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Sakashita, Satoshi; Okui, Masahiro; Yoshida, Tadayoshi; Uezu, Yasuhiro; Okuda, Eiichi
JAEA-Review 2022-012, 42 Pages, 2022/06
JAEA-Review-2022-012.pdf:2.96MB
In this report, results of investigating fire alarm detectors status in order to understand the actual situation of false alarm occurrence and measures to systematically update of them. Based on results of this investigation, measures to systematically update of detectors were taken in order to reduce false fire alarm reports in a harsh environment and aged detectors. Numbers of detectors, false alarms were investigated. Furthermore, causes of their occurrence were investigated for three years (2018-2020). As a result of this investigation, it was found that most of the 34,400 fire alarm detectors in JAEA have been used for more than 20 years. In the last 3 years, 65 false alarms have been reported, 60% of which were found to have been used where the environment should be improved. It was also found that there are many cases where false alarms are reported from a detector within 14 years after installation. Based on the above, three basic policies were formulated. First of all, database will be built for fire alarm maintenance and inspection, secondly, installation location of fire alarm will be improved, and finally, detectors will be updated with reference to the manufacture's plan. According to the three basic policies, it is considered that the reports of false fire alarms will be able to reduced.
Sono, Hiroki; Sukegawa, Kazuhiro; Nomura, Norio; Okuda, Eiichi; Study Team on Safety and Maintenance; Study Team on Quality Management; Task Force on New Nuclear Regulatory Inspection Systems
JAEA-Technology 2020-013, 460 Pages, 2020/11
JAEA-Technology-2020-013.pdf:13.46MB
Japan Atomic Energy Agency (JAEA) has completed the introduction of a new frame work of safety, maintenance and quality management activities under the new acts on the Regulation of nuclear source material, nuclear fuel material and reactors since April 2020, in consideration of variety, specialty and similarity of nuclear facilities of JAEA (Power reactor in the research and development stage, Reprocessing facility, Fabrication facility, Waste treatment facility, Waste burial facility, Research reactor and Nuclear fuel material usage facility). The JAEA task forces on new nuclear regulatory inspection systems prepared new guidelines on (1) Safety and maintenance, (2) Independent inspection, (3) Welding inspection, (4) Free-access response, (5) Performance indicators and (6) Corrective action program for the JAEA's nuclear facilities. New Quality management systems and new Safety regulations were also prepared as a typical pattern of these facilities. JAEA will steadily improve these guidelines, quality management systems and safety regulations, reviewing the official activities under the new regulatory inspection system together with the Nuclear Regulation Authority and other nuclear operators.
Harigae, Hitoshi; Takagi, Tsuyohiko; Hamano, Tomoharu; Nakamura, Shoichi; Oba, Toshio; Ebashi, Masaaki; Okuda, Eiichi; Kinoshita, Tomonobu
JAEA-Technology 2013-014, 150 Pages, 2013/07
JAEA-Technology-2013-014.pdf:24.38MB
In-Vessel Transfer Machine (IVTM) came off from the gripper claw in the Auxiliary Handling Machine (AHM) and fell at a height of approximately two meters during a withdrawal work of the IVTM in the Fast Breeder Reactor (FBR) Monju. The withdrawal work of IVTM from the reactor vessel by AHM was performed. The work, however, was suspended due to the excessive load alarm. To grasp the situation of the IVTM fall, observation of the machine was necessary. An interior observation and an exterior observation of the dropped IVTM were performed. As a result of these observations, the radially deformed lower end of the upper guide tube was observed at the connection part, and it was jammed in the fuel throat sleeve when the dropped IVTM was withdrawn. Based on this information, the IVTM could be safely withdrawn from the reactor vessel with the fuel throat sleeve.
Kato, Yuko; Umebayashi, Eiji; Okimoto, Yutaka; Okuda, Eiichi; Takayama, Koichi; Ozawa, Takayuki; Maeda, Seiichiro; Matsuzaki, Masaaki; Yoshida, Eiichi; Maeda, Koji; et al.
JAEA-Research 2007-019, 56 Pages, 2007/03
JAEA-Research-2007-019.pdf:6.79MB
In order to resume the System Startup Test (SST) of Monju, replacement fuel have to be loaded in exchange for some of initial fuel now loaded in the core to compensate core reactivity lost by decay of Pu-241 in them. The replacement fuel were being stored either in sodium in an ex-vessel storage tank or in air in a storage rack for about 10 years since their fabrication. The initial fuel were irradiated during the SST which was suspended in the end of 1995 and then stayed being loaded in the sodium-circulated core. As this long-term storage and loading may deteriorate mechanical integrity of the assemblies, a study has been made thoroughly on its thermal-hydraulic, structural and material effects on them that might be caused by irradiation in the core, sodium and mechanical environment. The study has shown that the mechanical integrity of them is well maintained even with this long-term storage and loading.
; ; Ueno, Fumiyoshi; ; ; ;
JNC TN2400 2000-005, 103 Pages, 2000/12
JNC-TN2400-2000-005.pdf:3.98MB
Inelastic analyses of the floor liner subjected to thermal loading due to sodium leakage and combustion were carried out, considering thinning of the liner plate due to molten salt type corrosion. Because the inelastic strain obtained by the analyses stayed below the ductility limit of the material, mechanical integrity, i.e., there exist no through-wall crack on the floor liner, was confirmed. Partial structural model tests were conducted, with a band of local thinning of the liner plate. Displacements were controlled to give specimens much larger strains than those obtained by the inelastic analyses above. No through-wall crack was observed by these tests. Mechanical integrity of the floor liner was confirmed by these results of the inelastic analyses and the partial structural model tests.
; ; ; ; ; Kano, Shigeki
PNC TN9410 94-351, 97 Pages, 1994/09
Subsequent to the previuos testing (PNC SN9410 90-082, June 1990), characterization has been made on the sintered-metal load gauge element. The sintered-metal load gauge element was developed for use in off-line load measurement in the reactor environment. The testing conducted is as follows : (1)Characterization test phase II (a)Compression Tests for Initial Adjustment (b)Geometrical Parameter Compression Tests (c)Inclined Compression Tests (d)Creep Tests at Elevated Temperature (2)Characterization test phase III (For application in the reactor environment, the sintered-metal was covered with thin plates.) (a)Compression Tests for Initial Adjustment (b)Compression Tests at Elevated Temperatures (c)Inclined Compression Tests at Elevated Temperatures The results have shown that the sintered-metal load gauge element is applicable in the reactor environment. In association with the characterization tests, method for practical applications in JOYO and extended application have also been investigated.
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PNC TN9410 90-082, 105 Pages, 1990/06
Characterization has been made on the sintered-metal load gauge element which is under development for use in off-line load measurement in the reactor environment. The shape of the element was determined with due consideration for possible use in the sub-assembly interaction force measurement in the Joyo core. The testing conducted is as follows : (1)Themal Expansion Measurement Test (2)Sodium l㎜ersion Test (3)Compression Tests at Room Temperature (4)Compression Tests at Elevated Temperatures (5)Creep Tests at Elevated Temperature Compression tests for sodium-i㎜ersed elements were also comducted at an elevated temperature. Characteristic data obtained have been highly satisfactory, thereby encouraging further study for practical applications.
; *; *; *; *; *
PNC TN9410 89-052, 54 Pages, 1989/03
Control rod operation guidance system (named Rod Guider) has been developed for the development of the automatic control rod system in experimental reactor Joyo from 1986. The first step of this development was completed. The four sphere's programs (Critical approach, Power ascent, Power adjustment, Power descent) had already been completed and the system heat-up program, remained last sphere's program, was developed continuously. And, Menu program was completed in order to unite five sphere's programs. During the 16th 100 MW duty cycle operation of Joyo, all programs (five sphere's program) were verified. Rod Guider gave adequate guidances for the operators. The results of these developments are following. (1)The program of system heat-up had a very good control. (2)New functions that give various plant operating guidances to the operators, excepting control rod operating guidance, were good. (3)All sphere's programs had a good contact to the menu program. (4)All sphere's programs (Critical approach, System heat-up, Power ascent, Power adjustment, Power descent) were completed.
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Final Report of the CRP on Intercomparison of LMFBR Core MEchanics Codes, 0 Pages, 1989/00
no abstracts in English
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PNC TN9410 86-112, 91 Pages, 1986/10
Since the initial criticality of Joyo was achieved in 1977, the reactor has been operated thoroughly and the reactor protection system which consists of control rods, acontrol rod drive system, monitoring instrumentations and logic modules has been functioned as designed. As the time elapsed, the maintenance work was gradually expanded due to degradation of the system. A modification of the logic module was conducted to increase its reliability. This paper describes the modification and its results of the logic module which was conducted during 5th periodical inspection. The logic module is essential for the reactor protection function, and provides scram signals on determing conditions. Reliability of the module is strongly required and function check of the module is also required on the reactor operation, for assurance of plant safety. The results of the modification are summerized as follows, (1)The solid-state integrated circuits used in the logic module as the basic logic switching scheme was modified from type "HTL" into type "C-MOS" which is excellent noise proof device. And further faile-safe design was completely applied in both logic circuits and out-put mechanical relay circuits. (2)Reflecting the experience obtained through the operation, the operational board and circuits were modified in order to improve operability of the system. New functions were introduced as indication of first actuated signal and self-testing circuits which enable to check regardless the operation conditions. Further step-wise checking was also introduced to diagnose integrity of individual signal train. (3)In order to increase maintenability, defect indication was newly provided, which displays circuit defect if any, and circuit boards were modified to access easily for checking.
*; *; *; *; Miyaguchi, Kimihide; *
PNC TN941 84-121, 56 Pages, 1984/08
At the Delayed Monitoring system, which in one of the Fuel Failure Detection System in JOYO, some probrems had occurred since the 6th cycle of 75MW power operation at MK-I core. As a result of inspection from Feb. 1983 to Mar. 1984, it was found that the various electrical noises interface with it's normal function. So many kinds of noise appeared at power supply circuit, pre-amplifier circuit and cable lines. Though this Phenomenon was a difficult problem to deal with, We could remove injurious electrical noises successfully. lt's working effects were indicated as follows, (1)At first an AC Line Conditioner was built in power supply circuit. (2)An adjustment was made on the pre-amplifier circuit and some circuit parts were replaced in order to alter the circuit. (3)Most of signal line at BF-3 monitoring system was changed from coaxial cable to glass fiber cable partially.
Ito, Kazumoto; Ikeda, Hiroshi; Takayama, Koichi; Okuda, Eiichi
no journal, ,
no abstracts in English