Steels, corrosion testing radiation effects

Activity transport effects can be minimized by selecting materials with a low cobalt content and by rigid adherence to chemical specifications for the coolant. Because of the important role of corrosion product particles in this transport, filtration has been studied extensively as a means of reducing the rate of growth of radiation fields. High flows are needed to be effective and therefore the filters must operate at full coolant temperature. Two types of filter which have proved successful in pilot tests at the NPD reactor are a deep bed of graphite particles and a bed of steel balls in an electromagnetic field (61). 

Skerry, Alavi, and Lindgren have identified three factors of importance in the degradation and corrosion of painted steel that are not modeled by the salt spray test wet/dry cycling, a snitable choice of electrolyte, and the effects of UV radiation (critical becanse of the breakdown of polymer bonds in the paint) [3]. 

Dynamic tests of the reaction between Bi and steel in the presence of a radiation field must be completed before a final selection can be made of materials for the LMFR. The effect of velocity on corrosion is not certain from the out-of-pile studies, so that no exact analogy can be made between out-of-pile forced circulation loops and in-pile capsules. There has been limited work done at Harwell [6] with thermal convection loops in and out of a radiation field. These loops had no U but did contain Ca and Zr inhibitors. The data suggest that pile radiation may have induced some acceleration of mass transfer. 

The decreasing levels of SO2 and increasing frequency of car traffic has resulted in a new multi-pollutant situation in many urban and industrial areas. In order to possibly quantify the corrosion effects caused by this new multi-pollutant situation an extended exposure program was performed that took place between 1997 and 2001 and involved some 30 test sites in 18 countries in Europe and North America [91]. Specimens of carbon steel, zinc, copper, bronze, limestone, paint-coated steel, and glass representative of medieval stained glass windows were exposed for up to four years. At each site, the environmental data measured included climatic parameters (temperature, relative humidity, and sunshine radiation), gaseous pollutants (SO2, NO2, HNO3, and O3), particles (presented as PMio, i.e., concentration of particles with diameter < 10 pm), and precipitation (total amount, conductivity, and concentration of, i.e., H+, S04 , N03, Cl", NH4+). 

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