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.


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


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.


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.


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.


Strategic Plans for Primary and Secondary Water Chemistry Programmes

(LCC13 AR)

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.


Key Emerging Issues and Recent Progress Related to Plant Chemistry/Corrosion (PWRs, VVERs, CANDUs, PHWRs, and Auxiliary Systems)


The 20th Nuclear Plant Chemistry (NPC) International Conference, which started in Bournemouth (UK) and held every other year, was held in Brighton (UK) in October 2016. It is the most im­portant conference related to chemistry in Nuclear Power Plants, and covers many new results in this area. The key information presented at this Conference is covered in two separate LCC12 Reports.

This Report does not only covers PWRs, VVERs, CANDUs, PHWRs and auxiliary systems issues but also summarizes and analyses the results to assess in which specific situation the results are applicable and give the point of view of experts of ANT International that atended the Conference.

The second report covers BWRs and Fukushima response.


CRUD in PWR/VVER Coolant Volume II – Control of CRUD in the PWR/VVER Coolant and Mitigation Tools

All materials used in nuclear power plants, as bare material (steels and alloys), are not stable in the reactor water and dissolve by corrosion. They are protected by passive oxide layers formed by the corrosion attack of the water to the metal surface under operating conditions. However, to some small extent these oxide layers dissolve in the reactor coolant and are transported as corrosion products (called also CRUD) to the reactor core. There they deposit on the fuel assemblies and are activated. The deposition of the crud on fuel assemblies and their release to the coolant highly influences the core and plant performance with respect to fuel cladding integrity and radiation fields.

The purpose of the Volume II of this Report, in LCC11, is to describe the tools and their application to adequately control the coolant crud in order to improve the fuel and out-core radiation performance. This information can support the plant chemists to establish strategies of applying the mitigating tools for crud control to achieve their plant specific goals. The information given in this Report is also valuable for fuel vendors and plant fuel engineers to evaluate the possible ways of improving the fuel performance. In a similar way, this information helps the Regulators at properly examining the relative importance of various CRUD Control Mitigating Tools to ensuring an improved fuel performance for safe operation. 
The associated Volume I containing: Mechanism of Sources, Transportation in Coolant, Fuel Deposition and Radiation Build-up, was published within the LCC10 Programme.


Start-Up and Shutdown Practices in BWRs as well as in Primary and Secondary Circuits of PWRs, VVERs and CANDUs

The objective of this Report is to provide a good understanding of the special problems and appropriate good practices during shutdown as well as during startup of LWRs. The Report provides a worldwide review of Startup and Shutdown Procedures both in the Primary and in the Secondary Circuit of PWRs, CANDUs and VVERs, and in the reactor coolant and main steam containing systems of BWRs.