The Importance of Organic Compounds in Evaluating Accident Management Strategies

Abstract

The behaviour of iodine in reactor accidents is a concern because of its radiological importance, and longstanding programmes of continuing research in Canada have brought about radical changes in its understanding. Although iodine remains a potential hazard, past analyses and practices have tended to underestimate the complexity of its behaviour while overestimating its probable radiological impact. The Radioiodine Test Facility (RTP) at Whiteshell Laboratories as well as separate effects tests and fundamental research has identified four factors of significance affecting iodine behaviour: pH, radiation, organic materials and surfaces. Radiation fundamentally alters iodine behaviour, radiolysis of organic materials can form acids which can increase the volatility of iodine, and by maintaining the sump water at a high pH, iodine volatility can be minimised. This latter finding has significance for accident management strategies. However, the detailed chemical reactions involved are not well understood, and it may be difficult to retrofit pH control into existing systems. Therefore it is important to understand the chemistry and to evaluate alternative strategies. This paper focuses on aqueous iodine chemistry in the presence of radiation and typical organic materials and suggests alternative mitigation strategies.