Technology, Safety and Costs of Decommissioning a Reference Uranium Hexafluoride Conversion Plant
Safety and cost information is developed for the conceptual decommissioning of a commercial uranium hexafluoride conversion (UF{sub 6}) plant. Two basic decommissioning alternatives are studied to obtain comparisons between cost and safety impacts: DECON, and passive SAFSTOR. A third alternative, DECON of the plant and equipment with stabilization and long-term care of lagoon wastes. is also examined. DECON includes the immediate removal (following plant shutdown) of all radioactivity in excess of unrestricted release levels, with subsequent release of the site for public use. Passive SAFSTOR requires decontamination, preparation, maintenance, and surveillance for a period of time after shutdown, followed by deferred decontamination and unrestricted release. DECON with stabilization and long-term care of lagoon wastes (process wastes generated at the reference plant and stored onsite during plant operation} is also considered as a decommissioning method, although its acceptability has not yet been determined by the NRC. The decommissioning methods assumed for use in each decommissioning alternative are based on state-of-the-art technology. The elapsed time following plant shutdown required to perform the decommissioning work in each alternative is estimated to be: for DECON, 8 months; for passive SAFSTOR, 3 months to prepare the plant for safe storage and 8 months to accomplish deferred decontamination. Planning and preparation for decommissioning prior to plant shutdown is estimated to require about 6 months for either DECON or passive SAFSTOR. Planning and preparation prior to starting deferred decontamination is estimated to require an additional 6 months. OECON with lagoon waste stabilization is estimated to take 6 months for planning and about 8 months to perform the decommissioning work. Decommissioning cost, in 1981 dollars, is estimated to be $5.91 million for OECON. For passive SAFSTOR, preparing the facility for safe storage is estimated to cost $0.88 million, the annual maintenance and surveillance cost is estimated to be about $0.095 million, and deferred decontamination is estimated to cost about $6.50 million. Therefore, passive SAFSTOR for 10 years is estimated to cost $8.33 million in nondiscounted 1981 dollars. DECON with lagoon waste stabilization is estimated to cost about $4.59 million, with an annual cost of $0.011 million for long-term care. All of these estimates include a 25% contingency. Waste management costs for DECON, including the net cost of disposal of the solvent extraction lagoon wastes by shipping those wastes to a uranium mill for recovery of residual uranium, comprise about 38% of the total decommissioning cost. Disposal of lagoon waste at a commercial low-level waste burial ground is estimated to add $10.01 million to decommissioning costs. Safety analyses indicate that radiological and nonradiological safety impacts from decommissioning activities should be small. The 50-year committed dose equivalent to members of the public from airborne releases during normal decommissioning activities is estimated to 'Je about 4.0 man-rem. Radiation doses to the public from accidents are found to be very low for all phases of decommissioning. Occupational radiation doses from normal decommissioning operations (excluding transport operations) are estimated to be about 79 man-rem for DECON and about 80 man-rem for passive SAFSTOR with 10 years of safe storage. Doses from DECON with lagoon waste stabilization are about the same as for DECON except there is less dose resulting from transportation of radioactive waste. The number of fatalities and serious lost-time injuries not related to radiation is found to be very small for all decommissioning alternatives. Comparison of the cost estimates shows that DECON with lagoon waste stabilization is the least expensive method. However, this alternative does not allow unrestricted release of the site. The cumulative cost of maintenance and surveillance and the higher cost of deferred decontamination makes passive SAFSTOR more expensive than DECON. Several methods to assure that the licensee has adequate funds for decommissioning are considered. The methods investigated (all based on expected decommissioning costs) range from a single payment when plant operations begin, to payments into a sinking fund during the normal plant operating period, to a single payment when normal plant operations cease and decommissioning begins.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- Office of Nuclear Regulatory Research
- DOE Contract Number:
- DE-AC06-76RL01830
- OSTI ID:
- 1083948
- Report Number(s):
- PNL-3909; NUREG/CR-1757
- Country of Publication:
- United States
- Language:
- English
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