According to Kahoku Shinpo, a Fukushima local paper, TEPCO admitted on November 15, 2013 that there are 70 fuel assemblies with damaged fuel rods in the Reactor 1 Spent Fuel Pool, located on the operating floor (top floor) of the reactor building whose air radiation levels are measured in millisievert/hour and sievert/hour (first floor).
There are also three such fuel assemblies in the Reactor 2 SFP, and four of them in the Reactor 3 SFP.
Total 80 spent fuel assemblies in the SFPs in Reactors 1 – 4 are damaged.
The damages had been there long before the March 11, 2011 accident, and TEPCO claims it properly notified the national government as they discovered the damages. But the company has come clean in public only now.
Kahoku Shinpo article below suggests that the oldest of such damaged fuels may have been there for 40 years in the Reactor 1 Spent Fuel Pool. (Reactor 1 started generating electricity in 1971.)
Reactor 1 at Fukushima I Nuke Plant is TEPCO’s oldest nuclear reactor; it was entirely the project by General Electric of the US, a turnkey.
From Kahoku Shinpo (11/16/2013):
Fukushima I Nuke Plant Reactor 1 has 70 fuel assemblies damaged before the March 11, 2011 disaster, a quarter of the total spent fuel assemblies [in the Spent Fuel Pool of Reactor 1]
It was revealed on November 15 that 70 fuel assemblies in the Reactor 1 Spent Fuel Pool at Fukushima I Nuclear Power Plant had had damages before the March 11, 2011 earthquake/tsunami.
The damaged assemblies are about one-quarter of the 292 spent fuel assemblies stored in the pool. Technologies to remove damaged fuel haven’t been established, and there are worries that [the revelation] may negatively affect the plan to remove the fuels from Reactor 1 [SFP] starting 2017 and the decommissioning work in general.
TEPCO hadn’t disclosed all the facts until November 15. The company says it had reported to the national government as required.
According to TEPCO, these 70 fuel assemblies had series of problems including leakage of radioactive materials from small [pinhole-size] holes [on fuel rods]. So the company removed them from the reactor and stored in a separate location inside the Spent Fuel Pool.
There are three damaged fuel assemblies inside the Reactor 4 Spent Fuel Pool, where the removal of the fuel assemblies will start on November 18. TEPCO has postponed the removal of the damaged assemblies as it is difficult to remove them in a normal manner.
Other than in the Spent Fuel Pools of Reactor 1 and Reactor 4, the Reactor 2 Spent Fuel Pool has three damaged fuel assemblies, and the Reactor 3 Spent Fuel Pool has four, making the total of damaged fuel assemblies 80. TEPCO will consider the measures such as building a dedicated container for transfer for these damaged fuels.
As to the reason why Reactor 1 has the largest number of damaged fuels, TEPCO says, “Reactor 1 [at Fukushima I Nuke Plant] is the oldest nuclear reactor of our company, and we hear that there were quality control issues when the fuel rods were manufactured and that there were many fuel rods with inferior quality. From Reactor 2 onward, much improvement was done on the fuel rods, and quality improved.”
Reactor 1 at Fukushima I Nuke Plant is the first nuclear reactor for TEPCO, and it started the commercial operation in March 1971.
No major national newspaper has covered this story so far.