I have often blogged about the problem of spent nuclear fuel assemblies that are piling up in the cooling pools of U.S. nuclear reactors. There is no permanent geological repository for spent nuclear fuel in the U.S. The attempt to build such a repository at Yucca Mountain in Nevada was cancelled in 2009 although there are members of Congress who are trying to get that project going again. The only path forward seems to be the creation of interim storage facilities with dry casks to hold spent nuclear fuel assemblies.
After the San Onofre nuclear power plant in San Diego, CA was shut down, the spent nuclear fuel had to be dealt with. Following a great deal of debate and discussion, it was decided to store the spent nuclear fuel in dry casks called HI-STORM UMAX constructed by Holteck International. They are a well-known dry cask company and brag about how advanced their HI-STORM UMAX dry casks are.
South California Edison (SCE), the owners of the San Onofre nuclear power plant, are responsible for the decommissioning of the old nuclear power plant. This includes dealing with the spent nuclear fuel. A few weeks ago, SCE technicians were loading spent nuclear fuel assemblies into HI-STORM UMAX dry casks when they discovered a loose pin at the bottom of aluminum shims. The shims are supposed to provide space for helium gas to flow around the fuel assemblies to cool them. SCE stopped loading spent fuel assemblies into the casks for a week while they explored this finding.
Holtec engineers informed SCE that they had made a design change to some of the HI-STORM UMAX dry casks supplied to SCE. SCE has requested that Holtec provide SCE with all the information they have on the design change. They have also requested that Holtec run thorough tests on the design change and inform SCE of the results.
It turns out that of the seventy three dry casks Holtec has supplied to SCE for San Onofre, thirty of the casks conform to the original design for the UMAX series while the remain forty three cask have the new design where the problem was discovered. SCE has resumed loading spent fuel assemblies into the casks with the original design which is widely used in the construction of dry casks.
Ray Lutz is with the watchdog group, Citizens Oversight. He said "It’s pretty worrisome that the first four canisters that they loaded, already, we're notified that they are having these defects, and now, when they were asked, 'Can we open them up and replace these parts?' they said, 'No, no one has ever opened these canisters up, we don’t know how to do it — it would take years of research."
SCD began the task for removing hundreds of spent fuel assemblies stored in the cooling pool at San Onofre this January. The spent fuel assemblies are being inserted into the dry casks which are partially buried after being encased in concrete. The casks are stored next to the beach at San Onofre. A citizen’s group has asked for a permanent monitoring system around the casks to detect any leakage of radioactive materials. A new panel has just been appointed to consider how and where to store the spent fuel.
