High Temperature Doppler Effect Experiment for 238U at FCA, (II). Reaction Rate Measurement up to 2,000.DEG.C. with a Foil Heated by Laser Exposure.

Abstract

For evaluation and improvement of the accuracy of calculations of the Doppler effect in a temperature range up to 2,000°C, a new experimental device was developed to measure the 238U Doppler effect at the Fast Critical Assembly of Japan Atomic Energy Research Institute. The measurement technique is based on a reaction rate measurement with a heated foil. Components of the device that are subjected to high temperatures are made of tungsten, while the remaining structural parts are made of stainless steel. The measurements were carried out in a mock-up core of an oxide-fueled fast reactor, where the Doppler reactivity worths up to 1,500°C were previously measured.In the analysis, the activation Doppler effect was determined by precise calculation of the effective capture rate in the Doppler foil. A collision probability cell code with ultra-fine group structure, PEACO-X, was used in the resonance energy range and the conventional cell code SLAROM was used in all other energy ranges. When the JENDL-3.2 data was used, the calculation agreed with experimental values within the experimental errors (–6 a%t 2,000°C).The C/E values in the high temperature range were compared between the activation Doppler effect and the Doppler reactivity worth. Both values showed good agreement within the experimental errors. When the activation Doppler effect can be considered as complementary to the Doppler reactivity measurements, the calculation accuracy of the Doppler reactivity worth at 2,000°C was confirmed. A series of the high temperature Doppler effect measurements at the FCA extend experimental temperature range and contribute to the improvement of the calculation reliability of the 238U Doppler effect at higher temperature.