Radiation control on wastes recovery work in wastes storage pit

Ito, Yasuhisa; Noda, Kimio; ;

JNC TN8410 2001-018, 67 Pages, 2001/04

JNC-TN8410-2001-018.pdf:2.96MB

There are waste storage pits where non-radioactive wastes generated from plutonium fuel facilities were stored in JNC Tokai Works. But radioactive wastes were found in one of the pit during wastes arrangement works. Therefore we set the pit temporary controlled area and recovered wastes from it. This report describes the radiation control technique of recovery work in detail.

Development of resistance welding process; Manufacture of test specimens for ODS steel strength evaluation

Endo, Hideo; Seki, Masayuki; ; *; *

JNC TN8410 2000-007, 89 Pages, 2000/03

JNC-TN8410-2000-007.pdf:6.28MB

(1)Outline of examination. Various test specimens were made to evaluate and confirm the weld strength properties of the oxide dispersion strengthened (ODS) cladding tube material (martensitic and ferritic steel), which had been manufactured in JFY 1997. The examination consisted of tensile tests (RT,650C, 700C, 800C), internal pressure creep tests, internal pressure burst tests, and a rapid heating burst tests. (2)Examination results. The results of the tensile tests are as follows: (ferritic and martensitic) (a)All test specimens from RT to 700C failed in the tube. The weld zones had not failed. (b)The test specimens at 800C failed in the weld zones. There was little elongation. (ferritic) (a)The weld zone had fine grain structure and carbide precipitates. (martensitic) (a)Carbide had precipitated in the weld zone. From these results, the strength of weld zone decreased extremely at temperatures exceeding the endurance limit (700C) All of the internal pressure burst test specimens and the rapid heating burst test specimens failed in the tube and not the weld zone. (3)The quality assurance method of the test specimens. The weld reliability of the test specimens were confirmed by the process control of the welding conditions, by using control test specimens, and ultrasonic testing. Confirmation of the process control of the welding conditions; current wave, the voltage waveform, the accelerogram, and the displacement ripple in the welding process was recorded to assure an abnormal value had not occurred. (Process control of welding condition) The results the current waveform, voltage waveform, accelerogram, and the displacement waveform were excellent. (test specimens) The weld joint was excellent based on metallography examination. (Ultrasonic testing) The length of the weld joint was measured and found to be adequate. The reliability the weld joint can be assured by using the above-mentioned method.

Introduction to Reactor Safety

;

Genshiryoku Kogyo, 20(4), p.46 - 52, 1974/04

http://ci.nii.ac.jp/naid/40017723321

no abstracts in English

Development of elemental technology for alpha-ray dust monitor for in-situ measurement of radioactive aerosol in dismantling and decommissioning

Tsubota, Yoichi; Honda, Fumiya; Nakagawa, Takahiro; Kawasaki, Takashi; Tamakuma, Yuki*; Tokonami, Shinji*; Momose, Takumaro

no journal, , 

A large number of radioactive aerosols, especially alpha particles, are expected to be generated during fuel debris retrieval on Fukushima - Daiichi (1F) site and decommissioning of nuclear fuel cycle facilities. In the case of conventional alpha dust monitor, silicon surface barrier detector (SSBD) is often used as a detector which has not so high limit of count rates. Moreover, SSBD is not suitable for high humidity environment. In this work, we developed a prototype of alpha dust monitor aiming at an in-situ measurement of high concentration of airborne alpha particles. Approx. 20M cpm of counting rate was achieved which was more than 10 times higher compared to a conventional alpha dust monitor using SSBD. For follow-up test, counting rate of prototype alpha dust monitor was smoothly followed with respect to the airborne concentration of alpha particles.

Identification of artificial radionuclides in radioactive aerosol monitor

Hashimoto, Hiroki*; Yamada, Ryohei; Yamaguchi, Kanna*; Sasaki, Koichi*; Tamakuma, Yuki*; Hosoda, Masahiro*; Akata, Naofumi*; Tokonami, Shinji*

no journal, , 

no abstracts in English

Discrimination of artificial radionuclides in a radioactive aerosol monitor; Correlation method of Po-gross alpha counts

Yamada, Ryohei; Hashimoto, Hiroki*; Tamakuma, Yuki*; Omori, Yasutaka*; Hosoda, Masahiro*; Akata, Naofumi*; Uchiyama, Rei; Nakada, Akira; Endo, Michitaka*; Imajo, Yusuke*; et al.

no journal, , 

no abstracts in English

Effective dealing with aging alpha dust monitors

Imahashi, Atsushi; Sagawa, Naoki; Kanazawa, Nobuyuki*; Tamura, Toshinobu*; Hosomi, Kenji; Takashima, Hideki

no journal, , 

Alpha dust monitors are used for continuous measurering of airborne alpha contamination in radiation control area in NCL JAEA. In case of emergency, alarm is issued to evacuate workers. However, number of false alarms due to degradation of equipment are increasing year by year, because the equipment has been used more than 30 years. Now, we are updating our old silicon detectors to new ion-implanted silicon detectors with high endurance. We are also installing new preamplifier cercuits which is strong against electrical noise. As a result, reliability of alpha dust monitors has been ensured. In this talk, a report about our effective deal with the aging equipment will be given.