Sensitivity Degradation Characteristics of In-core Neutron Detector for Heavy Water Reactor, Fugen NPP
Conference
·
OSTI ID:21070048
- Japan Nuclear Cycle Development Institute (Japan)
Fugen nuclear power plant is a 165 MWe, heavy water-moderated, boiling light water-cooled, pressure tube-type reactor developed by JNC, which is the world's first thermal neutron power reactor to utilize mainly Uranium and Plutonium mixed oxide (MOX) fuel. Fugen has been loaded a total of 726 MOX fuel assemblies since the initial core in 1978. Each in-core neutron detector assembly of Fugen composed of four Local Power Monitors (LPM) is located at sixteen positions in the area of heavy water moderator in the core and monitors its power distribution during operation. The thermal neutron flux of Fugen is relatively higher than that of Boiling Water Reactor (BWR), therefore LPM, which is comprised of a fission chamber, degrades more quickly than that of BWR. An Improved Long-life LPM (LLPM) pasted inner surface wall of the chamber with {sup 234}U/{sup 235}U at a ratio of 4 to 1 had been developed through the irradiation test at Japan Material Test Reactor (JMTR). The {sup 234}U is converted to {sup 235}U with absorption of neutron, and compensates the consumption of {sup 235}U. LPM has been loaded to the initial core of Fugen since 1978. JNC had evaluated its sensitivity degradation characteristics through the accumulated irradiation data and the parametric survey for {sup 234}U and {sup 235}U. Based on the experience of evaluation for sensitivity degradation, JNC has applied shuffling operation of LPM assemblies during an annual inspection outage to reduce the operating cost. This operation realizes the reduction of replacing number of LPM assemblies and volume of radioactive waste. This paper describes the sensitivity degradation characteristics of in-core neutron detector and the degradation evaluation methods established in Fugen. (authors)
- Research Organization:
- The ASME Foundation, Inc., Three Park Avenue, New York, NY 10016-5990 (United States)
- OSTI ID:
- 21070048
- Country of Publication:
- United States
- Language:
- English
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