NBS TECHN

National Bi

jjfcrary, E-01 j 3 MAY 7 1969 458

Activation Analysis

Section:

Summary of Activities

July 1967 to June 1968

II

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U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

NBS TECHNICAL NOTE 458

ISSUED MARCH 1969

Activation Analysis

Section:

Summary of Activities

July 1967 to June 1968

Edited by Philip D. LaFleur

Activation Analysis Section

Analytical Chemistry Division

Institute for Materials Research

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C, 20402 - Price $1

FOREWORD

The Analytical Chemistry Division was established as a separate division at the National Bureau of Standards on

September 1, 1963 s and became part of the Institute for

Materials Research in the February 1, 1964, reorganization.

It consists at present of nine sections and about 100 technical personnel encompassing some 57 different analytical

competences from activation analysis and atomic absorption to

vacuum fusion and x-ray spectroscopy. These competences, and

in turn the sections which they comprise, are charged with

research at the forefront of analysis as well as awareness of

the practical sample, be it standard reference material or

service analysis. In addition it is their responsibility to

inform others of their efforts

Formal publication in scientific periodicals is a highly

important output of our laboratories. In addition, however,

it has been our experience that informal, annual summaries of

progress describing efforts of the past year can be very valuable in disseminating information about our programs. A word

is perhaps in order about the philosophy of these yearly

progress reports. In any research program a large amount of

information is obtained and techniques developed which never

find their way into the literature. This includes the

"negative results" which are so disappointing and unspectacular but which can often save others considerable work. Of

importance also are the numerous small items which are often

explored in a few days and which are not important enough to

warrant publication—yet can be of great interest and use to

specialists in a given area. Finally there are the experimental techniques and procedures, the designs and modifications

of equipment, etc., which often require months to perfect and

yet all too often must be covered in only a line or two of a journal article.

iii
Thus our progress reports endeavor to present this information which we have struggled to obtain and which we feel

might be of some help to others. Certain areas which it

appears will not be treated fully in regular publications are

considered in some detail here. Other results which are

being written up for publication in the journal literature

are covered in a much more abbreviated form.

At the National Bureau of Standards publications such as these fit logically into the category of a Technical Note.

We have now issued these summaries for all of our sections.

The following is the second annual report on progress of

the Activation Analysis Section.

W. Wayne Meinke, Chief

Analytical Chemistry Division

IV
PREFACE

During the period covered by this progress report the

separation between the Radiochemical Analysis Section and

the Activation Analysis Section became complete by the

appointment of different Section Chiefs for each section.

The Activation Analysis Section has the responsibility

to develop and apply measurement techniques for the quantitative and qualitative analysis of materials through the

use of nuclear reactions.

The basic activities of the Section may be divided

into two general areas, the research and development area

and the sample area. The section has a very real responsibility for the development of new techniques, and the

refinement of existing techniques, to increase the applicability of activation analysis and to reduce the cost of

analysis to become more competitive with non-nuclear methods

of analysis

A very important part of the Section's activities is

involved in the certification of Standard Reference Materials

in cooperation with the other sections in the Analytical

Chemistry Division. The Office of Standard Reference

Materials of the National Bureau of Standards is currently

developing, or has issued, Standard Reference Materials of

very high purity which are well characterized for their trace

element content. The Activation Analysis Section has made

a significant contribution in the certification of these

standard materials.

Activation analysis is particularly suited for the

analysis of trace and ultra-trace components of materials

because of the high inherent accuracy, the very high sensitivity for many elements, the lack of a reagent "blank" in

most analyses, and the fact that there are few sources of

systematic error associated with the technique that are

difficult to evaluate.

v
During this past year, the Section has become more

involved with the application of activation analysis in biological and medical problem areas, and the first steps of

what is hoped will be a fruitful relationship with the

National Institutes of Health, especially The National

Institute of Arthritis and Metabolic Disease, have begun.

In connection with these problems, the Section has taken a leading role in the development of Standard Reference

Materials for application to analytical problems in medicine

and horticulture. Standards of botanical material and

freeze-dried blood serum, which are carefully characterized

for their trace element content, are being developed now,

and a Standard of freeze-dried tissue (liver) will be

developed in the near future.

The Activation Analysis Section is composed of three

groups that are oriented to a specific source of nuclear

radiation; the reactor, LINAC , and Cockcroft-Walton generator groups, and a fourth group for the development of radiochemical separations. This method of division serves the

administrative needs. More important is the fact that considerable interaction among the groups is encouraged so

that activities of common interest are worked upon jointly

in the several groups. In addition, the Radiochemical

Analysis Section retains groups in nuclear instrumentation

and nuclear chemistry which consult both sections.

A roster of the groups in the Section is listed in

Part 8. In the past the Section has enjoyed the presence

of scientists from abroad, and from within the United States,

who have worked for one to two years in the Section, and have

contributed to a very stimulating environment. It is hoped

that we may continue to utilize this program in the future.

In order to specify adequately procedures, it has been

necessary occasionally to identify commercial materials and

equipment in this report. In no case does such identification

VI
imply recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the material or equipment

identified is necessarily the best available for the purpose.

Philip D. LaPleur, Chief

Activation Analysis Section

Analytical Chemistry Division

Vll
TABLE OP CONTENTS

Page

1. INTRODUCTION 1

2. LIAISON AND GENERAL FACILITIES 4

A. Liaison 4

B. General Facilities 4

C. Pneumatic Tube System 5

1. Sample Vehicle (Rabbit) 7

2. Instrumentation 8

3. ACTIVATION ANALYSIS WITH 14-MeV NEUTRONS .... 9

A. Introduction 9

B. Status of the 14-MeV Neutron Activation

Facility 10

1. Installation of High Flux Neutron

Generator 10

2. Biological Shield 11

3. Pneumatic Transfer System 12

4. Detector Assembly 15

5

.

Sequence Programmer 16

6. Photo-electric Trigger Circuit 18

C. Research Activities 18

1. Dual Sample-Biaxial Rotating Assembly . . 18

2. Evaluation of Systematic Errors 19

3. Self-Absorption Corrections in GammaRay Photopeak Analysis 20

4. Analysis of Photographic Emulsions. ... 22

5. Blank Problems in the Analysis of Trace . Oxygen ' 24

D. Role of 14-MeV Neutrons in the Activation

Analysis of Standard Reference Materials. . . 26

1. Determination of Oxygen in Ferrous and

Non-ferrous Metals 26

2. Analysis of Organometallic Compounds. . . 30

3. Analysis of Silicon 30

4. ACTIVATION ANALYSIS WITH THE NUCLEAR REACTOR . '. 31

A. Introduction 31

B. Research Activities 31

1. Group Separations for the Activation

Analysis of Steels 31

2. Determination of Impurities in High Purity

Zinc by Neutron Activation Analysis. . . 32

3. Determination of Molybdenum by Activation

Analysis - 34

viii
TABLE OF CONTENTS (cont.)

Page

C. Analysis of Standard Reference Materials ... 37

1. Activation Analysis of Copper and Nickel

in Clay Standard Reference Materials ... 37

2. Determinations of Gold in SRM Platinum . . 40

3. Nondestructive Determination of Manganese

and Vanadium in Iron and Steel Standard

Reference Materials 5k, 5& s 6g, lOle,

lOlf, 101g, 196 and 342a 41

4. Analysis for Cobalt in Lithium-Boron-10

Glass Using a Pre-dissolution Technique. . 44

5. Copper and Arsenic in SRM Cast Iron

Samples 46

6. The Determination of Cu and Sb in Solder . 48

7. Activation Analysis of SRM Urea, Creatine

and Uric Acid 49

8. Determination of the Homogeneity of SRM

Clays Nos . 97a and 98a Analyses for

Sodium and Scandium 50

D. Service Analyses 51

1. Nondestructive Neutron Activation

Analysis of Impurities in Several Quartz

Samples with a Lithium-Drifted Germanium

Semiconductor Detector 51

2. Nondestructive Analysis for Silver,

Chlorine, Bromine, Sodium, and Potassium

in Quartz 54

3. Analysis of Nickel and Manganese in

Standard Asbestos Samples 56

4. The Determination of Copper in Serum and

Urine 58

5. Preparation of DN0~ for the NBS Reactor. . 60

ACTIVATION ANALYSIS WITH THE NBS LINAC 62

A. Introduction 62

B. Facilities 62

C. Carbon and Oxygen in Sodium 63

D. Matrix Effect 64

E. Sensitivities in Photon Activation Analysis. . 65

F. Carbon in Sulfur 66

G. Yttrium in Rare Earths 68

EXTRACTION OF METALS BY BIS ( 2-ETHYLHEXYL)

ORTHOPHOSPHORIC ACID 70

ACTIVATION ANALYSIS LITERATURE SEARCHING FILE. . . 78

ix
TABLE OP CONTENTS (cont.)

9

10

PERSONNEL AND ACTIVITIES

A. Personnel Listing

B. Publications '.

. . C. List of Talks

ACKNOWLEDGMENTS

REFERENCES

APPENDIX 1: Sequencing Action of Programmer

APPENDIX 2: Keys for Computer Literature

Searching

LIST OP FIGURES

Figure

1. Terminal locations of new pneumatic tube

systems

Sample carriers for use in the NBSR '.

. 2.4 mA neutron generator

6

7

8

9

10

11

12

13

14

15

Pulse height analyzer and sequence programmer

with associated electronics and neutron

generator operating console

Plan view showing modification to existing

biological shield. A=top view, A-A=side

view

Cutaway drawing showing the location of the

neutron generator in the biological shield.

Schematic of pneumatic tube transfer system

Inside view of detector shield

Circuit diagram of sequence programmer. . . Photoelectronic trigger circuit

Gamma ray attenuation factor calibration

curve

Flow-through capsule

Flow sheet for group separations from iron

steel matrices

Flow sheet for group separations from a zinc

matrix

Separatory funnels modified with screw-top

closures

Page

80

80

81

81

83

84

86

89

Page

5

7

11

12

13

14

15

16

17

18

21

25

32

33

36
LIST OP FIGURES (cont.)

Figure Page

16. Photograph of electron beam from LINAC

striking fluorescent screen 62

17- Normalized results of sensitivity

calculations shown with experimental results

of Oka et al 67

18. Plot of log Kd as a function of HC10,

concentration 71

19. Plot of log Kd as a function of HNO^

concentration 72

20. Plot of log Kd as a function of HC1

concentration 73

21. Plot of log Kd as a function of acid

concentration for the lanthanides . 74

22. Plot of log Kd for molybdenum as a function

of HDEHP concentration 75

23. Extraction of HCIO^ HNO and HC1 by HDEHP . . 77

24. Typical readout of computer literature search . 79

LIST OF TABLES

Table

1. Analysis of oxygen in ferrous and nonferrous materials 28

2. Analysis of organometallic compounds 29

3. Results of molybdenum analyses 37

4. Copper and nickel in SRM clays 39

5. Gold in SRM 68l (platinum) 40

6. Information on samples analyzed 4l

7. Manganese and vanadium in SRM cast iron

samples 43

8. Copper and arsenic content of SRM cast iron

samples 47

9. Copper and antimony content of SRM 127b

(solder) 49

10. Results of homogeneity studies of SRM clay

#97a. .• 52

XI
LIST OP TABLES (cont.)

Table p age

11. Results of homogeneity studies of SRM Clay

#98a

12. Impurities in quartz samples

13. Nickel content of asbestos samples

14

.

Manganese results on asbestos samples

15. Copper content of human serum and urine ....

16. Carbon content in intermediate purity sulfur. . 17. Comparison of sensitivities for yttrium using

various detector systems 69

53

55

57

58

59

68

Xll
ACTIVATION ANALYSIS: COCKCROFT-WALTON GENERATOR, NUCLEAR

REACTOR, LINAC

July 1967 through June 1968

Edited by Philip D. LaPleur

ABSTRACT

The facilities used by the reactor, LINAC and neutron

generator groups for activation analysis are described.

Proposed installation of four new irradiation terminals and

a new pneumatic transfer tube system are outlined.

A new 2.5-mA neutron generator has been installed and

the biological shield, pneumatic transfer system and the

detector assembly modified. Studies of blank problems for

oxygen determination and self-absorption corrections in

photopeak analysis have resulted in greatly improved precision for Standard Reference Materials. Halide in photographic emulsions, using 14-MeV and 2.6-MeV neutrons, have

been determined.

Considerable emphasis has been placed on the development of group radiochemical separations, SRM steel and

high purity zinc samples have been analyzed using this technique .Eighteen different SRMs were analyzed for a variety of

elements and a variety of service analyses were performed.

The self-absorption effects of the matrix on irradiation

photons were studied and calculations of sensitivities 1 for

photon activation analysis were made. Carbon in sulfur,

yttrium in rare earth oxides and oxygen in sodium were determined by photon activation.

The extraction of metals by bis (2-ethylhexyl) orthophosphoric acid has been studied, and distribution coefficients are given for many of the transition metals. The

results Indicate enhanced applicability of this reagent for

radiochemical separations.

Updated keys for computer literature searching and a sample output are included.

xiii
KEY WORDS:

Activation analysis, Cockcroft-Walton neutron generator,

computer literature searching, extraction, group separations,

homogeneity testing, hydrogen bis (2-ethylhexyl) phosphate,

matrix effect, molybdenum, NBS LINAC, NBS reactor, photon

activation analysis sensitivities, Standard Reference Materials, zinc.

xiv
1. INTRODUCTION

During the past year the activation analysis technique

has become more and more important in the certification of

Standard Reference Materials (SRM) . The number of elements

which we are capable of analyzing without significant developmental work has increased markedly during this year. The

capability of all of the projects has been greatly extended

during this time.

As mentioned in last year's report, one of the most

serious limitations of the activation analysis technique is in

the difficulty in approaching the rapid multi-element analytical capability that is characteristic of emission spectroscopy

or spark-source mass spectrometry. Past efforts at survey

type analyses have been made with the use of nondestructive

techniques and computer resolution of the complex gamma-ray

spectra that result. This technique has been only moderately

successful and has, in several cases, led to serious questioning of the value of nuclear activation analysis.

We are attempting to achieve the multi-element analysis

capability through the application of group radiochemical

separations as outlined below.

Except in unusual circumstances, e.g. high accuracy at

trace concentration levels, we do not believe that activation

analysis is apropos for survey analyses, especially qualitative, since emission and spark-source mass spectrometry

are much more versatile for this purpose.

With the advent of high resolution solid state gamma

ray detectors, many people have felt that radiochemical

separations were no longer needed in activation analysis,

that all analyses could be performed using instrumental

techniques and computer data reduction. Our philosophy is

to use nondestructive activation analysis whenever it is

feasible and whenever it gives high accuracy and precision.

In cases where nondestructive analysis meeting these criteria
is not possible, we believe very strongly in the utilization

of radiochemical separations.

Because stable carriers can be added prior to radiochemical separations, some workers have employed sloppy chemical

techniques using the excuse that "I can always determine the

yield later." Often these yields are determined using precipitates, etc., which are poorly characterized. The resulting

poor precision of analysis has led some workers in the field

of activation analysis to blame chemistry for this lack of

precision and to devote themselves wholly to instrumental

analysis. It is also more expensive to do activation analysis

when yield determinations are necessary, since you are essentially analyzing the sample twice. When adequate separations

are not available in the literature, we strive to develop

separations which are rapid, give very high yields, preferably

quantitative, and are as simple as possible. There is no

substitute for good chemistry!

The ideal technique is the marriage between nondestructive analysis and analysis with chemical separations. This

technique may be referred to as the group separations method

in which groups of elements, 1 to 4 or more, are separated

together. These groups generally can be resolved readily

using high resolution gamma-ray spectrometry. It is this

technique, group radiochemical separations, that is receiving

the greatest emphasis within the radiochemical separations

project

.

As always, the evaluation of systematic and random errors

has been paramount in the efforts of all the projects in the

section. The installation of a new neutron generator having

a vastly improved neutron flux level has enabled the analysis

of macro constituents in metallo-organics and of oxygen in

metals with precisions approximating those of non-nuclear

techniques. Using this new generator facility, the studies

of the evaluation of systematic errors resulting from
self-absorption and degradation of neutrons during irradiation

and of gamma rays during counting, have been completed. This

technique allows extrapolation of correction factors between

matrices and has been instrumental in allowing analysis of

metallic elements in metallo-organics to be performed.

The National Bureau of Standards Reactor (NBSR) achieved

criticality in December of 1967, but low power start-up tests

are still continuing. It is anticipated at this time that

operation in excess of 100 KW will occur in October of 1968

enabling the reactor neutron activation analysis project to

utilize the reactor here at the Bureau of Standards rather

than having irradiations performed at other reactor centers.

In spite of this handicap the reactor neutron activation

project has been very fruitful in terms of number of analyses

performed during this year.

The photonuclear analysis project has continued to operate

whenever time was available at the LINAC . During this year

the work on the analysis of carbon in sodium metal has been

completed and another project, also of great interest in the

fast-breeder reactor program, that of the determination of

oxygen in sodium metal, using the 0(y,n) reaction has

also been completed. There has been no change In the LINAC

operating schedule and we are still irradiating approximately

one day a week for an eight hour irradiation period. All

laboratory facilities in the reactor building, with the

exception of the new pneumatic tube facilities, have been

completed and we now do all work, with the exception of reactor

irradiations, here at the National Bureau of Standards.
2. LIAISON AND GENERAL FACILITIES

A. Liaison

Although the NBS Reactor achieved criticality in December

1967, usable power levels are not yet available for experiments. Because of this, the use of the NBSR facilities for

activation analysis by scientists outside the Bureau has not

yet been realized.

B. General Facilities

The start-up of the NBS reactor in December, 1967, created

a need for efforts in the design and installation of new

multi-routing pneumatic transfer systems, suitable handling

facilities for highly radioactive samples and for the preparation of irradiation guides for the experimenter. A major

proportion of this work has been completed. Subject to final

approval by the Hazards Committee, these facilities should

be made available during fiscal year 1969.

All of the facilities in the laboratory wing of the NBSR

have been completed, with the exception of the pneumatic tube

facilities discussed below, and are now in daily use by the

personnel of the Section. We are, in addition, still using

the irradiation facilities of the NBS LINAC and other reactors,

especially the Naval Research Laboratory Reactor.

Efforts have also been expended on the design of a small

hot-cell facility in which up to 50 curies of 1 MeV gammaray activity can be handled safely. This facility is expected to have .the provision for remote handling of the sample

for rapid decontamination of the sample from undesirable

matrix activity.

An exhaustive draft covering regulations for irradiations

in the NBSR has been completed. This guide includes sample

irradiation requirements for all available and planned facilities. Over 500 elements and matrices have been included.

At the present time the proposed guide is being evaluated for

possible acceptance by the Reactor Hazards Committee.

H
C . Pneumatic Tube System

At the time of construction the NBSR was equipped with a pneumatic tube system consisting of four terminal positions

in the reactor and a send/receive location for each tube located in rooms C001 and C002 (fig. 1) . The. expected flux levels

at 10 MW indicate a thermal flux 7 . 3xl0 1 ^n • cm

-2

• sec

-1

for

the tube closest to the core and a thermal flux of 3.8x10 J

n-cm

-2

-sec

-1 with a fast flux of .16x10 ]^_p_l Jn • cm -sec for

the tube farthest from the core.

Shaded Area Denotes Type of System Available at

this Location.

T-l,2,3,&4 — ll/2 in Pneumatic Tubes.

T-5 [MD Converter Tube.

T-6 Manual Facility. T-7 \"^:\ Thermal Column Tube.

T-8 £^3 Vertical Thimble Tube.

'B

m Wing Lab Area

B-152 B^7

T-3&4

T-7

T-8

T-I&2

1 B-144 B-142

1 mil

B-124 B-122 BI2I

I'

Offices

Figure 1. Terminal locations of new pneumatic tube systems
In order to expand these capabilities, 4 new irradiation

terminals are currently under construction. One of the terminals will be constructed entirely of graphite and will be

located in the thermal column of the reactor. Using a 1 1/2 in

i.d. pneumatic tube system, laboratories B-144, B-121, and C002

will have access to an essentially pure thermal neutron flux

11 -2 -1

of about 3x10 n.cm .sec

The remaining three terminals will be located in the

reactor core. Two of these will be coupled to 7/8 in. i.d.

pneumatic tubes, while access to the remaining terminal will be

manually from the top of the reactor on the control room level.

This manual irradiation facility will be used when samples

must be irradiated for a longer period of time than can be

allowed in the pneumatic tube location because of radiation

damage and heating of polyethylene rabbits. Since it is less

affected by the high levels of gamma heating and radiation

damage which are to be expected at this location the sample

containers will be made of high purity graphite. An irradiation of one reactor cycle (18 days) should produce an NVT of

20 approximately 3x10 neutrons in this irradiation facility.

The two 7/8 in. in-core facilities will consist of a vertical irradiation terminal similar to the four tubes orginally

installed, and a fast neutron convertor terminal. The fast

neutron convertor system will allow irradiation in an essenti13 -2 -1 ally pure fission spectrum flux of about 3-5x10 n.cm .sec , and will have send/receive stations located in laboratories

B-142, B-121, B-124 and C002. The flux in the vertical terminal will be much the same as the manual irradiation system,

however, it will be used for short irradiations (.probably 3

min. or less) and will serve laboratories B-142, B-144, B-147

and C001.

When the new system is completed the sample Irradiation

capability of the NBSR will have been expanded to a total of

8 irradiation positions and 22 send/receive locations which
will service 8 different laboratories within the reactor

building (fig. 1)

1. Sample Vehical (Rabbit) High density linear polyethylene sample containers will be used in the 7/8 in. system. On

special occasions, however, high purity graphite or beryllium

containers of the same configuration could be used.

The 7/8 in. and 1 1/2 in. rabbits which will be used in

the pneumatic tube system, and the graphite bucket for use

with the manual irradiation facility, are shown in figure 2.

1 \ o 1 INCH

Figure 2. Sample carriers for use in NBSR,

7
2. Instrumentation In order to monitor traffic from the

22 send/receive locations to the 8 irradiation terminals, an

instrumentation system has been developed to prevent the

insertion of more than one sample in any one tube. An interlock system also has been incorporated whereby only one sample

may be in transit at one time. This serves to prevent the

insertion, or withdrawal of several samples simultaneously.

Since many of the tubes pass through laboratories or work

areas, a visual warning system has been built which will be

activated in the event a sample becomes lodged in a tube.

The alarm will be sounded when a sample has exceeded the

preset maximum transit time from the reactor to the receiving

station.

In the event of a major scram of the reactor, or a power

failure, an emergency system has been developed, using an

independent supply of C0„ propelling gas, which will automatically return all samples in the irradiation terminals to

a central, shielded location. This system circumvents, the

possibility of samples remaining in the core and the rabbit

and/or sample container melting during a scram or power failure

(S. S. Nargolwalla, P. A. Lundgren and P. D. LaPleur)
3. ACTIVATION ANALYSIS WITH 14 MeV NEUTRONS

A. Introduction

Primary emphasis in this program has been given to research on new approaches toward the improvement of the precision and accuracy of 14 MeV neutron activation analysis.

The use of the dual sample-biaxial rotating sample assembly

has improved precision by neutron flux homogenization,

especially in oxygen analyses, by about a factor of ten better

than by other normalization techniques. The NBS system gives

results limited in precision chiefly by counting statistics

and permits the analyst to determine both neutron and gammaray attenuation in dense samples. An outline is given of

the careful studies which substantiated the expected exponential dependence of the attenuation correction factor on

the calculated attenuation coefficient difference between the

sample and the standard. Empirically determined calibration

curves as a function of sample diameter can be used to predict attenuation correction factors for oxygen in other matrices than steel.

The more general case of analyses for elements other

than oxygen, in which gamma rays of less than 4.8 MeV result

from nuclear level transitions or positron annihilations, was

also the subject of a detailed research study. Such factors

as reaction threshold effects on neutron attenuation and

photon energy dependency on attenuation correction factors

were evaluated.

Since capsule blanks can cause major difficulties in the

determination of trace amounts of oxygen, a method for precisely establishing the capsule contribution was developed.

This method corrects for the geometrical configuration of the

sample within the capsule. Experimental results are in good

agreement with theory.
A highly promising research study was also made on the

determination of halogens in a silver bromide matrix in photographic emulsions. Since a knowledge of chloride and iodide

composition is essential to the evaluation of the primary

light-sensitive properties of such emulsions, rapid and accurate methods were needed. It was found that accurate chloride

analyses could be made with a relative standard error of 1%

at the 200 mg level. The use of 2.8 MeV neutrons produced

2 2 3 by the H( H,n) He reaction, which eliminated undesirable

radioisotopes induced above this reaction threshold, allowed

the accurate determination of iodine to 1% relative standard

error at the 420 mg level.

By the use of a new high flux neutron generator (2.5mA

maximum output) plus improvements in shielding, pneumatic

tube system and detector, analyses of Standard Reference

Materials have been possible with higher orders of precision

and accuracy. The elements nitrogen, fluorine, magnesium,

silicon, phosphorus, cobalt and silver have been determined

(singly) in thirty Standard Reference Materials. Some of

the more interesting analyses will be described.

(S. S. Nargolwalla)

B. Status of the 14 MeV Neutron Activation Facility

1. Installation of High Flux Neutron Generator

The flux limitation of the old facility has been eliminated by the installation of a new high flux neutron generator rated at 2.5 mA maximum deuteron beam output, and capable

of accelerating monoatomic deuterons up to 200 keV. A gain of

about a factor of ten in flux has been realized. The neutron

generator, shown in figure 3 is operated from outside the

biological shield. The operating console and other equipment

are shown in figure 4. Aside from the flux, the new machine

differs from the older model in that the design of the tritium

target holder includes Freon cooling instead of water and is

replaceable for rapid and safe target changes. The generator

10
Figure 3. 2.5 mA neutron generator

also has beam focusing capability and a remote mechanical

deuterium leak. The beam stability of this accelerator is

comparable to the 500 yA machine previously used [1].

(S. S. Nargolwalla and J. E. Suddueth)

2 . Biological Shield

In order to house the new high-flux machine, the existing

biological shield had to be modified considerably. A general

layout (fig. 5) and the cut-a-way drawing (fig. 6) indicate

the extent of the modifications in terms of additional high

density (180 lb/ft ) shielding and the construction of a small target room. A closed-circuit T.V. camera can be accom11
HKSB

.*•.;

Figure 4. Pulse height analyzer and sequence programmer

with associated electronics and neutron generator

operating console.

modated in the target room to view the beam for alignment „ purposes. Preliminary dose measurements made by the Health

Physics unit indicate that the shielding of the new structure

is equivalent to that of the previous shield for a flux ten

times greater than obtained with the 500 uA generator.

(J. E. Suddueth and S. S. Nargolwalla)

3. Pneumatic Transfer System

To accommodate the location of the accelerator with respect

to the modified biological shield, the pneumatic tube system

had to be redesigned. An improved high-speed transfer facil12
Experimental

Well

Rotating

Target Assembly

3" Standard —

I Beams

15 kV dc Focus Power Supply

— 10'

- 32"

200 kV.dc Main

Power Supply

Existing Shield

Increased Shielding , of 180 lb/ft

3

V7777A Concrete to Accomodate 2.5 mA

Generator.

12-8"

—8-3"

—7'

"A -A'

Figure 5. Plan view showing modification to existing

biological shield. A=top view, A-A=side view.

ity constructed from 3/4 in. i.d., 1/8 in. wall polyethylene

tubing was installed. More efficient air-operated routing

switches at the loading and sample-routing stations insured

a completely closed system, ideal for trace oxygen determinations in which the propelling gas is nitrogen. The arrester

pin and sample spinning assemblies described previously [2]

have been eliminated. Reproducible sample placement between

the two scintillation detectors is achieved through closetolerance design of the sample receiver. A schematic diagram

showing the general layout of the pneumatic tube facility is

illustrated in figure 7

(J. E. Suddueth and S. S. Nargolwalla)

13
15 kV Focus

Power Supply

Safety Door

200 kV Main

Power Supply

I l Existing Shield

E57H Increased Shielding

(180 lb/ft 3 Concrete)

Figure 6. Cutaway drawing showing the location of the

neutron generator in the biological shield.

14
SAMPLE IN SIGNAL (PRESSURE SWITCH)

SEND/RECEIVE SIGNAL

RESET

PRE AMP

BLEED N, SUPPLY

N

2 SUPPLY (SEND)

Figure 7- Schematic of pneumatic tube transfer system.

4 . Detector Assembly

Two 4 in. x 3 in. Nal(Tl) scintillation detectors, each

mounted on a 5-in diameter photomultiplier tube, form the

basis of the detection system. These detectors are matched

for gain, gain-shift and resolution to within 0.25% of one

another. In our earlier work [2] it was found that the detector shield was slightly underdesigned with respect to neutron

shielding, and activation of the detectors was observed.

The new shield is located 12 ft further from the neutron

source and the concrete and paraffin layers were doubled in

thickness. Little or no activation of the detectors has been

15
observed. The locations of the detectors inside the shield

showing the sample receiver are illustrated in figure 8.

(J. E. Suddueth and S. S. Nargolwalla)

Figure 8. Inside view of detector shield.

5. Sequence Programmer

Major modifications in the earlier unit were made in order

to adapt the apparatus to the new sequence of operations.

The new experimental sequence can be followed with the aid of

the schematic diagram shown in figure 7 and the circuit diagram illustrated in figure 9. The basic principle of sequencing action is identical to that described previously [2]. A

step-by-step description of the individual operations is given

in appendix 1.

(P. C. Ruegg and M. Stalbird, Radiochemical Analysis

Section, J. E. Suddueth and S. S. Nargolwalla)

16
j\i i\i i\in

CD

UW

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o

£

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17
6 . Photo-electric Trigger Circuit

This trigger circuit (fig. 10) is used to sense the capsules as they pass through the pneumatic transfer system.

When a capsule interrupts the light beam, the photocell resistance becomes large and transistor T-l is driven into its "on"

state. The tunnel diode D-l, which is used as a discriminator,

turns transistor T-2 off which produces a fast positive pulse.

This pulse is used to trigger a monostable described previously

[2] which activates a relay.

(F. C. Ruegg, Radiochemical Analysis Section)

12V.

o *\

50 K/

ii 412V

+ I2V

o

CL-3

Tl

K

2N3565/pC~ 6.8K

IN37I2

01

2NI306

MONOSTABLE

Figure 10. Photoelectronic trigger circuit.

C . Research Activities

1. Dual Sample-Biaxial Rotating Assembly

The high degree of precision obtained as a result of flux

homogenization by the dual sample-biaxial rotating sample

assembly has indicated the absolute need for such devices [3]

for meaningful analysis using 14 MeV neutrons. We have realized that neutron flux perturbation is the most important

factor affecting reproducibility, since beam control is very

limited. For this reason, most normalization procedures lead

18
to either ambiguous or incorrect analyses. Beam jitter or

beam wander is particularly undesirable when short-lived

species are being produced; the determination of oxygen by

the 0(n,p) N reaction is a prime example. The dual samplebiaxial rotation is achieved by a special gear mechanism.

This assembly allows reproducible placement, as determined by

irradiating and counting carefully prepared identical capsules

of benzoic acid, and permits both sample and standard to be

exposed to an identical neutron flux as a result of biaxial

rotation. An optimum rotation speed was determined and target

displacements of one-half inch in all directions were found

to have negligible effect. By the use of standard statistical procedures, it was found that the analytical precision,

which is now most- often limited by the total number of counts

accumulated, is about ten times better than that which most

normalization techniques can provide. The system permits the

analyst to determine both neutron and gamma-ray attenuation

in dense samples. This irradiation assembly is currently

being utilized for the accurate and precise determination of

oxygen and other elements in NBS Standard Reference Materials.

(S. S. Nargolwalla and F. A. Lundgren)

2 . Evaluation of Systematic Errors

The evaluation of systematic errors in the analysis for

oxygen was a major objective of further research [4] and

methods were developed whereby accurate absorption correction

factors could be experimentally determined with a high degree

of precision. In comparative 14-MeV neutron activation analysis for oxygen, the neutron and gamma-ray attenuation differences in the sample and standard introduce systematic errors.

The neutron attenuation process utilizes the concept of total

removal cross section (E„) as a more accurate measure of the

matrix attenuation of 14-MeV neutrons, while the gamma-ray

attenuation takes the usual meaning of the total linear attenuation coefficient (u ). Equations are then derived for the

19
total attenuation correction factor. The equipment used and

experimental procedure including sample selection and preparation are outlined in detail [4]. The experimentally determined correction factor for both the neutron and gamma-ray

case shows an exponential dependence on the calculated difference between the respective attenuation coefficients for

sample and standard. Within the range of sample diameters

tested, preliminary data indicate that the slope of each

calibration line is linearly dependent upon the sample diameter. For comparable diameters, the magnitude of the slope

for neutron attenuation is approximately ten times greater

than for gamma attenuation. Such calibration lines, for a given generator system, allow an experimental relationship to

be generated which will permit the evaluation of absorption

errors to give correction factors for other matrices. The

general technique can be adapted to other light elements as

well. Some typical analyses of Standard Reference Materials,

corrected for attenuation, illustrate the high degree of accuracy and precision obtained.

(S. S. Nargolwalla and M. R. Crambes)

3. Self-Absorption Corrections in Gamma-Ray Photopeak

Analysis

Success with the application of the above research prompted

us to extend the work to the general case of analysis in which

the measurement of gamma radiation is made by counting the

area under the photopeak [5]. A study was then initiated to

determine the photon self-absorption relationships for the

general case of photopeak analysis of gamma-ray energies resulting from nuclear level transition and positron annihilation.

By the judicious selection of appropriate samples and

standards, the reaction threshold effect on the previously

determined neutron attenuation correction relationship [4] and

the photon energy dependency on the attenuation correction

factor were evaluated. For positron emitters, careful sample

20
selection and preparation permitted a study of effects due

to differences in density and positron energy or both. The

experimental technique used consisted of simultaneously irradiating a sample and standard in a dual sample-biaxial rotating assembly and sequentially counting between two 4 in x 3

in Nal(Tl) scintillation detectors coupled to a 400-channel

pulse height analyzer system. This technique and the method

of data processing have been described in previous work [3, 4].

A comparison of photon attenuation correction factors as a function of the differences in the linear attenuation between

sample and standard for the three possible cases is shown in

figure 11. Under a given set of irradiation and counting conditions the slope representing the general case of photopeak analysis is independent of gamma energy and approximately

twice that of 4.8- to 8.0 MeV range used for oxygen analysis.

This is due to the reduction in efficiency for photopeak

counting when compared to counting between the 4.8- to 8.0

MeV range. Since the photon attenuation correction factors

(fjL {sid)-fu. (sample)) cm"

Figure 11. Gamma ray attenuation correction factor

calibration curve.

21
can only be determined from prior knowledge of the neutron

attenuation characteristics, it is now confirmed that neutron

attenuation is best approximated by the removal cross section

concept and thus independent of the reaction threshold. The

straight line relationship observed for positron emitters

show that the correction factor is independent of density and

positron energy differences. However, the small reduction in

the slope when compared to that obtained for the general case,

can be attributed to bremsstrahlung contribution in the photopeak region. Both of these factors would increase the efficiency of counting with corresponding reduction in the observed

photon attenuation.

The accurate determination of self-absorption systematic

errors has enhanced the applicability of 14-MeV neutrons to

the accurate and matrix-independent analysis of 0, N, P, Na,

Mg, Si, P, Co and Ag for the Standard Reference Materials

certification program.

(M. R. Crambes, S. S. Nargolwalla and J. P. Suddueth)

4 . Analysis of Photographic Pmulsions

This project involved the application of fast neutron

activation analysis of halogens to bulk photographic emulsions

Bulk emulsions consist of three major components: a silver

halide, gelatin and water. The proportions of these components vary somewhat, depending upon the use anticipated. For

example, x-ray films have a higher silver halide-to-gelatin

ratio than do fine grain microfilms.

The primary light-sensitive properties of a photographic

emulsion are determined by the composition of the silver

halide component in so far as the ratio of chloride, bromide

and iodide are concerned. For example, an emulsion containing

1 mole percent iodide and 99 mole percent bromide has much

higher sensitivity to light than a pure silver bromide emulsion or an emulsion containing chloride and bromide. Thus,

the composition of the silver halide component of an emulsion

22
establishes its basic photo-sensitive properties. Furthermore,

second-order modifications in the light-sensitive properties

can be achieved by changes in the technique of precipitation

of the silver halide and the incorporation of various other

materials which are known sensitizers or desensitizers

Therefore, there exists a strong need to have accurate

rapid methods of analysis for the halides in photographic

emulsion matrices. Present chemical and physical methods,

however, fall short of this goal. There are two methods

which are commonly used for these analyses. One is a coulometric argentometric titration of the halides which is reasonably accurate but is rather long and laborious. The method

is cumbersome because it requires removal of the silver by

zinc reduction prior to titration. The halides are separated

by differential oxidation. One operator is capable of carrying out six determinations in an eight-hour day. The method

is, however, applicable to any mixture of chloride, bromide

and iodide. The second method used is x-ray fluorescence.

This method is reasonably good for the measurement of iodide

but suffers from severe self-absorption errors when used for

bromide and chloride. The soft x-rays from these two elements

are greatly attenuated by the matrix and slight changes in

the matrix composition cause a change in the attenuation.

Fast neutron activation analysis appear to offer several

possible solutions to the problem. In general, matrix attenuation problems are considerably smaller with the higher

energy gamma rays as compared with the soft x-rays used in

the x-ray fluorescence technique. This makes activation

analysis more generally applicable. It is highly possible

that very accurate chloride analyses can be carried out

directly on emulsions, using a sodium iodide detector and irradiating the sample with 14-MeV neutrons. The determination

of bromide and iodide may require the use of the higher resolution germanium detectors since the most abundant gamma rays

are not separated sufficiently in energy for complete resolu23
tion with a sodium iodide detector. Another alternative which

could be investigated is the irradiation of the samples with

2 2 3

2.8 MeV neutrons produced by the reaction H( H,n) He. This

would eliminate some of the undesirable reactions with reaction thresholds greater than 2.8 MeV which result in complex

spectra that are difficult to resolve.

A nondestructive neutron activation technique for the

analysis of chloride and iodide in a silver bromide matrix

was developed. Chlorine was measured after activation with

57

14.7 MeV neutrons. The 3-1 MeV gamma rays from J S were

measured without interference. Calibrations were carried out

using photographic emulsions containing 10- to 200 milligrams

of chlorine. The relative standard error of a single determination at the 10 milligram level was 5%', at the 200 milligram level it approached 1% .

-i p o Iodine was measured via I produced by n,y activation

with 2.8- MeV neutrons. A straight line calibration curve

was established for 2- to 420 milligrams of iodine. The

relative standard error of a single determination at these

two levels was 20% and 1% respectively.

This technique offers an attractive alternate to existing

chemical and instrumental methods for the determination of

iodide and chloride in silver halide mixtures since it has

the potential for providing rapid analyses with reasonably

good precision. A manuscript describing this study has been

prepared for publication.

(E. Przybylowicz, S. S, Nargolwalla, J. E. Suddueth and

(Gilbert W. Smith)

5. Blank Problems in the Analysis of Trace Oxygen

A major difficulty in the accurate and precise determination of trace amounts of oxygen by 14-MeV neutron Activation analysis is the contribution of oxygen from the sample

capsule. Errors as large as ca. 25% in blank correction

and more than 100$ in the final result can be experienced

24
if the count from the oxygen in the capsule is merely subtracted from the total sample-in-capsule count.

Prom our recent investigations, a procedure for precisely

establishing the capsule contribution to the total count from

the encapsulated sample has been defined. This procedure

takes into account the attenuation of the capsule activity

due to the presence of the sample in it. It also includes

correction for the geometrical configuration of rods of

different diameters within the capsule. For metal rods, a "flow-through" capsule (fig. 12) propelled with nitrogen in

the pneumatic transfer system has been used to eliminate any

oxygen contribution from the void volume of the capsule.

Experimental results are in good agreement with those calculated on the basis of theory. This work has been submitted

for publication.

(S. S. Nargolwalla, E. P. Przybylowicz and J. E. Suddueth)

Figure 12. Flow-through capsule

25
D- Role of 14-MeV Neutrons in the Activation Analysis of

Standard Reference Materials

During the past year, over thirty Standard Reference

Materials have been analyzed. Elements such as 0, N, F, Mg,

Si, P, Co and Ag have been determined. Our main contribution

to the certification program has been in the trace oxygen

analysis in ferrous and nonferrous materials and in the macro

analysis for the metallic component in a number of organometallic compounds. Some of the more interesting analyses

are described.

1 . Determination of Oxygen in Ferrous and Non-ferrous

Metals

Five different steels and two titanium alloys were analyzed for trace oxygen. The concentrations of oxygen varied

between 30 and 3000 ppm. Usually about six rods from each

type of sample were analyzed, and between 6 and 8 determinanations were made on each rod.

In most cases the rods were supplied in 4-inch lengths.

The rod diameters varied between 1/4 and 1/2 inch. Each

sample was cut with a clean hacksaw and a 2-inch length was

cleaned for five minutes in an ultrasonic bath charged with

trichloroethylene . The samples were rinsed in deionized

water and immediately dried in a dry nitrogen atmosphere.

Each rod was encapsulated, in our low-oxygen polyethylene

irradiation containers in a nitrogen atmosphere. The samples

were transported to the irradiation site inside a clean polyethylene bag filled with nitrogen. In spite of the great

care taken during encapsulation and transportation, a small

percentage of the samples suffer from air leaks either

during the sealing process or during transportation. To remove this source of error, a new approach was tried. The

method employed was discussed briefly in Section C. Part 5

of this report.

26
The samples were irradiated for about thirty seconds with

a standard in our dual sample-biaxial assembly, and the oxygen

content determined by a method recently described [3,4] . The

results are shown in table 1. The uncertainties* of the mean

values shown in table 1 (and table 2) are

tSn where:

D

At

t = t, /n for k-1 degrees of freedom l-a/2 to in table A-4 of NBS Handbook #91

a = 0.05 for the 95% confidence interval.

/ (y-L - y)

2 + (y 2 -y)2 + . . (y k-?)

2

\ 1/2

B V k-i /

y.= weighted mean for n determinations per sample.

y = mean of weighted means.

k = number of samples.

The analytical error in most cases is believed by us to

be insignificant relative to the imprecision due to counting

statistics. Statistical tests indicate that some degree of

inhomogeneity is induced in most samples, though insufficient

data are available to determine the degree of inhomogeneity

precisely.

In addition to the ferrous materials, macro oxygen in

cycsint (SRM 143b) was determined. Two batches of this material were analyzed. The result, 26.28±0.30$* oxygen, are in

good agreement with the stoichiometric value of 26.63$ stipulated for this high purity material.

*This treatment of the uncertainty of the results was suggested by B. L. Joiner of the NBS Statistical Engineering

Section (205.03).

27
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Analysis of Organometallic Compounds

These standards provide oil-soluble materials of known,

reproducible composition. They are primarily issued for the

transportation industry and the U. S. Department of Defense

for the analysis of lubricating oils to determine engine

wear. The 14-MeV neutron activation technique has proven

to be a highly accurate and precise method for macroconstituent analyses [4]. The organometallics are extremely wellsuited for this technique since besides the metal component,

the only other activated specie is oxygen. Two minutes

after irradiation, N from 0(n,p) N ( T

1 / 2

=7 - 2 sec ^ decay s and the activated product of the metal component can be

measured free from interference. A number of SRM renewals

in this series of compounds have been analyzed using' the

general method of simultaneous irradiation of sample and

standard followed by sequential counting of the gamma-ray of

interest. The results of analyses are shown in table 2.

Although the self-absorption corrections necessary to relate

the sample to the standard were as high as 14% in some cases,

the final results are in close agreement with the certified

values. The work with the organometallics has provided an

opportunity to verify much of our research pertaining to

evaluation of self-absorption errors in cases where photopeak

counting is done.

3. Analysis of Silicon

Silicon in Silica Brick (SRM 102) and Borosilicate glass

(SRM 93) was determined. The activation analysis results,

43 . 74±0 . 78%* Si and 37-51+0.45%* Si, compare favorably with

the certified values 43.91% and 37.68%, respectively. The

nuclear reaction Si(n,p) Al Ey=1.78. MeV, T 1/2

=2.31 min)

was used.

(S. S. Nargolwalla, J. E. Suddueth, M. R. Crambes,

E. P. Przybylowicz and Gilbert W. Smith)

*Standard deviation of the average of 4 determinations on

one sample.

30
4. ACTIVATION ANALYSIS WITH A NUCLEAR REACTOR

A

Introduction

The main emphasis in the Reactor Activation Analysis Project has been the development of the capability to perform

analyses of a variety of elements in essentially any matrix

rapidly and with the highest possible accuracy and precision.

We now have this capability for many elements, and will continue our methods development during the coming year. Some

of the methods developed are given in the following pages.

Much of our research has been involved with analysis of constituents of NBS Standard Reference Materials.

B. Research Activities

1. Group Separations for Activation Analysis of Steels

Since many of the Bureau's Standard Reference Materials

are steels a major effort was devoted to the development of

rapid group separations by means of which a number of elements

could be determined in steels, rapidly and with high precision

and accuracy. The elements for which group separation procedures have been developed are W, Mo, Ni , Cu, As, Cr, Co,

Sb , and Ga.

The basic procedure is as follows: The sample of steel

or cast iron is dissolved in a mixture of HNO_ and HC1CK with

strong fuming of HCIOk to remove carbon and to oxidize As and

Sb to the +5 state and prior to fuming. The separation procedure, which is shown in figure 13, consists of three solvent

extraction steps. Tungsten and molybdenum are extracted from

3N HC1 using a-benzoinoxime in chloroform. Antimony, gallium,

and the bulk of the Iron matrix are extracted into isopropyl

ether from 7-5N HC1. Nickel is extracted from basic citrate

solution using dimethylglyoxime in chloroform. Copper,

arsenic, chromium and cobalt remain in the aqueous phase and

can be determined quantitatively using a Ge(Li) detector to

resolve the 511 keV annihilation radiation of Cu from the

560 keV y-ray of As and to resolve the Co y-rays from any

59 remaining traces of Fe

31
Fe

Dissolve in HNO3-HCIO4 (HF) Take to fumes of HCIO4

Make 3N in HCI

Extract with a-benzoinoxime, CHCI3

r

'

1 organic aqueous

W, Mo Make 7.5N in HCI Add NaBr03 Extract with isopropyl ether

organic aqueous

Sb, Fe, Ga Cu,Cr,, Co, As Figure 13. Flow sheet for group separations from iron and

steel matrices.

The separation is very rapid; six replicates can be

carried through the entire scheme in about two hours after

dissolution. The scheme has been applied to the analysis of

a variety of cast iron and steel samples including some containing up to k% C and k% Si. Uncertainties of less than 5%

at the 95% confidence level can be obtained with 6 determinations. By counting all the fractions, an element, whose

presence might not have been suspected, can be determined

quantitatively

.

A manuscript describing this work has been submitted for.

publication.

(B. A. Thompson and P. D. LaFleur)

2 . Determination of Impurities in High Purity Zinc by

Neutron Activation Analysis

Analyses were requested of three grades of high purity

SRM zinc, two nominally 99 • 999% Zn and one nominally 99.9999%

Zn. The determination of as many elements as possible at the

ppb level was desired. To achieve this end, both nondestructive and destructive analyses were performed. The number of

elements which could be determined nondestructively was

limited by the intense radioactivity of the zinc matrix (T, /2

of Ik h and 265 d) and of the copper-64 and copper-67 radio32
activities formed by the (n,p) reactions on the zinc matrix

(T, ,~ of 12.9 h and 6l h, respectively).

In the nondestructive analyses, no impurities were seen,

but upper limits were obtained for aluminum, vanadium,

rhodium, indium and manganese.

For destructive analysis, various approaches were considered, including electrodeposition, amalgam exchange, solvent

extraction and precipitation. Group separation methods were

desired to minimize the total analyses time.

The method developed was primarily based on solvent extraction and is shown in figure 14. Silver, which was present at

the ppm level in most of the samples, was precipitated as

AgCl and removed by filtration. Tungsten and molybdenum were

extracted into CHC1_ with a-benzoinoxime ; antimony, gold,

gallium and selenium were extracted into isopropyl ether as

the chloride complexes; SnCl„ was added and the arsenic and

iridium chlorocomplexes we're extracted into isopropyl ether.

Zn

Disso

Dilute

ve in 6N

to 3N,1

HCI

dd AgN03

1 ppt AgCl

1 soln Extract with a-benzoinoxime, CHCI3

organic

r

W, Mo

1 aqueous Make 7.5 N in HCI Add NaBr03 Extract with isopropyl ether

1

1 organ ic

1 aqueous Add SnCI 2 Extract with

isopropyl ether

1

Sb, Au, Ga

organic As, lr aqueous

Zn, Cu

Figure 14. Flow sheet for group separations from a zinc matrix.

33
Only Ag, Sb and Au were actually detected but upper limits

at the ppb level were determined for the other elements.

For these group separations, a Ge(Li) detector usually was

required for the resolution of the gamma rays of the elements

of interest from those of remaining traces of Zn and Cu activities . A separate procedure was developed for the determination

of sodium and potassium. In this case, the zinc and copper

matrix activities were separated from the possible sodium

and potassium impurities. The zinc was precipitated as zinc

ammonium phosphate and the copper as the sulfide. Several

precipitations were made with large quantities of holdback

carriers. No, Na or K was observed, but lower limits were

determined for Na at the sub-ppb level and K at the sub-ppm

level.

(B. A. Thompson and D. A. Becker)

3. Determination of Molybdenum by Activation Analysis

Molybdenum is one of the elements which is very often

certified in SRM steel samples at the Bureau of Standards.

In addition, this element has been shown to be essential in

higher plants and animals, where it is present in the enzymes

nitrate reductase [6] and xanthine oxidase [7] respectively.

The levels at which molybdenum is normally found in biological

samples requires a very sensitive procedure, while the maximum precision possible is required for application to the

SRM program.

A number of procedures have been published for the determination of molybdenum by activation analysis, commonly using

a-benzoinoxime [8], cupferron [9], ion-exchange [10], etc.

Most of the published data indicate that these procedures suffer

from poor precision.

The reagent hydrogen bis (2-ethyl-hexyl) phosphate (HDEHP)

has been shown to be an excellent extractant for fission product molybdenum [11] and has been applied for the various

sample matrices here at the National Bureau of Standards.

34
a. Experimental

The samples analyzed included SRM steel samples 5& and 6g,

kale samples obtained from Dr. H. J. M. Bowen [12] and lyophilized liver samples. In all cases the samples were sealed

in quartz ampoules prior to irradiation. Standards used were

Mo0~ also sealed in quartz ampoules. Samples and standards

were irradiated with flux monitors for flux normalization.

Irradiations were performed in the glory tube facilities at

the Naval Research Laboratoary Reactor at a nominal flux of

12 -2 —1 8x10 n-cm -sec for 1 to 5 hours.

After irradiation the samples were dissolved in HN0--HC10J.

mixtures. In the case of the steel samples, HF was added prior

to HOICK fuming to drive off most of the silica.

After sample decomposition, the residue was taken up in

3M HC1CK and extracted into 0.75M HDEHP in petroleum ether for

1-2 min. The use of mechanical shaking machines is often

frowned upon when extracting intensely radioactive solutions,

since the ground glass stoppers of separatory funnels often

become unseated during the extraction and the radioactive

contents of the funnels are thrown about the laboratory area.

To circumvent this problem, separatory funnels were modified

by replacing the standard taper stopper- system with tubing

having threads to accommodate screw closures with conical

polyethylene lines. Examples of these funnels are shown in

figure 15. Using these funnels no leakage problems have

occurred.

After extraction, the samples are washed twice with 20-ml

portions of 3M HCIO^ for 15-30 seconds each. The Mo is then

back extracted with 3 15 -ml portions of 10M HN0„ containing

^3% HO. Five milliters of HOICK are added to the combined

back extracts in a 200-ml erlenmeyer flask and the sample

evaporated to fumes of HCIOk. The sample is transferred to

+++

a 40-ml centrifuge tube, 10 mg of Fe carrier is added,

and Fe(OH) is precipitated with NaOH to scavange any activities that may have accompanied the Mo. The Fe(OH)- is centri35
Figure 15. Separately funnels modified with

screw-top closures.

99 fuged off, and the supernatant liquid is counted for Mo

after allowing 24 hours for Tc equilibration. A 3 in . x

3 in. Nal(Tl) detector and a 400-channel pulse height analyzer

is used and the 140-keV photopeak is integrated.

b . Results and Discussion

The results of the analyses are shown in table 3. Using

the procedure described, eight samples may be prepared for

counting in less than 3 hours (after dissolution).

Using this separation technique it has been possible to

perform analyses at great sensitivity and with excellent precision for molybdenum. Current studies are being undertaken

to apply this technique to samples of rocks, ores, and clays.

36
Table 3. Results of Molybdenum Analyses

Sample Mo Founda Mo Present

SRM 5A 0.019±0.002#b 0.02% C

SRM 6g 0.038±0.001$ b 0.035# c Kale 2.55 ±0.08 ppm

d 2.59+0.23 ppm [9]

2.33±0.47 ppm [12]

Liver 3.^0 ±0.08 ppm

d

3.All errors are given at ts//n at the 95% confidence level

6 samples

NBS certified value

8 samples

(P. D. LaPleur)

C . Analysis of Standard Reference Materials

1 . Activation Analysis of Copper and Nickel in Clay

Standard Reference Materials

Microgram amounts of copper and nickel were determined

in SRM clays 97a and 98a by neutron activation analysis.

Radiochemical procedures were used for the separations of

copper and nickel from the complex matrix.

a. Experimental

Samples of SRM clays weighing 500 mg and of asbestos

weighing 100 mg were encapsulated in 2/5-dram polyethylene

snap-cap vials. Standards of copper and nickel foil weighing

about 10 mg each were fixed on top of the vials and the

samples were irradiated at a neutron flux of approximately

1 2 — ? _ 1 8x10 n-crn -sec for two hours in the glory tube facilities

of the Naval Research .Laboratory Reactor.

After irradiation the clay samples, with 20 mg of Cu and

1 mg of Ni carriers, were fused for 20 minutes with 2 g of

sodium peroxide in a zirconium crucible. During fusion the

37
crucible was swirled from time to time to expedite the dissolution. After fusion the crucible containing the cooled mass

was placed in a beaker containing 100 ml of 2 M HC1 and heated

to dissolve the fusion cake. Occasionally a turbid solution

was obtained which was clarified by addition of 2 ml of 48$

HP. Therefore, 2 ml of HF was added routinely to the samples

after they were dissolved in HC1.

The asbestos samples together with 1 mg of nickel carrier

were dissolved by heating with 10 ml of concentrated H SOn . The residue was dissolved in 50 ml of 2 M HC1.

Copper and nickel standards were dissolved in 5 ml of

concentrated HN0~ and diluted to 25.0 ml.

Copper . To the clay solution 10 ml of a 5% thioacetamide solution was added and it was heated for about 5

minutes to precipitate copper sulfide. After cooling the

precipitate was filtered, washed twice with water and mounted

for counting.

Nickel . The filtrate was heated to remove excess H S.

Then 10 ml of a 50$ ammonium citrate solution was added and

the excess acid was neutralized with ammonium hydroxide.

After cooling, the solution was made slightly alkaline with

ammonium hydroxide and transferred to a 2

5 -ml separatory

funnel. Five milliters of a 1% dimethylglyoxime solution wasadded and the nickel complex was extracted by shaking with 15

ml of chloroform. An additional 10-ml portion of chloroform

was used to extract any remaining nickel complex. The two

chloroform portions were combined and the volume was reduced

to about 5 ml by evaporation.

Immediately after separation, the activities of the

nickel fraction and the standard were measured with a 3 in. x

3 in. Nal(Tl) crystal and a 1024-channel pulse height analyzer.

The 1.49 MeV peak of ' 5 Ni was used for the analysis.

The activities of the copper sample and the standard

were measured with a 30-cnr Ge(Li) detector and a 4096-channel

pulse height analyzer. The 511-keV annihilation radiation

38
64 of Cu was used for the copper analysis. The gamma-ray

spectrum of the copper sulfide sample was found to have peaks

at 0.56 MeV, 0.66 MeV and 1.22 MeV which were due to 7 As.

These peaks, however, did not interfere in the determination

of copper, as they were completely resolved from the annihilation peak.

b . Results

The results of the analysis of copper and nickel in SRM

97a and 98a are shown in table 4. The yields of the radiochemical separation procedures was determined using radioactive tracers of nickel and copper. The chemical recoveries

of copper and nickel were found to be 94±2* and 95 . 5±2*

respectively.

(I. H. Qureshi)

Table 4.

Sample

SRM 97a (1)

(1)

(3)

(3)

(5)

(5)

Copper and nickel in SRM clays

Amount of Cu

(ppm)

17.4

20.0

23.0

23.8

20.2

19.2

Amount of Ni

(ppm)

75.4

81.8

69.6

78.4

82.2

83.4

Mean 20.6±2.4' 78.4±5.2 ;

SRM 98a (2a)

(2a)

(6b)

(6b)

(4e)

(4e)

Mean

208.4

217.4

206.2

194.6

186.6

189.8

200.6±12 a

172.4

174.4

173.4

181.4

156.6

176.8

176.6±8.4'

Errors are given as ts//n at the 95% confidence level.

*ts//n at the 95% confidence level.

39
2. Determination of Gold in SRM Platinum

A redetermination of gold in high purity platinum SRM

was requested. Since the gold level was known to be of the

order of a few ppm, some chemical separation from the

platinum matrix was necessary. The determination is also

199 subject to interference from the large amounts of Au

199 r -, formed by decay of v Pt . Killick [13 J has described a method of reducing this interference by use of a lead and

plastic absorber. This preferentially absorbs the low

199

energy gamma rays from Au while absorbing a much smaller

198 percentage of the Au.

a. Experimental

The procedure employed for the analysis was as follows:

Two 100 mg platinum samples were irradiated for 4 hours in

the NRL reactor. Gold standards were irradiated at the same

time. After irradiation the samples were dissolved in aqua

regia and made up to a volume of 100 ml. Gold was separated

chemically from six aliquots of each sample by extraction

into isopropyl ether using HBr . The chemical yield was

95.4%. The ether fractions were counted with a 3 in. x 3 in.

Nal(Tl) detector using the lead and plastic absorber mentioned above. The dead time was further, reduced by raising the

lower level discriminator to a point just below the 0.4l MeV

198

Au photopeak.

b

.

Results

The results of the twelve determinations are given in

table 5.

Table 5. Gold in SRM 681 (Platinum)

(Results are in ppm)

X

8.05

8.23

8.34

8.44

8.27

8.37

s

8.13

8.32

8.33

8.87

8.70

8.95

ts//n (95%) 8.42 0.28 ±0.18

40
These results are comparable to those obtained by other

methods

(B. A. Thompson, and G. W. Smith)

3. Nondestructive Determination of Manganese and

Vanadium in Iron and Steel Standard Reference

Materials 5k, 5&, 6g, lOle, lOlf, lOlg, 196 and 342a . Eight iron-based SRM's were analyzed for their manganese

and vanadium content. Their type and composition are listed

in table 6. Besides the two elements of interest, the SRM's

had additional added elements up to a maximum of 13 per SRM,

averaging about 10. These added elements ranged in concentration from <0 .1% to over 3% (except for the 70% chromium in

the ferrochrome SRM.

Similar samples have been previously analyzed for vanadium

in this laboratory [1,2]. In most cases the procedures were

essentially the same. Only where the procedures vary significantly will they be discussed here.

Table 6. Information on samples analyzed

Elemental content (%)

SRM Type Manganese

5k Cast iron 0.536 a

5£ Cast iron 0.70 b

6g Cast iron 1.05 b

lOle Crl8-Ni9 1.77 a lOlf - unknown

101g - unknown

196 Ferrochrome ^0.1b

342a Nodular iron 0.28 b

Vanadium

0.014'

0.034 1 0.054

0.043 a unknown

unknown

^0.1b

0.0l8 b

aCertified values, as reported in NBS Misc. Publ. 260 (1968

Edition). These samples were to be used as control samples

These values were aim composition or heat analyses.

41
a. Experimental

The techniques used for the analysis of these samples

varied significantly from the references given above in the

following two ways. First, a small volume portable lithiumdrifted germanium detector was used to verify the gamma-ray

purity of several of the samples, in addition to the normal

half life determination. A 3 in. x 3 in. (7.6 cm x 7.6 cm)

sodium iodide detector was used for the analyses to improve

counting statistics. Second, since manganese was also to

be determined in these samples, the complement subtraction

technique was not used. Instead, a known amount of manganese

was added to the vanadium standard approximately equal to the

amount of manganese found in the sample. Thus, the standard

consisted of both manganese and vanadium in essentially the

same ratio found in SRM's. In this way any interference by

the high manganese activity would affect both the sample and

the standard the same way. This technique allowed the analysis

for both manganese and. vanadium with a single irradiation

and a single counting period. It also eliminates some

subtle difficulties such as inaccurate live-time corrections

due to large differences in the dead time between samples

and standards.

b . Results and Discussion

The results from these analyses are presented in table 7.

Because there is some question as to the accuracy of the results obtained, the technique was thoroughly Investigated.

For the vanadium analyses, it was shown that the results were

not changed when the complement subtraction technique was

compared with the technique described above. For the manganese analyses, a second set of 5£ samples were irradiated for

a longer period of time in a higher neutron flux position,

allowed to decay for 10 hours, and then the 1.8l and 2.11 MeV

gamma-rays counted and data calculated. These new results

agreed with the previous results at the 95% confidence level.

In addition, for this second set of samples, -the manganese

H2
Table 7. Manganese and vanadium in SRM cast iron samples

Manganese "Vanadium

No. Mean ts_* No. Mean ts*

SRM No. Samples {%) /n Sampl*5S {%) /n

5k 6 0.591 .019 3 .0165 .0025

51 6 0.699 .006 6 0.036 .003

6g 6 1.05 .02 6 0.059 .003

lOle 3 1.69 .27 3 0.0345 .0035

101f-l 4 0.0934 .0156 4 0.0318 .0048

101g-8 3 0.0959 .0072 3 0.0309 .0055

101g-5 5 0.0917 .0025 5 0.0290 .0007

101g-6 3 0.0913 .0055 3 0.0283 .0007

342a 7 0.0291 .0074 7 0.019 .0017

196-1 4 0.283 .011 4 0.117 .003

196-2 6 0.284 .008 6 0.116 .003

196-4 5 0.281 .014 5 0.117 .004

196-6 4 0.280 .006 4 0.116 .005

*The ts/Zn numbers given are at the 95% confidence level.

standard used was a different chemical compound obtained from

a different manufacturer. This was done in order to eliminate any possible bias due to an insufficiently characterized standard. The vanadium standard used was a solution

freshly made from vanadium metal which had already been

rigorously evaluated as to purity and reliability.

The apparent lack of precision in some of the results

given in table 7 is at least in part due to a proven inherent

inhomogeneity for trace and minor constituents in many of the

iron and steel SRM's for samples ca. 100 mg. This characteristic can readily be seen in the vanadium contents of the

101 series. The apparent precision of the lOlg samples are

considerably better (1.0-2.1%) than the precision of the lOle

and lOlf samples (4.0-9.4%).

43
4 . Analysis for Cobalt in Lithium-Boron-10 Glass

Using a Pre-dissolution Technique

Several scientists connected with the NBSR have developed

a new SRM for the measurement of thermal neutron fluxes. In

brief, the method utilizes the activation of a 1/V activator

(in this case, cobalt) in a glass bead (^1 mm radius) which

has been made black to thermal neutrons through the incorporation of 10$ lithium oxide and 40% boron oxide (92% enriched

boron-10). The cobalt content was known to be approximately

9%.

Previous to our work, wet chemical analyses were performed on the cobalt content of this glass, and the results showed

an apparent inhomogeneity at small sample sizes, and a cobalt

content of 9.23%. Since the purpose of these beads was to

determine a neutron flux with an accuracy and precision

approaching 1% , and a great deal of time and effort had been

put into making the glass, these results required verification

before acceptance. Thus, the object of our analyses was to

verify these findings. The use of a completely different

analytical technique, such as neutron activation analysis

should tend to eliminate any systematic errors and produce

a clear-cut answer to the homogeneity problem. However, due

to the severe neutron self-shielding problem involved, the

absolute cobalt number obtained may have a negative bias.

This bias should not affect the precision of the analysis

and the homogeneity results should still be valid, providing certain precautions are taken to Insure exactly the

same amount of self-shielding for all the samples.

a. Experimental

The samples, in the form of small chips of glass, were

weighed and transferred to tared polyethylene snap-cap vials.

There were seven samples, with weights varying from 1.519 mg

to 3.660 mg. The samples were then dissolved in the polyethylene vials using small amounts of perchloric and hydrofluoric acids. After complete dissolution, the solutions

44
were diluted with de-ionized water until the sample weight

was lg, and the vials closed and heat sealed. The standards

were made from pure cobalt metal, which was dissolved and

diluted in exactly the same manner as the samples. All

samples and standards had copper foil flux monitors attached

for flux normalization.

The 10.5 min m

Co was used for the analyses. The

vastly improved sensitivity at short irradiation times for

small samples over the long-lived Co more than offset the

disadvantage of having to count the low-energy 59 keV isomeric transition photons. It was felt that, since the

samples and standards were to be diluted and counted in

exactly the same way, any gamma-ray absorption present would

be identical for all standards and samples. One other

problem may be present; that is the neutron self-shielding

within a sample due to the high lithium and boron-10 content.

Dilution of the sample by almost a factor of 1000 will decrease the neutron self-shielding to a small value. In

addition, since all samples have exactly the same configuration in the dilute form, samples of equal weight will

have identical neutron self-shielding. Thus a plot of

specific activity versus sample weight should reveal any

neutron self-shielding still present.

The procedure for analysis was as follows: the samples

were irradiated for one minute in the south pneumatic tube

facility of the Naval Research Laboratory Reactor, and

were allowed to decay for two and one-half minutes. Then

the samples were counted for five minutes using a 400-channel

pulse height analyzer and a 3 in. x 3 in. Nal(Tl) detector.

In all cases approximately 1,000,000 counts were accumulated

in the 59-keV peak after subtraction of background. Appropriate corrections were made, including flux normalization.

45
b . Results and Discussion

The results obtained averaged 9-17±0.12% cobalt (± value

is ts//n at the 95% confidence level). These results

indicate that the maximum inhomogeneity present is of the order

of 1.5%. However, since the precision of the technique, even

with great care, is approximately 1% , it is not definite

whether an actual inhomogeneity does exist. The cobalt concentration observed is slightly less than the wet chemistry

results, however, the values overlap.

Concerning the possible problem of neutron self-shielding,

a comparison of samples having over a factor of two difference

in glass content showed no trend toward a decrease in specific

activity with an increase in sample weight. This indicates

that no significant neutron self-shielding was present at

these dilutions.

(D. A. Becker)

5 • Copper and Arsenic in SRM Cast Iron Samples

As part of the Standard Reference Materials certification

program at the National Bureau of Standards, we determined the

copper and arsenic content in cast iron SRM's 5£ and 6g, and

nodular iron SRM 342a. Copper and arsenic are easy to separate together as acid sulfides, and, using a Ge(Li) detector,

the 511-keV annihilation radiation from the Cu is easily

resolved from the 560 keV principal gamma ray from the 7 As.

a. Experimental

Samples of the SRM's were weighed out (ca. 100 mg) into

polyethylene snap-cap vials; copper flux monitors were attached, and the samples, along with standards of As 0^ (primary

standard) and copper metal, were irradiated for one hour in

the glory tube facilities of the NRL reactor. The samples

were dissolved in 15 ml of 1:1 HNO -HCIO^ + 10 mg Cu carrier.

When fumes of perchloric acid were visible, the samples were

cooled slightly and about 3 ml of 48$ HF was added and the

samples were fumed to incipient dryness to drive off the

46
silica as SiF^. The samples were then taken up in 20 ml of

1 N HC1 and heated to boiling. About 50 mg of KI was added

to assure reduction of the As to As(III), and copper and

arsenic precipitated as the sulfides with about 10 ml of 5%

thioacetamide in water. The samples were kept at or near

the boiling point for about 3 minutes, and allowed to cool.

The precipitates were filtered through glass-fiber filter

pads, washed, dried with acetone, and counted using a 30-cc

Ge(Li) detector in conjunction with a 4096-channel pulse

height analyzer.

b . Results

The results are summarized in the following table:

Table 8. Copper and arsenic content of SRM

cast iron samples

SRM Sample Cu content {%) As content {%)

51 1 1.015 0.00098

0.00136

0.00112

0.00096

0.00092

0.00091

0.00104±.000l8 a

#

6g 1 0.521 0.0430

0.0428

0.0422

0.0426

0.0445

0.0414

0.0428±0.0011 a

#

342a 0.1468 Not determined

(<10 ppm)

1 1.015

2 0. 982

3 1.010

4 0.996

5 0.982

6 1.017

mean 1.004±0.019 %

1 0.521

2 0.524

3 0.507

4 0.517

5 0.526

6 0.526

mean 0.520±0.008 d'^

0.1468

0.1448

0.1432

0.1390

0.1420

0.1438

mean 0.1433±0.0029 %

l All errors are given as ts//n at the 95% confidence level.

(P. D. LaPleur)

47
6 . The Determination of Cu and Sb in Solder

The Activation Analysis Section was requested to participate in the certification of SRM 127b which is a k0% Sn - 60% Pb material. The elements requested were Cu, Sb , and As.

It was decided to use an acid sulfide separation in the

presence of HF (to complex the Sn and prevent its precipitation) and use a high resolution Ge(Li) detector to resolve

the gamma rays of the Cu, Sb and As.

a. Experimental

The solder (ca. 100 mg) was weighed into polyethylene

snap-cap vials, Cu flux monitors were attached, and the

samples and appropriate standards of Cu, As, and Sb were

irradiated for one hour in the glory tube facilities of the

NRL Reactor. The samples were dissolved in approximately

10 ml of concentrated HpSCv, 10 mg Cu carrier was added, the

samples were cooled, and transferred quantitatively to 40-ml

conical centrifuge tubes. The samples were centrifuged and

the supernatant liquid transferred to erlenmeyer flasks

The PhSCv precipitates were washed once with a 5% Na^SCv

solution, centrifuged, and the wash added to the samples.

The precipitate was discarded. The samples were then heated

to boiling, KI added to reduce the As to As (III), about 3 ml

of 48$ HP and 15 ml of 5% thioacetamide solution were added.

The samples were kept at or near the boiling point for about

3 minutes, then were removed from the hot plate and allowed

to cool. The precipitates were filtered through glass-fiber

filter pads, washed, and dried with actone. The samples

were then counted using a 30 cc Ge(Li) detector in conjunction

with a 4096-channel pulse height analyzer.

b

.

Results

Examination of the gamma-ray spectra showed that the

activity of the As was so low, compared to the high Sb

activity, that the peak could not be totally resolved from

the Sb peak. To remove the possibility of bias from the As

48
122

on the Sb results, the 687 keV peak of Sb was used for

the analyses, along with the 511 keV annihilation radiation

for the Cu. A rapid method for separating the Sb from the

As is presently being developed. The results for Cu and Sb

are given below:

Table 9. Copper and Antimony content of SRM

127b (solder)

Cu content {%) Sb content (%)

SRM 127b 0.0098 0.409

0.0095 0.431

0.0113 0.457

0.0104 0.380

mean . 0103±0 . 0013 a

# . 4l9±0 . 052 a

%

Errors are given as ts//n at the 95% confidence level.

(P. D. LaFleur)

7 . Activation Analysis of SRM Urea, Creatine and

Uric Acid

The NBS Office of Standard Reference Materials is in the

process of characterizing the above clinical materials in

preparation for issuance as Standard Reference Materials

(SRM's). One aspect of this characterization was to be a survey of these specially purified materials for impurities,

especially enzyme poisons. For this purpose, the Activation.

Analysis Section was asked to examine these materials for

trace elemental impurities,

a. Experimental

The samples were irradiated in the in-core facility at

the NRL reactor for 1 hour at a neutron flux of approximately

12 —2 —1 8x10 n.cm .sec . After irradiation, the samples were returned to the NBSR for nondestructive counting and for group

separation procedures. In addition, some short irradiations

were made in the NRL pneumatic rabbit irradiation positions

for short half-life radioisotopes. These samples were counted at NRL with no chemical separation; but with transfer to

clean non-irradiated containers before counting.

49
b . Results and Discussion

A number of elements were found to be present in trace

quantities in these biological materials. They included

chlorine, manganese, copper, gold, aluminum and zinc at the

sub-ppm level and sodium, which was present at levels of

^1-150 ppm. In addition, arsenic and antimony were looked

for but not found.

(D. A. Becker and T. E. Gills)

8 . Determination of the Homogeneity of SRM Clays

Nos. 97a and 98a: Analyses for Sodium and Scandium

Two renewal SRM clays were received for homogeneity

studies, No. 97a, Flint Clay, and No. 98a, Plastic Clay.

Three different cuts of the finely powdered material were

received.

These six clay samples were examined by nondestructive

neutron activation analysis to determine which elements, if

any, could be easily used for a study of the inhomogeneity

in trace element content. The two elements selected, sodium

and scandium, were excellent for a homogeneity study, because

of their different chemical characteristics and their ease of

determination by nondestructive techniques.

a. Experimental

Irradiations were made in the glory tube facilities of

the NRL Nuclear Reactor. Samples of approximately 100 mg

were heat-sealed in polyethylene snap-cap vials before irradiation. After irradiation, the samples were quantitatively

transferred to clean, non-irradiated poly vials for counting.

Counting equipment used included a 3 in. x 3 in. Nal(Tl)

detector and a large volume Ge(Li) semiconductor detector.

The germanium detector was used to verify that only one y-ray

peak was in the area of interest, then the sodium iodide detector was used to obtain a large number of peak counts to

minimize the error due to counting statistics.

50
b . Results and Discussion

The results are given in Tables 10 and 11. Since only

the homogeneity was of interest, the numbers were calculated

relative to each other. Corrections were obtained and made

for flux variations within the irradiation position, both

vertically and horizontally.

Since the value of a homogeneity test is directly related to the precision of measurement, considerable time was

expended in the evaluation of random and systematic errors

on such precision. Experimental work with the same and

similar type samples showed that with considerable care, we

could routinely obtain precisions of the order of 1%. Thus,

the values shown are estimated to have a precision of 1-2%.

The calculated ± values (S„ of average) are 1.0% and

1.3$ for the scandium and 2.4% and 2.8% for the sodium, for

97a and 98a, respectively. This indicates no apparent inhomogeneity for the scandium distribution. However, since

the standard deviation of 2.4% and 2.8% are significantly

above the precision of the technique, there does seem to be

a small inhomogeneity in the sodium distribution among the

three cuts.

(D. A. Becker)

D. Service Analyses

1. Nondestructive Neutron Activation Analysis of

Impurities in Several Quartz Samples with a Lithium - Drifted Germanium Semiconductor Detector

Pour samples of quartz were submitted to the Activation

Analysis Section for determination of their impurity content.

The samples had been obtained from various sources of supply,

and were to be examined for absolute and relative impurities,

in order to select the best source for the specific requirements at hand.

51
Table 10. Results of Homogeneity Studies of SRM Clay #97a

Sample Relative

Cut Scandium Average

Concentration Scandium

Relative Average

Sodium Sodium

Concentration

1.03^

0.998

0.991

1.008

1.068

0.972

1.021

1.020

1.011

0.999

0.991

1.000

1.015

0.993

1.009

1.006

0.986

1.004

0.987

0.992

0.965

1.005

0.951

0.974

Average =

1. 000±0.010 1.000±0.024

Absolute Scandium concentration (Relative cone. = 1.000) is

34.4 ppm on a dry basis.

Absolute Sodium concentration was not determined. The ratio

of the two sodium concentrations was: [Na] 95a

[Na] 97a

± Values are standard deviation of the average

.

= 1.986

NOTE: Sample sizes ranged from 85 mg to 135 mg with an

average of 120 mg. All samples were dried several days

@ 110°C before weighing. Cut numbers are those of the

Office of Standard Reference Materials.

52
Table 11. Results of Homogeneity Studies of SRM Clay #98a

Relative

Sample Scandium Average

Cut Concentration Scandium

Relative

Sodium Average

Concentration Sodium

2a 1.018

1.006

1.011

1.011

1.013

0.950

1.029

0.995

4c 1.005

0.999

0.9^9

0.984

1.001

0.999

0.937

0.979

6b 1.002

1.012

1.004

1.006

1.034

1.069

0.975

1.026

Average =

1.00010.013 1.00010.028

Absolute Scandium concentration (Relative cone. = 1.000)

is 39.1 ppm. on a dry basis.

Absolute Sodium concentration was not determined. The

ratio of the two sodium concentrations was: [Na] 98a _ -. p<r [Na] 97a " 1>y0b

i values are standard deviation of the average.

NOTE: Sample sizes ranged from 90 mg to 142 mg 5 with an

average at 117 mg. All samples were dried several

days at 110° C before weighing.

53
a. Experimental

Since considerable care had been used in the packaging,

samples were analyzed as received, except in one case where the

sample was too large. In order to reduce the size to that

required, the large single piece was placed inside a section

of clean thick-walled polyethylene tubing, the ends clamped

shut with hemostats, a hammer used to break up the quartz and

a fragment was selected for analysis. The quartz did not cut

through the polyethylene, so no contamination should occur

through this process.

The samples were irradiated in precleaned polyethylene

vials, for 1 hour In the NRL Nuclear Reactor. They were then

brought back to NBS , transferred to clean, non-irradiated

vials, and counted on a 30cc lithium drifted germanium detector

b

.

Results

The results obtained are found in table 12. Since high

precision and accuracy was not required, and since the primary

interest was in the relative impurity concentrations between

the four samples for one element, multiple samples were not

analyzed.

c

.

Discussion of Results

The results shown in table 12 indicate a great range in

impurity contents of the four quartz samples, approaching

three orders of magnitude in one case. No one sample is

lowest in all impurities, which means that the source selected

would have to be on the basis of which impurities would interfere the least in the planned utilization of the finished

material

.

(Donald A. Becker)

2 . Nondestructive Analysis for Silver, Chlorine, Bromine,

Sodium and Potassium in Quartz

The absorption and exchange of molten silver bromide and

silver chloride in contact with quartz surfaces was being

evaluated and the Activation Analysis Section was asked to

54
co

CD HaS

cti CONP

in

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Oh

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CD H

cti Eh

a

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CDOcoo e3 oo

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cti bV

-po

Pm6 rH M O o\ rH

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CDCO

CD OA t— G C\J oo r- o>

cti o o H

H

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m o o O

C . • • •

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>>coe vr> CM on VD

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CD o CO t— o

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tKI rH

V

V

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T3 o CM o

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bO

CD v_^ MD H -P CM vo ITS CM ft^ O o t— LO e ho H rH o H

CO CD

O o o O

13

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cti s

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55
analyze quartz tubing samples for silver, chlorine, and

bromine. During the course of the analyses it became known

that the sodium and potassium concentrations in the quartz

were important also, and could be obtained, in most cases,

with little extra effort on our part.

We received a total of four sets of samples, which included

quartz tubing which had been in contact with the molten salts

as well as non-contacted samples. They were analyzed as

received, with no additional cleaning. Care was taken in the

transporting and storage as well as during the irradiations

so that no contamination of the samples occurred. The product nuclides used for the analyses were silver-110, chlorine37 j bromine-82, sodium-24, and potassium-42 . The concentrations found ranged from less than 0.1 to over 400 ppm.

Additional information and specific results can be obtained from the publication by K. Stern [14].

(D. A. Becker and E. D. Anderson)

3. Analysis of Nickel and Manganese in Standard

Asbestos Samples

The National Center for Urban and Industrial Health, U.S.

Public Health Service, Cincinnati, Ohio, prepared a number

of asbestos samples for their Industrial health standards

program. These samples had been analyzed for several elements

by two laboratories, one using activation analysis, the other

atomic absorption spectrometry. In the case of the Mn and Ni

content of these samples, the two laboratories disagreed

markedly. The Activation Analysis Section was asked to provide reference analyses for these two elements.

a. Nickel

The experimental technique was the same as that described

in Section C, Part 2 of this report.

The results we obtained, together with the results of

the other laboratories are given in table 13. Our values

agree well with those of the atomic absorption technique

56
Either inhomogeneity of the sample or, more likely, inter56 ference from Mn if nondestructive activation analysis was

used, may be the cause of disagreement between the two laboratories. Due to the limited quantity of samples received, any

inhomogeneity could not be investigated.

Table 13. Nickel content of asbestos samples.

Sample Amount of Ni (ppm) in Asbestos Samples

Lab H

(Activation

Analysis

)

Crysotile 0-991

Crysotile 0-010 <200

Crocidolite 0-014 8700

Crocidolite 0-993

Amosite 0-007 1500

Anthrophyllite 0-016 1900

Lab C NBS

(Atomic (Activation

Absorption) Analysis

)

1970 1506

795 659

13 12

139 84

34 25

424 488

(I. H. Qureshi)

b. Manganese

Nondestructive manganese determinations were made

by neutron activation analysis on samples of about 100 mg

each. After irradiations of 10 minutes in the NRL rabbit and

56

3 hours decay, gamma-rays from the 2.58 hour Mn were counted

using a sodium iodide detector.

Results are shown in table 14. Relatively large amounts

of sodium (probably milligrams) were found in the Crocodilite

24 samples II, III and VI, and the induced Na was removed by

complement subtraction. The agreement with either Lab H or

Lab C is good in the case of samples I and III and fair in

the case of VI. Because only 100 mg of each sample was furnished, no estimates could be made of sample inhomogeneity

57
Table 14. Manganese results on asbestos samples.

Sample

No. Description

I Chrysotile 0-991

II Crocodillte I 0-992

III Crocodilite II 0-993

IV Amosite 0-99^

V Amosite 0-007

VI Chrysotile "B" 0-010

VII Crocodilite 0-014

VIII Anthophyllite 0-016

Quoted Cincinnati

Analyses

ppm Mn

ppm Mn Lab A Lab B

Based[ on

0.845MeV l.blMeV Atomic

Peak Peak A. A. Atisorption

866 843 868

675

1 - - 924

1018 1 - - 950

5188 4852 - 3988

12321 11794 15000 13900

584 568 510 443

1042 1

779

1 870 864

1473 1450 1200 988

24 Na subtracted from spectrum by complement subtraction.

(Gilbert ¥. Smith)

4 . The Determination of Copper in Serum and Urine

In cooperation with the National Institute of Arthritis

and Metabolic Diseases at the National Institutes of Health,

we determined the copper levels in blood serum and urine

taken from a patient suffering from Wilson's Disease.

Wilson's Disease is a hereditary disease in which the patient's

metabolism is unable to control the trace element copper.

We received samples of serum and urine taken prior to treatment with penacillamine and after treatment was well established.
a. Experimental

One milliliter samples of serum were transferred to

weighed quartz ampoules which had been rigorously cleaned

with HNO_ and distilled water. The ampoules were sealed,

and the contents weighed by difference. Copper flux monitors

were attached, and the samples were irradiated in the glory

tube facilities of the NRL reactor for one hour. The ampoules

were carefully opened and the samples transferred with 10 mg

Cu carrier to erlenmeyer flasks quantitatively. The samples

were ashed with HN0_ - HClCv and the residue taken up with

about 25 ml of 1 N HC1. The samples were heated to boiling

and 10 ml of 5% thioacetimide solution was added. The samples

were held at or near boiling point for about 3 minutes then

removed from the hot plate and allowed to cool. The precipitate was collected on a glass-fiber filter pad, washed with

water, and dried with acetone. The samples were then counted

using a 3 in. x 3 in. (7-6 cm x 7.6 cm) Nal(Tl) detector in

conjunction with a 400 channel pulse height analyzer. The 511-

64 keV annihilation radiation of Cu was used for the analysis

.

b

.

Results

The results are summarized in table 15.

Table 15. Copper content of human serum and urine

Serum

Taken 2/26/68 3.4 ppm Copper

Taken 3/5/68 3.7 ppm Copper

Urine

Total Cu

Taken Total Volume Cu Content (ppm) Excreted

2/25 - 2/26/68 1710 ml 1.9 0.33 mg

3/4 - 3/5/68 3000 ml 6.4 1.92 mg

These results agree with the results of atomic absorption

spectrometry

.

(P. D. LaPleur)

59
5. Preparation of DNO~ for the NBS Reactor

In order to minimize corrosion of the primary coolant

system in the NBSR, it is desirable to maintain the pD of the

system at or near the neutral point. During operation, the

pD slowly rises, so it is necessary to add acid to the system

periodically. To avoid adding light hydrogen (protium) to the

heavy water system, we were asked to make some heavy nitric

acid by the Reactor Operations Section of the Reactor Radiations Division, using the method utilized by R. L. Tromp [15] at

the National Reactor Testing Station. The method used is the

classical method of preparing a low-boiling point acid from a salt of the acid and a higher boiling acid.

a. Experimental

A 2-lb. ampoule of Sulfan* stabilized SO-, (liquid) is

sealed into an all-glass system consisting of the ampoule,

and a condenser which terminates in a tube long enough to

extend slightly below the surface of 180 ml of DO in a 500-ml glass stoppered reagent bottle. The bottle is vented

to the air through a drying tube containing MgCClO. ) ?

. The

SO-, is distilled into the D

? (which is resting in an ice

bath), slowly at first, then more rapidly as the concentration of the D SO. being formed increases, using infra-red

heat lamps. When nearly all of the S0„ has been distilled,

the 500-ml reagent bottle containing the DpSO. is removed and

quickly stoppered.

Another all-glass system is prepared consisting of a 3000-

ml round bottom flask containing 4 lbs of NaN0_, which has

been dried at 120° C for at least 24 hours, and about 1500-ml

of D^O, connected through a condenser to a 4 liter reagent

bottle. The boiling flask is in a heating mantle which is on

top of a large magnetic stirrer, and a 3/8-in x 2-in Teflon

*See disclaimer in preface

60
stirring bar is in the flask. One neck of the boiling flask

has a dropping funnel in it through which the DpSCK is added.

The flask is heated with stirring to prevent bumping and DpSOj.

is added slowly. The DNO_ produced is distilled into the

reagent flask at about 120° C. Using the system described,

DNO- of 11 M was produced.

(P. D. LaFleur)

61
5. ACTIVATION ANALYSIS WITH THE NBS LINAC

A. Introduction

Useful beam from the NBS electron linear accelerator has

been available for about 18 months. Our efforts during this

time have been divided roughly equally between the methodology

of photon activation analysis including flux monitoring, evaluation of systematic error and calculation of sensitivities,

and determinations for which photon activation is particularly suited. These included the determination of carbon

and oxygen in sodium, yttrium in rare earths and cast iron,

and carbon in sulfur.

B. Facilities

The target and pneumatic transfer facility described in

previous progress reports continues to function in a satisfactory manner. The fluorescent screen is of great assistance

to the accelerator operators in positioning the electron beam

properly. Figure 16 shows a photograph taken on closed circuit

television of the electron beam striking the screen. The beam

approximately fills a circle of one inch diameter. In the

Figure 16. Photograph of electron beam from

LINAC striking fluorescent screen

62
foreground the beam pipe which carries the electron beam may

be seen.

A second rabbit terminal has been installed directly behind the original terminal. This is used for production of

isotopes for decay scheme studies, Mossbauer spectroscopy,

and tracers for radiochemical separations research.

C . Carbon and Oxygen in Sodium

The determination of carbon and oxygen in sodium is a problem of substantial concern in the technology of liquidsodium cooled reactors and one for which photon activation

analysis is uniquely suited.

Classical methods for these determinations are subject

to error because of the possibility of contaminating the

surface of the sample before an analysis of the bulk of the

sample can be accomplished. In addition, reagent and equipment blanks may be large relative to the amount of the nonmetal to be determined.

In photon activation, the nuclear reactions and the

half-lives of the products of interest are

12 C(y,n) 1!L C 20.5 min

1 0(y,n) 15

C 2.1 min

Both radionuclides decay by positron emission. Their halflives are of sufficient length to permit a simple separation.

After irradiation, the samples are etched to remove approximately 25% of the sample before separation. The separation

of carbon has been described [16] . The separation of oxygen

consists of dissolving the sample in 6M NaOH under a stream

of nitrogen. The radioactive oxygen is converted to hydroxide

which exchanges with the water. A portion of the water is

rapidly distilled and the positron anhillation radiation

counted by coincidence ' spectrometry . Yields of 40-50% are

usually obtained and the time from the end of irradiation to

63
beginning of counting is usually about four minutes. Sensitivities of a few ppm are possible.

(G. J. Lutz and D. A. DeSoete)

D. Matrix Effect

A general source of systematic error in activation

analysis is the difference in absorption of the bombarding

particles between sample and standard. Serious error can

arise through neglect of differences in self-shielding. We

have evaluated the extent to which these errors can occur in

our photon activation facility.

Since the mean free path of the photons in the sample

is large compared to the dimensions of the sample one may

write

f

=e

"tJ*P (1)

fo

where fo = photon flux with zero attenuation (photons/

2 , cm - sec

)

2 f = photon flux after attenuation (photons/cm - sec

)

Eyp = The sum over all elements in the sample of

the density of each element (cm

-

) t = Thickness of the sample (cm)

Since the activity per unit weight of an element in the

sample produced during irradiation is proportional to the

flux we may replace fluxes with A and Ao

A = e -tZyp

(2)

Ao

Since y is energy dependent, for complete rigor the right

side of the equation should be replaced with a sum of terms

over all photon energies. For ease in computation and without significant loss in accuracy one may consider an average

energy and use the gamma ray absorption coefficients corresponding to this energy. A logical choice is the energy of

maximum cross section.

64
In our facility, samples are cylindrical in shape and

have a diameter of 0.95 cm. The photon beam is perpendicular

to the axis of the cylinder and thus travels a circular cross

section of the sample.

Samples of MgO , PbO and carefully blended mixtures of

the two compounds to give variations in photon absorption

24 properties were irradiated and the specific activities of Na

202 25 24 and v Pb produced for the reactions Mg(yjP) Na and

204 20^ Pb(y,n) J Pb were measured. The results were fitted to

the logarithmic form of equation (2).

InA = -tZup +lnAo

The value of t was experimentally determined to be 0.32±.02 cm. This is in reasonable agreement with the estimated value

which would be 0.785 x radius or 0.38 cm.

(G. J. Lutz)

E. Sensitivities in Photon Activation Analysis

A new radiator for the photon activation analysis facility

has been designed. It was considered worthwhile to estimate

the photon flux to be expected from this target and calculate sensitivities for determination of the elements.

Estimates have been made of specific activities to be

expected from bremsstrahlung produced by an electron accelerator

,The photon flux distribution from electrons striking a 0.6cm.

tungsten target at different energies and included in the

cone described by a five degree angle from the forward direction has been calculated. Flux times cross section for

photonuclear reactions of analytical utility was integrated

and disintegration rates of the reaction products for most of

the elements under conditions of different electron energies

and irradiation times were calculated. Relative values for

the specific activities were calculated and compared with the

experimental results of Oka and co-workers [17].

65
The comparison of measured and calculated (y,n) yields

was made under the irradiation conditions of 20 MeV electrons

and a 0.2 mm platinum radiator. Since Oka's paper did not

specify the angle subtended by his samples, it was possible

only to compare relative yields. Our calculated results were

6 55 54 normalized to 2x10 reactions/mole for the Mn(y,n) Mn reaction to coincide with the values found by Oka. The calculated results are plotted along with those of Oka in figure 17

The agreement is satisfactory.

(G. J. Lutz)

P. Carbon in Sulfur

A request was made by the Office of Standard Reference

Materials for the determination of carbon in intermediate

purity sulfur. A sample of the sulfur had previously been

irradiated with thermal neutrons and no gamma-emitting

products had been observed. A preliminary irradiation with

35 MeV photons yielded, as expected, a prodigious amount of

30 2.5 minute, positron emitting, P produced via the reaction

32 30 S(y,np) P. When this had decayed, the only activity

observed was the 20.5 minute, positron annihilation gamma of

C produced via the reaction C(y,n) C.

A matter of concern in the determination was extraneous

contamination. Since the lumps of sulfur obtained powdered

to a great extent from the shock of travelling by compressed

air to and from the irradiation position, the commonly used

technique in AA of removing the surface after irradiation

and before counting was not practical.

Since a bulk analysis was desired, approximately onequarter inch of material was skimmed from all surfaces of

the sample which were irregular lumps of about one inch

dimensions. In all the pre-irradiation manipulations, only

tools and container of glass and stainless steel along with

the irradiation containers to be described were allowed to

come in contact with the surfaces.

66
I0l

I0r -

I06 -

Q

_)

<I

_l

cr

10

I0

£

iot

1 1 1 1 1 1 1 1 1

X

x

x

x x*6>

X o

-

o

o

ox

'* ox xo

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X °

o

X X x ~_ o °°

x o °o O

O

O

o

o

X

Ox

X o XX

o

x o

O

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OKAETAL

X O

X CALCULATED YIELDS

X

1 1

1 1

1

5 _

20 40 60

ATOMIC NUMBER (z) 80 100

Figure 17 . Normalized results of sensitivity calculations

shown with experimental results of Oka et al

.

67
In our facility samples are usually encapsulated in snap

cap polyethylene vials which are placed in large, aluminum

rabbits for irradiation. Because of concern over recoil C

atoms from the polyethylene containing the sample, small aluminum vials, fabricated in the shop, were used for encapsulation. After the removal of the surface of the sulfur, it

was pulverized in a glass mortar and samples were encapsulated

Discs of polyethylene were taped to each end of the aluminum

vials as flux monitors. Powdered graphite was used as a standard.

The samples were irradiated for 20 minutes with a beam

of 30 uamps and an electron energy of 35 MeV. After irradiation, the samples were allowed to decay for about 30 minutes

and then were transferred to clean vials and the positron

annihilation radiation decay followed for about 30 minutes.

Results obtained are given in table 16.

Table 16. Carbon content in intermediate purity sulfur.

Lot Number C content (ppm)

1 73,80,60,72

2 68,82,76

3 69,50,62

4 59,78,65,77

(G. J. Lutz and D. Setlock)

G. Yttrium in Rare Earths

Yttrium has been determined in a variety of rare earths

oq 00

by the reaction Y(y,n) Y. The product nuclide decays with

emission of 0.90 and 1.83 MeV gammas in cascade. Samples were

measured by counting the 1.83 MeV gamma ray with a 30-cmJ

lithium-drifted germanium detector or a 3 in. x 3 in. Nal detector, with two 4 in. x 4 in. Nal detectors using coicidence

counting.

68
An analysis of relative sensitivities is shown in table

17. The first column shows the detector system used.

The next column shows background; for the 3x3 Nal and Ge(Li)

detector, this is the region of the 1.83 MeV photopeak. Using

the method of Currie [18] for calculating detection limits for

20 hours of counting background and 20 hours of counting sample

the minimum detectable count rate is shown in the next column.

The fourth column shows detection efficiency which is based

on irradiation as well as counting conditions. The irradiation conditions are a two hour irradiation with an electron

energy of 35 MeV and an average beam current of about 30yA

The optimum counting geometry is used in all cases. The fifth

column is the ratio of the third and fourth columns and shows

the maximum mass of yttrium detectable. Coincidence counting

is somewhat superior to the other two methods . Since several

grams of sample can be accommodated, a sensitivity of a few

tenths of a ppm is possible.

A manuscript describing this investigation is being prepared for submission to a scientific journal for publication.

Table 17. Comparison of sensitivities for yttrium using

various detector systems.

Minimum Detection Minimum Mass

Detectable Efficiency of Y

Background Activity (Counts/hr Detectable

Detector (Counts/hr) (Counts/hr) - yg Y) (yg)

30 cm

3 Ge(Li) 1.5 1.5 .3 5.0

3-in x 3-in 200 15 8.5 1.9

Nal(Tl)

Two 4-in x 4-in 1.5 1.5 1.6 .9

Nal(Tl) in

coincidence

69
6. EXTRACTION OP METALS BY BIS( 2-ETHYL-HEXYL)

ORTHOPHOSPHORIC ACID

Solvent extraction studies using bis (2-ethyl-hexyl)

orthophosphoric acid (HDEHP) as the extractant, are being

made with the ultimate aim of developing group chemical separation procedures. The extraction behavior of Ti, Cr, Mn,

Zr, Nb, Mo, Tc, Hf, Ta, W, So, Y, and the lanthanides from

1 to 11M solutions of hydrochloric, perchloric and nitric

acids into a 0.75M HDEHP solution (diluted with cyclohexane

or n-heptane) has been studied.

The group IVB elements and scandium exhibit high extraction which is independent of hydrogen ion concentration; the

group VIIB elements are essentially unextracted. The extraction of some elements of group VB and VIB and of the lanthanides reaches a minumum and then increases with increasing

acidity.

The log of the distribution ratios of the group III-VIIB

elements and the lanthanides have been plotted as a function

of acid concentration in figures 18 to 21.

In order to get more information on the extraction mechanism further investigations were carried out on the extraction of molybdenum. Solutions containing different amounts

of HDEHP were used to study the influence of solvent concentration in the organic phase on the extraction of molybdenum

from 3M and 9M nitric acid solutions. A log-log plot of the

distribution ratios versus HDEHP concentrations, shown in

figure 22 exhibits a straight line with an approximate slope

of 1, which indicates 1:1 solvent dependency for molybdenum

extraction.

Solutions containing semi-gross quantities of molybdenum

were used to study the effect of molybdenum concentration on

the distribution ratio. The distribution ratio was found to

increase with increasing molybdenum concentration in the

aqueous phase and levels off at a concentration of approximately 5 mg of Mo/ml. The distribution ratios in 9M HNO~

70
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74
•o

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1.9

1.7

1.5

a -9M HNO

o-3M HNO

_L

-I 0.8 0.6 0.4 0.2

LOG HD 2 EHP CONCENTRATION

Figure 22. Plot of log Kd for molybdenum as a function of

HDEHP concentration.

were found to be higher than that in 3M HN0_. The extraction

remains quantitative even when 10 mg of Mo/ml or a total of

100 mg of Mo, was in the aqueous phase.

According to the solvent dependency studies, one mole of

HDEHP should be required for the extraction of one mole of

molybdenum from the solution. However, HDEHP was found to

extract more than stiochiometric amounts of molybdenum which

indicates that a high molybdenum concentrations polymerization in the organic phase may take place. Infra-red studies

also indicate a change in the character of the organic species

and the possibility of polymerization at high molybdenum

75
concentrations. Formation of chain polymers has been observed by Baes, et al . [19] in the extraction studies of uranium by HDEHP.

The extraction of metals from acid solutions greater

than 5M HDEHP appears to be complex. At high aqueous acid

concentrations j interactions similar to those observed in

TBP [20] involving the acid, or its anion, may be operative in

the extraction. Therefore, the extraction of hydrochloric,

perchloric and nitric acids into 0.75M HDEHP was studied.

Several solutions of three acids were equilibrated with

solutions of HDEHP by mechanically shaking for 2 minutes.

The two phases were separated by centrifugation and the

aqueous phase was titrated with a 0.5M sodium hydroxide

solution to determine the amount of acid extracted into the

organic phase. The distribution of the acids between the

organic and aqueous phases is shown in figure 23. It may be

seen from the figure that for nitric and perchloric acids,

the amount of acid extracted varies linearly with the initial

aqueous acid concentration up to about 9M original acid concentration. Above 9M the curves become asymptotic, indicating

saturation of the organic phase.

Infra-red spectra of the equilibrated organic phases show

the presence of nitrate and perchlorate absorption bands in

the organic phase with aqueous acid concentrations greater

than 4M. The intensities of these absorption bands increases

with the acidity of the aqueous phase up to about 9M aqueous

concentration confirming the titration data. However, infrared spectra of HDEHP solutions which were equilibrated with

aqueous solutions containing 6M nitrate or perchlorate ions

(3M NO" as NaNO in 3M HNO or 3M ClO^ as CaClO^ in 3M HCIO^

)

do not show the absorption band for nitrate or perchlorate

ions. This observation indicates that the entire acid molecule

may be extracted rather than only the anions to form species

of the type HNO .HDEHP and HC10,. HDEHP.

76
.0

LjJ 0.8

if)

<

I

Q.

O 0.6

"Z. <

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tr

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c

6

z

o

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Q

O

<

o-HN0

3

A-HCIO4

D-HCI

± _L

2 4 6 8 10 12

ACID C0NC. in AQUEOUS PHASE (M)

Figure 23. Extraction of HC10^ 5 HN0~, and HC1 by HDEHP

.

Further studies are in progress to attempt to elucidate

the mechanism or mechanisms of the extraction of metals into

HDEHP from strong acid solutions.

(I. H. Qureshi, L. T. McClendon and P. D. LaFleur)

77
7. ACTIVATION ANALYSIS LITERATURE SEARCHING FILE

The Analytical Chemistry Division of the National Bureau

of Standards has, for several years, maintained a file for the

activation analysis literature. Each of the some four thousand books, journal articles, reports, theses and conference

proceedings in the file is keyed to each (if appropriate) of

the following five categories

I. Element Determined

II. Matrix Analyzed

III. Technique Used

IV. Nature of publication, language and

country of origin

V. Scope of publication

The specific keys for each category are given in Appendix 2.

The title, authors and location in the literature along

with an identifying number and the appropriate keys, are

entered on magnetic tape. Subsequently a computer search to

identify these items included in a key of a category or combination of keys in the various categories can be accomplished.

A portion of a typical readout is shown in figure 10. For

this listing the following keys were requested: Key 1 - all,

Key 2 - 88, Key 3 - all, Key 4 - all.

It is intended to publish in October, 1968, a complete

bibliography of activation analysis identifying all items in

the literature associated with the specific keys of the first

three categories.

(G. J. Lutz)
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ctivat ion

P. D.

D. A.

E. D.

T. E.

W. D.

F. A.

w. P.

G. W.

B. A.

8. PERSONNEL AND ACTIVITIES

A. Personnel Listing

Activation Analysis Section

Philip D. LaFleur, Section Chief (1/4)

James R. DeVoe, Section Chief (3/4)*

Betty E. Dawson, Secretary (3/4)

Patricia A. Snyder, Secretary - Transferred (1/4)

Ramona Roberts (Summer Worker, Youth Opportunity

Program)

Analysis, Reactor

LaFleur, Project Leader (1)

Becker, Project Leader - Special Project (1)

Anderson - Transferred (1/4)

Gills (1)

Kinard (1)

Lundgren (1/4)

Reed - Transferred (3/4)

Smith (1)

Thompson (3/4)

Patricia Brady (Summer Worker, Youth Opportunity

Program)

Activation Analysis, Cockcroft-Walton Generator

S. S. Nargolwalla, Project Leader and Assistant

Section Chief (1)

M. R. Crambes - Terminated (1/2) NBS Contract, Prance

Paul Black - Terminated (1/4)

E. P. Przybylowicz (1/3) Industrial Research Associate

Eastman Kodak Company

Sheryl Birkhead (Summer Worker, Youth Opportunity

Program)

Activation Analysis, LINAC

G. J. Lutz, Project Leader (1)

D. A. DeSoete - Terminated (1/6) NBS Contract,

Belgium

Diane Setlock - Terminated (1)

Moneta Sherin (Summer Worker, Youth Opportunity

Program)

Radiochemical Separations

P. D. LaPleur, Project Leader

L. T. McClendon - Transferred (3/4)

I. H. Qureshi (1), NBS Contract, Pakistan

*Section Chief of Radiochemical Analysis Section

NOTE: Fractions in parentheses indicate fraction of the year

in this position.

80
B. Publications

G. W. Smith and D. A. Becker, "The Preparation of an NBS

Biological Standard Reference Marerial for Trace Element

Analysis," Proceedings of the Symposium on Nuclear Activation

Techniques in the Life Sciences, International Atomic Energy

Agency, Vienna, 1967 pp. 197-207.

S. S. Nargolwalla, M. R. Crambes and J. R. DeVoe, "A

Technique for the Evaluation of Systematic Errors in the

Activation Analysis for Oxygen with 14 MeV Neutrons," Anal.

Chem. ^0 666 (1968).

F. A. Lundgren and S. S. Nargolwalla "Use of a DualSample-Biaxial Rotating Assembly with a Pneumatic Tube Transfer System for High Precision 14-MeV Neutron Activation Analysis," Anal. Chem. 40, 672 (1968).

G. J. Lutz and D. A. DeSoete, "Determination of Carbon

in Sodium by Photon Activation Analysis," Anal. Chem. 40_

820 (1968).

C. List of Talks

P. D. LaPleur, "The Application of Activation Analysis

to Biomedical Problems," Armed Forces Radiobiology Research

Institute, Bethesda, Maryland, September, 1967.

P. D. LaFleur, "The Application of Activation Analysis to

Biomedical Problems," National Institutes of Arthritis and

Metabolic Diseases Seminar, National Institutes of Health,

Bethesda, Maryland, October, 1967.

S. S. Nargolwalla, "A Technique for the Evaluation of

Systematic Errors in the 14 MeV Neutron Activation Analysis

for Oxygen," Conference on Chemistry and Spectroscopy,

Anaheim, California, October, 1967

.

G. J. Lutz, "Non-Reactor Methods of Activation Analysis,"

(Panel Discussion) Oak Ridge National Laboratory, Gatlinburg,

Tennessee, October 1967.

G. J. Lutz, "Photon Activation Analysis," Greater Washington Area Activation Analysis Council, Washington, D. C.,

November, 1967.

J. R. DeVoe , "Standard Reference Material for Trace Analysis in the Life Sciences," Oak Ridge National Laboratory,

Tennessee, November, 1967.
G. J. Lutz, "The Determination of Carbon in Sodium by

Photon Activation Analysis," (G. J. Lutz and D. A. DeSoete

American Chemical Society, San Francisco, Calif. April, 1968.

P. D. LaPleur, "The Determination of Molybdenum by Activation Analysis," American Chemical Society, San Francisco,

Calif. April, 1967.

B. A. Thompson, "Rapid Group Radiochemical Separation in

the Activation Analysis of Steels," (B. A. Thompson, P. D.

LaFleur) American Chemical Society, San Francisco, April, 196I

J. R. DeVoe, "The Determination of Fluorine by 14-MeV

Neutron Activation Analysis," (J. R. DeVoe and S. S.

Nargolwalla) , American Chemical Society, San Francisco, April

1968.

S. S. Nargolwalla, "Evaluation of NBS 1090 Series for

Oxygen and Nitrogen Content by Several Methods," Ann. Meeting

Div. I, Committee- E-3 , ASTM, NBS, Gaithersburg , Maryland,

April, 1968.

P. D. LaFleur, Chairman, General Papers (two sessions),

Division of Nuclear Chemistry and Technology, American Chemical Society, San Francisco, Calif, April, 1968.

S. S. Nargolwalla, "Current Status of Activation of Trace

Oxygen," a Panel Discussion, 14th Annual Meeting of the

American Nuclear Society in Conjunction with the Canadian

Nuclear Association, Toronto, Canada, June, 1968.

S. S. Nargolwalla, "Self-Absorption of Gamma Photons from

Nuclear Emission and Positron Annihilation in 14 MeV Neutron

Activation Analysis." 14th Annual Meeting of the American

Nuclear Society in Conjunction with the Canadian Nuclear

Association, Toronto, Canada, June, 1968.

82
9 . ACKNOWLEDGMENTS

The Activation Analysis Section wishes to thank Dr. Keith

Marlow, Mr. E. Bebbs, Mr. L. Harris and Mr. R. Vogt of the

Naval Research Laboratory Reactor Facility for making the

irradiation of samples possible. We also wish to acknowledge

the assistance of the NBS Health Physics staff who have helped

us with the safe handling of these samples.

We wish to express our thanks to Dr. R. S. Carter and his

staff of the Reactor Radiations Division for their cooperation in making arrangements for our use of the facilities in

the NBS Reactor Building. Further the assistance of Dr. J.

E. Leiss and staff of the LINAC Radiation Division for arrangements to use the LINAC facilities is gratefully acknowledged. We also wish to thank Dr. Brian Joiner for assistance

in the statistical analysis of experimental data.

We also wish to express our appreciation to Professor

J. Hoste, University of Ghent, Belgium, and Dr. Usmani for

making possible the visit of Doctors DeSoete and Qureshi,

respectively

.

This section acknowledges Mrs. J. R. Gossard for her

assistance in preparing this report.

Special appreciation is expressed to Mrs. B. Dawson who

typed the entire report and whose tireless efforts as section

secretary has made our entire operation more efficient and

effective

.
10. LIST OP REFERENCES

[1] DeVoe, J. R. , editor, NBS Technical Note 404 (1966).

[2] DeVoe, J. R., editor, NBS Technical Note 428 (1967).

[3] Lundgren, P. A. and Nargolwalla, S. S., Anal. Chem. 4_0

762 (1968).

[4] Nargolwalla, S. S. Crambes, M. R. and DeVoe , J. R.,

Anal. Chem. 40, 666 (1968).

[5] Crambes, M. R., Nargolwalla, S. S. and Suddueth, J. E.

Transactions , American Nuclear Society, 11, No. 1, 97

(1968).

Nicholas, D. J. D., and Nason, A., Plant Physiol. 30_,

135 (1955).

Totter, J. R., Burnett, W. T., Monroe, R. A., Whitney,

I. B. and Comar, C. L., Science 118, 555 (1953).

Thompson, B. A. Strause, B. M. and Leboeuf, M. B., Anal.

Chem. 30, 1023 (1958).

Livingston, H. D. and Smith, H., Anal. Chem. 39, 538

(1967).

Webster, P. 0., Brune , D. and Samsahl, K. Inst. J. Appl.

Rad. Isot. 15, 59 (1964).

LaPleur, P. D., PhD Thesis, University of Michigan (1967)

Bowen, H. J. M. , Analyst 92, 124 (1967).

Killick, R. A., Talanta 8, 793 (1961).

Stern, K., J. Phys . Chem. in press . Tromp, R. L., Idaho Nuclear Corp., Idaho Palls, Idaho,

private communication.

Lutz, G. J. and DeSoete, D. A., Anal. Chem. 40, 818

(1968). —

Oka, T. Kato, Nomura, K. and Saito, T., Bull. Chem. Soc

.

Japan, 40, 575-579 (1967).

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

[17]

84
[18] L. A. Currie, Anal. Chem. 4_0, 586 (1.968).

[19] Baes, C. F. Jr., Zingaro, R. A. and Coleman, C. F.,

J. Phys. Chem. 62, 129 (1958).

[20] Hesford, E. and McKay, H. A. C, J. Inorg. Nucl. Chem

13, 156 (I960).

85
APPENDIX 1

Sequencing Action of Programmer

After presetting (a) gas pressures on the main nitrogen

and bleed nitrogen supplies (b) irradiation timer and (c)

total multiscaling time on the analyzer clock timer, the

samples are ready for loading.

Position Home (H ) . In this position the loading-routing

valve (Ld. RV - fig. 7) is in the "load" position, the

sample routing valve (RV - fig. 7) is in sample position #1

and the trigger device (REX) is reset. The programmer is

advanced manually to position #1 on the front panel.

Position #1 . The valve (Ld. RV) is released and returns

to its normal position. A microswitch indicates when this

position is secured and advances the programmer to the next step

Position #2 . The (REX) is reset and advances the programmer to position #3.

Position #3 . The first rabbit is loaded and propelled

into the irradiation assembly. Its arrival there is sensed

by a mercury pressure switch which advances the programmer to

the next step.

Position #4 . The valve Ld. RV is switched to "load"

position and valve RV Is switched to sample position #2.

The second sample is manually loaded and the programmer is

manually advanced to position #5.

Position #5 . In this step the Ld . RV is released and its

return to normal is sensed by the microswitch which advances

the programmer to position #6.

Position #6 . The trigger (REX) Is reset and the programmer is advanced to position #1

.

Position #7 . The second sample is injected into the

second location in the dual-axis irradiation assembly where

its arrival is sensed by a mercury pressure switch and advances

the programmer to the next step.

86
Position #8 . Valve RV is switched to sample position

#1 and the . programmer advances to step #9.

Position #9 . Advances to position #10.

Position #10 . The motor "start" button is pressed. This

initiates the rotation of the irradiation assembly. The programmer is manually advanced to position #11.

Position #11 . Advances to position #12.

Position #12 . In this position the neutron beam is

turned on, the irradiation timer starts the countdown and

2 nitrogen gas at approximately 10 lb f/in is bled into the

rotating-sample assembly. Termination of the preset irradiation time advances the programmer to position #13.

Position #13 . The beam is turned off, and the rotating

sample assembly is given a signal to reverse the motor and

index the assembly to the proper orientation for rabbit

return. The bleed nitrogen is turned off and the irradiation

timer is reset. When the indexing operation is completed the

programmer receives a "pin-in" signal and advances to position

#14.

Position #14 . The first rabbit is returned and the photoelectric gas trigger (PEGT) cuts off the return gas supply

and advances the programmer to position #15. The signal for

gas cut-off is given a fraction of a second before the rabbit

actually arrives at the receiver to reduce damage to the

receiver by heavy samples.

Position #15 . The photoelectric analyzer trigger (PEAT)

,

located at the point of rabbit arrival in the receiver, initiates the counting of the first sample and the trigger (REX)

is reset. After termination of the preset counting time, the

programmer is advanced to the next step.

Position #16 . The detector gate of the analyzer is

closed and the first sample is returned to the irradiation

position. The pressure switch cuts off the gas supply and

advances the programmer to the next position.

87
Position #17 . The valve RV is switched to sample position

#2 and the second sample is returned for counting. The PEGT

turns off the gas and advances the programmer to position #18.

Position #18 . The PEAT initiates the counting of the

second sample for the remaining time on the analyzer clock.

At termination of this count the programmer advances to the

next step.

Position #19 . The second sample is returned to the

irradiation site, the pressure switch turns off the gas and

advances the programmer to position #20.

Position #20 . The valve RV is returned to sample position

#1 and the programmer advances to position #21.

Position #21 . The automatic sequence ends at this point.

The samples can be either unloaded by advancing through steps

#21-to-Home or can be re-irradiated by switching the "recycle"

switch to the recycle mode which causes the programmer to

return to position #10. To remove the samples, the programmer

is manually advanced to position #22.

Position #22 . Sample #1 is returned and the PEAT turns

off the gas and advances the programmer to position #23.

Position #23 . The valve Ld . RV is switched to the loadunload position, the valve RV is switched to sample position

#2. The first sample is manually ejected (via REX) and then

the programmer is manually advanced to position #24.

Position #24 . The valve Ld . RV is switched to the normal

position and the programmer advances to position #25.

Position #25 . Sample #2 is returned and the PEAT turns

off the gas and advances the programmer to Home.

Position Home . The valve Ld . RV switches the loadunload position and sample #2 is ejected manually. The

programmer is now ready for a new cycle operation.

(P. C. Ruegg and M. Stalbird, Radiochemical Analysis

Section, J. E. Suddueth and S. S. Nargolwalla)
APPENDIX 2

Keys for Computer Literature Searching

KEY 1 (ELEMENT TO BE DETERMINED)

1. Actinium Ac

2. Aluminum Al

3. Americium Am

4. Antimony Sb

5. Argon Ar

6. Arsenic As

7. Astatine At

8. Barium Ba

9. Berkelium Bk

10. Beryllium Be

11. Bismuth Bi

12. Boron B

13. Bromine Br

14. Cadmium Cd

15. Calcium Ca

16. Californium Cf

17. Carbon C

18. Cerium Ce

19. Cesium Cs

20. Chlorine CI

21. Chromium Cr

22. Cobalt Co

23. Copper Cu

24. Curium Cm

25. Dysprosium Dy

26. Einsteinium Es

27. Erbium Er

28. Europium Eu

29. Permium Fm

30. Fluorine F

31. Francium Fr

32. Gadolinium Gd

33. Gallium Ga

34. Germanium Ge

35. Gold Au

36. Hafnium Hf

37. Helium He

38. Holmium Ho

39. Hydrogen H

40. Indium In

41. Iodine I

42. Iridium Ir

43. Iron Fe

44. Krypton Kr

45. Lanthanum La

46. Lead Pb

47. Lithium Li

48. Lutetium Lu

49. Magnesium Mg

50. Manganese Mn

51. Mendelevium Md

52. Mercury Hg

53. Molybdenum Mo

54. Neodymium Nd

55. Neon Ne

56. Neptunium Np

57. Nickel Ni

58. Niobium Nb

59. Nitrogen N

60. Nobelium No

61. Osmium Os

62. Oxygen

63. Palladium Pd

64. Phosphorus P

65. Platinum Pt

66. Plutonium Pu

61. Polonium Po

68. Potassium K

69. Praseodymium Pr

70. Promethium Pm

71. Protactinium Pa

72. Radium Ra

73. Radon Rn

74. Rhenium Re

75. Rhodium Rh

76. Rubidium Rb

77. Ruthenium Ru

78. Samarium Sm

79. Scandium Sc

80. Selenium Se

81. Silicon Si

82. Silver Ag

83. Sodium Na

84. Strontium Sr

85. Sulfur S

86. Tantalum Ta

87. Technetium Tc

88. Tellerium Te

89. Terbium Tb

90. Thallium Tl

91. Thorium Th

92. Thulium Tm

89
KEY 1 (ELEMENT TO BE DETERMINED) continued

93. Tin Sn

94. Titanium Ti

95. Tungsten W

96. Uranium u

97. Vanadium V

98. Xenon Xe

99. Ytterbium Yb

100. Yttrium Y

101. Zinc Zn

102. Zirconium Zr

103. Rare earths

104. Actinides

105. Lanthanides

90
KEY 2 (MATRIX ANALYZED)

1,

2.

3,

4,

5.

6.

7.

8,

9.

10,

11.

12,

13.

14,

15.

16,

17.

18,

19.

20.

21,

22,

23.

24,

25.

26,

27.

28,

29.

30,

31.

32,

33.

34,

35.

36,

37.

38,

39.

40,

41,

42,

43.

44,

45

46

47

48

Air, Atmosphere

Archaelogical specimens

Art

general j including virus

blood

urine

other fluids

soft tissue, including hair, nails, and hoofs

bone, teeth

fish

shell fish

seaweed

leaves, needles

wood

other botanical

Textiles

Biological,

Biological

,

Biological

Biological

,

Biological

Biological

Biological

Biological,

Biological

,

Biological

Biological

Biological,

Cellulose - Cement

Chromatography and Ion Exchange - paper, resins, reagents,

etc . Clays

Coal

Corrosion Products

Detergents

Drugs

Dusts

Food

Forensic

,

Forensic

,

Forensic

Forensic

,

Forensic

Glass

Inorganic Compounds (general)

In-stream Analysis

Isotopic Analysis

Liquids, excluding water and sea water

Metals and Alloys (general)

Meteorites and Tektites

Minerals

Ores

Organic Compounds

Organometallic Compounds

Particles

Pesticides

Petroleum and Derivatives

Photographic film and material

Plastics

Process control

Protein

general

hair and fingernails

poisons

gunpowder residue

trace identification

91
KEY 2 (MATRIX ANALYSED) continued

49. Quartz

50. Reactor Materials

51. Reagents

52. Refractories and Ceramics

53. Rocks

54. Sediments, marine

55. Semi-conductor materials

56. Soils - fertilizers

57. Space applications, lunar

58. Stable tracers

59. Steel and Cast Irons

60. Surface analysis

61. Thin films

62. Water

63. Water, sea

64. Well logging

65. Lithium and Its alloys and compounds

66. Ammonium compounds and alkali metals and their alloys and

compounds (excluding lithium)

67. Beryllium and its alloys and compounds

68. Magnesium and its alloys and compounds

69. Calcium, strontium and barium and their alloys and compounds

70. Boron and its alloys and compounds

71. Aluminum

72. Aluminum alloys and compounds

73. Titanium and its alloys and compounds

74. Zirconium and its alloys and compounds

75. Hafnium and its alloys and compounds

76. Niobium and Its alloys and compounds

77. Tantalum and its alloys and compounds

78. Chromium, vanadium and manganese and their alloys and

compounds

79. Molybdenum and its alloys and compounds

80. Tungsten and its alloys and compounds

81. Iron and its alloys and compounds (excluding steels and

cast irons)

82. Cobalt and its alloys and compounds

83. Nickel and its alloys and compounds

84. Copper and its alloys and compounds

85. Zinc and its alloys and compounds

86. Gallium, indium and thallium and their alloys and compounds

87. Cadmium and its alloys and compounds

88. Silver, Gold and Mercury and their alloys and compounds

89. Platinum and its alloys and compounds

90. Rhenium, Ruthenium, Osmium, Rhodium, Iridium and Palladium

and their alloys and compounds

92
KEY 2 (MATRIX ANALYSED) continued

91. Carbon, graphite, diamond

92. Silicon and its alloys and compounds (excluding quartz)

93. Germanium and its alloys and compounds

94. Tin and its alloys and compounds

95. Lead and its alloys and compounds

96. Phosphorus and phosphates

97. Arsenic and Antimony and their alloys and compounds

98. Bismuth and its alloys and compounds

99. Sulfur

100. Selenium and Tellurium and their alloys and compounds

101. Rare earths and their alloys and compounds (including

Sc + Y)

102. Halogens

103. Noble Gases

104. Uranium, Thorium and Plutonium and their alloys and

compounds

105. Fission products

93
KEY 3 (TECHNIQUE USED)

1. Reactor - thermal neutron (n,y) 1

2. Reactor - fast (n,p) (n,a) (n,n ) (n,2n)

3. Reactor - epithermal

4. Isotope Source - neutrons

5. Generator - or sealed tube

6. Accelerator - neutrons

7. Photon Activation (includes Isotope Source)

8. Charge Particle (includes Isotope Source)

9. Secondary Particle

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21. Non-destructive

22. Chemistry - Dissolution Technique

23. Chemistry - Group Separations

24. Chemistry - General

25. Chemistry - Precipitation

26. Chemistry - Distillation

27. Chemistry - Solvent Extraction

28. Chemistry - Chromatography or Ion Exchange

29. Chemistry - Electrodeposition

30. Chmeistry - Isotope Exchange

31. Chemistry - Amalgam Exchange

32. Chemistry - Szilard-Chalmers

33. Chemistry - Substoichiometric

34. Chemistry - Automated

35. Chemistry - Absorption or Adsorption

36. Rapid Radiochemical Separation

37. Isotope Dilution

38.

39.

40.

41. Gamma Sepctrometry

42. Solid State Gamma Spectrometry

43. Beta and Alpha Spectrometry

44. Coincidence Spectrometry

45. Non-discriminatory counting (a, 3, y) but include half

life and absorber measurements, autoradiography,

emulsions

.

46. Neutron Counting

47. Prompt Gamma Counting

94
KEY 3 (TECHNIQUE USED) continued

48.

49.

50.

51. Neutron Flux Determination, includes sample selfshielding and flux perturbations

52. Charge Particle Flux Determination, includes sample selfshielding

53. Photonuclear Flux Determination, includes sample selfshielding

54. Interfering Nuclear Reactions

55. Other errors associated with irradiation

56. Counting errors and corrections

57.

58.

59.

60.

61. Precision-accuracy discussed

62. Sensitivity tables

63. Preconcentration, contamination, collection and handling

techniques

64. Irradiation techniques, sample handling and facilities,

flux monitors

65. Activation analysis standards and standard reference

materials

66. Computer applications and numerical methods

67. Data handling systems

68. Electronics in Activation Analysis

69.

70.

71.

72.

73.

74.

75.

76.

77.

78.

79.

80.

81.

82.

83.

84.

85.

86.

87.

88.

89.

90.

95
AH 1 4

1. Abstract

2. Bibliography

3. Book or book chapter

4. Book review

5. Conference

6. Institute or Course

7. Journal (professional)

8. Journal (trade)

9. Patent

10. Press release (news)

11. Report

12. Thesis

13.

14.

15.

Language

16. English

17. English (translation)

18. German

19. French

20. Russia

21. Japanese

22. Chinese

23. Czechoslovakian

24. Dutch

25. Hungarian

26. Italian

27. Norwegian

28. Polish

29. Portugese

30. Serbo-Croatian

31. Spanish

32. Swedish

33. Rumanian

34. Hindi

35. Ukraninian

36. Arabic

37. Danish

38. Hebrew

39. Korean

40. Finnish

41. Greek

42. Others not listed

Work Done

43. USA

44. UK

45. Russia

46. France

47. Germany

48. Japan

49. Austria

50. Belgium

51. Canada

52. China

53. Czechoslovakia

54. Greece

55. Hungary

56. India

57. Israel

58. Italy

59. Korea

60. Mexico

61. Netherlands

62. Norway

63. Poland

64. Portugal

65. South Africa

66. South America

61. Spain

68. Sweden

69. Taiwan

70. Turkey

71. UAR

72. Yugoslavia

73. Australia

74. Switzerland

75. Rumania

76. Denmark

77. Philippines

78. Ukraine

79. Pakistan

80. New Zealand

81. Bulgaria

82. Finland

83. Vietnam

96

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