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Abstract

It has long been known that, for light water reactors, the temperature coefficient of reactivity calculated from microscopic nuclear data differs in a systematic way from that obtained in critical experiments as well as in the start-up operations of large power reactors. In order to remove this discrepancy, it has been proposed that the energy dependence of certain nuclear data be modified with respect to ENDF/B-V. In particular, the "238"** capture cross section sigma(238) in the subthermal and thermal range should decrease with energy faster than 1/v, due to the presence of a negative energy resonance. In order to check this hypothesis sigma(238) was measured at the Geel linac for both a metallic and an oxide sample using four C-6-6 detectors operated in coincidence. In order to increase the number of cold neutrons, a liquid methane moderator kept at -170circC temperature was installed around the neutron producing target. Relative values of sigma(238) together with their estimated uncertainties are given down to 0.002 eV energy and compared with the proposed shape as well as with the JEF- 1 evaluation.

Additional information

Authors: CORVI F, JRC GEEL ESTAB. (ITALY);FIONI G JRC GEEL ESTAB. (ITALY), JRC GEEL ESTAB. (ITALY)
Bibliographic Reference: INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY, MITO (JAPAN), MAY, 30-JUNE 3, 1988, AVAILABILITY: CEC-LUXEMBOURG, DG-XIII-C-3, POB 1907, MENTIONING PAPER EN 34011 ORA
Availability: Can be ordered online
Record Number: 1989126116500 / Last updated on: 1989-06-01
Category: PUBLICATION
Available languages: en