Impact of Storage Time on the Needed Capture Efficiency for Volatile Radionuclides - 13369
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37849 (United States)
- Idaho National Laboratory (United States)
- Pacific Northwest National Laboratory (United States)
During the processing of used nuclear fuel (UNF), volatile radionuclides will be discharged from the facility stack if no recovery processes are in place to limit their release. The volatile radionuclides of concern are {sup 3}H, {sup 14}C, {sup 85}Kr, and {sup 129}I. There are three key regulations that address the release of these radionuclides to the environment- 40 CFR 61, 40 CFR 190, and 10 CFR 20. These regulations apply to the total radionuclide release and establish dose limits for the maximum exposed individual (MEI) in the public both in terms of whole body dose and dose to specific organs such as the thyroid. Each radionuclide released to the environment contributes to the total dose to some degree. In this paper we attempt to evaluate the efficiency requirements for the capture processes to limit the doses to the MEI to regulatory levels. Since the total amount of each volatile radionuclide present in the UNF changes with the age of the fuel, the respective capture requirements also change with time. Specifically, we are interested in the impact of the decreasing contribution of {sup 3}H and {sup 85}Kr, which have relatively short half-lives, 12.32 y and 10.76 y, respectively, with the increasing age of the fuel (i.e., time between when the UNF is removed from the reactor and the time it is processed) on the capture requirements. In this paper we examine the capture requirements for these four radionuclides for three fuel types (pressurized water reactor [PWR] with uranium oxide fuel [UOX], PWR with mixed oxide fuel [MOX], and an advanced high temperature gas-cooled reactor [AHTGR]), several burnup values, and time out of reactor extending to 200 y. We calculate doses to the MEI with the EPA code CAP-88 and look at two dose contribution cases. In the first case, we assume that the total allowable dose is attributed to only the four volatile radionuclides. This establishes the lowest capture efficiency value possible. Since this is unrealistic, because it assumes zero dose contribution from all other radionuclides, we also examine a second case, where only 10% of the allowable dose is assigned to the four volatile radionuclides. We calculate the required decontamination factors (DFs) for both of these cases for the three fuel types, multiple fuel burnups, and fuel ages and determine whether or not the dose to the whole body or to the thyroid that drives the capture requirements would require additional effluent controls for the shorter half-life volatile radionuclides based on dose considerations. This analysis indicates that the principal isotopes of concern are generally {sup 3}H and {sup 129}I, the latter requiring the highest DFs. The maximum DF value for {sup 129}I is 8000 for the evaluated cases and assumptions used. ∼60 for fresh fuels. The DF for {sup 14}C could be as high as 30 for certain fuels. These values are based on just meeting the regulatory limits, and additional engineering margins (perhaps 3x to 10x or higher) should be applied to provide a safety factor for compliance. However, by assuming less conservative dose allocations, taller stacks, different radionuclide speciation, fuel aging, and other reprocessing facility design and location parameters, the DF requirements could be significantly reduced. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22221353
- Report Number(s):
- INIS-US-13-WM-13369; TRN: US14V0546042308
- Resource Relation:
- Conference: Waste Management 2013 - WM2013 Conference: International collaboration and continuous improvement, Phoenix, AZ (United States), 24-28 Feb 2013; Other Information: Country of input: France; 11 refs.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
61 RADIATION PROTECTION AND DOSIMETRY
BURNUP
CARBON 14
DECONTAMINATION
DOSE LIMITS
ECONOMICS
HALF-LIFE
HTGR TYPE REACTORS
IODINE 129
KRYPTON 85
MIXED OXIDE FUELS
PWR TYPE REACTORS
RADIATION DOSES
REPROCESSING
THYROID
TRITIUM
URANIUM OXIDES
VOLATILITY
YTTRIUM 76