in use: mitigation of boiling water reactor...

Materials Degradation and Aging August 2016

IN USE: MITIGATION OF BOILING WATER REACTOR MATERIALS DEGRADATION

ISSUE STATEMENT

The goal of the mitigation R&D activity is to evaluate, develop, demonstrate and implement effective technologies to mitigate material degradation in BWRs. Mitigation issue management gaps are associated with R&D needs in the area of new technology development or assessment of miti-gation effectiveness to prevent initiation or limit progression of degradation.

The overall objective of Boiling Water Reactor Vessels Inter-nal Program (BWRVIP) mitigation activities is to optimize the water chemistry to achieve a proper balance of benefit from implementation versus negative consequences to the plant and to show that the mitigation technologies are effec-tive through appropriate monitoring.

DRIVERS

Asset ManagementAsset management is the primary driver associated with the mitigation tasks. Mitigation technology improvements, development of new mitigation methods, and qualification of surface mitigation techniques could reduce operating costs while maintaining adequate material integrity by investigating the technical basis for longer inspection inter-vals and fewer repair activities.

Regulatory and Industry CommitmentsThis work supports industry commitments through efforts such as the NEI 03-08 Materials Initiative. Implementation of projects within these tasks, such as Inspection Relief and Water Chemistry Guidelines, supports regulatory require-ments. Mitigation issues are applicable to the entire BWR fleet.

RESULTS IMPLEMENTATION

Guidance documents, models and plant demonstrations being developed under this program will be incorporated into industry guidance for managing materials degradation in BWRs through the plant’s licensed operating period.

PROJECT PLAN

The following major tasks will be performed within this pro-gram to support the asset management goals of BWR utilities:• BWR Water Chemistry Guidelines – this industry doc-

ument is utilized by the entire U.S. BWR fleet. The docu-ment is reviewed annually and revised every four years. It is prepared by a committee of utility personnel, nuclear steam supply system and fuel vendors, Institute of Nuclear Power Operations (INPO), consultants and EPRI staff.

• BWR Vessel and Internals Assessment (BWRVIA) Radiolysis and Electrochemical Potential (ECP) Model – this computer code calculates the necessary amount of hydrogen required for intergranular stress cor-rosion cracking (IGSCC) migration of reactor and pri-mary piping components.

• ECP Monitoring Sourcebook – this guidance document will provide detailed information on electrochemical cor-rosion potential (ECP) monitoring including recom-mended types of monitoring probes, monitoring locations and data analysis.

• Startup ECP Reduction Technology Development and Demonstration – this project is developing the tech-nology needed for early hydrogen addition in a BWR dur-ing plant startup. The first plant demonstration has been performed and the results of the application and associ-ated monitoring were reported to the industry. As this technology begins to be applied to throughout the fleet, guidance and optimization methods will be developed. New work is in progress to assess the injection of metha-nol for early hydrogen implementation.

• Effect of Chemistry Transient on Crack Growth Rates of BWR Materials – this project will evaluate the impact of chemistry transients on crack growth rates of primary system materials under various BWR water chemistries such as hydrogen water chemistry (HWC) and noble metal addition and assess their impact on Action Level limits in the BWR Chemistry Guidelines. The initial work on the effect of chlorides on low alloy steels will be completed in 2016 and the results will be used to revise the Action Level limits in the Guidelines and to revise low alloy steel crack growth reports BWRVIP-60-A and BWRVIP-233 Rv.1. The follow on work will investigate the effect of chemical transients on IASCC of irradiated stainless steels and IGSCC of Ni-base alloys and stainless steels.

EPRI | Nuclear Sector Roadmaps August 2016

• Online NobleChem (OLNC) Deposition Modeling, Durability and Effectiveness Studies – this project will evaluate the noble metal loading on vessel internals and piping at various BWRs and to develop and benchmark a platinum deposition model to calculate loading at various locations within the reactor and primary piping systems. ECP measurements will be conducted in the lower ple-num region in a BWR to confirm the effectiveness of OLNC. The task also includes characteriza tion of plati-num particle size, spacing and distribution and impact on ECP.

• Technical Basis for Inspection Relief for BWR with Hydrogen Injection – this project will revise BWR-VIP-62 to provide guidance for effective implementation of OLNC and to provide the technical basis to optimize inspection intervals for plants implementing OLNC. The document has been submitted to the NRC for a Safety Evaluation and will result in the generation of BWR-VIP-62 Rv.1-A after completion of the NRC review.

• Mitigation Monitoring Focus Group – this industry group will develop technically based monitoring guid-ance to assure confidence in various monitoring methods which may include chemistry measurements of hydrogen and oxidants, ECP monitoring, analysis of platinum deposition on surfaces of plant components, and the use of modeling tools.

RISKS

Possible negative results associated with delay, deferment, or cancellation of project elements include:• Inability to ensure effective mitigation of all applicable

BWR components in all critical locations for the life of the plant using existing mitigation techniques. For exam-ple, currently there are no effective methods to mitigate IGSCC in components in the two phase region above the core e.g., top guide, core spray piping and steam dryer.

• A loss of potential to extend the time until component repairs or replacements is needed. This could occur due to a lack of new technology development for mitigation of components that cannot be currently protected by hydro-gen water chemistry technologies (e.g., Moderate HWC, Noble Metal Chemical Addition, and OLNC).

• Inability to incorporate OLNC into BWRVIP-62-A, potentially impacting implementation of longer inspec-tion intervals for this hydrogen water chemistry based technology.

• Potential for increased cracking or crack re-initiation to occur during startup and/or shutdown periods when hydrogen injection is unavailable.

RECORD OF REVISION

This record of revision will provide a high level summary of the major changes in the document and identify the Road-map Owner.

revision description of change

0 Original Issue: August 2011 Roadmap Owner: Raj Pathania

1 Revision Issued: August 2012 Roadmap Owner: Raj Pathania

Changes: Added Key Milestones to flowchart


Changes: Updated Roadmap content and milestones on flow chart


Changes: Updated roadmap content and milestones on flow chart





Materials Degradation and Aging August 2016

in use: mitigation of boiling water reactor...

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