Engineers for Edison and Mitsubishi, writing last year in a trade magazine, said they needed to design generators that would require only minor modifications within the rest of the plant, but also meet a federal test to qualify as "in-kind," or essentially identical, replacements, which would allow them to be installed without prior approval from federal regulators.
Boxer said the report documented that Edison and Mitsubishi rejected some safety modifications, apparently because they believed they could force the company to seek a lengthy license amendment. It also indicates the decision to reject additional safety modifications contributed to the faulty design, she said.
Boxer's office did not release the report.
The generators, which resemble massive steel fire hydrants, control heat in the reactors and operate something like a car radiator. At San Onofre, each one stands 65 feet high, weighs 1.3 million pounds, with 9,727 U-shaped tubes inside, each three-quarters of an inch in diameter.
Overall, NRC records show investigators found wear from friction and vibration in 15,000 places, in varying degrees, in 3,401 tubes inside the plant's four generators, two in each reactor.
The plant is owned by SCE, San Diego Gas & Electric and the city of Riverside.
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