MTA-EN-002

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Administrative Items
Date	12/15/2020
Functional Area Where Benefits Will Be Realized	Engineering Maintenance
Reference Implementation Guidance	Plant Modernization Business Case: Monitoring Heat Exchanger Shells (EPRI 3002018481) Nondestructive Evaluation: Structural Health Monitoring for Heat Exchanger Shells (EPRI 1016413) State of Structural Health Monitoring Technologies for Nuclear Applications (EPRI 3002010448) Technology and Process Improvement Readiness and Proposed Measurement Method for Nuclear Plant Modernization (EPRI 3002015802)
Industry SME	EPRI Nondestructive Evaluation Program Contact: NuclearPlantMod@epri.com
Previous Implementation	Please contact EPRI for implementation examples and contacts.
Implementation Enablers	MTA-MA-003 – Implement a Wireless Network Infrastructure Using a Distributed Antenna System (DAS) MTA-MA-004 – Implement a Wireless Network Infrastructure Using WiFi
Applicability	All reactor types All geographic regions
Keywords	Heat exchangers; flow-accelerated corrosion; structural health monitoring; guided wave sensors; plant modernization
Business Case Analysis Cross-Reference	Plant Modernization Business Case: Monitoring Heat Exchanger Shells (EPRI 3002018481).

Description

The heat exchanger shell is a pressure vessel that surrounds and encloses a tube bundle. The internal side of the shell may be susceptible to corrosion and wear caused by the steam and flow conditions in the heat exchanger. Shell wall thickness data are typically collected using conventional ultrasonic testing (UT) inspection techniques to monitor the shell health and to support the plant’s flow‑accelerated corrosion (FAC) program, but complete coverage of the shell is impossible due to obstructions (e.g., pipes and fittings) and time constraints. This nondestructive evaluation (NDE) inspection typically involves gridding the component and manually taking measurements at the grid intersections with a transducer or probe; sometimes, manual scanning within the grids is required to properly characterize the extent of wall loss. These inspections require surface preparation for the inspection technology. In addition, these inspections often require insulation to be removed prior to inspection and reinstalled before returning to operation.

This MTA focuses on the use of permanently installed guided wave ultrasonic sensors to provide continuous monitoring of the shell condition. The technology introduces guided waves throughout the entire heat exchanger shell, providing increased support of the FAC program and extending the interval of NDE inspections. Permanently installing sensors and conducting Structural Health Monitoring (SHM) can reduce the costs associated with NDE inspections but is not intended to replace UT wall‑thickness inspections entirely.

The scope of this MTA only includes non‑safety‑related heat exchangers, for consistency with the associated Plant Modernization Business Case (EPRI 3002018481).

Benefits

Benefits Estimate

Level 1 – Potential savings are achieved through a reduction in periodic inspections and are expected to be less than $1 million per year. Manual inspections may be on the order of 3 to 10 years. Average net savings are approximately $25,000 per year based on previous implementations.

Benefits Description

• Labor savings associated with conducting fewer manual inspections due to transition from a time‑based to a condition‑based inspection approach. SHM enables data to be acquired at any desired time interval without the need to access the component or prepare it for inspection.
• Contract savings from reduced need for scaffolding to perform inspections.
• Reduced costs associated with extended NDE inspection intervals related to surface preparation and insulation removal/reinstallation.
• Reduced dose exposure associated with extended NDE inspection intervals related to surface preparation and insulation removal/reinstallation.
• Improved understanding of component health from using permanently installed guided wave technology. The shell condition can be monitored while in operation, leading to additional inspection insights on wear rates and wear patterns while online and during any system changes.

Costs and Schedule

Cost

Level 3 – Total costs of sensors, nondestructive evaluation (NDE) related equipment, personnel time for the installation, and dose accumulated during installation are expected to be less than $1 million per installation. Implementation costs are approximately $150,000 per unit.

Schedule

One to three years, which includes planning and implementation. SHM implementation on heat exchangers can be incorporated with a phased approach (i.e., not all heat exchangers need to be implemented in the same outage).

Scope Context

Per unit. The number of heat‑exchanger SHM candidates varies per unit, but historically there have been 4 – 6 candidates per unit.

Risks

Potential personnel risk – The ability of guided wave technology to identify localized thinning or defects is not fully developed. At this time, guided wave technology is not intended to replace ultrasonic thickness testing but can be used to inform the need for ultrasonic inspections, potentially increasing inspection intervals and decreasing scope. Active research is being performed to validate guided wave technology’s ability to identify defects.

IT risks associated with integrating with existing plant network, data storage, and analysis software. Addressing IT concerns at the requirements phase of the project (for example, how the sensor data will be gathered and used) will mitigate this risk.

Sensors may be affected by temperature and radiation effects. Sensors can survive at least 3 years in service at 350 °F. Active research is being performed to understand further temperature and radiation effects on SHM sensors in heat exchangers.

SWEEP Score

Category	Level	Description
Cost	3	Implementation costs associated with sensors should be less than $1 million.
Savings	1	Savings for one unit are expected to be less than $1 million per year.
Payback	1	Typical inspection frequencies are in excess of five years; therefore, return on investment will also be greater than five years.
Licensing Readiness	3	Heat exchangers considered for implementation are not safety-related. Therefore, no licensing requirements apply.
Technology Readiness	2	Guided wave technology has been used in other industries and applications. The technology has been piloted with some success in heat exchanger shells. EPRI is engaged in follow‑on research to refine the state of the technology and knowledge.
Implementation Proficiency	2	Implementation depends on experience related to wireless data infrastructure, wireless data transmission for maintenance and monitoring, cyber‑security protocols, etc.