27 Janvier 2013
Posted by Mochizuki on January 26th, 2013
On 1/19/2013, Tepco employee found a water leakage at the water treatment building. Due to this accident, they got to have to feed water to skimmer surge tank of reactor1 by a fire pump car. However, they had a water leakage then again.
Also, they had another water leakage at the chemical tank of decontamination equipment on 1/24/2013. These are due to the freezing water and in appropriate installation of the valves, which shows they had no improvement since last year.
It is estimated they are going to have 38 more winters to decommission Fukushima nuclear plants.
- From 1:54 PM to 2:22 PM on January 24, Unit 1 spent fuel pool alternative cooling system was suspended while feeding water to the skimmer surge tank of Unit 1 spent fuel pool by a fire pump car. The spent fuel pool water temperature when the cooling system was restarted was 10.0℃, which was the same as that of when the cooling was suspended. (Though usually water is fed into Unit 1 spent fuel pool skimmer surge tank via the filtrate water pipe, a fire pump car was used instead since the main valve of the filtrate water pipe is closed due to leakage from the valve installed on the filtrate water pipe header found on January 19.) While feeding water into the skimmer surge tank by a fire pump car, water (filtrate water) leakage was found at the flange of the water feeding pipe installed in the large carry-in entrance at Unit 1 Reactor Building. The amount of leaked water is approx.2L (Affected area: Approx. 2mx1m with a small depth). The leakage stopped after water feeding into the skimmer surge tank was stopped. From 2:42 PM to 3:05 PM on January 25, Unit 1 spent fuel pool alternative cooling system was suspended in order to feed water into the skimmer surge tank by a fire pump car after the leakage area was repaired. The spent fuel pool water temperature when the cooling was restarted was 10.5℃ (the same as when the cooling was suspended). No problem was found with the leakage location.
- At around 1:15 PM on January 19, a TEPCO employee found filtrate water leaking in the form of a mist from the filtrate water header valve used for feeding water to the spent fuel pool which is installed in the former Water Treatment Building. The area affected by leakage is approx. 1mx1m when the leakage was first found. The leaked water is kept in the building and has not flowed to the outside. After closing the valve located in the upstream side of the filtrate water pipe, the leakage amount was reduced to 2 drops per second. As a result of inspection, a crack was found on the filtrate water header valve where the leakage was found. As a result of investigation performed afterwards, it was found that though the valve of concern is installed inside the building, the installation condition is the same as those installed outside considering that the outer walls of the building were damaged due to the earthquake and no insulation material was installed on or near the valve. Under such installation conditions, the water remaining in the pipe froze and the pipe got expanded causing the valve to be damaged. As the valve and the pipe on which the valve is installed are not planned to be used, the valve has been removed and a closure panel has been installed on the flange in the upstream side of the pipe. Insulation material was also installed on the pipe to prevent freezing. After implementing these measures, water dripping was stopped. We will check the valve for leakage and install insulation material on the valves installed in the building. The incident has no impact on feeding water to the spent fuel pool.
- On January 24, after replacing the gasket of the flange on the pipe which feeds water into the chemical tank of the decontamination equipment (flange located on the tank side of the reducer), a TEPCO employee found filtrate water leaking from the reducer at around 3:10 PM while checking for leakage using fire hydrant water (filtrate water). The leakage stopped after closing the main valve of the fire hydrant. The amount of leakage was approx. 20L (affected area: approx. 3mx3mx2mm in depth) and the leaked water remains in the dam of the chemical tank. Considering that a crack was found on the reducer and no insulation material was attached on it, the crack is assumed to have been caused by freezing. The damaged reducer will be repaired with insulation material attached on it.