Plutonium nitrate solution is stored in tanks that have cooling system to prevent boiling accident by decay heat and scavenging system to prevent explosion of hydrogen generated by radiolysis. These systems are designed to be provided power from emergency power generators at the Tokai reprocessing plant (TRP) when commercial power is lost. In addition, some apparatus (mobile power generators and nitrogen gas cylinder to scavenge hydrogen, etc.) are recently deployed at TRP on the basis of power loss i...
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Emergency safety measures at the Tokai reprocessing plant（Part 2）

In the Fukushima Daiichi Nuclear Power Plant unit 1, isolation condenser (IC) should play an important role in core cooling during the station blackout. To evaluate cooling capacity of the IC, two phase flow analyses with the TRAC-BF1 code and experiments simulating the IC were conducted. The analyses for the actual BWR indicated that the decay heat could be removed if the IC worked properly at 18:18. However, our results showed that core uncovery occurred at 17:30, which leaded to hydrogen production f...
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Study on Evaluation of Cooling Capacity of Isolation Condenser in Fukushima Daiichi Unit 1

The water level in the fuel zone is an important parameter to conduct properly accident management. In the Fukushima Daiichi Nuclear Power Plant accident, measurement error of the water level occurred, which was caused by evaporation of water in a reference leg. To measure the water level properly, the reference leg connected to the condensing chamber must be filled with water. We focused on the method called backfill to keep the performance of water level gauge during severe accident. Backfill is applied ...
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Study on keeping performance of water level gauge under the severe accident.

Ultrasonic testing techniques by using the three-dimensional (3D) phased array was investigated. The 3D phased array allows a target region to be scanned volumetrically with focused beams transmitted from a matrix array probe. This leads to an increase in inspection speed and easy-to-u nderstand inspection results displayed as 3D rendered images. This paper focuses mainly on synthesizing techniques of 3D scanned data obtained a t multiple positions when moving the probe. The technique is effective to figu...
英字タイトル:
Three-Dimensional Phased Array Ultrasonic Testing

This study presents innovative 2D phased array inspection system “HITCHI 3D Focus-UT” for 3D volume inspection. This system employees (1) 3D ray-trace simulator to set-up the delay time for array elements and delay pattern for 3D volume scanning, (2) high sensitivity 256CH phased array equipment to drive a 2D matrix ar ray simultaneously and to obtain 3D volumetric data, and (3) high-speed 3D data processing software to convert 3D volumetric inspection data into 3D voxel data and display 3D inspection ima...
英字タイトル:
Development of 3-Dimensional Ultrasonic Testing System “3D Focus-UT”