High radiation levels are impeding workers from switching on the reactors' cooling pumps. On 26 March, JAIF reported that high radiation levels have rendered the job impossible.
On 24 March three workers laying cable on the first floor and basement of a turbine building were exposed to radiation of more than 170mSv, TEPCO said. Two confirmed that their legs were contaminated, which might lead to beta-radiation burn injuries. They were initially transferred to Fukushima Medical University hospital; the third worker joined them on 25 March; all three have since been sent to the National Institute of Radiological Sciences. The water surface had a radiation of 400 mSv/hr, dominated by Iodine 131 and Cerium 144. In a statement, TEPCO blamed the workers for not evacuating the area after the dosimeters they were wearing started to beep.
Also, water that accumulated in the basement of the unit 1 and 3 turbine halls was found to have 10,000 times the radioactivity of water circulating through the reactor in normal circumstances. TEPCO has begun to drain off the water, JAIF said.
The highly-radioactive water in the turbine hall probably leaked from the units 1 and 3 containment, JAIF reported. A separate TEPCO report on 25 March said that there is no indication of reactor coolant leakage at units 4, 5 or 6.
Also, high levels of radioactive iodine have been found in a sample of seawater 300m from the discharge limit, 1,250 times the legal limit, according to JAIF.
Concerns about the chemical and mechanical effects of seawater being injected at the Fukushima-Daiichi primary circuits of reactors 1 and 3 (particularly erosion and salt deposition) have prompted workers to change the source of emergency cooling to fresh water on 25 March, according to the Japan Atomic Industrial Forum. Unit 1 pump capacity is 120L/min; unit 3 pump capacity is 240 L/min. They are also preparing to switch unit 2 cooling, and cooling of an unspecified spent fuel pool, to fresh water, it said. The water is being pumped from the Sakashita dam in Fukushima prefecture.
In other developments: the unit 5 residual heat removal system pump (seawater) which tripped on 23 March was replaced on 24 March, when cooling restarted.
Work to reconnect site systems to the electricity grid have enabled workers to begin cooling spent fuel pools with site equipment: on 25 March the fuel pool cooling and filtering (clean up) systems for the unit 4 and unit 2 spent fuel pools were started up, drawing seawater for cooling. The unit 3 spent fuel pool FPCF system was also started up and began seawater injection on 24 March, according to TEPCO. The common fuel pool cooling pump was also started up on 24 March.
FilesReactor-by-reactor, system-by-system summary from JAIF on 27 March Fukushima-Daiichi parameters