While preparing for an inspection inside unit 2’s reactor well, workers found new damage. The reactor cavity differential pressure adjustment line pipe was the planned location to insert a scope into the reactor well. This pipe is used to change the pressure between the reactor well and the refueling floor.
TEPCO inspected the portion of this differential pipe where it exits the containment structure. They found the valve for this pipe was open. A path of damage to the pipe and HVAC duct was found. High levels of radioactive contamination were found in the bottom of the HVAC duct and along a stained trail 4 meters below.
The damage to the duct work was described as alkaline rot of the zinc in the HVAC duct caused by “cesium oxide” and high temperature steam. Unit 2 produced large volumes of steam soon after the initial disaster and continued to purge steam out of the reactor well for years.
The trail of stains from the damaged HVAC section of the pipe has higher levels of contamination than surrounding areas. This appears to indicated a path of radioactive steam from the reactor through the reactor well to the reactor building hallway.
Varying types and levels of contamination were found in and around the pipe, and in the floor area below.
Attempts will be made to decontaminate this area near the pipe to reduce the exposure to workers. The pipe would be cut and inspection scopes inserted to look in the reactor well area.
How much this area contributed to radioactive leaks over the years is unconfirmed. The area has notable contamination but not as high as other leaks from containment such as the lower hatches on the first floor. The inspection of the reactor well could give some important new information about the initial meltdown conditions and the damage in this area. TEPCO did not provide a date for any of the future work related to this pipe.
Document machine translated to English:
Original document in Japanese
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