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Central Bureau for Nuclear Measurements

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Reprinted from

Reactor Science and Technology

(Journal of Nuclear Energy Parts A/B)

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This document was prepared under the sponsorship of the Commission of the European

Atomic Energy Community (EURATOM).

Neither the EURATOM Commission, its contractors nor any person acting on their behalf

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­ Make any warranty or representation, express or implied, with respect t o t h e accuracy,

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1° — Assume any liability with respect t o t h e use of, or for damages resulting from the use of

any information, apparatus, method or process disclosed in this docnmpnt

any information, apparatus, method or process disclosed in this document.

The authors' names are listed in alphabetical order.

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Vol.

17­1963,

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E U R 4 5 4 . e

R E P R I N T

THERMAL NEUTRON ABSORPTION CROSS SECTION OF BORON by P. DE BIEVRE, G.H. DEBUS and J. SPAEPEN.

European Atomic Energy Community - EURATOM. Central Bureau for Nuclear Measurements.

Geel Establishment (Belgium).

Reprinted from „Reactor Science and Technology,,.

(Journal of Nuclear Energy Parts A/B) - Vol. 17, 1963 - page 349. Summary not available.

E U R 4 5 4 . e

R E P R I N T

THERMAL NEUTRON ABSORPTION CROSS SECTION OF BORON by P. DE BIEVRE, G.H. DEBUS and J. SPAEPEN.

European Atomic Energy Community - EURATOM. Central Bureau for Nuclear Measurements.

Geel Establishment (Belgium).

Reprinted from „Reactor Science and Technology,,.

(Journal of Nuclear Energy Parts A/B) - Vol. 17, 1963 - page 349. Summary not available.

E U R 4 5 4 . e

R E P R I N T

THERMAL NEUTRON ABSORPTION CROSS SECTION OF BORON by P. DE BIEVRE, G.H. DEBUS and J. SPAEPEN.

European Atomic Energy Community - EURATOM. Central Bureau for Nuclear Measurements.

Geel Establishment (Belgium).

Reprinted from „Reactor Science and Technology,,.

(4)
(5)

Reprinted from

REACTOR SCIENCE

AND TECHNOLOGY

Journal of Nuclear Energy Parts A & Β

P E R G A M O N P R E S S

(6)
(7)

Reactor Science and Technology (Journal of Nuclear Energy Paris A/B) 1963, Vol. 17. p. 349. Pergamon Press Lid. Primed in Northern Ireland.

Thermal neutron absorption cross section of boron

(Received 19 March 1963)

T H E thermal neutron absorption cross section of b o r o n has been measured in several laboratories and the discrepancies were not explained o n a basis of statistical error calculation ( G R E E N

et al., 1954; D E R U Y T T E R et al., 1962).

T H O D E et al. proved the variation of the isotopie concen­ tration of boron with different geological origin a n d t h e dis­ agreements in the cross­section values of natural b o r o n have been partly ascribed t o the boron samples used by the experi­ mentalists of the different laboratories.

D u r i n g a recent intercomparison of samples taken from stocks of boron used as a standard in nuclear institutes, we obtained, by means of mass spectrometry, a series of results which agree with previous direct intercomparisons of t h e s a m e stocks by oscillation techniques ( G R E E N et al.)

O u r results arc given in Table 1, which indicates the ratio of the atomic boron­10 content in the sample to the atomic b o r o n ­ 10 content in the Harwell boric acid standard.

T A B L E 1

A r g o n n c I A r g o n n e 11 C . B . N . M . I I C h a l k River A . E . G . I­ontenay Cold F o m c n a y (new

slock) s t o c k )

M a s s s p e c t r o m e t e r I

0­985 ­­­ 0­002 0­986 ± 0­002 0­986 ­J­ 0­003 0­9S6 t 0­003 0­984 ­i­ 0 0 0 2 0­9995 ± 0­002 0­997 ± 0­002

M a s s s p e c t r o m e t e r II

0­983 ± 0­002 0­985 ­■■ 0­002 0­9S5 ± 0­003 0­9SS ­Í­ 0 0 0 2 0­9S6 ± 0­002 0­986 ­·­ 0­003 0­9995 ± 0­002 0­99S Í­ 0 0 0 2

A v e r a g e

0­984 0­9S5. 0­9S5 0­9S7 0­9S6 0­985 0­9995 0­997r

T h e A r g o n n e I sample is boric acid, obtained from Wexler and Ringo, A . N . L . , and was taken from the original stock used by G R E E N et al. for cross­section measurements. This stock is now almost exhausted.

T h e A r g o n n e Π sample is a p r o b e from 7001b boric acid mixed by Merck U.S. for A . N . L .

T h e C . B . N . M . I sample is Ba03 from Merck, G e r m a n y a n d

was used by DERUYTTER et al. for measurements of the thermal neutron absorption cross section of boron.

The C . B . N . M . II sample is part of 200 kg boric acid prepared by Merck, G e r m a n y a n d mixed by the C . B . N . M . This stock of natural b o r o n is t o be distributed by C . B . N . M . in the countries of the E u r o p e a n C o m m u n i t y .

T h e Chalk River sample is boric acid and originates from a boron standard a t Chalk River, C a n a d a .

T h e A . E . G . sample is a p r o b e from a large lot of boric acid prepared by Merck, G e r m a n y .

T h e F o n t e n a y 'old stock' and Fontenay ' n e w stock' samples are boric acid and originate probably from Turkey. T h e old stock has been used as a standard at Fontenay­aux­Roses, F r a n c e .

The Harwell sample was boric acid.

F r o m the present investigation, it seems worthwhile to mention the following observations:

(1) T h e values obtained for the atomic boron­10 content of t h e t w o A r g o n n c samples, the two C . B . N . M . samples, the Canadian sample (Chalk River) a n d the A . E . G . sample' ( G e r m a n y ) are identical within the statistical fluctuations. T h e quoted errors are such that the measured value has a 99 per cent probability not to exceed the indicated limits.

(2) T h e British (Harwell) a n d the two French (Fontenay O l d ' and ' n e w ' ) samples are significantly different in atomic boron­

10 content from the others but are themselves also identical within the limits of statistical fluctuations.

This result is in agreement with the value of the ratio in­ dicated by G R E E N et al. of the thermal boron absorption cross section of the A r g o n n e ­ B r o o k h a v e n standards to the thermal boron absorption cross section of the Harwell one, obtained by

oscillation in GLEEP.

Central Bureau for Nuclear Measurements TJ'TVU U

r . D E BIEVRE

J. SPAEPEN

_ Euratom, Geel, Beteiu

R E F E R E N C E S

D E R U Y T T E R Α . , D E B U S G., L A U E R Κ., M O R E T Η . a n d P R O S D O C ­

IMI A . (1962) Measurements of the Thermal Neutron Absorp­ tion Cross Section of Boron bv Means of a Time­of­FIi"ht Technique. Report E U R 12.e.

G R E E N Α . , L I T T L E R D . J., L O C K E T T E. E.. SMALL V. G . . S P U R ­

WAYA. H . a n d B O W E L E. (1954) J. Nucl. Energy 1, 144.

T H O D E H. G., M A C N A M A R A J., LOSSING F . P. a n d C O L L I N S C Β

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