NBS Measurement Services:

Research Information Center

fVational Bureau of Standards

Gaitheraburg, Alarykad 20899

Neutron

Source Strength ,

, ,,,, Calibrations

U.S, Department of Commerce

National Bureau of Standards
Center for Radiation Research

The Center for Radiation Research is a major component of the National Measurement Laboratory in the National Bureau of Standards. The Center provides the Nation with standards and measurement services for ionizing

radiation and for ultraviolet, visible, and infrared radiation; coordinates and furnishes essential support

to the National Measurement Support Systemfor ionizing radiation; conducts research in radiation related

fields to develop improved radiation measurement methodology; and generates, conpiles, and critically

evaluates data to meet major national needs. The Center consists of five Divisions and one Group.

Atomic and Plasma Radiation Division

Carries out basic theoretical and experimental research into the • Atomic Spectroscopy

spectroscopic and radiative properties of atoms and highly ionized • Atomic Radiation Data

species; develops well-defined atomic radiation sources as radiometric • Plasma Radiation

or wavelength standards; develops new measurement techniques and

methods for spectral analysis and plasma properties; and collects,

compiles, and critically evaluates spectroscopic data. The Division

consists of the following Groups:

Radiation Physics Division

Provides the central national basis for the measurement of far ultra- • Far UV Physics

violet, soft x-ray, and electron radiation; develops and disseminates • Electron Physics

radiation standards, measurement services, and data for for these radia- • Photon Physics

tions; conducts theoretical and experimental research with electron,

laser, ultraviolet, and soft x-ray radiation for measurement applications; determines fundamental mechanisms of electron and photon interactions with matter; and develops advanced electron- and photon-based

measurement techiques. The Division consists of the following Groups:

Radiometric Physics Division

Provides national measurement standards and support services for ultra- • Spectral Radiometry

violet, visible, and infrared radiation; provides standards dissemination • Spectrophotometry

and measurement quality assurance services; conducts research in optical • Radiometric Measurement Services

radiation, pyrometry, photometry, and quantun radiometry; and develops

spectroradiometric and spectrophotometric standards and calibration

procedures. The Division consists of the following Groups:

Develops,

Radiation

operates,

Source

and

and

improves

Instrumentation

major NBS radiation

Division

facilities • Accelerator

^

Research

including the electron Linac and race track microtron; develops, • Linac Operations

designs, and builds electronic and mechanical instrimentation for • Electronic Instrunentation

radiation programs and facilities; provides national leadership • Mechanical Instrumentation

in the standardization of nuclear Instrinentatlon; and develops new competence in radiation sources and instrjnentation. The

Division consists of the following Groups:

Ionizing Radiation Division

Provides primary national standards, measurement services, and basic

data for applications of ionizing radiation; develops new methods of

chemical and physical dosimetry; conducts theoretical and experimental

research on the fundamental physical and chemical interactions of

ionizing radiation with matter; provides essential standards and

measurement support services to the National Measurement Support

System for Ionizing Radiation; and develops and operates radiation

sources needed to provide primary radiation standards, fields, and

well-characterized beams of radiation for research on radiation

Interactions and for development of measurement methods. The Division

consists of the following Office and Groups:

Office of Radiation Measurement

Radiation Theory

Radiation Chemistry and Chemical

Dosimetry

Neutron Measurements and Research

Neutron Dosimetry

Radioactivity

X-Ray Physics

Dosimetry

Nuclear Physics Group

Engages in forefront research in nuclear and elementary particle physics;

performs highly accurate measurements and theoretical analyses which

probe the structure of nuclear matter; and improves the quantitative

understanding of physical processes that underlie measurement science.
NBS MEASUREMENT SERVICES:

NEUTRON SOURCE STRENGTH

CALIBRATIONS

E. Dale McGarry

Edward W. Boswell

Center for Radiation Research

National Measurement Laboratory

National Bureau of Standards

Gaithersburg, MD 20899

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued March 1988
Library of Congress Catalog Card Number: 88-600510

National Bureau of Standards Special Publication 250-1

Natl. Bur. Stand. (U.S.), Spec. Publ. 250-18, 58 pages (Mar. 1988)

CODEN: XNBSAV

Commercial products— materials and instruments— are identified in tliis document for the sole pur- pose of adequately describing experimental or test procedures. In no event does such identification imply recommendation or endorsement by the National Bureau of Standards of a particular product; nor does it imply that a named material or instrument is necessarily the best available for the purpose

it serves.

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1988

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402-9325
PREFACE

The calibration and related measurement services of the National Bureau

of Standards are intended to assist the makers and users of precision

measuring instruments in achieving the highest possible levels of

accuracy, quality, and productivity. NBS offers over 300 different

calibration, special test, and measurement assurance services. These

services allow customers to directly link their measurement systems to

measurement systems and standards maintained by NBS. These services

are offered to the public and private organizations alike. They are described in NBS Special Publication (SP) 250, NBS Calibration Services

Users Guide .

The Users Guide is being supplemented by a number of special

publications (designated as the "SP 250 Series") that provide a detailed description of the important features of specific NBS

calibration services. These documents provide a description of the:

(1) specifications for the service; (2) design philosophy and theory;

(3) NBS measurement system; (4) NBS operational procedures; (5)

assessment of measurement uncertainty including random and systematic

errors and an error budget; and (6) internal quality control procedures

used by NBS. These documents will present more detail than can be

given in an NBS calibration report, or than is generally allowed in

articles in scientific journals. In the past NBS has published such

information in a variety of ways. This series will help make this type

of information more readily available to the user.

This document ( SP 250-18), NBS Measurement Services: Neutron Source

Strength Calibrations, by E. Dale McGarry and Edward W. Boswell, is the

18th to be published in this new series of special publications. It

describes the calibration of the neutron emission rate of sources of

unknown source strength by use of the manganese sulfate bath method to

compare their strengths to a Ra-Be standard photoneutron source ( see test numbers 44010C and 44020C in the SP 250 Users Guide). Inquiries

concerning the technical content of this document or the specifications

for these services should be directed to the authors or one of the

technical contacts cited in SP 250.

The Center for Radiation Research (CRR) is in the process of publishing

21 documents in this SP 250 series, covering all of the calibration

services offered by CRR. A complete listing of these documents can be

found inside the back cover.

NBS would welcome suggestions on how publications such as these might

be made more useful. Suggestions are also welcome concerning the need

for new calibration services, special tests, and measurement assurance

programs

Joe D. Simmons

Acting Chief

Measurement Services

Chris E. Kuyatt

Director

Center for Radiation Research
ABSTRACT

The manganese sulfate (MnSO^) bath method of neutron source strength

calibration at NBS is described and compared briefly with other MnSO^

bath techniques used internationally. The accuracy of source

calibration is discussed from the viewpoints of international

intercomparisons and practical limitations of the NBS system. In

particular, there is discussion of uncertainties associated with system

limitations and with corrections necessary for neutron capture in the

source, capture of fast and thermal neutrons by competing reactions in

the MnSO^ , capture of neutrons in the source container, and the

correction for leakage of neutrons from the bath, which is 1.27 meters

in diameter.

Key words: calibrations; emission rate; manganese sulfate;

neutron source; source strength determination

iv
TABLE OF CONTENTS

Page

1 . DESCRIPTION OF CALIBRATION SERVICES AND ACCURACIES

1.1 Services Available

1.1.1 Allowable Source Strength Range

1.1.2 Method in General

1.2 Summary of Accuracy

1.2.1 Accuracy of NBS-I Source Strength

1.2.2 Other Uncertainty Components of Interest 2

2. DESIGN PHILOSOPHY 2

2.1 Bath Size and Manganese Concentration 2

2.2 Standard Source Calibrations 2

3. DESCRIPTION OF FACILITIES AND METHODS 4

3.1 Calibration of Sources With Very Different Source Strengths 4 3.2 Corrections to MnSO^ Bath Measurements 9

3.2.1 Neutron Absorption in Oxygen and Sulfur 9

3.2.2 Absorption Corrections for the NBS MnSO^ Bath 9

3.2.3 Neutron Absorption in the Sources and Source Holders 11 3.2.4 Leakage of Neutrons From the Bath 13

3.3 Source Strength Determination 13

3.3.1 Recalibration of MnSO^ Bath 14

4. OVERALL UNCERTAINTY OF A SOURCE STRENGTH MEASUREMENT 14

4.1 Recapitulation of Uncertainty Components 15

4.2 Uncertainty Estimate in Light of Reported 15

Measurements and the ^^^Cf Half-Life

4.3 International Intercomparison of Neutron Source Strength 16

Measurements

4.3.1 Further Discussion 17

5. OPERATIONAL DESCRIPTION OF FACILITY 20

V
5.1 Counting the *®Mn Gamma Rays 20

5.1.1 Scintillators and Photomultipl ier Tubes 20

5.1.2 Preamplifiers 20

5.1.3 Linear Amplifiers 20

5.1.^ Discriminators 20

5.1.5 Scalers 21

5.1.6 Printout Modules 21

5.2 Response Ratio of Counters and System Dead Time 21 5.3 The U.S. National Standard Source Strength, NBS-I 21

6. DATA TAKING AND ANALYSIS 22

6.1 Data Collection 22

6.1.1 Data Collection Monitoring 22

6.2 Data Analyses 23

6.2.1 Fortran Analysis Code: General Concepts 23

6.2.2 Some Limitations of the Analysis Code 24

6.3 Photoproduction 25

7. IMPROVEMENTS IN OPERATIONS BECAUSE OF BETTER NEUTRON AND GAMMA 26

RAY SHIELDING

8. SAFETY 27

9. REFERENCES 28

APPENDIX A: Output From the Mn-56 Data Processing Code A-1

and Example Test Report

APPENDIX B: Computer Code for Processing Raw Counting B-1

Data from the Manganese Sulfate Bath Electronics

APPENDIX C: Californium Source Decay Code Listing C-1

APPENDIX D: Interface of Counting Electronics to Microcomputer D-1

vi
LIST OF FIGURES

Fig. No. Brief Description Page No.

1 Radium Berryllium Photoneutron Source

NBS-I 3

2 Circulating Manganese Sulphate Bath and

Shielded Gamma Ray Detectors 6

3 Photograph of MnSO^ Bath 7

4 Schematic of Nuclear Events in MnS04 8

5 Graph of Results of International 18

Comparison of Source Strength

Measurements

D1 Electric Connections to Unflltered D^l Building Power and Filtered Power from an Uninterruptable Power Supply

vii

1. DESCRIPTION OF CALIBRATION SERVICES AND ACCURACIES

1 . 1 Services Available

The available services are described in the current edition of the

Ionizing Radiation Section of NBS Special Publication 250, "NBS

Calibration Services Users Guide, 1986-1988". Basically, they are as follows:

1.1.1 Allowable Source Strength Range

SP-250 4401 OC applies to calibrations of neutron sources in the range

from 5 X 10^ to 5 x 10' neutrons/second. Such sources may be

calibrated to an uncertainty of about ± ^.^%, depending upon what is

known about their encapsulations. SP-250 44020C applies to sources in

the range 5 x 10' to 5 x 10^ neutrons/second and these may be

calibrated to an uncertainty of about ±^.2%, again with some dependence

on their encapsulations. The quoted uncertainties are at the 685b confidence level.

About two months should be allowed for source calibrations, and advance

arrangements must be made including the following information:

1) A diagram showing the source location in the shipping container and

instructions for removal of the source, if necessary.

2) A description of any special markings on the source.

3) The dimensions of the source, including the relative internal

location of the active ingredients.

4) The nature and amount of radioactive materials and the ratio of

neutron producing ingredients.

5) The kind of metal enclosing the source and, if possible, the number

of grams of each element.

6) The date the source was sealed.

1.1.2 General Method

Emission rates (neutrons/second) of neutron sources of unknown source strength are determined by the Manganese Sulfate Bath Method. At NBS,

the neutron sources are calibrated by comparing their strengths to a Ra-Be photoneutron source known as NBS-I. A comparison of source strengths is made by activating a manganese sulfate bath solution and

continuously counting the induced, saturated ^^Mn radioactivity with a scintillation counter.

1 . 2 Summary of Accuracy

1.2.1 Accuracy of NBS-I Source Strength

The present emission rate of NBS-I, which is absolutely determined, is

1.243E+06 neutrons/second with an estimated uncertainty of ± 0.85^ (one

Sigma). See Section 2.2 for discussion of this uncertainty.

Uncertainties in this document refer to either one standard deviation

(experimental) or estimates of non-random uncertainties that have the

character {68% confidence limit) of one standard deviation.

1
1.2.2 Other Uncertainty Components of Interest

1) Depending upon the activity of the source, different scintillation

counters are used. The use of separate counters for high level

(>2x10® n/s) sources introduces an additional O.H% uncertainty because

of the methods of calibration. See Section 3.1 for discussion of

calibrations of the "main" and "remote" counters.

2) Corrections (always less than five percent total) are made for

neutron absorption in the source itself. See Sections 3.2.3 and 3.2.4

for detailed discussion of these leakage and absorption corrections.

3) The half-life of the principal neutron-emitting isotope in Cf

neutron sources, ^^^Cf, is 2.645 ± 0.008 years. The next most

significant isotope is ^^^Cf with a half-life of 50 years. If the

composition of the source is limited to no more than 3% ^^°Cf, it will

not contribute more than a fraction of a percent to the neutron

strength even 10 years after separation of the californium. See

Section 4 for further discussion of a possible source-dependent halflife.

2. DESIGN PHILOSOPHY

The design philosophies that dominate the operation and achievable

accuracy of the neutron source-strength calibration service are discussed in the following paragraphs. Perhaps the most notable

characteristic of the NBS MnSO^ bath calibration method is that it is

the only such calibration in the world based entirely on relative

measurements of unknown source strengths against a known standard Ra-Be

(n,Y) source, NBS-I (see Fig. 1). All other MnSO^ facilities calibrate

by determination of absolute ^^Mn activity.

2. 1 Bath Size and Manganese Concentration

Sources are calibrated by comparison with NBS-I in a large spherical

tank, 1.27m in diameter, containing MnS04 solution with a density of

1.37 kg/1 of solution. Calibrations depend upon measurements of gamma

rays from the activity induced in manganese through the capture of

neutrons. Corrections to the bath activity for fast neutron capture by

oxygen, sulfur and teflon, as well as escape from the bath, all require

knowledge of the source spectrum. The correction for absorption by the source itself, which in some cases leads to fission, requires detailed

knowledge of the isotopic content of the source material and the

weights and thickness of all encapsulations.

The neutron sources are suspended at the center of the bath until

equilibrium of the ^^Mn activity is reached. This takes about 25

hours. The source is enclosed in a teflon cylindrical shell which

creates a void in the manganese sulfate that serves to minimize

absorption of thermal neutrons by the source.

2.2 Standard Source Calibrations

The absolute emission rate of NBS-I has been measured by three

independent methods. See references 1,2, and 3 for reports of these

2
3
calibrations. In the first calibration, the thermal neutron density

was determined from the activity induced in thin indium and magnesium

foils as a function of distance from the source when both the source

and foils were under water. The second calibration involved the

capture of neutrons by a surrounding manganese sulfate (MnSO„) bath,

followed by a measurement of the activity of the manganese-56 . The

third method involved a relative comparison to an antimony-beryllium

source which had been calibrated absolutely in a heavy-water manganese

sulfate bath. The final value of NBS-I was determined from the results

of these measurements in June 1961 and was 1.257 x 10^ n/s ±^%.

Subsequent to this, the emission rate has been checked against the

number of neutrons of ^^^Cf that are emitted per fission, v. The

uncertainty was reduced to ±0.85$:

As the half life of radium is 1 600±5 years, the emission rate of the

standard can be accurately calculated over a long period of time.

Table 1 gives the emission rate since 1976. As mentioned, the emission

rates of sources are determined by comparison with NBS-I in the MnSO^

bath. Table 1 is particularly significant in that only the values

listed there have been used by NBS for the source strength of NBS-I

since 1976, even though some discussions of a possible ±0.35$ bias

exists in the literature. See bottom of Table 8 and Ref. (4). The

present (September, 1986) emission rate of NBS-I is 1.243 x 10^

neutrons/second with an estimated uncertainty of ±0.85$.

3. DESCRIPTION OF FACILITIES AND METHODS

Figure 2 schematically shows the bath, the remotely located

scintillation counters, and various pumps and radiation shields. For

calibration, the sources are located at the center of the spherical

bath - see Figure 3. The spherical tank is aluminum, lined completely

with 2 mm of polyethylene to prevent long-term interaction of the

acidic MnSO^ solution with the aluminum. The bath contains nominally

1050 liters of MnSO^ at a solution density of 1.37 kg/1 of solution.

The bath solution is circulated through plastic tubing to a scintillation counter, located outside of a polyethylene-lined,

high-density-concrete shielding wall.

3 . 1 Calibration of Sources With Very Different Source Strengths

A factor of 10,000 in source strength range is spanned by using two

scintillation counters that differ in sensitivity by a factor of 70.

The choice of counter depends upon the counting rate; all source strengths are compared to the NBS-I rate.

Details of the operations of the counters and calibration of their

response are discussed in Section 6. Only the more sensitive of the

two counters can be directly calibrated with NBS-I. An additional

multiplicative factor of 70, and its uncertainty, are required to

relate the secondary (or "remote") counter's calibration to that of the

first. Quality assurance procedures are necessary to insure the long

term stability of this ratio. Originally it was planned to use the

half life (2.645 years) of ^^^Cf as a measure of quality control by

following the decay of ^^^Cf sources over three to four half lives.

4
TABLE 1

NBS-1 EMISSION RATE TABLE BASED ON THE CALIBRATION OF 1,257E£

IN JUNc. 1961 AND A HALF LIFE OF 1600 YcARS

1976 1977 1978 1979 4 #%A^ 1980

JAN 1.2491E+06 1 2485E+06 4 OAA^pj.y\y

1 « 2480Et06 l»2475E+06 1.2469E+06

FEB l,2490E+06 1 •2485Et06 1 * 2480Er06 l»2474E+06 1.2469E+06

MAR 1 2490E+06 1 * 24dDEtOo 1 * 2479hT06 4 A ^ A ^ 1 JK. t 1 2474E+06 1 •2468E'f06

APR 1 2489E+06 4 ^JftAJlP^7\/^ 1 •2484Et06 1 2479E+06 4 A *4 t y^ ^ l«2473E+06 1 •2468E'i-06

MAY 1 2489E+06 1 2484E+06 1 2478E+06 1 .2473E+06 1 .2467E+06

JUN 1 •2489E+06 1 «2483E+06 1 2478E+06 1 2472E+06 l«2467E+06

JUL 1 2488E+06 1 2483E+06 1 •2477E+06 1 .2472E+06 1.2467E+06

AUG 1 2488E+06 1 2482E+06 1 2477E+06 1 2471E+06 l*2466E-f06

SEP 1 2487E+06 1 2482E+06 4 ^ A Tt y ^ 1 ^ y 1 2476E+06 l»2471E+06 1 • 2466E>06

OCT 1 2487E+06 1 .2481E+06 4 ^% A ^ y ^ 1 yv y 1 •2476Et06 1 2471E+06 1 .2465E+06

NOV 1 2486E+06 1 •2481E+06 4 ^ A *9 y r* 1 /\ y 1 2476E+06 1 .2470E+06 1.2465E+06

DEC 1 2486E+06 1 24S0Et06 1 2475E+06 1 2470E+06 l#2464E+06

1981 1982 1983 4 An A 1984 1985

JAN 1.2464E+06 1 •2458E+06 1 2453E+06 l»2448E+06 1.2442E+06

FEB l*2463E+06 1 .2458E+06 1 2453E+06 1.2447E+06 1.2442E+06

MAR 1 2463E+06 1 2458E+06 1 •2452E+06 A A A *'ft^' B A y 1 .2447E+06 ^ ^% A A ^ A A 1 2441E+06

APR 1 2462E+06 1 2457E+06 1 « 2452E+06 A ^% A A > M. ^ 1 2446E+06 A 9^ AAA • A A 1 .2441E+06

MAY 1.24&2E+0A 1 .2457E+06 1 2451E+06 1 .2446E+06 1.2440E+06

JUN 1 24A2E+06 1 2456E+06 1 .2451E+06 lA A A • Ak A 1 2445E+06 1 .2440E+06

JUL 1 •2461E+06 1 2456E+06 4 A CT A^ 1 yv y 1 2450E+06 1 2445E+06 1 . 2440E+06

AUG l»2461E+06 1 •2455E+06 A A ^» yv y 1 2450E+06 1 2444Ef06 1.2439E+06

SEP 1.2460E+06 1 •2455Et06 1 2449E+06 A ^% AAA ^* 1 t 1 •2444E+06 l»2439E+06

OCT 1 2460E+06 1 2454tT06 1 • 244yE+06 4 AAA 1 # 1 .2444E+06 1 .2438E+06

Noy 1.2459E+06 ^ ^% A A 4 yV ^ 1 2454E+06 A A yv y 1 .2449E+06 A A A f • yv * 1 2443E+06 1 .243SE+06

DEC 1.2459E+06 1 2453E+06 4 ^AAOPJ./\y

1 • 2448Et06 4 A A A *T >v y 1 2443E+06 1 .2437E+06

1986 1987 1988 4 AAA 1989 1990

JAN 1 •2437E+06 1.2431E+06 1.2426E+06 1 2421ct06 4 ^\ A 4 P yv y 1 •2415E+06

FEB 1 .2436E+06 1.2431E+06 1.2426E+06 1.2420E+06 1.2415E+06

MAR 1.2436E+06 1.2431E+06 1.2425E+06 1.2420Eh06 l,2414E+06

APR 1.2435E+06 1.2430E+06 1.2425E+06 1.2419Ef06 1.2414E+06

MAY 1 .2435E+06 1.2430E+06 1.2424E+06 1 .2419E+06 1.2414E+06

JUN 1.2435E+06 1 .2429E+06 1.2424E+06 1 .2418E+06 l,2413E+06

JUL 1.2434E+06 1.2429E+06 1.2423E+06 1.2418E+06 1.2413E+06

AUG 1.2434E+06 1 .2428E+06 1.2423E+06 1 .2418E+06 1.2412E+06

SEP 1 .2433E+06 l,2428E+06 1.2422E+06 1.2417E+06 1.2412E+06

OCT 1 .2433E+06 l,2427E+06 1 .2422E+06 l«2417E+06 1 .2411E+06

NOV 1 2432E+06 1.2427E+06 1 ,2422E-f06 1 .2416E+06 1 .2411E+06

DEC 1 .2432E+06 1.2427E+06 1.2421E+06 1 .2416E+06 1 .2410E+06

5

FIG. 3. A photograph of the aluminum shell which supports the

polyethylene liner and MnSO/^ solution. Sources are pulled into the

center of the solution by a Teflon can attached to a rope on a pulley,

above, and a short steel bar at the bottom of the inside of the

spherical tank.

7
7 ^UJ

CO

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UJ UJ

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(0

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Cl, CO 0) 8
However, there is now sufficient evidence (5) to show that different

^'^Cf sources exhibit measurably different "effective" ^^^Cf half lives

in the range of 2.635 to 2.657 years. Consequently, quality control

procedures are related to measurements of effective ^^^Cf half lives

for about five older NBS sources.

3.2 Corrections to MnSO^ Bath Measurements

Ideally, the neutrons emitted from a source located at the center of

the MnSO^ solution enter the bath, are slowed down by a series of

collisions, and finally captured by a *^Mn nucleus to produce ^^Mn. In

the laboratory, we do not achieve this ideal situation and a number of

small (several percent) corrections have to be made. Figure ^ shows

the different neutron loss processes which take place in the MnS04

bath.

3.2.1 Neutron Absorption in Oxygen and Sulfur

Oxygen and sulfur are both present with the manganese in MnS04. Table

2 gives relative concentrations for solutions with three different

densities. The density of a saturated MnSO^ solution is 1.^65 g/cm^' at

20 °C. The presence of oxygen (in both water and the MnSO^) causes significant absorption of neutrons above 4 MeV, primarily by the ^^0

(n,a)^^C reaction. Sulfur also absorbs neutrons above 2 MeV. In

addition, sulfur absorbs neutrons in the thermal and epithermal (E>0.63

eV) energy range. See Ref. (6), for NBS calculations of absorption

corrections by W. Murphey.

3.2.2 Absorption Corrections for the NBS MnSO^ Bath

The corrections currently used at NBS for neutron absorptions in oxygen

and sulfur are based upon several studies. One is a Monte Carlo

calculation performed by E. J. Axton, National Physical Laboratory,

(NPL), Teddington, England. Another is from an extrapolation of

transport calculations, performed for the Electric Power Research

Institute, (EPRI), by Goldstein and Lin Chen at Columbia University

(7). EPRI, as part of v of ^^^Cf measurements, examined correction

factors applied to MnSO^ bath measurements. Results are presented in

Tables 3 through 5.

Table 2 provides relationships among various factors in those tables.

The Columbia results (given in Table 3) address only ^^^Cf neutrons but

consider differences in both the densities of MnS04 solutions and bath

radii. The Axton results (given in Table 5) examine different types of

neutron sources, some with significantly different energy spectra, but

only for an NBS-type bath, i.e., 63.5-cm radius and 1.37^ kg/L density.

From an examination of the data in Table 3, it is concluded that the

results from the "infinite medium, 1.382 g/cm^" case are essentially

the NBS-bath situation. Therefore, these data are converted, in Table

4, into the units of Table 5 by multiplying by either the concentration

of oxygen or sulfur, as appropriate. The comparison is mentioned in

footnote #1 of Table 5.

9
TABLE 2. Atom Densities of Elements in Each Composition of the MnSO^

Solutions Referred to in Tables 3 and

Density (g/cm') 1 .382 1 .257 1.093^

N^/Nj^^ 35.47 55.65 162.15

Amount of MnSO^ 320.7 231.3 93.68

(g/kg solution)

Concentrations (in units of nuclei/barn-cra)

C 6.269-2* 6.il52-2 6.624-2

c" 3.843-2 3.690-2 3.475-2

Cj; 1.768-3 1 .159-3 4.085-4

C^" 1.771-3 1.161-3 4.090-4

*Read 6.269 x 10 _2

TABLE 3. Impurity Absorption in Various Size Baths and Different

Concentrations of MnSO^ . The Table Assumes a ^^^Cf Fission Spectrum.

(See Ref. 7)

Type & Energy Absorption Rates for Indicated Densities

Range of Reaction 1 .382 g/cm^ 1.257 g/cm^ 1 .0934 g/cm^

Infinite Medium

0(n,a) fast 1.059

0(n,p) fast 5.406

S(n,a) E>0.63 eV 7.043

S(n,a) Thermal 2.012

S(n,p) E>0.63 eV 7.033

S(n,p) Thermal 4.059

52-cm sphere

0(n,a) fast 1.045

0(n,p) fast 5.264

S(n,a) E>0.63 eV 6.989

S(n,a) Thermal 2.011

S(n,p) E>0.63 eV 6.958

S(n,p) Thermal 4.047

25-cm sphere

0(n,a) fast 8.888

0(n,p) fast 4.161

S(n,a) E>0.63 eV 6.I38

S(n,a) Thermal 1.722

S(n,p) E>0.63 eV 6.048

S(n,p) Thermal 3-466

1 1 .060-1 1 .071-1

4 5.518-4 5.704-4

1 6.981-1 6.967-1

1 2.461 -1 3.584-1

1 7.006-1 7.039-1

4 4.963-4 7.229-4

1 1 .046-1 1 .056-1

4 5.363-4 5.527-4

1 6.920-1 6.891-1

1 2.444-1 3.329-1

1 6.929-1 6.941-1

4 4.930-4 6.728-4

2 8.874-2 8.901 -2

4 4.205-4 4.278-4

1 6.069-1 6.030-1

1 2,070-1 2.775-1

1 6.010-1 5.994-1

4 4.175-4 5.608-4

10
TABLE 4. Absorption Rates per Source Neutron for Elements Other Than

Manganese in the NBS MnS04 Bath Assuming a Concentration Density of

1.374 kg/L and a ^^^Cf Fission Neutron-Energy Spectrum. Bath is 1.27 m

in Diameter (See Ref. 7).

Type and Energy

Range of Reaction Absorption Rates (per source neutron)

Total Percentage

0(n,a) fast 4.054 X 10-' 60. 05? 0(n,p) fast 2.069 X 10-^ 0.3

S(n,a) E>0.63 eV 1 . 204 X 10-' 17.4

S(n,a) Thermal 3.440 X lO-** 4.9

S(n,p) E>0.63 1 .203 X 10-' 17.4

S(n,p) Thermal 6.941 X 10-^ 0.0

6.826 X 10-' (100.0)

C = 3.828 X 10-^ nuclei/barn-cm; C = 1.710 x 10-' nuclei/barn-cm

(refer to Table 2)

See Table 5 for the Axton results and a comparison with Tables 3 and 4.

3.2.3 Neutron Absorption in the Sources and Source Holders

The correction considered here is to account for the reduction of the

manganese activity due to the loss of thermal ized neutrons absorbed in

the neutron source itself.

1 ) Effects of surrounding the source in the MnSO^ solution with a void. There are two problems associated with placing a bare neutron

source directly into the MnSO^ solution: (1) the MnSO^ solution is

sufficiently acidic to interact with the source encapsulation metals;

(2) the amount of thermal-neutron absorption by the source is dependent

upon the size of the void surrounding the source, because the albedo of

the MnSO^ is constant and the neutron flux within the void is

proportional to the flux at the surface of a void surrounding the source. Consequently, moderate voids (400cm' to 800cm') around the

source are used in essentially all MnSO^ baths to protect the source

and reduce the neutron absorption.

2) Corrections for different types of sources : A calculation of the

thermal neutron self-absorption for cylindrical or spherical neutron

sources has been made(6). The calculations are confirmed by the

experimentally measured difference in the manganese sulfate bath

activity for bare and cadmium-covered Pu-Be and Am-Be neutron sources. The calculation is done in single-interaction approximation and assumes

that the incident thermal neutron flux is isotropic. The source material may be fissionable and be covered by up to three cladding

materials. A computer program has been written for the numerical

calculations. A comparison of the calculations with experimental

results is given in Table 6.

11
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12
Table 5. Results of Intercomparison Between Calculation and

Measurement of Source Absorption

Calculated difference between

bare and cadmium covered

source absorption

Experimentally measured

difference (from bath

irradiations)

Pu-Be-B AM-Be

i%) (.%)

2.08 i|.06 1.34

1.93+0.03 4.05±0.1 1.44±0.08

Pu-Be-A

3.2.4 Leakage of Neutrons From the Bath

A correction is necessary for neutrons which escape from the bath. In

principle, the larger the bath the less that escape. However, making

the bath too large has compensating disadvantages. In particular, the

specific activity of the solution decreases with increasing radius.

See Table 5 for leakage corrections.

3.3 SOURCE STRENGTH DETERMINATION

The source strength, S, in neutrons per second emitted into ^ir geometry

of the bath is,

S =

^^Mn Counter

Factor when

>1 .000

Net count rate

of customer's

source in MnSO,

Corrections for

leakage &

capture for

customer's source

Source strength

of NBS-I at

calibration date

Net count rate

of NBS-I in bath

on calibration date

Corrections for

leakage and

capture for

NBS-I

where all factors are fairly obvious except the first parenthesis in the

numerator, which is the main-to-remote counter ratio.

As a representative example. Section 3.3-1 describes a check on the

calibration of the NBS bath after it had been shut down for shielding

modifications in 1985. The check was made using a Savannah River (SR)

^^^Cf source SR-Cf-144. The percent correction to the MnS04

calibrations of that source for oxygen and sulfur neutron capture is

(0.62 ± 0.08)%; for neutron capture in the Teflon beaker which holds the source during immersion in the bath, the correction is (0.17 ± 0.06)$;

for fast plus thermal leakage of neutrons from the bath, the correction

is (0.045 ±0.010)5t and for source absorption of thermal neutrons is

13
(0.08 ± 0.03)%. The uncertainties of these four quantities are estimates that are intended to have the character of one standard

deviation and are based upon the following: 1) for fast neutron capture

in sulfur and oxygen, the uncertainty stems primarily from the

differences between the Columbia and the NPL results; 2) for capture in

Teflon, the uncertainty relates to nuclear cross section uncertainties

and the complex geometry of the Teflon structure (i.e., effective

thickness); 3) for leakage, which is quite small for the NBS bath, the

correction is estimated to be uncertain by 20%; for source

absorption, the uncertainty comes from the thermal absorption studies of

Spiegel and Murphey at NBS (13).

When the four corrections are added together, this gives a total

correction factor in the numerator of 1.0092 ± .0010. The uncertainty

is the quadrature sum of the four quoted uncertainties. Similar

corrections for NBS-I give a correction factor in the denominator of

1.0021 ± 0.0008. The factor for NBS-I is smaller because the neutron

spectrum is less energetic and fast capture and leakage are smaller.

The resulting net correction factor is 1.0071 ± .0013-

3.3.1 Recalibration of MnSO^ Bath

On 17 July 1986, the NBS MnSO^ bath was officially placed back into

operation, following extensive modifications in the radiation shielding

and external source handling capabilities. Because of reduced

background at the ^^Mn counters, the operation point of the system was changed to decrease slightly (0.155^) the dependence of counting rate on gain shift. This resulted in a new operating point; i.e., a new value

of counts per second of NBS-I on the "MAIN" counter. To recalibrate the

system, the source SR-Cf-144, previously involved in the international

comparison counting, (see Section ^.3) was remeasured, and the results

were as follows:

1 ) Date of Recalibration of SR-Cf-1 ^4 : 17 JULY 1986 (198th day)

^ ^ [ul'll f ofy * (1.007U0.0013) (1.2^13'^ x 10^ ± 0.85^?)

S = 5.261 X 10^ ± 0.935^, at a 68^ confidence level

This is to be compared to a decay-corrected source strength of 5.240 x 10^ n/s on 17 July 1986 based upon the 20 February 1983 value of (1.270

± 0.012)x10' n/s .

3) Comparison: 5.261/5.240 =-1.0040

4. OVERALL UNCERTAINTY OF A SOURCE STRENGTH MEASUREMENT

It is instructive to bring the various aspects of the source-strength

calibration procedure together in an example to see how the final

uncertainty is derived. One interesting example is that for a singly-encapsulated ^^^Cf source fabricated at ORNL and used for a

14
variety of measurements at NBS in the years 1976 - 198^. This source is

identified as NS-100. The uncertainty estimated for the Cf-252 source

NS-100 is ±1.1? do). The uncertainty is derived as follows.

4 . 1 Recapitulation of Uncertainty Components

NS-100 was calibrated by comparing its strength to that of NBS-I.

The emission rate of NBS-I was at that time 1.245 x 10^ neutron/second

with an estimated uncertainty of ±0.85?.

There are four fractional uncertainty components which make up a ±0.63?

uncertainty attributed to the MnSO^ bath measurements of Cf source

NS-100 relative to NBS-I. These uncertainties have been observed to be

somewhat larger than would be predicted by statistics alone. Although

gross counting statistics are usually <0.1?, there are three factors

which control the limits of uncertainty:

1) for low counting rates (e.g., NBS-I counts 178.3 ops on the more sensitive crystal), a time variable background of a few counts per

second limits reproducibility to ±0.3?;

2) for high counting rates (> 3000 cps), electronic gain instabilities

limit reproducibility to about ±0.35?;

3) for strong sources like NS-100 (>10® neutrons/second), the less

sensitive crystal is used thereby introducing the additional

multiplicative factor of 70 with a ±0.4? uncertainty.

Finally, there is an additional ±0.13? uncertainty on the corrections

for leakage and absorption (see Table 5). These four components, taken

in quadrature, yield the ±0.63? uncertainty mentioned above.

Therefore, the resultant uncertainty of the ^^^Cf source NS-100 is the

quadrature sura of 0.85? and 0.63? or 1.06?. Table 7 summarizes these

uncertainties.

4.2 Uncertainty Estimate in Light of Reported Measurements and the

^^^Cf Half Life

It is worth noting that five determinations of the NS-100 source strength have been made at NBS in the period 15 May 1979 to 26 July

1984. These measurements when fitted to Y = A exp(-Bt) for ^^^Cf decay

give a weighted-fit uncertainty of ±0.5? which is consistent with an average half life of (2.645 ±0.007) years. The maximum-to-minimum ratio

of the fitted and measured results is 1.0088. If this ratio is

interpreted as an estimate of the two-sigma uncertainty interval, even

the outer lying values are consistent with a 68? confidence level of

±0.5?.

15
Table 7. Summary of Uncertainties Associated with Californium

Neutron Source Strength Calibrations

Source Strength NBS-I ±0 .85% 3

* Main-to-Remote Counter Response Ratio ±0 .H0% s Fast neutron capture by oxygen and sulfur ±0 .08% s for the Cf neutrons

Capture in Teflon for the Cf neutrons ±0 .06% 3

Leakage of Cf neutrons ±0 .0]% S

Cf Source absorption of thermal neutrons ±0 .03% 3

Counting imprecision (Cf source) caused ±0 .35% r by gain drift

Counting imprecision for NBS-I which is ±0 .30% r dominated by time variability of the

background

Capture and leakage for NBS-I +0 .08% 3

Combined uncertainties (in quadrature) = ±1.06^ (68% confidence)

* r = random

s = non -random

4.3 International Inter comparison of Neutron Source Strength

Measurements

A previous intercomparison of neutron source emission rates was based on measurements of a Ra-Be(a,n) source. The source was circulated to

eleven laboratories between 1959 and 1965, and the results were published by V. Naggiar in 1966 (14). The results showed a total spread

of 3.7%, and the reported uncertainties varied from ± 0.9% to ± 3.0%.

Over the following decade significant improvements in the accuracy of

neutron source measurements were achieved. It was therefore decided

that a new intercomparison should be arranged. After some discussion of

various types of sources, a ^^^Cf source was chosen as being the most

suitable. The source could be made small, the neutron spectrum is such

that corrections for fast neutron losses would be small, and the low

gamma-ray emission allows for easy transportation around the world.

The intercomparison, begun in 1977, was concluded in 1986. E. J. Axton,

NPL, has written a report to be published soon in Metrologia (Ref. 10).

Figure 5 is an Axton summary of results from that intercomparison.

Table 8 compares the NBS result to the world average.

Before considering Table 8, some discussion of how the data were selected is necessary. The evaluation in Table 8 considers only the

data from Ref. 10 that relate to measurements of neutron source SR-Cf-144 by different laboratories which use the MnSO^ technique.

Fig. 5 is taken from Ref. 10 and shows 21 data points representing

measurements from 14 laboratories. Only the 17 data points below which

the symbol "Mn" appears use MnS0^. Note that PTB is, therefore, not

included in Table 8. Of the 17 laboratories activating MnS0^, only 10

measured the same (SR-Cf-144) neutron source. However, the ASMW result

16
was assumed to be biased and was also excluded.

Of the remaining results, multiple data points from any laboratory were averaged to yield the values listed in Table 8. The NBS results were treated somewhat differently, however, because the very first NBS data

point on Fig. 9 represents NBS measurements made in 1978 prior to

circulation of the source. The later three NBS values, which are 1983

measurements, were averaged (see footnote 1 to Table 8) to produce the

second NBS result in Table 8.

4.3.1 Further Discussion

Comments are necessary on two items related to Table 8. First, the

reported total uncertainties on the NBS values are larger, in most cases by factors of 2 or 3, than uncertainties reported by other

laboratories. As indicated by the last footnote to Table 8, this is

due to the ±0.85% uncertainty assigned to NBS-I. If one extracts 0.85?

in quadrature from the NBS uncertainties, what remains is about ±0.4?

uncertainty indicating that the precision of the NBS calibrations is

essentially the same as other laboratories. The issue here is that the

NBS results are dependent upon calibrations of NBS-I that are about

20 years old. This could be changed by recalibration of NBS-I; but to

be worthwhile, the effort should reduce the uncertainty on NBS-I by a factor of 3 or more and that will require substantial effort. Periodic

reviews of the situation fail to justifiy this recalibration.

Second, the total uncertainty on the measurement of the SR-Cf-144

source strength are smaller than the ±1.1? typically reported for

customer's sources. This is a result of: (1) smaller uncertainties on corrections for structural effects and isotopic composition, because

the source due to its intended international exposure was carefully

selected for known characteristics; and (2) because the source strength

selected for convenience of shipping could be calibrated at NBS, both

in 1978 and 1983, without the need for the remote counter assembly, and

therefore, the uncertainty is also free of the uncertainty on the ratio

factor.

17
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18
Table 8. A Review of the Most Recent International Source Strength

Intel—Comparison (see Ref. 10).

Uncertainties ( in percent)

Result (xlO^n/s) (at a 6Q% confidence level)

1 NBS (1978) 2.09557 0.945

2 BIPM 2.098U 0.322

3 ENEA 2.11161 O.i^OH

4 LMRI 2.1iJ190** 0.791

5 IMM 2.11347 0.423

6 VGK 2.10430 0.366

7 ETL 2.11225 0.379

8 NPL 2.09653 0.292

9 NBS* (1983) 2.09277*** 0.952****

Footnotes:

* NBS ( 1983) value; (see Ref. j_0 and j_22

2.09154 X 10^ n/s 0.944%

2.09016 " 0.960%

2.09662 " 0.952%

Average = 2.09277±0.00278

(i.e., reproducibility is ±0.13%).

This average value is for an arbitrary date used in Ref. 10. When

corrected for ^^^Cf decay, it corresponds to the source strength of

5.24 X 10^ n/s on 7/17/86 as referred to in Sect. 3.3.1.

** Examination of above tabulated results (x1 O^n/s)

Unweighted Average = (all values) 2.10745±0.01529 (0 ) (±0.725%)

^

Unweighted Average = (excluding 2.14239) 2. 10308±0.00842 (0 ) (±0.400%) ^

*** Comparison of world average with NBS 1 978 and 1 983 values

- 1.001.93 While 2J0308 . ,_,(,3„

2.09277 2.09557

 Uncertainty on NBS results versus other values

The uncertainty of the NBS measurements is due mainly to the ±0.85%

uncertainty in the value of the NBS-I , radium-beryllium, reference

source. See discussion in Section 1.2.1.

19
5. OPERATIONAL DESCRIPTION OF FACILITY

The manganese sulfate bath method of neutron source calibration at the

NBS involves mechanical manipulations necessary to position either

NBS-I or an unknown source into the bath for measurements, electronics

operations necessary to obtain a comparison of the ^^Mn counting rates,

and finally a complete description of data analyses from which a final

neutron source strength is derived. The following operations begin

when the source has been in the bath long enough for the ^®Mn to reach

equilibrium. The discussion of methods will start with electronics

operations.

5. 1 Counting the ^^Mn Gamma Rays

Electronics for the main and remote crystal are identical. The

following paragraphs describe the components and the settings used in

normal operations.

5.1.1 Scintillators and Photomultiplier Tubes

The photomultiplier tubes are Bicron-selected 85^23 and require about

1000 volts positive voltage. The scintillator and photomultiplier are

in a factory-sealed container. The high voltage is supplied by a single HV unit with dual output. The dials on the high voltage unit

should be set so that the meter shows 1.11 kV.

5.1.2 Preamplifiers

The preamps are ORTEC Model 113s and are set at 200 picofarad input

capacitance. They feed negative input pulses less than one microsecond

wide to two amplifier channels.

5.1.3 Linear Amplifiers

The amplifiers are ORTEC 485s which have been modified to have 0.25

microsecond time constants. The gains are set at about 8 coarse and 6

fine gain so that the desired ^^Mn peak (846.9 keV) is in channel 316

and a '^"Cs peak (662 keV)i3 in channel 247, of 512 channels. The

positive unipolar output pulses are about 1 .5 microseconds wide and all

the negative undershoot pulses are restored to the baseline by about

3.2 microseconds.

5.1.4 Discriminators The amplifiers are fed to constant-dead-time

discriminators, built at NBS, with settings as follows: Input offset

is OFF. The 2-20 microsecond dead-time scale is set at about 90 so that the dead-time output pulse is 3.4 microseconds wide on the scope screen and results in a total dead time of 3-5 microseconds. The

outputs are labelled as "Dead Time Count Output". The discriminator

output pulse of 0.5 microseconds width is routed to the scalers. The

discriminators are set to match channel 37, which corresponds to a gamma-ray energy of about 100 keV.

20
5.1.5 Scalers

All scalars are contained in a single Tennelec module, which is a tinner

and triple scalar. The scalar channels are A,B and C. A & B are the

main readout, with A being the most-significant-digit overflow from B. C is for the remote output.

5.1.6 Printout Modules

Printout is controlled by a Tennelec 588 Printout Control. See Appendix

D on Interconnection of Electronics for more details on output to a microcomputer.

5.2 Response Ratio of Counters and System Dead Time

Weaker sources between 5x10^ to 2x10® n/s are counted with the main

crystal and larger sources with the remote crystal. The main-to-remote

crystal counting ratio is dependent upon the dead time of the system.

This dead time is non-extendable. That is, amplifier pulses shaped to

have shorter time durations than the set discriminator time interval,

and which appear during the set (or fixed) dead time, do not lengthen

the set time interval.

The main-to-remote crystal counting ratio is determined by observing

the counting-rate ratio of the two counters for a source strength of

about 5 X 10® n/s. The counting rates are corrected for a fixed

dead-time of 3.^ microseconds plus 0.1 microseconds for electronics

later in the chain.

The system response for other counting rates, higher and lower, is

checked by observing the decay of ^®Mn with a half-life of 15^^.71

minutes. This is accomplished by allowing a source of appropriate

strength to reach equilibrium in the bath and then cutting off the flow

to the counters and observing the exponential decay.

5.3 Thi U-S. National Standard Source Strength, NBS-I

A Ra-Be (Y,n) source was selected as the standard because of its 1600

year half life. For comparison, Ra-Be (a,n) sources do not have such

simple time histories since their strength depends upon other factors

than the amounts of radium and beryllium present (8). A Ra-Be (a,n) source has an initial growth of about 0.5 percent per year. In brief,

the NBS Standard Ra-Be (Y,n) source, NBS-I, consists of a beryllium

sphere, 4 cm in diameter, at the center of which a one curie capsule of

RaBrj is placed (see Figure 1). As only gamma rays can enter the

beryllium, the neutron source strength is governed by the known

exponential decrease of Ra-226

Two nearly identical radium-beryllium photo-neutron sources have been

constructed to serve as standards for the Bureau. The radium in both

sources was initially enclosed in platinum-ir idium capsules of 0.2 mm wall thickness. One capsule developed a leak and was subsequently

21
enclosed in Monel of 1 -mm thickness (9). The source having the

original capsule (NBS-I) has been chosen as the primary standard for

the absolute calibration. It has had an aluminum protective jacket

placed around it. The other source is known as NBS-II. The source

strength ratio of the two sources is 0.9^±0.01.

6. DATA TAKING AND ANALYSIS

The radioactivity of the ^^Mn is sampled at saturation by a continuous

flow system at a location outside of the primary radiation shielding

for the MnS04 bath. There are two sodium-iodide scintillation counters

at this remote location. One, identified as the "main" counter is a 2"

X 2" crystal mounted crystal-end down in a Marinelli metal beaker

through which the MnSO^ solution is pumped. This beaker is positioned

inside of a lead cave. Attached tightly to the beaker by two large

"hose" clamps is a pipe which contains a second scintillation crystal,

also 2" X 2", positioned on its side at the end of the pipe. This

second or "remote" counter is held in the pipe by an adjustable

positioning mechanism so that the ratio of the counting rate in the two

crystals can be varied by about 30%. Nominally the present ratio

between them is 70. The remote crystal is also surrounded by lead.

6 . 1 Data Collection

The counting data are accumulated in scalars connected to permit

accumulation of up to 10® counts. The counters are connected together

with a time and date clock, and interval timer, to a read out mechanism

connected by an RS-232 line to a Professional 350 (PRO-350) DEC

computer. This electronics is on an uninterruptable power supply

which, in event of a power failure, will keep the system in operation

long enough to record the fact that a power failure occured and record

the current data.

The RS-232 interface is operated in the File Transfer Mode of the

normal DEC operating system during data collection. Functionally, this means that from the Main Menu of the PRO-350, the File Transfer is

selected and a name is assigned by the user to an ASCII file. The

PRO-350 then waits until the counter electronics sends data and then

the PRO-350 places it in the file and returns to the waiting state for

further data. The process can be terminated at any time by the user. The data file may be viewed with the normal File Services routines of

the PRO-350 or it may be printed by the normal Print Services routines.

6.1.1 Data Collection Monitoring

The essential task of data monitoring is that of assuring that the gain

of the data collection channel does not change. To monitor this gain,

the signal from the channel (i.e., main or remote) is sent to a multichannel analyzer. The characteristic spectrum of the voltage

pulse height distribution from the output of the linear amplifier

(which is also fed to one of the discriminators) is a distribution of

pulses from about 50 keV, the typical noise level, to about 1 .2 MeV.

The peak from the ^^Mn activity is at 846.9 keV. Section 5.1.'4 gives

22
the details for setting the electronics and the discriminator. The

position of the ** Mn peak is periodically checked by the operator and

manual adjustments to the amplifier gain are made as necessary. After

acquiring some experience with the system, gain is controllable to

about ±0.3? depending somewhat upon the counting rate. The effect of

gain setting on the average of two measurements taken at two different

times has an estimated uncertainty of ± 0.35%.

6.2 Data Analyses

The analysis of the counting data normally takes place in two separate

operations. The first is analysis of the raw data to obtain a best

average value of the ^®Mn count rate for a specific set of data. These

data are corrected for resolving time loss primarily in the 3.5

microsecond fixed-dead time discriminators, source decay during data

acquisition (when necessary) , and background. The latter is taken

after a source has been placed into the bath but before the flow to the

counters is turned on. This is convenient because it requires about 25

hours for the ^^Mn activity level to reach saturation. Also note that,

if a source with a strength of greater than 8x10^ n/s has been in the

bath recently, the background will be a function of time (primarily

because of 14. 29-day ^^P created by the ^^S(n,p) reaction). This means background measurements must be taken before and after the source

measur ement

Also note that normally there are periods of several weeks between

source measurements. Therefore, in addition to taking data for the source which is to be calibrated, the bath must be re-calibrated

against NBS-I, for which background measurements are very important.

Currently, the background is nominally ^ .8% of the count rate for

NBS-I.

6.2.1 Fortran Analysis Code ; General Cone epts

This first part of the data analyses is accomplished using FORTRAN code

ANALYZE. FTN (see Appendix B for listing and example output). The code

performs the following operations:

1) The code derives an "uncorrected" average value of the individual

results for the preset counting-time interval. The uncorrected

notation means not corrected for background.

2) From this average, the code determines what the uncertainty would

be if it were based solely on Poisson statistics of the number of

counts. This is the "expected standard deviation." The code then

finds the observed square root of the variance about the mean

value. This is the "observed standard deviation" about the mean.

3) The program provides the background corrected mean and the count

rate in counts per second.

23
4) From the larger of the above-mentioned uncertainties and the number

of observations, the code determines the uncertainty of the mean

count rate.

5) The code lists the system dead-time (or counting loss) correction,

and the background rate.

6) The code gives the fraction of observed counts which lie outside of

both one sigma and three sigma of the mean.

7) If desired, the code will recompute a revised average and a revised

standard deviation by eliminating all observations outside of three

Sigma. This option is primarily for use when there is trouble with

the system. For example, suppose source measurement were accomplished over a weekend and in the last few hours one of the

channels, say a scaler, failed. It is easy to eliminate the bad

data using this option.

8) The code computes the main-to-remote counter ratio. Also as a matter of convenience, the code computes the ratio of both the main

and remote count rates to an input best-estimate of the current

count rate of NBS-I. Note, one does not always know the precise

value for NBS-I at the time of data processing so these latter

ratios are for a quick reference only.

6.2.2 Some Limitations of the Analysis Code

1) All counting time intervals must be the same. The counting time

interval is assumed to be in multiples of tenths of a second and

must be the first output parameter for each observation. The code

computes the counting time interval as DELTA = C(1)/10.0.

2) The same FORTRAN program is used to process background measurements

as well as source strength calibration data. It asks whether or not the data to be processed refer to a background measurement. If

the answer is yes, the code uses the same algorithm but assumes a negligibly small "background" to be subtracted from the measured

background data.

3) The user must input the dead-time in microseconds. This is the

value set on the fixed dead-time discriminators. There is currently

only one value for this in the code so the fixed dead times in both

counting channels must be set the same.

4) The uncertainty of the mean is more complicated than alluded to

above. After deciding on the larger of the Poissonian and observed

deviations, the value is divided by the square root of the number

of observations. This is then added in quadrature to 0.15? to form

a quantity called TEMP. The 0.15? reflects the current uncertainty

associated with gain instabilities.

24
5) Finally, the following are computed:

TN = (TEMP/1 00) *(mean count rate)

TB = 0.06*(mean background rate)

ERR = SQRT (TN^ + TB^

)

where: TN is the absolute, as opposed to relative, uncertainty on the

average counting rate; TB is the uncertainty on a variable background,

and is taken to be 6% of the instantaneously observed background (see

discussion below); ERR is the quantity printed out as the uncertainty

of the mean counting rate.

Although counting statistics on a long background determination (3 to 4 counts per second) may be considerably less than 6% (say 0.3%), there

is frequently ^^P activity in the bath from the '^S(n,p)^2p reaction.

During a one-day determination of background, there will be a decay of

5%. On the other hand, short-term counting of background yields

nominally ^ .5% statistics, if there are no gain shifts or sources moved

in the vicinity of the equipment. Consequently, if 6% is conserative,

it is not so by more than a factor of two and this would translate to

about 0.^5% uncertain in the source strength determination.

6. 3 Photoproduction

De Volpi (11) performed an experiment in his MnSO^ bath with a radium

bromide pellet of about one curie (without a beryllium shell). First,

to check the shielding of his continuous flow counter, he placed the

pellet into the bath but did not turn the flow on. Basically there was

not an increase at the counter. Next he placed the radium bromide

pellet in the bath, turned the flow on and observed an apparent neutron

yield of 3.0 x 10"* n/sec. Finally, he placed the pellet in a thick

beryllium shell and this, in turn, into the bath and measured 1.16 x 10^ neutrons/ second. Therefore, without the beryllium shell he had seen a (2.6 ± 0.^%) response. De Volpi asserts that very little of

that observed signal can be from photoneutrons from the deuterium

component of the bath or from structural materials. However, he

asserts that some may be due to (a,n) reactions from radium a's on the

two bromine isotopes in the pellet.

Since NBS-I (and II) both contain radium bromide (RaBr2), we must

consider what effect all this has on our calibration procedure. NBS-I

was calibrated, at least once, against a Sb-Be(Y,n) source and whether

the neutrons come from (a,n) reactions on beryllium or (a,n) reactions

on bromine only matters when it is necessary to know something about

the neutron energy spectrum from NBS-I. The (a,n) neutrons will be of

higher energy so the leakage from the bath could be larger. However,

since the fraction of these is already small, the effect is assumed to

be negligible.

The conclusion from these attempts to measure photoproduction is that

no correction for photofission or the (a,n) neutrons is necessary for

the NBS procedures.

25
7. IMPROVEMENTS IN OPERATIONS BECAUSE OF BETTER NEUTRON AND GAMMA-RAY

SHIELDING

Two areas of improvement have resulted from the installation of better

neutron and gamma shielding. Previously, scintillation counters could

be activated by exposure to neutrons. The background of the

5 cm X 5 cm cylindrical Nal crystal is nominally 3 counts per second.

Activation by the source increased this by a factor of four. There are

two distinct components to the decay: that of 25 minute iodine-128 and

that associated with 15 hour sodium-2'4. In roughly four hours after

exposure, the background activity was reduced to about 30$ more than

normal. This residual then decayed with the 15 hour half-life. The

improved shielding appears to have eliminated this crystal activation

problem for neutron sources up to about 10^ n/second.

The second area of improvement is that associated with gamma background

from a neutron source in the bath or the handling of NBS-I which

contains one gram of radium. To first establish a basis for what could

be attained, measurements of background with four different size sodium

iodide crystals were made in a low-background, lead-shielded

environment. See Table 9.

TABLE 9

Data to Establish A Realistic But Low Level Background for Sodium

Scintillation Counts at NBS MnSO^ Bath

Crystal Observed Ratio Predicted Ratio

Dimension Relative background background background^ observed to

( inches) volume (counts/s) per volume (counts/s) predicted

1x1

1/2 x 2x2

4x^4

1 1/2

1 3.38

8

64

0.39

1 .Oil 2.4

16.5

0.39

0.31

0.30

0.25

0.26

0.87

2.06

16.5

1 .50

1 .20

1 .17

1 .0

For comparison before the recent improvements in shielding, and with

NBS-I in the bath (but with no flow to the counters) and no other

sources in the room, the 1 1/2" x 1 1/2" crystal had a background of

about 5 cps and the 2" x 2" crystal about 11 cps. Subsequent to the new

shielding, the backgrounds in the 2" x 2" crystals (now in use) are in

the vicinity of 3.7 cps. This is a factor of three improvement although

the background is still 50% above that of a radiation free area. The

significance in the improvement, however, is seen from the fact that

previously the background-to-signal ratio was 11/148 = 0.074. Now that

ratio is 3.7/1 48 = 0.025, that is, only 2.555 of the response to NBS-I is

background. It takes less effort now to accurately establish counter

background when sources are in the bath.

'Based on high-quality, well-shielded 4x4 crystal background of 16.5 cps

and reductions per relative volume.

26
8. SAFETY

The calibration of neutron sources involves several different

safety aspects:

1 ) The radiation safety aspect emphasizes minimization of

personnel exposure. Because there are no hot cells at NBS, the

magnitude of neutron source strengths that can be safely handled

is limited to 10^° n/s, or less. This means that many hours of

close proximity exposure would be necessary to produce a lethal

dose of radiation. Consequently, emphasis is upon as small an exposure as practical.

2) The other aspects are safe handling of neutron sources

to prevent any damage and industrial safety practices when

handling heavy shielding materials, shipping casks, and the

removable parts of shipping containers.

With regard to radiation safety, NRC and NBS regulations require

that all personnel handling neutron sources be given a radiation

safety and awareness training course. This training is

essentially the same as that required by the NBS reactor.

Therefore, the training requirement for neutron source handling

is satisified every two years by attendance at the Reactor

Health Physics course.

Safe handling of neutron sources and the industrial safety

aspects are taught through an apprentice-type relationship with

each new handler.

All neutron-source transfer operations at NBS are accomplished

by trained professionals with the cognizance of, and frequently

with the help of, Health Physics personnel. Temporary,

in-transit, source storage is accomplished with moveable water

tanks and shielding barrels. Procedures are reviewed prior to

each handling operation. Each participant must wear an albedo-type neutron dosimetry badge, a gamma badge, and pocket

dosimeter. The latter serves as a device for periodically

estimating doses during an operation. Frequently, in those

situations where sources are to be removed from a unfamiliar

surrounding, or for in-air source transfers, audiable-signal

dosimeters are also used.

27
9. REFERENCES

1. J. A. DeJuren, D. W. Padgett, and L. F. Curtiss, J. Res. NBS 40, 63

(1955).

2. J. A. DeJuren and J. Chin, J. Res. NBS 40, 311 (1955).

3. R. H. Noyce, E. R. Mosburg, Jr., J. B. Garfinkel, and R. S.

Caswell, "Absolute Calibration of the National Bureau of Standards

Photoneutron Source-Ill, Absorption in a Heavy Water Solution of

Manganese Sulfate," Reactor Sci. Technol. (J. Nucl. Energy, Part

A/B) VJ_, 31 3 (1963).

4. E. J. Axton, P. Cross, and J. C. Robertson, "Calibration of the NPL

Standard Ra-Be Photoneutron Sources by an Improved Manganese

Sulfate Bath Technique," Jour, of Nucl. Energy, Parts A/B, Vol. 19,

pp. 409 to 422 (1965).

5. K. W. Geiger, "Recent Improvements in the Absolute Calibration of

Neutron Sources," Metrologia, 4, No, 1, pp. 8-14, (1968).

6. W. M. Murphey, "The Correction Factor for Fast Neutron Reactions on Sulfur and Oxygen in the Manganese-Sulfate-Bath Calibration of

Neutron Sources," Nucl. Instr. and Methods, 37, 13 (1965).

7. H. Goldstein and L. Chen, "Preliminary Calculations on Fast Neutron

Absorption Corrections to the MnSO^-Bath Technique", EPRI Report

RP-707-3, 10 April 1979.

8. V. Spiegel, "Neutron Source Calibrations at NBS for Calibration

Checks of Neutron Radiation Instruments," Proc. of Symposium on Measurements for the Safe Use of Radiation, NBS Special Publication

456, p. 87, (1976).

9. R. L. Walker, U. S. Atomic Energy Commission Document MDDC 41 4, Oct

22 (1964).

10. E.J. Axton, "Intercomparison of Neutron Source Emission Rates

(1979-1984)", Metrologia 23, 129-144 (1986/87).

11. A. De Volpi and K. G. Porges, "Absolute Calibration of Neutron

Sources Having a Wide Range of Emission Spectra", Metrologia, CVol.

5, No. 4 (1969).

12. E.D. McGarry, V. Spiegel and Lee Linpei, "BIPM Com Cons. Etalons

Mes. Ray. lonisants (Section I), 7, (1985).

13. V. Spiegel, Jr. and W. M. Murphey, "Calibration of Thermal Neutron

Absorption in Cylindrical and Spherical Neutron Sources,"

Metrologia, 7, 34 (1971 ).

28
V. Naggiar, Rapport sur la comparaison internationale de la mesure

du taux d' emission de la soure de neutrons Ra-Be (a,n) du Conseil

National de Recherches n 200-1 par la methode de ralentissement des

neutrons dans une solution de sulfate de manganese, _in Recueil de

Travaux de BIPM, Vol. 1 , 1966-1967.

29

APPENDIX A - Output from the Mn-56 Data Processing Code and Example Test

Report

riLEMAMI 18 EDl.LOa

THI RAN COUIITIMa DATA MIRK («!• la la aacoadm)!

1 «0. 0. lt7627. 101136. 92. 11. 4.48.

2 40. 0. 187429. 100293. — 92. 11. 3.28.

3 «0. 0. 187334. 100833. 92. 11. «. 8. « «0. 0. 1B3B41. 98798. 92. 11. 6.48.

5 40. 0. 182312. 9840C. 92. 11. 7.28.

S 40. 0. 187830. 100472. 92. 11. 8. 8. 7 40. 0. 187480. 997S2. 92. 11. 8.48.

UMBER or coiniTS- 7 THI EXPERIMENT HAS STARTED OH APRIL 2. 198fi

MAI I COUITIR RESULTS ******************** Thm UBcorrao^d aaaa of all tha data Is Its axpactad standard daviatlea (in X) is Its obsarrad standard dSTiation (In k> Is

Ttaa correetad saaa is la COUNTS PER SECOND it Is Tha uacartaiaty oa tha saan (in X) is Systas daad tisa la Blcrosacoads was

Tha parcant counting-less eorractlon was

Tha backgrouad (in cps) was Tha parcant of background in tha nat count was

Tha fraction of counts outsida of ona std. dav. was

Tha fraction of counts outsida of 3 std. dav. was X SN 190738.77 3.09 190334.09 2.62 190683.30 2.92 186846.64 -3.90 183473.98 -9.03 190968.39 3.37 190606.81 2.74 Rayisad avaraga axeluding counts outsida 3 sigaa is Its ravlsad standard daviation (in X) is

189413.172

0.230

1.194 189403.172

4733.079 0.476 3.300

1.663 10.000

0.003 1.000

0.371

190614.730 0.034

REMOTE COUNTER RESULTS

aAAft AAAAAAAAAAA AAA^AAA Tha uncorractad saan of all tha data is Its ezpectad standard daviation (in X> ia Its obsarvad standard daviation (in X) ii

100839.766 0.313

1.036

Tha corractad saan is 100834.266

Is COUNTS PER SECOND it is 2520.837 Tha uncartainty on tha saan (ia X> is 0.420 Systaa daad tisa in sicrosaconds was 3.300 Tha parcant counting-loss eorractlon was 0.890 Tha background (in cps) was 3. 500 Tha parcant of background In tha nat count was O.OOS

The fraction of counts outsida of ona std. dav. was 0.8S7 Tha fraction of counts outsida of 3 std. dev. was 0.429

X SH 102038,.98 3.78

1011B2,,96 1.08

:oi-'32..59 2.81

936J3.,54 -3.72

99260.,69 -4.97

101363.,12 1.63 100640.,31 -0.63 Revised average excluding counts outside 3 slgma is Its revised standard deviation < in X) is 101229.797

0. 449 RATIO OF MAIN/REMOTE counter response 1.878 Reference value for SBS-I was

M*in--.i-N=S-I ratio is Rea)C^e-t:-S3£-: ratio is

148. 200

31 . 951 17.013

Al
UNITED STATES DEPARTMENT OF COMMERCE

National Bureau of Standards

Gaithersburg, Maryland 2D899

REPORT OF CALIBRATION

Test No. 536-98765-4 Date: 13 May 1985

SUBMITTED BY: ABCDE Corporation

FOR: John P. Doe

9999 S. South Avenue

Anywhere, US 66666

DESCRIPTION OF NEUTRON SOURCE:

Nominally a 50 microgram Cf-252 source. Assumed source encapsulation equivalent to source

NBS-108. Isotopic composition as follows:

Cf-250 ]2.750%

Cf-252 77.410%

Cf-254 0.00]%

CALIBRATION: The source described above has been calibrated by

comparing its strength to that of the NBS primary Ra-Be photoneutron

standard source, "NBS-1." The neutron emission rate of the submitted

source was found to be 1.088 X 10® neutrons/sec. The error is

estimated as 1.3% standard error. September 16, 1984 is the reference

calibration date.

EXPERIMENTAL METHOD: The comparison of source strengths was made by

activating a manganese sulfate bath and continuously counting the

induced, saturated manganese-55 activity with a scintillatin counter.

The source was located at the center of a 1.2 m diameter spherical bath

in a small teflon cavity. The bath was circulated to the scintillation

counter, which was located in a shielded, stainless-steel beaker. The

following corrections have been applied: 0.63% for fast neutron

capture by oxygen and sulfur in the bath, 0.13% for neutron capture by

fluorine in the teflon source holder, 0.05% for escape from the bath,

and 0.29% for thermal neutron absorption in the source. The

calibration data is recored on 259 in data book No. 15. The present

emission rate of NBS-1, which is absolutely determined, is 1.245 x 10^

neutrons/second with an assigned uncertainty of ± 0.85%.

This calibration was performed by

For the Director:

Chief, Ionizing Radiation Division

A2 Ionizing Radiation Division
APPENDIX B - Computer Code for Processing Raw Counting Data from

the Manganese Sulfate Bath Electronics

PROGRAM ANALYZE. FTN

CHARACTER AN1 , AN2 , AN3 , AN4 , AN5 , INFILE* 1 2 , OUFI LE* 1 2 , M0NTH*9

REAL C(8) ,CMAIN( 100) .CREMOTdOO) ,NB , DTIME( 1 00 ) ,SECOND( 100)

REAL X(IOO) .LAMBDA, SW( 100) ,TX( 100) ,C0UT(2) ,NBS1 ,RNBS(2)

INTEGER DAY, YEAR, PASS

WRITE (5,*) 'What is the name of the input file?'

READ (6,'(A)' ) INFILE

WRITE (5,*) 'What is the name of the output file?'

READ (6, '(A)') OUFILE

OPEN( UNIT=3 , FILE=INFILE , STATUS= ' OLD '

)

OPEN( UNIT=i| , FILE=0UFILE , STATUS= ' NEW' )

WRITE (i1, 1000) INFILE

1000 FORMAT (il7X, 'FILENAME IS ',12A)

WRITE(il,1001 )

1 001 FORMAT

)

WRITE(4,1002)

1002 FORMAT (17X, 'THE RAW COUNTING DATA WERE (time is in seconds):')

WRITE(4,*)

WRITE(4,*)

N0=0

READ(3,*)

READ(3,1003)

1003 F0RMAT(18X)

10 READ (3,100i|,END=20) (C(I),I = 1,8)

100^4 FORMAT ( 4 (F7.0,3X) ,F6 . 0 , 3X, 3F2. 0 ) N0= NO + 1 WRITE (4, 1005) N0,C(1 )/10. ,(C(I),I=2,8)

1005 FORMATd 1 X, 13 ,5X,F7 . 0 , ilX ,F2 . 0 , MX ,F8 . 0 , 4X, F8 . 0 , J|X,F4 . 0 .^IX, 3F3 . 0 ) CMAIN(N0)=C(3) + C(2) * 1.0E07

CREM0T(N0)=C(4)

IF (NO .EQ. 1 ) THEN

DAY= ININT(C(5))

DELTAT=C( 1 )/10.

END IF

SECOND(N0)=C(8) + 3600. * C(6) + 60. * C(7)

GO TO 10

20 WRITE(4,*)

WRITE(il,*)

WRITE(M,1006) NO

1006 F0RMAT(22X, 'NUMBER OF COUNTS= ',l4)

WRITE(5,*) 'Is this a Cf-252 source (Y or N)?'

READ(6,' (A)' ) AN1

IF (AN1 .EQ. 'Y') THEN

CF2=1

ELSE

CF2=0.

END IF

WRITE(5,*) 'Is this a satur-ation measurement of NBS-1 (Y or N)?'

Bl
PROGRAM ANALYZE. FTN

READ (6 ,

' (A) • ) AN2

IF (AN2 .EQ. 'Y') THEN

NB=1 . ELSE

NB=0.

END IF

WRITE(5,*) 'What is the current value of NBS-I in CPS?'

READ(6,*) NBS1

WRITE(5,*) 'Input the deadtime in microseconds:'

READ(6,*) TAU

TAU= TAU * 1 .OE-6

WRITE(5,*) 'What is the current year?'

READ(6,*) YEAR

CALL CHANGE (DAY, MONTH, I DAY, YEAR)

WRITE(4

WRITE (4, 1007) MONTH, I DAY, YEAR

1007 F0RMAT(22X, ' THE EXPERIMENT WAS STARTED ON ' , A9 , 1 X , 12 ,

' , ',I4)

TINC=0.

DO 30 1=1 ,N0

IF (I .EQ. 1 ) THEN

DTIME(I)= 0.

ELSE

IF (SECOND(I) .LT. SECOND(I-I)) TINC= TINC + 86400.

DTIME(I)= SECOND(I) + TINC - SECOND( 1

)

END IF

30 CONTINUE

DO 90 PASS=1 ,2

WRITE(5,*) 'Is this a background measurement (Y or N)?'

READ(6 ,

' (A) ' ) AN3

IF (AN3 .EQ. 'Y') THEN

IF (PASS .EQ. 1 ) THEN

BKG= 0.003

ELSE

BKG= 0.001

ENDIF

ELSE

WRITE(5,*) 'Input the background in "CPS":'

READ(6,*) BKG

END IF

DO 40 1=1 ,N0

IF (PASS .EQ. 1 ) THEN

X(I)= CMAIN(I)

ELSE

X(I)= CREMOT(I)

END IF

40 CONTINUE

B2
PROGRAM ANALYZE. FTN

BAK= BKG * DELTAT

DTZ= TAU / DELTAT

DO 50 1 = 1 ,N0

X(I)= X(I) / (1 - X(I) * DTZ)

50 CONTINUE

LAMBDA= AL0G(2.) / (2.6^15 * 365.25 * 8.64E4)

IF (CF2 .EQ. 1 ) THEN

DO 60 1 = 1 ,N0

X(I)= X(I) - BAK

X(I) = X(I) » EXP(LAMBDA » DTIME(I))

X(I) = X(I) + BAK

60 CONTINUE

END IF

CALL ECALC(NO,X,AVE,SIG,STD)

NX= 1 CALL 0TSIDE(N0,NX,AVE,X,SW,TX,K0UT1 ,JT1

)

NX = 3

CALL OTSI DE ( NO , NX , A VE , X , SW , TX , K0UT3 , JT3

)

CZERO= AVE / DELTAT

CTLOSS= 100. * ((1. / (1. - CZERO * TAU)) - 1.)

CAVE= AVE - BAK

C0UT(PASS)= CAVE

CPS= CAVE / DELTAT

RNBS(PASS)= CPS/NBS1

FRACT1= K0UT1 / FLOAT(NO)

FRACT3= K0UT3 / FLOAT (NO)

IF (STD .GT. SIG) THEN

EX=STD

ELSE

EX=SIG

END IF

TEMP= EX / SQRT ( FLOAT ( NO )

)

TEMP= SQRT (TEMP ** 2 + 0.15 ** 2)

TN= (TEMP / 100. ) * CPS

TB= 0.06 * BKG

ERR= SQRT(TN ** 2 + TB ** 2)

ERR= (ERR / CPS) * 100.

PBKG= (BKG * 100.) / AVE

WRITE(M,*)

WRITE(5,*)

WRITE (4,*)

WRITE (5,*)

B3
PROGRAM ANALYZE. FTN

IF (PASS .EQ. 1 ) THEN

WRITE(4,1008)

WRITE(M,1009)

WRITE(5,1008)

WRITE(5,1009)

ELSE

WRITE(i4,1010)

WRITE(M,101 1 ) WRITE(5,1010)

WRITE(5,101 1 ) END IF

F0RMAT(22X, 'MAIN COUNTER RESULTS')

F0RMAT(22X, ' **********^********* '

)

FORMAT (22X, 'REMOTE COUNTER RESULTS')

F0RMAT(22X,

)

WRITE (4 1012) AVE

WRITE (4 ,101 3) SIG

WRITE (4 1014) STD

WRITE(i| ,*)

WRITE (4 r1015) CAVE

WRITE (4 ,1016) CPS

WRITE (i4 ,1017) ERR

WRITE(4 ,1018) TAU * 1 .0E6

WRITE (4 ,1019 ) CTLOSS

WRITE (4 ,1020) BKG

WRITE(4 ,1021 ) PBKG

WRITE (4 ,1022) FRACT1

WRITE (4 ,1023) FRACT3

WRITE(5 ,1012) AVE

WRITE (5 ,1013) SIG

WRITE(5 ,1014) STD

WRITE(5 ,*)

WRITE(5 ,1015) CAVE

WRITE (5 ,1016) CPS

WRITE(5 ,1017) ERR

WRITE(5 ,1018) TAU * 1 .0E6

WRITE(5 ,1019) CTLOSS

WRITE(5 ,1020) BKG

WRITE(5 ,1021 ) PBKG

WRITE(5 ,1022) FRACT1

WRITE (5 ,1023) FRACT3

B4
PROGRAM ANALYZE. FTN

1012 F0RMAT(12X, 'The uncorrected mean of all the data is ',F25.3)

1013 F0RMAT(12X,'Its expected standard deviation (in %) is ',F23.3)

1014 F0RMAT(12X, 'Its observed standard deviation (in %) is ',F23.3)

1015 F0RMAT(12X, 'The corrected mean is ',F43.3)

1016 F0RMAT(12X, 'In COUNTS PER SECOND it is ',F38.3)

1017 F0RMAT(12X,'The uncertainty on the mean (in %) is ',F27.3)

1018 F0RMAT(12X, 'System dead time in microseconds was ',F28.3)

1019 F0RMAT(12X,'The percent counting-loss correction was ',F24.3)

1020 F0RMAT(12X, 'The background (in cps) was ',F37.3)

1021 F0RMAT(12X,'The percent of background in the net count was ' & ,F18.3)

1022 FORMAT (12X, 'The fraction of counts outside of one std. dev. was

& ,F13.3)

1023 FORMAT (12X, 'The fraction of counts outside of 3 std. dev. was ' & ,F15.3)

WRITE(5,*)

WRITE(5,*)

WRITE(5,*) 'Do you want a listing of the corrected counts and ', & 'their distribution'

WRITE(5,*) 'relative to the average (Y or N)?'

READ(6, ' (A) ' ) AN4

IF (AN4 .EQ. 'Y') CALL PEXTRA(NO , X, SW)

WRITE (5,*) 'Do you want a revised average of the data excluding'

WRITE(5,*) 'points outside of 3 sigma (Y or N)?'

READ(6,' (A)' ) AN5

IF (AN5 .EQ. 'Y') THEN

CALL ECALC(JT3,TX,AVE,SIG,STD)

WRITE(M,*)

WRITE(4,102M) AVE

WRITE(4,1025) STD

1024 FORMATd 2X, 'Revised average excluding counts outside 3

& 'Sigma is ' ,F13.3)

1025 F0RMAT(12X, 'Its revised standard deviation (in %) is ',F24.3)

END IF

90 CONTINUE

WRITE (4,*)

WRITE(4,1026) C0UT(1) / C0UT(2)

1026 FORMATd 2X, 'RATIO OF MAIN/REMOTE counter response ',F27.3)

WRITE(4,*)

WRITE(4,1027) NBS1

WRITE(4,1028) RNBS(1)

WRITE(4,1029) RNBS(2)

1027 F0RMAT(12X, 'Reference value for NBS-I was ',F35.3)

1028 FORMATd 2X, 'Main-to-NBS-I ratio is ',F42.3)

1029 FORMAT ( 1 2X, 'Remote-to-NBS-I ratio is ',F40.3)

END

B5
PROGRAM ANALYZE. FTN

SUBROUTINE CHANGE( DAY, MONTH , IDAY , YEAR)

DETERMINE MONTH AND DAY OF THE MONTH WHEN GIVEN THE DAY OF THE YEAR

CHARACTER*9 MONTH

INTEGER DAY, YEAR

IF (DAY .LE. 31 ) THEN

MONTH= 'JANUARY'

IDAY= DAY

END IF

IF (IM0D(YEAR,4) .NE. 0) THEN

IF (DAY .GT. 31 .AND. DAY .LE. 59) THEN

M0NTH= 'FEBRUARY'

IDAY= DAY-31

END IF

IF (DAY .GT. 59 .AND. DAY .LE. 90) THEN

MONTH= 'MARCH'

IDAY= DAY-59

END IF

IF (DAY .GT. 90 .AND. DAY .LE. 120) THEN

MONTH= 'APRIL'

IDAY= DAY-90

END IF

IF (DAY .GT. 120 .AND. DAY .LE. 151) THEN

MONTH= 'MAY'

IDAY= DAY-120

END IF

IF (DAY .GT. 151 .AND. DAY .LE. l8l) THEN

MONTH= 'JUNE'

IDAY= DAY-151

END IF

IF (DAY .GT. 181 .AND. DAY .LE. 212) THEN

MONTH= 'JULY'

IDAY= DAY-181

END IF

IF (DAY .GT. 212 .AND. DAY .LE. 2^3) THEN

MONTH= 'AUGUST'

IDAY= DAY-212

END IF

IF (DAY .GT. 243 .AND. DAY .LE. 273) THEN

MONTH= 'SEPTEMBER'

IDAY= DAY-2J43

END IF

IF (DAY .GT. 273 -AND. DAY .LE. 30^) THEN

MONTH= 'OCTOBER'

IDAY= DAY-273

END IF

IF (DAY .GT. 304 .AND. DAY .LE. 33^) THEN

MONTH= 'NOVEMBER'

IDAY= DAY-304

END IF

IF (DAY .GT. 334) THEN

MONTH= 'DECEMBER'

IDAY= DAY-334

END IF

B 6
PROGRAM ANALYZE. FTN

C LEAP YEAR

ELSE

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY = END IF

IF (DAY

MONTH=

IDAY=

END IF

END IF

RETURN

END

.GT. 31 .AND. DAY . •FEBRUARY'

DAY-31

.GT. 60 .AND. DAY , 'MARCH'

DAY-60

.GT. 91 .AND. DAY , 'APRIL'

DAY-91

.GT. 121 .AND. DAY

'MAY'

DAY-121

.GT. 152 .AND. DAY

' JUNE

DAY-152

.GT. 182 .AND. DAY

'JULY'

DAY-182

.GT. 213 .AND. DAY

'AUGUST'

DAY-21

.GT. 244 .AND. DAY

'SEPTEMBER'

DAY-24i|

.GT. 274 .AND. DAY

'OCTOBER'

DAY-274

.GT. 305 .AND. DAY

: 'NOVEMBER'

DAY-305

.GT. 335) THEN

'DECEMBER'

DAY-335

LE. 60) THEN

LE. 91 ) THEN

LE. 121 ) THEN

.LE. 152) THEN

LE. 182) THEN

LE. 213) THEN

.LE. 244) THEN

LE. 27 4) THEN

.LE. 305) THEN

.LE. 335) THEN

B 7
PROGRAM ANALYZE.FTN

SUBROUTINE ECALC(NO , X,AVE ,SIG,STD)

REAL X(100)

SMW= 0.

S= 0.

AMT= FLO AT (NO) - 1 DO 10 1=1 ,N0

S= S + X(I)

10 CONTINUE

AVE= S/FL0AT(N0)

SIG= SQRT(AVE)

DO 20 1=1 ,N0

SMW= SMW + (X(I) - AVE) *« 2

20 CONTINUE

STD= SQRT(SMW/AMT)

SIG= (SIG / AVE) » 100.

STD= (STD / AVE) * 100.

RETURN

END

SUBROUTINE OTSIDE ( N , NX , XBAR , X , SW , TX , KOUT , JT

)

C DETERMINE HOW MANY X'S FALL OUTSIDE NX STANDARD DERIVATIVES OF THE MEAN

REAL X(100),SW(100),TX(100)

K0UT= 0

JT= 0

DO 10 1=1 ,N

SW(I)= (X(I) - XBAR) / SQRT(XBAR)

DIFF = ABS(SW(I))

IF (DIFF .GT. NX) THEN

KOUT= KOUT + 1 ELSE

JT= JT + 1 TX(JT)= X(I)

END IF

10 CONTINUE

RETURN

END

SUBROUTINE PEXTRA(NO , X,SW)

REAL X(IOO) ,SW(100)

WRITE (4,*)

WRITE(4,1000)

1000 F0RMAT(22X, 'X' ,1 3X, 'SW'

)

DO 10 1=1 ,N0

WRITE (i| ,1001 ) X(I),SW(I)

1001 FORMATd 7X,F1 1 .2 ,5X,F6.2)

10 CONTINUE

RETURN

END

B8
APPENDIX C - Californium Source Decay Code Listing

C CFYLD—CALIFORNIUM YIELD 6/26/82.

DIMENSION KCOM(66)

CHARACTER*! REP

CHARACTER*'4 A

C THIS PROGRAM USES 2.645 YR HALFLIFE FOR 252CF AND NU=3.766.

C FOR 250CF IT USES 13.2 YRS AND 3.53. FOR 254CF IT USES 61.9 DAYS

C AND 3.93. NU RATIOS ARE FROM N. SC. AND ENGIN. 43,5^(1971).

C RATIO OF ALPHA PARTICLE TO SPONTANEOUS FISSION RATE IS FROM

C J. INORG. NUCL CHEM 27,33(1965)., IE., 31.3 AND 1260.

C LAMBDA ALPHA/(LAMBDA SP FISSION) = 1/(1260+1) AND 1/(31.3+1)

C SP FISSION/ALPHA FOR 254 IS 0.997

C

DATA CFOHF/13.2/, CF2HF/2 . 645/ , CF4HF/61.9/, CFONU/3.53/,

&CF2NU/3.766/, CF4NU/3.93/

A='XXXX'

1 F0RMAT(F14.0)

2 F0RMAT(6X,A4,I2, '

,

' , I4 , 1 P4E1 2 . 4

3 FORMAT (15)

4 FORMAT (/7X,

&'GIVE THE DAY, MONTH, AND YEAR OF ISOTOPIC ANALYSIS ')

5 F0RMAT(7X, 'IN F FORMAT THE ATOM PERCENT COMPOSITION OF CF250

& 252, AND 254 ='

6 F0RMAT(7X, 'GIVE THE DAY, MONTH, AND YEAR OF CALIBRATION ')

7 F0RMAT(/7X' DATE ' 3X ' 250/T0TAL ' 3X ' 254/TOTAL ' 3X

&'DECAY'7X'N/SEC'/)

8 FORMAT (7X' GIVE THE DAY, MONTH, AND YEAR FOR THE END OF THE ' &/7X'TABULATI0N '/)

9 F0RMAT(7X'IN F OR G FORMAT WHAT IS THE CALIBRATION

&0N THAT DATE ? '

10 FORMAT (7X' GIVE THE DAY, MONTH, AND YEAR FOR THE START OF THE ' &/7X' TABULATION IN I FORMAT'/)

11 FORMAT (/7X,

&'THE HALF LIVES USED IN YEARS FOR CF250 AND CF252,',/

&7X,' AND IN DAYS FOR CF254 = '/)

12 F0RMAT(7X'TYPE THE TITLE INFORMATION '/)

1 3 FORMAT (66A1 ) 14 F0RMAT(7X,66A1

15 F0RMAT(7X,3F1 4 .6)

16 FORMAT (/7X, 'THE VALUES USED FOR NUBAR = '/)

18 FORMAT (/7X' GIVE A CARRIAGE RETURN AFTER EACH DATA ENTRY')

19 F0RMAT(7X'THE ATOM PERCENT COMPOSITION OF CF250

& 252 AND 254 =')

20 F0RMAT(7X'WHENEVER YOU REQUIRE NO FURTHER OUTPUT, ANSWER THE NEXT'

&/7X'REQUEST FOR DAY, MONTH, AND YEAR WITH THREE CARRIAGE RETURNS.'

&' '/)

21 FORMAT (/7X' THE OUTPUT WILL BE ON FOR002.DAT.')

22 FORMAT (Al ) 23 FORMAT (7X' GIVE THE DAY, MONTH, AND YEAR '/)

24 F0RMAT(7X'D0 YOU WISH TO INPUT A SPECIFIC DATE (Y/N) ? '/)

0PEN(2,STATUS='NEW'

WRITE(7,18)

CI
CALIFORNIUM SOURCE DECAY

WRITE(7 ,4)

READ(5,3)ID,M,IYR0

CALL IDAYS(ID,M,IYRO,IDAYO)

WRITE(7,5)

READ (5,1) X050 , X052 , X054

C NORMALIZE THE NEUTRON EMMITTERS TO 1

SN=X050+X052+X054

X50=XO50/SN

X52=X052/SN

X54=X054/SN

WRITE(7,6)

READ(5,3)ID,M,IYR1

CALL IDAYS(ID,M,IYR1 ,IDAY1

)

CALL LPDAYS(IYR1,IYR0,ITL)

WRITE(7 ,9)

READ(5,1 )CA

IT=(IYR1 -IYR0)*365+(IDAY1 -IDAYO)+ITL

C * DEBUG OPTIONS FOLLOW

C WRITE(7,400)IDAY0,IYR0,IDAY1 ,IYR1 ,ITL,IT

C ^00 F0RMAT(7X, ' IDAYO ,IYRO ,IDAY1 ,IYR1 ,ITL,IT' ,/7X,8l6)

T=FLOAT(IT)

A500=0.6931 47*CF0NU*X50/(CF0HF* 365. 25*1261 .

)

A520=0.6931 i<7*CF2NU*X52/(CF2HF*365. 25*32.3)

A540=0.693l47*CF4NU*0.997*X54/CFi^HF

AAT=A520+A500+A5M0

AT0=1

F00=A500/AAT

F40=A540/AAT

A50=A500*EXP( -0. 6931 47*T/( CF0HF*365. 25 )

)

A52=A520*EXP(-0.6931 47*T/(CF2HF*365.25)

A54=A540*EXP(-0.6931 47*T/CF4HF)

ATT=A50+A52+A54

AT1=ATT/AAT

FOl =A50/ATT

F4l =A54/ATT

AT=AT1

CN0=CA/AT1

WRITE(7,12)

READ(5,13)KCOM

WRITE(2,1 J4)KC0M

WRITE (2,1 9)

WRITE (2,15) X050 , X052 , X054

WRITE(2 ,1 1

)

WRITE(2,15) CFOHF, CF2HF, CF4HF

WRITE(2 ,1 6)

WRITE (2,1 5) CFONU, CF2NU, CF4NU

WRITE(2,7)

CALL MODAY(IYR0,IDAY0,A,ID)

WRITE(2 ,2)A,ID,IYR0,F00 ,F40 ,ATO,CNO

CN1 =CN0*AT1

CALL MODAYdYRl ,IDAY1 ,A,ID)

WRITE(2,2)A,ID,IYR1 ,F01 ,F4l ,AT1 ,CN1

WRITE(7 ,20)

60 WRITE(7,24)

C2
CALIFORNIUM SOURCE DECAY

ACCEPT 22, REP

IF ( (REP.EQ. 'Y' ) .OR. (REP.EQ. 'y ' ) ) GO TO 70

WRITE(7,10)

READ(5 ,3)ID,M,IYR2

IF(ID.EQ.O)GO TO 200

CALL IDAYS(ID,M,IYR2,IDAY2)

WRITE(7,8)

READ(5 ,3)ID,M,IYR3

CALL IDAYS(ID,M,IYR3 ,IDAY3)

CALL LPDAYS(IYR3,IYR2,ITL)

N=(IYR3-IYR2)*365+IDAY3-IDAY2+ITL+1

GO TO 80

70 N=1

WRITE(7 ,23)

READ(5,3)ID,M,IYR2

IF(ID.EQ.0)GO TO 200

CALL IDAYS(ID,M,IYR2 ,IDAY2)

80 CALL LPDAYS(IYR2,IYR0,ITL)

IT2=(IYR2-IYR0)^f365 + IDAY2-IDAY0 + ITL

C * DEBUG OPTIONS FOLLOW

C WRITE(7,500)IDAY0,IYR0,IDAY1 ,IYR1 , IDAY2 , IYR2 , ITL , IT2

C 500 F0RMAT(7X, ' IDAYO , lYRO , IDAY1 , IYR1 , IDAY2 , IYR2 , ITL , IT2 ' ,/7X,8l6)

T=FL0AT(IT2)

DO 100 1 = 1 ,N

A50=A500*EXP( -0. 6931 47*T/( CF0HF*365 . 25 )

)

A52=A520*EXP(-0.6931 47*T/( CF2HF^^365 . 25 )

)

A54=A540*EXP(-0.6931 47*T/CF4HF)

ATT=A50+A52+A54

AT1=ATT/AAT

F01=A50/ATT

Fill =A54/ATT

CN1 =CN0*AT1

CALL M0DAY(IYR2,IDAY2,A,ID)

IF ( (REP.EQ. 'Y' ) .OR. (REP.EQ. 'y' ) ) THEN

WRITE(7 ,2)A,ID,IYR2,F01 ,F^^ ,AT1 ,CN1

END IF

WRITE(2,2)A,ID,IYR2,F01 ,FMl ,AT1 ,CN1

IDAY2=IDAY2+1

IF (IDAY2.lt. 366) GO TO 100

IF(IDAY2.GT.366)GO TO 95

IMOD=MOD(IYR2,4)

IF(IMOD.NE.0)GO TO 95

GO TO 100

95 IDAY2=1

IYR2=IYR2+1

100 T=T+1

GO TO 60

200 CL0SE(2)

WRITE(7 ,21 ) STOP

END

C3
CALIFORNIUM SOURCE DECAY

SUBROUTINE IDAYS (I D, M , lYR ,IDAY)

C THIS SUBROUTINE CALCULATES THE JULIAN CALENDAR DAY OF THE YEAR

C

1 FORMAT (7X' YOU TYPED MONTH AND DAY. TYPE DAY AND MONTH V)

3 FORMAT (15)

IF(IYR.LT.1900)IYR=IYR+1900

IF(M.GT.12)WRITE(7,1

)

IF(M.GT.12)READ(5,3)ID,M

IY=M0D(IYR,4)

C FOR MONTHS AFTER FEBRUARY

X=2.0

C FOR JANUARY AND FEBRUARY

IF(M.LE.2)X=0.0

C FOR MONTHS AFTER FEBRUARY IN LEAP YEARS

IF(M.GT.2.AND.IY.EQ.0)X=1 .0

Y=(M-1 )*30.57+0.5+ID-X

IDAY=INT(Y)

RETURN

END

C

SUBROUTINE LPDAYS( I2YR , I 1 YR , ITL

)

C

C THIS SUBROUTINE CALCULATES THE LEAP YEAR DAYS BETWEEN II YR

C AND THE YEAR PRECEDING I2YR.

C

ITL=0

IF(I1 YR.GE.I2YR)G0 TO 60

DO 50 1=11 YR,I2YR-1

IMOD=MOD(I ,4)

C * DEBUG OPTIONS FOLLOW

C 3 FORMAT (7X, 'ITL, I, AND IMOD ARE ',3I8)

C WRITE (7, 3) ITL, I , IMOD

50 IF(IM0D.EQ.0)ITL=ITL+1

60 RETURN

END

C

SUBROUTINE MODAY( lYR , IDY , A , ID)

C

C MODAY—THIS SUBROUTINE CALCULATES THE MONTH AND DAY OF THE YEAR

C FROM THE JULIAN CALENDAR DAY. 9/11/81

C

CHARACTER * 4 AO , AJAN , AFEB , AMAR , AAPR , AMAY , AJUN , AJUL , AAUG , ASEP , AOCT

1 ANOV,ADEC,A

DATA AO/'****'/,AJAN/'JAN V.AFEB/'FEB V.AMAR/'MAR '/,

&AAPR/'APR V, AMAY/ 'MAY '/,AJUN/'JUN '/,AJUL/'JUL '/, AAUG/ 'AUG '/,

&ASEP/'SEP '/,AOCT/'OCT '/,ANOV/'NOV '/,ADEC/'DEC '/

C

IF(IDY.EQ.O) GO TO 1000

A=AO

J=1

C4
CALIFORNIUM SOURCE DECAY

C IDY MUST NOT BE CHANGED BECAUSE IT IS RETURNED TO MAIN PGM

C

IDAY=IDY

IMOD=MOD(IYR,^)

IF(IDAY-31 )10,10,20

10 A=AJAN

ID=IDAY

GO TO 1000

20 IF(IDAY-59)30, 30,^0

30 A=AFEB

ID=IDAY-31

GO TO 1000

i|0 IF(IDAY.EQ.60.AND.IMOD.EQ.0)J=0

IF(J-1 )50,60,60

50 A=AFEB

ID=IDAY-31

GO TO 1000

60 IF(IM0D.EQ.0)IDAY=IDAY-1

C IDAY AT THIS LINE OF THE PROGRAM MUST BE 60 OR GREATER.

C THIS SECTION OF THE PROGRAM DECIDES WHERE THE PROGRAM

C SHOULD CONTINE IN ORDER TO AVOID MOST OF THE FOLLOWING 'IF'

C STATEMENTS.

C

K=(IDAY-6)/30

GO TO (65,65,80,100,120,140,160,180,200,220,240,240) K

C

C ***************************** ******

65 IF(IDAY-90)70,70,80

70 A=AMAR

ID=IDAY-59

GO TO 1000

80 IF(IDAY-120)90,90,100

90 A=AAPR

ID=IDAY-90

GO TO 1000

100 IF(IDAY-151 )1 10,1 10,120

110 A=AMAY

ID=IDAY-120

GO TO 1000

120 IF(IDAY-181 )130,130,140

130 A=AJUN

ID=IDAY-151

GO TO 1000

140 IF(IDAY-212)150,150,160

150 A=AJUL

ID=IDAY-181

GO TO 1000

160 IF(IDAY-243)170,170,180

170 A=AAUG

ID=IDAY-21

GO TO 1000

180 IF(IDAY-273)190, 190,200

C5
CALIFORNIUM SOURCE DECAY

190 A=ASEP

ID=IDAY-2^3

GO TO 1000

200 IF(IDAY-304)210,210,220

210 A=A0CT

ID=IDAY-273

GO TO 1000

220 IF(IDAY-33^)230,230,240

230 A=AN0V

ID=IDAY-304

GO TO 1000

240 A=ADEC

ID=IDAY-334

GO TO 1000

1000 RETURN

END

C6
EXAMPLE OUTPUT

NBS 118 (TYPE III) SOURCE STRENGTH PER 14 FEB 1985 CALIBRATION

THE ATOM PERCENT COMPOSITION OF CF250, 252 AND 254 = 8.160000 86.260002 0.021000

THE HALF LIVES USED IN YEARS FOR CF250 AND CF252,

AND IN DAYS FOR CF254 = 13.200000 2.645000 61.900002

THE VALUES USED FOR NUBAR =

3.530000 3.766000 3.930000

DATE 250 /TOTAL 254 /TOTAL DECAY N/SEC

DFC 13 1983 4 0341E- W wJ _L J—04 1X « 1

•3-1 op_ m 1 OOOOE-fOO 7

XFFRIII* 14 1985 5 a094F- 04 1X « A91 9F- 03 R9RRp_ m\J X

R^ < TTir 91 1 QRt; Z L f XjOD D . Ut Z 7 A AQP'— nui-A R R9AQT^— OZbyCj n n U X

A

ft

A CI RTTj- A Q . 4b / tsUi+u

y

d ULj b . Jb / b£j— U1 7Z . 7 1 c 7ir' A A U4 bOZZ Q 9 7 7ir_ /Ci A T U X

A

4: ,. 4b4brj-rU

y

1 1 1

iJ ULi b . J / X Jt— Uft- z

C Q D HIT . booUCj— A A U4 b

OXoDEj Q 1 Q RTr_ A 1 U X

A

ft

A Ci A Tr_L A Q . 4bX4lL-rUy

TTTT J ULi O /I 1 Q Q R b

3 7 R (VC AU4/I 7z

. bbUUh.— A A U4 bCJXft Q 1 y1 jJH.— 7T A 1 U X

A4 , /IRQ 0 ir^_i_ A Q . 4bDZh.-rUy

TTTT J ULi ZD ;• ± y oD b . J / obJl. Uft 7Z I. cbJZ7 7 7Jr.— c A A Uft b

0RimX U XJ-jV— nU X1 Aft , /I R R ATTJ. A Q . 4bDUE4-rUy

TTTr ZD X y oo b

"3 RO "3^— Uft 0z

c A/1 RTT — , bUftOHi AUftA c0

RHRQP- 0 U ZJ !7Ili n 1 4 ART RTT-i- A Q . 4DXoCjT^Uy

TTTT J ULi z /

^ xy b

nUftA 7z R 7 7 717" _ Ail Uft b

R0 mU X DHj RP- nU 1

J. A4 .44A A RtT-i- oblLTUA Qy

TTTr J ULi ZD ^ xy OD b . joy /ili HAUft 7Z R R n RC_ A A Uft u . 1 J 1 DI-i \J X

/I 4 A A R ATT'j.n Q . 44D4ll.TUy

UTTTT ULi 9Qz y X

T QDR y 0 D b

3 0 7 QTT- J y J jCj DAUft 7z . DZI- R9 A9P- ZHi OAUft R 70-3 4.p_m\J X Aft A A99T7'-l-nQ

TTTr U ULi J u ^ X y 0 D b7 Q 7 fiPT"— HAU** 7Z . AQ7QT— ft y / yt"^ A A Uft R 7PQ7p_ X

/Ift A'^QnTT'j.nQ . ft j5yui_.TUi7

JTTTT ULi jxD 1 1 Q Q R ^ X y OD b

Ann 4 U U 7T^- / 111 Uft 7Z . ft / X yt. A/l U4- / 0 J XXj X 4 . A7RRT7'-4-nQ ft jDoi-jTuy

a TIP 1X ^ X

1 QRR y 0 D b > rtU't't-l-f HAU^i 7Z A AC n P"- . fttb xjCj • nUftA R 7Q/ 0 nqp- U -7 111 niX A

aTTr* AULt 0 1 Q Q R z r xytSD b/I n D T T U4 7

4-

/I 7 ACTT . 4 ZUbr.- C\A Uft b

77c: pTr_ nU nX 4 A 9 Q ATT-l-A Q . 4 Z y 4lliT^U y

a TTr* "3 1 Q Q R J , xy DO b . 4-XXtJt- U4 7z7 Q R 1? A A b

1 1 L^XHiLt nU X1 A4

/I 7 A 717" J. A Q . 4ZbZxi.TUy

A 1 Q R 4 , xy DO b ./I T R RTT n A U4 7z7 7 A /I IT A ^ U4- b

7C^R RTT- nU 1X 4

/I 7 7 ATT'j.A Q . 4Z jUH-rUy

AU(_j R 1 0 0 R rb

419 Zt- 04 z . 34b /h.- 04 b/b4 Jt- A T UX /I4

/I 1 Q DTTx. A Q

TV TT^ AU(j b , ly ob b . 4ZZyn- 04 z . 3ZlZE- 04 5

7 An 7F- U X 4 . 4 Xb /E-rUy

Jn.\J\j 7 1 QRR D . Tt Z ODHj n A 7z 9071 Tr_ . z y / xij • nu At R 7560E- 01 A AT 7RP4.AQ

AUG 8,1985 6. 4303E-04 2 . 2731E-04 5. 7519E-•01 4 .4103E-1-09

AUG 9,1985 6. 4340E-04 2 . 2494E-04 5. IMIYL-01 4 .4071E-f-09

AUG 10,1985 6. 4377E--04 2 . 2260E-04 5. 7436E-01 4 .4040E-I-09

AUG 11,1985 6. 4414E-04 2 . 2028E-04 5. 7395E-01 4 .4008E-(-09

AUG 12,1985 6. 4451E--04 2 . 1798E-04 5. 7354E-01 4 . 3976E-H09

AUG 13,1985 6. 4488E--04 2 . 1571E--04 5. 7312E-01 4 . 3945E-H09

AUG 14,1985 6. 4525E--04 2 . 1346E-04 5. 7271E-01 4 . 3913E-I-09

AUG 15,1985 6..4562E--04 2 . 1123E--04 5. 7230E-01 4 . 3882E-H09

AUG 16,1985 6..4599E--04 2 . 0903E--04 5. 7189E-01 4 . 3850E^+-09

AUG 17,1985 6.,4637E--04 2 . 0685E--04 5. 7148E-01 4 . 3818E-H09

AUG 18,1985 6.,4674E--04 2 .0470E--04 5. 7107E-01 4 . 3787E-f09

AUG 19,1985 6.,4711E--04 2 .0256E--04 5. 7065E-01 4 .3755E-I-09

AUG 20,1985 6.,4748E--04 2 . 0045E--04 5. 7024E-01 4 .3724E-I-09

AUG 21,1985 6..4786E--04 1 .9836E--04 5. 6983E-01 4 . 3693E-f09

AUG 22,1985 6..4823E--04 1 .9630E--04 5. 6942E--01 4 .3661E-f-09

AUG 23,1985 6..4860E--04 1 . 9425E--04 5. 6902E--01 4 .3630E-I-09

AUG 24,1985 6,.4897E--04 1 .9222E--04 5. 6861E--01 4 . 3598E-t-09

AUG 25,1985 6.. 4935E--04 1 .9022E--04 5..6820E--01 4 .3567E-f-09

C7

Appendix D

1 . INTERFACE OF COUNTING ELECTRONICS TO MICROCOMPUTER

The counter electronics are connected to a microcomputer for data

storage and analyses. The principal interface component is the

Tennelec "TC-588" Buffered Printout Control Interface. This

module collects data from various NIM modules such as scalars,

timers, etc. by a Daisy Chain interconnection cabling system. The

data is first swept into a buffer in the TC-588 and then made

available to a PRO-350 microcomputer by an RS-232 line.

1 . 1 Line Characteristics

The LINE CHARACTERISTICS presently set in the PRO-350 are given in

Table D-1 .

TABLE D-1

Line Characteristics of the PRO-350 which must be compatible with the

output from the TC-588

Receive Baud Rate 1200

Transmit Baud Rate 1200

Number of Data Bits 8

Number of Stop Bits 1 Parity OFF

XON/XOFF control Enabled

7-bit character codes Enabled

Connection Type Handwired

1 .2 Communications Line Compatability

To make the TC-588 output compatible with the above conditions, two

DIP switches, SW1 and SW2 , inside of the TC-588 must be set as shown in Table D-2.

Dl
TABLE D-2

Switch Settings In The TC-588

Switch

Name

SWl

SW1

SWl

SWl

SWl

SWl

SWl

Function

TTY or RS-232

(Not used)

Pari ty

Stop Bits

Number of Bits

Tl TT TT (doesn't matter)

Switch

Number

12

3

4

5

6

7

On or Off

"ON" = RS232

"OFF" = No parity

"ON" = one stop bit

"OFF" (means 8

"OFF" bits)

SW2 Band Rate 1,2,3,4 "ON,OFF,OFF,OFF"=9600 band

1 . 3 Switch Settings on Print Out Control

The only other requirement for the TC-588 is to assure that operation

is carried out with the two switches on the front face of the unit set

as follows: the READOUT MODE Switch should be in the "AUTO RECYCLE"

position; the OUTPUT FORMAT switch should be in the "NORMAL" position.

1 .4 Malfunction of the Readout System

The two red push buttons normally do not require activation in the

autocycle mode. However, occasionally the Daisy Chain system hangs up

and this is identified by one of two conditions as seen on the readout

lights of the TC-588 and the Time-of-Day/Year Clock. These conditions

are either: (1) no visible lights; (2) or lights on the TC-588 rapidly

flash as if unit is performing readout operation. These hangup

conditions are usually eliminated by pushing the RESET button, the

PRINT button and then the RESET button a second time.

D2
2. DATA COLLECTION

The following is the procedure for collecting data from the MNSO^

activity counting electronics, using a Digital Equipment Corporation

(DEC) Pro-350 computer.

2.1 To Start Data Taking

2.1.1 On the PRO-350:

1 ) Select "PRO TOOL KIT" from the Main Menu

2) Run DTE

3) Push "ADDITIONAL OPTIONS" key

4) Select "START HOST OUTPUT LOGGING"

5) Specify the output log name (XXXXXX.LOG)

6) Push "RESUME" key

2.1.2 Start Data Taking on the TC-535P Timer/Sealer:

1 ) Push "RESERT" button

2) Push in "START/STOP" button

2.2 To Stop Data Taking

2.2.1 ON THE TC-353P:

1 ) Release "START/STOP" button

2.2.2 On the PRO-350:

1 ) Push "ADDITIONAL OPTIONS" key

2) Select "STOP HOST OUTPUT LOGGING"

3) Push "RESUME" key

4) Push "EXIT" key (only once)

At this point, there are a variety of things which can be done. For

example, the file can be viewed on the CRT of the PRO-350, it can be

printed out, it can be saved to a floppy diskette (remember, it is

already on the hard disk), it could be edited, but most importantly,

can be analyzed to get final results. Since the latter is the normal

mode of operation, we will conclude this sequence with the analysis

procedure and that to obtain a printout of the analyzed results. the

other options are covered in Appendix A.

2.2.3 On the PRO-350 (in PRO Tool Kit)

1 ) Type RUN ANALYZE

Answer the questions and provide the requested input. See discussion

on the "ANALYZE" Program for details about the input required for the

various program options (background counts, calibration counts of

NBS-I , counts of source to be calibrated, etc.).

D3
2) Type "COPY" (to get the printout of the output file)

FROM: Filename. ext

TO: LP:

3 . 110 VOLT SUPPLY AND THE UNINTERRUPTABLE POWER SUPPLY

Part of the system is on an uninterruptable power supply which will

keep the system (main electronics and microcomputer) alive sufficiently

long to log the last result and close the data files. See Fig. D-1

FIGURE D.I

1 10 AC

From Bldg. 245

, ! Emergency

Light

Bottom Power

Strip

(not UPS)

Oscilloscope

Uninterruptable

Power

Supply (UPS)

Top Power Strip

with

Surge Protection

Digital

PRO

350

y Computer

TOP NIM BIN

(MnSOj

Electronics)

BTM NIM BIN

(MnSO^

Electronics)

Extra NIM BIN

ADCAM

Electronics

ND-62

Multichannel

Analyzer

Printer

for

PRO-350

Electrical Connections to Unfiltered Building Power and Filtered Power

from an Uninterruptable Power Supply (UPS).

D4
NBS-114A (REV. 2-8C) U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

REPORT NO.

SHEET (See instructions) NBS/SP-250/18 March 1988

4. TITLE AND SUBTITLE

NBS MEASUREMENT SERVICES: NEUTRON SOURCE STRENGTH CALIBRATIONS

5. AUTHOR(S)

E. Dale McGarry and Edward W. Boswell

6. PERFORMING ORGANIZATION (If joint or other thon NBS. see /n struct ions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

Gaithersburg, MD 20899

7. Contract/Grant No.

8. Type of Report & Period Covered

Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Same as item above.

10. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 88-600510

I I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most si gnifi cant information. If document includes a significant

bibliography or literature survey, mention it here) The manganese sulfate (MnS04) bath method of neutron source strength calibration at

NBS is described and compared briefly with other MnS04 bath techniques used

internationally. The accuracy of source intercomparisons and practical limitations

of the NBS system. In particular, there is discussion of uncertainties associated

with system limitations and with corrections necessary for neutron capture in the

source, capture of fast and thermal neutrons by competing reactions in the MnS04,

capture of neutrons in the source container, and the correction for leakage of

neutrons from the bath, which is 1.27 meters in diameter.

12. KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

calibrations; emission rate; manganese sulfate; neutron source; source strength

determination

13. AVAILABILITY

Unlimited

I I For Official Distribution, Do Not Release to NTIS

Kxj Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

[331 Order From National Technical Information Service (NTIS), Springfield, VA, 22161

14. NO. OF

PRINTED PAGES

58

15. Price

*U.S. Government Printing Office : 1988 - 201-597/82550 USCOMM-DC 6043-P80



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