ALARA efforts in nordic BWRs
- ABB Atom, Vaesteraes (Sweden)
Some ALARA-related ABB Atom projects are currently under investigation. One of the projects has been ordered by the Swedish Radiation Protection Institute, and two others by the Nordic BWR utilities. The ultimate objective of the projects is to identify and develop methods to significantly decrease the future exposure levels in the Nordic BWRS. As 85% to 90% of the gamma radiation field in the Nordic BWRs originates from Co-60, the only way to significantly decrease the radiation doses is to effect Co and Co-60. The strategy to do this is to map the Co sources and estimate the source strength of Co from these sources, and to study the possibility to affect the release of Co-60 from the core surfaces and the uptake on system surfaces. Preliminary results indicate that corrosion/erosion of a relatively small number of Stellite-coated valves and/or dust from grinding of Stellite valves may significantly contribute to the Co input to the reactors. This can be seen from a high measured Co/Ni ratio in the feedwater and in the reactor water. If stainless steel is the only source of Co, the Co/Ni ratio would be less than 0.02 as the Co content in the steel is less than 0.2%. The Co/Ni ratio in the reactor water, however, is higher than 0.1, indicating that the major fraction of the Co originates from Stellite-coated valves. There are also other possible explanations for an increase of the radiation fields. The Co-60 inventory on the core surfaces increases approximately as the square of the burn-up level. If the burn-up is increased from 35 to 5 MWd/kgU, the Co-60 inventory on the core surfaces will be doubled. Also the effect on the behavior of Co-60 of different water chemistry and materials conditions is being investigated. Examples of areas studied are Fe and Zn injection, pH-control, and different forms of surface pre-treatments.
- Research Organization:
- US Nuclear Regulatory Commission (NRC), Washington, DC (United States). Div. of Regulatory Applications; Brookhaven National Lab. (BNL), Upton, NY (United States)
- OSTI ID:
- 54659
- Report Number(s):
- NUREG/CP-0143; BNL-NUREG-52440; CONF-940505-; ON: TI95008770; TRN: 95:012693
- Resource Relation:
- Conference: 3. international workshop on implementation of ALARA at nuclear power plants, Long Island, NY (United States), 8-11 May 1994; Other Information: PBD: Mar 1995; Related Information: Is Part Of Proceedings of the Third International Workshop on the implementation of ALARA at nuclear power plants; Khan, T.A. [comp.] [Brookhaven National Lab., Upton, NY (United States)]; Roecklein, A.K. [Nuclear Regulatory Commission, Washington, DC (United States). Div of Regulatory Applications]; PB: 810 p.
- Country of Publication:
- United States
- Language:
- English
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