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View allDecomissioningBWR ChemistryPWR/VVER ChemistryAnnual Reports Presenting Key Results Published During 18 Months
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Key Emerging Issues and Recent Progress Related to Plant Chemistry/Corrosion (PWR, CANDU, and BWR Nuclear Power Plants) (LCC19)

Safety and reliability of power plants are becoming increasingly important factors since many plants are aging and have obtained license renewal for continued power operation and also for new reactors using different technologies that are or will be in design, construction, commissioning, or start-up stage. Therefore, sharing plant operating experiences, sharing lessons learned, and sharing new industry research are all crucial in order to maintain the nuclear power plant fleet in a healthy condition as well as for new reactors using different technologies that are or will be in design, construction, commissioning or start-up stages.

This report on Key Emerging Issues and Recent Progress, ANT International has collected the most relevant experiences and advanced research exposed at the Nuclear Plant Chemistry Conference NPC-2023 that took place in Antibes Juan-les Pins, France in September.

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Deposit Formation on Fuel Cladding in PWR Primary Systems

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.

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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.

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Historical Evolution of Coolant Chemistry for PWR/VVER Plants: 1960 to Present; Including Basis of the Guidelines

(LCC15)

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.

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Historical and Present Issues on Secondary System Chemical Treatment and Corrosion in PWR/VVER Units; including Materials Behaviour

(LCC15)

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.

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Key Issues in Plant Chemistry and Corrosion – PWR, VVER, CANDU – 2018

(LCC14)

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.

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Key Issues in Plant Chemistry and Corrosion in BWRs – 2018

(LCC14)

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.

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Use of Film Forming Amines (FFA) in Nuclear Power Plants for Lay-up and Power Operation

(LCC13 AR)
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.

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The Underestimated Role of the Oxygen on RCS Component Failures

(LCC13 AR)

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.

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