Estimation of external dose for wild Japanese macaques captured in Fukushima prefecture; Decomposition of electron spin resonance spectrum

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

Radiation Protection Dosimetry, 199(14), p.1620 - 1625, 2023/09

https://doi.org/10.1093/rpd/ncad146

We have been conducting dose assessments for Japanese macaques captured in Fukushima to reveal radiobiological effects on the low-dose expose animals. To accurately determine the external exposure dose, it is desirable to examine the analysis of the CO radical intensity. We examined ESR spectra of teeth of 10 macaques captured in Fukushima by two spectrum-decomposition algorithms.

Development of dose estimation method using wild animal teeth for low dose exposure

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

KEK Proceedings 2021-2, p.91 - 96, 2021/12

We examined whether the ESR dose estimation method could be applied to wild Japanese macaque. In this work, we investigated the enamel preparation protocol and the analytical method of the ESR spectra.

Effects of interaction between molten zircaloy and irradiated MOX fuel on the fission product release behavior

Tanaka, Kosuke; Miwa, Shuhei; Sato, Isamu; Hirosawa, Takashi; Sekine, Shinichi; Osaka, Masahiko; Obayashi, Hiroshi; Koyama, Shinichi

Journal of Nuclear Science and Technology, 51(7-8), p.876 - 885, 2014/07

https://doi.org/10.1080/00223131.2014.896229

As a first step for obtaining experimental data on the effects of high-temperature chemical interaction on fission product (FP) release behavior, we focused on the dissolution of irradiated uranium plutonium mixed oxide (MOX) fuel by molten zircaloy (Zry), and carried out a heating test under the reducing atmosphere. Pieces of an irradiated MOX fuel pellet and cladding were subjected to the heating test at 2373 K for 5 min. The fractional release rate of cesium (specifically Cs) was monitored during the test and its release behavior was evaluated. The observation of microstructures and measurements of elemental distribution in the heated specimen were also performed. We demonstrated experimentally that the fuel dissolution by molten Zry accelerated the release of Cs from the fuel pellets.

Morphology-controlled synthesis of Mo compounds from a nitric acid solution by the microwave heating and/or Zr-addition

Osaka, Masahiko; Tanaka, Kosuke; Sekine, Shinichi; Akutsu, Yoko; Suzuki, Tatsuya*; Mimura, Hitoshi*

Journal of Nuclear Materials, 427(1-3), p.384 - 388, 2012/08

https://doi.org/10.1016/j.jnucmat.2012.05.022

Morphology-controlled synthesis of Mo compounds from a nitric acid solution by microwave heating was investigated for effective utilizations of Mo fission product from a high level nuclear waste. The microwave heating method was revealed to greatly accelerate crystallization and crystal growth of the synthesized powder. Addition of a small amount of Zr stabilized synthesis of a hexagonal-MoO powder. Furthermore, the microwave heating with Zr-addition has synthesized a specific urchin-like shaped hexagonal-MoO crystal having a good crystallinity. The present methods would be useful for effective utilization of Mo from high level nuclear waste in terms of their practicability and ability to the morphology control.

Mercury adsorbent synthesized by graft polymerization onto cellulose nonwoven materials

Sekine, Ayako*; Suzuki, Yoshio*; Seko, Noriaki; Tamada, Masao

JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 42, 2007/02

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2006-042.pdf

no abstracts in English

Effect of Oxygen Potential on the Sintering behavior of MOX fuel containing Am

Miwa, Shuhei; Osaka, Masahiko; Yoshimochi, Hiroshi; Tanaka, Kenya; Seki, Takayuki*; Sekine, Shinichi*

JNC TN9400 2005-023, 43 Pages, 2005/04

JNC-TN9400-2005-023.pdf:3.56MB

The effect of oxygen potential on the sintering behavior of MOX fuel containing Am (Am-MOX) was investigated. Green pellets of Am-MOX were prepared by a conventional powder metallurgical technique. For Am-MOX fuel pellets sintered at various oxygen potential conditions, density measurement, microstructural observation and elements analyses by EPMA were performed High density pellets having good structure were obtained due to oxygen potential change of sintering atmosphere from high oxygen potential to low oxygen potential at 800C in the cooling process.For the pellets sintered at -520 kJ/mol, -390 kJ/mol and -340 kJ/mol, the sintered density increases with increase of oxygen potential up to -390 kJ/mol (threshold oxygen potential), then decreases above the threshold oxygen potential. This tendency is similar to that observed in the (U,Gd)O system. The differences of sintering behavior for Am-MOX pellets which were observed by changing the oxygen potential were attributable to the difference of pore structure, which was supposed to be caused by the valence state of Am in the oxides. On the other hands, the grain size of Am-MOX pellet sintered at -520 kJ/mol was almost the same as that at -390 kJ/mol. Homogeneous distribution of U, Pu and Am was obtained at pellets sintered both -520 and -390 kJ/mol in these sintering conditions. For the pellets sintered at 1500C , 1600C , 1700C , the high dense pellets are obtained, therefore This results shows the the possibility of fabrication of good fuel pellets at lower temperature than 1700C

Phase relation of (U,Pu,Am)O

Osaka, Masahiko; Miwa, Shuhei; Mondo, Kenji; Ozaki, Yoko; Ishi, Yohei; Yoshimochi, Hiroshi; Seki, Takayuki*; Sekine, Shinichi*; Ishida, Takashi*; Tanaka, Kenya

JNC TN9400 2005-002, 40 Pages, 2005/03

JNC-TN9400-2005-002.pdf:2.43MB

An experimental investigation for the phase relation of (U,Pu,Am)O was performed with XRD, ceramography and DTA. Although lattice parameter tended to increase with increases of Am content and O/M ratio, its slope differed from that of (U,Pu)O. A drastic structural change was observed around O/M=1.98. Besides, many DTA peaks, which could never be seen in the case of (U,Pu)O, were observed above O/M=1.98.These results were interpreted with a hypothesis that all Am were trivalent and equivalent amount of U became pentavalent. The dependence of lattice parameter on Am content could be expressed well by using a model with ionic radii of each element. Also the structural change around O/M=1.98 could be explained as caused by valence states of each element. It was concluded from these interpretation that all Am in (U,Pu,Am)O were likely to exist as trivalent state.

Hydraulic experiment for compact reactor vessel; Measurement of flow field and flow optimization in upper plenum

Kimura, Nobuyuki; Hayashi, Kenji; Ito, Masami*; Sekine, Tadashi*; Igarashi, Minoru; Sato, Hiroyuki; Kamide, Hideki

JNC TN9400 2003-032, 214 Pages, 2003/03

JNC-TN9400-2003-032.pdf:111.0MB

An innovative sodium cooled fast reactor has been investigated on the FBR feasibility study. The design of the reactor is undergoing in order to reduce the construction cost of the reactor. For example, thermal output is increased against the reactor size and an upper inner structure (UIS) has a slit for the arm of the fuel-handling machine to simplify the fuel exchanging system. The dipped plates (D/P) are set below the free surface to prevent gas entrainment at free surface. We performed an 1/10th scaled model water experiment for the upper plenum of reactor vessel and investigated flow fields in the plenum in order to optimize flow. In the upper plenum, all of main components were set up as well as the reactor design. In addition, the D/P has a hole in front of the slit of the UIS to insert the fuel handling machine(FHM). As the experimental parameters, the core outlet velocity was varied from the condition of the Froude number similarity to the same value as the real reactor. The local velocity was measured by the particle image velocimetry and the ultrasound Doppler velocimetry. In the experimental results, gas entrainment at the free surface was not observed in the range from the Froude number similarity condition to the same velocity condition as the real reactor. However, the free surface was bulged on a large scale in front of the UIS slit. At the neighborhood of the H/L intake, three vortex cavitations were observed. The vortex cavitations were broken out under the same cavitation coefficient condition based on the H/L velocity as that in the real reactor. A vertical rib was set on the reactor vessel wall near the H/L inlet to restrict the rotating flow at the neighborhood of the H/L. As the result, the vortex cavitation at the region between the reactor vessel wall and the H/L was supressed under the same cavitation factor condition as the real reactor. A vertical cylinder, named FHM plug, was installed to close the hole in the D/P fbr FHM.

Experimental Study on Flow Optimization in Upper Plenum of Reactor Vessel for a Compact Sodium Cooled Fast Reactor

Kimura, Nobuyuki; Hayashi, Kenji; Igarashi, Minoru; Kamide, Hideki; Ito, Masami*; Sekine, Tadashi*

Proceedings of 10th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-10), CD-RO, K0102 Pages, 2003/00

An innovative sodium cooled fast reactor has been investigated on the feasibility study of FBR cycle system in JNC. A compact reactor vessel (R/V) and a column type upper inner structure (UIS) with a radial slit for an arm of a fuel-handling machine (FHM) are adopted. Dipped plates (D/P) are set in the R/V below the free surface to prevent gas entrainment at free surface. We performed an 1/10th scaled model water experiment for the upper plenum of the R/V. Gas entrainment at the free surface was not observed in the experiment under the same velocity condition as the designed reactor. However, the free surface rose in front of the UIS slit due to upward flow through the gap between the D/P and the R/V wall. The upward flow will cause free surface vortex and also the gas entrainment. Three vortex cavitations were observed near the hot leg (H/L) inlet. The vortex cavitations were broken out under the same cavitation factor condition as the reactor. A vertical rib was set on the R/V wall

Power-to-melts of uranium-plutonium oxide fuel pins at a beginning-of-life condition in the experimental fast reactor JOYO

Inoue, Masaki; ; ; ; Sekine, Takashi; Osaka, Masahiko

Journal of Nuclear Materials, 323(1), p.108 - 122, 2002/00

https://doi.org/10.1016/j.jnucmat.2003.08.030

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