Measurement and Analysis of Reactivity Worth of²³⁷Np Sample in Cores of TCA and FCA

Abstract

The reactivity worth of 22.87 grams of 237 Np oxide sample was measured and analyzed in seven uranium cores in the Tank-Type Critical Assembly (TCA) and two uranium cores in the Fast Critical Assembly (FCA) at the Japan Atomic Energy Agency. The TCA cores provided a systematic variation in the neutron spectrum between the thermal and resonance energy regions. The FCA cores, XXI and XXV, provided a hard neutron spectrum of the fast reactor and a soft one of the resonance energy region, respectively. Analyses were carried out using the JENDL-3.3 nuclear data library with a Monte Carlo method for the TCA cores and a deterministic method for the FCA cores. The ratios of calculated to experimental (C/E) reactivity worth were between 0.97 and 0.91, and showed no apparent dependence on the neutron spectrum.

Measurement and Analysis of Reactivity Worth of241Am Sample in Water-Moderated Low-Enriched UO2Fuel Lattices at TCA

“…The sample reactivity worths were corrected for the influence of the difference between H 2 and H ref to fit the function Eq. (1) to the distribution of corrected sample reactivity worths at H ref , through the following repeated procedure that was proposed in the reference: 10) 1) Equation (1) was fitted to the temporary distribution of the sample reactivity worths with no correction, through which the value of Á mx could be evaluated. …”

“…In the 1.42S core, the K determined in the reference 10) was used for this technique. In the uniform cores, those given in the reference 15) were employed after making a small correction of less than 3% for the difference in reactivity between the set of delayed neutron parameters prepared for each core and the fixed set of those actually used in the reactivity meter when the K was determined.…”

“…Those of fuel rods can be found in the references. [10][11][12] The 241 Am oxide powder surrounded by the capsule, container, tubes, and fuel rods was simulated with a two-dimensional symmetrical model shown in Fig. 5 with the 0.56S core for instance.…”

“…Detailed specifications of low-enriched UO 2 fuel rods used in these cores can be found in the references. 11,12) The arrays of fuel rods in these cores are the same as those described in the reference, 10) and hence, brief descriptions are given for the core configuration in the present paper.…”

“…Experiment 1. 241 Am Sample The 241 Am sample used in the present experiment is 22.82 grams of the 241 Am oxide powder that is packed in double cylindrical capsules of stainless steel, which is similar to those for a 237 Np sample. 10) A part of the inside of an inner capsule is filled with the 241 Am oxide powder. The length of this part is 7.39 cm.…”