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Journal Articles

Performance evaluation of eddy current flowmeter in Monju

Aizawa, Kosuke; Chikazawa, Yoshitaka; Morohashi, Yuko

Journal of Nuclear Science and Technology, 55(12), p.1393 - 1401, 2018/12

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Measurement of the temperature and flow rate at each fuel subassembly outlet is an effective way for a liquid metal fast breeder reactor to detect a loss of coolant accident or reactivity-initiated accident in the early stage and to understand the reactor's thermal hydrodynamic performance. Japan Atomic Energy Agency has developed the eddy current flowmeter in practical use and installed 34 of them in the upper core structure of fast breeder reactor, Monju. This report presents data obtained by using the flowmeters in Monju. We observed high linearity between each of the flowmeter's signal intensity and the primary sodium's flow rate under 10-100% flow rate condition. The fluctuation of flow rate observed by the flowmeters was below 0.2 m/s which is 5% of the time-averaged velocity under a rated condition. These experimental results show that the eddy current flowmeter is an effective tool to detect the changes in relative flow rate.

Journal Articles

Demonstration of eddy current type flow meter in Monju

Aizawa, Kosuke; Chikazawa, Yoshitaka; Morohashi, Yuko

Proceedings of 2016 International Congress on Advances in Nuclear Power Plants (ICAPP 2016) (CD-ROM), p.314 - 320, 2016/04

Temperature and flow rate measurement of each fuel subassembly outlet is effective to detect loss of coolant accident (LOCA) and reactivity initiated accident (RIA) early and to understand a thermal hydrodynamic performance in liquid metal fast breeder reactor (LMFBR). This report shows the data of eddy current type flow meters in Monju. High linearity between the signal intensity of each eddy current type flow meter and flow rate of primary sodium was obtained in the flow rate condition of 10$$sim$$100%. In addition, the linearity was also demonstrated in the low velocity region, approx. 0.25 m/s. Fluctuation shown on each eddy current type flow meter was below 0.2 m/s, which is 5 % of the time averaged velocity at the rated condition. Those experimental results show that the eddy current type flow meter can detect the change of relative flow rate.

JAEA Reports

Performance confirmation of MONJU failed fuel detection and location system, 1

Morohashi, Yuko; Suzuki, Satoshi

JAEA-Technology 2014-045, 116 Pages, 2015/03

JAEA-Technology-2014-045.pdf:33.37MB

The failed fuel detection and location (FFDL) system collects the tagging gas that migrates into the reactor cover gas from a failed pin. The tagging gas is made of stable isotopes of Kr and Xe. The isotopic composition of the tagging gas can be made specific to each assembly. The assembly containing a failed fuel pin can be identified by analyzing the isotopic composition. The FFDL system is comprised of two tagging gas concentration devices. The concentration rate is designed to be higher than 200. Past examinations demonstrated that the concentration rate meets the requirement with a noble gas concentration of 1ppm. However, the actual noble gas concentration emitted from a failed fuel is assumed to be much lower. In the present study, the performance of FFDL system was investigated by measuring low concentration gas of the actual fuel failure level. As a result, the concentration rate was confirmed to be more than tens of thousands, which sufficiently satisfies the design demand.

Journal Articles

Performance confirmation of Monju failed fuel detection and location system

Morohashi, Yuko; Suzuki, Satoshi

Proceedings of 2014 International Congress on the Advances in Nuclear Power Plants (ICAPP 2014) (CD-ROM), p.624 - 630, 2014/04

Monju has failed fuel detection systems which consist of the delayed neutron (DN) monitoring system, the cover gas (CG) monitoring system, and the failed fuel detection & location (FFDL) system based on the tagging gas analysis. The DN method and the CG method are used to watch the integrity of fuel assemblies continuously. When a fuel failure of pin-hole level is detected by the CG monitoring, the FFDL system starts operation to identify the location of the failed fuel assembly in the reactor core. In case of a larger fuel failure, the DN monitoring system works and the reactor shuts down automatically. The FFDL system collects the tagging gas which migrates into the reactor cover gas from a failed pin. The tagging gas is made of stable isotopes of Kr and Xe. 270 types of isotopic composition are available using 15 types for Kr and 9 types for Xe. Thus, the isotopic composition of the tagging gas can be made specific to each assembly. The assembly containing a failed fuel pin in the reactor core can be identified by analyzing the isotopic composition. The FFDL system is comprised of two tagging gas concentration devices. The device collects and concentrates the tagging gas by adjusting temperature of activated carbon from 110 K to 420 K. The concentration rate is designed to be higher than 200. In the past examination performed, it was confirmed that the concentration rate meets the requirement with a noble gas concentration of 1 ppm. However, the actual noble gas concentration emitted from a failed fuel is assumed to be much lower. In the present study, the performance of FFDL system was demonstrated by measuring low concentration gas of the actual fuel failure level. The sample gas of concentrations ranging 0.1 ppb to 10 ppb was used. As a result, the concentration rate was confirmed to be more than tens of thousands, which sufficiently satisfies the design demand. Moreover, it was confirmed that the concentration dependence of noble gas was small.

JAEA Reports

Core confirmation test in system startup test of the fast breeder reactor MONJU

Jo, Takahisa; Goto, Takehiro; Yabuki, Kentaro; Ikegami, Kazunori; Miyagawa, Takayuki; Mori, Tetsuya; Kubo, Atsuhiko; Kitano, Akihiro; Nakagawa, Hiroki; Kawamura, Yoshiaki; et al.

JAEA-Technology 2010-052, 84 Pages, 2011/03

JAEA-Technology-2010-052.pdf:17.14MB

The prototype fast breeder reactor MONJU resumed the System Startup Test (SST) on May 6th 2010 after five months and fourteen years shutdown since the sodium leakage of the secondary heat transport system on December 1995. Core Confirmation Test (CCT) is the first step of SST, which consists of three steps. CCT was finished on July 22nd after 78 days tests. CCT is composed 20 test items including control rods' worth evaluation, radiation dose measurement etc..

Journal Articles

Neutron irradiation effect on isotopically tailored $$^{11}$$B$$_{4}$$C

Morohashi, Yuko; Maruyama, Tadashi*; Donomae, Takako; Tachi, Yoshiaki; Onose, Shoji

Journal of Nuclear Science and Technology, 45(9), p.867 - 872, 2008/09

 Times Cited Count:9 Percentile:56.05(Nuclear Science & Technology)

Journal Articles

Neutron irradiation effects on $$^{11}$$B$$_{4}$$C and recovery by annealing

Donomae, Takako; Tachi, Yoshiaki; Sekine, Manabu*; Morohashi, Yuko; Akasaka, Naoaki; Onose, Shoji

Journal of the Ceramic Society of Japan, 115(1345), p.551 - 555, 2007/09

 Times Cited Count:4 Percentile:30.7(Materials Science, Ceramics)

Use of moderator materials in Fast Breeder Reactor (FBR) is effective for transmutation technology, and $$^{11}$$B$$_{4}$$C is one of the candidates. Up to now, the behavior of $$^{10}$$B$$_{4}$$C as the Control rod material is well known, but that of $$^{11}$$B$$_{4}$$C is hardly investigated. In this paper, the radiation effects of $$^{11}$$B$$_{4}$$C pellets, neutron irradiated in the experimental fast reactor JOYO were studied. From the experimental results, it was observed that no macro-cracks were recognized in the irradiated $$^{11}$$B$$_{4}$$C pellets. But, bubble nucleation was found in grain and along grain boundaries of $$^{11}$$B$$_{4}$$C. And, it was shown that the conductivity of $$^{11}$$B$$_{4}$$C was higher than that of $$^{10}$$B$$_{4}$$C. During the annealing from room temperature to 1400$$^{circ}$$C, three recovery stages were found on thermal conductivity. It was suggested that, the recovery of B$$_{4}$$C was related to the dispersion behavior of helium. Judging from these results, as $$^{11}$$B$$_{4}$$C was mechanically more stable compared with $$^{10}$$B$$_{4}$$C under irradiation, it was shown that $$^{11}$$B$$_{4}$$C had high applicability for a moderator.

JAEA Reports

JOYO MK-III Performance Test; Isothermal Temperature Coefficient Measurement (NT-333)

Yokoyama, Kenji; Morohashi, Yuko; Maeda, Shigetaka; Sekine, Takashi

JNC TN9400 2004-012, 56 Pages, 2004/03

JNC-TN9400-2004-012.pdf:3.37MB

In the experimental fast reactor JOYO MK-III performance test core, the isothermal temperature coefficient was measured. There was a systematic difference between the result of ascending temperature measuament and that of descending temperature measurement. However, it was removed by the correction of thermal expansion effect of the control rod extension tubes. Finally, -3.82+-0.17x10^-3%dk/kk'/C was obtained as a measured value of the isothermal temperature coefficient. From this result, it was confirmed that isothermal temperature coefficient is a negative value and the calculated design value, -3.88x10^-3%dk/kk'/C, agrees with the measured value well.On the other hand, a detailed analysis based on JUPITER standard analysis method was carried out. In this analysis, transport effects and ultra fine group effects were evaluated. The calculated isothermal temperature coefficient has two main components, Doppler broadening of neutron cross section resonances and thermal expansion of the fuel and core. The items contributing to the thermal expansion include the coolant density reduction, the core radial expansion and the fuel axial expansion. In addition, the isothermal temperature coefficients of the MK-I, MK-II cores were evaluated by using the same method and differences among the cores are discussed. The calculated value by JUPITER standard analysis method became -3.68x10^-3%dk/kk'/C (C/E-value:0.96) and it agrees with the measured value within measurement error.

JAEA Reports

A Study on cell heterogeneity effects in the MONJU core; Evaluation using the continuous energy Monte Carlo code MVP

Morohashi, Yuko; Ishibashi, Junichi;

JNC TN4400 2001-003, 28 Pages, 2002/03

JNC-TN4400-2001-003.pdf:1.12MB

The criticality analysis of the MONJU initial critical core was conducted based on conventional methods developed by the JUPITER program. Effective cross sections were created, considering self-shielding effects, from the JAERI Fast Set (JFS-3-J3.2); group constants in 70 energy groups, which were processed from the Japanese Evaluated Nuclear Data Library (JENDL-3.2). These were used in the standard calculation method: a 3-Dimensional Hexagonal-Z whole core calculation by diffusion theory. This standard calculation, however, involves several approximations. The continuous neutron energy spectrum is divided into 70 discrete energy groups and continuous spatial coordinates are represented by assembly-wise spatial meshes. Original transport equations are solved by diffusion theory (isotropic scattering) approximation and fine structures in fuel assemblies, such as fuel pins or wrapper tubes, are processed into cell-wise homogeneous mixture. To improve the accuracy of the results, these approximations are compensated for by applying corresponding correction factors. Cell heterogeneity effects, among them, were evaluated to be 0.3-0.4%$$Delta$$ k/kk' by diffusion calculations based on the group constants, obtained by heterogeneous cell model calculations. This method, however, has the drawback that it assumes that there is no interdependency of the related approximations; energy grouping, diffusion approximation, etc. A study on cell heterogeneity effects has been conducted using the continuous energy Monte Carlo method to validate the adequacy of this non-interdependency assumption. As a result, cell heterogeneity effects slightly larger than those from conventional methods have been obtained; 0.54% $$Delta$$ k/kk' for the initial critical core, and 0.50% $$Delta$$ k/kk' for the initial full power core. Dependency on plutonium enrichment and fuel temperature has also been identified, which implies the dependency of the cell heterogeneity effects on the specific ...

Oral presentation

Analyses of Monju core by European reactor analysis system "ERANOS"

Usami, Shin; Kageyama, Takeshi*; Morohashi, Yuko; Kitano, Akihiro; Kishimoto, Yasufumi*; Teruyama, Hidehiko; Nishi, Hiroshi

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Prototype FBR Monju system start up test "zero power reactor physics test", 6; Isothermal temperature coefficient measurement

Mori, Tetsuya; Morohashi, Yuko; Maruyama, Shuhei; Kasahara, Hideyuki; Yabuki, Kentaro; Okawachi, Yasushi

no journal, , 

no abstracts in English

Oral presentation

Prototype FBR Monju system start up test "zero power reactor physics test", 7; Coolant flow coefficient measurement

Morohashi, Yuko; Mori, Tetsuya; Maruyama, Shuhei; Kasahara, Hideyuki; Yabuki, Kentaro; Okawachi, Yasushi

no journal, , 

no abstracts in English

Oral presentation

Prototype FBR Monju system start-up test

Morohashi, Yuko

no journal, , 

no abstracts in English

Oral presentation

Monju core confirmation test, 7; Coolant flow coefficient measurement

Morohashi, Yuko

no journal, , 

no abstracts in English

Oral presentation

Results of Monju zero power reactor physics test

Mori, Tetsuya; Takano, Kazuya; Kitano, Akihiro; Morohashi, Yuko; Kato, Yuko; Yabuki, Kentaro; Miyagawa, Takayuki; Okawachi, Yasushi; Hazama, Taira

no journal, , 

Monju restarted safely on May 6, 2010 after 14 years and 5 months suspension. Core Confirmation Test was performed until July 22. The core fuel contains Am-241 because Pu-241 (half-life 14 years) decayed during 14.4 years suspension. Therefore, physics data of the core containing Am-241 are obtained. The mainly test items are criticality, control rod worth and isothermal temperature coefficient. In the criticality, the measured CR position at the criticality was confirmed to be within the predicted CR position range. Criticality was predicted in good accuracy. In the control rod worth measurement, CR worth of CCR1 was measured by the period method. CR worth of other CR was measured by the balancing method. In the isothermal temperature coefficient measurement, the measured value was a little bit smaller than that of the previous test due to the accumulation of Am-241, the decay of Pu-241, and other composition change by refuelling.

Oral presentation

Study on high sensitive FFDL technique for Monju and next generation SFR using laser resonance ionization mass spectrometry

Aoyama, Takafumi; Ishikawa, Takashi; Iwata, Yoshihiro; Ito, Chikara; Morohashi, Yuko; Takeda, Toshikazu*

no journal, , 

no abstracts in English

Oral presentation

High sensitive and reliable FFDL technique for sodium cooled fast reactor using laser resonance mass spectrometry

Aoyama, Takafumi; Takeda, Toshikazu*; Ishikawa, Takashi; Iwata, Yoshihiro; Ito, Chikara; Morohashi, Yuko

no journal, , 

The high sensitivity FFDL technique for SFR has been developed using the RIMS method. The RIMS method was demonstrated by measuring the artificially blended xenon and krypton gas which was used for the pressurized steel capsule of in-pile creep rupture experiment in the experimental fast reactor Joyo. The measured isotopic ratio of xenon collected from the Joyo reactor cover gas by means of RIMS could successfully identify the ruptured capsule of which tag gas was contained. The RIMS was then applied for the proto type fast breeder reactor Monju. The RIMS system can also detect stable xenon nuclides and radioactive Xe-133 in the collected from the Joyo reactor cover gas during the fuel failure simulation test, implying that the RIMS can apply to assume the burn-up of the failed fuel subassembly by using the ratio of stable and radioactive xenon isotopes.

Oral presentation

Performance confirmation of MONJU failed fuel detection and location system, 1; Noble gas concentration test of active carbon

Suzuki, Satoshi; Morohashi, Yuko

no journal, , 

The Tagging gas method which identifies failed fuel by tag gas is used for the failed fuel detection and location system (FFDL) of prototype fast-breeder reactor Monju. This encloses characteristic tag gas (Kr, Xe) with the fuel pin for every fuel assembly beforehand, collects and analyzes the tag gas emitted to the primary argon gas system at the time of fuel failure, and identifies failed fuel. It is supposed on the design that it can identify at a 200 or more-time rare gas concentration rate (recovery rate), and it is checked by sample gas with a rare gas concentration of 1 ppm in the past examination. This time, while checking the rare gas concentration rate by the low concentration gas of the level assumed at the time of fuel failure, it checked also about the dependence of rare gas concentration.

29 (Records 1-20 displayed on this page)