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

(LCC11 STR)
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.

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Key Emerging Issues and Recent Progress Related to Plant Chemistry/Corrosion inPWR/VVER/CANDU reactors

(LCC10 AR)
Key Emerging Issues and Recent Progress Related to Plant Chemistry/Corrosion in PWR/VVER/CANDU Reactors (LCC10 AR)

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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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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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CRUD in PWR/VVER Coolant. Volume I – Sources, Transportation in Coolant, Fuel Deposition and Radiation Build-Up

Crud in PWR/VVER Coolant. Volume I – Sources, Transportation in Coolant, Fuel Deposition and Radiation Build-up (LCC10 STR) The topic is covered in two separate volumes. Volume I which is provided within the LCC10 Programme, and Volume II which will be provided in the LCC11 Programme. This document, Volume I covers the following topics:

• Introduction
• Sources of CRUD
• CRUD Transportation in PWR/VVER Coolant
• Crud Deposition in the Core
• Crud Release from Core and Radiation Build-up Mechanism
• Summary Volume II will contain information on Control of CRUD in the PWR/VVER Coolant and Mitigation Tools

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Key Emerging Issues and Recent Progress Related to Plant Chemistry/Corrosion

(LCC8)
The report covers the impact of manufacturing on microstructure and in-reactor performance of Zr-Nb alloys. The report was co-authored by Russian scientists involved in the development of the Russian Alloys E110, E635 and E125.

1. The EPRI Steam Generator Secondary Side Management Conference covering:

• Deposit generation and transport
• Deposit control and mitigation
• Deposit consolidation and removal
• Short and long term strategic planning

2. BWR issues presented in the EPRI Conference

3. The Nuclear Power Chemistry Conference covering:

• Primary water chemistry including:
• Secondary water chemistry including:
• Auxiliary systems, cooling water systems, water and waste treatment
• Lifetime management and plant ageing
• Maintenance including curative and preventive cleaning methods
• Future trends and new developments

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Incoming Goods, Hazardous Materials and Aging of Plant Chemicals

The objective of this Report is to provide a comprehensive understanding of controlling the quality of incoming goods in Nuclear Power Plants. The Report will help utilities with checking that their Quality Assurance system is appropriate or modifying it. The Report will also be useful for manufacturers at properly implementing manufacturing, protection, shipping, labelling, etc for avoiding degradation that may be discovered at the very beginning of plant operation. Finally, regulators will have a complete view of the possible risks of degradation and how to verify that the Quality Assurance programs are implemented.

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