Experimental Study of Aqueous Chemical Trisodium Phosphate-Buffered Environment Under Post-LOCA Conditions With Head Loss Measurements

Abstract

An integrated chemical effects test (ICET) was designed and executed to investigate the corrosion of materials in a hypothetical post-loss of coolant accident (LOCA) environment for pressurized water reactors (PWRs) and the resulting effects on the measured head loss in three vertical columns through multiconstituents debris beds. The head loss columns were isolated approximately after 72 h, as the measured head loss in all three columns approached or surpassed the maximum limit of the differential pressure (DP) cells. Additional bench scale tests were carried out to investigate the cause of high head loss in the three columns. Combination of epoxy agglomeration and adhesion to fiber resulted in subsequent blockage of the flow through the debris bed with no chemical precipitation was concluded as the most reasonable cause of high head loss observed in the test. The test continued thereafter up to 30 days as an integrated chemical effects test using the corrosion tank only. The results presented in this article demonstrate trends for zinc, aluminum, and calcium release that are consistent with separate bench scale testing and previous integrated tests conducted under trisodium phosphate (TSP)-buffered post-LOCA environmental conditions. In general, the total and filtered samples showed almost identical concentration of all metals (Al, Ca, Si, and Mg) except zinc which clearly indicate that no precipitation occurred. The release rate and maximum concentrations of the released materials were slightly different than the separate effect testing as a result of different experimental conditions (temperature, surface area-to-water volume ratio) and/or the presence of other metals and chemicals in the integrated test.