Impact of reactor neutron spectrum on measured spectrum averaged cross sections

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F26722445%3A_____%2F22%3AN0000040" target="_blank" >RIV/26722445:_____/22:N0000040 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/68407700:21340/22:00365041

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S0306454922004509" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0306454922004509</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.anucene.2022.109418" target="_blank" >10.1016/j.anucene.2022.109418</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Impact of reactor neutron spectrum on measured spectrum averaged cross sections

Popis výsledku v původním jazyce

The cross section averaged over 235U thermal-neutron induced fission spectrum is a fundamental quantity that can be used in evaluation and validation of nuclear data. Many experiments focused on the determination of Spectrum Averaged Cross Sections (SACS) in 235U(nth,f) Prompt Fission Neutron Spectrum (PFNS) in light water reactors using enriched uranium fuel. In these reactors, there is already some amount of water moderator be-tween the uranium fuel and the irradiated sample. Due to the decrease of hydrogen cross-section with neutron energy, the high energy tail of the reactor spectrum in cores with water moderator may be harder than the pure PFNS. This paper aims to compare the shape of the actual reactor spectrum in various core positions of a research light-water reactor differing each from other by the effective water thickness. The spectrum shape is determined both by calculations and experimentally using various high energy threshold reactions. The impact of the photo-nuclear reactions (gamma,n) competing with (n,2n) in production of the same residual nucleus was shown to be less than a percent for most of studied dosimeters. An important exception was found for 197Au(n,2n)196Au dosimeter irradiated in the outcore channel where a notable photo-neutron contribution to the production of 196Au is caused by the neutron production from the high energy gamma-rays from thermal-neutron capture in 54Fe. The corresponding ENDF/B-VIII.0 data turned out to underestimate such gamma-yield by 40 % in comparison with ENDF/B-VI.8. This has improved but however not resolved the disagreement between our measurement and calculations. The remaining deficiency was attributed to the underestimation of the evaluated cross section IAEA/PD-2019 for the 197Au(gamma,n) cross section near the reaction threshold. The later was confirmed by comparison with existing measured data.

Název v anglickém jazyce

Impact of reactor neutron spectrum on measured spectrum averaged cross sections

Popis výsledku anglicky

The cross section averaged over 235U thermal-neutron induced fission spectrum is a fundamental quantity that can be used in evaluation and validation of nuclear data. Many experiments focused on the determination of Spectrum Averaged Cross Sections (SACS) in 235U(nth,f) Prompt Fission Neutron Spectrum (PFNS) in light water reactors using enriched uranium fuel. In these reactors, there is already some amount of water moderator be-tween the uranium fuel and the irradiated sample. Due to the decrease of hydrogen cross-section with neutron energy, the high energy tail of the reactor spectrum in cores with water moderator may be harder than the pure PFNS. This paper aims to compare the shape of the actual reactor spectrum in various core positions of a research light-water reactor differing each from other by the effective water thickness. The spectrum shape is determined both by calculations and experimentally using various high energy threshold reactions. The impact of the photo-nuclear reactions (gamma,n) competing with (n,2n) in production of the same residual nucleus was shown to be less than a percent for most of studied dosimeters. An important exception was found for 197Au(n,2n)196Au dosimeter irradiated in the outcore channel where a notable photo-neutron contribution to the production of 196Au is caused by the neutron production from the high energy gamma-rays from thermal-neutron capture in 54Fe. The corresponding ENDF/B-VIII.0 data turned out to underestimate such gamma-yield by 40 % in comparison with ENDF/B-VI.8. This has improved but however not resolved the disagreement between our measurement and calculations. The remaining deficiency was attributed to the underestimation of the evaluated cross section IAEA/PD-2019 for the 197Au(gamma,n) cross section near the reaction threshold. The later was confirmed by comparison with existing measured data.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

20305 - Nuclear related engineering; (nuclear physics to be 1.3);

Projekt

<a href="/cs/project/EF16_013%2F0001790" target="_blank" >EF16_013/0001790: Posílení a rozvoj výzkumu na ČVUT v Praze s využitím výzkumné infrastruktury VR-1- Školní reaktor pro výzkumnou činnost</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2022

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Annals of Nuclear Energy

ISSN

0306-4549

e-ISSN

1873-2100

Svazek periodika

179

Číslo periodika v rámci svazku

109418

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

13

Strana od-do

1-13

Kód UT WoS článku

000860754300004

EID výsledku v databázi Scopus

2-s2.0-85137155961