TEPCO has reported radiation dosage measurements above the water surface of the spent fuel pool of Unit 4.
- 84 mSv/hr
This means that in a little over an hour of exposure, the maximum annual dosage for a nuclear industry worker of 100 mSv would be reached. Normally elevated radiation levels would not be detected at this location and certainly not levels of this magnitude, which suggests that the fuel rods in the pool are damaged. TEPCO says that based on a preliminary analysis of water samples from the pool it believes that most of the fuel rods in the pool are undamaged.
TEPCO also measured the temperature of the pool on Tuesday using an extensible arm on a special vehicle and found that the temperature of the water in the spent fuel pool of Unit 4 is about 90o C. The normal temperature is less than 40o C. TEPCO thinks that the water level is about 5 meters below normal, but still 2 meters above the fuel rods. The spent fuel pool contains all the operational fuel rods from the Unit 4 reactor which was undergoing maintenance when the earthquake struck March 11.
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