Experience and technology consolidation related to dismantling sodium equipment; Technology to reduce sodium remaining in 100m grade large tanks

Hayakawa, Masato; Shimoyama, Kazuhito; Miyakoshi, Hiroyuki; Suzuki, Shigeaki*

JAEA-Technology 2021-027, 33 Pages, 2022/01

JAEA-Technology-2021-027.pdf:3.64MB

At the Oarai Research and Development Institute of the Japan Atomic Energy Agency, experimental studies in various sodium environments are being conducted in connection with the research and development of sodium-cooled fast reactors such as the experimental fast reactor Joyo and the prototype fast reactor Monju. The dismantling of sodium test facilities and equipment that have achieved their purpose has been carried out sequentially, and a wealth of experience and technology has been accumulated. On the other hand, a large amount of metallic sodium used for research and testing is being reused for new testing facilities, and the large sodium tanks that contained the metallic sodium are being dismantled. In order to dismantle these tanks safely and efficiently, it is important to reduce the residual sodium inside the tanks (especially at the bottom) as much as possible before dismantling. Therefore, we have been working on the reduction of residual sodium at the bottom of several large sodium tanks of 100 m class. This report describes the technologies and experiences related to the reduction of residual sodium that have been carried out so far.

Development of sodium conversion technology; Method and basic features of sodium conversion process

Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*

JAEA-Research 2007-038, 32 Pages, 2007/03

JAEA-Research-2007-038.pdf:5.06MB

Decommissioning of a sodium cooled fast reactor or an experimental facility which used radioactive sodium will bring a lot of radioactive sodium. However, technology to deal with such the radioactive sodium and decommission is not well established in Japan. Then, basic experimental study has been carried out in order to find and estimate an economic and safety process of the radioactive sodium decommission. There were some examples in overseas to convert the sodium into sodium hydroxide via sodium-water reaction. This method was examined by a basic sodium conversion test apparatus. In the experiment, liquid metal sodium was injected into the sodium hydroxide. Influences of temperature and concentration of the sodium hydroxide were investigated. Nitrogen gas was injected into the sodium hydroxide as atomizing gas in order to protect the sodium injection nozzle and also to mix the sodium. Then the gas flow rate was also varied to see the desired effects. Injected sodium temperature and mass flow rate were fixed at 200C and 10kg/h, respectively. The atomizing gas flow rate, the temperature and concentration of the sodium hydroxide were varied in ranges of 60-100 l/min, 70-100C and 40-60wt%, respectively. The influences of these parameters on the sodium conversion reaction were evaluated. The experiments showed that increase of the atomizing gas resulted in stable injection of the sodium and also larger reaction area. The temperature of the sodium hydroxide had small influences on the reaction, however, the sodium injection nozzle tended to choke up when the temperature was less than 70C. The lower concentration resulted in larger temperature fluctuation and also enlarged the reaction area. Unstable reaction, for example, sudden increase of reaction rate due to excess sodium, was not found under the conditions above listed ranges and stable sodium conversion was confirmed.

Reference Core Design Mark-III of the Experimental Multi-Purpose VHTR; Study of Nuclear and Thermohydraulic Characteristics for Design of main Core Parameters

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JAERI-M 8546, 107 Pages, 1979/11

JAERI-M-8546.pdf:2.5MB

no abstracts in English

Design Study of Block-Pin Type Fuel for Experimental VHTR (EVHTR) Core

; ; ; *; *; *; *

JAERI-M 6714, 39 Pages, 1976/09

JAERI-M-6714.pdf:1.2MB

no abstracts in English

Dismantling technology for large-scale sodium components used for a long time, 1; Behavior of impurity adhesion to sodium equipment

Shimoyama, Kazuhito; Hayakawa, Masato; Suzuki, Shigeaki*; Miyakoshi, Hiroyuki; Ara, Kuniaki

no journal, , 

We are conducting dismantling inspection of large-scale sodium component that we have been using in sodium environment for a long time. It was found from the operation history etc. that the sodium compound adhesion behavior on the inner surface of each device exposed to the sodium environment for several decades from the start of use affects sodium purity. In dismantling large sodium equipment, it is important to reduce the residual sodium in the equipment as much as possible, and proposing to carry out high temperature refining operation effective for removal of these attached impurities at the end of plant operation.

Dismantling technology for large-scale sodium components used for a long time, 2; Adhesion behavior of sodium vapor in cover gas region

Suzuki, Shigeaki*; Hayakawa, Masato; Shimoyama, Kazuhito; Umeda, Ryota; Yoshida, Eiichi; Miyakoshi, Hiroyuki

no journal, , 

We are conducting dismantling inspection of large-scale sodium component that we have been using in sodium environment for a long time. We got the cover gas area sodium deposition rate of the large tank used for several decades. As a result of examination based on the data and past findings, it was possible to derive the recommended value "1.0e-10 g/cm/s" for the cover gas region sodium adhesion rate of the plant operating in the low temperature range (150 to 200C). For disassembling large sodium equipment, it is possible to estimate and evaluate sodium adhesion amount based on this recommended value and operation history. With this evaluation, it became possible to increase the reliability of disassembly technology for safety measures and safety management related to sodium fires etc.