DS525 - Chemistry Programme for Water Cooled Nuclear Power Plants

The current version of SSG-13 was published in January 2011. Since then, a significant amount of additional operating experience in Member States has been gained, the Fukushima-Daiichi NPP accident has occurred, and the nuclear industry has identified new challenges in the plant chemistry area.  These findings represent opportunities to improve the safety and reliability of NPPs as well as to update the existing Safety Guide on the chemistry programme for water cooled NPPs.

Therefore, it is necessary to revise the Safety Guide so that it reflects the current understanding of the expectations set for chemistry and radiochemistry programmes. The proposed revision of the Specific Safety Guide will:

• Address new practices and technologies in the preservation of plant systems during extended outages, delayed construction programmes or modernisation projects for long term operation;
• Revise the guidance related to the quality control of chemistry parameter measurements and data;
•  Include guidance to validate software tools used in chemistry and radiochemistry laboratories (such as the calculation of the рН value at operating temperature (pHT), and calculations used to evaluate chemical conditions in flow restricted areas like between tube and tube sheet in steam generators, etc.);
• Update the current guidance for post-accident sampling systems and necessary chemistry measurements;
• Balance the current details of chemistry programmes given for various types of water cooled NPPs;
• Increase the level of detailed guidance for chemistry control of auxiliary systems;
• Align SSG-13 with other relevant, recently revised Safety Standards and remove duplication of contents if necessary;
• Incorporate feedback from the users of SSG-13.

The objective of the revised SSG-13 is to provide Member States with updated and, in some areas, more detailed guidance for the safe operation of water-cooled nuclear power plants based on current international best practices in the chemistry area. The updated document will provide recommendations which mitigate degradation of SSCs, improve quality control of chemistry laboratory activities, and contribute to maintaining radiation doses as low as reasonably achievable. The revised publication will also update the current practices of chemistry measurements during accidents and the current expectations of post-accident sampling systems.