Corporate Information

Press Release (Sep 24,2009)
Planned Shutdown of Kashiwazaki-Kariwa Nuclear Power Station Unit No.7 for Refueling
The Tokyo Electric Power Company, Inc. (TEPCO) has been cautiously continuing the 
operation of Unit No.7 of the Kashiwazaki-Kariwa Nuclear Power Station by using 
power suppression testing*1 in order to verify that radiation leakage from the 
identified leaking fuel assembly is appropriately restrained and that the assembly's 
state remains stable. During this operation, operational and monitoring data have 
been collected and compiled for enhancing our knowledge. 
Unit No.7 was also due for a shutdown for a partial replacement of fuel in late 
September 2009 before its scheduled regular inspection. This was a decision made in 
consideration of comprehensive issues, including that Unit No.7 was the first plant 
that resumed operation after the Niigata-Chuetsu-Oki Earthquake. 

The collection and compilation of operational and monitoring data for Unit No.7, 
which continued until today, will end as we start the procedure to reduce the output 
of the generator at 10:00 a.m. on September 25, 2009 and stop power generation at 
around 11:00 p.m. Subsequently, the reactor will be shut down at around 1:00 a.m. 
on September 26.

After the reactor shutdown, all the fuel assemblies loaded in the reactor will be 
subjected to a sipping test*2 to detect the source of the radiation leak, and the 
identified leaking assembly will be replaced. For the sake of providing better 
reliability, the leaking assembly as well as 96 other assemblies that are not 
equipped with a foreign matter filter will be replaced with a new type of fuel 
assembly with a foreign matter filter*3.
Any fuel assemblies from which radiation leakage was detected during the sipping 
test will be subjected to detailed inspection, including visual inspection, in 
order to investigate the cause of the leak. 

The results of the test will be summarized and reported to the national and local 

TEPCO will step up efforts to make its power stations more resistant to disasters 
and thereby provide better safety and peace of mind. At the same time, TEPCO will 
appropriately perform inspections, evaluations and restoration work at its plants 
and will responsibly explain the results to people in the local community and 
society in general, just as it always has.

*1 Power suppression testing
   When a radiation leak from fuel occurs during plant operation, where the leaking 
   assembly is loaded can be identified by operating control rods while restricting 
   the output of the plant, and then by taking high-sensitivity off-gas monitor 
   readings during that operation. This method also allows the plant to continue 
   stable operation at rated output, with the control rods around the identified 
   leaking assembly inserted for the restriction of output. Power suppression 
   testing is a proven technique that has been used in many cases for the purpose 
   of continuing plant operation. 

*2 Sipping test
   An inspection to identify a leaking fuel assembly by measuring the concentration 
   of the gaseous radioactive material released from the given assembly. For 
   measurement, the target fuel assembly, which is loaded in the reactor, is lifted 
   a few meters to reduce water pressure applied to it.

*3 New type of fuel assembly with a foreign matter filter
   A fuel assembly equipped with the filtration function at its bottom in order to 
   further reduce the influence of foreign matter on the fuel. 

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