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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BWR Decommissioning General Information and Experiences

(LCC13 AR)

Many BWR nuclear power plants have begun decommissioning activities recently after a period of 30 to 40 years, with the final goal of obtaining license termination and getting the property released based on the regulator’s decommissioning regulations and guidelines. The power plants use a variety of strategies for dismantling systems, structures, and components, waste management, and deciding on the future use of the site. Typical activities include safely decommissioning of the plant, minimising radioactive waste generation, fuel removal and storage, license termination and getting the site restored and released. In the US, it is expected that decommissioning will be completed within a period of 60 years.

During decommissioning, plant sites typically use one of three approaches, Immediate Dismantling (DCON), Safe Enclosure (SAFSTOR) or Entombment (ENTOMB). Each approach has its benefits and disadvantages although most plants have used the SAFSTOR approach. The report summarises the publicly available BWR decommissioning general information and experiences with salient features and practices employed in the decommissioning activity including potential costs involved.

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

(LCC12)

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.

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Key Issues in Plant Chemistry and Corrosion in BWRs – 2016

(LCC12)

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 summarizes the BWR related papers from the conference and is designed to provide updated information with the author’s critique and analysis for the benefit of the ANT International/LCC customers. The Report is expected to be a compre­hensive document summarising the latest information on BWR water chemistry that would benefit the BWR operators and regulators.

The second report covers PWRs, VVERs, CANDUs, PHWRs and auxiliary systems issues.

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LCC1 Annual Report

The Report covers the following topics:

  • Coolant Quality and Control Issues – PWR Water Chemistry – BWR water chemistry
  • Materials selection for the primary BWR and PWR circuits
  • Primary Circuit Corrosion (BWRs and PWRs) – SCC, PWSCC in PWRs – SCC in BWRs and remedies (HWC, NMCA)
  • Dose Rate Buildup and Control
  • Fuel/Water Chemistry Interaction

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LCC2 Annual Report

The Report covers the following topics:

  • Coolant Quality and Control Issues – PWR/VVER Water Chemistry – BWR water chemistry
  • Structural Materials Degradation
  • Primary Circuit Corrosion (BWRs and PWRs) – SCC, PWSCC in PWRs – SCC in BWRs and remedies (HWC, NMCA)
  • Dose Rate Buildup and Control (BWRs and PWRs)

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LCC4 Annual Report

The Report covers the following topics:

  • Nuclear plant primary water chemistry experience (PWR, VVER and BWR)
  • Water chemistry sampling and monitoring (PWR, VVER and BWR)
  • Corrosion product control and sampling technique (secondary side, PWR, VVER)
  • Material degradation management
  • Fuel /water chemistry interaction
  • Behaviour of radiolysis gases in BWRs and PWRs

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