Dissolution of organic solvents from painted surfaces into water

The presence of volatile iodine in containment buildings is one of the majo r safety concerns in the potential event of nuclear reactor accidents. Orga nic impurities in containment water, originating from various painted struc tural surfaces and organic materials, could have a significant impact on io dine volatility following an accident. To determine the source and magnitud e of organic impurities and their effects on time-dependent iodine volatili ty, the dissolution for organic constituents from paints used in reactor bu ildings has been studied under postulated accident conditions. The studies of the organic dissolution from carbon steel coupons coated with zinc-prime d vinyl, epoxy-primed polyurethane or epoxy paints over the temperature ran ge 25-90 degrees C are reported. Relatively large activation energies were measured for the release of the principal organic compounds from painted su rfaces, suggesting it is the release of the solvents from the paint matrix rather than their diffusion through the solution that is the rate determini ng step for the dissolution mechanism. The similarities in the values of ac tivation energies for the dissolution of different organic compounds from t he paints suggest the release rate is independent of the nature of the pain ted surface or the type of organic being released from the surface. These t wo observations indicate that it may be possible to write a generalized rat e expression for the release of organic compounds from painted surfaces in containment following an accident. The possible implications of these resul ts for predicting iodine volatility in containment are also discussed.