Institute for resource and Security Studies
27 Ellsworth Avenue, Cambridge, Massachusetts 02139, USA
Phone: (617) 491-5177 Fax: (617) 491-6904 E-mail: email@example.com
RISKS AND ALTERNATIVE OPTIONS ASSOCIATED
WITH SPENT FUEL STORAGE AT THE
SHEARON HARRIS NUCLEAR POWER PLANT
Executive Summary of a February 1999 report prepared
for Orange County, NC, by Gordon Thompson
Spent fuel at Harris
Carolina Power & Light Company (CP&L) requested, in December 1998, an amendment of its operating license for the Shearon Harris nuclear plant. The amendment, if granted by the Nuclear Regulatory Commission (NRC), would permit the activation of two currently unused spent fuel pools at Harris. The Harris plant was to have four units but only the first unit was built. (A unit consists of a reactor, a turbine-generator and associated equipment.) A fuel handling building was built to serve all four units. This building contains four fuel storage pools (A, B, C, D), a pool for loading or unloading fuel shipping casks, and three fuel transfer canals, all interconnected but separable by gates. Spent fuel can be stored in pools A through D and moved via the canals, while remaining under water at all times.
Pools A and B at Harris contain fuel racks, and are in regular use. They store spent fuel from the Harris reactor and from CP&L’s Brunswick plant (two units) and Robinson plant (one unit). CP&L seeks to activate pools C and D at Harris, which are now flooded but unused. By activating these pools, CP&L expects to have sufficient storage capacity at its three nuclear plants to accommodate all the spent fuel discharged by the four CP&L reactors (the Harris and Robinson reactors and the two Brunswick reactors) through the ends of their current operating licenses.
The fuel racks in pools A and B, and the proposed racks in pools C and D, employ a compact configuration which allows fuel to be stored at a high density. This arrangement contrasts with the low-density pool storage configuration that was used when nuclear plants first entered service. The United States has no national storage site or repository for spent fuel, so CP&L is currently obliged to store fuel at its plant sites. Compact storage in the existing pools is a comparatively cheap option for on-site storage.
The potential for a severe pool accident
Pool storage of spent fuel in a high-density configuration creates the potential for a severe accident. Loss of water from the pool can lead to an exothermic (heat-producing) reaction of the fuel cladding with air or steam, releasing a large amount of radioactive material to the atmosphere. Once released, the radioactive material would travel downwind and contaminate the environment. The amount of cesium-137 released from the fuel pools at Harris, given a loss of water, could be as large as 790 kilograms. For comparison, the 1986 Chernobyl reactor accident released 27 kilograms of cesium-137. A release of 790 kilograms of cesium-137 from Harris could require relocation of populations from an area as large as North Carolina, to avoid a significant increase in rates of cancer.
Several categories of event, including sabotage or terrorist events, could cause a loss of water from a Harris pool. One category would encompass accidents at the Harris reactor which release a significant amount of radioactive material. Analysis by CP&L shows the potential for such an accident, and the NRC requires offsite emergency planning to respond to accidents of this type. If such an accident occurred, cooling of the fuel pools would be interrupted and personnel could no longer gain access to the plant for purposes of restoring cooling. Water would then be lost from the pools by evaporation. Thus, the reactor accident would be followed by a pool accident. The pool accident would release much more cesium-137 and other long-lived radioisotopes than would the reactor accident.
CP&L’s plan for the activation of pools C and D raises other safety concerns. For example, CP&L intends to provide cooling and electrical supply to pools C and D from systems at Unit 1 which support the Harris reactor. This approach could increase the potential for reactor accidents.
Dry storage of spent fuel is a proven option that poses a lower level of hazard than high-density pool storage. The NRC has approved a range of dry storage designs. Similarly, low-density pool storage was once a common practice at nuclear plants and poses a lower level of hazard than high-density pool storage. CP&L could employ a spent fuel storage strategy which combines dry storage with low-density pool storage. If appropriately designed and implemented, this strategy would dramatically reduce the hazard posed by present and proposed fuel storage arrangements at Harris.
Gordon Thompson received a B.E. in mechanical engineering and a B.Sc. in mathematics and physics from University of New South Wales, Australia. He also received a Ph.D. in applied mathematics from Oxford University. Since 1977 Dr. Thompson has performed technical analyses of safety and environmental issues related to nuclear facilities. These analyses have been sponsored by a variety of nongovernmental organizations and local, state and national governments, predominantly in North America and western Europe. Dr Thompson has provided expert testimony in legal and regulatory proceedings, and has served on committees advising U.S. government agencies.
For more information, contact NC WARN, PO Box 61051, Durham, NC 27715 919-490-0747, NC WARN@NC WARN.org