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JAEA Reports

Distribution of actinide elements among various environmental factors (II)

Kudo, Akira*; Fujikawa, Yoko*

JNC TJ8400 2000-010, 67 Pages, 2000/02

JNC-TJ8400-2000-010.pdf:2.17MB

The first and second environmental releases of man-made $^{239+240}$ Pu came from nuclear explosions at Alamagordo and Nagasaki in 1945. The release at Nagasaki was more serious than at Alamagordo, because it happened in an area with a high population density. Unfissioned $^{239+240}$ Pu and various fission products have been interacting here with various environmental materials (soils, sediments, and plants) under wet and temperature conditions for more than 45 years. To assess the environmental mobility of $^{239+240}$ Pu, the distributions of radionuclides from this release were investigated at Nishiyama where heavy black rain containing unfissioned plutonium and fission products fell 30 minutes after the nuclear explosion. The vertical distributions of $^{137}$ Cs and $^{239+240}$ Pu were determined in unsaturated soil cores up to 450cm deep. Most radionuclides were found in the soil column 30cm from the ground surface. However, $^{239+240}$ Pu were detected in the groundwater as well below a depth of 200cm. No $^{137}$ Cs was found below 40cm from the ground surface or in groundwater. These observations reveal that about 3% of the total $^{239+240}$ Pu have been migrating in the soil at a faster rate than the remaining $^{239+240}$ Pu. Sharp peak of $^{137}$ Cs and $^{239+240}$ Pu, indicating heavy deposition from the Nagasaki local fallout of 1945, were found in sediment cores collected from the Nishiyama reservoir. $^{239+240}$ Pu peaks were unexpectedly discovered in pre-1945 sediment core sections. NO $^{137}$ Cs was found. By contrast to the distribution in sediment cores, $^{137}$ Cs in tree rings had spread by diffusion from the bark to the center of the tree without holding a fallout deposition record. Most of the $^{239+240}$ Pu was distributed in the tree rings following a similar deposition record to that found in sediment cores. Furthermore, a very small amount of $^{239+240}$ Pu (about 1%) was found unexpectedly in pre-1945 tree rings. The only reasonable ...

Journal Articles

Experiments and analyses on sodium void reactivity worth in mock-up cores of metallic fueled and MOX fueled fast reactors at FCA

Oigawa, Hiroyuki; Iijima, Susumu; Ando, Masaki

Journal of Nuclear Science and Technology, 35(4), p.264 - 277, 1998/04

https://doi.org/10.3327/jnst.35.264

Times Cited Count：6 Percentile：49.22(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

None

*; *

PNC TJ9500 98-001, 102 Pages, 1998/03

PNC-TJ9500-98-001.pdf:5.87MB

None

JAEA Reports

Fast Reactor Calculational Route for Pu Burning Core Design

Hunter

PNC TN9460 98-001, 156 Pages, 1998/01

PNC-TN9460-98-001.pdf:5.71MB

This document provides a description of a calculational route, used in the Reactor Physics Research Section for sensitivity studies and initial design optimization calculations for fast reactor cores. The main purpose in producing this document was to provide a description of and user guides to the calculational methods, in English, as an aid to any future user of the calculational route who is (like the author) handicapped by a lack of literacy in Japanese. The document also provides for all users a compilation of information on the various parts of the calculational route, all in a single reference. In using the calculational route (to model Pu burning reactors) the author identified a number of areas where an improvement in the modelling of the standard calculational route was warranted - the document includes a description of these changes. The calculational route makes use of several different computer programs. SLAROM calculates nuclear data from compositions, using either homogeneous or heterogeneous models. CITATION and MOSES do reactor burn-up and/or flux diffusion calculations; CITATION is used for 2D (RZ) calculations, whilst MOSES models 3D (hex-Z) geometry. PENCIL and CITDENS are essentially specialized versions of CITATION (PENCIL includes data preparation and other functions). MASSN calculates fuel cycle mass balances. PERKY performs perturbation and associated calculations, both 1'st order and exact perturbations. JOINT and RZOUT3 provide various dataset interface functions, including energy group condensation. Briefer descriptions of the calculational route are given, followed by a more detailed step-by-step approach to the calculations. This latter includes examples of all JCL and data files, and a description of all the data that a user may have to employ. The document does not give a complete description of the component programs: where options and/or data are not used in any of the calculations they have generally been ignored; ...

JAEA Reports

Transition of plutonium isotopic composition by multi-recycling

Kofuji, Hirohide;

PNC TN9410 97-100, 49 Pages, 1997/10

PNC-TN9410-97-100.pdf:1.48MB

The degradation of Plutonium isotopic composition is suggested by the multi-recycling in the LWR. On the other hand, it is expected that FBR or FR has some advantages from the view point of the use of the degraded Plutonium. In this report, the Plutonium mass flow was calculated on some scenarios focused on the trend of the Plutonium isotopic composition through several times recycling. As the results, the Plutonium composition was remarkably degraded in the case of LWR only recycling, however it would be recovered by using both the FBR core and the blanket fuels. In the case of FR recycling, Plutonium can be consumed steadily by using one ratio of LWR, LWR(Pu) and FR. Though the FBR system has some merits, for example saving the natural Uranium resource, it became clear that the FBR can be used for the purpose of using degraded Plutonium.

JAEA Reports