Formation of deposits on Pressurised Water Reactor (PWR) fuel cladding has been an inherent problem in these systems since their inception and remains a problem to-date. The report provides: 1) a brief history of fuel crud in PWR systems, 2) mechanisms for material release, transport and deposition in the core and the influence by material choice, coolant chemistry and core design 3) discussions of what occurs within fuel crud that may affect its deposition rate, its effect on core neutronics and possible impact on clad corrosion leading to failure. Finally, a discussion is given summarizing our current understanding and where future work is required to further this knowledge.
Corrosion Product Generation, Activity Transport and Dose Rate Mitigation in Water Cooled Nuclear Reactors
This report discusses in detail, the steps involved in, generation of corrosion products including colloid formation, activation on fuel, transport through the coolant, deposition on surfaces including zeta potential effects, release from surfaces and removal of activated corrosion products in light water reactors. The report also discusses activity transport that will include basic steps involved and models used.
This updated report reviews, as of 2020, the laboratory and field results of zinc injection technology in PWR plants worldwide. The review covers the range from basic information to current knowledge and understanding of operational behaviour. This information on PWR plants given in this report is also applicable for VVER plants.
Historical Evolution of Coolant Chemistry for PWR/VVER Plants: 1960 to Present; Including Basis of the Guidelines
This report describes the historical development of the water chemistry in primary side of the PWR and VVER plants since 1950s up to present. Starting with the first research PWR plants in USA without applying any water chemistry addition of neither alkaline reagent nor hydrogen, lot of fuel performance degradations were experienced in 1950s and 1960s, such as heavy fuel deposits, flow restrictions across the core, reactivity losses and high radiation fields. Even the first AOA indications were experienced in a PWR with low core duty operating without applying water chemistry treatment.
Historical and Present Issues on Secondary System Chemical Treatment and Corrosion in PWR/VVER Units; including Materials Behaviour
This report describes and explains the past and present issues related to secondary system chemistry and materials behaviour.
It starts with the relation between design and material evolution influence on chemistry selection, as well as guidelines for the secondary system. It also explains the behaviour of added reagents and of impurities in the secondary system. The integrity and long-term behaviour of the plant is largely considered.
This first report on PWRs, VVERs, CANDUs and PHWRs summarises and analyses the results to assess in which specific situation the results are applicable and gives the point of view of A.N.T. International expert. Instead of giving a short summary of each paper presented at the conference, the report covers the key facts, either new or of significant interest for LCC customers.
This is of particular interest to discuss how to consider different presentations that may sometimes give contradictory or conflicting results.
The main examples concern zinc addition into the primary coolant, potential replacement of LiOH by KOH in PWRs as used in VVERS, Film Forming Amines, dispersant addition, hydrazine alternates. The advantages, disadvantages, questions or limitations of new solutions are explained.
The second report summarising the BWR related papers and various other subjects is designed to provide updated information with the author’s critique and analysis for the benefit of the LCC customers. The report is expected to be a comprehensive summary document incorporating the latest information on BWR water chemistry and decommissioning that would benefit the operators and regulators, and those who have not been able to attend the NPC 2018 Conference.
This report presents a new corrosion inhibitor based on film forming amines (FFA), which are often referred to as fatty amines or polyamines. FFA can form a mono-molecular hydrophobic film or layer adsorbed on the metal surfaces, that constitutes a homogeneous protective barrier against corrosion by its water-repellent behaviour. FFA belongs to chemical substances of the class of oligo alkylamino fatty amines, the simplest one being the well-known Octadecylamine (ODA). Due to the volatility of the film forming amine, the whole steam water cycle can be protected. The high affinity to surfaces can lead to a slow removal of surface deposits such as loose magnetite and impurities. FFA’s are successfully used as water treatment additives for several decades, in steam water cycles of the VVER type in Eastern Germany and Russia with positive treatment results.
For several years, AREVA has very successfully applied this treatment using a specific procedure in several PWR plants. The purposes are to control the corrosion product transport into steam generators during power operation and for long time lay-up of whole steam water cycle without using hydrazine. Even in a BWR plant this FFA treatment was applied in several parts of steam water cycle with success. This report explains the mechanism of the FFA chemistry treatment and summarises the published information regarding the application results achieved in western nuclear plants.
PWR chemists may claim that there is no oxygen in the Reactor Cooling System because hydrogen injection suppresses the oxidising species generated by radiolysis. This is why, at EDF, the RCS has no oxygen monitoring. In fact, this assessment is true only if free flowing conditions are considered. The RCS contains many flow-restricted or occluded zones where some chemistry deviations can occur, one being the presence of oxygen.
This report aims to keep the plant chemists alert regarding oxygen tracking, ingress, venting, scavenging, monitoring. It also shows some examples of field failures that occurred because oxygen presence was not anticipated in the environment. This report helps plant engineers understand why they should stay alert regarding oxygen control. The report shows there are several ways to limit oxygen ingress or to scavenge oxygen in the RCS. The oxygen specification may seem stringent, however the failures presented in this report support a non-deviation application of the RCS oxygen specification.
The U.S. requirements for a Strategic Water Chemistry Plan, despite the additional work for plants, has been a benefit to U.S. nuclear utilities. The reasons for this are that it requires plants to consider the balance of plant components and their chemistry considerations to the overall integrity of the steam generator integrity, primary system pressure boundary and the fuel cladding integrity. This not to imply that either U.S. utilities or non-U.S. utilities would not consider these issues in developing their own water chemistry plans. However, these voluntary commitments by the U.S. nuclear utilities has probably reduced the regulatory requirements imposed by the NRC, although this is not known for certain.
This document explains the Objective and Optimisation Methodology of this Strategic Water Chemistry Plan. For the Primary Coolant, it includes the Parameters Impacting or not the Pressure Boundary or Fuel Cladding Integrity. For the Secondary System, it includes the key elements and the components susceptibility and reliability. The report is of benefit to those non-U.S. utilities in developing their own water chemistry programs, both primary and secondary side.