Experimental analysis of the aqueous chemical environment following a loss-of-coolant accident

Abstract

Five different 30-day tests were conducted to simulate the chemical environment in a pressurized water reactor containment water pool after a loss-of-coolant accident (LOCA). All chemical environments within the test apparatus included boric acid, lithium hydroxide, and hydrochloric acid. In addition, trisodium phosphate, sodium hydroxide, and sodium tetraborate were used to control pH in separate tests. Materials tested within this environment included representative amounts of submerged and unsubmerged metal coupons, concrete, insulation debris samples, concrete particulate, and latent debris. Visible changes were seen on the both submerged and unsubmerged metal coupons in each test because of corrosion. The tests with calcium silicate (cal-sil) insulation had considerably more sediment than the other tests with fiberglass insulation. Particulate deposits were found only on the exterior surfaces of the fiberglass bundles. The most particulate deposits were found on the fiberglass exterior from the test that involved cal-sil insulation and trisodium phosphate (TSP). In addition, snow-like white precipitates were found on top of the sediment in that test, that were rich in calcium and phosphorus. Precipitates were also present in the solutions of two tests when the solution was cooled to room temperature. These precipitates have high contents of aluminum and boron with small amounts of sodium and calcium. The presence of insulation debris, precipitates, and sediments is significant because of the impact they may have on the ECCS recirculation process.