Experimental observations of boric acid precipitation scenarios
Conference Paper
Overview
Identity
Additional Document Info
View All
Overview
abstract
During a Loss of Coolant Accident (LOCA) in Light Water Reactors (LWR). borated water is injected into the core through the safety injection system. The continuous vaporization of the water from the core may increase the concentration of boric acid in the core that, under certain conditions may reach the solubility limit and precipitate. This includes scenarios where the liquid water supply to the core if affected blockages due for example to debris accumulation. Questions have been raised on the effects of the precipitate in the core on the flow behavior, including the possibility of additional blockages produced by precipitate accumulation. A simple experimental facility was constructed to perform simple experimental observations of the behavior of borated water under the combined effects of the boiling and the boric acid precipitation (BAP). The facility consists of a transparent polycarbonate vertical pipe where forty-five heated rods have been installed to supply the power to the water to reach the saturation temperature and maintain a given boil-off rate. The layout and geometry of (he experimental apparatus were design to emulate a simplified core of a Pressurized Water Reactor (PWR). Experimental observations have been conducted under two different conditions. The first test was executed to observe the behavior of the water and the boric acid precipitate during a boil-off scenario with without external borate water addition (decreasing water level). During the second test, borated water was constantly injected from the top of the test section to maintain a constant mixture level in the test section. Both tests assumed no How from the bottom of the test section which may be the ease of PWR LOCA scenarios in presence of debris-generated core blockagc. The observations performed with a set of three cameras installed around the test section, showed interesting effects of the vapor bubbles on the boric acid precipitate migration and accumulation in the test section. The results may help addressing some basic questions regarding the effect of the precipitation of boric acid during core blockage LOCA scenarios and, provide the basis for further experimental or computational analysis required to resolve the BAP issue as part of the Generic Safely Issue 191.
