AMBIENT-TEMPERATURE CONTAMINATION OF PROCESS PIPING AND THE EFFECTS OF PRETREATMENT

The results are presented of a study of pretreatment methods as possib le controls on the buildup (plateout) of cobalt and cesium activity on the inside surfaces of mild and stainless steel piping used to carry radioactive liquors. Coupon specimens of mild steel and Type 304L and 18/13/1 stainless steel piping are treated by contacting with acid and electroetching. Also, the effect on plateout of saturating steel coup ons with inactive cobalt is investigated. In addition, the transient e ffects of pH, concentration changes, and liquid turbulence on untreate d surface buildup are presented. Surface treatment is shown to delay a ctivity buildup in certain instances but does not affect the magnitude of overall surface activity. For untreated and treated surfaces, plat eout is dependent on solution pH and isotope concentration. The higher the pH and the higher the concentration, the greater the deposition w ill be. The effects of turbulence cause only a marginal decrease in pl ateout at each pH level and concentration studied. The steel type has a major effect on the activity picked up. The mild steel specimen show s the greatest activity buildup.