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Journal Articles

Sound speeds in and mechanical properties of (U,Pu)O$$_{2-x}$$

Hiroka, Shun; Kato, Masato

Journal of Nuclear Science and Technology, 55(3), p.356 - 362, 2018/03

 Times Cited Count:2 Percentile:33.17(Nuclear Science & Technology)

The sound speeds of longitudinal and transverse waves in the uranium-plutonium mixed oxide (MOX) pellets were measured as functions of porosity, oxygen-to-metal ratio (O/M) and plutonium content. The effect of each parameter was well fitted by a linear function and the equations were obtained to calculate the sound speeds. Mechanical properties were evaluated with the sound speeds and the result of Young's modulus showed that porosity was the most important factor to decrease Young's modulus. Temperature dependence on Young's modulus was also evaluated with previously reported thermal expansion. Decrease of Young's modules with increasing temperature was in good agreement with available literature.

Journal Articles

Influence of temperature histories during reactor startup periods on microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons

Kasahara, Shigeki; Kitsunai, Yuji*; Chimi, Yasuhiro; Chatani, Kazuhiro*; Koshiishi, Masato*; Nishiyama, Yutaka

Journal of Nuclear Materials, 480, p.386 - 392, 2016/11

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

This paper addresses influence of two different temperature profiles during startup periods in the Japan Materials Testing Reactor and a boiling water reactor upon microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons to about 1 dpa and 3 dpa. Tensile tests at 290$$^{circ}$$C and Vickers hardness tests at room temperature were carried out, and their microstructures were observed by FEG-TEM. Influence of difference in the temperature profiles was observed obviously in interstitial cluster formation, in particular, growth of Frank loops. The influence was also found certainly in loss of strain hardening capacity and ductility, although the influence on the yield strength and the Vickers hardness was not clearly observed. As a result, Frank loops, which were observed in austenitic stainless steel irradiated at doses of 1 dpa or more, were considered to contribute to deformation of the austenitic stainless steel.

JAEA Reports

An Irradiation test of heat-resistant ceramic composite materials, 2; Interim report on post-irradiation examinations of the second and third preliminary test, 98M-41A, 99M-30A

Baba, Shinichi; Nemoto, Makoto*; Sozawa, Shizuo; Yamaji, Masatoshi*; Ishihara, Masahiro; Sawa, Kazuhiro

JAERI-Tech 2005-055, 157 Pages, 2005/09

JAERI-Tech-2005-055.pdf:19.06MB

The Japan Atomic Energy Research Institute (JAERI) has been carrying out the research on radiation damage mechanism of heat-resistant ceramics composite materials, as one of the subjects of the innovative basic research on high temperature engineering using the High Temperature Engineering Test Reactor (HTTR). A series of preliminary irradiation tests is being made using the Japan Materials Testing Reactor (JMTR). The present report describes results of post-irradiation examinations so far on specimens irradiated in the second and third capsule, designated 98M-41A and 99M-30A, to fast neutron fluences of 1.0$$times$$10$$^{25}$$m$$^{-2}$$(E$$>$$1MeV) at temperatures of 973K-1173K and 1273K-1473K. The PIE were conducted as the fundamental statistics index of the diametral dimensions for irradiated specimen, irradiation induced dimensional change rate and thermal expansion rate.

Journal Articles

Effects of irradiation and water temperatures on IASCC susceptibility of stainless steels

Miwa, Yukio; Tsukada, Takashi

Proceedings of 8th Japan-China Symposium on Materials for Advanced Energy Systems and Fission & Fusion Engineering, p.161 - 168, 2004/10

Irradiation assisted stress corrosion cracking (IASCC) is one of the environmental degradation problems of in-core structural materials for light water reactors. The effects of irradiation and water temperatures on the IASCC were studied using type 316(LN) stainless steels irradiated at 333-673 K to 1.1-16 dpa. IASCC did not occur at 513 K in oxygenated water for specimens irradiated below 573 K to 1.1-16 dpa, but IASCC occurred above 533 K in oxygenated water for all specimens. The irradiation temperature had a strong influence on IASCC susceptibility at 513 K in oxygenated water, so that the irradiation temperature dependence was compared with the temperature dependence of other radiation-induced phenomena.

JAEA Reports

Preliminary investigation of annealing effect on thermal conductivity of graphite and investigation of annealing test method (Contract research)

Sumita, Junya; Nakano, Masaaki*; Tsuji, Nobumasa*; Shibata, Taiju; Ishihara, Masahiro

JAERI-Tech 2004-055, 25 Pages, 2004/08

JAERI-Tech-2004-055.pdf:4.25MB

Neutron irradiation remarkably reduces the thermal conductivity of graphite, and the reduced thermal conductivity is recovered by annealing effect if the graphite is heated above the irradiation temperature. Therefore, it is expected that the reduced thermal conductivity of graphite components in the HTGR could be recovered by the annealing effect in accidents, such as a depressurization accident. Then, an analytical investigation of the annealing effect on thermal performance of a HTGR core was carried. The analysis showed that the annealing effect reduces the maximum fuel temperature about 70$$^{circ}$$C, and it is important to introduce the annealing effect appropriately in the temperature analysis of the core components and reactor internals. In addition, an annealing test method was investigated to evaluate the effect quantitatively, and the test plan was made.

Journal Articles

Effects of silicon, carbon and molybdenum additions on IASCC of neutron irradiated austenitic stainless steels

Nakano, Junichi; Miwa, Yukio; Koya, Toshio; Tsukada, Takashi

Journal of Nuclear Materials, 329-333(Part1), p.643 - 647, 2004/08

 Times Cited Count:7 Percentile:46.83(Materials Science, Multidisciplinary)

To study effects of minor elements on the irradiation assisted stress corrosion cracking (IASCC), high purity Type 304 and 316 stainless steels (SSs) were fabricated and added minor elements, Si or C. After neutron irradiation to 3.5$$times$$10$$^{25}$$n/m$$^{2}$$ (E$$>$$1MeV), the slow strain rate tests (SSRT) for the irradiated specimens was conducted in oxygeneted high purity water at 561 K. Fracture surface of the specimens was examined using the scanning electron microscope (SEM) after the SSRT. Fraction of intergranular stress corrosion cracking (IGSCC) on the fracture surface after the SSRT increased with netron fluence. Suppression of irradiation hardening and increase of peiod to SCC fracture as benefitical effects of the additional elements, Si or Mo, were not observed obviously. In high purity SS added C, fraction of IGSCC was the smallest in the all SSs, although irraidiation hardening level was the largest in the all SSs. Addition of C suppressed the susceptibility to IGSCC.

Journal Articles

Correlation between cleavage fracture toughness and charpy impact properties in the transition temperature range of reactor pressure vessel steels

Onizawa, Kunio; Suzuki, Masahide

JSME International Journal, Series A, 47(3), p.479 - 485, 2004/07

In the structural integrity assessment of reactor pressure vessel, fracture toughness values are estimated by assuming that the radiation effect on fracture toughness is equivalent to that on Charpy properties. Therefore, it is necessary to establish the correlation between both properties especially on irradiation embrittlement. In this paper, we present the fracture toughness data obtained by applying the master curve approach that was adopted recently in the ASTM test method. Materials used in this study are five ASTM A533B class 1 steels and one weld metal. Neutron irradiation for Charpy-size specimens as well as standard Charpy-v specimens was carried out at the Japan Materials Testing Reactor. The shifts of the reference temperature on fracture toughness due to neutron irradiation are evaluated. Correlation between the fracture toughness reference temperature and Charpy transition temperature is established. Based on the correlation, the optimum test temperature for fracture toughness testing and the method to determine a lower bound fracture toughness curve are discussed.

JAEA Reports

Development of pellet melting temperature measuring technique; Melting temperature measuring technique for small sample

Harada, Katsuya; Nakata, Masahito; Harada, Akio; Nihei, Yasuo; Yasuda, Ryo; Nishino, Yasuharu

JAERI-Tech 2004-034, 13 Pages, 2004/03

JAERI-Tech-2004-034.pdf:0.69MB

The Department of Hot Laboratories has been aiming the establishment of the melting temperature measuring technique for small samples obtained from the micro-region of irradiated fuel pellet. Due to the modification of the shape of tungsten capsule contained sample and the improvement of the detection method for melting temperature from indistinct thermal arrest point owing to small sample, it is possible to determine the melting temperature of small sample and to utilize effectively for the irradiated fuel pellet by using the existing apparatus. This paper describes the technique of the melting temperature measurement for small sample and the experimental results by using tantalum, molybdenum, hafnium oxide and un-irradiated UO$$_{2}$$ pellet.

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

Assessment of irradiation temperature stability of the first irradiation testi rig in the HTTR

Shibata, Taiju; Kikuchi, Takayuki; Miyamoto, Satoshi*; Ogura, Kazutomo*

Nuclear Engineering and Design, 223(2), p.133 - 143, 2003/08

 Times Cited Count:1 Percentile:11.39(Nuclear Science & Technology)

The High Temperature Engineering Test Reactor (HTTR) can provide very large spaces at high temperatures for irradiation tests. The I-I type irradiation equipment was developed as the first irradiation rig. It will be served for an in-pile creep test on a stainless steel with large standard size specimens. It uses the ambient high temperature of the core for the irradiation temperature control. The target irradiation temperatures are 550 and 600$$^{circ}$$C with the target temperature deviation of $$pm$$3$$^{circ}$$C. In this study, the irradiation temperature changes at transient conditions were analyzed by an FEM code and the temperature controllability of the equipment was examined by a mockup test. The controllability was evaluated with the measured temperature transient data at the core graphite components in the Rise-to-Power tests of the HTTR. The result indicates that the temperature control method of the equipment is effective to keep the irradiation temperature stable in the irradiation test.

JAEA Reports

Development of capsule design support subprograms for 3-dimensional temperature calculation using FEM code NISA

Tobita, Masahiro*; Matsui, Yoshinori

JAERI-Tech 2003-042, 132 Pages, 2003/03

JAERI-Tech-2003-042.pdf:7.19MB

Prediction of irradiation temperature is one of the important issues in the design of the capsule for irradiation test. Many kinds of capsules with complex structure have been designed for recent irradiation requests, and three-dimensional (3D) temperature calculation becomes inevitable for the evaluation of irradiation temperature. For such 3D calculation, however, many works are usually needed for input data preparation, and a lot of time and resources are necessary for parametric studies in the design. To improve such situation, JAERI introduced 3D-FEM (finite element method) code NISA (Numerically Integrated elements for System Analysis) and developed several subprograms, which enabled to support input preparation works in the capsule design. The 3D temperature calculation of the capsule are able to carried out in much easier way by the help of the subprograms, and specific features in the irradiation tests such as non-uniform gamma heating in the capsule, becomes to be considered.

Journal Articles

Irradiation Assisted Stress Corrosion Cracking (IASCC)

Tsukada, Takashi

Zairyo To Kankyo, 52(2), p.66 - 72, 2003/02

Irradiation assisted stress corrosion cracking (IASCC) is a potential failure mode suffered by the core-components of austenitic stainless steels in the aged light-water reactor (LWR), which is the intergranular type cracking caused by synergistic effects of neutron/gamma radiation and chemical environment. Effects of radiation on the materials and high-temperature water are discussed in this paper to understand IASCC phenomenon from a mechanistic viewpoint. It is essential to elucidate the radiation-induced microcompositional and microstructural changes in the alloy for mechanistic and predictive investigations of IASCC. Although grain boundary segregations of alloying and impurity elements are significant factors affecting IASCC, it has been considered that the radiation-induced microstructural and mechanical changes of materials play critical roles in IASCC. For mechanistic understanding of IASCC, further fundamental research works with experimental and theoretical approaches are needed. Efforts directed to the researches at the Japan Atomic Energy Research Institute are also described.

JAEA Reports

Temperature evaluation of irradiation specimens in the HTTR for innovative basic research

Ishihara, Masahiro; Baba, Shinichi; Takahashi, Tsuneo*; Aihara, Jun; Shibata, Taiju; Hoshiya, Taiji

JAERI-Tech 2002-054, 169 Pages, 2002/07

JAERI-Tech-2002-054.pdf:5.93MB

no abstracts in English

JAEA Reports

Evaluation of dose equivalent rate for IASCC water control unit

Tobita, Masahiro*; Itabashi, Yukio

JAERI-Tech 2002-042, 40 Pages, 2002/03

JAERI-Tech-2002-042.pdf:2.09MB

In relation to aging of light water reactors (LWRs), Irradiation Assisted Stress Corrosion Cracking (IASCC) has been regarded as a significant and urgent issue for reliability of in-core components of LWRs. It is essential for IASCC studies to irradiate test materials under well-controlled of Boiling Water Reactor (BWR) conditions simulating the in-core environment. Therefore, the study for the design of the new water control unit to supply high temperature water into saturated temperature capsules in the Japan Materials Testing Reactor (JMTR) has been carried out. This report summarizes the results of estimation using ORIGEN-2 and QAD-CGGP2 codes of dose equivalent rate on outer surface of the concrete wall of installation room and dose equivalent rate around the ion-exchangers where the highest dose equivalent rate is expected in the unit after the reactor shutdown.

JAEA Reports

Study on high-performance fuel cladding materials; Joint research report in FY 1999-2000 (Phase 1) (Joint research)

Kiuchi, Kiyoshi; Ioka, Ikuo; Tachibana, Katsumi; Suzuki, Tomio; Fukaya, Kiyoshi*; Inohara, Yasuto*; Kambara, Shozo; Kuroda, Yuji*; Miyamoto, Satoshi*; Ogura, Kazutomo*

JAERI-Research 2002-008, 63 Pages, 2002/03

JAERI-Research-2002-008.pdf:7.85MB

no abstracts in English

Journal Articles

New material synthesis by radiation processing at high temperature; Polymer modification with improved irradiation technology

Seguchi, Tadao; Yagi, Toshiaki; Ishikawa, S.*; Sano, Y.*

Radiation Physics and Chemistry, 63(1), p.35 - 40, 2002/01

 Times Cited Count:65 Percentile:96.58(Chemistry, Physical)

no abstracts in English

Journal Articles

Development of 3-dimensional capsule temperature calculation program using FEM (NISA Code)

Tobita, Masahiro*; Matsui, Yoshinori

KAERI/GP-195/2002, p.87 - 95, 2002/00

In the Japan Materials Testing Reactor (JMTR) of Japan Atomic Energy Research Institute (JAERI), the temperature distribution inside of irradiation specimens and capsules structure material are evaluated in the design of irradiation capsules. For the evaluation of detailed temperature distribution, NISA (Numerically Integrated elements for System Analysis) code has been introduced, and subprograms are developed to simplify the input data of the capsules structure and the analysis conditions using the three-dimensional finite element method. By the development of subprograms, prediction of the temperature distribution inside of irradiation specimens and capsules structure material became detailed and more accurate than calculation by one-dimensional code. Also estimation of detail temperature distribution during irradiation became possible based on the indication of thermocouple.

Journal Articles

Development of new technique for temperature control of irradioation capsules

Kanno, Masaru; Kitajima, Toshio; Homma, Kenzo

KAERI/GP-195/2002, p.71 - 75, 2002/00

Recent irradiation studies aiming at clarifying the detailed mechanisms of irradiation damages to the reactor materials require to maintain the specimens at constant temperature regardless of the reactor power level,in order to avoid artificial effects of temperature transient due to reactor power change. In order to deal with this problem, JMTR has adopted feed-foward control to the gas pressure based on the reactor power signal, and developed new temperature control technique in combination with feedback control of heater power.

Journal Articles

New in-pile water loop facility for IASCC studies at JMTR

Tsukada, Takashi; Komori, Yoshihiro; Tsuji, Hirokazu; Nakajima, Hajime; Ito, Haruhiko

Proceedings of International Conference on Water Chemistry in Nuclear Reactor Systems 2002 (CD-ROM), 5 Pages, 2002/00

Irradiation assisted stress corrosion cracking (IASCC) is caused by the synergistic effects of neutron and gamma radiation, residual and applied stresses and high temperature water environment on the structural materials of vessel internals. IASCC has been studied since the beginning of the 1980s and the phenomenological knowledge on IASCC is accrued extensively. However, mainly due to the experimental difficulties, data for the mechanistic understanding and prediction of failures of the specific in-vessel components are still insufficient and further well-controlled experiments are needed [1]. In recent years, efforts to perform the in-pile materials test for IASCC study have been made at some research reactors [2-4]. At JAERI, a high temperature water loop facility was designed to install at the Japan Materials Testing Reactor (JMTR) to carry out the in-core IASCC testing. This report describes an overview of design and specification of the loop facility.

JAEA Reports

Results and future plans for the innovative basic research on high temperature engineering

HTTR Utilization Research Committee

JAERI-Review 2001-016, 232 Pages, 2001/05

JAERI-Review-2001-016.pdf:12.01MB

no abstracts in English

70 (Records 1-20 displayed on this page)