MTA-MA-019

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Administrative Items
Date	12/15/2020
Functional Area Where Benefits Will Be Realized	Maintenance
Reference Implementation Guidance	Guidelines for Instrument Calibration Extension/Reduction - Revision 2: Statistical Analysis of Instrument Calibration Data (EPRI 3002002556) US NRC Generic Letter 91-04 Changes in Technical Specification Surveillance Intervals to Accommodate a 24-Month Fuel Cycle Regulatory Guide 1.105 Setpoints for Safety-Related Instrumentation NUREG-0800, Branch Technical Position 7-12, Guidance on Establishing and Maintaining Instrument Setpoints NEI 04-10 Rev. 1 Risk-Informed Technical Specifications Initiative 5b - Risk-Informed Method for Control of Surveillance Frequencies
Industry SME	EPRI – OPI Contact: NuclearPlantMod@epri.com
Previous Implementation	Please contact EPRI for implementation examples and contacts.
Implementation Enablers	N/A
Applicability	All reactor types The available guidance for extending calibration intervals is based on the U.S. NRC regulations.
Keywords	Extend calibration; calibration intervals; instrument drift; historical data; statistical analysis
Business Case Analysis Cross-Reference	N/A

Description

Calibration and surveillance of nuclear plant instrumentation requires substantial resources. Historical calibration data can be used to better characterize instrument drift, which in turn can be used to justify increased calibration intervals and refine instrument uncertainty inputs to setpoint calculations. Per EPRI report 3002002556, instrument drift is the difference between the current as‑found instrument setting and the previous as‑left instrument setting. Statistical analysis is applied to historical data from instrument calibration checks to quantify drift over time by groups of instruments with similar design and performance characteristics, such as a group of transmitters with the same manufacturer make and model used to monitor pressurizer level. Note that instrument calibration and surveillance intervals identified in plant Technical Specifications must be updated through a license amendment request (LAR) to extend calibration intervals. Previous implementations have shown that by applying statistical analysis to historical drift data, instrument calibration intervals can be extended across multiple outages before requiring a calibration check, reducing maintenance costs associated with calibration testing.

Benefits

Benefits Estimate

Level 1 – Savings are less than $1 million per year per unit.

Benefits Description

• Reduction in labor hours because components do not require as frequent calibration (estimated 2,000 man‑hours saved each year per unit).
• Reduction in personnel dose depending on the location of the instruments that receive extension of their calibration intervals.
• Increased equipment reliability because each calibration check carries a potential for equipment damage.

Costs and Schedule

Cost

Level 2 – Implementation cost is between $1 million and $5 million per unit. Costs for additional units may be reduced if drift adjustments can be leveraged for multiple component types.

Schedule

One to three years.

Scope Context

Per unit – cost and schedule estimates include labor associated with:

• Drift evaluations for numerous groups of instruments
• Calculation changes
• License changes
• Work mechanism updates
• Changes to outage schedules and management activities

Risks

No unique risks beyond standard project risks associated with implementing changes at nuclear power plants.

SWEEP Score

Category	Level	Description
Cost	2	Implementation cost is between $1 million and $5 million. Costs for additional units may be reduced if drift calculations can be leveraged for like component types
Savings	1	Savings are less than $1 million per year per unit. Extension of calibration intervals is a one-time implementation cost. Once the license is changed, plants can see significant savings over the lifetime of the facility.
Payback	2	The payback period for implementation is greater than one year but less than five years (inclusive). Extension of calibration intervals is a one-time implementation cost. Once the license is changed, plants can see significant savings over the lifetime of the facility.
Technical Readiness	3	The methodology to extend calibration intervals has already been implemented at commercial nuclear sites.
Licensing Readiness	3	This methodology to extend calibration intervals has already been implemented at nuclear plants. For instruments with calibration and surveillance intervals identified in plant Technical Specifications, a license amendment request (LAR) is required to extend the calibration intervals. This methodology follows US NRC’s Generic Letter 91-04 which provides guidance on completing a LAR.
Implementation Proficiency	3	The implementation of this methodology to extend calibration intervals does not require knowledge in implementing digital technologies.