Evaluation of decay heat used for effectiveness evaluations of countermeasures against severe accidents in the prototype FBR Monju

Usami, Shin; Kishimoto, Yasufumi*; Taninaka, Hiroshi; Maeda, Shigetaka

JAEA-Technology 2018-003, 97 Pages, 2018/07

JAEA-Technology-2018-003.pdf:12.54MB

The decay heat used for effectiveness evaluation of the prevention measures against severe accidents in the prototype fast breeder reactor Monju was evaluated by applying the updated nuclear data libraries based on JENDL-4.0, reflecting the realistic core operation pattern, and setting the rational extent of uncertainty. The decay heats of fission products, the actinide nuclides such as Cm-242, and radioactive structural materials were calculated by FPGS code. The decay heat of U-239 and Np-239 was evaluated based on ANSI/ANS-5.1-1994. The calculation uncertainty of each decay heat was evaluated based on summation of uncertainty factors, C/E values of reaction rates obtained in Monju system startup test, and so on. Furthermore, the decay heat evaluation method based on the FPGS90 was verified by the comparison of the results of the decay heat measurement of the two spent MOX fuel subassemblies in the experimental fast reactor Joyo MK-II core.

Emergent Weyl fermion excitations in TaP explored by Ta quadrupole resonance

Yasuoka, Hiroshi; Kubo, Tetsuro*; Kishimoto, Yasuki*; Kasinathan, D.*; Schmidt, M.*; Yan, B.*; Zhang, Y.*; To, Hideki*; Felser, C.*; Mackenzie, A. P.*; et al.

Physical Review Letters, 118(23), p.236403_1 - 236403_6, 2017/07

https://doi.org/10.1103/PhysRevLett.118.236403

The Ta quadrupole resonance (NQR) technique has been utilized to investigate the microscopic magnetic properties of the Weyl semi-metal TaP. We found three zero-field NQR signals associated with the transition between the quadrupole split levels for Ta with =7/2 nuclear spin. A quadrupole coupling constant, = 19.250 MHz, and an asymmetric parameter of the electric field gradient, = 0.423 were extracted, in good agreement with the theoretical calculations. In order to examine the magnetic excitations, the temperature dependence of the spin lattice relaxation rate (1/) has been measured for the -line ( transition). We found that there exist two regimes with quite different relaxation processes. Above *K, a pronounced ( behavior was found which is attributed to the magnetic excitations at the Weyl nodes with temperature dependent orbital hyperfine coupling. Below *, the relaxation is mainly governed by Korringa process with (1/) = constant, while we have to include a type dependence in order to reproduce our experimental data. We show that Ta-NQR is a novel probe for the bulk Weyl fermions and their excitations.

A Scrutinized analysis on the power reactivity loss measurement in Monju

Taninaka, Hiroshi; Kishimoto, Yasufumi; Mori, Tetsuya; Usami, Shin

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.2610 - 2621, 2016/05

Reactivity loss due to power ascension (power reactivity loss or power coefficient of reactivity) is thus an important design parameter for determining the number of CRs and plutonium content or inventory in the SFR core design, along with the burnup reactivity loss. Measurements on these reactivity losses were therefore performed during the system startup tests in the Japanese prototype SFR Monju in 1995 and analyses have been carried out for several times. The most recent analysis on the power coefficient measurement in Monju was presented by Takano (Takano, et al., 2008). The following latest findings, which have not been taken into account in the past analyses, are available at present and may affect the existing results: (a) in-core temperature distribution effect, (b) crystalline binding effect, (c) logarithmic averaging of the fuel temperature, (d) localized fuel thermal elongation effect, (e) updated Japanese Evaluated Nuclear Data Library, JENDL-4.0, and (f) refined corrections on the measured value. The influences of refining the calculational models and measured value corrections were therefore quantitatively identified in this study by considering all of these new findings. As a result, it was revealed that the analysis overestimates the experiment by 8.1% for the total uncertainty of 5.9%. Therefore, an additional effect, that is the core bowing effect, was considered in the calculation, and the discrepancy was reduced to 2.9%. The possibility of a significant contribution from the core bowing or deformation effect was thus suggested.

Zn nanoparticles irradiated with swift heavy ions at low fluences; Optically-detected shape elongation induced by nonoverlapping ion tracks

Amekura, Hiroshi*; Ishikawa, Norito; Okubo, Nariaki; Ridgway, M.*; Giulian, R.*; Mitsuishi, Kazuki*; Nakayama, Yoshiko*; Buchal, C.*; Mantl, S.*; Kishimoto, Naoki*

Physical Review B, 83(20), p.205401_1 - 205401_10, 2011/05

https://doi.org/10.1103/PhysRevB.83.205401

Elongation of metal nanoparticles (NPs) embedded in silica induced by swift heavy-ion irradiation, from spheres to spheroids, has been evaluated at low fluences by linearly polarized optical absorption spectroscopy. It is important to clarify whether the high fluences, i.e., track overlaps, are essential for the elongation. Zn NPs embedded in silica were irradiated with 200-MeV Xe ions. The comparison with numerical simulation suggested that the elongation of Zn NPs was induced by nonoverlapping ion tracks.

Intensity correlation measurement system by picosecond single shot soft X-ray laser

Kishimoto, Maki; Namikawa, Kazumichi*; Sukegawa, Kota*; Yamatani, Hiroshi*; Hasegawa, Noboru; Tanaka, Momoko

Review of Scientific Instruments, 81(1), p.013905_1 - 013905_5, 2010/01

AA2009-0790.pdf:0.78MB

https://doi.org/10.1063/1.3280173

We developed a new soft X-ray speckle intensity correlation spectroscopy system by use of a single shot high brilliant plasma soft X-ray laser. The plasma soft X-ray laser is characterized by several picoseconds in pulse width, more than 90% special coherence, and 10 soft X-ray photons within a single pulse. We developed a Michelson type delay pulse generator using a soft X-ray beam splitter to measure the intensity correlation of X-ray speckles from materials and succeeded in generating double coherent X-ray pulses with picosecond delay times. Moreover, we employed a high-speed soft X-ray streak camera for the picosecond time-resolved measurement of X-ray speckles. We performed the X-ray speckle intensity correlation measurements for probing the relaxation phenomena of polarizations in polarization clusters in the paraelectric phase of the ferroelectric material BaTiO near its Curie temperature and verified its performance.

High-resolution spectroscopy of the nickel-like molybdenum X-ray laser toward the generation of circularly polarized X-ray laser

Hasegawa, Noboru; Sasaki, Akira; Yamatani, Hiroshi; Kishimoto, Maki; Tanaka, Momoko; Ochi, Yoshihiro; Nishikino, Masaharu; Kunieda, Yuichi; Kawachi, Tetsuya; Yoneda, Hitoki*; et al.

Journal of the Optical Society of Korea, 13(1), p.60 - 64, 2009/03

https://doi.org/10.3807/JOSK.2009.13.1.060

The precise knowledge about the spectral width of the X-ray laser line is important to generate the circularly polarized X-ray laser. There are three magnetic sub-levels at lower state of the collisional excitation X-ray laser transition of the nickel-like ion X-ray laser medium. The polarization of each transition is circular or linear. Therefore the circularly polarized X-ray laser could be extracted by the influence of the Zeeman effect if the X-ray laser medium was under the external magnetic field. The strength of the magnetic field required for the circularly polarized X-ray laser is determined by the spectral width of the X-ray laser. Only a few measurements of the spectral width of the laser line have been reported, because the spectral width of the X-ray laser is so narrow that the required spectral resolution is quite high. In this study, we took the nickel-like molybdenum X-ray laser as an example and succeeded the measurement of the spectral width of the X-ray laser.

Nonlinear behaviour of collisionless double tearing mode induced by electron inertia

Matsumoto, Taro; Naito, Hiroshi*; Tokuda, Shinji; Kishimoto, Yasuaki*

Nuclear Fusion, 45(11), p.1264 - 1270, 2005/11

https://doi.org/10.1088/0029-5515/45/11/006

A gyrokinetic particle simulation is executed to clarify the effect of the electron inertia on the MHD phenomena in the reversed shear configuration (RSC) of a cylindrical tokamak plasma. It is found that the collisionless (kinetic) double tearing modes grow up at the Alfvn time scale, and nonlinearly induce the internal collapse when the helical flux at the magnetic axis is less than that at the outer resonant surface. After the internal collapse, the secondary reconnection is induced by the current concentration due to the convective flow. It is also clarified that a nonlinear dynamics accompanied with the elementary processes caused by the flow can generate a new RSC with resonant surfaces. In the presence of the density gradient, after the full reconnection induced by the mode, the radial electric field is found to be generated due to the difference of the motion between ions and electrons. However, the intensity of the radial field is not so large as that induced by the collisionless kink mode.

Advanced tokamak research on JT-60

Kishimoto, Hiroshi; Ishida, Shinichi; Kikuchi, Mitsuru; Ninomiya, Hiromasa

Nuclear Fusion, 45(8), p.986 - 1023, 2005/08

https://doi.org/10.1088/0029-5515/45/8/026

The Japanese large tokamak JT-60 has been focusing its research emphases to develop a high performance plasma, namely high confinement, high temperature and high density, and to sustain it non-inductively for a long time with possible minimization of external power input. The first demonstration of high bootstrap current discharges in a high-poloidal-beta mode (high-p) and the concept development of a steady-state tokamak reactor SSTR based on this experimental achievement initiated the so-called "advanced tokamak research". The first observation of internal transport barriers in the JT-60 high-p mode was followed by the world-wide explorations of reversed shear discharges associated with internal transport barriers. The advanced tokamak research is now the major trend of the current tokamak development. A new concept of compact ITER was developed and proposed in the context of this advanced tokamak approach pursued on JT-60.

Present status of JRR-2 decommissioning

Nakano, Masahiro; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki

Dekomisshoningu Giho, (30), p.11 - 24, 2004/09

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_30.pdf

Japan Research Reactor No.2(JRR-2), heavy water moderated and cooled tank type research reactor with maximum thermal power of 10MW,was operated for over 36 years, and was permanently shut down in December, 1996. In 1997, decommissioning plan was submitted to the STA, and dismantling was begun. Decommissioning program of JRR-2 is divided into 4 phases. Phase 1, 2 had already been completely finished without any trouble. Furthermore, the phase 3 was also finished in February, 2004 as planned. On exposure of worker in phase 1, 2 and 3, it was achieved to control lower than the estimate. On exposure of worker in phase 1, 2 and 3, it was achieved to control lower than the estimate. Reactor will be removed in phase 4 by one piece removal technique. The reactor building is planned to use effectively as a hot experimental facilities after decommissioning. The decommissioning plan was changed that the reactor would be kept in safety storage.

JRR-2 decommissioning activity, 1

Nakano, Masahiro; Arigane, Kenji; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki; Sakuraba, Naotoshi; Oba, Nagamitsu

JAERI-Tech 2003-072, 92 Pages, 2003/08

JAERI-Tech-2003-072.pdf:6.99MB

The decommissioning plan of the Japan Research reactor No2(JRR-2), decommissioning activities until the first half of phase-3, radioactive wastes and exposure dose of workers are described in this report. Since the first criticality in October 1960, JRR-2 had been operated about 36 years for various experiments. However, JRR-2 was permanent shutdown in December 1996 based on JAERI's long term plan, and the decommissioning of the JRR-2 was started in August 1997. Decommissioning of the JRR-2 was planed for 11 years from 1997 to 2007 and the program was divided into 4 phases. The decommissioning activities of the phase-1, phase-2 and the first half of phase-3 had already completed as planned in March 1998, February 2000, March 2002, respectively. The decommissioning activities of the later half of Phase-3 (dismantling of the reactor cooling systems) are carrying out at present time with planed 2002 and 2003 fiscal years.