New Inspection Plan Approved for CA Nuclear Site


A new inspection program was approved late last month by the California Coastal Commission to inspect and maintain dry storage tanks containing spent nuclear fuel at the San Onofre Nuclear Generation Station.

The CCC voted unanimously to approve the Inspection and Maintenance Program proposed by plant owner Southern California Edison.

Edison reportedly developed the program in response to a special condition in its 2015 Independent Spent Fuel Storage Installation (ISFSI) development permit issued by the CCC.


The IMP applies only to the Holtec International Storage Module Underground MAXimum Capacity (UMAX) system, which is an underground Vertical Ventilated Module dry spent fuel storage system.

The program, which will officially begin in 2024 with two canisters being inspected every five years, will also inspect the San Onofre test canister every two-and-a-half years. The test canister is an electrically heated, full-scale canister simulator without any spent fuel inside that is used to model potential effects of storage over time.

The company hired independent engineering firm LPI to review the program prior to sending it to the CCC. LPI found that the IMP was sufficient to detect wear until 2035.

However, LPI made several recommendations, which were all adopted into the IMP. Those recommendations included:

  • Flaw depth of 0.0625 inches as the threshold for fuel canister repairs. Any flaws deeper than that would need to be repaired;
  • A “more appropriate” statistical method for modeling the maximum depth of canister scratches that may occur during insertion and extraction;
  • Assessment of how future canister unloading operations can be optimized to minimize wear; and
  • Correction of a typographical or miscalculation error in a support document related to the potential scratch or wear mark depths on canisters.

Edison has maintained that it is unlikely a canister would require repair; however, the company selected a metallic overlay repair process for the work should it arise. The process would combine the robotic visual assessment used to inspect canisters, with metallic overlay technology, a high-energy, solid-state coating and powder application.


Tagged categories: Coating inspection; Inspection; NA; North America; Nuclear Power Plants; Quality Control

Join the Conversation:

Sign in to our community to add your comments.