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Journal Articles

Development of multi-group neutron activation cross-section library for decommissioning of nuclear facilities

Okumura, Keisuke; Kojima, Kensuke; Tanaka, Kenichi*

JAEA-Conf 2015-003, p.43 - 47, 2016/03

In the safety assessment concerning disposal of radioactive wastes generated in the decommissioning of nuclear facilities, it is necessary to evaluate the radionuclide inventory produced by the activation of structured materials. For this purpose, we have to pay much attention to the activation of many impurities irradiated in various neutron spectra depending on their positions and materials. Therefore, accurate activation cross-section data are necessary for many nuclides and reactions. A new multi-group neutron activation cross-section library (MAXS) was developed based on the recent nuclear data JENDL-4.0 and JEFF-3.0/A to apply it to the activation calculations for the decommissioning of nuclear facilities. The library contains cross-sections and isomeric ratios for many reactions such as (n,$$gamma$$), (n,f), (n,2n), (n,3n), (n,p), (n,$$alpha$$), (n,d), (n,t), (n,n$$alpha$$), (n,np), and so on, for 779 nuclides, in the 199-energy group structure of VITAMIN-B6.

JAEA Reports

Evaluation on activation activity of reactor in JRR-2 applied 3 dimensional model to neutron flux calculation

Kishimoto, Katsumi; Arigane, Kenji*

JAERI-Tech 2005-016, 83 Pages, 2005/03

JAERI-Tech-2005-016.pdf:10.52MB

Revaluation to activation activity of reactor evaluated at the notification of dismantling submitted in 1997 was carried out in JRR-2 where decommissioning was advanced now. In the revaluation, estimation accuracy on neutron streaming at various horizontal experimental tubes was improved by applying 3 dimensional model to neutron transport calculation that had been carried out by 2 dimensional model, and calculating with TORT. As the result, excessive overestimations on horizontal experimental tubes and biological shield that had greatly contributed to total activation activity in evaluation at the notification of dismantling was revised, sum of their activation activities in the revaluation decreased to 1/18(case after 1 year from the permanent shutdown of reactor) of evaluation at the notification of dismantling, and the structural materials that had large activation activity were changed. By the above, it was shown that introducing 3 dimensional model was effective in evaluation on activation activity of the research reactor that had a lot of various experimental tubes.

Journal Articles

Irradiation effects on precipitation in reduced-activation ferritic/martensitic steels

Tanigawa, Hiroyasu; Sakasegawa, Hideo*; Klueh, R. L.*

Materials Transactions, 46(3), p.469 - 474, 2005/03

 Times Cited Count:15 Percentile:26.78(Materials Science, Multidisciplinary)

The effects of irradiation on precipitation of reduced-activation ferritic/martensitic steels (RAFs) were investigated, and its impacts on the Charpy impact properties and tensile properties were discussed. It was previously reported that RAFs (F82H-IEA and its heat treatment variant, ORNL9Cr-2WVTa, JLF-1 and 2%Ni doped F82H) shows variety of changes on its ductile-brittle transition temperature (DBTT) and yield stress after irradiation at 573K up to 5dpa. These differences could not be interpreted as an effect of irradiation hardening caused by dislocation loop formation. The precipitation behavior of the irradiated steels was examined by weight analysis, X-ray diffraction analysis and chemical analysis on extraction residues. These analyses suggested that irradiation caused (1) the increase of the amount of precipitates (mainly M$$_{23}$$C$$_{6}$$), (2) increase of Cr and decrease of W contained in precipitates, (3) disappearance of MX (TaC) in ORNL9Cr and JLF-1.

Journal Articles

A Study on induced activity in the low-activationized concrete for J-PARC

Matsuda, Norihiro; Nakashima, Hiroshi; Kasugai, Yoshimi; Sasamoto, Nobuo*; Kinno, Masaharu*; Kitami, Takayuki; Ichimura, Takahito; Hori, Junichi*; Ochiai, Kentaro; Nishitani, Takeo

Journal of Nuclear Science and Technology, 41(Suppl.4), p.74 - 77, 2004/03

In high power proton accelerator facilities, concrete shield can be highly activated, which makes maintenance work quite difficult. So, a low-activationized concrete (limestone concrete) is to be partially adopted as a concrete shield for Japan Proton Accelerator Research Complex (J-PARC) aiming at reducing $$gamma$$-ray exposure dose during maintenance period. A new quantity, $$^{24}$$Na-equivalent, was introduced as a criterion to assure effectiveness of the low-activationized concrete. In order of its verification, powdered low-activationized concrete and ordinary one were irradiated using FNS at JAERI. The measurements were analyzed by a shielding design code system being used for J-PARC, showing that the calculations reproduce the measured induced activity within a factor of 2. Furthermore, by using the same code system, $$gamma$$-ray exposure dose was calculated for the configuration of J-PARC to find out that $$gamma$$-ray exposure dose by the low-activationized concrete was about 10 times lower than that by the ordinary concrete in a period of less than a few days after operation.

JAEA Reports

Study on residual radioactive inventory estimation in reactor decommissioning program (Contract research)

Sukegawa, Takenori; Hatakeyama, Mutsuo; Yanagihara, Satoshi

JAERI-Tech 2001-058, 81 Pages, 2001/09

JAERI-Tech-2001-058.pdf:5.98MB

In general, neutron transport and activation calculation codes are used for residual radioactive inventory estimation; however, it is essential to verify calculations by measurement results because of geometrical complexity of the reactor and so on. The comparison between measured and calculated radioactivity in the JPDR core components showed a relatively good agreement (factor of 2), and it was cleared that water content and weight ratio of steel bars to concrete materials significantly influenced the neutron flux distribution in the biological shield (factor of 2-10 error). The measured radioactivity inside of the reactor pressure vessel wall and at the inner part of the biological shield was compared in detail with the calculations to verify the methodology applied to calculations of radioisotope production. Then it was found that the radioactive inventory could be estimated accurately with combination of calculations and measurement of radioactivity in samples and dose rate distribution for planning of dismantling activities.

Journal Articles

Calculation of the activation rate of a cylindrical sample irradiated by a cylindrical fast neutron source

; ; *; *

Nuclear Instruments and Methods, 116(2), p.361 - 364, 1974/02

no abstracts in English

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