ISOE Expert Group on Water Chemistry and Source-term Management (EGWC)

Background

Information System on Occupational Exposure (ISOE) provides a forum for radiation protection professionals from nuclear electricity utilities and national regulatory authorities worldwide to share dose management information and operational experience to improve the optimisation of worker radiological protection at nuclear power plants. The ISOE programme, with its participating utilities and regulatory authorities, is a key organisation in developing safe, sustainable and socially acceptable strategies for emerging issues in the field of occupational radiological protection (RP).

There are many approaches to water chemistry in pressurised water reactors (PWRs) and boiling water reactors (BWRs) with very various results and consequences in terms of RP performance. During an ISOE management board meeting, it was decided that the RP aspects of primary system water chemistry and source-term management should be discussed by an ISOE ad-hoc expert group. The group could address the experience of various ISOE utilities with various water chemistry regimes to see if experience exchange could help to improve radiological protection performance. Members of the management board also noted that water chemistry should not only be viewed only from the context of radiation protection issues, but also from the context of operational and safety issues. It was proposed to group a few of the most commonly used water chemistry approaches (e.g. zinc injection, pH control, iron injection, hydrogen water chemistry, etc.) to focus on discussions to compare and exchange experiences. For each approach, it was expected to identify how RP benefits were evaluated with a focus on measurement techniques such as CZT gamma spectroscopy, etc.

Objective of the Group

The objective of the EGWC was to develop a report on radiation protection aspects of primary water chemistry and source-term management, in order to reflect the current state of knowledge, technology and experience on radiation protection issues directly related with radiation protection.

Under the Working Group on Data Analysis (WGDA), the EGWC undertook a review and analysis of current knowledge, technology and experience, and produced a summary report.  The outcome of the work was a new ISOE report on RP aspects of primary water chemistry and source-term management that would find broad use within the NPP radiation protection community. The EGWC undertook this work by:

Planned work of the Expert Group

The expert group discussed the following topics:

Paarticular attention was be given to the collaboration between the different actors involved in the management of source term: operation, chemistry and radiation protection.

Prevention of contamination

It was expected from utilities representatives participating to the EGWC to provide a description of the way they managed their source term so as to prevent (limit) contamination of the primary coolant (pH, Zn injection, steam generator materials, radio-chemical spec. for operation, etc.) and the driving factors that lead to their current approach (cost, radiation protection, safety, etc.). These elements were debated and discussed within the expert group.

Supporting documents such as operational guidelines and procedures (spec., etc.) were welcome. Benefits as well as drawbacks of the different strategies were identified.

Remediation

If a contamination (general or localised) was observed, what techniques weree used, what procedures were followed so as to move back to normal conditions? What indicators were used to identify a contamination that had to be dealt with?

Performance indicators

Various measurement techniques (for instance CZT gamma spectroscopy measurement devices) and indicators (dose rate at some key points in the reactor building, collective dose, etc.) may have been used to assess results of prevention strategies or remediation actions over time. It was expected to have overview of these key elements within this topic.

Final report of the Group

Radiation Protection Aspects of Primary Water Chemistry and Source-term Management Report
OECD, 2014

Last reviewed: 28 July 2014