OTHER TOPICS

COOLANT CHEMISTRY & CORROSION

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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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.

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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.

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PWR/VVER Primary Side Coolant Chemistry, Volume I – Technical Basis and Recent Discussions

(LCC7 STR)
This report is the first volume out of two focusing on PWR/VVER chemistry. This document is intended to provide a detailed description of the PWR/VVER Primary Side Coolant Chemistry. Furthermore, it should provide a strong support to the utilities for establishing a responsive plant specific chemistry program. It may also help the Manufacturers and Regulators at having a detailed approach of primary water chemistry and corresponding issues.

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PWR and VVER Secondary System Water Chemistry

Adequate secondary side water chemistry is crucial for safe and economical PWR and VVER plant operation. A good practised water chemistry control avoids degradation problems of the key components, sucj as steam generators (SG), carbon steeel components and turbine. The PWR and VVER Secondary System Water Chemistry Report gives a complete overview of the various rationale approaches to optimize the water chemistry according to the design and materials as well as the specific situation of each Nuclear Power Plant.

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Operational Issues and Practices in PWRs

Operational Issues and Practices are important issues for plant personnel. These issues may require optimization or an exchange of knowledge to improve plant operation in a safe, economical, environmentally sustainable way. This report combines the following topics of potentially important consequences:

  • Total Organic Carbon (TOC) in primary and secondary system water
  • Best practices for corrosion products removal in reactor coolant systems (RCS) of VVERs and the use of mechanical filters or macroporous resins
  • Best practices for the use of Ion Exchange Resins for RCS, SG blowdown, and the spent fuel pool
  • Best practices to mitigate condenser leakages and recommendations for Operation procedures in case of large impurities ingress
  • The Use of Dispersant to Mitigate Steam Generator Corrosion Product Deposition In addition to the help for utilities, this report may be of interest for manufacturers and regulators in understanding some plant issues.

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LCC9 AR: Operational Issues, Practices and Remedies

Operational Issues, Practices and Remedies are important issues for plant personnel and designers. This report combines the following subjects of limited extent but potentially important consequences:

  • Degradation of the primary coolant barrier together with mechanical remedies.
  • The potential benefits of Enriched Boric Acid (EBA).
  • Primary coolant (Co-58, colloids) inventory.
  • Degradation of concrete structures in NPPs.
  • Colloids, Zeta Potential and Activity Transport.
  • Electrochemical Corrosion Potential (ECP) measurements.
  • Key points, ”lessons learned” and ”best practices” of several recent conferences.

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