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Title: Effect of the fissile bead's and thermocouple wires’ sizes on the response time of a fission couple

The fission couple is proposed as a fast response miniature neutron detector in the measurement of time dependent energy depositions within the fissile material based on theoretical analysis, but the response time of a fission couple is relatively slow in practice. The time lag originated from heat transfer process was demonstrated to be the dominating factor by theoretical simulations and experimental verification in this paper. The response of a fission couple as a function of the bead size and the thermocouple wires’ sizes are simulated using ANSYS workbench. The decrease of wires’ diameter results in the decrease of response time, and the increase of bead's diameter leads to a slight increase of response time. During a pulse heating transient in the fuel of Chinese Fast Burst Reactor II with a FWHM of 181μs, the time lag originated from heat transfer process is about tens of microseconds for the peaks of the change rate of temperature, and is of the order of milliseconds to achieve 85% of the temperature rise for a typical fission couple with a Φ 1 mm fissile bead and two Φ 0.05 mm thermocouple wires. The results obtained provide foundation for the optimization of fission couples.
Authors:
; ; ; ;  [1] ;  [2]
  1. CAEP Key Laboratory of Neutron Physics, Mianyang 621900 (China)
  2. (China)
Publication Date:
OSTI Identifier:
22308863
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 85; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; CHINA; ENERGY ABSORPTION; ENERGY LOSSES; EXPERIMENTAL DATA; FBRF REACTOR; FISSILE MATERIALS; FISSION; HEAT TRANSFER; HEATING; NEUTRON DETECTORS; NUCLEAR FUELS; OPTIMIZATION; SIMULATION; THEORETICAL DATA; THERMOCOUPLES; TIME DEPENDENCE