MTA-MA-015

Administrative Items
Date	12/15/2020
Functional Area Where Benefits Will Be Realized	Maintenance Engineering Chemistry
Reference Implementation Guidance	Steam Generator Management Program: Steam Generator Deposit Removal Strategies Sourcebook (EPRI 3002005090) 2016 NEI TIP Awards – Submittal 25 (ID: 9106343)
Industry SME	EPRI – Brent Capell Contact: NuclearPlantMod@epri.com
Previous Implementation	Please contact EPRI for implementation examples and contacts.
Implementation Enablers	N/A
SWEEP Score	Cost – Level 2 – The process and training on its use is greater than $1 million but less than $5 million. Savings – Level 1 – Savings are less than $1 million per year. Payback – Level 2 – Based upon available cost and savings information, the payback period for implementation is greater than one year but less than five years License readiness – Level 3 – This approach has already been implemented at nuclear power plants. Technology readiness – Level 3 – The technology is commercially available and has been used previously at nuclear power plants. Implementation proficiency – Level 3 – The implementation and operation of the iASCA/CODE process does not require knowledge in implementing digital technologies.
Applicability	Components, systems, and industries with iron, silica, and aluminum based deposits. All geographic regions
Keywords	Steam generator cleaning; equipment reliability; maintenance; scale conditioning; deposit extraction; process chemistry; secondary deposits
Business Case Analysis Cross-Reference	N/A

Description

Steam generators require maintenance to protect from corrosion and other degradation mechanisms in their operating environment. Within a steam generator, localized areas of hardened top of tubesheet (TTS) deposits can accumulate in collars around the tubes. These types of deposits are resistant to removal by typical mechanical cleaning techniques like sludge lancing during maintenance. An alternative is chemical treatment, but because each plant has its own design and history, steam generator chemical cleaning treatments must be tailored specifically for each application.

This MTA describes technologies applicable to remove secondary side deposits and binding species of iron, silica and aluminum found in some TTS deposits. The Inhibited Advanced Scale Conditioning Agent (iASCA) increases the capacity for secondary side deposit removal and is generally applicable to all steam generators. Additionally, the Consolidated Deposit Extraction (CODE) process focuses on cleaning the binding species found in consolidated TTS deposits, specifically iron, silica, and aluminum. The combined iASCA/CODE process is designed to maximize secondary deposit removal of iron, silica and aluminum species that take years to accumulate while reducing personnel dose associated with mechanical cleaning. The iASCA/CODE process is not needed for every outage. Frequency of iASCA/CODE treatment and reduction in the interval for mechanical cleaning is plant specific.

iASCA and CODE, both developed by a US Nuclear utility, are part of a family of application‑specific processes that can be used to optimize deposit removal. Optimization can consider removal from specific locations (tube support plate crevices), the total mass removed, or the structure of the deposits left behind (increasing porosity for enhancement of thermal performance) as well as reductions in the effect on outage planning (schedule, cost, resources, etc.).

Benefits

Benefits Estimate

Level 1 – Savings are expected to be less than $1 million per year. Potential savings are achieved through reduction in sludge lancing cycles, saving ~$1 million every outage where sludge lancing is skipped (extended interval for sludge lancing is plant‑specific). Additional savings (> Level 1) may also come from the cost avoidance associated with the increased reliability of steam generators.

Benefits Description

• Improved cost savings from skipping sludge‑lancing cycles without steam generator degradation concerns – saves ~$1 million per skipped cycle
• Reduction in dose from the capability to skip sludge‑lancing cycles without steam generator degradation concerns – saves ~1.5 rem per skipped cycle
• Increased reliability in steam generators through reduced risk of corrosion‑related failures and structural failures associated with areas of hard secondary side deposits
• Improved cost‑savings associated with the capability to skip additional steam generator maintenance services during an outage – maintenance of secondary side deposits mitigates the risk associated with sludge accumulations that provide an environment for corrosive elements to remain. If the generator is allowed to degrade, additional services (e.g., tube plugging) may need to be performed.
• Improved thermal performance – benefits are unit‑specific and can include both long‑term and short‑term effects.

Costs and Schedule

Cost

Level 2 – The chemicals, process and training are greater than $1 million but less than $5 million per outage.

Schedule

One to three years, which includes planning and implementation of the iASCA/CODE process. Actual usage of the iASCA/CODE cleaning process occurs during the course of an outage.

Scope Context

Per unit/per outage. The context for the combined iASCA/CODE process is based on the first‑of‑a‑kind (FOAK) implementation. The iASCA process on its own has been performed multiple times previously.

Risks

The chemicals used in the iASCA/CODE process are hazardous. If the health & safety risks are not planned and accounted for, then significant cost and schedule impacts are expected to occur. Proper planning for the technologies should begin at least one outage before its use.