United States Nuclear Regulatory Commission - Protecting People and the Environment

Humboldt Bay

1.0 Site Identification

Type of Site: Power Reactor Facility
Location: Eureka, CA
License No.: DPR-7
Docket No.: 50-133
License Status: DECON
Project Manager: John Hickman

2.0 Site Status Summary

Humboldt Bay, Unit 3 was a 65 MWe boiling water reactor plant located 4 miles southwest of Eureka, CA. The plant operated commercially from 1963 to 1976. On July 2, 1976, Humboldt Bay Power Plant (HBPP) Unit 3 was shut down for annual refueling and to conduct seismic modifications. In 1983, updated economic analyses indicated that restarting Unit 3 would probably not be cost-effective, and in June 1983, PG&E announced its intention to decommission the unit. On July 16, 1985, the U.S. Nuclear Regulatory Commission (NRC) issued Amendment No. 19 to the HBPP Unit 3 Operating License to change the status to possess-but-not-operate, and the plant was placed into a SAFSTOR status. SAFSTOR is the decommissioning method in which a nuclear facility is placed and maintained in a condition that allows the safe storage of radioactive components of the nuclear plant and subsequent decontamination to levels that permit license termination. In December 2003, PG&E formally submitted a license application to the NRC for approval of a dry-cask Independent Spent Fuel Storage Installation (ISFSI) at the Humboldt Bay site. A license and safety evaluation for the Humboldt Bay ISFSI were issued on November 17, 2005. The transfer of spent fuel from the fuel storage pool to the ISFSI was completed in December 2008, and decontamination and dismantlement of HBPP Unit 3 decommissioning commenced. HBPP successfully completed removal of the reactor vessel internals in September 2013.  The transfer of Greater Than Class C (GTCC) components into Independent Spent Fuel Storage Installation (ISFSI) Cask 6 was completed in November 2013.  The licensee has completed work on Control Rod Drive Mechanisms removal, piping systems and components removal from the off-gas tunnels, suppression chamber down-comers piping removal and removal of the spent resin disposal tank and components from the Liquid Radwaste System.  In addition, the Turbine Building has been demolished.

3.0 Major Technical or Regulatory Issues

At Humboldt Bay, the caisson was a first of its kind to house a nuclear containment structure, pressure suppression chamber, and nuclear steam supply system below grade.  A caisson is a water tight structure used as a foundation or to carry out work below grade.  The initial advantages of using a caisson included additional radiological shielding provided by the soils, physical protection being below grade and external pressure suppression in the event of an accident.  The construction of the caisson ultimately placed the lowest floor at approximately 66 feet below sea level, the bottom of the structure about 80 feet below grade, and most of the structure is below the water table.

To accommodate the deep structure removal of the caisson, the project scope was expanded to include: installation of a cut-off slurry wall 170 feet deep surrounding the caisson to a clay layer; installation and operation of a dewatering system inside the slurry wall to remove and control water infiltration; removal or the caisson; and waste management and handling.

4.0 Estimated Date For Closure

12/31/2017

Page Last Reviewed/Updated Friday, March 04, 2016