Improvements of Water Chemistry for Moderating Environmental Impacts of BWR Plants.

Abstract

In order to cause fewer environmental impacts, nuclear power plant systems and operational procedures with fewer radwaste sources, lower occupational exposures and smaller operational areas contaminated by radioactivity which will minimize internal exposure, have been established. Collaborative efforts have demonstrated that the combined application of major improvements in the systems and better operational procedures (e.g., (1) prevention of fuel defects, ( 2 ) application of low cobalt containing and corrosion resistant materials for the primary cooling system, (3) improvement of condensate water cleanup system and the resins applied to it, and (4) careful water chemistry control) is resulting in BWRs involved in the Japanese Improvement and Standardization Program (JISP BWRs) having occupational exposure of less than 0.5 man.Sv/yr, minimized contaminated areas in turbine buildings to only around the main steam turbines, and radwaste sources producing fewer than 500 drums/yr. Additionally, the JISP BWRs have high reliability with more than a 75% duty factor and unscheduled plant shudown occurrences of fewer than once in 10 years. K E Y W O R D S

Application of In-Service Temperature Lowering to Reduce Radioactivity Corrosion Product Deposition on Carbon Steel Piping of BWR Residual Heat Removal System

“…The steam flow rate, when the turbine bypass valve was opened to the maximum, was 5.9×10 4 kg/h at a reactor water temperature of 150…”

“…1) In recent years, radiation exposure in the primary containment vessel (PCV) has been reduced along with a lowered dose rate on the PLR piping. [2][3][4] As a result, radiation exposure due to radiation sources of the RHR piping is now 30 to 50% of the total exposure. In the advanced BWR (ABWR), in particular, internal recirculation pumps are used without the PLR system, so that the RHR piping has become the dominant radiation source in the PCV.…”

A Mechanism for Corrosion Product Deposition on the Carbon Steel Piping in the Residual Heat Removal System of BWRs.

“…3) Radiation exposure in the PCV has been greatly reduced along with a lowered dose rate on the PLR piping. [4][5][6][7] As a result, exposure due to radiation sources of the RHR piping is now 30 to 50% of the total exposure. For the advanced BWR (ABWR), internal recirculation pumps are used without the PLR system, so that the RHR piping becomes the dominant radiation source in the PCV.…”