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

In previous annual reports we have described crystallographic

studies on sodium and postassium cyanides. Each of these alkali

cyanides is cubic at room temperature, with a disordered arrangement of

cyanide ions. In each there is a lower temperature phase with orthorhombic symmetry in which the cyanide ions are all parallel to one direction, but the sense of the C-N vector is random, and a still lower

temperature phase in which the C-N dipoles show antiferroelectric ordering. Zinc cyanide, Zn(CN)2 has a structure which is also cubic at room

temperature, but with a different space group from the alkali cyanides.

Each CN ion is parallel to a particular [111] direction, but, again, the sense of the CN vector is random. Dipole energy considerations would

lead one to expect a transition at some temperature to a tetragonal

2 (pseudo-cubic) ferroelectric phase at some low temperature. Mellor

looked for this transition, but did not find any evidence for it down

to 77K. In preliminary measurements on a crystal kindly supplied by

Prof. D. P. Shoemaker there are indications that a transition occurs between 40K and 50K. Additional measurements will be taken in an at-t tempt to confirm this transition.

1. J. M. Rowe, J. J. Rush, E. Prince, N. J. Chesser, S. Susman, and

D. G. Hinks, NBS Tech. Note 969 (1977).

2. J. Mellor, Thesis, M. I. T. (1962).

9
REACTOR RADIATION DIVISION PROGRAMS

CONSTRUCTION OF A POWDER DIFFRACTOMETER WITH 5 DECTECTORS

E. Prince and A. Santoro

The full potential of neutron powder dif fractometry and profile

analysis can only be realized if the resolution of the powder pattern

is the best practically obtainable, which implies a penalty in the

form of low intensity and correspondingly long counting times. On the

other hand, intensity is present in all parts of the powder diffraction

pattern all of the time, so great improvements in effeciency can be

obtained by measuring different parts of the diffraction pattern simultaneously. A detector shield has been designed for the dif fractometer

at BT-1 which has five independent collimators with a 20° angle between

each pair. It will be possible, for any given resolution, to collect

data 4 or 5 times faster than before. Installation and check-out of

this instrument will occur in the late summer and early fall of 1978.

NEUTRON DIFFRACTION POWDER PROFILE ANALYSIS

OF MANGANESE FLUOROAPATITE

A. Santoro

and

L. W. Schroeder

(Food and Drug Administration, Washington DC)

Manganese fluoroapatite provides a good example of the challenges

presented during the determination of cation distributions in substituted apatite. The present sample has manganese ions substituted

for two of the ten cations which allows both ordered and disordered

arrangements. The apatite structure is such that ordered cation distributions are also possible in space groups P63, P5, P3 and P3. Disordered distributions are also possible in P6 /m, the nominal apatite

space group in addition to the space groups mentioned above. Neutron

Diffraction Powder Profile Analysis is well suited to problems of this

type because a bulk sample which is more reflective of the actiial

10
REACTOR RADIATION DIVISION PROGRAMS

situation is studied rather than one crystal which may provide biased

results.

Powder diffraction data was collected on a well-crystallized

sample. The experimental conditions were as follows:

monochromatic beam; reflection 220 of a Cu crystal,

wavelength 1.5416 (3) A

mosaic spread of Cu monochromator 15 minutes of arc Horizontal divergences

(a) in-pile collimator - 10'

(b) monochromatic beam collimator - 20'

(c) diffracted beam collimator - 10'

Sample container: Vanadium can ^1 cm in diameter

The region from 20 = 5° to 110° was scanned in 0.05° steps.

We decided to first try and determine if the cation distribution

in manganese fluoroapatite is ordered. Modes in space groups P6

and P6 gave refinements in which the manganese ion shifted spuriously

even though the initial positions were chemically reasonable. Refinements in space group P3 were stable and converged to agreement factors

about twice those expected from counting statistics. However, the re- sulting bond distances and angles expecially for the P0, group and about

the manganese ions deviated greatly from literature values. We concluded

that the extra degrees of freedom possible in P3 are not utilized in a manner reflective of the actual structure. Results obtained so far

indicate that:

(a) the cation distribution in our sample of manganese

fluoroapatite is not ordered.

(b) Refinements must be carefully evaluated because for

these structures there is a tendency for false minima.

Future efforts will be directed towards the development of disordered models for the cation distribution.

11
REACTOR RADIATION DIVISION PROGRAMS

POWDER DIFFRACTION STUDY OF Ta 2W08

A. Santoro

and

R. S. Roth

(Ceramics, Glass, and Solid State Science Division)

and

D . Minor

(Information Technology Division)

The compound Ta^WOg has been first considered structurally related

to Nb

2WOg [Stephenson, N.C. (1968). ActaCryst., B24, 637-653.] which

is orthorhomBlc with space group Pbcm. [Lundberg, M. (1972). Acta Chem.

Scan., 26, 2932-2940]. In a subsequent investigation [Holcombe, C. E.

(1976) . Oak Ridge Report Y-2061] it was noted that the x-ray powder

pattern of Ta2W0

fi can be fully indexed on a unit cell similar to that of

LiNb^O^cF, which is orthorhombic with space group Pmma [Lundberg, M. (1965).

Acta Chem. Scan., 19, 2274-2284], and it was concluded that the two com- pounds must be isostructural.

The relationship between the two proposed structural models is illustrated in figure 1. The mirror m, perpendicular to [010] in space

group Pmma, is replaced by the glide b in space group Pbcm. The metal

and oxygen atoms, constrained to lie on the mirror in the first case, are free to move perpendicularly to the plane of projection in the second

case. The change of point symmetry of the atomic positions, in turn, causes the doubling of the unit cell in space group Pbcm. When structures

are as closely related as those shown in figure 1, the indexing of powder

patterns may not be the best way for choosing one model

rather than the other. In fact, angular positions of non-extinct reflections are identical in most cases and the superlattice reflections are

in general very weak and difficult to detect even in those regions of

the pattern free from interferences.

An accurate knowledge of the structure of Ta^WOg is important in

understanding the thermal expansion properties of the compound [Holcombe,

2
REACTOR RADIATION DIVISION PROGRAMS

C.E. and Smith, D.D. (1978). J. Am. Ceramic Soc, 61, 163-169]. For

this reason an attempt was made to solve the structural uncertainty with

the method of profile analysis [Rietveld, H.M. (1969). J. Appl. Cryst.,

2, 65-71].

The single phase composition was prepared by heating the

appropriate mixture of Ta2C>5 and WO3 at 1350°C for 31. 5h and was found

to occur at 52.4 Ta2C>5:47 .6WO3. Assuming the existence of a single phase,

this composition may be interpreted as oxygen deficient (^307. 968' M=Ta, W) or as containing metal excess (M3 > 012^8) • Neutron diffraction measurements

were made with the conditions indicated in table 1. Refinements were

carried out using 262 reflections over the angular range 7.0°<29<84.5°

for Pmma and 298 reflections for Pbcm. In both cases intensities were

measured at 26 intervals of 0.05°. The results for both space groups

are given in table 2, and they clearly show that Ta2W0s is isostructural

with Nb2W08»

c(Pbcm)5q(Pmma)

1,

< 4 <

b(Pbcm) = c(Pmma) Vjf\V4 n*

^

X\/ /\Nj/\/ /i^M/ Awy

"~~7i \PTvL\ V/lVAl ^r>l\ _^T5&

\i-^yj\ \N^7\ \N^/\ vr-AFigure 1. Projections of the structures of Nb2W0s and LiNbg0i5F. The

unit all in space group Pbcm is outlined on the left side of

figure, and the unit cell in Pmma on the right side. The

symbols of the symmetry elements are those used in Int. Tables

for X-Ray Crystallography, Vol. 1.

13
REACTOR RADIATION DIVISION PROGRAMS

The possibility of variable occupancies at the metal sites for

this and for related compounds has been reported (Holcombe, Loc. cit.)

and, in fact, Nb/W ratios different from those corresponding to random

distribution have been found in Nb2W0g (Lundberg, Loc. cit.). In this

study no. 'attempt has been made to refine the Ta/W ratios because tests

on the validity of the Gaussian approximation, made on a sample of AI2O3,

gave a "goodness of fit" X ranging between 1.0 and 1.3, ie. close to the

value of 1.36 obtained for R^/R for Pbcm. This indicates that our re- finements are essentially complete and that it would not be meaningful

to refine more detailed models. For the same reason all calculations

were carried out assuming perfect stoichiometry.

The final atomic parameters for space group Pbcm are given in

table 3 and a comparison of observed and calculated profiles is shown

in figure 2.

i\Ar- f- <yvwMvAjfAx^^^-^x^r^X/ ""W"

1 m,\A-aaj^»yvVv"-Ha^v^-"/1 vv

15 IB 19 20 21 22 23 24 2S 26 28 30 32 34 36 36 40 46 48 SO 56 58 60 62 64 66

Figure 2. Observed (dots) and calculated (continuous line)

profiles. On the lower part of the diagram the curve y(obs) , y(cal) is shown.

In Ta2W0g, 5/6 of the metal cations are octahedrally coordinated

and they are located in three crystallographically independent positions,

two general and one special. The remaining cations are surrounded by seven oxygen atoms in a pentagonal bipyramidal configuration. Octahedra and

pentagonal bipyramid are connected by edge sharing, as indicated in

figure 3, to form the same strucutural unit found in the structures of

Nb2W08, LiNbsOisF, and numerous other compounds (e.g. Stephenson, 1968).

14
REACTOR RADIATION DIVISION PROGRAMS

Table 1. Experimental conditions used to collect the powder intensity

data for Ta2W03.

Monochromatic beam: reflection 220 of a Cu monochromator

(transmission geometry)

o Mean neutron wavelength: 1.5416(3) A

Horizontal divergences -

(i) In-pile collimator: 10 min. arc;

(ii) Monochromatic beam collimator: 20 min. arc;

(iii) Diffracted beam collimator: 10 min. arc.

Monochromator mosaic spread: ^15 min. arc

Sample container: Vanadium can of ^1 cm diameter

0(5 0(5')

0(6")

0(6')

0(6'")

0(5") 0(5'")

Figure 3. Basic unit in the structure of Ta2W0o. A mirror perpendicular

to the plane of figure passes through the atoms 0(1), M(l)-

0(A), M(4) and 0(10)

15
a

REACTOR RADIATION DIVISION PROGRAMS

CO o

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16
REACTOR RADIATION DIVISION PROGRAMS

+

d CU s—s c0 rd

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-d * d -X cu •H ^—

/

rH >. U Nw» c17
REACTOR RADIATION DIVISION PROGRAMS

Table 3. Atomic parameters for Ta2W0g in space group Pbcm

Atom

M(1><*0

M(2

M(3

M(4

0(1

0(2

0(3

0(4

0(5

0(6

0(7

0(8

0(9

0(10)

(*) Figures in parentheses are standard deviations in the last decimal

figure.

(**) M indicates 0.687 Ta + 0.313W.

X

0.016(5) ( ** }

Y

0.3426(5)

Z1/4

0.019(4) 0.1982(3) 0.1296(4)

0.980(3) 0.4061(4) 0.0612(4)

0.083(3) 0.0277(5) 1/4

0.006(7) 0.2288(4) 1/4

0.997(3) 0.3108(3) 0.1307(4)

0.995(4) 0.4402(3) 0.1767(4)

0.491(6) 0.3456(5) 1/4

0.971(3) 0.0972(4) 0.1668(3)

0.988(5) 0.1668(3) 0.0224(4)

0.484(3) 0.2008(3) 0.1317(4)

0.519(4) 0.4077(4) 0.0629(5)

0.530(5) 0.0229(5) 1/4

18
REACTOR RADIATION DIVISION PROGRAMS

Table 4. Interatomic distances in the structure of Ta2W0s» Numbers in

parentheses are standard deviations in the last decimal figure,

The labeling of the atoms is the one shown in figure 4.

M(l) - M(2) 3.254(9) 0(1) - 0(2) 2.467(8)

M(l) - M(3) 3.351(8) 0(2) - 0(3) 2.420(8)

M(l) - H(4) 3.30 (1) 0(3) - 0(3') 2.45 (1)

M(2) - 0(7) 1.81 (2) M(3) - 0(9) 1.79 (2)

M(2) - 0(7)* 2.07 (2) M(3) - 0(9) (*) 2.09 (2)

M(2) - 0(1) 2.083(7) M(3) - 0(2) 2.050(9)

M(2) - 0(2) 1.998(8) M(3) - 0(3) 2.024(9)

M(2) - 0(5) 1.905(9) M(3) - 0(6") 1.902(9)

M(2) - 0(6) 1.878(9) M(3) - 0(8') 1.955(7)

M(l) - 0(4) 1.84 (3)

M(l) - 0(4) (*) 2.04 (3)

M(l) - 0(1) l 2.02 (1) , M(l) - 0(2) 2.072(7)

M(l) - 0(3) 2.122(9)

M(4) " 0(10) ^ 1.74 (2)

M(4) - 0(10) (*) 2.14 (2)

M(4) - 0(3) 1.998(9)

M(4) - 0(5") 1.908(9)

(*) Oxygen atom belonging to the structural unit below the plane of fig. 4,

19
REACTOR RADIATION DIVISION PROGRAMS

Some relevant interatomic distances are shown in table 4. The pentagonal

bipyramid is quite regular, the 0-0 distances corresponding to the edges

o shared with the octahedra vary from 2.420(8) to 2.46(8)A and the re- maining distances from 2.80(3) to 2.88(3). On the other hand, the M06

octahedra are highly distorted with 0-0 distances between 2.420(8) and

o 3. 129 (8) A. The average M-0 distances of the three octahedrally coordinated cations are 1.957(5), 1.969(6) and 1.950(5)1, while that for the

o seven-coordinated cation is 2.041(7)A. These values agree closely with

those found for Nb 2W0s (Lundberg, 1972).

The symmetry of the structural units and the mechanism by which they are connected to form the structure are in general different from compound

to compound. In Ta2W0 8 and Nb2W0s they are pinked by corner sharing and

form layers as the one shown in figure 1. In the third direction the

layers are stacked on top of one another, and each polyhedron shares a vertex with the corresponding one of the next layer. The array of corner sharing octahedra creates large tunnels extending in the direction of the

a(Pbcm) axis and surrounded by three or four octahedra rings. Probably

these are the locations in which the lithium ions are located in the

strucutures of LiNb 6

0-|[-F and of the high-temperature form of LiTa30s.

CRYSTALLOGRAPHY OF RIBONUCLEASE-A

A. Wlodawer

Several sets of neutron diffraction data have been collected on a large deuterated crystal of ribonuclease-A (space group P2^, a. = 30.18A,

b = 38.4, c = 53.32, g = 105.85*, crystal volume 30 mm3 ). Data were

collected using the flat-cone dif fractometer in equational geometry and

counting each reflection for 10 min. The agreement between these data

sets was good (R = 4.8%, defined as R = Z iFj-Fg/ZF) . Incomplete data to

O 2.1 A resolution were collected in the flat-cone mode. An example of the

output for several frames is shown in figure 1. The quality of the data

20
REACTOR RADIATION DIVISION PROGRAMS

o o

«* CM

(0 CO

|auuei|3 J8d sjunoQ |3uueL|0 J3d siunoQ lauueqQ ja<j sjunoQ

Xl

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O

O c CO o 4-1 CU •H PI U U CU

CU CO e

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XI rd

4-1 CU

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XI X) 4-1 H c

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09 •H

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lfl_ en CU

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td • CJ CU

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4-> o r4

CJ 4-1 3

2z CO CJ TJ

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c <4-t M-l o c •H 14-1 m (0 X) •H • O CU T> o

£1 CU CO u (3 CO O &

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4-1 cu

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cu o

q C & < o 4-> O

21

cur460

•H
REACTOR RADIATION DIVISION PROGRAMS

was adversely affected by a faulty ADC circuit (since replaced) and the

agreement with the lower resolution data was fair (R = 9.0%).

X-ray diffraction data on identically treated ribonuclease crystals

e were also collected to 2.5 A resolution. The comparison with the data

collected on similar crystals by Carlisle et al. suggested that there

are some small differences in the conformation of protein molecules, due

to different solvent and deuteration (manifested by high R factor of

11.2%).

We are planning to run several cycles of refinement of x-ray structure of Carlisle et al. using structure amplitudes collected by us to

obtain the best starting model for neutron refinement. This will be

o o followed by refinement of the 2.8 A neutron data and later 2.1 A data,

when the latter set has been recollected.

1. E. Prince, A. Wlodawer and A. Santoro, J. Appl. Cryst. 11, 167 (1978)

2. C. H. Carlisle, R. A. Palmer, S. K. Mazumdar, B. A. Gorinsky and

D. G. R. Yeates Jm Uo i % Bi i, 1 (1974).

ROTATIONAL DYNAMICS AND PHASE TRANSITIONS IN (KCN) x (KBr)l-x

J. M. Rowe and J. J. Rush

and

S. Susman and D. Hinks

(Argonne National Laboratory, Argonne, IL)

Work is continuing on this interesting set of mixed crystals.

Since last year, further measurements on the (KCN)q.25 ( KBr)o.75

crystals have led us to the explanation of the results reported last

year - namely that the energy of the [100] TA modes initially decrease

with decreasing temperatures, then increase for even lower temperatures,

The new results are shown in figure 1. As can be seen in the figure,

the energy of the modes decreases, then increases as T is reduced from

22
REACTOR RADIATION DIVISION PROGRAMS

300

200

100

KBr076 KCN

1 1

. Q = (1.9.2.0)

L

T = 290K

**•————————'

300

| 200

3O 100

300

200

100

T=100K D d

R: a**

m

T 10- o

o T=12K

o^o

°oCbcP o

o°°o

ocP

oocr ° o

°

^

oo

-1.0 -0.5 0.5 Energy (meV)

1.0

Figure 1. Neutron scattering line shapes in (KCN)q 25(KBr)« yc for

transverse acoustic phonons propagating along a [iOO] axis.

Note the existence of an experimental contaminant near

energy transfers of + 0.8 meV (contaminated points are omitted)

There is no contamination for negative energy transfers (neutron energy gain) . The data are uncorrected for resolution

effects. The size of the resolution is shown by the horizontal bars.

300K to 100K to 12K. At the same time, the scattering at ho)=0 (elastic

scattering) increases anomalously over the same temperature range as the

phonon energy increases again.

It is this behavior which provides the clue to the origin of the

effect. As has been pointed out previously, there is a strong coupling

in alkali cyanide crystals between the acoustic phonons (particularly

[100] TA) and the reorientation of the cyanide ions. A central parameter in the theory of these systems (as derived by Michel and Naudts

in collaboration with the present authors) is the ratio of the re- orientation rate (1/A) to the bare (unperturbed) phonon frequency 0)o . For w »l/X, one expects the central peak critical scattering behavior

shown by ND^Dr while for tou »l/A, one expects the soft mode behavior

shown by KCN . However, 1/A is related both to collective behavior and

to single particle behavior. If the temperature is reduced, 1/A decreases

23
REACTOR RADIATION DIVISION PROGRAMS

(in one approximation, exponentially as l/Aae~^K) . Thus, if the temperature can be lowered far enough, 1/X will always be much less than

0)o . In KCN, one cannot reach this regime because of the phase transition at 168K. However, in (KCN) #2 5 (KBr) ^75 there is no phase transition and we can observe both regimes in the same system. Thus, these

mixed crystals offer an almost perfect model system for studying the

temperature behavior of coupled phonon - reorientation systems.

The experimental configuration used for these experiments is

of some interest since high energy resolution and moderately

high momentum transfer are required. We met these requirements by

using 20-20-20-20 collimation and [004] pyrographite for both monochromator and analyses, at a 20 of 90° for a total resolution of 0.2

meV for elastic scattering, with better intensity than could be

obtained for 10-10-10-10 collimation which would have had worse

resolution.

We are continuing this work and have a 50% crystal on which

measurements are just beginning. We have also studied a sample

of 0.4% KCN in KBr and are presently analysing the data. In general,

the data are similar to the results of Nicklow at Oak Ridge on KCN

in KC1.

CN" IONS IN KC1, KBr

R. C. Casella

Motivated by neutron scattering experiments currently being carried

out at the NBS Reactor by J. J. Rush and J. M. Rowe, I have begun a theoretical, analysis of the dilute CN~ substitutional impurities in KC1 and

KBr. One aspect of the analysis has to do with infrared experiments done

elsewhere with a view towards helping to sort out the possible CN" low

temperature equilibrium orientations, e.g. <111> vs. <100>. I assume that

the internal stretch modes are excited by the infrared and that under

24
REACTOR RADIATION DIVISION PROGRAMS

Table 1. Values for the intensity ratio R under various experimental

conditions (see text).

Strain Polarization

E

Model CN~ dipole alignments Experiment3- <100> <110> <111>

[100] e| I s

e_|_ s 3/2 3/2

[1113 £|jS

e_[_ s 3/2

1/3 0.33

4/3 1.15 c

[110], e||s

el s, c| | [110]

e]_ s, ej | [001]

0.1

aData from Reference 1. Maximum applied stress equals 600 dynes/cm'

unless otherwise noted.

maximum stress = 200 dynes/cm , cmaximum stress = 100 dynes/cm ,

compressive applied stress the CN dipoles tend to occupy those positions

in the original equilibrium set which lie most nearly perpindicular to

the applied- stress axis. Under various conditions of applied stress and

for various polarizations £ of the infrared excitation, values of the

saturation ratio R of absorbed intensities are calculated for models in

which the equlibrium CN~ orientations are assumed to lie along the <100>,

<110>, and <111> axes, respectively:

25
REACTOR RADIATION DIVISION PROGRAMS

(intensity of infrared absorbtion under saturation stress)

• R = (intensity of infrared absorbtion under no applied stress)

i The calculated values of R are presented in Table 1 along with data.

These values are obtained ignoring the small ( ^1 cm" 1

) tunnel splittings,

in effect summing over the intensities of the submultiplets . Whereas the

results in table 1 indicate that the <111> orientations are favored, there

is controversy among the infrared experiments as indicated in reference

1, whence the issue is not settled. It is hoped that the neutron scattering experiments, which presumably give a measure of the interaction of

the phonon modes with the local libronic and/or tunneling motions of the

CN ions, will shed further light on this matter. In this connection,

we expect that detailed tight-binding symmetry-projected tunneling states

for the most probable <111> and <100> orientations will be of use, both

for the librational ground states of the CN~ ions and also for states in

which, in addition to the tunneling motion, the ions undergo rapid librational-lika .oscillations in each potential well with a frequency much

greater than the tunneling frequency.

1. F. Luty, Phys. Rev.B10_, 3677 (1974).

NEUTRINO SCATTERING AND WEAK- INTERACT I ON GAUGE THEORIES

R. C. Casella

The idea that scaling violations not accounted for in the original

parton model of Feynman would allow an interpretation of diverse data on neutrino scattering without the necessity of introducing right-handed

(V + A) charged-current Fermi couplings, appears to be experimentally

correct, although the amount of scale breaking required is not yet settled.

26
REACTOR RADIATION DIVISION PROGRAMS

This understanding includes the neutrino and antineutrino induced (oppositely signed) dileptons, the latter in association with charm production

off the strange component of the parton sea. Moreover, the SU(2) x U(l)

gauge theory of Weinberg and Salam (WS) is in accord with the neutralcurrent neutrino scattering data, again without the necessity of introducing appreciable coupling to the heavy quark associated with Lhe upal2

silon resonance. There remains the (experimentally controversial) absence of parity violation by the neutral currents in atomic bismuth,'

which runs counter to the predictions of WS . I have examined a popular

version of the generalized SU(2) x SU(2) x U(l) gauge theories which

have been proposed to explain this possible discrepancy. It is con- cluded that in the Higgs sector the relation Trace < pT><p> - Trace

< (f) > < (J? > , which is required (in the model examined) to reproduce the

sucessful WS predictions for neutral-current neutrino scattering, does

not have a natural basis. This conclusion seems to hold even when (ignoring possible renomalization difficulties) the Higgs scalars p and (j) are treated as different composites of common fermion fields. Very recent

polarized electon-deuteron scattering experiments at Stanford-^ tend to

confirm the original WS theory, which was employed in the analysis of the

neutrino scattering data in reference 1.

1. R. C. Casella II Nuovo Cimento hlk, 377 (1977).

2. For nearly two years, two independent atomic physics groups, one at

Oxford University and the other at the University of Washington at

Seattle, have reported no parity violation at a level well below that

predicted by the WS theory. Recently L. M. Barkov and M. S. Zolotorev

[Zh. Esep. Teor. Fig. Pis 'ma Red 2_6» 379 (1978)] report otherwise.

3. Sinclair (private communication).

27
REACTOR RADIATION DIVISION PROGRAMS

ISOTOPIC SHIFTS OF PHONONS

R. C. Casella

To our prior work in which the molecular product rule for isotopically

substituted systems was shown to hold at arbitrary wave vector q.in a periodic crystal, we have added new inequalities relating the sums of

squares of the eigenfrequencies w and u) associated with isotopic masses

M and M, respectively. We find for a crystal of point ions

x

2 I

u) 2 (qrY ) < I w

2

(q-rY ) < £ o^ry),

Y Y Y (1)

where r denotes the irreducible representation of the little group at q,

y enumerates different modes belonging to the sam- mass ratio of the substituted isotopes. That is,y enumerates different modes belonging to the same (r,q), and x is the

x = (M/M)^,

(2)

where M signifies the heavier mass (x < 1) . For a crystal of extended

molecules, treated as rigid, we find

x I

o) 2 (qry)

Y

< I ^(W) < I

U) 2 (q~ry),

y I

03 2 (qry) Y Y

(3)

Y

2 where y is the ratio of the moments of inertia of the substituted species

(assumed isotropic)

mln

y

= (1/1)1/2 < 1. (4)

The analysis was applied to the Raman spe

28

ctrum of ammonium perchlorate
REACTOR RADIATION DIVISION PROGRAMS

where the shifts under deuteration have been studied (at q = 0) by H.

Prask and G. Rosasco at NBS. The analysis containing the product rule,

the inequalities, and their application to the perchlorates was submitted

for publication. Application to NH/C1- ND4 CI at general q is anticipated.

1. R. C. Casella, NBS Technical Note No. 969', (ed., F. J. Shorten, 1978).

2. R. C. Casella, Phys. Rev. B 17, 3381 (1978).

NEUTRON RADIOGRAPHY

D. A. Garrett

1. Internal NBS Activities

a. Facilities Development

A large effort has been devoted to the construction of the thermal

column neutron radiography facility. The system has been completed with

the exception of the He-filled drift tube. The significant factors this

system has contributed to the NBSNR are (a) neutron radiography may be

conducted without affecting the background which could affect neighboring

experiments, (b) the focal-plane shutter makes it possible to make ex- posures ranging in time from infinity to 0.1 sec, and (c) the entire

system is mounted on tracks, facilitating removal to provide space for

other thermal column experiments

b. Fracture and Deformation Division

Hydrided and unhydrided standard steel samples and specimens from

ruptured petrochemical pressure vessels have been submitted to this group

for neutron radiography in an attempt to visualize the hydride areas of

the pressure vessels. Conventional neutron radiographic techniques have

yielded negative results due to the high scattering cross section of

Fe. This will possibly result in an ongoing program in the FY-79 . Plans

29
REACTOR RADIATION DIVISION PROGRAMS

are presently being made to collaborate with G. Tuckey at the Atomic

Weapons Research Establishment at Aldermustern, England to employ cold

neutrons from that radiographic facility to attempt to visualize the hydride layers

c. Building Technology

A collaborative effort is in progress with personnel of Building

Technology to design experiments to assess the performance of neutron

backscatter gages for the determination of water buildup in flat-topped

building roofs. The role played by our staff is strictly advisory and

will probably terminated once that Building Technology personnel have

been trained in the use of the instrumentation and correct assessment of

the data.

d. Composite Materials

This group has been asked to participate in the NBS composite

materials program both in graphite resin and metal composite technology.

Although no work has been conducted internally in these areas, evidence

exists that neutron interrogation could play an important role in the

destructive and nondestructive evaluation of these materials. Such

problems exist as the breaking of reinforcing graphite or boron fibers in

the materials under investigation, water migration through composite materials and lack of bond. Should positive results be obtained, it appears

that this will be an ongoing problem. On a recent tour of the NBS Research

Reactor, members of the Aerospace Industries Association indicated that

the problems were many and felt that neutron NDE would be a useful methol-

°gy2. Outside Agency Activities

a. NASA Goddard Space Flight Center - Graphite-Boron Composite Materials,

Samples of graphite-boron reinforced composite materials were

submitted to this group for neutron radiographic interrogation. The

graphite thickness was approximately .062 in. The filaments were not

discernable to the human eye, however the spacing could be detected with

microdensitometer scans of the thermal neutron radiographs. This was a

30
REACTOR RADIATION DIVISION PROGRAMS

one-shot experiment and will not be an ongoing program.

b. NASA Goddard Space Flight Center - Graphite-Resin Composite Materials.

Samples of graphite-resin composite materials were submitted to

this group for neutron radiographic interrogation, to determine if resin

richness or poorness could be detected. The samples were approximately

0.25 inches thick. The differences in the two samples could be discerned

both radiographically and ins t rumen tally with microdensitometry scanning

of the radiograph. The possibility exists that this will be an on-going

program on a OA contract basis.

c. NRC - Measurements for Nuclear Safeguards.

The design and purchase of the electronics and scanning system for

the resonance neutron radiography system has been completed. Design of

the collimator and experimental cavity is in progress. Dr. Yu Tavang

Cheng has been selected to fill the Nuclear Safeguards slot in the

Reactor Radiation Division. Dr. Cheng obtained his Ph.D. in nuclear

physics from the University of Oregon and possesses extensive experience

in Fortran computer programming. He presently holds a Postdoctoral

Fellowship at Johns Hopkins University and is working with Madam Dr. Wu's

group at Columbia. His obligation to Johns Hopkins ended at the middle

of September. We expect to hire Dr. Cheng as soon as possible contingent

on his being granted U.S. Citizenship.

The Los Alamos simulation contract has been issued. The Albuquerque

DOE fiscal officer has required that some changes be made. For instance,

the DOE would prefer to bill our program on a monthly manpower usage basis.

This should present no problem to the NBS . A detailed communication outlining the procedure to be followed has been received.

Personnel from the Neutron Field Standards Group are cooperating

in this project by supplying fission detectors for the final system.

All indications are that this activity will be an on-; >ing program at approximately $70,000 per year plus inflation

received 10 percent of the general equipment budget for FY-1979.

31
REACTOR RADIATION DIVISION PROGRAMS

d. FDA Cardiac Pacemaker Battery Studies.

This group has received a $15,000 contract to study the physical

behavior of lithium iodine pacemaker battery dielectric behavior as a function of battery depletion over a 1.5 year period. The pacemaker

batteries will be neutron radiographed at 3 month intervals over the

projected lifetime of the batteries.

Three dimensional laminagraphy of one set of batteries at various

stages of depletion has confirmed that void formation does occur in the

electrolyte. Whether this is caused by pressurized gas at this point

is purely conjecture until destructive analysis can be made. It is well

established that Li-SOo power systems violently explode once void formation in the electrolyte begins. Chemists, however, at the manufacturer

of the cells presently under examination state that there is no known

mechanism by which void formation can take place in the solid delectric

used in pacemaker batteries.

e. NAVAIR Screen Devlopment

Work on the NAVAIR screen development project has lagged primarily

due to the fact that much of the information is proprietary and that

delivery of components is slow. Preliminary experiments with uv curing

adhesives as a binder indicate that this procedure may be promising - however insuf f iecient data is available at this time to make a definite statement. This could be an ongoing project.

fNational Art Gallery - Smithsonian Institution

A proposal has been submitted by the Conservation Analytical Laboratory of the Smithsonian Institution to the National Art Gallery for

the NBS to participate in neutron-induced autoradiography program for

authentication and attribution of Old Masters and Early American Primitive

paintings. The initial contract to the NBS would be $22,000 for a twomonth feasibility study. At the same time, a proposal is being submitted to other funding agencies for an on-going program.

32
g. Royal Military College of Canada

A transportable field neutron radiography system designed by the

author is presently operational in Canada. The design of the system was unique in the Cf-251 source is exposed to the object under inspection,

resulting in gamma fogging of the film in the direct exposure mode. The

rationale for this design was that the gamma fogging can be subtracted

from the composite radiograph, resulting in the production of a pure

thermal neutron radiograph. Cooperative experiments are in progress to

determine whether or not this can be attained in the darkroom.

3. Addendum: Symposium on Real-Time Radiologic Imaging: Medical and

Industrial Applications

The author co-chaired this symposium May 8-10, 1978 with Mr.

Donald Bracher of the Old Delft Corporation. In our activities in radiologic imaging, it was obvious that scientists in the medical and

industrial sectors were making real strides in the development of this

technology, however they were not sharing information. It was the

purpose of this symposium to bring these two communities together on a common ground in which an exchange of ideas would result.

There were a total of thirty-one papers, twenty-five of which were by

invited authors who were world experts in some facet of the technology.

There were a total of 230 attendees at the symposium. Eighty-three

percent of the authors submitted manuscripts which will be published as

a special ASTM publication in approximately nine months.

33
B. RRD Collaborative Programs

APPLICATION OF NEUTRON DIFFRACTION TO

NON-DESTRUCTIVE TESTING PROBLEMS

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

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

and

(National Bureau of Standards, Washington, DC)

and

H. A. Alperin

(Naval Surface Weapons Center, White Oak, MD)

and

(National Bureau of Standards, Washington, DC)

and

C. Bechtold

(Metal Science and Standards Division)

The Army group at the NBSR has been engaged in a continuing program

to determine "texture 1

" (i.e., grain orientation) as a function of depth,

nondestructively , in the copper liner component in shaped-charge munitions. Because the liner of interest is only 0.28 cm thick, a "difference' 7 technique has been developed which utilizes the fact that for a given crystallographic plane, and appropriate masking, different volumes

(depths) are sampled when different neutron wavelengths are employed.

Alternatively, the same effect is achieved at a fixed wavelength by

examining different order reflections for a given plane. »Z Initial results have now been obtained for a shaped-charge liner,

divided into "top" (0.5mm thick) and "bottom" (below 0.5mm depth) layers.

Pole density distributions are shown in figures 1(a) and 1(b) for (100)

and (111) planes, rspectively. Although preliminary in nature, the re- sults are in qualitative agreement with (destructive) x-ray texture

studies for similarly fabricated liners.

The difference technique has also been applied to the determination

34
(a)

RRD COLLABORATIVE PROGRAMS

(200) Bulk (400) Bulk

(100) Top Layer (100) Bottom Layer

Figure 1. Pole density distribution for an M456 shaped-charge liner.

Following conventional notation, a = 90° - which corresponds

to the normal direction to the cone surface-is at the center

of each figure; <$> = 0° is at the top and corresponds to the

apex direction of the copper cone. The periphery of the

figures correspond to a = 30°. "Top" and "bottom" layer

distributions are obtained by taking appropriately weighted

differences of the "bulk" distributions 2 for (100) and (111)

planes, respectively. The contour lines correspond to steps

of one 'random" with the outermost contour line equivalent to

"random"

35
RRD COLLABORATIVE PROGRAMS

(b) (111) Bulk (222) Bulk

Hi'.'. #

(111) Top Layer (111) Bottom Layer

lilHIi.

iiiiiirj iiiti

•%$m

Figure 1. "Continued",

of texture as a function of depth in an aluminum cylinder fabricated for use as an ultrasonic standard reference block. In this case, the "top"

layer corresponds to a 0.1 cm thick surface layer, and the "bottom"

layer extends from CL 1 cm to a maximum depth of 0.5 cm. Pole figures,

shown in figure 2, indicate little change in texture as a function of

depth. However, considerable anisotropy is observed in the ring of the

secondary maximum (a^65°). The fact that the block was rejected as an

36
RRD COLLABORATIVE PROGRAMS

Al (200) Bulk Al (400) Bulk

•..:!.;:,.;!*!>::!:;:::.•.;;.;*«.;:

Al (100) Top Layer

' .* '"

*'J"2 T *r . " *•"*'*•*»•*•*'• ••II' *

"•'

:

: k;«K

, ' : ^.;'.;Ji

,v

; l&:

Al (100) Bottom Layer

.ni

.

r,$?£ H;;;K •

i, . s^ •

' :' :V~ .-? : f

Figure 2. Pole density distribution for the flat surface of a cylindrical

aluminum standard reference block. "Top" layer corresponds to

a depth of < 0.1 cm; "bottom" layer to the region ^0.1 cm to

MD.5 cm for 35°<_a<90°.

ultrasonic standard may be correlated with this texture anisotropy.

In the area of residual stress determination, our program is aimed

toward the nondestructive determination of residual stress gradients within the bulk of metallurgical samples. However, work to date has focused

on demonstrating that precision and reproducibility of the neutron diffraction technique is sufficient for residual stress characterization.

37
RED COLLABORATIVE PROGRAMS

In figure 3 are shown strain vs. stress results for a 1.59 cm diameter

steel rod (AISI 1017) stressed in tension. Data for (310) and (211)

Table 1. Comparison of v/E vs. stress for a carbon steel.

Crystal

Plane

(310)

(211)

Bulk

1.35

Neutron

Diffraction

1.56 + 0.02

1.19 + 0.02

Theoretical^-)

1.69

1.25

A) E. Kroner, Z. Physik 151, 504 (1958); F. Bollenrath et al.,

Z. Mettallkde. 58, 76 (1967).

c

'5

KSI 10 20 30 40 50

60

I I

Steel (AISI 1017)

1 1 i

(310)^^

40 - •s^

(211)

20

^^S^^"^ ^y^^*

-^f_ 1 1 l_ I 1 60 120 180 240 300 360

Stress Mn/m 2

Figure 3. Strain vs. stress for a 1.59 cm diameter steel rod in tension,

38
RRD COLLABORATIVE PROGRAMS

planes are shown. In table 1, a comparison of v/E, obtained from the

slope of the strain vs. stress data, is made with theoretical predictions

for a "plain carbon steel." These results confirm that the precision

and reproducibility of the neutron diffraction technique is sufficient

for residual stress characterization.

1. Prask et al. , NBS Tech. Note 969, p. 73 (1978).

2. C. S. Choi, H. J. Prask and S. F. Trevino , J. Appl. Cryst. , to be

published.

HIGH TEMPERATURE STRUCTURE OF NH4NO3 ( PHASE II)

C. S. Choi

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

and

(National Bureau of Standards, Washington, DC)

It is well known that solid ammonium nitrate exists in five different phases. The phase II form is stable at the temperature between 84°C

and 125 C and crystallizes in tetragonal cell with P42..m space group.

A few years ago we had proposed a probable structure for phase II in con- junction with the structure of phase IV. This study was undertaken to

confirm the proposed structure by means of profile refinement of neutron

powder diffraction data. Triple axis spectrometer, equipped with Cu(lll)

monochrometor and graphite (400) analyzer, was used for the measurement

o to reduce the incoherent background from hydrogen atoms. Using 1.5357 A

neutrons, diffraction intensities were measured from 10° to 120° with 0.1

step. The postion of the data contaminated by aluminum peaks from the

sample container was removed from the refinement. The structure was re- fined by using a modified version of Riethveld's profile refinement program, with anisotropic thermal parameters for oxygen atoms and ammonium

nitrogen. The final R- indices were rather high, R-j = 9.89 R2=19.54 Ro=17.35

39
RRD COLLABORATIVE PROGRAMS

for expected R=9.47, which may be attributable to the poor counting

statistics of the data due to the intense background and also to the an- harmonic thermal motions of both ions. The refined cell parameters are

o a=5. 695(1) and c=4.912(l)A. The structure is made of two dimensional hydrogen bond chain network running between 0(1) atom and four hydrogens of

an ammonium group, which is the same network observed in phase IV structure

o except slight increase in the bond length (2.05 and 2.16A in phase IV to

o 2.33A in phase II). The final structure parameters are given in table 1.

Figure 1 shows the thermal ellipsoids of nitrate group atoms, which indicate clearly an intense librational motion about the central nitrogen

within the molecular plane. If this libration is a hindered rotationtype motion, the molecule must possess three equivalent 0-N bonds (or

trigonal symmetry). The observed N-0 bond lengths were 1.12(2)A for the

o two N-0(2) bonds with resonating double bond character, and 1.47(2)A for

the N-0(1) bond (single bond) which is also consistent with the hydrogen

iXa

o'0

if &

X:

*

O ^

£

Y.

Figure 1. Structure of ammonium nitrate viewed along the c-axis direction

and a nitrate anion viewed along the plane normal direction.

The thermal ellipsoids are scaled to include 20% probability.

40
RRD COLLABORATIVE PROGRAMS

bonds formation of the 0(1)" atom. Hence this study is inconsistent with

the hindered rotor model of NO3 ion in phase II strucuture.

Table 1. Positional and thermal parameters in NH^NO-, phase II at 100 C,

(* indicates isotropic temperature factor B)

Atom X Y Z Bll (_B22 ) B

33 B 12

NH 0. 0. 0. 2.9(3) 11.4(8) 0.

H -.018(8) -.112(3) .139(3) 12.(1)*

NO 0. .5 .497(2) .5(1)*

0(1) 0. .5 .198(3) 11.(1) 1.(1) -1.(1)

0(2) .106(2) .606(2) .644(4) 8.(1) 20.(2) 6.(1)

B13 (-B23 ) 0.

-10.(1)

REFINEMENT OF D I PARA-ANTHRACENE STRUCTURE

C. S. Choi

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

and

(National Bureau of Standards, Washington, DC)

This study was intended to supplement the earlier work by Ehrenburg

(1969) which is based on two sets of VJeissenburg data and hence is less

accurate. A total of 1609 independent reflection data were collected

within the sphere of sin9/X less than 0.65A , using Ka-Ka radiation.

Using combination of direct method and Fourier synthesis, a complete

structure including hydrogen atoms was solved. Subsequent least squares

refinement reduced the R- indices to R=0.045 and R =0.05 for 1019 observable w

intensity reflections. The unit cell obtained were a=12.085(4).

b=18.853(7) and c=8.139(3) in Pbca space group. The final least squares

parameters are given in table 1. The bond lengths are given in figure 1.

The benzene ring in either end of anthracene molecule is very close to

o regular hexagon with the bond length of 1.39±1A and bond angle of 120±1 .

41
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42
RRD COLLABORATIVE PROGRAMS

Figure 1. GRTGP drawing of dipara-anthracene molecule. Carbon atoms are labeled with underlined number, and hydrogen atoms are drawn

with small circle.

Each anthracene molecule is bent at the middle by 44°, and coupled to

o other anthracene molecule through the long c-c bonds (1.628A) extended

from the apex atoms. There are no evidence of hydrogen bonding in this

crystal.

THE PRESSURE- INDUCED PHASE TRANSITION IN SODIUM NITRATE

S. F. Trevino

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

and

(National Bureau of Standards, Washington, DC)

and

E. M. Brody

(University of Rochester, Rochester, NY)

43
RRD COLLABORATIVE PROGRAMS

Sodium nitrate undergoes a paraelectric to ferroelectric phase

2 transition at 45 kilobars. A soft mode has been observed by Ramon

scattering in the ferroelectric phase. The mode is of A symmetry.

The behavior of the mode, as a function of pressure is well described

using a mean field expression of the form

^ = A(P-Pc) 172

P > Pc

where A = 13 + 1 cm"

1

/ kb 1/2 and Pc = 45 + .5 Kb

The paraelectric form should satisfy the eq.

2tt m CPc P)

In addition, from the known structural changes caused by the phase

transition, the eigenvectors of the mode can be constructed and must

have both translational motion of the Na and NO groups parallel to the

unique axis and rotation of the N0„ group about the unique axis. In

the paraelectric phase, the soft mode must have A~ symmetry. Such a mode has been observed at ambient condition by neutron scattering.

Table 1. The structure in portion of the A~ mode in NaNO , E, in the

rotational part of the eigenvector and E, the translational.

RLP F

006 1.708 5 T

022 -.16 5 T + .554 ^

In the present work, the polarization vector and pressure dependence of this mode are investigated to corroborate the validity of

the soft mode model.

44
RRD COLLABORATIVE PROGRAMS

500 r

q = (0.0,0)

(0,0,6)

q = (0,0,0)

(0,2,2)

Figure 1. The A2U phonon measured at two different RLP as discussed

in the text.

Figure 2. The pressure dependence of the An,, phonon.

45
RRD COLLABORATIVE PROGRAMS

Table 1 shows the structure factor for the two reciprocal lattice

points (RLP) used to measure the eigenvector (g and g are respectively

R 1 the eigenvectors for relation and translation of the mode) and figure 1

the measured phonon at these RLP. From the measurement £ = .202 and

R

F = .979 confirming the translation-rotation nature of the mode. Figure

2 shows the pressure dependence of the mode for two pressures of 1 bar

and 6.69 K bar. The shift is downward by 6%. The model predict a downward shift of 7.7%. The present evidence is taken as confirming the

correctness of the model.

It will be very interesting to study the behavior of the soft

mode to higher pressure but we do not at present have that capability.

1. Barrett, J. D., Pack. J. and Hall, H. T. Tans. American Cryst.

Dissoc. 5 113 (1969)

2. Letturi, T. R., Brody, E. M., Bull. American, Phys. 5 or 22 323

(1978).

THE STRUCTURE OF SODIUM ZINC CHLORIDE TR I HYDRATE

H . Ammon and R . J . Khanna

(University of Maryland, College Park, MD)

and

E. Prince

The positions of the non-hydrogen atoms in the unit cell of sodium

zinc Chloride trihydrate Na2ZnCl4 # 3B.20 eve determined by x-ray diffraction by Brehler . The compound crystallized in space group P31m with

o o all dimensions a=6.876(5)A, c-5«955(5)A, with one formula unit per unit

cell. A set of three dimensional neutron diffraction data was collected

from a crystal of this compound several years ago . These data have now

been refined to an R=0.028, and the hydrogen positions have been determined. The water molecules lie in minor planes with )-H distances

o o (uncorrected for thermal motion) of 0.954A and 0.962A and an H-O-H bond

angle of 104.23°. Both hydrogen atoms participate in 0-H # **^ hydrogen

46
RRD COLLABORATIVE PROGRAMS

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CO S3M OrHcoco^r-crm eu> cmcmcmcmoocmcmco o

CO

CU u

CU1

V4

cOa. to

cu •S

IW

Pi

r-\ CM

rH a

,Q O

CO 4-1 d CO H <3 Nl 2

H CM jo

<-^ r-\ H CM cO

C_3 O O M W H

47

H CM CM rH CM

o? s? o* o< c* rH o a

i O

1 rH CM o1 U

1 d d CO CO i 1 rH CM 1 M Nl K J3 o O ffl a o

* •K * K •K
RRD COLLABORATIVE PROGRAMS

bonds. Table 1 gives refined atomic parameters and table 2 gives selectee

interatomic distances and angles.

1. B. Brehler, Z. fur Krist • , 114 , 66 (1960).

2. R. J. Khanna & E. Prince, NBS Tech. Bote 813, 54 (1974).

SPIN EXCITATIONS IN AMORPHOUS TRANSITION-METAL GLASSES

J . J . Rhyne

and

J . W . Lynn

(University of Maryland, College Park, MD)

and

(National Bureau of Standards, Washington, DC)

and

F. E. Luborsky and J. L. Walter

(G. E. Research and Development Center, Schenectady, NY)

There has been a very strong interest in the magnetic properties of

amorphous transition-metal ribbon materials principally for their very

hi&h permeability and their applicability in transformer design and magnetic

shielding. In the interest of examining some of the alloys magnetic inelastic neutron scattering studies have been performed at the NBS reactor

on ribbon specimens of amorphous Yeg^S^ cSiQ^ and Fe2oNi60B 19-E> l* ^ne samples were prepared from boron enriched to 96% R to reduce the neutron

absorption. The Curie temperatures for the two materials are 613 K and

410 K respectively, and the saturation magnetizations 4ttM are 16.0 kG

and 5.1 kG at room temperature. In the Fe~QNigQBsl9pl specimen, welldefined spin waves were observed at room temperature for neutron wave

vector transfers in the range q = 0.06A- -'- up to q = 0.4 A . After

correcting for instrumental resolution, the data obeyed a quadratic dispersion law with spin stiffness D = 80 meV-Az . This is to be compared

with a D of 100 meV-A^ measured on a specimen of a similar commercial

48
RRD COLLABORATIVE PROGRAMS

amorphous ribbon material of composition Fe4oNi4oPx4^6 which has a Curie

temperature of 537 K 3. A representative energy scan showing both energy

gain and energy loss spin wave peaks is shown in the figure. Spin waves

in the ^^S2^16 5^0.5 amorphous alloy were observed at somewhat higher

energies than in the Fe20Ni60Bi9Pl. as expected due to the difference

in Curie temperatures. The spin wave stiffness parameter for this material is 125 meV-A^

MAGNETIC EXCITATIONS IN HoFe2 J . J . Rhyne

and

N. C. Koon

(Naval Research Laboratory, Washington, DC)

HoFe„ is one of the series of RFe_ (R = a trivalent rare earth

heavier than Nd) compounds which crystallize in the close-packed Lavesphase crystal structure. All have Curie temperatures well above room

temperature (T

c for HoFe

2 is 597 K* and for the heavy rare earths

exhibit a f errimagnetic spin structure in which the rare earth spin

having the free-ion moment is antiparallel to the iron moments of approximately 1.5 Ug . The low iron moment is presumed to result from band

structure effects.

We have made inelastic neutron measurements of the spin excitations

in single crystal HoFe„. The lattice parameter of HoFe_ is 7.30 A at room temperature and the primitive cell contains 6 atoms. One thus

expects six spin wave branches, only three of which are at a sufficiently

low energy to be accessible to thermal neutron scattering. The data were

3 taken on a single crystal of approximately 2 cm on triple axis spectrometers at the NBS reactor. The [100] direction is the easy magnetic

direction for HoFe„.

49
RRD COLLABORATIVE PROGRAMS

10 +>C

3

O

o

COc

CD 450-

300

150

6001

450-

300-

150

Fe 20 Ni 60

B 19 P

1 Amorphous Alloy

Q = 0.08A

-1

-0.80 -0.40 0.00 0.40 0.80

E

Q = 0.12A

•450

300

150

-2.25 -1.50 -0.75 0.00 0.75 1.50 2.25

E (meV)

Figure 1. Scattered neutron intensity (arbitrary units) versus neutron

energy transfer for Fe2oNi5QBi9Pi amorphous ribbon alloy.

Data are shown for wavevector transfer q of 0.08, 0.12 and

O.IAA- -'-, and were taken with an incident energy of 28 meV.

The solid line is the result of fitting a Gaussian lineshape

to the data. The arrows indicate the position of the reso- lution-corrected spin wave energies.

50
RKD COLLABORATIVE PROGRAMS

The lowest three branches for spin waves propagating in the [q,q,o]

direction for HoFe2 are shown in figure 1 at room temperature and 10 K

(2 branches). Measurement in the [q,q,q] direction showed no evidence

for anisotropy in the spin wave spectra. The spectra are qualitatively

similar to those found in previous work on ErFe2 t 3 l and consist of an acoustic mode, a very flat optic mode and a highly dispersive optic

branch.

The high energy mode represents an in-phase precession of the iron

spins only and has a spin stiffness very close to that of iron metal. In

the absence of rare earth ion exchange, which produces the 16.6 meV gap,

this mode would become the acoustic mode excitation. At 78 K calculations

show that the increased rare earth magnetization raises the q = energy

to 34 meV.

The flat branch of the spectrum arises from a molecular field excitation of the rare earth spins by the iron. The absence of measurable

dispersion in this mode is a consequence of negligible rare earth-rare

earth exchange and places an upper limit of approximate +0.01 meV on

the magnitude of this interaction assuming an isotropic model.

The 10 K excitations have been fit to a linear spin wave model with

a Hamiltonian containing both exchange and crystal field contributions

which yielded the following parameters: J = -0.43 meV, J" = 26 meV,

e7__ „ = 0, and A = 0.6 meV. Agreement between theory and experiment for

the acoustic and lower optic mode is within experimental error over the

entire Brillouin zone. The model also fits the high energy iron mode at

2 room temperature using a value of <J > = 4.7, in agreement with elastic

Ho

neutron scattering data [2].

A careful study was made of the temperature dependence of the energy

and intensity of the flat rare earth mode to look for observable crystal

field transitions, figure 2 illustrates the observed scattering at the zone boundary for this mode as a function of temperature. At 10 K only

a single line of width determined by instrumental resolution was found at

an energy of 8.3 meV which represents the ground state to first excited

51
RRD COLLABORATIVE PROGRAMS

state energy. As the temperature is raised this mode increases rapidly

in intensity and shifts to a slightly higher energy (8.6 meV at 295 K)

Concurrently, significant intensity also appears in a very broad maximum

about 6.7 meV indicative of a distribution of unresolved energy states

in the range approximately 5-8 meV.

0.2 0.4 0.6 0.8 1.0 Reduced Wave Vector, q x (x component)

Figure 1. Magnon dispersion in HoFeo at room temperature and at 10 K

for the [q,q,0] propagation direction.

52
RRD COLLABORATIVE PROGRAMS

5 6 7 8 9 10

Energy Transfer (meV)

Figure 2. (a) Observed inelastic intensity for the (2,1,1) point in

reciprocal space as a function of temperature. Note the

increase in scattering near 7 meV as higher states of the

calculated crystal field multiplet (b) become populated.

The value of exchange (gygH excu in' equation 2) used was

7.73 meV and the crystal field parameters were

B4 = -8.1xl0-5 meV, and Be =+4 .4xl0"7 meV.

53
1. E. Burzo, Z. Angew. Phys. 32 127(1971).

2. N. C. Koon and J. J. Rhyne, Solid State Communications 26. 537 (1978)

RRD COLLABORATIVE PROGRAMS

It is noted that the "acoustic" mode excitations observed at 295 K

and shown in figure 1, broaden severely and become essentially unobservable above about 7 meV as they enter the energy region of the crystal field

transitions.

A calculation of the energy levels was made by a direct diagonalization

of a Hamiltonian containing both exchange and fourth and sixth order

crystal field terms and the results are shown in figure 2b. The eigenstates are almost pure J states, so that only transitions between

adjacent states have finite matrix elements.

The calculation provides a qualitative explanation of the observed

scattering intensity. At T = 10 K only the ground state is populated

and a single transition at about 9.2 meV is observed. Since the levels

immediately above the ground state are separated by more than 8.2 meV,

the peak in the scattering intensity initially moves to higher energies

as the temperature is raised. At 200 and 295 K, however, crystal

field levels with lower energy separations become populated and a broad

band of scattering centered at about 6.7 meV is observed.

The model, however, gives a very small matrix element for the ground

state to first excited state transition. Comparison of the relative

intensities in figure 2a shows that this transition is actually quite

weak, considering that at 10 K essentially all of the rare earth spins

are in the ground state, but it is not nearly as weak as the model

predicts. It should be noted that for HoFe

2 the [110] and [100]

directions are almost equally easy at low temperatures and it is possible

that the easy axis of HoFe- is rotated slightly away from [100] at

T = 10 K. Further work is in progress on this problem.

54
RRD COLLABORATIVE PROGRAMS

MAGNETIC NEUTRON SCATTERING FROM AMORPHOUS TmFe2

J. Rhyne

and

S. Pickart

(University of Rhode Island, Kingston, RI)

and

H. Alperin

(Naval Surface Weapons Center, White Oak, MD)

and

(National Bureau of Standards, Washington, DC)

The nature of the spin glass "freezing" or "blocking" transition

has recently attracted much theoretical and experimental interest

One might expect that a microscopic technique such as neutron scattering

should contribute heavily to uncovering such details. Previous neutron

measurements indicate anomalies in the small-angle magnetic scattering

from a series of crystalling AuFe alloys2 and amorphous YFe2

while changes in the frequency dependence of the scattering were reported

for the crystalline CuMn system^. We have made total and inelastic

scattering measurements also on an amorphous composition, TmFe2> that

does not show a conventional ferromagnetic ordered phase at low temperatures. Instead a peak in the susceptibility occurs at about 45 K, suggestive of a spin clustered system with probably antiferromagnetic correlations.

The low angle scattered intensity was measured for scattering

vectors .02<q<.12 A

_1

and found to be of comparable absolute intensity

to that in the previous study of YFe,,. This is to be contrasted with

the scattering observed from TbFe

2 3 and HoFe2

5

, which is orders of

magnitude larger. These latter alloys have much stronger spin correlations and exhibit conventional bulk ferrimagnetic behavior.

There is one (probably minor) difference between the TmFe

2 data and

the previous YFe

2 results 3 . First, no peak is observed in the region

of the transition temperature suggested by bulk magnetic measurements

55
RRD COLLABORATIVE PROGRAMS

(^45 K) , though there is a definite tendency of the scattering curves to

bend over at low temperatures; possibly at lower temperatures or lower q

than attained in the present study a peak might develop . Overall the

main feature of the data (which show a large increase in small angle

scattering with decreasing temperature) is indicative of the development

of regions of short range magnetic order.

In order to detect a possible change in the spin relaxation process

on passing through the spin freezing temperature of approximately 45 K

(as given by bulk magnetization data) we measured the energy dependence

of the scattering at small angles at temperatures of 60 K and 10 K. The

results indicate that no great change in the diffusion constant has

occurred. The measurement is a difficult one to make with the great

precision because of the well-known limitations in energy transfer attainable at small momentum transfers near the forward direction. As a result,

the true background of the scans cannot be fixed unambiguously. However,

our data appear to rule out more than at most a 30% change in energy

width of the scattering from above to below the spin freezing temperature.

The small angle total scattering data described above suggest a similarity in the spin clustering in TmFe

2 and YFe,, but its exact nature

requires much more extensive data to elucidate. The data are not inconsistent with those for the AuFe system2 (taken at much lower q) , where

much sharper peaks were observed.

However, there is a clear difference in the changes in inelasticity

of the scattering above and below the transition in the amorphous TmFe9 and in CuMn 4, in which a striking change in halfwidth occurs (from

0.36 meV above the freezing temperature, to .005 meV below). We must

thus conclude that in the concentration range of these alloys there is an intrinsic difference in the spin diffusion processes occurring in the

crystalline and amorphous matrices.

56
RRD COLLABORATIVE PROGRAMS

1. For collected references, see Levy, R. and Hasegawa, R. , Amorphous

Magnetism II, Plenum Press, New York, 1977

.

2. Murani, A. , "Nonuniqueness of Freezing Temperature of Spins in

Binary Alloys," Phys. Rev. Lett. 37, 450-453, 1976.

3. Pickart, S., Rhyne, J. and Alperin, H. , "Anomalous Small-Angle

Scattering from Amorphous TbFe_ and YFe„," Phys. Rev. Lett. 33 , 424-427, 1974.

4. Murani, A., Goeltz, G. and Ibel, K., "Evidence for Freezing of Spins

in Binary Alloys," Solid State Comm. 19, 733-736, 1976.

5. Pickart, S. , Rhyne, J. and Alperin, H. , "'Critical 1 Neutron Scattering in Amorphous HoFe and GdFe'' AIR Conf. Proa. 2A_, 117-118,

1975.

57
RRD COLLABORATIVE PROGRAMS

MEASUREMENTS OF THE CRYSTAL-FIELD SPLITTINGS

IN SUPERCONDUCTING (Ce1 _x

Ho

x

)Ru 2 ALLOYS

C. J. Glinka & J. W. Lynn

(University of Maryland, College Park, MD)

and

(National Bureau of Standards, Washington, DC)

In the superconductor CeRu~ rather high concentrations of magnetic

heavy rare earth ions may be substituted for the non-magnetic cerium ions

before superconductivity is completely quenched. For example, ^35%, of

the Ce can be replaced by Ho before Ts goes to zero and small amounts of

Ho actually enhance Ts

. Furthermore, for Ho concentration above ^25%,

bulk magnetic susceptibility data show distinct maxima as a function of

temperature which are suggestive of long-range magnetic ordering. Thus

the psuedo-binary alloy (Ce-i_xHo )Ru« is an ideal system for studying the

competition between the two cooperative phenomena of superconductivity

and magnetism. To this end, neutron scattering is an ideal technique

for studying the magnetic properties since the magnetic state may be

microscopically probed without being affected by the screening of the

superconducting electrons.

In (Ce-i__.Ho )Ru„, a fundamental characterization of the system is

J- A x Z a measurement of the splitting of the J=8 manifold of the Ho J ion by

the cubic electrostatic field of the crystal. In an initial study of

the inelastic scattering from a sample of (Ce 73H0 27)^2 > the observed

transitions implied that a triply degenerate r, 5 state lies lowest, so that the ground state is magnetic. Recently we have carried out similar

measurements on samples with the compositions (Ce qHo -i)Ru 9 and (Ce^gHo „..)Ru2 in order to study the concentration dependence of the crystalfield splitting. The samples were prepared by arc melting measured

amounts of the pure elements and then annealing at 1350°C for 24 hours.

Neutron diffraction and metallographic analysis revealed only trace

amounts of secondary phases in the resulting materials, whose compositions

were determined by emission spectroscopy.

58
RRD COLLABORATIVE PROGRAMS

Crystal field transitions observed in (Ce QnHo , n )Ru at 10K are

. yu • _LU 2. shown in figure 1. The transition energies of 3.75 and 15 meV are nearly

(Ce09 Ho0| )Ru2

T = IOK

I~kI =1.60 a"

1

iA'w

5.0 10.0

E (meV)

15.0 20.0

Figure 1. Constant - K scan of the low energy inelastic magnetic scattering from (Ce >9 QHo >10 )Ru2 at 10K showing two crystal field

transitions from the fa round state at 3.75 and 15.0 nieV.

the same as had been observed in (Ce 70H0 ~ 7 )Ru2 and correspond to the

two possible transitions out of the ! T5 ^ •'ground state. With increasing

temperature two additional, excited state transitions become observable

at 8.5 and 12.0 meV. These may be seen in figure 2 which shows data

taken at 50K. The combination of transitions seen in figures 1 and 2 uniquely identifies the crystal field level scheme of the Ho-* ion,

confirming that the magnetic Ts^ 1 ^ level is the ground state. Similar

results were obtained on the high concentration sample, (Ce /-qHo ^^Ruo.

o_i_ We conclude, therefore, that the Ho ion has a magnetic ground state

over the entire concentration range of interest.

59
RRD COLLABORATIVE PROGRAMS

O 100

in

-t- c

O

o

( Ce

0.9

H

°0..) Ru

2

T = 50K

K I =1.60 A"

1

12.0

E (meV)

18.0

Figure 2

.

Inelastic magnetic scattering from (Ce^gQHo^ 10)Ru2 at 50K

showing, in addition to the ground state crystal field

transition at 15 meV, two excited state transitions at 8.5

and 12.0 meV.

Small'-angle scattering measurements are now in progress to study

the development of magnetic correlations as a function of the holmium

concentration in these alloys. In data taken on the 27% Ho sample^, these

correlations were found to be described by an Ornstein-Zernike correlation

function, with the correlation range increasing steadily with decreasing

o temperature down to 0.5K, but then saturating at a value of 80' k . In

contrast to the crystal field measurements, changes in the holmium con- centration should have a marked effect on this behavior.

1. J. W. Lynn D. E. Moncton, W. Thomlinson and L. Passell,

Bull Am Phys Soa. 22, 339 (1976).

60
RRD COLLABORATIVE PROGRAMS

LOW TEMPERATURE PHASE TRANSITION IN Cs 2NaPrCl6

G. E. Fish

and

J . W . Lynn

(University of Maryland, College Park, MD)

and

(National Bureau of Standards, Washington, DC)

and

H. H. Patterson

(University of Maine, Orono, ME)

and

J . J . Rhyne

The compounds Cs2NaMCl£ are known to have the face centered cubic

structure at room temperature for a wide variety of trivalent ions M,

including transition metals, actinides, and rare earths. This class of

compounds provides a rather unique model system for study of the rare

earths in either concentrated salts or with paramagnetic ions diluted in

the diamagnetic La, Lu, or Y hosts, because all the trivalent ion sites

are equivalent and have octahedral (Oh) symmetry1

. For the heavy rare

earths, the compounds remain cubic down to 1.5 K or have at most a slight

non-cubic distortion . However, previous EPR and optical studies have

shown that the light rare earth compounds undergo a phase transition below room temperature, but no details of the structure have been reported .

We have studied a single crystal of Cs 2NaPrCl fi with elastic neutron

scattering and confirmed a commensurate phase transition at 155 K. No

additional Bragg peaks have been seen. Inelastic scattering measurements

are being made to determine if this phase change is a second order

transition driven by softening of an optical phonon mode, as in the

structurally similar compound K^ReCl^, where the transverse phonon

branch which rotates the (ReClfc)

-"^ octahedra softens first at T, then at

X . Preliminary data on Cs2NaPrCl£ reveal a soft T-point phonon with

energy less than 2 meV at room temperature and with an energy width which

61
RRD COLLABORATIVE PROGRAMS

is considerably broader than instrumental resolution. Work is in

progress to further characterize this mode.

1. L. Morss, M. Siegal, L. Stenger/ and N. Edelste±n:.;JnQi'g. Chem 9_ 1771

(1970)

2. G. E. Fish and H. J. Stapelet^n, J. Chem. Phys. (to be published)

.

3. C. J. O'Conner, R. L. Carlin, and R. W. Schwartz, J. Chem. Soa. 3 Faraday Trans. II 73, 361 (1977)..

4. J. W. Lynn, H.

V H. Patterson, G. Shirane, and R. G. Wheeler, Solid

State Comm. 27, 859 (1978).-

CRYSTAL-FIELD EXCITATIONS IN (RE)Mo^S

J . W . Lynn

(University of Maryland j College Park, MD)

and .— i .v ,*- .,,; ,*• (National Bureau of Standards, Washington, DC)

.

.' • *

•. and

R. N. Shelton

(University of California at San Diego, LaJolla, CA)

Ternary Chevrel-phase superconductors of the general formula

(RE)MogXg (RE=rare-earth, X=Se, S) exhibit a variety of unique and interesting phenomenon related to the competition between magnetism and superconductivity. The neutron scattering technique is ideal to study the

magnetic properties of these systems since the magnetic state can be

directly probed on an atomic level without the perturbing influence

of the superconducting state such as shielding currents, for example.

The first neutron study of the magnetic ordering in these materials was

performed-^- on ErMo^Seg. As anticipated on the basis- -of specific heat

studies, strong magnetic Bragg scattering was found to develop at IK,

well below the superconducting transition at V5.5K, with the samples

remaining superconducting. However, the complicated magnetic diffraction

62
RRD COLLABORATIVE PROGRAMS

<0 * o

10

00

2 r* r*

ii

ii h 1*

uitu 02/ s * uno O

o fc-

(0c

(0

- in H

>

a

c

UJ

- O

8If) O

o

IX)

a) n3 ,£> 0) a] » > >

CU U U

u a> <D 3 CO CO w ,o ua « O

a) <u co p. u <u a cO

a) c

•H -H

CO o -u

cu so

O

a)

CO ,Q

CO

CO 3

>> CO u u

O 4-1

<D

CO

CO 3 4-1 w 3 -H O CD

*-> U C

CO U) cOM

03 a) 4-i 4) A

W 4J H

vD CO O M-( fl O

>»

00

1-4 0)c

a)ou

<vN

4-> ^

CO to

a)

o

•H

4-1 4-1 3 -H O -3•a

co cO »h a

o c

jO >h cO a 4J •h co cu

1-1 4-J U

<U 'H <U *J OX 4J X 5

CO CU O

« ^ t4

r-H 00

<u o >

M

0)

3

a.o m q,

a, s

•H

J-i ao

jO

CO OJ cO U 4J

<U CO d cj

4-1 CO -3 OH CU X! >-rJ CO H

CO

0)M • CJ >

cu m <u X 3

4J U "3

cO

0) CO

l-i CO CU /-> AAA

o s

o

4-1 CO

>

CU HCO

CUM

3

00 •H

ft,

uitu QL/siunoQ

63
RRD COLLABORATIVE PROGRAMS

pattern could not be interpretated in a straightforward manner and the

possibility that only impurity phases were magnetic could not be ruled

3 out. More recently, HoMo^-Sq was found to become ferromagnetic, at

which point the superconductivity established at 1.25 was destroyed.

Similar reentrant ferromagnetic behavior has been observed in the re- lated system E'rRh^B/^.

In all of these materials the characteristic magnetic energies

are typically IK or less. We can then anticipate that the crystal field

may play a dominant role in determining the magnetic properties of these

systems. The crystal structure of the Chevrel phase is rhombohedral

(R3) with one formula unit per unit cell. The rare-earth ions occupy

a single primitive lattice which is nearly cubic since the rhombohedral

angle is close to 90° . Hence to a first approximation we expect the

lifting of the free-ion angular mementum degeneracies can be described

by a crystal field with cubic symmetry as calculated by Lea, Leask and

Wolf. 6

The polycrystalline samples used are the same samples studied by

9 specific heat and susceptibility. All the data were taken with the

triple-axis technique with a PG(002) analyzer. The monochromator was

a "bent" PG(002) crystal for the lower energy transfers, and a "bashed"

Cu(220) for the higher (>30meV) energy transfers. Figure la shows a typical scan at low temperatures on TbliogSeg. The peak at zero energy

transfer is the {ill} Bragg reflection. The crystal field transition

out of the ground state is clearly seen at 5.0meV. The transition was unambiguously identified as crystal field in origin due to its temperature and wavevector dependence. At higher temperatures a second ex- citation appears as shown in Figure lb. This is consistent with a cu- bic crystal field, and gives a singlet as the ground state. For ErMogSeg, on the other hand, three transitions out of the ground state were

observed. This may indicate that the small rhombohedral distortion has

a significant effect on the crystal field in this material, or that there

is more than one inequivalent crystallographic site for the Er in these

64
RRD COLLABORATIVE PROGRAMS

samples. In the latter case, however, it is not possible to distinguish

whether these additional sites are in the Chevrel phase or in an impurity

phase.

Extensive measurements have been taken on HoMo^Sg in an attempt

to observe crystal-field excitations in this material, without success. All measurements were taken above the ferromagnetic transition of 0.67K.

Scans with an energy resolution of O.SmeV revealed no excitations in the

range 0.5->-22meV. This indicates that the crystal field excitations li are severely broadened due to lifetime effects, or the excitations lie

outside this energy range. Both possibilities suggest that the sulfides

differ sharply from their selenide counterparts. High resolution

(92|ieV) measurements showed no excitations in the region 0.05-KL.0 meV

and high energy scans revealed no excitations at small wavevectors in

the range 30 to 70 meV

.

1. J. W. Lynn, D. E. Moncton, G. Shirane, W. Thomlinson, J. Eckert and

R. N. Shelton, J. Appl. Phys. A2_, 1389 (1978).

2. R. W. McCallum, C. C. Johnston, R. N. Shelton, W. A. Fertig and

M. B. Maple, Sol. St. Comm. 24_, 501(1977). R. W. McCallum (thesis)

3. J. W. Lynn, D. E. Moncton, W. Thomlinson, G. Shirane and R. N.

Shelton, Sol. St. Comm. (to be published)

4. M. Ishikawa and Fischer, Sol. St. Comm. 23_» 37(1977).

5. W. A. Fertig, C. C. Johnston, L. E. deLong, R. W. McCallum, M. B.

Maple and B. T. Matthias, Phys. Rev. Lett. 39_, 1164 (1977); D. E.

Moncton, D. B. McWhan, J. Eckert, G. Shirane and W. Thomlinson,

Phys. Rev. Lett. 39_, 1164 (1977).

6. K. R. Lea, M. J. Leask and W. R. Wolf, J. Phys. Chem. Solids 23,

1381 (1962)

.

65
RRD COLLABORATIVE PROGRAMS

A TRIPLE AXIS POLARIZED BEAM SPECTROMETER

C. J. Glinka and J. J. Rhyne

and

R. W. Williams

(Naval Surface Weapons Center, White Oak, MD)

A triple axis polarized beam neutron spectrometer is now in operation at the NBSR. The instrument is a fixed incident energy spectrometer which utilizes a pair of Heusler alloy crystals, C^MhAl, as polarizing monochromator and polarization-sensitive analyzer. The crystals, mounted in 3 kgauss permanent H-magnets, are used in transmission

o geometry and have a measured peak reflectivity of 35% at 2.4A for one spin state and a mosaic spread of 15 minutes. At present, the average

polarization of the beam over its 2.5 x 3.2 cm^ area is typically 90%.

Over the central region of the beam the polarization is higher, approaching

the intrinsic polarizing efficiency of the Heusler crystals which has

been measured to be approximately 98%. Efforts are continuing to improve

the uniformity of the polarization by eliminating stray fields along

the beam path. An rf spin resonance flipper coil, situated in the

incident beam, is used to reverse the sense of polarization. A flipping

efficiency of 99% over the entire beam area is routinely obtained.

A split-coil superconducting magnet has been received and tested

successfully at fields up to 75 kgauss. The magnet has a 3.8 cm bore

so that rather large samples may be accommodated and maintained at

temperatures from 4 to 300K. Also available for polarized beam work

at higher temperatures, up to 900 °C, is a vacuum furnace which mounts

between the pole pieces of a conventional vertical field electromagnet.

To illustrate the performance and energy resolution of the spectrometer, a constant-Q scan of the incoherent elastic scattering from

nickel is shown in figure 1. The incoherent cross section for Ni is

entirely due to isotopic incoherence which has no effect of the spin state

of the incident neutrons. The scattered beam thus has the same polarization as the incident beam. The scan in figure 1 illustrates, therefore,

66
RRD COLLABORATIVE PROGRAMS

1000

800

(0c° 600

c

o

t= 400

200

• Flipper Off

- o Flipper on

E Q

= 14.7 meV

Vo^o

Ni Incoherent

Scattering

1

°

U

«*88888S

1

-6.0 -4.0 -2.0 2.0 4.0

Energy Transfer (meV)

6.0

Figure 1. Constant-Q scan of the elastic incoherent scattering frora

nickel measured with the incident beam polarized "up"

(filled circles) and "down" (open circles)

.

the discrimination which is presently attainable between neutrons scattered

with spin "up" (flipper off) and those with spin "down" (flipper on)

.

The small residual peak in the flipper on data is due to the imperfect

polarization of the incident beam.

A study of the polarization dependence of the critical scattering

from isotropic ferromagnets is currently in progress using the polarized beam spectrometer. Measurements of the magnetic form factors of

both the iron and rare earth atoms in Laves phase (RE)Fe~ compounds

are also planned.

67
RRD COLLABORATIVE PROGRAMS

STUDIES OF THE EFFECTS OF DEUTERIUM IN TITANIUM

H. Alperin

(Naval Surface Weapons Center, White Oak, MD)

and

(National Bureau of Standards, Washington, DC)

and

J. J. Rush

Phonon measurements on a titanium single crystal have been

initiated to determine if any lattice decohesion results from the

presence of deuterium at interstitial positions in the titanium

lattice. Prior to loading with deuterium phonons have been measured

in the [0110] and [1120] directions at room temperature and. at

385C. The crystal has been successfully loaded with ^7% deuterium

and measurements at 385°C are in progress.

1. Alperin, H.A, Pickart, S. J., and Rhyne, J. J., "Small Angle

Neutron Scattering from Rare-Earth from Alloys", J. Appl.

Cryst 11, 105 (1978)

.

2. Pickart, S. J., Alperin, H. A, and Rhyne, J. J., "SmallAngle Magnetic Scattering from a Dilute Amorphouse Fe (Tb)

Alloy", Phy. Letters^ 64A, 337 (1977).

STRUCTURE AND DYNAMICS OF 3 V2D

H. Jo and S. C. Moss

(University of Houston, Houston, TX)

and

J. M. Rowe and J. J. Rush

The phase diagrams of VH and VD are particularly complex, and

show a large difference for the two isotopes. For the composition

68
RED COLLABORATIVE PROGRAMS

V2D there exists a narrow single phase region only for the deuteride

which can be approached directly (with no mixed phase region) from

the a or solute phase. In the 3 phase, the metal atoms form a body centered tetragonal lattice (to first order) with the deuteriums

ordered on alternate [101] planes. The whole structure is monoclinic

as determined from neutron powder diffraction measurements. The

properties of the system allow one to cool a single crystal from the a to the 3 phase without shattering. Although in general, 3-phase

crystals are multidomain, small samples suitable for diffraction

can be obtained. One such sample has been used to collect a full

data set which is presently being analysed.

In addition, we have attempted to measure the phonon dispersion

relation for a multidomain sample of ^ l/2cc. In spite of the fact

that the optic modes are known to lie very low in energy from powder

measurements, we were unsuccessful in our attempt. Thus, efforts

are underway to produce a large single domain crystal using uniaxial

stress. This sample will then be used to study the lattice dynamics

of this system.

CHAIN DEFORMATION IN RUBBER

C. Han

(Polymer Science and Standards Division)

and

B. Mozer

and

J. A. Hinkley and H. Yu

(University of Wisconsin, Madison, WI)

Small-angle neutron scattering (SANS) has made possible direct determinations of the chain dimensions of polymers in the hulk amorphous

state. The technique takes advantage of the isotopic difference in

neutron scattering cross sections of deuterium and hydrogen. In this

69
RRD COLLABORATIVE PROGRAMS

cD

2-

reu

15<

q

2 10 3 (A )

Figure 1. Excess scattered intensity in log scale vs. q^(Guinier plot

where the ordinate is in arbitrary units) for samples con- taining 3% deuterated chains (•) for bulk mixture and (o) for

network. Error bars, standing for one standard deviation,

are given only for a few representative data points. The

two curves are drawn according to the Debye form factor which

gives the best fit for the mixture (solid curve) and for the

network (chained curve)

.

work, we give a brief account of a study of the chain dimensions in rubber

networks by the SANS technique. We ask what happens to the linear

dimension of a chain upon cross-linking its ends into a network and how

this dimension changes when the network is stretched. In the theory of

rubber elasticity, it has generally been hypothesized that the macroscopic

extent of stretching of a network is af finely transformed to the ex- tension ratio of each adjoining pair of cross-links. We are now able

to test this hypothesis. We could effect the experiment because we were

able to prepare uniform networks, whose elastic strands are of mono- disperse chain length and cross-links are of uniform functionality.

Incorporating a small fraction of perdeuteriopoly (butadiene) (3% or less)

in its hydrocarbon matrix,, we have performed SANS measurements on the un~ cross-linked mextures and on -the cross-linked networks with and without

an axial strain.

70
RED COLLABORATIVE PROGRAMS

1.8

1.0

0.8-

Junction

Affine

Phantom Network

J L

1.0 1.2 1.4X

1.6 1.8

Figure 2. Ratio of the apparent radius of gyration to that in the un- strained state vs. extension ratio. R= (Sy2) ^/(Sy^) A=l^.

The error bars are estimated from the sum of relative errors

of slop and intercept of the linear extrapolation procedure

without taking into account possible correlation between

the two. Three curves are drawn respectively for the chain

affine model (- ) where R=A, for the junction affine model

( ) where R=[(l + \

2 )/2]%t and for the phantom chain model

( ) where R=[(5 + A2)/6]^when the cross-link functionality

is three.

We first present the results for the determination of chain

dimensions in bulk samples. The root mean square radius of gyration

2 1/2

(S )

' (henceforth, just called the radius of gyration) is extracted

from the excess scattered intensity, I(q), in two ways. The first

method is to fit the data at small q to a least squares straight line.

Because the scattering profile is in fact curved for the observed range

of q (S 2

) , this method systematically overestimates (S 2

) . a simulation study shows that the error is about 20% for the range of q used.

Inasmuch as chain conformations in the bulk amorphous state have been

71
RED COLLABORATIVE PROGRAMS

shown to be well described by the Gaussian coil model, we have also fit

the I(q) data to the Debye form factor for a Gaussian coil. The results

of both fitting procedures are collected in table 1. The radius of gyration

at infinite dilution derived from the second method is 36.9 + 10. 5A. This

o agrees with the unperturbed radius of gyration of 35 A calculated from the

literature values taking into account the variation with microstructure.

The study of the chain dimension in a rubbery network is restricted

to networks containing 3% (by weight) of deuterated chains, hence we re- present the radius of gyration as the apparent one which is not corrected

for its possible concentration dependence. On the basis of a plausible

2 assumption that the concentration dependence of (S ) for the free chain

in the bulk state does not differ from that for the network chain in the

unstrained state, we can now compare the chain dimensions in the two states.

In figure 1, Guinier plots for the 3% mixture and the 3% network are presented. Within the experimental uncertainty, the apparent radii of

gyration are indistinguishable. We therefore conclude that the chain dimension of polybutadiene in the free state is the same as in the unstrained

network. An identical experiment on set B samples gave the same result

(see table 1) . The results for the study of chain dimensions in a network under

unaxial strain are also collected in table 1. We summarize the data

by plotting in figure 2 the ratio of apparent radius of gyration at a given A. to that at the unstrained state (A=l) against A. The ex- perimental data are compared against three different models in figure

2. The first is that of chain affine deformation, whereby every pair

of chain segments within an elastic strand moves af finely with the

macroscope strain. The second model is the classical one which we call

the junction affine deformation, descriptive of the case when only the

cross-link junctions deform affinely with the macroscopic strain. This

is the model that is commonly invoked in the statistical mechanical description of elastic free energy of an isolated chain in a network. The

third is the model of the phantom network proposed by James and others.

Given the experimental uncertainty and the limited range of X covered , 72
RRD COLLABORATIVE PROGRAMS

Table 1. The Apparent Root-Mean Square Radius of Gyration, of Poly-

(butadiene-d.5) in Amorphous Bulk Mixtures and in Uniform

Networks

.

Perdeuteriochain Method 1° Method 2*

content, % A' B< A B

3

2

1 Infinite dilution

Mixtures

40.6 ± 3.9 35.4 x 4.4 42.7 x 4.8 40.8 x 6.3

Networks (3% perdeuteriochain)

27.0 x 4.0 28.8 x 3.8 35.3 x 8.5 36.9 x 10.5''26.3 x 3.5

Extension ratio X

11.22 1.25

1.43 1.53 1.55

39.4 x 4.1 40.6 x 4.8 41.5 x 5.4 43.8 x 7.6 54.8 x 3.4 58.6 x 12.2 53.0 x 6.2

30.4 x 4.S 26.0 x 6.7

" From the limiting slope of small q.

b Pitting to the Debye form factor. 'Two sets of samples described in the Experimental Section. * The only value extrapolated to infinite dilution.

we can conclude that our preliminary data are in qualitative accord with

the prediction of the model of junction affine deformation.

73
C. Non-RRD Programs

ACTIVATION ANALYSIS: SUMMARY OF 1978 ACTIVITIES

Thomas E. Gills

(Inorganic Analyticial Research Division)

The Activation Analysis Group of the Inorganic Analytical Research

Division is physically located in the NBS Reactor building. It has

at present a staff of 8 full-time members and has programs in the areas

of reactor neutron activation analysis, photon activation analysis, nuclear track detection and prompt gamma activation analysis. These programs include both basic and applied research projects and analytical

programs on a wide variety of sample types. This is a summary of the

activation analysis programs and activities during the past fiscal year.

1. Research Programs with Activation Analysis

a. The National Environmental Specimen Bank (NESB)

Thomas Gills, Harry Rook, Robert Greenberg

Development of Sample Storage

and

Analysis Techniques for NESB Samples

For the past two years the U.S. National Bureau of Standards has

been cooperating with the U.S. Environmental Protection Agency in ex- amining sampling, storage and analytical methods for use in archiving

environmental samples for retrospective analysis. During the past year

investigations of different parameters, utilizing activation analysis, were made in the sampling and storage areas, particularly for the determination of trace elements. The effects of microbiological action

on trace constituents' concentrations and distributions are well documented. However, the mechanism for complete long-term elimination of

that microbiological activity has not been well documented. Freezing has

long been applied as a technique for storage; however, no study has previously been made to document the reliability of this method of storage

for more than a short period of time. Recently, the analysis and sub74
NON-RRD NBS PROGRAMS

sequent reanalysis of a selected animal tissue (bovine liver) that had been

stored frozen at -80°C for a period of one year gave us the first indication that our preliminary protocols for the storage of fresh tissue are

valid, i.e., polyethylene sealed samples stored at -80°C. The original

organ had been subset sampled and the remainder homogenized with a com- mercial food blender and portioned into six polyethylene ice cube trays

containing 14 samples each. The trays were individually sealed in 1 mil

thick polyethylene film and stored in a chest type -80°C freezer. Analyses

were performed on the subsets of the liver tissue before freezing to provide initial trace elemental concentrations and to verify contamination

free homogenization of the sample.

After one year, one tissue cube was removed from each of the six

trays and the trays resealed for future studies. The selected tissue

cubes were freeze-dried and analyzed using the same analytical procedures utilized in the initial analyses. A comparison of the results

of this reanalysis to those originally obtained is given in table 1.

No detectable losses occured as a result of homogenization, freezer storage and freeze-drying of the liver tissue. These findings support recent

studies that in freeze-drying, minimal losses and/or contamination of

trace elements occur. The complexity of the chemical composition of many environmental

and biological materials and the extreme low levels of toxic elements

pose a problem in selecting a method or procedure that would ensure precise and accurate analysis. Methods must be sensitive, specific and

capable of measuring an analyte within required uncertainty levels.

Recently new or improved analytical methodologies have been developed to

analyze typical NESB type samples. The most promising methods include

a new multi-element separation procedure coupled with neutron activation

which enables the simultaneous determination of Cd, As, Sb, Se, Cu and Cr

.

As a test of the accuracy of results, previously certified NBS Standard

Reference Materials were analyzed. The results are shown in table 2.

A second procedure currently under investigation will allow for the

75
CU

CO

en & H

co • >> X) H CU

03

O

C

O

**"

nM

ft

NON-RRD NBS PROGRAMS 3

CO ^H CM <». pH rH, <u + 1 st

vOooo+ 1 + 1 VOmooo+ ;

COooo

CNOOo+m

5+.002

5+

enooi 1 o O i

r^ r«- r^ r^

u o o o o o o

^H /—-s • • • • • • co co o •H o CO m m CO JN H m 4J CO o o o O O o o (Q • • • • • • M + 1 £' +1 + + 1 + 1 ft 4-J cu o> o o\ c-^ r~^ ,d CO CN en m CN CN CN

CO 00 • • • • • • cu •H

CO 0) CN st

m r- 00 ^ 13 H O o o o

CO (3 o + 1 + 1 + 1 + 1 +1 a O s CT> vO o CN CN

cd -d 00 r^ 00 00 00

T3 cu a 4J 00

a!

M •*-»

m N, CN

H rH, H,

O 00

C + £' + + + + cu ft P. N CTi cy> cr» CTi 00

60 CU en St en en en en

CO Pi no CO o 4-1 PI ^H

m en rH CN

CO

O 3 + + + 1 + + i •H o 00 CT> ov ov o u 4J vo VO VO vO r-> cu cO > M

•H 4J r^ st, ^o, st CN r^

rH

a CU + 1 + + 1 + + ! + ! a) Pm VO CTi St m VO CO a\

CU o r-» r-- l-«. r^ ra vO c ti rt •H o CU > u S O *—

,o IWo

XI CO

cu

m cu CO

u o rH

C o & o

4J • e 00 r^

m VO vO •H VO

CO o3

cO CO

H en 4-1 CO /^> CU3

cm •H H< CO O

•~\ I h£

co •H

CO /^~s -^

OH •H j> V-*

CO o CU T> CO J-l fJ >. cu 4-) 4J H •H >, CU rH 4J cO CU CO CO N

cfl +1 co s CO -a !>, rH

O XJ

C ^w-' S cu c rH

H CU <! CO cu 00 4-) CO CO H Pm «H

4-J cu 00 o CU 4-»

C CU }-l cu rH o g CO CO CO 4-1 >-i *d » CO ft 6 o ,a CU U-l o : rH CO 42 e o ffi 3 cu & CO cu

CU 3 cd r3 CO 00 « i

43N

CU rH CO CO a) SH CO cu H ft cu •

!-i

O • CU CU Xi E ft • 1—1 • CU S-i H u u

co CO >•> • H

H > > u

H pt.

h

H CO

H

H

H 1—1 H <*

w

H + * 76
NON-RRD NBS PROGRAMS

simultaneous determination of Hg, Pt, Pd, Au and Os. These multielement techniques will greatly reduce the analytical cost when large

numbers of samples are processed during the operation of the specimen

bank. The coupling of proper sampling and storage to these improved

analytical techniques will allow the accurate determination of trace

constituents of importance, to human health.

Table 2. Determination of As, Sb , Se, Cr, Cd, and Cu

in NBS Subbituminous Coal SRM 1635

(concentration in yg/g)

Matrice NBS SRM Subbituminous Coal 1635

Element _ Certified Values This Work

As 0.42 + 0.15 0.44 + 0.05

Sb (0.14) 0.12 + 0.01

0.82 + 0.04 Se 0.9 + 0.3

Cr

Cd

Cu

2.5+0.3 2.48+0.08

0.03 + 0.01 0.029 + 0.007

3-6+0.3 3.56+0.36

Values in parentheses are NBS information values.

77
NON-RRD NBS PROGRAMS

b. Trace Elements in Solar Cell Silicon

R. M . Lindstrom, R. F. Fleming, H. L. Rook, and P. J. Paulson

The Low-Cost Solar Array project, managed by Jet Propulsion Laboratory for the Department of Energy, has as its goals the production of

electricity from sunlight at a cost of $2.00 per peak watt in 1983, and

50c per watt in 1986. This latter goal is a reduction by a factor of 20

from the present cost of photovoltaic power, to a level competitive with

more conventional sources of electricity.

One factor of major importance in this cost reduction is the

price of silicon from which solar cells are made. For space

applications, where cost considerations were secondary and production

quantities small, semiconductor-grade silicon was satisfactory and

appropriate. It is expected that cheaper silicon, produced in much

larger quantity at a lower grade of purity will be optimum for terrestrial applications, and an important determinant of the price of silicon

is the degree of purity that will give acceptable solar cell perfomance.

Information to date is still incomplete, but some elements seem to be

tolerable in concentrations above 1 yg/g while others must be below 1 ng/g# Accurate measurement of concentration at the low nanogram range

is difficult, because of the small signal available from the small

•quantity of analyte, and because of the likelihood of large noise from

environmental contamination. A program of measurements by neutron activation analysis (NAA) in collaboration with isotope dilution spark source mass spectrometry (IDSSMS) is underway to address these analytical problems. Interference-free NAA sensitivities in the NBSR have been calculated

table 1 and shown to be reasonable representations of reality in favorable

cases. The conditions assumed were irradiation to saturation or for 8

hours (whichever is shorter) at 6 E13 n/cm 2 s, followed by counting for

2 half-lives or 8 hours (whichever is shorter) in contact with a Ge(Xd)

detector of 15% efficiency (25 cm; relative to 3" x 3" Nal) . The determination limit L

q

(Currie, Anal. Chem. 40_ 586 (1968) is that amount of

element which is determinable with 10% relative standard deviation from

78
NON-RRD NBS PROGRAMS

Table 1. - Interference-Free Determination Limits

for Neutron Activation

Determination Limit

Element

Radioisotop

24Na

\

Ey

(KeV)

1368

Calculated

at/ cm-

> ng

2.5E10 4.2E-4

Observed

ng

* Sodium 15.0 h

* Magnesium 27Mg 9.1 m 844 1.2E14 2.0

* Aluminum 28A1 2.2 m 1779 1.0E13 1 . 9E-1

Silicon 31 Si 2.6 h 1266 8.9E15 180

Chlorine 38C1 37 m 1642 2.3E12 6.7E-2

Calcium ^\a 4.5 d 1297 2.8E16 8100

Scandium ^Sc 84 d 889 1.6E11 5.3E-3 3E-3

*Titanium 51T

. 5.8 m 320 2.1E13 7.2E-1

* Vanadium 52V 3.8 m 1434 2.3E11 8.3E-3 2

*C hromium 51Cr 28 d 320 4.2E12 1.5E-1 0.7

* Manganese 56Mn 2.6 h 847 1.1E9 4.2E--5 0.1

*Iron 59Fe 45 d 1099 6.9E14 28 40

Cobalt ^o 5.3 y 1173 2.1E12 8.9E-2 8E-2

*Nickel 65Ni 2.5 h 1482 6.4E12 2.7E-1 200

*Copper 64Cu 13 h 511 5.3E9 2.4E-4

*Zinc 69mZn 14 h 439 2.6E11 1.2E-2

- 65 Zn 240 d 1116 6.7E13 3.1 3

Arsenic 76As 26 h 559 6.7E9 3.6E-4

* Zirconium 95 Zr 66 d 757 1.3E15 86

- 97 Z r 17.0 h 658 6.3E12 4.1E-1

Molybdenum 99mTc 67 h 141 1.2E11 8.1E-3

Tin H3sn 120 d 392 3.9E12 3.3E-1

Antimony 122 Sb 2.7 d 564 1.7E10 1.5E-3 8E-3

Gold 198Au 2.7 d 412 3.1E8 4.4E-5

Determination limit mass of element oi atomic concentration in a 1-g

sample determinable with 10 ] Dercent precision (r s.d.), hiised on Poisson

counting statistics of the fiill--energy peak v;ith zero baseline. See Text

79
NON-RRD NBS PROGRAMS

Table 2. Trace Elements in Silicon

Concentration Estimated

Sample No. Element ng/g atoms/cc

xlO" 15

Uncertainty

% rsd

W-002-00 Cu 0.24 0.006 30

W-003-00 Mn 4.8 0.12 4

W-005-Mn Mn 38. 0.96 4

W-007~Cu Cu 2.6 0.050 18

W-013-Mn Mn 10.2 0.26 17

W-017-Cu Cu 502. 11.0 2 W-019-Cu Cu 12.6 0.28 11

W-020-00 Cu 0.26 0.007 40

W-026-Mn Mn 0.33 0.008 22

W-027-Mn/Cu Mn 35. 0.89 20

W-027-Mn/Cu Cu 56. 1.23 7 W-030-Cr/Cu Cu 58. 1.29 6

W-031-Cr/Mn Mn 61. 1.55 4

W-041-Ni/Cr/Cu Cu 0.22 0.005 40

W-047-Cu/Ni/Zr Cu 56. 1.24 6

W-051-Cu/Ti Cu 0.08 0.002 100

W-055-Cu Cu 1.2 0.027 40

W-056-Cu Cu 2050. 45. 2

C5ES Mn 25. 0.64 6

M1BS Mn 0.093 0.0024 10

B-M3BD Mn 0.84 0.021 30

B-M11BS Mn 3.7 0.094 17

Sample W-056-Cu was analyzed by both techniques. Neutron activation

found 235 +5 ng Cu in the sample, and isotope dilution spark-source

mass spectrometry found 234, after a 3 ng blank was subtracted. The

concentrations found in many of the above samples differ from predictions

or previous analyses, or both.

Poisson counting statistics of the full-energy peak with zero baseline.

A series of silicon samples (supplied by JPL) deliberately doped

with trace impurities has been measured. A representative set of data

is presented in table 2, from which the quality of the analyses in real

samples can be judged.

80
NON-RRD NBS PROGRAMS

c. Gamma Dose Measurements Using A Plastic Detector

B. S. Carpenter and L. J. Pilione

The measurement of x-ray and Co-60 Y"ray dose and dose distribution

by dielectric plastic detectors has been reported in much detail over the

last 10 years. The absorbed dose is determined by measuring changes in

such quantities as: mass, chemical etch rate, optical absorbance, color,

etc., of the plastic detector. The advantages of using plastic detectors

are: low cost, handling ease, the dose field is not disturbed, relatively simple readout, long-term document storage, etc.

In the present study Cronar, polyethylene terephlate, detectors were

exposed in the following NBS facilities to the indicated doses:

Co-60 (0.2 - 20 MRAD)

10 M-watt Research Reactor (0.1 - 10 MRAD)

Spent Fuel Storage Pool (1 - >20 MRAD)

The reactor exposures were done in RT-4 with a mixed field of neutrons

(10 -10 ) and gamma rays. Included in each plastic sample packet was

a radiochromic dye detector for purposes of calibration. The gamma

dose was determined by measuring the change in optical density of visible

light as a function of chemical etch time (6N-NaCH@40+l°C , 10 min etch

intervals)

.

The results indicate that a maximum optical density at a specific

chemical etch time correlates with the gamma dose in the range: 2-20

MRAD. Detectors exposed to an equivalent gamma doses in the reactor and Co-60

facilities show no discernable shift in their gamma response, indicating

the neutron exposure does not alter the gamma dose signal. It was also

observed that a thin gelatin layer had been placed on one surface of the

plastic at the time of manufacture. Chemical removal of this layer prior

to irradiation resulted in a complete loss of gamma signal.

Work is continuing in optimizing the dose signal by changing the

etchant concentration and temperature.

81
NON-RRD NBS PROGRAMS

d. Determination of Thermal Neutron Flux for Fission

Track Geochronology

B. Stephen Carpenter

The nuclear track technique (NTT) has found an application in geology since 1962 when Price and Walker (1962) found that natural mica

contained a number of fission tracks from the spontaneous fission decay

of U-238. With this discovery and the simplified age equation suggested

by Price and Walker (1963) , the geologist had a new tool for determining

ages of various minerals. The age determination from the equation follows:

A. --£2Bs . l(*t)a

p i ,238

A

f

Where,

A = Age of Sample (yr)

Ps = Spontaneous fission track density (Tern"" 2

) Pi = Induced fission track density (Tern-2

) I = Isotopic ratio of 2 35u/238u

($t) = Total neutron fluence (n*cm ) a = Effective cross-section for the 235U (n,f) reaction (cm2

)

, = Spontaneous fission decay rate of U(yr~l),

A

f

was based on the simple theory that the absolute rate at which spontaneous

fission events or tracks from U-238 accumulate in minerals is proportional to the uranium content and, therefore, the measurement of both

the spontaneous track abundance and the uranium content is necessary.

The uranium content is determined simply by inducing fission to a measurable portion of the uranium. This measurement utilizes the fact

that thermal neutrons cause fission of U-235. The final procedure of

the age measurement is to count the spontaneous tracks, then the sample

is exposed to a known thermal neutron fluence in a nuclear reactor and

82
NON-RED NBS PROGRAMS

the newly induced tracks are counted. From the ratio of these two track

densities, together with the thermal neutron fluence, the age is then calculated.

The simplicity of both the technique and theory have caused many

users difficulties and problems in the determination of ages. One of the

problems arose in selecting the best decay constant since several values

exist. To a large extent this problem has been resolved by users reporting

the value used in the determination. However, the neutron fluence value

cannot be as easily resolved, since each nuclear reactor is unique and

their neutron spectra will vary.

-2 -1

The neutron flux, $(ncm s ) , is comprised of two components and is defined as

00 J

epl

= <t> th / <f>„,(E)dE

0.5ev

where 4> t u is the thermal neutron flux, <J> ep:j_ is the epithermal neutron flux

per unit of energy and dE is the energy interval. The contribution from

each of these components to the total neutron flux is a function of

sample position relative to the core during irradiation and type of moderation used. \s the neutron flux changes with energy so does the

A 23S effective cross-section, G for the JJU(n,f) reaction which is defined

as

o = a

Q

l 1+ Z*2±_ _o T epi •

4>th - a

0'

where a is the 2200 m's- -*- value of the cross-section for U-235, 582 x lO-'^cm , and I is the resonance integral for the U(n,f) reaction

at infinite dilution.

83
NON-RRD NBS PROGRAMS

o " /

Q < E > dE = 280 x 10"24 cm2,

_ J- E

I. =

0.~5ev

So if the flux is not highly thermalized, a. large fraction of fissions

will be induced from U-235, as well as U--238 and Th-232, by epithermal

neutrons.

There are several ways by which either the total neutron flux or the

thermal neutron flux can be determined. One method of determining the

neutron flux as suggested by Eleisher et al. (1975), Carpenter and Reimer

(1974), and Kleeman and Lovering (1970) is to use glasses with known

uranium content which are then irradiated with metal foils. The

radioactivity produced from the metals during the irradiation is used

to determine the neutron flux. Then the neutron flux observed by the

metal foil is related to the track density produced in the glass.

In order to determine the thermal activity, A t^, induced from the

total activity, At t

, in the foil monitor, it is necessary to know the

cadmium ratio R , of the metal foil for the irradiation position used.

If the absorption of part of the epithermal neutrons in the cadmium

shield is neglected, then At ^ = A tot (l-l/RC(j) . Finally, the thermal

neutron flux is calculated from the activation equation.

. A -A t th "-^

(1-e

m r

1

NO

m

where N is the number of target atoms present in the metal foil; Cm

is

2 \ the thermal cross section of the atoms in the metal foil, cm ; Am is t decay constant of the product nuclide; and t is the irradiation time.

84
NON-RRD NBS PROGRAMS

e. Simultaneous Determination of Arsenic, Antimony Cadmium,

Chromium, Copper, and Selenium in Environmental Material,

by Radiochemical Neutron Activation Analysis

M. Gallorini, R. R. Greenberg, and T. E. Gills

In studies of environmental pollution, elements such as arsenic,

antimony, chromium, cadmium, copper, and selenium are among the most

interesting due to their toxic nature. These elements are usually found

at very low concentration in most samples of interest. The accurate

analysis of these elements can be accomplished only by techniques that are very sensitive and selective. Neutron activation analysis usually

meets these requirements; however, in many cases the elements to be

determined must be separated selectively from neutron activated matrices.

Utilizing Radiochemical Neutron Activation Analysis (RNAA) , one can obtain maximum sensitivity, accuracy,- and selectivity.

Usually, the choice of the radiochemical procedure to be followed is

dependent upon the elements to be determined, the nature of the materials

to be analyzed, and the simplicity of the chemistry. Several radiochemical procedures such as solvent extraction, distillation, ion exchange

chromatography, precipitation and electrodeposition can be used to obtain

satisfactory results.

However, when used alone most of these procedures are not suitablej

for simultaneous multielement analysis. Furthermore, when several

chemical steps are necessary, quantitative separation becomes extremely

difficult; often, the determination of chemical yields, which can con- tribute to the analytical error is required.

In this work a multielement radiochemical separation procedure has

been tested and optimized to determine six elements simultaneously in

different NBS environmental Standard Reference Materials (SRM's).

Hydrated Manganese Dioxide (HMD) , an inorganic ion exchanger was used

for the retention and subsequent determination of As, Cr, Sb , and Se,

while a solvent extraction system using diethyldithiocarbamate compounds

was used to determine Cd and Cu.

85
NON-RRD NBS PROGRAMS

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86
NON-RRD NBS PROGRAMS

Table 2. Determination of As, Sb , Se, Cr, Cd, and Cu in NBS SRM

western coals

concentration in yg/g

Matrice NBS SRM Western Coals

Element Certified Values Found Values

As 0.42 ± 0.15 0.44 ± 0.05

Sb (0.15)± 0.12 ± 0.01

Se 0.9 ± 0.3 0.82 ± 0.04

Cr 2.5 ± 0.3 2.48 ± 0.08

Cd 0.03 ± 0.01 0.029 ± 0.007

Cu 3.6 ± 0.3 3.56 ± 0.36

The reported value for each element consisted of ten determinations

Values in parenthes are NBS information values.

In an attempt to demonstrate applicability to matrices having

different chemical compositions, the following NBS materials were

analyzed: Orchard Leaves (SRM 1571), Bovine Liver (SRM 1577), and Subbituminous Coal (SRM 1635).

The results are shown in tables 1 and 2. The results indicate very

good agreement between certified and found values, demonstrating that

the procedure is accurate.

The retention of arsenic, selenium, chromium, and antimony on HMD

in 1M HNO-j is highly selective and quantitative, while the elution of

Cd and Cu is complete.

The decontamination of the elements of interest from Sodium-24

and other radioactive matrix interferences can be estimated to be a factor of 10 8

.

87
HON-RRD NBS PROGRAMS

The simplicity of the method permits a rapid isolation of the radioisotopes of interest without many chemical steps. The quantitative re- covery avoids the calculation of the chemical yield. The sensitivity and

accuracy obtained in this work demonstrates the validity and the precision

of this radiochemical procedure.

f. Development of a RNAA Procedure for the Determination of Hg

and Noble Metals in Rocks

M. Gallorini and T. E. Gills

The analysis of rocks for the determination of Hg, Os , Ru, Pt, Au

and Ir are always difficult due to the very low concentration of these

elements. Activation Analysis has the sensitivity for these ultra-low

determinations when coupled to radiochemical separations.

Radiochemical separations procedures found in the literature for

many of these elements are often involved due mainly to the nature of the

chemistry of noble metals. This work presents a radiochemical separation

procedure which allows the determination of seven elements simultaneously.

The general scheme adopted is shown in figure 1.

The samples and carriers were dissolved by fusion in a nickel

crucible using a mixture of Na and NaOH (10:2). The fusion was carried out in a Vycor tube under an air stream at 850°-900° as to

quantitatively retained the mercury in a joined tube cooled at liquid

nitrogen temperatures.

Osmium and Ruthenium were then separated using a fractional distillation of their tetroxides which were distilled from sulfuric acid

solution by adding solium bromate. The two tetroxides were then absorbed

and collected in cold sodium hydroxide. Gold, Platinum, Iridium and

Palladium, remaining in "pot" solutions, were absorbed on ion-exchange

resin (IONAC SR-3) from a solution 6M in HCL. This ion-exchange resin

showed high retention and selectively for these metals.

88
NON-RED NBS PROGRAMS

Table 1. The analysis of U.S.G.S. rock (PCC-1) using radiochemical

activation analysis

Element P g/g Found Mean £ Literature Vg/g

Hg 11.2, 9.13, 10.1, 9.60 ± 0.8 7.7, 10, 4

9.9, 8.8, 9.3,

9.1, 8.9

Os 13, 9.99, 8.93, 11.1 ± 1.7 6.7, 6.4, 11, 12.3

12.5

Ru 13, 11.3, 10, 12.0 ± 1.4 6.5, 8.4, 9.5, 9.8,

13.7, 12 10.3, 11.3

Au 0.7, 0.78, 0.7, 0.74 ± 0.04 0.6, 0.7, 0.73, 0.8,

0.71, 0.8, 0.73 0.8, 1.4, 1.6, 3.2

Pt 14, 13, 12, 11, 11.6 ± 2.3 5.1, 3.5, 8, 15

8.7

Pd 5.6, 5.5, 6.8, 6.6 ± 1 3.0, 5.9, 6.0, 7,

8, 7 13, 29

Ir 3.9, 3.4, 4.6, 4.1 ± 0.6 3.5, 2.6, 5, 5.1, 5.2,

5.1 5.6, 5.7, 6.6, 7.1, 8

The results obtained in the analysis of U.S.G. (PCC-1) rock are shown in table 1. The concentrations found are compared with those

reported in the literature. The quite wide spread for some elements

reported in literature reflects the difficulty of determing low con- centrations of noble metals. The results obtained with this method,

are in good agreement with and inside the range of the reported values.

The multielement capability of this radiochemical procedure with

its degree of sensitivity places radiochemical activation analysis among

the best analytical techniques for the determination of these elements

at ppb levels. The method is relatively simple, quantitative, and

accurate.

89
NON-RED NBS PROGRAMS

g. The Use of Radiochemical Activation Analysis For The

Determination of Hg and Cd

R. R, Greenberg

A radiochemical separation procedure has been developed to separate

Hg and Cd from other neutron-activated products. The procedure is

based on solvent extraction and involves the use of Nickel Diethyldithiocarbamate [Ni (DDC) ] to remove Hg and Zinc Diethyldithiocarbamate [Zn (DDC) 2] to remove Cd.

The basic procedure followed involved dissolving the samples with

HNO- and H~SO, in a Telfon-lined bomb to prevent loss of Hg during

dissolution. After dissolution H-0- was added to the solution to

destroy the various NO compounds formed.

The pH of each solution was adjusted to 1.5 with NHL and the

solution was transferred to separatory funnels containing 20 ml of

0.005 M Ni(DDC)„ in chloroform. After shaking for 2 minutes, the

organic phase containing Hg was drained from each funnel and 20 ml of

0.005 M Zn(DDC)_ in chloroform was added. Each funnel was shaken for

two minutes and the organic phase containing Cd and most of the Cu was

drained into a second separatory funnel. Cd was then back extracted by

shaking for 15 seconds with 20 ml of 2M HC1.

This procedure was tested on SRM 1577 (Bovine Liver) and good

agreement with the certified values of Hg and Cd was observed.

h. Prompt-Gamma Activation Analysis

G. E. Gordon, W. H, Zoller , W. B. Walters, D. L. Anderson,

M. P. Failey

(University of Maryland, College Park, MD)

,

R. M. Lindstrom

A collimator and shutter have been installed in the V5 reflector

position at the NBS reactor by the University of Maryland group in co- operation with the NBS staff, in order to initiate studies of a new

90
NON-RRD NBS PROGRAMS

analytical technique: neutron-capture prompt y-ray activation analysis

(PGAA) . A detection system based on a large, high resolution Ge(Li)

detector surrounded by a Nal crystal has been developed for measurement

of prompt Y~rays of energies ranging from 80 keV to 11 MeV. With a temporary external beam tube in place, neutron and y~ray backgrounds were

investigated prior to design and construction of a well-shielded beam

tube and massive shielding for the detection system. With the backgrounds

made suitably low, it has been possible .to investigate y-ray spectra of

a wide range of samples. These spectra are being analyzed to identify

species contributing the observed lines. Whenever an element's presence

is suspected, standards of the pure element or simple compounds must be

irradiated to determine its complete spectrum. This is necessary in order to determine which lines are useful for analytical purposes and which

have interferences from other elements. From the results to date, it

appears that PGAA will be able to measure the following elements in many

types of samples: H, B, C, N, Na, Al, Si, S, CI, K, Ca, Ti, V, Mn, Fe,

Sm and Gd. Many other elements will be measureable in certain classes

of samples. Furthermore, the list of elements is incomplete, as not all

lines have yet been identified in the spectra. The quantitative application of the method is being tested using a wide range of NBS Standard

Reference Materials whose elemental compositions are well characterized.

Measurements have been made for about twelve elements in several standards,

In general, the agreement with previous measurements is quite good.

91
NON-RRD NBS PROGRAMS

i. Analysis of Archaeological Artifacts by Instrumental Neutron

Activation Analysis

M. J. Blackman

Trace and minor elemental concentrations were used to construct

characteristic elemental profiles for a number of different types of

archaelogical artifacts and geological source samples. Artifacts were

matched with source samples to determine the geological origin of the raw material and/or the place of manufacture of the artifact. The objective was to attempt to answer questions concerning the development

and evolution of exchange systems and cultural contacts between peoples.

Continuing research on three different types of material is being

conducted. Seventy-five obsidian artifacts from two archaeological sites

in southern Iran, dating from the 4th through the 2nd millenia B.C. and source samples from several obsidian flows in central Turkey, western

Turkey and the Armenian S.S.R. have been sampled and analyzed. Seven

distinct elemental groups have been recognized in the artifacts and

three of these groups have been assigned to known obsidian occurrences,

two in western Turkey and one in the Armenian S.S.R.

Over one-hundred clay objects, including tablet blanks, beads,

figurines, and spindle whorls from four archaeological sites in Iran

and one site in Iraq have been sampled and analyzed. The objective was

to use classes of clay objects which have a low probability of being

trade items to delineate the trace and minor element variability in the

local clays from each of the five sites. Excavated clay sealings used

to seal objects which may have been traded between the various sites

were then compared to the profiles generated for the clay objects to

attempt to establish exchange networks. This research is on-going and no definite conclusions can as yet be reported.

The third type of material being investigated is ceramics from the

late 4th and early 3rd millenia levels at Tal-e Malyan, Iran, the site

92
NON-RRD NBS PROGRAMS

of the ancient city of Anshan and from several small villages in the

same general area. The objective is to attempt to establish, through

trace and minor element profiling of the ceramics, the local and regional

influence of the developing center at Anshan. This research is also ongoing with an insufficient number of samples so far analyzed to draw any

conclusions.

j . Absolute Determination of Phosphorus in Neutron Transmutation

Doped Silicon

R. F. Fleming

Very uniform and precise phosphorus doping of silicon ingots is

achieved by irradiation in a thermal neutron flux via the reaction JUSi

(n,y 31Si,3~) 31P [IEEE Transactions on Electron Devices, Vol. ED-23, #8,

p. 800 (August, 1976)]. Such high quality doped silicon, used for solar

cell and power thyristor production, is being processed in ton/year

quantities at various nuclear reactors around the world. Determination

of the phosphorus concentration in the range of 10 -10 1 ' atoms /cm^ is a very difficult analytical problem if carried out after the fact.

It has been recognized [Bickford, N. A. and Fleming, R. F., "Silicon

Irradiation Facilities at the NBS Reactor", to be published in the Proceedings of the Neutron Transmutation Doping Conference, Columbia,

Missouri (1978)] that a direct, absolute measurement of the phosphorus

in the ingot can be obtained by gamma counting the 2.62 hour Si-31 activity

with a calibrated detector:

vr AO T MP = T

~rY

Where Mp = total P-31 in the silicon ingot

Ao = decay corrected count rate

t = irradiation time

E = detector efficiency for E = 1266 KeV

T = number of 1266 KeV gammas/decay of Si-31

93
NON-RRD MBS PROGRAMS

The absolute accuracy of this technique clearly depends on how well the

branching ratio, T is known. Unfortunately only a single, 25 year old

measurement exists [Lyon, W. S. and Manning, J. J., "Radioactive Si-31",

Phys. Rev., 9_3, 501 (1954)], and it appears to be in error by as much as 50 percent. Therefore, a careful measurement of the gamma-ray branching

ratio has been undertaken jointly with Dr. Francis Schima of the Center

for Radiation Research. Preliminary results indicate that a determination

at the +3 percent level will be obtained.

k. Determination of Helium-3 Depth Profiles in Metal Tritides

R. F. Fleming

A joint effort has been undertaken with Sandia Laboratories,

Albuquerque, to investigate the use of thermal neutron beams to determine the amount and depth profile of helium-3 in metal tritides by means

3 3

of the He(n,p) H reaction. The metal tritides, MT„ are stoichiometrically loaded with tritium which, as it undergoes its natural 12-

year beta decay, produces the helium-3. These tritides are fabricated

as targets for high yield 14-MeV neutron generators which are used for

defense, medical therapy, and analytical purposes. The buildup of the

helium-3 and its migration in the tritide may have a significant effect

on the long term integrity of the neutron targets.

Initial measurements with implantation-loaded He-3 targets have

given proton spectra which are very encouraging. It appears that sensi15 3 tivities of less than 10 He-3 atoms/cm are possible and that, by

unfolding the proton spectrum measured with a surface barrier detector

and using the appropriate stopping power, depth resolutions of less than

o 100A can be obtained.

Work is now underway to modify the NBS Reactor horizontal beam BT-3

to allow the study of actual metal tritide samples.

94
NON-RRD NBS PROGRAMS

1. Field Test of Reactor Track-Etch Neutron Flux Monitor

B. S. Carpenter

As a part of the international reactor safeguards program, tracketch monitors are currently being evaluated as a reliable method for

providing an independent record of reactor power history. Lack of re- liable and complete supporting data in past tests of the monitors has

made interpretation of past test results almost impossible. The need

therefore is to evaluate the track-etch monitors carefully and accurately

by testing them under well defined experimental conditions.

The track-etch monitor is an externally-powered device designed to

record the neutron flux from operating reactors and other sources for

extended periods of time. A strip of 35 mm wide polymer tape is driven

past a group of six fissionable nuclides which are exposed to the local

neutron flux. A given fraction of the fission fragments generated penetrate the tape producing radiation damage tracks that are subsequently

etched and counted to permit a reconstruction of the temporal flux

history to which the monitor was exposed. The monitor is equipped with

15.2 meters of tape which is adequate for over one year's operation at

the nominal speed of 2.9 cm per day. Under these conditions the monitor

6 — ? —1

is designed to operate at a neutron flux of 10 n«cm S . This reactor

operating history should show the periods of operation, shutdown periods

and/or other significant changes in reactor operating conditions. Any

data concerning the neutron flux level, flux spectrum and gamma flux at

the monitor's test location will be noted and recorded. Similar types

of monitors have been installed in other reactors under the supervision

of the Arms Control and Disarmament Agency and the International Atomic

Energy Agency.

A similar monitor was also installed in the Nuclear Channel #2

Detector Well of the NBS Research Reactor for 56 days from 25 July to

19 September 1978. This monitor was exposed to a thermal neutron flux

95
NON-RED MBS PROGRAMS

6 —2 —1

of 1x10 n'cm s~ and a gamma dose rate of 140 R/h. The radiation

activity from the monitor after removal from the detector well was

<0.1 mR/hr. The NBS Research Reactor is the best characterized reactor

in the world and should provide reliable tests and data of the tracketch monitor.

In collaboration with NBS, IAEA plans to install and evaluate the

track-etch monitor at several typical U.S. power reactors for a period

of three to six months under well-documented conditions of environmental

and reactor operations.

m. NDA-Gamma-Ray Spectrometry

B. S. Carpenter

In order to compile an archival gamma-ray spectrum library of known

2 35

U enrichment levels, counting standards were prepared from the NBS

SRM Uranium Isotopic Standards. These standards were prepared with the

help of L. A. Machlan and J. S. Maples, of the Inorganic Analytical

Chemistry Division, from the U o Q stock material fired at 800 °C for one hour, then a nominal 300 mg of material was transferred into thinwindow lucite holders and sealed.

Data reduction techniques and methods for determining the atom

percent of U-235 on low-enriched materials (<L0 percent) have been applied

to the archival gamma-ray spectrum library of known U-235 enrichment

levels. The result of this work has been to establish calibration curves

for the determination of the U-235 atom percent.

96
NON-RRD MBS PROGRAMS

n. Determination of Trace Concentrations of Bismuth by Activation

Analysis

R. F. Fleming

When bismuth is irradiated with thermal neutrons and the resulting

five day Bi-210 is allowed to decay, one obtains a source of Po-210

which decays by alpha particle emission:

209Bi <">?) 210

Bi £—> 21°Po 2 > 206C1 Pb

a = 19 mb 5.01 day r ° 138.4 day

This Po-210 alpha activity may therefore be counted to provide an analysis

for bismuth. Among the stable elements bismuth is unique in producing a long-lived alpha activity.

Since alpha counting is characterized by high efficiencies and low

backgrounds, the method should be accurate, sensitive and reliable. Alpha

detection will be done using both electronic counters for high accuracy

and rapid determination, and the plastic track detectors - developed by

Drs. Carpenter and Pilione - for highest sensitivity when precision

better than + 5 percent is not required. The only possible interference

with the 5.3 MeV Po-210 alpha is that from the natural decay chains of

uranium and thorium. These can be exactly accounted for by running a parallel unirradiated sample as a blank.

Two approaches to the alpha counting will be developed: nondestructive direct counting of the sample, and counting the extracted Po-210

following post-irradiation dissolution of the sample.

1. Non-destructive Counting

This technique can determine bismuth at the sub-yg level, but re- quires an accurate value of the alpha particle range in the matrix (or

a bismuth standard with the same matrix) to obtain values for the con- centration. The nuclear track technique, which is at least 100 times

more sensitive than electronic detection, will also provide a mapping

of the bismuth surface distribution.

97
NON-RRD NBS PROGRAMS

2. Post-irradiation Dissolution

If after irradiation all of the Bi-210 is allowed to decay and the

sample dissolved, the resulting Po-210 can be spontaneously plated out on a silver foil (yield _>99.7 percent) for counting. By counting against

an SRM alpha standard the bismuth concentration is obtained directly.

Using this technique, bismuth can be determined at the sub-ng level,

interferences from thorium are eliminated, and those from uranium are

reduced by at least a factor of ten.

A second nuclear method using photon activation analysis and Ge(Li)

counting with the reaction 2093i(y } 3n)206Bi has been developed by Dr.

George Lutz. Accurate results have been obtained at the 10 ppm level

and the method is completely independent of the neutron induced alpha

activity method.

o. Cadmium Analysis by Radiochemical Neutron Activation Analysis

R. Greenberg

Cadmium has been suspected of causing detrimental health effects in

humans even at very low levels. Since Cd is commonly found at the trace

or ultra-trace level, many analytical techniques do not have the sensitivity to accurately determine the concentration of this element in many

environmentally improtant materials . In a recent interlaboratory com- parison of oyster material carried out by the International Atomic Energy

Agency, the reported values of the Cd concentration ranged from 0.4 to

4.4 yg/g [Intercalibration of Analytical Methods on Marine Environmental

Samples - Progress Report No. 13]. This illustrates the problems involved in determining the "true" Cd concentration in biological materials

even when this concentration is relatively high. These problems become

more serious as the Cd content decreases. In addition, there are some

instances in which the total amount of material available for analysis

98
NON-RRD NBS PROGRAMS

is very small, such as for hair samples or certain types of atomosheric

particulate samples. Analytical techniques capable of measuring very

small amounts of Cd are therefore required.

Radiochemical Neutron Activation Analysis (RNAA) has been routinely

used at the NBS to analyze Cd in a variety of environmentally important

matrices. The method used to separate Cd from other neutron-activated

products is solvent extraction. Zinc diethyldithiocarbamate [ZnCDDC^]

in chloroform will quantitatively extract Cd from an aqueous solution

over a pH range from 1 to 12. In addition to the extraction of Cd, Zn

(DDC>2 will also extract Cu, which can interfere with the Cd analysis by

producing a high background level of radiation. This can be avoided by

first extracting with Bi(DDC)., in chloroform which removes Cu, but not

Cd. Copper concentrations can, therefore, be determined in addition to

Cd.

This two-extraction radiochemical separation procedure is very versa- tile and is often used as part of a larger multielement analysis scheme.

As demonstrated in section e and g of this report. Hydrated manganese

dioxide (HMD) was used to retain As, Sb, Se, and Cr prior to extraction

and the eluted fraction is then extracted with Bi(DDC)3 to remove Cu,

and then with Zn(DDC)2 to remove Cd.

A number of NBS Standard Reference Materials were analyzed by the

previously mentioned procedure, and the Cd and Cu results obtained are compared with the certified values in the following tables. Very good

agreement is observed, demonstrating the accuracy of this technique.

99
NON-RED NBS PROGRAMS

Table 1. Cadmium in various SRMs

Concentration-yg/g

This Work Certified

Orchard Leaves (SRM 1571)

Pine Needles (SRM 1575)

Bovine Liver (SRM 1577)

Rice Flour (SRM 1568)

Wheat Flour (SRM 1567)

Sub Bituminous Coal (SRM 1635)

River Sediment (SRM 1645)

Urban Particulate (SRM 1648)

0.116 + 0.008

0.194 + 0.009

0.295 + 0.015

0.029 + 0.005

0.030 + 0.005

0.030 + 0.002

10.2 + 0.4

71.2 + 3.7

0.11 + 0.01

< 0.5

0.27 + 0.04

0.029+ 0.004

0.032+ 0.007

0.03 + 0.01

10.2 + 1.5

75 +7

Table 2. Copper in various SRMs

Orchard Leaves (SRM 1571)

Pine Needles (SRM 1575)

Bovine Liver (SRM 1577)

Rice Flour (SRM 1568)

Wheat Flour (SRM 1567)

Sub Bituminous

Concentration-yg/g

This Work Certified

11.6 + 0.4

3.04 + 0.16

185 + 7 2.12 + 0.09

2.21 + 0.10

3.56 +0.18

12+1

3.0 + 0.3

193 + 10

2.2 + 0.3

2.0 + 0.3

3.6 + 0.3

100
NON-RED NBS PROGRAMS

p. Organic Mercury in Tissues

R. Zeisler, T. E. Gills

Increased interest of ecologists and analysts has been focused on

the ratio of organic mercury to total mercury content of biological and

environmental samples. The determination of the total mercury content

of these matrixes using NAA procedures has been extensively investigated

in the past years, and some RNAA methods are considered fully reliable

for this purpose. So far, the determination of organic mercury has been

carried out by use of other methods, e.g., gas-chromatography . Thus,

two samples have to be analyzed by different methods to yield the desired

information on the ratio of organic mercury to total mercury content.

Well developed extraction and volatilization techniques are cur- rently being investigated for the isolation of methylmercury from biological tissues.. Since the possible radiolytic damage to organic mercury

compounds during irradiation cannot be fully assessed, we are developing

and applying a modified extraction technique to be used in a pre-irradiation and "normal" RNAA scheme. This will yield information about the

changes of the chemical form of organic mercury during irradiation.

The separation of organo- or methylmercury is based on the volatilization of methylmercury cyanide formed in the reaction of methylmercury

in a sample with hydrocyanic acid released by the interaction of a cyanoferrate with sulfuric acid at elevated temperatures. The methylmercury cyanide released is captured on cysteine paper in a microdif fusion

cell. The paper is then placed in a flux of neutrons and the mercury

quantitatively determined by neutron activation analysis.

The feasibility of this method is currently being tested. SzilardChalmers reactions that can change the chemical status of the mercury and

possible losses of mercury from the sample have to be assessed. Test

analyses have proven that irradiation has to be performed in sealed quartz

containers. Samples can then be counted either "instrumentally" in the

irradiation container or after using the combustion methods. Both

101
NON-RRD NBS PROGRAMS

require comparable samples and standard configurations. The use of

mercury deposits on filter paper (comparable to the proposed cysteine

paper) is being evaluated.

In addition, the volatilization method for mercury determination

after the reduction of the inorganic mercury by SnClo will give the possibility of cross-checking of the mercury contents. The reduction method

is claimed to be selective for the inorganic mercury (only 0.5% of the

organomercury is released). This is, however, critically dependent on

the chemical treatment of the samples. This has to be carefully investigated.

The procedure utilizes the volatility of mercury and its compounds;

more importantly the inherent sensitivity of neutron activation analysis

along with minimum use of reagents and solvents should provide increased

accuracy over currently used methods.

q. Determination of Iodine in Foods by Radiochemical Activation

Analysis

H. L. Rook, R. M. Lindstrom

Iodine is an essential element in the human diet. The recommended

daily allowance is only 150 micrograms per day, so that in order to

measure the intake of iodine accurately, analyses of foods at a level of

1 ppm or less is required. In addition, there is little information on

the reproducibility of avialable analytical methods. We recently measured iodine in six freeze-dried food materials, as a contribution to an interlaboratory comparison coordinated by M. Heckman of Ralston Purina

Company. Orchard Leaves (SRM 1571) and Oyster Tissue (SRM 1566) were

analyzed in parallel. Duplicate samples of all materials were irradiated for periods up to five minutes in the RT3 pneumatic facility of the

NBS Reactor and combusted in a flowing oxygen atomosphere. Chlorine and

102
NON-RRD NBS PROGRAMS

Table 1. Iodine content of foods and SRMs

Sample

SRM 1571

Orchard Leaves

SRM 1566

Oyster Tissue

Stew

Corn

Milk

Vegetables

Protein

Wheat

Cereal

Tuna

Iodine found

(yg/g, by wt)

0.177

0.185

0.188

2.87

2.71

0.057

0.046

0.0094

0.0084

6.24

6.42

0.064

0.068

0.0099

0.0090

0.59

0.63

Mean I concentration

(yg/g)

0.183

2.79

0.051

0.0089

6.33

0.066

0.0095

0.61

bromine were separated by passing through hydrated manganese dioxide and

the iodine trapped on silvered quartz wool. The procedure has been

published [H. L. Rook, J. Radioanal. Chem. 39, 351 (1977)].

Our results are given in the attached table 1. Comparison among

eight laboratories shows poor agreement. Other investigators using

chemical methods for analyses appear to be limited by blanks. Agreement

with the other activation analysis laboratory reporting, however, was

better; but, there was a calibration discrepancy even there. Clearly

the state of iodine analysis in foods requires further work.

103
NON-RRD NBS PROGRAMS

r. Silicon Irradiation Facilities at the NBS Reactor

N. A. Bickford and R. F. Fleming

A program of silicon irradiation is being carried out at the National

Bureau of Standards 10MW, heavy water moderated reactor using the reaction ->^Si(n,Y)-*-l-Si(3

-

) P to achieve phosphorus doping of high uniformity

at precisely known levels.

Characterization of Irradiation Facilities

When comparing irradiation facilities for transmutation doping of

silicon, two quantities, in addition to the spatial uniformity of the

neutron flux, are important: 1) the P-31 production rate and 2) the

rate of radiation damage. The P-31 production rate is determined by the

magnitude of the thermal neutron flux while the radiation damage rate

has three components:

1) The unavoidable damage resulting from the ^^Si(n, y) 31si reaction itself, which is essentially proportional to the P-31 production.

2) The carnage resulting from high energy neutrons whose energies

are well above any appreciable cross section for the 30si(n> y) 31gi reaction.

3) The damage resulting from the intense gamma ray field.

In order to establish some measured quantities which can be used

to characterize irradiation facilities we should consider the several

radioactivities that are produced when pure silicon is irradiated in a reactor flux. When the 2.62 hour half life Si-31 decays there is a

2 1266.1 KeV gamma ray emitted with an intensity of about 0.07%. The

specific activity of this gamma line is of course directly proportional

to the P-31 doping rate. The high energy neutrons always present in

any reactor spectrum produce three other activities in silicon via the

reactions 28Si(n,p) 28A1, 29 Si(n,p) 29A1 and 30 Si(n,a) 27Mg. Both the Al28 and the Mg-27 activities are also produced by thermal neutron reactions on any aluminum or magnesium impurity that may exist in the silicon,

The 6.52 minute Al-29 activity is unique and results in a gamma ray at

104
NON-RRD NBS PROGRAMS

1273.3 KeV. This suggests that a simple characterization of a silicon

irradiation facility can be accomplished by irradiating high purity

silicon and then gamma counting the Si-31 and the Al-29 activities produced.

The corrected count rate, Ao, for any particular activity is defined as

Ao "

At x ANe

(1-e )(l-e )

" A6 ,-| e -1

A6

ere

A = In 2 = decav constant

half life

N = net counts in the photo peak

t^ = decay time from end-of-irradiation to start-of-count

x = irradiation time

A = counting live time

6 = counting dead time

We propose the ratio A (-*-*-Si) /Aq (29a1) as a measure of the ratio

of phosphorous production to neutron damage in an irradiation facility.

Although the silicon damage function has a significantly different

energy dependence then the y Si(n,p) ^9^.1 cross section, both are sensitive to the flux of high energy neutrons. The fact that the gamma ray

energies of the two activities are only 7 keV apart means that the difference in the Ge(Li) detector efficiencies can be ignored and no detector calibration is necessary. The measurement consists of counting

the 1273.3 keV line of Al-29 and then, after it and the 1267.9 keV single

escape line from Al-28 have decayed away, counting the 1266.1 keV Si-31

line.

The measurement of AQ

( Si) and of the ratio AQ (31si) /A ( 29A1) were

carried out on the vertical tubes G2 and G4 and on the pneumatic tube

105
NON-RRD NBS PROGRAMS

Table 1. Doping parameters in NBS reactor

A (31-Si)

IRRADIATION FACILITY A (31sl)**

°

( 29A1) G2* 1.0 0.74

G2 (2" Above)* 0.99

G2 (6" Above)* 0.89 0.40

G4* 1.28 0.83

RT4 0.086 9.51

*Core Gap Center-Line

**Normalized to G-2 Center-Line Value

RT4. The results are shown in the table 1. We see that G4 not only

has a higher P-31 production rate than G2 , but that the production-todamage ratio is somewhat improved. Notice also that at 6 inches above

core midplane in G2 , which is in the fueled region, the production-todamage ratio has dropped significantly. The results in RT4 show that

if high P-31 production rates are not necessary it is possible to obtain

doping with greatly reduced fast neutron damage. The precicted phosphorous

doping rate of 7.5 x 10-"-3 atoms cm~3 hr- -'- is in good agreement with

measured values.

1. Bickford, N. A. and Fleming, R. F. , "Silicon Irradiation Facilities

at the NBS Reactor", Proa. Second International Conference on Neutron

Transmutation Doping of Semi-oonduotors (1978)

106 -
NON-RRD NBS PROGRAMS

2. SRM Certification Program

T. E. Gills

An essential function of the National Bureau of Standards (NBS)

is the production and certification of materials that have accurately

established characteristics which can be used to determine that a measurement system provides meaningful information. These materials,

identified as standard reference materials (SRM's), are certified for

particular chemical or physical properties. During the last fiscal

year activations analysis both instrumental and radiochemical, was

used in the certification and homogeneity testing of 17 different SRM's,

Such an effort was made possible through the group's capability in

multielemental analysis made possible by an effective automation and

data reduction system.

The following is a list of various matrices analyzed by Activation

Analysis

.

SRMs Other Materials

a.b.

c.d.

e.

f.

g.

h.

i.

j«

k.

1.m.n.

o.PqRice Flour a. Polymers

Wheat Flour b. Silicon

Copper Benchmarks c. Graphite

Eastern Coals d. Plastic Ware

Western Coals e. Flu Vaccine

Air Particulate Dust f. Freeze-Dried Foods

Bovine Serum g- Raney Nickel

River Sediment h. IAEA Oyster

Fly Ash i. Shark Tissue

Bauxite J

• Recycled Fuel Oil

Orchard Leaves

Trace Metals in Water

Spinach

Pine Needles

Bovine Liver

Tomato Leaves

NBS Oyster

Though most of the group analyses were done on NBS SRMs, many materials

analyzed came from within NBS or the private sector.

107
NON-RKD ITBS PROGRAMS

a. Analysis of New Fly Ash SRM

R. R. Greenberg

Standard Reference Material 1633 (Fly Ash) was widely used in the

analytical community and after this material was sold out a new Fly Ash

SRM (1633a) was prepared. The homogeneity of this material was checked

using Instrumental Neutron Analysis (INAA) . During homogeneity testing

the concentrations of eight elements were determined and submitted for

OSRM certification.

Two different sample sizes were used for homogeneity testing —

50 mg and 250 mg. Two 50 mg samples and one 250 mg sample were taken

from each of 12 bottles of the new SRM. The samples were irradiated

with primary standards and samples of the old Fly Ash SRM in three

different rabbits. Midway through irradiation, each rabbit was removed

from the reactor, flipped end over end, and reinserted into the reactor

to ensure a uniform neutron flux within the rabbit. The primary standards

consisted of multielement solutions pipetted onto Whatman 41 filters and were described in last year's progress report. After irradiation, the

samples and standards were allowed to decay for one month and were

counted 15 cm from the detector. Data reduction was accomplished using

the NBS computer code QLN-1 supplemented by hand integration of poorly

defined peaks.

The concentrations of eight elements determined in the 50 mg

samples are listed in table 1. The concentrations of these elements

in the 250 mg samples, and the overall average concentrations in the

Fly Ash are listed in table 2. The observed standard deviations are consistent with the counting statistics demonstrating the homogeneity

of this material for sample sizes of 50 mg or more. The results of the analyses of the old Fly Ash SRM are compared

in table 3 with the certified and literature (1) values. Very good

agreement was observed.

1. J. M. Ondov etal., Anal. Chem. 47, 1102 (1975).

108
NON-RRD NBS PROGRAMS

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109
NON-RRD NBS PROGRAMS

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110
NON-RRD NBS PROGRAMS

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111
ITON-KRD NBS PROGRAMS

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112
NON-RRD NBS PROGRAMS

3. Facilities

R. M. Lindstrom and R. F. Fleming

A major addition to the data acquisition and processing facilities

of the group was the purchase of a Nuclear Data 6620 Nuclide Identification System. This system allows simultaneous operations from two display terminals in adjacent counting rooms. Each terminal contains two

independent ADCs (expandable in the future) , so the result is as if four

multichannel analyzers had been acquired. The system also contains 96 K

words of 16-bit memory, two disks with a total of 10 M bytes storage

capacity, a real-time clock, a magnetic tape deck, fast printer, and

Teletype. Software is available for data acquisition and display, peak

search and nuclide identification, a comprehensive set of file manipulations, and program development in FORTRAN, BASIC, and MACRO assembler.

All system resources are available to a user at any of the three terminals.

This system offers the opportunity to make a number of improvements

in our operations. With data processing now available in the counting

room, experiments can be monitored and modified as the measurements are

in progress without waiting overnight for a computer run. Qualitative

analysis in particular is much easier, with the gamma-ray tables now

stored in the computer. Interactive spectral data analysis is now

practical, with the user able to modify the method of data reduction to

fit the situation at hand. As we gain experience with the file

structure, real-time statistical control over the performance of the

counting systems will be implemented, with a major improvement on the

quality as well as the quantity of data.

113
NON-RRD NBS PROGRAMS

FISSIONABLE DEPOSIT MASS ASSAY

D. M. Gilliam, W. E. Slater, J. A. Grundl

(Nuclear Radiation Division)

The Neutron Field Standards section has continued to improve and

expand its mass assay program for the NBS collection of Reference and

Working Fissionable Deposits. A new alpha particle counting system has

been set up and put into routine operation. In addition to many routine

comparisons this system was used to compare the NBS U-235 Reference

Deposit (23S-2-2) with a very carefully assayed deposit (LASL Spare No.

1) from the Los Alamos Scientific Laboratory. A second comparison with

the LASL deposit was made by fission counting at the NBSR thermal column.

1. Alpha Particle Counting System

A low-geometry alpha particle counting system has been built to

allow routine mass assay intercomparisons and long-term integrity checks

for our fissionable deposit collection.

Figure 1 shows a schematic diagram of the arrangement of the system.

Flat and parallel surfaces and careful assembly technique make possible

highly reproducible vertical spacing—an imprecision of less than + 0.006

mm. The effect of this error in spacing reproducibility on the counting

effeciency is less than 0.03% and is usually hidden by statistical error. Larger geometric errors occur due to the deviation of the deposit backings

from perfect flatness . Admeasuring microscope is used to determine the

average deposit height (without touching the deposit) , so that departures from flatness up to + 0.1mm can be tolerated without incurring errors

in excess of + 0.2%.

The fixed low-geometry configurations themselves are regarded as artifact standards, comparable in long-term integrity to the most durable

standard alpha-emitting deposits.

Table 1 gives the results of the comparison of LASL Spare No. 1

and the UNB U-235 Reference Deposit.

2. Fission Counting Comparison

114
. ITON-RRD NBS PROGRAMS

Using a large fission chamber on loan from the Lawrence Livermore

Laboratory, the comparison- .of the LASL standard and the NBS Reference

Deposit was repeated by counting the fission rate of each deposit

simultaneously in a well collimated beam extracted from the NBSR thermal

column.

These results are also given in table 1. The mass used for LASL

spare No. 1 was 1550. 4ug.

Table 1. U-235 Isotopic Mass of NBS Reference Deposit 25S-2-2

Published Value

New Value from LASL

Spare No. 1 via a counting

New Value from LASL

243.3

+1.2%ug

247.0

jp.5%yg

247.5

+0.7%yg

DETECTOR

DETECTOR ft APERTURE

CENTERING RING (BRASS)

APERTURE

SPACER (AD

VACUUM HOLE

HOLDER a

SPACER -

CENTERING RING

(BRASS)

"-DEPOSIT

-Pt BACKING

- AL SUPPORT DISC

- RETAINER RING

Figure 1. Schematic View of Alpha Counting Geometry. Five spacer cylinders

of various heights permit values of Z from 15mm to 114mm. Three

sizes of aperture diameters from 6.3mm to 29.4mm are available.

115
NON-RRD NBS PROGRAMS

PRECISION GAMMA-RAY WAVELENGTHS

E. G. Kessler, Jr., R. D. Deslattes, W. C. Sauder and A. Henins

(Center for Absolute Physcial Quantities)

The unique high resolution crystal spectrometer, figure 1, we have

operating at NBS has produced a significant body of new results. 1 Initial operation has been in the range 0.05 < E < 1.0 MeV. First definitive results were published in early 1978. These gave values for

Au-198 411 and 675 keV together with Ir-192 206, 296, 308, 316, 468, 588,

604 and 612 keV. These results have a typical la estimate below 0.5

ppm. This represents a more than forty-fold improvement over previous

work.

A special feature of this work is that through absolute measurements using crystals calibrated by x-ray/optical interferometry, results are obtained directly connected to the Rydberg constant R^. This

facilitated revised evaluations of y-mesic and TT-mesic x-ray lines and

revised comparison with quantum electrodynamic calculations for the ymesic case. The revised reference wavelengths, together with improved

comparisons and analysis lead to the pattern of substantial agreement

between theory and experiment shown in figure 2. This resovles a longstanding difficulty historically linked to the vacuum polarization

correction to muonic x-ray spectra. In the case of pionic spectra the

main objects of interest are the strong interaction shifts and the 7T-mass.

Our new reference wavelength values have led to removal of previously

apparent inconsistencies between y-mass values derived from different

calibration algorithms.

Susequent work, carried out in collaboration with two visiting

scientists has produced new values for prominent reference lines in

Yb-169 and for Tm 84 keV. In the case of Yb-169, new values have been

obtained for the lines at 63, 93, 110, 119, 130, 177, 198, 261, and 307

116
1T0N-RRD NBS PROGRAMS

keV. In those cases of groups of three levels connected by cascadecrossover relations, closure tests failures were about 0.1 ppm. In

addition to the y-ray studies, a separate measurement of W Kai from an electron bombarded anode of a natural tungsten was carried out. This

result was such as to resolve historical conflicts between different

routes to estimating the location of Au-198 411 keV.

In a joint effort with the visitors^ mentioned above, we have

undertaken design and assembly of a new two-crystal diffraction instrument. The new design incorporates many features not found in the initial

attempt. These include: a greater angular range - 30° instead of 5°;

a more fully compensated optical path for the angle interferometers; full

computer control including atomospheric compensation; and, provisons for use of a stationary radiation source such as an in-pile n-y source or the primary proton target in a meson factory or an elemental anode in an electron accelerator. Construction is complete as of mid-August. Calibration and computer programming are underway. Initial measurements of

high Z x-ray spectra are expected in September at the NBS 4 MeV electron

Van de Graaff.

Finally, after many years since the initial proposal, we are, in

August, to make a first attempt to measure a particularly narrowed

annihilation radiation component. The narrowing process used involves

singlet-triplet mixing and thermalization by elastic collisions in a rare

gas (He) moderator at cryogenic temperatures. A massive transfer cask

with internal manipulators has been fabricated and tested. It will

receive from the NBS reactor a Cu-64 source of about 10 kilocuries.

This will be transported to the Y~ray measurement facility and inserted

by remote manipulation into the low temperature Dewar. After cool-down,

a superconducting solenoid provides the 2 kilogauss field needed to

optimally mix triplet and singlet wavefunctions . It is hoped that August will see the first trial run of this system. If it performs as predicted, a new and more accurate value for the electron's Compton wavelength, X

c

, will be obtained. When this is combined with the Rydberg

constant, R^, one obtains a value for the Sommerfeld fine-structure

117
NON-RRD NBS PROGRAMS

constant, a. In favorable circumstances, this value will compare well

in accuracy with that available from other sources. Following its initial application to high Z x-ray spectra, it is

of interest to consider application of our new fixed-source instrumentation to in-pile capture-y sources. This will permit extension of

the range of our optically based measurements through the range 2.0

< E < 10 meV. In addition to providing new and more accurate reference

values in this region, we envision two rather definite scientific opportunities. In the first place, we can measure the cascade associated

with n +

llf N ->

5 NC and n +

1 H -> 2 D. A mass spectrometer measurement

of the difference between the 5 N

1 H and 14 N H molecules (or ions) is

equivalent to this energy via the Einstein relation. It is easy to show

that these measurements imply a value for the electrochemical Faraday."

Leaving questions of accuracy aside, one also can think of applying the

high resolution and linearity of our instrumentation to the problem of

unscrambling complex nuclear spectra in the region of 2-4 MeV. This is

of particular interest in view of the recent success of the coupled

Boson model of nuclear excitation at just slightly lower energies, it is

reasonable to expect to see breakdown of the nucleon pairing associated

with the coupled Boson picture as one moves toward higher energies where

ultimately a statistical picture must prevail. For several reasons, such

studies as those just mentioned are not easily imagined to take place on

the NBS reactor. There are three reasons for this: first, the NBS

reactor is a very busy place with many NBS workers and visitors active

at any given time; second, the tangent ports which might be used for n-y

work have been preempted except for possible short term access; third,

13 -1 -2

there is a relatively low flux available, i 10 s .cm . It therefore seems desirable to propose such activity for the higher flux facility

14 2 -1

(8 x 10 cm • s ) at Grenoble which is also a place where y-ray work

is accorded a higher priority. A proposal to this effect is in preparation.

118
NON-RRD NES PROGRAMS

Figure 1. The two axis transmission spectrometer,

Q-x

<D UJ

I >>o

200.6 E(keV)

Figure 2. Comparison of recent muonic x-ray data with theory. The

hatched bands represent theoretical uncertainties. In the

absence of the revised y-scale, the theory bands would be

centered on the dashed lines and the agreement between

theory and experiment would be degraded.

119
NON-RRD NBS PROGRAMS

1. A detailed description of instrumentation and procedures is in preparation.

2. E. G. Kessler, Jr., R. D. Deslattes, A. Henins and W. C. Sauder,

Phys. Rev. Lett. 40, 171 (1978).

3. C. K. Hargrove, E. P. Hincks, R. J. McKee, H. Mes, A. L. Carter,

M. S. Dixit, D. Kessler, J. S. Wadden, H. L. Anderson and A.

Zehnder, Phys. Rev. Lett. 39, 307 (1977); T. Dubler, K. Kaeser,

B. Robert-Tissot, L. A. Schaller, L. Schellenberg and H. Schneuwly

Nuclear Phys. A294, 397 (1978).

4. A. L. Carter, M. S. Dixit, M. K. Sundaresan, J. S. Wadden, P. J. S,

Watson, C. K. Hargrove, E. P. Hincks, R. J. McKee, H. Mes, H. L.

Anderson and A. Zehnder, Phys. Rev. Lett. 37, 1380 (1976).

5. These visitors are: Dr. Ludo Jacobs, Leuven University and Mol

Laboratories, Belgium and Dr. Wolfgang Schwitz, Fribourg University

and SIN, Switzerland.

6. E. G. Kessler, Jr., R. D. Deslattes and A. Henins, Wavelength of the

W Ka 1 x-ray Line, submitted to Physical Review A.

7. W. C. Sauder and R. D. Deslattes, Jour. Res. NBS 71A , 347 (1967).

8. This point was originally brought to our attention by B. N. Taylor

about two years ago.

CAVITY FISSION NEUTRON SOURCE IRRADIATION FACILITY

V. Spiegel, E. D. McGarry, and R. A. Dallatore

(Nuclear Radiation Division)

The NBS cavity fission source operates at the center of a 30 cm

diameter spherical cavity located at the center of the NBS Research

Reactor graphite thermal column. Figure 1 shows the source-detector

capsule in detail and its location within the thermal column cavity.

Two disks of U-235 metal (16 mm dia x 0.13 mm thick) are placed above

and below a cylindrical cadmium box, which encloses the passive detectors

for exposure.

10 2 Fission neutron fluxes of ^ 2 c 10 n/cm sec are obtained between

the source disks at a separation distance of 1 cm. For thin detectors,

which are disk shaped and up to 12 mm in diameter, flux gradients are

120
NON-RRD NBS PROGRAMS

mild. In the axial direction the flux at + 1 mm form the midplane is

less than 5% greater than at the midplane; center-to-edge ratios are

about 1.3 for a 12 mm dia. disk detector. This small radial flux gradient

does not require that detector disks be extremely uniform. A radial

nonuniformity of 20% in a detector for example changes the activation rate

by less than 0.5%.

Fission neutron return for spherical cavities in graphite has been

studied extensively by means of neutron transport calculations in con- nection with the general development of standard neutron fields in spherical

geometry. For the 30 cm cavity at NBS, the response of fission threshold

detectors to fission neutrons returning to the cavity center is less than

0.5% of the uncollided fission neutron flux; for higher threshold detectors with 95% of its response above about 2 MeV the response to the

cavity return flux is less than 0.1%.

The NBS cavity fission source is not used generally for low-energy

integral detectors when high accuracy is required. The cavity return

correction for the U-235(n,f) reaction, for example, is nearly 10%. Self

DETECTOR STACK

CAOMIUM ENCLOSURE

Figure 1. NBS Cavity Fission Source.

121
NON-RRD NBS PROGRAMS

shielding of this near-l/E cavity return flux for conventional activation

foil thicknesses makes this correction uncertain to about twenty percent.

Disk detector irradiations are monitored by means of the In(n,n')

reaction in monitor foils placed adjacent to the exposed detectors. The

absolute neutron flux is obtained with the same In(n,n') reaction using

the procedure of flux transfer from the Cf-252 fission neutron irradiation

facility. In this procedure an In(n,n') foil activation is first obtained

in a known Cf-252 fission neutron flux. Based on this calibration the

In(n,n') activation during a cavity fission source exposure is translated

to an average U-235 fission neutron flux at the In foil monitor position.

The expression governing the flux transfer in terms of truncated

cross section is

G a _(>E ) ¥ _(>E ) D

r s \ i - cf cf p cf __p cvy r, N

, [(nv)

o

] cvy " G~ ' a 0^7 " f ^t) ' FT * [(nv)

o

] cf ' cvy cvy p) cvy p cf

where (nv) Q = fission neutron flux and "cvy" denotes the U-235 cavity

fission neutron flux at the In monitor position/ and "cf" the Cf-252

fission neutron flux for the In calibration exposure.

The ratios on the right side of the equation are, in order, the decay

correction factors (G) , In(n,n') truncated reaction cross sections (a),

spectrum fractions (¥) , and In detector responses in the cavity and at

the Cf irradiation facility. The truncated cross section ratio is

1.028 + 0.010 and the spectrum fraction ratio 1.021 + 0.014. Combined

with a typical error of + 1.% for decay correction factors and detector

response ratios, and + 1.4% for the Cf-252 fission neutron flux, [ (nv) ] f

, the flux transfer procedure yields a free-field U-235 cavity fission neutron

flux to an accuracy of approximately +2.5% (la).

15 2 Fission neutron fluences of up to ^ 1 x 10 n/cm may be obtained

at the NBS facility in day-long irradiations. The small irradiation

volume restricts multiple foil packages to thicknesses of a few millimeters.

122
D. Summary of Reactor Operations

All aspects of reactor operations continued to be excellent. Once

again, outstanding on-line performance, reactor utilization and fuel

efficiency were achieved. A summary of the overall operating statistics

for this and previous years is presented in the following table.

NBSR Operating Summary

1976 1977 1978

Reactor Operations to date, MWH 396,000

Reactor Operations for year, MWH 68,000

Hours Reactor Critical

Number of Days at 10 MW

On-line Time at 10 MW

Average U-235 Burnup

Number of Unscheduled Shutdowns

Number of Irradiations

Irradiations, Total Hours

Hours per irradiation

Number of Visitors

'6,000 459,000 525,000

i8,000 63,000 66,000

6,900 6,400 6,500

283 262 277

78% 72% 76%

55% 56% 52%

2 3 9

2,360 2,255 2,140

7,250 7,400 5,900

3 3.3 2.8

7,000 3,000 3,000

123
E. Service Programs

ACTIVATION ANALYSIS PROGRAM

OF THE FOOD AND DRUG ADMINISTRATION

AT THE NBSR

J. T. Tanner

(Food & Drug Administration, Washington, DC)

1. Analysis of Cement Kiln Dust

It has recently been discovered that the addition of cement

kiln dust to cattle feed decreased the amount of feed required by the

animals and improves the quality of their meat.

The effect of the dust was first observed by Georgia cattle

ranchers. They were liming their pastures with dust from a cement kiln

and dumped some into their cattle feed. The cattle ate the feed and

gained more weight than expected. Wheeler and Oltjen of the U.S.D.A.

verified the finding.

The dust is a complex, calcium-rich mixture of minerals that is

entrained when hot air is pulled out of the cement kiln. It does not

contain the alkalis and hardners necessary for cement to set . About 30

percent of its effect ^ results from a simple buffering action in the

gastrointestinal track. The other 70 percent might arise because: (a)

the dust contains some element that has not yet been recognized as an essential nutrient for cattle; (b) the intense heat of the kiln causes

the minerals in the dust to behave in some manner that is beneficial to

cattle, or (c) that the small size of the particles allow them to be

absorbed from the gastrointestinal track more easily than conventional

mineral supplements.

The Food and Drug Administration has no laws restricting the ce- ment kiln dust use in cattle feed, however, legal action may be taken

if any dust residue appears in the meat.

The cement kiln dust was analyzed by Neutron Activation Analysis.

Table 1 summarizes the results. These results along with analyses by othe

U

other FDA scientists will be studied to determine any potential hazard

to the consumer which may arise from this practice.

124
SERVICE PROGRAMS

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SERVICE PROGRAMS

2. Analysis of Sea-Derived Food Ingredients

To support the Generally Recognized As Safe (GRAS) Review co- mmittee, the FDA collected and analyzed a series of samples to determine whether there might be an unusual accumulation of toxic

elements in these sea-derived ingredients. In the interest of obtaining

broadest range of elements per analysis the samples were analyzed by

Neutron Activation Analysis (NAA) and Induction Coupled Plasma-Emission

Spectroscopy.

Table 2 summarizes the NAA results. There were no unexpected results. Kelp (whole seaweed) had high levels of arsenic which placed

it in the catagory of high arsenic contaminating foods.

This survey was intended as a broad screen to detect any un- usual accumulation of heavy metals in these substances. It appears

that during the processing of certain seaweeds to obtain agar, algimates,

and carrageenan, there is no accumulation on mineral substances. The

highest levels are observed in the unprocessed, dried seaweeds such

as kelp.

1. T. II. Maugh II, Science 199 , 413 (1978).

2. W. E. Wheeler & R. R. Gitj en, U.S.D.A. Report No. ARS-NE-88, December,

1977.

atf's forensic activation analysis program

William D. Kinard

(U. S. Treasury Department, Rockville, Maryland)

Neutron Activation Analysis (NAA) still plays a valuable role in the

analysis of evidentiary materials submitted to our laboratory. The

ability to analyze materials for their trace constituents, nondestructively, is a distinct asset in those cases where the physical integrity

of the submitted evidence must be preserved for courtroom presentation.

126
SERVICE PROGRAMS

During the past year, our laboratory used NAA in the examination of 55

actual criminal cases, as well as in several on-going research projects.

The material examined by this technique consisted of hair, paint, glass,

soil, explosive residues, and bullet lead, amounting to some 151 hours

of reactor time.

The value of NAA for the examination of paint and human hair is being

critically assessed, thus prompting a concentrated effort, by our laboratory, to see whether a trace elemental profile of these materials is

of any value.

Promising analytical data has been gathered and will be the subject of a report during the coming fiscal year.

12 7
F. STAFF ROSTER

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128
STAFF ROSTER

NON-RRD NBS STAFF LOCATED AT REACTOR

Division 354

P. Cassidy

K. Eggert

T. Hobbs

F. Moore

J. Shubiak

Division 532

M. Baier

R. A. Dallatore

C. Eisenhauer

D. Gilliam

J. A. Grundl

E. McGarry

I. G. Schroder

R. Schwartz

W. Slater

V. Spiegel

Division 520

R. Deslattes

A. Henins

L. Jacobs

E. Kessler

W. Sauder

W. Schwitz

J. Snyder

Division 522

R. Dove

H. Marshall

Division 532

C . Bowman

K. Duval

1

Division 541

Division 551

D. Anderson

J. Bailey

J

.

Blackman

B. Carpenter

R. Fliming

M. Gallorini

T. Gills

C. Grabnegger

S. Harrison

J. Koslozis

R. Lindstrom

G. Lutz

J. Maples

J. Mitchell

L. Pilione

H. Rook

N. Sato

R. Zeisler

GUEST WORKERS AND COLLABORATORS

J. Kelly

T. Madey

Division 544

S. Greer

Division 550

D. Sweger

Division 553

R. Bowen

C. Han

M. Mathew

Division 562

B. Christ

Division 564

C. Bechtold

Division 565

A. Mighell

D. Minor

R. Roth

W. Thurber

129
STAFF ROSTER

Division 741

P. Brown

Office 501

H. Berger

Off'ice 506

D. Becker

Argonne National Laboratory

R. Armani

T. Brun

H. Flo tow

0. Hinks

S

.

Susman

Battelle, N. W.

W. Nicholson

Bell Laboratory

Brookhaven National Laboratory

Federal Bureau of Investigation

R. Asbery

D. B. Davies

J. Haverkost

J. W. Kilty

E. Mitchell

C. Peters

J. P. Riley

Food and Drug Administration

M. Fiedman

L. Schroeder

W. Stroube, Jr.

J . Tanner

Harry Diamond Laboratory

C. Heimbach

NASA-Langley Research Center

R. Buckingham

National Gallery of Art

B. Miller

C. Parkhurst

C. Olin

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

C. Bond

P. D' Antonio

A. Ehrlich

M. Fatemi

J . Karle

N . Koon

V. Rath

Naval Surface Weapons Center

(White Oak Laboratory)

H. Alperin

M. Lia

D. Polansky

R. Williams

Oak Ridge National Laboratory

J . Cleland

R. Westbrook

R. Young

Picatinny Arsenal

C. S. Choi

H. J. Prask

S . Trevino

130
STAFF ROSTER

Smithsonian Institution

M. Blackman

T. Chase

J

.

Mishara

S. O'Dell

J. Olin

L

.

Zacherman

U. S. Geological Survey

P. Baedecker

J. Morgan

J . J . Rowe

U. S. Treasury Department

J. M. Hoffman

W. Kinard

American University

R. Abbundi

R. A. Segnan

Colorado State University

C. E. Patton

Georgetown University

K. Barkigia

Harvard University

G. A. Ferguson

M. Lewis

Reed College

W. Parker

Royal Canadian Military Academy

L. Bennett

University of Arkansas

D. Wolfman

T. Rolnick

University of California

(Lawrence Livermore Laboratories)

J. Browne

S . Hankins

(San Diego Campus)

R. Shelton

University of Connecticut

J. Budnick

University of Chicago

E. Anders

M. Jans sens

University of Houston

H. Jo

S. Moss

University of Illinois

C. Satternthwaite

R. Standley

University of Maine

H. Patterson

University of Maryland

D. Anderson

C. Choquette

W. Cunningham

M. Failey

P. Gallagher

M. Germani

I . Gokmen

C. Gulovali

G. Kowalczyk

E. Lepel

J. Lynn

J. Muhlbaier

I . Olmez

D

.

Reamer

E. Schneider

A. Sigled

A. Small

K. Steffansoon

131
STAFF ROSTER

W. Walters

J. Weber

M Yiu

W. Zoller

University of Paris

B. Le Meindre

University of Pittsburgh

S . Sankar

W. Wallace

University of Rhode Island

S. Pickart

University of Salford (U.K.)

D. Martin

University of Wisconsin

J . Hinkley

H. Yu

Allied Chemical Corporation

G. Leibowitz

A. Maeland

B-K Dynamics

N. Chesser

Caterpillar Tractor Company

W. Evans

Fedders Air Conditioning Company

W. Simpkins

General Electric Company

F. Luborsky

J. Walter

IBM Corporation

D. Bouloin

Monsanto Research Corporation

W. Brotherton

OLDELFT Corporation

D. Bracher

132
G, Publications

COLLABORATIVE PROGRAMS

ABBUNDI, R., RHYNE, J. J., SWEGER, D. M. , and SEGNAN, R. , "Magnetic Relaxation Phenomena in Dy-Sc Alloys." (to be published).

ALPERIN, H. A., PICKART, S. J., and RHYNE, J. J., "Small Angle Neutron

Scattering From Rare-Earth-Iron Alloys." (to be published).

CASELLA, RUSSEL C, "Neutrino Scattering in a Modified GIM Model."

IL NUOVO CIMENTO, 42A, 377-369(1977).

CASELLA, RUSSEL C., "Isotopic Shifts in Complex Crystals."

Phys. Rev. B} 17(8) , 3381-86(1978).

CHOI, C. S. and PRINCE, E., "Triaminoguandinium Nitrate by Neutron

Diffraction." (to be published).

CHOI, C. S., and PRINCE, E. , "Refinement of a-Lead Azide by Neutron

Diffraction." Acta Cryst., B33, 3536-37 (1977).

GARRETT, DONALD A., "ASTM Recommended Practice for Thermal Neutron

Radiography of Materials and Components." (to be published).

GARRETT, DONALD A., "The Observation of Electrolyte Phenomena in Lithium

Iodide Pacemaker Batteries with Neutron Radiographic Interrogation."

Procedings for Reliability Technology for Cardiac Pacemaker - Symposium Three. (to be published).

GARRETT, DONALD A., "Neutron Radiography Using Electronic Imaging

Technology." Society of Photo-Optiaal Instrumentation Engineer

(1978).

GLINKA, C. J., ROWE, J. M. , LIBOWITZ, G. G. , and MAELAND, A.

"Neutron Crystal-Field Spectroscopy of CeD2.l2«" (to be published).

GLINKA, C. J., ROWE, J. M. , RUSH, J. J., RAHMAN, A., SHINHA, S. K. , and

FLOTOW, H., "Inelastic Neutron Scattering Lineshapes in PdDQ.63-"

Physieal Review B} 17(2) , 488-93(1978).

HINKLEY, J. A., HAN, C. C, MOZER, B. and YU, H. , "Chain Deformations in

Rubber.", Macromoleeules3 Vll(4), 836-38(1978).

133
PUBLICATIONS

FORESTER, D. W. , KOON, N. C, SCHELLENG, J. H. , and RHYNE, J. J., "Spin

Glass and Magnetic Blocking Transitions in Amorphous YFe2."

(to be published)

.

KOON, N. C. and RHYNE, J. J., "Crystal Field Effects on the Spin Wave

Dispersion Relations of Cubic Rare Earth-Iron Laves Phase Compounds."

Rare Earths and Actinides3 _37, 112(1978).

KOON, N. C. and RHYNE, J. J., "Excited State Spin Waves in ErFe2-"

Solid State Coram., 26_, 537(1978).

MARTIN, D. J. and RHYNE, J. J., "Re-Analysis of Dysprosium Magnetostriction,

J. Phys. Chem, 4123-26(1977).

PICKART, S. J., ALPERIN, H. A., and RHYNE, J. J., "Small Angle Magnetic

Scattering from a Dilute Amorphous Fe(Tb) Alloy." Physios Letterss 64A(3) , 337-39(1977).

PRINCE, E., and CHOI, C. S., "Ammonium Azide." Acta Crysta. } B34, 2606-

08(1978).

PRINCE, E,M WLODAWER, A., and SANTORO, A., "Flat-Cone Diffractometer

Utilizing a Linear Position-Sensitive Detector." J. Appl. Cryst. 3 11, 173-78(1978).

RHYNE, J. J., KOON, N. C, MILSTEIN, J. B., and ALPERIN, H. A., "Spin

Waves in ErFe2", Physioa B3 86-88, 149(1977).

RHYNE, J. J., SANKAR, S. G. , and WALLACE, W. E., "Sublattice Magnetization

of ErFe2-H." The Rare Earths in Modern Science and Technology.

RHYNE, J. J., FISH, G. E., SANKAR, S. G. , and WALLACE, W. E., "Magnetic

Properties of Laves Phase Rare Earth Hydrides", (to be published).

RHYNE, J., PICKART, S., and ALPERIN, H. , "Magnetic Neutron Scattering

from Amorphous TmFe2 ." J. Appl. Phys. 49(3) , 1691-92(1978).

RHYNE, J. J. and KOON, N. C, "Magnetic Excitations in HoFe2 ."

J. Appl. Phys., 49(3) , 1691-92(1978).

ROWE, J. M. and RUSH, J. J., "The Dynamics of Hydrogen in Metals."

Proc. of International Symposium on Neutron Inelastic Scattering.

(to be published)

.

ROWE, J. M., RUSH, J. J., and PRINCE, E., "Neutron Diffraction Study

of the Structure and Phase Transitions of Alkali Cyanide Crystals."

(to be published)

.

134
PUBLICATIONS

ROWE, J. M., RUSH, J. J., CHESSER, N. J., HINKS , D. L., and SUSMAN, S.,

"Neutron Scattering Study of Rotation-Translation Interactions in

(KCN) 0#2 5(KBr)o.75-" J' Chem ' Phys -> 68(9), 4320-21(1978).

ROWE, J. M. , RUSH, J. J., CHESSER, N. J., and MICHEL, K. H., "Nature

of the Phase Transition in KCN at 168 K.", Phys. Rev. Letters,

40(7) , 455-58(1978).

ROWE, J. M. , "Low-temperature Lattice Properties of PdD alloys."

Metal Phys., 8(1) , L7(1978).

ROWE, J. M., RUSH, J. J., PRINCE, E., and CHESSER, N. J., "Neutron

Scattering Studies of Crystal Dynamics and Order-Disorder Phase

Transitions in Alkali Cyanides.", Fevvoelectvies, 1_6, 107-09(1977).

RUSH, J. J. and ROWE, J. M. , "Neutron Quaiselastic Scattering Study of

ND^4" Orientational Fluctuation in g-Phase ND4Br

.", (to be published).

RUSH, J. J. and ROWE, J. M. , "Comments on 'High Temperature Theromodynamics

of Palladium-Hydrogen II. Temperature Dependence of Partialmolar

Properties of Dilute Solution in Hydrogen in the range 500-700 K."

J. Chem. Phys., 68(8), 3954(1978).

SANT0R0, A., RUSH, J. J., and MAELAND A., "Neutron Powder Diffraction

Study of Titanium-Copper Deuteride.", (to be published).

SANT0R0, A., ROTH, R. S., and MINOR, D. , "Neutron Powder Diffraction

Study of M-LiTa3 8

.", Acta. Cryst., B33, 3945-47(1977).

SHORTEN, F. J., "NBS Reactor:A Summary of Activities, July 1976 to June

1977," NBS Technical Note 969, (1978).

STEENBERGER, C. and RUSH, J. J., "Neutron Scattering Study of Rotational

Dynamics in Dimethyltin Difluoride. ", (to be published).

TAYLOR, A., CARPENTER, F. C, and Wlodawer, A., "Leucine Aminopeptidase

(Bovine Lens): An Electron Microscopic Study.", (to be published).

WLODAWER, A., ROBERTS, J., and HOLCENBERG, J. S., "Characterization of

Crystals of L-Glutaminase-Asparaginase from Acinetobacter

Glutaminasificans and Pseudeomonas 7A .", J. Mol. Biol., 112, 515-

19(1977).

135
PUBLICATIONS

INDEPENDENT PROGRAMS

BOYER, W., TANNER, T. , and GAJAN, J., "Multielement Analytical Techniques

at the Food and Drug Administration," American Laboratory3 10,

51-65 (1978)

.

BOWEN, R. L., McCLENDON, L. T., and GILLS, T. E., "Adhesive Bonding

of Various Materials to Hard Tooth Tissues XV: Sorption of

Moldant Ions Evaluated by Neutron Activation Analysis, Journal

of Dental Research^ (1977).

CAPAR, G., TANNER, T., FRIEDMAN, H., and BOYER, W. , "Multielement

Analysis of Animal Feed, Animal Wastes, and Sewage Sludge,"

Environmental Soienoe and Technology} (to be published)

.

CARPENTER, B. S., SAMUEL, D. , WASSERMAN, I., AND YUWILER, A., The 17

(n,a) C Reation as a Tool for Determining the Location and Rate

of Turnover of Monoamines in the Brain", (to be published).

CARPENTER, B. S., D'AGOSTINO, M.D. and YULE, H. P., Editors, "Computers

in Activation Analytical Analysis and Gamma-Ray Spectroscopy",

(to be published)

.

CARPENTER, B. S., "Determination of Thermal Neutron Fux for Fission

Track Geochronology", Geological Survey Open-File Report 78-701,

p. 60, (1978).

CARPENTER, B. S. and REIMER, G. M. , "Uranium Analysis of Natural Waters

by Fission Tracks", ANS Transactions3 26, p. 172, (1977).

CARPENTER, B. S., "Mapping and Detecting Selective Elements by Nuclear

Track Techniques", Proc. of the Nuclear Methods in Environmental

and Energy Conference3 (1977)

.

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", J. Radional. Chem. 3 Vol. 37, p. 523 (1977).

High Energy Heavy Ion Induced X-Ray Emission Analysis.

J.B. Cross, R. Zeisler, E.A. Schweikert, Nucl. Instrum. Meth. 142 , 111

(1977).

FRIEDMAN, M. H. , and TANNER, T., "A Computer Language for Reducing

Activation Analysis Data," Journal of Radioanalytical Chemistry;, (1978).

136
PUBLICATION

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, p. 163, (1977).

GALLORINI, M., GREENBERG, R. R. , and GILLS, T. E. , "Simultaneous

Determination of Arsenic, Antimony, Cadmium, Chromium, Copper and

Selenium in Environmental Material by Radiochemical Neutron

Activation Analysis", Anal. Chem. , Vol. 50, No. 11, p. 1479, 1978.

GILLS, T. E., GALLORINI, M. and GREENBERG, R. R. , "The Measurement of

Selected Toxic Elements in Biological Matrices Using Radiochemical

Activation Analysis", Proa, of the Third International Conference

on Nuclear Methods in Environmental and Energy Research, (1977)

.

GILLS, T. E., GALLORINI, M. , and GREENBERG, R. R. , "The Measurement of

Selected Toxic Elements in Biological Matrices Using Radiochemical

Activation Analysis", Proc, 3rd International Conferernce on Nuclear

Methods in Environmental and Energy Research, (to be published)

.

GILLS, T. E., GALLORINI, M. , "The Determination of Trace Elements in New

Food Grain SRM's Using Neutron Activation Analysis, (to be published).

GREENBERG, R. R. , GALLORINI, M. , and GILLS, T. E., "Cadmium Analysis

by Radiochemical Neutron Activation Analysis", (to be published).

NEUENDORF, D. W. , and YOST, K. J., "Composition of Particles Emitted

from the Nicosia Municipal Incinerator", (to be published).

GREENBERG, R. R. , ZOLLER, W. H., and GORDON, G. E., "Composition and

Size Distribution of Particles Released in Refuse Inceneration",

Environmental Science & Technology, 12, p. 566, (1978).

GREENBERG, R. R. , GALLORINI, M. and GILLS, T. E., "Cadmium Analysis by

Radiochemical Neutron Activation Analysis", Proc. of Environmental

Health Perspectives (1978)

.

GALLORINI, M., GREENBERG, R. R. , and GILLS, T. E., "Simultaneous Determination of Arsenic, Antimony, Cadmium, Chronium, Copper, and

Selenium in Environmental Material by Radiochemical Neutron

Activation Analysis", Anal. Chem., 50, 11, pp. 1479-1481, (1978).

GREENBERG, R. R. , ZOLLER, W. H., and GORDON, G. E., "The Contribution of

Refuse Incineration to Urban Aerosols", Proc, 4th Joint Conference

on Sensing of Environmental Pollutants, (1977)

.

137
PUBLICATIONS

KAMPS, L., TROTTER, J., YOUNG, S., CARSON, J., ROACH, A. G. , SPHON, A.,

TANNER, T., McMAHON, B., "Polychlorinated Quadraphenyls Identified

in Rice Oil Associated with Japanese Yusho Poisoning," Bulletin of

Environmental Contamination and Toxicology, (to be published).

KESSLER, E. G. , Jr., DESLATTES , R. D., and HENINS , A., "Wavelength of

the WKotj X-Ray Line", (to be published) .

KESSLER, E. G., Jr., DESLATTES, R. D.. HENIS, A., and SAUDER, W. C,

"Redetermination of Au and In y~Ray Standards Between 0.1

and 1.0 MeV", Phys. Rev. Lett. 40, 171 (1978).

LINDSTROM, R. M. , HARRISON, S. H. , and HARRIS, J., "Accurate Calibration

of Gold Film Standards by Neutron Activation and Gravimetry,

(to be published)

.

LINDSTROM, R. M. , and FLEMING, R. F., "Optimized Measurement of Aluminum

in High-Purity Silicon," Proo. 3rd Int. Conf. Nucl. Methods in

Env. and Energy Res. 3 (to be published).

LINDSTROM, R. M. , "Radial Efficiency Gradients in Ge(Li) Gamma Detectors,"

Radioanal., Chem. 39, 153-161 (1977).

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).

TANNER, T., and FRIEDMAN, H. , "Neutron Activation Analysis for Trace

Elements in Foods," Journal of Radioanalytioal Chemistry_, 37 , 529-538 (1977).

MCGINLEY, J. R. , STOCK, G. J., SCHWEIKERT, E. A., CROSS, J. B., ZEISLER,

R. , and ZIKOVSKY, L., "Nuclear and Atomic Activation with Heavy

Ion Beams." J. Radional. Chem. 3 43, 559 (1978).

MOODY, J. R. , and LINDSTROM, R. M. , "Selection and Cleaning of Containers

for Storage of Trace Element Samples, Anal. Chem. 3 49_, 2264-2267

(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," J. of the Eleotroehemioal

Society3 125, 654 (1978).

WAGNER, G. A. and CARPENTER, B. S., "Liquid Nitrogen Enhancement of

Partially Annealed Fission Tracks in Glass", Nature3 267, p. 182,

(1977).

138
PUBLICATIONS

WAINERDI, R. E., ZEISLER, R. , SCHWEIKERT, E. A.. "Activation Analysis

Opportunities Using a 5 • 10 to 5 • 10 n/sec 14 MeV Generator."

J. Radioanal. Chem. 3 37, 307 (1977).

ZEISLER, R., LUX, F., SEIDENBERGER, H. , SCHONENBERGER, H., BECK, W.,

"Studies on the Distribution of Platinum in Tumor-Bearing Rats

After the Application of Platinum Coordination Complexes Used in

Cancer Chemotherapy", Proa. Internation Symposium on Nuclear

Activation Techniques in the Life Sciences, (to be published)

.

fr US. GOVERNMENT PRINTING OFFICE : 1979 O—281-067 (129)

139
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN 9952. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE 5. Publication Date May 1979

AtiS REACTOR: Summary of Activities

July 1977 to June 1978

6. Performing Organization Code

7. AUTHOR(S)

Frederick J. Snorten

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 /77 t.n 6/ 3 0/ 78

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less (actual summary of most significant 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 1977 through June 1978. The programs range from

the use of neutron beams to study the structure and dynamics of materials through

nuclear physics ana neutron standards to sample irradiations for activation analys

isotope production, radiation effects studies, neutron radiography and nondestruct

evaluations.

is,

ive

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 QQ Unlimited

I | For Official Distribution. Do Not Release to NTIS a Order From Sup. of Doc, U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003- 02070-2

I | Order From National Technical Information Service (NTIS), Springfield, VA. 22161

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF

PRINTED PAGES

147

22. Price $4.50

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of the National Bureau of Standards reports NBS research and development in those disciplines of the physical and

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include physics, chemistry, engineering, mathematics, and

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the basic technology underlying standardization. Also in- cluded from time to time are survey articles on topics closely

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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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highlights and reviews such issues as energy research, fire protection, building technology, metric conversion, pollution

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publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies.

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chemists, biologists, mathematicians, computer programmers,

and others engaged in scientific and technical work.

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materials, compiled from the world's literature 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.

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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.

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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 F1PS 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 Title 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

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issued quarterly. Annual subscription: $30.00. Send subscription orders and remittances for the preceding bibliographic

services to National Bureau of Standards, Cryogenic Data

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