→ Summary of Reactor Status
On Saturday, 2 April 2011, the IAEA provided the following information on the current status of nuclear safety in Japan:
1. Current Situation
Overall at the Fukushima Daiichi plant, the situation remains very serious.
In preparation for transferring water in the basement of the Unit 1 turbine building to the condenser, water in the condenser storage tank is being transferred to surge tank of the suppression pool since 31 March, 03:00 UTC. Water in the trench was transferred to a water tank at the central environmental facility main building. The water level in the trench was reduced by 1 metre to 1.14 metre below the top of the trench on 31 March. On Unit 2 in order to prepare for removal of the water from turbine building basement, pumping of water from the condenser to suppression pool water surge was started 29 March, 07:45 UTC and was finished 1 April, 02:50 UTC. On Unit 3 in order to prepare for removal of the water from the turbine building basement, pumping of water from the condenser to suppression pool water surge was started 28 March, 08:40 UTC and completed 30 March, 23:37 UTC.
In a press release on 2 April, NISA reported the following: Water, with a dose rate of greater than 1 000 millisievert/hr, was confirmed by TEPCO at around 00:30 UTC on 2 April, in a pit, housing cables located next to the Unit 2 sea water inlet point. There exists a crack on the sidewall of the pit, about 20 cm in length, and water inside the pit is confirmed to be leaking directly to the sea. The isotopic analysis of water samples from inside the pit, the sea and near the seawater inlet bar screen filter is in process. Currently a plan to patch the pit with concrete is underway to stop the leakage. An investigation on the leakage path to this pit is on-going and measures to stop leakage to the sea will be implemented.
Transfer of fresh water from a US Navy barge to the "filtered water tank" started on 1 April, 06:58 UTC, and was suspended on 1 April, 07:25 UTC due to a connection failure. A second US Navy barge left Onahama port and planned to arrive 2 April, 00:30 UTC.
On Unit 1 fresh water has been continuously injected into the reactor pressure vessel through the feed-water line at an indicated flow rate of 8 m3/h using a temporary electric pump with diesel backup. The indicated temperature at the feed water nozzle of the RPV has decreased from 256 °C to 249 °C and at the bottom of RPV decreased from 128 °C to 119 °C. There was a corresponding decrease in RPV pressure and Drywell pressure.
Fresh water is injected continuously through fire extinguisher line on Unit 2 at an indicated rate of 9 m3/h using a temporary electric pump with diesel backup. The indicated temperature at the feed water nozzle of the RPV has decreased from 165 °C to 161 °C. The temperature at the bottom of the RPV was not reported. Indicated Drywell pressure remains at atmospheric pressure.
On Unit 3 fresh water is being injected continuously at an indicated rate of 7 m3/h into the reactor core through the fire extinguisher line using a temporary electric pump with diesel backup. The indicated temperature at the feed water nozzle of the RPV is about 119 °C and at the bottom of RPV is about 90 °C.
Fresh water (90 T) was pumped into the spent fuel pool in Unit 1 using a concrete pumping truck on 31 March. In Unit 2, injection of water into the spent fuel pond using the temporary pump was restarted on 1 April, 05:56 UTC. Fresh water (180 T) was pumped into the spent fuel pool on Unit 4 using a concrete pumping truck on 1 April.
Units 5 and 6 remain in cold shutdown with plant systems operating on off-site AC power.
2. Radiation Monitoring
On 1 April, deposition of iodine-131 was detected in 7 prefectures ranging from 7 to 74 becquerel per square metre. Deposition of cesium-137 in 9 prefectures was reported on April 1st ranging from 2.9 to 76 becquerel per square metre. Reported gamma dose rates in the 45 prefectures showed no significant changes compared to yesterday.
The Ministry of Agriculture, Forestry and Fisheries of Japan informed the IAEA that, because of winter conditions, most cattle, pigs and chickens are presently kept indoors. Animals are primarily fed on stored dried grass, silage and grain that has not been contaminated by the releases from the Fukushima Daiichi NPP.
On 31 March, NISA reported that among the workers at the Fukushima Daiichi plant, 21 workers have received doses exceeding 100 mSv. No worker has received a dose above 250 mSv, which is the dose limit for emergency workers.
On the 30 March, 180 000 Bq/l of I-131 and 15 000 Bq/l of Cs-137 were detected in the vicinity of the discharge water outlet of Unit 4.
The data reported for 27 - 30 March indicated that the levels at 30 m from the common discharge point of Units 5 and 6 were relatively constant at 45 000 - 55 000 Bq/l for I-131 and 10 000 - 15 000 Bq/l for Cs-137.
In addition to the 8 sampling points 30 km from the coast two additional monitoring stations were added in the South, 10km and 20 km from shore. The values reported for 28 and 30 March indicate a non-uniform distribution and trend.