Dose reduction benefits of zinc injection into the primary cooling system of a pressurized water reactor

Abstract

Koeberg Nuclear Power Station has set itself the objective of achieving world top quartile performance in terms of dose to workers. Achieving this goal requires implementation of a number of dose reduction initiatives. One such initiative is the continuous injection of depleted zinc acetate into the primary cooling system of the plant as a means of cobalt reduction, the principal contributor to out-of-core radiation fields. The purpose of this research report is to investigate the measure of success in reducing the radiation dose that nuclear plants world-wide have achieved through zinc injection, and how Koeberg measures up to international results. The investigation method included an extensive literature study on international experiences and results of other cobalt reduction methods, the benefits of zinc injection, as well as the potential negative impact it may have on major plant components. The report also presents the results of Koeberg’s zinc monitoring programme while comparing it to international trends. A recommendation is made for a more coordinated monitoring programme at Koeberg in order to obtain maximum benefits in the long term. Notwithstanding, the research has led to the conclusion that Koeberg is achieving the desired results compared to industry performances for plants that are in the same phase of their respective zinc injection programmes.