Chemistry, Low Level Waste and Radiation Management January 2016

ISSUE STATEMENT

Deposition of corrosion products on primary and secondary side heat transfer surfaces (e.g., fouling of steam generator (SG) tubes, fuel rods, heat exchanger surfaces) decreases heat-transfer efficiency and increases the susceptibility to (and likelihood of) corrosion degradation. Field activities to mitigate the effects of fouling lead to worker dose. Fouling leads to a reduction in power generation, costly maintenance activities to mitigate the problem, or even to replacement of the affected component. Such activities can result in indus-try-wide costs of tens of billions of dollars. Chemistry tech-nologies are needed to provide an effective means of mark-edly reducing fouling, and thereby prevent or significantly mitigate the consequences resulting from such fouling.

DRIVERS

Asset ProtectionCorrosion processes are greatly exacerbated by the detrimetal chemistry that develops in occluded geometries formed by deposits. Minimizing the formation of these occluded geom-etries by reducing corrosion product fouling decreases the likelihood of having to perform costly repairs or even replace the component.

OperationalBy minimizing the amount of corrosion products formed on heat transfer surfaces (e.g., by reducing deposition and/or removing existing deposits), the plant can maximize power output and overall plant availability.

EconomicMaintenance activities are a normal part of trying to ensure safe operation and maintain plant availability, but these activities can be costly. The application of chemistry tech-nologies to reduce corrosion product fouling may provide the mechanism by which maintenance scope or frequency can be safely reduced.

Worker DoseOverall reduction of corrosion product fouling will reduce needed worker activities, resulting in less radiation exposure in the field (supporting the goal of the Big RP initiative). For example, reducing the scope of secondary side steam genera-tor cleaning activities will result in less worker dose. Chem-istry technologies to reduce deposit accumulation or remove

existing deposits (i.e., from fuel via chemical enhancement of ultrasonic fuel cleaning) can positively impact this issue and help reduce worker dose.

RESULTS IMPLEMENTATION

The work pursued through this roadmap will result in guid-ance and tools in the form of dispersant application sourcebooks:• PWR Secondary Chemistry Dispersant Application

Sourcebook (Revision 2, 2020) – Expanded experience base with updated guidance and lessons learned

– Pre-application preparations for new applications, optimization for continuing applications

• BWR/PWR Ultrasonic Fuel Cleaning Dispersant Application Sourcebook (2021)

– Chemical enhancement for deposit removal to reduce CILC and CIPS susceptibility

• BWR/PWR Primary or Auxiliary Chemistry Dispersant Application Sourcebook (2021)

– Effects on radiation fields (in collaboration with Source Term efforts)

– Effects on heat transfer efficiency (e.g., heat exchangers, SGs)

• PWR Secondary Chemistry Filming Amine Application Sourcebook (2022)

– Safe application of a filming amine to reduce general corrosion and corrosion product release

Nuclear plants will use these sourcebooks to develop and maintain corporate and site procedures or documents for the mitigation of corrosion product fouling. EPRI offers sup-port, as needed, to assist utilities with implementation.

PROJECT PLAN

Dispersant on-line application for mitigation of secondary side steam generator fouling is the most mature of the con-sidered technologies. A significant body of work to qualify, field test and implement dispersant application for the PWR secondary sysem has been developed and will be leveraged to support the entire project plan. Filming amines is garnering more interest in the nuclear industry, but still requires qualification.

IN USE: CHEMISTRY TECHNOLOGIES FOR THE MITIGATION OF CORROSION PRODUCT FOULING

EPRI | Nuclear Sector Roadmaps January 2016

PWR Secondary System

Iron Monitoring

Assessment of iron transport is a key input to determining needed mitigation efforts in support of good steam generator health. Measurement of feedwater iron, on a continuous basis, is critical to this assessment (and blowdown iron if blowdown removal efficiency is significant). Manual efforts to obtain iron concentrations are labor intensive, and can lead to delays in analyzing the sample. Novel techniques to quantify or trend iron concentrations should be evaluated and, if appropriate, field tested in order to provide an online technique to appropriately reduce needed labor and provide more timely results.

Dispersant

There are three distinct applications of dispersant technology:• On-line injection during power operation to markedly

enhance SG blowdown iron removal. Benefit to SG ther-mal performance has also been demonstrated.

• Startup, during the long-path recirculation cleanup pro-cess (before feeding the SGs) to minimize iron transport to the SGs.

• SG wet layup to enable limited additional removal of existing deposits, and increase removal of hardness ele-ments (e.g., calcium and magnesium).

EPRI is continuing to evaluate field experience to assess the longer-term effects of dispersant application on plant opera-tions, and to assess novel applications such as targeted injec-tion at the end of the operating cycle. State-of-the-art guid-ance and recommendations will be consolidated in the revision of the PWR Secondary Chemistry Dispersant Application Sourcebook.

Filming Amines

Filming amines (poly amines and similar compounds) have been applied intermittently in the fossil industry for over 25 years, as a means of protecting carbon and low alloy steel components from general corrosion, especially during peri-ods of long layup. Filming amines also have been used on-line to prevent general corrosion, reduce fouling and miti-gate flow accelerated corrosion (FAC). EPRI has sponsored a number of projects related to use of filming amines for fossil plants since 2000, and continue to do work in this area. More recently, a filming amine has been applied at the end of two – three cycles of operation at the Almaraz PWR units in Spain1, 2. A favorable reduction in feedwater iron concen-tration after application of the filming amine has been reported. Nevertheless, details of the application procedure

1 EPRI Steam Generator Secondary Side Management Conference, September 2014.2 EPRI SGMP European Workshop, October 2015.

or qualification work has not been shared to date. The objec-tive of this work is to develop and qualify filming amines for safe and effective application in nuclear plant systems, in an analogous fashion to the way dispersant was qualified for PWRs.

BWR and PWR Primary or Auxiliary SystemBased on the demonstrated effectiveness of dispersant in the PWR secondary system, dispersant application in the reac-tor coolant could significantly enhance shutdown cleanup, corrosion product removal for improved heat transfer (e.g., heat exchangers, SGs) and reduce plant dose rates. In addi-tion, chemically enhanced fuel deposit removal during ultra-sonic fuel cleaning can mitigate crudding risk, CIPS (Crud-Induced Power Shift) and CILC (Crud-Induced Localized Corrosion).

EPRI will identify key components and/or target locations where dispersant application will likely have the greatest benefit. Feasibility evaluations will assess the requirements for a successful application and identify remaining qualifica-tion work needed. Upon qualification, a lead plant will implement an EPRI-developed trial application. Application guidance will be provided in a Sourcebook. As appropriate, application of a filming amine could be envisioned as well, if qualification efforts and efficacy evaluations demonstrate success.

RISKS

External Stakeholder EndorsementTechnical review and concurrence from external stakehold-ers is needed; namely, NSSS, fuel, turbine, and chemical vendors. In addition, proprietary interests may impede tech-nology development for filming amines. There is only one supplier of high purity polyacrylic acid (PAA). These stake-holders are engaged, or are becoming engaged, in this work.

Technical RiskQualification or efficacy testing may not prove successful for filming amines. For dispersant, the effect of long-term expo-sure on materials and resins are unknown and may impact continual use. Primary system application may also be affected by impacts on fuel. The benefits in primary systems may be reduced or negated due to chemical decomposition from radiation fields.

Technology Implementation ConstraintApplications of new chemistry technologies will require a lead plant to implement. Competing priorities with work groups outside of chemistry, for example fuels, materials, radiation protection and shutdown/outage planning, may add complexity to implementation.

Chemistry, Low Level Waste and Radiation Management January 2016

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: Keith Fruzzetti

1 Revision Issued: December 2011 Roadmap Owner: Keith Fruzzetti

Changes: Modified the language to more clearly state that the Worker Dose Driver is with respect to a reduction in field cleaning activities/scope, and that this reduction will result in less worker dose. Updated flowchart (project timeline) to address funded/unfunded project differences.

2 Revision Issued: August 2012 Roadmap Owner: Keith Fruzzetti

Changes: Modified and updated descriptions, especially for PWR secondary side application and experience. Updated flowchart (project timeline) to add qualification of additional dispersants for startup application on PWR secondary side, and modify schedule and funded/unfunded projects.

3 Revision Issued: December 2012 Roadmap Owner: Keith Fruzzetti

Changes: Updated project plan related to experience for PWR secondary side online application. Minor modification to clarify technical risks. Updated flowchart (project timeline) based on work completed in 2012 and to be performed in 2013.

4 Revision Issued: August 2013 Roadmap Owner: Keith Fruzzetti

Changes: Edited project plan to update information on PWR secondary system plant experience. Update to flowchart based on work activities and funded/unfunded projects.

revision description of change

5 Revision Issued: December 2013 Roadmap Owner: Keith Fruzzetti

Changes: Reflected new information in the text and flowchart based on discussions from the August 2013 dispersant workshop, and project prioritization activities. Minor editorial changes also incorporated.

6 Revision Issued: December 2014 Roadmap Owner: Keith Fruzzetti

Changes: Added scope to include filming amines. Re-titled to better reflect the issue being addressed. Updated information on projects and schedule.

7 Revision Issued: December 2015 Roadmap Owner: Keith Fruzzetti Utility Support: Michael Brett, Kevin Burroughs, Iain Duncanson, Jeff Goldstein, Larry Miller

Changes: Added scope to include iron monitoring. Updated writeup, and information on projects and schedule.

EPRI | Nuclear Sector Roadmaps January 2016