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Journal Articles

Short summary of LLW disposal project and NORM guidelines in Japan

Saito, Tatsuo

FNCA Radiation Safety and Radioactive Waste Management Newsletter (Internet), (17), p.6 - 7, 2022/03

In the Asian Nuclear Cooperation Forum (FNCA) newsletter, the mechanism for disposal of low-level radioactive waste generated from nuclear research facilities and facilities using RI was briefly explained. The outline of domestic guidelines on the handling of NORM was also explained, which has been the theme of FNCA since last year.

Journal Articles

Growing need for humanities and social science studies in uranium waste disposal

Yasuda, Hiroshi*; Fumoto, Hiromichi*; Saito, Tatsuo

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 63(8), p.610 - 614, 2021/08

Regarding the handling of uranium bearing waste, which is contaminated with uranium, which is a naturally occurring radionuclide, and its descendant nuclides, in recent years, the Japan Nuclear Regulatory Commission, etc. have been carefully and actively deliberated based on the knowledge of natural science and safety engineering. It was carried out, and as of March 2021, a certain policy has been shown. On the other hand, when disposing of uranium waste, which may cause dose exposure to future generations, the authors consider not only the science and engineering perspectives that have been conducted so far, but also the humanities and social science perspectives. We have been discussing with experts in related fields, thinking that it is necessary. In this report, we will introduce the background that brought about such an idea and the direction of future discussions.

Journal Articles

Conceptual design of an abnormality sign determination system for the general control system of the Materials and Life Science Experimental Facility at J-PARC

Sakai, Kenji; Oi, Motoki; Teshigawara, Makoto; Naoe, Takashi; Haga, Katsuhiro; Watanabe, Akihiko*

Journal of Neutron Research, 22(2-3), p.337 - 343, 2020/10

For operating a spallation neutron source and a muon target safely and efficiently, a general control system (GCS) operates within Materials and Life Science Experimental Facility (MLF). GCS administers operation and interlock processes of many instruments under various operation status. Since the first beam injection in 2008, it has operated stably without any serious troubles for more than ten years. GCS has a data storage server storing operational data on status around target stations. It has functioned well to detect and investigate unusual situations by checking data in this server. For continuing stable operation of MLF in future, however, introduction of abnormality sign determination system (ASDS) will be necessary for picking up potential abnormalities of target stations caused by radiation damages, time-related deterioration and so on. It will judge abnormalities from slight state transitions of target stations based on analysis with various operational data throughout proton beams, target stations, and secondary beams during long-term operations. This report mentions present status of GCS, conceptual design of ASDS, and installation of an integral data storage server which can deal with various data for ASDS integrally.

Journal Articles

Estimation of sensitivity coefficient based on lasso-type penalized linear regression

Katano, Ryota; Endo, Tomohiro*; Yamamoto, Akio*; Tsujimoto, Kazufumi

Journal of Nuclear Science and Technology, 55(10), p.1099 - 1109, 2018/10

 Times Cited Count:3 Percentile:39.5(Nuclear Science & Technology)

In this study, we propose the penalized regression "adaptive smooth-lasso" for the estimation of sensitivity coefficients of the neutronics parameters. The proposed method estimates the sensitivity coefficients of the neutronics parameters using the variation of the microscopic cross sections and the neutronics parameter obtained by random sampling. The proposed method utilizes only the forward calculations. Thus, the proposed method can be applied for the complex reactor analysis for which the application of the adjoint method is difficult. In this study, we proposed a penalty term considering the characteristics of the sensitivity coefficients of the neutronics parameter to the microscopic multi-group cross sections. Through verification calculation, we show that the proposed method achieves high accuracy with less computational cost compared to the method based on random sampling proposed in the previous studies.

Journal Articles

Dimension-reduced cross-section adjustment method based on minimum variance unbiased estimation

Yokoyama, Kenji; Yamamoto, Akio*; Kitada, Takanori*

Journal of Nuclear Science and Technology, 55(3), p.319 - 334, 2018/03

 Times Cited Count:6 Percentile:64.21(Nuclear Science & Technology)

A new formulation of the cross-section adjustment methodology with the dimensionality reduction technique has been derived. This new formulation is proposed as the dimension reduced cross-section adjustment method (DRCA). Since the derivation of DRCA is based on the minimum variance unbiased estimation (MVUE), an assumption of normal distribution is not required. The result of DRCA depends on a user-defined matrix that determines the dimension reduced feature subspace. We have examine three variations of DRCA, namely DRCA1, DRCA2, and DRCA3. Mathematical investigation and numerical verification have revealed that DRCA2 is equivalent to the currently widely used cross-section adjustment method. Moreover, DRCA3 is found to be identical to the cross-section adjustment method based on MVUE, which has been proposed in the previous study.

Journal Articles

A High-precision calculation method for interface normal and curvature on an unstructured grid

Ito, Kei; Kunugi, Tomoaki*; Ohno, Shuji; Kamide, Hideki; Ohshima, Hiroyuki

Journal of Computational Physics, 273, p.38 - 53, 2014/09

 Times Cited Count:13 Percentile:67.38(Computer Science, Interdisciplinary Applications)

Journal Articles

Neural-net predictor for beta limit disruptions in JT-60U

Yoshino, Ryuji

Nuclear Fusion, 45(11), p.1232 - 1246, 2005/11

 Times Cited Count:36 Percentile:74.89(Physics, Fluids & Plasmas)

Prediction of major disruptions observed at the $$beta$$-limit for tokamak plasmas has been investigated in JT-60U with developing neural networks. A sub-neural network is trained to output a value of the $$beta$$$$_{N}$$ limit every 2 ms. The target $$beta$$$$_{N}$$ limit is artificially set by the operator in the first step training and is modified in the second step training using the output $$beta$$$$_{N}$$ limit from the trained network. To improve the prediction performance further, the difference between the estimated $$beta$$$$_{N}$$ limit and the measured $$beta$$$$_{N}$$ and the other 11 parameters are inputted to a main neural network to calculate the stability level. Major disruptions have been predicted with a prediction success rate of 80% at 10 ms prior to the disruption while the false alarm rate is lower than 4%. This 80% is much higher than about 10% previously obtained. A prediction success rate of 90% has been also obtained with a false alarm rate of 12% at 10 ms prior to the disruption. This 12% is about a half of previously obtained one.

Journal Articles

Rapid normal zone propagation observed in a 13 T-46 kA Nb$$_{3}$$Al cable-in-conduit conductor

Koizumi, Norikiyo; Matsui, Kunihiro; Kume, Etsuo; Okuno, Kiyoshi

IEEE Transactions on Applied Superconductivity, 15(2), p.1363 - 1366, 2005/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

The Nb$$_{3}$$Al Insert was developed by JAERI aiming at the demonstration of a Nb$$_{3}$$Al conductor to fusion reactor magnets. A quench test was performed on the Nb$$_{3}$$Al Insert at 13 T with various temperature margins, which are defined as a difference between current sharing temperature and operating temperature. The initial normalcy was initiated by using an inductive heater and a coil current was kept for several seconds. The normal zone propagation velocity was accelerated after 3 s from the onset of heating in case that the temperature margin was set at 0.5 K. A simulation using one-dimensional stability and quench simulation code was performed. The calculation results indicate that such rapid propagation occurred due to a temperature rise beyond a current sharing temperature because of a large pressure increase even at the location where the normal front did not reach yet. This large pressure rise was caused since the coolant was contained in the closed circulation circuit of the cooling system, which is usually applied to a large magnet cooling system.

Journal Articles

Normal-mode analysis of circular DNA at the base-pair level, 1; Comparison of computed motions with the predicted behavior of an ideal elastic rod

Matsumoto, Atsushi; Tobias, I.*; Olson, W. K.*

Journal of Chemical Theory and Computation, 1(1), p.117 - 129, 2005/01

 Times Cited Count:11 Percentile:36.74(Chemistry, Physical)

We have extended a newly developed approach to study the low frequency normal modes of mesoscopic fragments of linear DNA in order to investigate the dynamics of closed circular molecules of comparable size, i.e., a few hundred base pairs. We have added restraint energy terms and a global minimization step to treat the more complicated, spatially constrained duplex in terms of the intrinsic conformation and flexibility of the constituent base-pair "step" parameters.

Journal Articles

Normal-mode analysis of circular DNA at the base-pair level, 2; Large-scale configurational transformation of a naturally curved molecule

Matsumoto, Atsushi; Tobias, I.*; Olson, W. K.*

Journal of Chemical Theory and Computation, 1(1), p.130 - 142, 2005/01

 Times Cited Count:9 Percentile:31(Chemistry, Physical)

Fine structural and energetic details embedded in the DNA base sequence, such as intrinsic curvature, are important to the packaging and processing of the genetic material. Here we investigate the internal dynamics of a 200 bp closed circular molecule with natural curvature using a newly developed normal-mode treatment of DNA in terms of neighboring base-pair "step" parameters. As superhelical stress is accumulated in the DNA, the frequency, i.e., energy, of the dominant bending mode decreases in value, and if the imposed stress is sufficiently large, a global configurational rearrangement of the circle to the figure-8 form takes place. We combine energy minimization with normal-mode calculations of the two states to decipher the configurational pathway between the two states.

Journal Articles

Hazard analysis approach with functional FMEA in PSA procedure for MOX fuel fabrication facility

Tamaki, Hitoshi; Yoshida, Kazuo; Watanabe, Norio; Muramatsu, Ken

Proceedings of International Topical Meeting on Probabilistic Safety Analysis (PSA '05) (CD-ROM), 11 Pages, 2005/00

A probabilistic safety assessment (PSA) procedure for Mixed Oxide (MOX) fuel fabrication facilities is being developed applicable to nuclear facilities at Japan Atomic Energy Research Institute (JAERI). As part of the PSA procedure, the approach to hazard analysis was established, which consists of two analysis steps: Functional Failure Modes and Effects Analysis (Functional FMEA) and Risk Matrix Analysis. In the Functional FMEA, a variety of functions of equipment composing the facility are analyzed to identify potential abnormal events exhaustively. In the second step, these potential events are screened to select abnormal events as candidate events to be analyzed for frequency and consequence by using two-dimensional matrix based on the rough estimation of likelihood and maximum unmitigated release of radioactive material. The applicability of the hazard analysis approach established was demonstrated through the trial application of the PSA procedure being developed to model plant of MOX fuel fabrication facility.

Journal Articles

Role of low order rational $$q$$-values in the ITB events in JT-60U reverse shear plasmas

Neudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro

Nuclear Fusion, 44(9), p.945 - 953, 2004/09

The formation of internal transport barriers (ITBs) near q=3 surfaces in normal shear (NrS) discharges of JT-60U is known. In reverse shear (RS) JT-60U plasmas, the role of q minimum (qmin) equal to 3.5,3,2.5,2 was not obvious for ITB formation. ITB-events (non-local confinement bifurcations inside and around ITB) are found in various NrS and RS plasmas. Under sufficient heating power, ITB-events are seen at rational and not rational values of qmin. The space-time evolution of Te and Ti is similar, suggesting the same mechanism of Te and Ti transport. The temporal formation of strong ITB under passing of qmin=3 (after periodical improvements and degradations via ITB-events) in RS mode is presented. Under smaller power, ITB-events are observed only at rational values of qmin. In a weak RS shot, abrupt rise of Te is seen at qmin=3.5, while more cases of Ti rise are observed. The difference of Te and Ti evolutions seen regularly under the low power, suggests decoupling of Te and Ti transport.

Journal Articles

Role of low order rational ${it q}$-values in the ITB events in JT-60U reverse shear plasmas

Neudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro

Nuclear Fusion, 44(9), p.945 - 953, 2004/09

 Times Cited Count:15 Percentile:46.65(Physics, Fluids & Plasmas)

The formation of internal transport barriers (ITBs) near ${it q}$ =2,3 surfaces in normal shear (NrS) discharges of JT-60U and JET is known. In reverse shear (RS) JT-60U plasmas, the role of ${it q}$ minimum (${it q}$$$_{min}$$) equal to 3.5,3,2.5,2 is not obvious for ITB formation. In this paper, the effect of low rational ${it q}$ values on ITB-events in JT-60U NrS and RS plasmas is investigated. Under sufficient neutral beam power (${it P}$$$_{nbi}$$$$>$$8MW for 1.2-1.5MA/3.8T pulses), ITB-events are seen at rational and non-rational values of ${it q}$$$_{min}$$. The space-time evolutions of ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ are similar, suggesting the same mechanism for ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ transports. The temporal formation of stronger ITB under passing ${it q}$$$_{min}$$=3 (after periodical improvements and degradations via ITB-events) in RS H-mode with ${it P}$$$_{nbi}$$=8MW is presented. Under smaller power, ITB-events are observed only at rational ${it q}$$$_{min}$$ values. In a weak RS shot with ${it P}$$$_{nbi}$$=4MW, the abrupt rise of ${it T}$$$_{e}$$ is seen at ${it q}$$$_{min}$$=3.5, while more cases of ${it T}$$$_{i}$$ rise are observed. The difference between the ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ evolutions for the low power suggests the decoupling of ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ transports.

Journal Articles

On the poloidal localization and stability of multi-faceted asymmetric radiation from the edge (MARFE)

Chankin, A. V.

Physics of Plasmas, 11(4), p.1484 - 1492, 2004/04

 Times Cited Count:9 Percentile:30.24(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Development of facility for in-situ observation during slow strain rate test for irradiated materials

Nakano, Junichi; Tsukada, Takashi; Tsuji, Hirokazu; Terakado, Shogo; Koya, Toshio; Endo, Shinya

JAERI-Tech 2003-092, 54 Pages, 2004/01

JAERI-Tech-2003-092.pdf:14.05MB

Irradiation assisted stress corrosion cracking (IASCC) is a degradation phenomenon caused by synergy of neutron radiation, aqueous environment and stress on in-core materials, and it is an important issue in accordance with increase of aged light water reactors. Isolating crack initiation stage from crack growth stage is very useful for the evaluation of the IASCC behavior. Hence facility for in-situ observation during slow strain rate test (SSRT) for irradiated material was developed. As performance demonstrations of the facility, tensile test with in-situ observation and SSRT without observation were carried out using unirradiated type 304 stainless steel in 561 K water at 9 MPa. The following were confirmed from the results. (1) Handling, observation and recording of specimen can be operated using manipulators in the hot cell. (2) In-situ observation can be performed in pressurized high temperature water and flat sheet type specimen is suitable for the in-situ observation. (3) Test condition can be kept constantly and data can be obtained automatically for long test period.

Journal Articles

Nuclear power plant simulation using multilayer perceptron

Ono, Tomio*; Subekti, M.*; Maruyama, Yuta*; Nabeshima, Kunihiko; Kudo, Kazuhiko*

Dai-13-Kai Interijento, Shisutemu, Shimpojiumu Koen Rombunshu, p.212 - 217, 2003/12

In this research, we present nuclear power plant simulation method using Multilayer Perceptron, which is one of the models of Artificial Neural Networks(ANNs). The major characteristics of ANNs are to obtain the model through learning, analogy and very high speed processing. Furthermore, 'time synchronizing signal' and 'progress synchronizing signal' are added as the inputs to adapt the abnormal events with various scales or progress rates. This ANN, learned some sample data, can be flexibly adapted to simulate the abnormal events with different scales including explicit progress rates. In the verification using PWR simulator, we confirmed that this method could model NPP abnormal events by learning data and simulate the data which have different progress rates from learning data.

Journal Articles

Influence of superfluidity on recombination reactions of H+T$$rightarrow$$HT and T+T$$rightarrow$$T$$_{2}$$ in $$^{3}$$He-$$^{4}$$He quantum media under saturated vapor pressure at 1.6 K

Aratono, Yasuyuki; Iguchi, Kazunari; Okuno, Kenji*; Kumada, Takayuki

Journal of Physical Chemistry A, 107(19), p.3741 - 3746, 2003/05

 Times Cited Count:4 Percentile:12.11(Chemistry, Physical)

An influence of superfluidity on recombination reactions of H+T$$rightarrow$$HT, T+T$$rightarrow$$T$$_{2}$$ in $$^{3}$$He-$$^{4}$$He quantum media was studied under saturated vapor pressure at 1.6 K. A change of reaction mechanism was observed at transition point from normalfluid to superfluid phase. Tunneling reaction mechanism by H and T bubble atoms was proposed on the basis of large isotope effect.

JAEA Reports

Mechanical properties changes of high burnup PWR fuel cladding by temperature transient

Nagase, Fumihisa; Uetsuka, Hiroshi

JAERI-Research 2002-023, 23 Pages, 2002/11

JAERI-Research-2002-023.pdf:1.94MB

To obtain basic data to evaluate fuel rod integrity during abnormal transient and accident of LWRs, high burnup PWR fuel claddings were heated for 0 to 600s at temperatures of 673 through 1173K, and the mechanical property changes were examined by using ring tensile test at room temperature. As a result of the test, it was shown that strength and ductility of the cladding are changed depending on heating temperature and time. The mechanical property changes by temperature transients are considered to be correspondent mainly to recovery of irradiation defect, recovery and recrystallization of the Zircaloy, phase transformations, and associated change of the hydride distribution and morphology. Comparison with unirradiated claddings suggested that irradiation effects are not completely annealed out by the short-term annealing at high temepratures. Radial change of hydrogen concentration was measured for the high burnup PWR fuel cladding and very high hydrogen concentration of about 2400wtppm was detected at the cladding periphery.

Journal Articles

Tritium dose assessment Code; ACUTRI and TRINORM

Noguchi, Hiroshi; Yokoyama, Sumi*

KURRI-KR-80, p.50 - 56, 2002/08

no abstracts in English

JAEA Reports

Proceedings of the 24th NSRR Technical Review Meeting; Tokyo, November 13-14, 2000

Fuel Safety Research Laboratory

JAERI-Conf 2001-010, 303 Pages, 2001/09

JAERI-Conf-2001-010.pdf:59.22MB

The 24th NSRR Technical Review Meeting was held at Tranomon Pastoral, Tokyo, on November 13 and 14, 2000. The purpose of the meeting was to present and discuss the recent progress of the NSRR program and other LWR fuel safety researches at JAERI. Twenty-one papers, including five by foreign institutes, were presented and discussed regarding fuel behavior during normal operation, reactivity initiated accident (RIA) and loss-of-coolant accident (LOCA) and FP release behavior during severe accident. The meeting was a great help in planning future research and promoting research cooperation. This proceeding contains the papers presented in the meeting.

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