Development of a radiation survey device for a multipurpose unmanned surface vehicle

Sanada, Yukihisa; Miyamoto, Kenji*; Momma, Hiroyasu*; Miyazaki, Nobuyuki*; Nakasone, Takamasa*; Tahara, Junichiro*; Baba, Shoichiro*; Furuyama, Hiroki*

Marine Technology Society Journal, 55(5), p.222 - 230, 2021/09

https://doi.org/10.4031/MTSJ.55.5.19

Large quantities of volatile radionuclides were released into the atmosphere following the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. To evaluate their effect on aquatic organisms and radiocesium behavior in the environment, the monitoring of radioactive cesium in the waterbed soil is important. We developed a dedicated radiation survey device that can both directly measure and collect some sediment samples. A comprehensive test was conducted using this device, which was installed in an unmanned surface vehicle at Fukushima offshore contaminated by radiocesium that resulted from the FDNPS accident. Consequently, the effectiveness of this device was confirmed because the measurement results of the sediment-core sample and in-situ radiation survey results show a good correlation. A successful application of this device in the time of post-nuclear facility accident is expected.

Annual report on the environmental radiation monitoring around Tokai reprocessing plant FY 2000

Maruo, Yoshihiro; ; Takeishi, Minoru; ; ; Takeyasu, Masanori;

JNC TN8440 2001-011, 146 Pages, 2001/06

JNC-TN8440-2001-011.pdf:2.98MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed since 1975, based on "Safety Regulations for the Tokai Reprocessing Plant, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitants due to the radioactivity discharged from the plant during April 2000 to March 2001. Appendices present comprehensive information, such as monitoring program, monitoring results, meteorological data and annual discharges from the plant.

None

Maruo, Yoshihiro; ; ;

JNC TN8440 2001-001, 135 Pages, 2000/12

JNC-TN8440-2001-001.pdf:4.61MB

None

None

JNC TN4420 2000-009, 11 Pages, 2000/06

JNC-TN4420-2000-009.pdf:0.84MB

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Study on migration behavior of radionuclides in engineered clay barrier (II)

*; *; *

JNC TJ8400 2000-018, 79 Pages, 2000/02

JNC-TJ8400-2000-018.pdf:2.09MB

As a basic research for geological disposal of high-level radioactive wastes, diffusion behavior of radionuclides and corrosion behavior of overpack materials in clay buffer materials (bentonite) were studied. In the study on the diffusion behavior of radionuclides, basal spacing and water content were determined for water saturated, compacted Na-montmorillonite that is major clay mineral of bentonite. The apparent diffusion coefficients of Na, Sr, Cs and Cl ions and their activation energies were also determined at different dry densities of montmorillonite. For all kinds of ions, the activation energies were found to increase as the dry density increased. These findings suggest that the diffusion mechanism of ions in compacted montmorillonite changed with increasing dry density. As a reasonable explanation for the changes in the activation energy, we proposed a multiprocess diffusion model, in which predominant diffusion process is considered to change from pore water diffusion to interlayer diffusion via surface diffusion when the dry density increases. The Na-montmorillonite is expected to alter by the ion exchange with Ca ions, which could be introduced from groundwater and/or cementitious materials in a repository. The apparent diffusion coefficients of Na and Cs ions and their activation energies were studied for Na/Ca montmorillonite mixtures in order to know the effect of this kind of alteration on the diffusion behavior of ions. It was found that the alteration of montmorillonite affected diffusion coefficients and the activation energies for both kinds of cations. These effects cannot be explained only by the pore water diffusion. The multiprocess diffusion model proposed in this study is suggested as the most reasonable explanation for the effects. The oxidation behavior of pyrite in bentonite during drying process was studied for understanding corrosion behavior of overpack materials in bentonite. There ...

Migration behavior of actinide colloids in near-field

Nagasaki, Shinya*

JNC TJ8400 2000-004, 32 Pages, 2000/02

JNC-TJ8400-2000-004.pdf:0.69MB

Equilibrium and kinetics of sorption of NpO on illite were investigated at pH = 6 by using the differential pulse anodic stripping voltammetry method and the spectroscopic method, respectively. It was found that the sorption isotherm obtained was fitted better by the Langmuir-Freundlich type equation than by the Langmuir equation. The heterogeneity coefficient was 0.89 0.05 and the half width at half maximum (HWHM) of affinity spectrum was 0.19 log unit, indicating that the surfacc of illite used has a low degree of heterogeneity. The kinetic spectra indicated that the sorption of NpO occurs only at the outer surfacc. The mean HWHM of the kinetic spectra was 0.18 log unit. This also proves that the sorption kinetics of NpO on the illite used is controlled by the same heterogeneity of the sorption sites. From the dependence of mean rate constants on temperature, a mean apparent activation enthalpy and a mean apparent activation entropy were evaluated at 373 kJ/mol and - 69 7 J/Kmol, respectively. This value of enthalpy suggests that the sorption is not controlled by diffusion through the hydrodynamic film around the illite. Equilibrium and kinetics of sorption of NpO and Np(V) carbonate complexes (mainly NpOCO) on Na-montmorillonite were also examined by using same technique.

Demonstration study on shielding safety analysis code (VI)

Sawamura, Sadashi*

JNC TJ1400 99-002, 73 Pages, 1999/03

JNC-TJ1400-99-002.pdf:2.34MB

no abstracts in English

None

Tokizawa, Takayuki

JNC TN6450 99-001, 39 Pages, 1999/01

JNC-TN6450-99-001.pdf:1.85MB

Accuracy of helium accumulation fluence monitor

Ito, Chikara; *; Aoyama, Takafumi

PNC TN9410 98-008, 32 Pages, 1998/01

PNC-TN9410-98-008.pdf:0.79MB

A He accumulation fluence monitor (HAFM) has been developed for neutron dosimetry and the direct measurement of He production in structural component materials used for fast reactors. As to accuracy of measuring helium atoms by the HAFM measurement system, previous study using He ions implanted samples shows that this system could measure He atoms within 5% error. In order to confirm the measurement accuracy of neutron fluence in the fast reactor, the HAFM samples were irradiated to a total fluence of 10 10 n/cm in the standard fast neutron spectrum field of the Fast Neutron Source Reactor "YAYOI" at university of Tokyo. Irradiated samples were measured by the HAFM measurement system and the He Atoms Measurement System (HAMS) at Kyushu university, and the measured values were compared with the calculated He productions. The principle results are summarized as follows: (1)It was confirmed that He production in B could be measured within 5 %error by the HAFM system at the reactor core center or the experimental hole through the blanket where He were produced by neutron of 10 keV 1 MeV and at Fast Column where He were produced by neutron less than 10 keV (2)It was also found that He production in Be could be measured within 5 % at the experimental hole through the blanket. Thus it is expected that Be could be applied to measurements of fast neutron of its energy over 1 MeV. (3)The differences between the measured values by the HAFM measurement system and those by HAMS were less than the experimental error, therefore it was confirmed that the measured values was reliable.

None

PNC TJ1603 97-003, 80 Pages, 1997/03

PNC-TJ1603-97-003.pdf:3.22MB

no abstracts in English