Tokyo Electric Power Co. is optimistic about a new cooling technique for a damaged reactor at Fukushima Daiichi, while outside the plant recent testing indicates many evacuated areas may be uninhabitable for years.
Developments this week in the multiple-reactor accident triggered by March’s earthquake and tsunami include:
Second Water Injection System Installed at Unit 3
TEPCO expects the core temperature of the unit 3 reactor will fall significantly in coming days as a new system begins spraying water onto its fuel from above. To date, crews have used a feed water system to pump coolant into the bottom of the reactor pressure vessel at six cubic meters per hour. The World Nuclear Association reported that TEPCO will begin introducing water from the top of the RPV as well through an existing injection valve that the utility has confirmed can be operated electronically. Starting on Thursday, TEPCO plans to gradually increase the new spray to 3 cubic meters per hour over three days while continuing the existing feed water injection. After a monitoring period, crews hope to bring the total water injected back to a total of 6 cubic meters per hour split between both systems, which TEPCO anticipates will speed the unit’s progress toward cold shutdown.
Many Areas Found to Be Uninhabitable as Regulators Form Decontamination Plan
Last weekend, test results published by Japan’s Ministry of Science and Education showed higher-than-expected levels of radiation in many areas of Fukushima Prefecture evacuated following the accident. Radiation levels above safe limits were found at more than three dozen sites within the 20-kilometer radius where the evacuation remains in effect. Radiation measured at some locations would create doses in excess of 500 millisieverts per year. An estimated 80,000 people were evacuated after the accident, and Japanese media reported this week that some are expected to be told soon that they can not return home for years.
Another team of scientists, from the Japan Atomic Energy Agency, began further testing in the region this week, and regulators released a decontamination plan Friday. The Nuclear Energy Institute reported earlier that the plan anticipates reducing radiation levels in residential areas by half over two years, with work expected to included surface soil removal, vegetation pruning and washing roofs and road surfaces.