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JAEA Reports

Radiation shielding analysis of the upper structure of an accelerator-driven system

Iwamoto, Hiroki; Meigo, Shinichiro; Nakano, Keita; Yee-Rendon, B.; Katano, Ryota; Sugawara, Takanori; Nishihara, Kenji; Sasa, Toshinobu; Maekawa, Fujio

JAEA-Research 2021-012, 58 Pages, 2022/01

JAEA-Research-2021-012.pdf:7.23MB

A radiation shielding analysis was performed for the structure located above the spallation target of an accelerator-driven system (ADS), assuming one cycle of an 800 MW thermal and 30 MW beam power operation. In this analysis, the Monte Carlo particle transport code PHITS and the activation analysis code DCHAIN-PHITS were used. The structures to be analyzed are a beam duct above the target, a beam transport room located above the ADS reactor vessel, beam transport equipment, and the room ceiling. For each structure, the radiation doses and radioactivities during and after the operation were estimated. Furthermore, the shielding structure of the ceiling was determined. As a result, it was found that the radiation dose at the site boundary would be sufficiently lower than the legal limit by applying the determined shielding structure. Moreover, under the condition of this study, it was shown that the effective dose rate around the beam transport equipment positioned above the target after the operation exceeded 10 mSv/h, and that the maintenance and replacement of the equipment in the room would require remote handling.

JAEA Reports

Measurement of fission cross section and fission neutron spectrum of Np-237 by an advanced technique

JNC TJ9400 2000-007, 46 Pages, 2000/03

JNC-TJ9400-2000-007.pdf:2.16MB

For fission cross section and prompt fission neutron spectrum, which largely influence core characteristics of a fast reactor, we have performed experimental and analytical studies for developing an advanced technique to measure absolute fission cross section and neutron fission spectrum for actinide nuclides such as Np237. As the results, we could develop an advanced technique, which combines a normalization technique for the well-known differential cross section and a correction method by a Monte-Carlo code for sample effects. This advanced technique accurately provides both absolute fission cross section and prompt fission neutron spectrum individually. By employing this technique, in this study, we have measured for three actinides ( $^{237}$ Np, $^{232}$ Th and $^{233}$ U), then, have obtained the fission cross sections and fission spectrum parameter data for those nuclides. Furthermore, we have also performed an analytical study to examine sensitivity of fission spectrum parameter to core multiplication factor by using the standard calculation code for a first reactor.

JAEA Reports

Improvement of covariance data for fast reactors

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JNC TJ9400 2000-004, 109 Pages, 2000/02

JNC-TJ9400-2000-004.pdf:4.96MB

We estimated covariances of the JENDL-3.2 data on the nuclides and reactions needed to analyze fast-reactor cores for the past three years, and produced covariance files. The present work was undertaken to re-examine the covariance files and to make some improvements. The covariances improved are the ones for the inelastic scattering cross section of $^{16}$ O, the total cross section of $^{23}$ Na, the fission cross section of $^{235}$ U, the capture cross section of $^{238}$ U, and the resolved resonance parameters for $^{238}$ U. Moreover, the covariances of $^{233}$ U data were newly estimated by the present work. The covariances obtained were compiled in the ENDF-6 format.