ID :
185164
Sun, 05/29/2011 - 16:59
Auther :
Shortlink :
https://oananews.org//node/185164
The shortlink copeid
Cooling system pumps stop for 15 hours at Fukushima plant's No. 5 unit
TOKYO (Kyodo) - Tokyo Electric Power Co. said Sunday pumps to cool the nuclear reactor and fuel pool at its crippled Fukushima Daiichi power plant's No. 5 unit, which had been in a state of ''cold shutdown,'' stopped for around 15 hours until backup pumps were activated.
The temperature inside the reactor rose to as high as 94.8 C after the unit's pumps were found to have stopped Saturday night but fell after switching to the backup pumps to restore the cooling system, the utility known as TEPCO said.
If the unit had been left unattended with the temperature surpassing 100 C, the water containing nuclear fuel inside the reactor could have boiled and evaporated, thereby exposing the fuel and damaging it.
But the government's Nuclear and Industrial Safety Agency said there was no danger of the No. 5 reactor falling into a serious condition because there are backup pumps and methods for injecting water inside the unit.
TEPCO admitted that while it had reported the incident to the central and Fukushima prefectural governments on Saturday night, it lacked consideration in waiting to make the information public until Sunday morning.
''If the backup pumps did not work, we could have faced a situation in which we might have had to start injecting water into the reactor as an alternative step,'' TEPCO spokesman Junichi Matsumoto said. ''We regret not having announced it sooner.''
Heated water in the No. 5 unit had been cooled by water and seawater using the residual heat removal system and the pumps that broke down were makeshift pumps set up to draw in seawater, according to TEPCO officials.
The problem may have been caused by insulation failure in the electrical system, the officials said.
When a worker patrolling the plant became aware of the problem at around 9 p.m. Saturday, the temperature of the water inside the reactor was around 68 C. It had risen to 94.8 C at 12:49 p.m. Sunday, they said.
After the March 11 earthquake and tsunami ravaged the plant in Fukushima Prefecture, the No. 5 reactor could achieve a stable state of ''cold shutdown'' because workers were able to use the residual heat removal system.
The temperature inside the reactor rose to as high as 94.8 C after the unit's pumps were found to have stopped Saturday night but fell after switching to the backup pumps to restore the cooling system, the utility known as TEPCO said.
If the unit had been left unattended with the temperature surpassing 100 C, the water containing nuclear fuel inside the reactor could have boiled and evaporated, thereby exposing the fuel and damaging it.
But the government's Nuclear and Industrial Safety Agency said there was no danger of the No. 5 reactor falling into a serious condition because there are backup pumps and methods for injecting water inside the unit.
TEPCO admitted that while it had reported the incident to the central and Fukushima prefectural governments on Saturday night, it lacked consideration in waiting to make the information public until Sunday morning.
''If the backup pumps did not work, we could have faced a situation in which we might have had to start injecting water into the reactor as an alternative step,'' TEPCO spokesman Junichi Matsumoto said. ''We regret not having announced it sooner.''
Heated water in the No. 5 unit had been cooled by water and seawater using the residual heat removal system and the pumps that broke down were makeshift pumps set up to draw in seawater, according to TEPCO officials.
The problem may have been caused by insulation failure in the electrical system, the officials said.
When a worker patrolling the plant became aware of the problem at around 9 p.m. Saturday, the temperature of the water inside the reactor was around 68 C. It had risen to 94.8 C at 12:49 p.m. Sunday, they said.
After the March 11 earthquake and tsunami ravaged the plant in Fukushima Prefecture, the No. 5 reactor could achieve a stable state of ''cold shutdown'' because workers were able to use the residual heat removal system.
