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Canister Carelessness:
NUKE Near Miss
Don Mosier | Rimini Road

This photo of the spent fuel cannister (white) was taken during a correct transfer of the cannister to its vertical silo. The image shows safety secondary rigging being attached to the canister,
a critical safety step that was omitted prior to the accident
on August 3rd when the cannister teetered
on the edge of disaster.
(Photo courtesy of the NRC).
Click to enlarge.

After the near drop of a highly radioactive fuel storage canister on August 3rd, the Nuclear Regulatory Commission (NRC) put a halt to movement of spent fuel from cooling pools at San Onofre Nuclear Generating Station (SONGS) to “semi-permanent” storage in half-buried concrete tombs. The review of that incident by the NRC is nearing conclusion, and a few new facts surrounding the near drop have emerged. The operator of the gantry crane (see photo) was new to the job, as was the individual overseeing the safety rigging that should have been attached to the fuel canister, but was not on August 3rd. The NRC accident report cited deficiencies in training and supervision, although it is unclear from the report whether or not these new employees had received any training.

Southern California Edison (SCE), the major owner and operator of SONGS, has now contracted with Holtec International, the manufacturer of the storage canisters, to oversee the canister transfer. SCE officials now say 11 workers or oversight personnel will be required when canisters are transferred, compared to nine in August. A camera has also been mounted near the top of the heavy gantry crane that lifts the canister and moves it into the appropriate storage cavity. The slings supporting the canister now have load sensors that transmit data to computer monitors. These changes in procedure have been reviewed by the NRC but fuel loading activities are still suspended until a further analysis of scratches to the canisters is completed.

The NRC released the results of their safety inspection on March 21st. Violation #1, failure to provide redundant drop protection, resulted in a proposed civil penalty of $116,000. Violation #2, failure to notify the NRC of the accident within 24 hours, resulted in no penalty because SCE received credit for appropriate corrective actions. SCE has the right to contest the civil penalty.

The concern about the safety of spent nuclear fuel at SONGS is related to the large amount of radioactivity on the site that will take thousands of years to decay. Approximately 43 percent of the intermediate and long-lived radioactivity in the spent nuclear fuel at SONGS is Cesium-137 (Cs-137). The reactors at SONGS have generated about 210 million curies of Cs-137. Of that, about 168 million curies of Cs-137 are in the two spent fuel pools. By comparison, this quantity of Cs-137 is more than 6 times the amount released by all atmospheric nuclear weapons tests, and about 89 times that released by the Chernobyl accident. To date, 29 of 104 canisters have been transferred from the cooling pools to the canister storage area, which means that 120 million curies remain in the two pools (one curie is a huge dose of radioactivity: 1 curie = 3.7 x 10 trillion disintegrations per second). Even release of radioactivity from one ruptured storage canister would render much of Southern California uninhabitable, so transfer of these canisters must be a fail-safe operation.

 

 

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