A SUMMARY OF CDBI FINDINGS

IN SERVICE TESTING OWNERS GROUPDecember 2010

Clearwater, Florida

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Introduction• Component Design Bases Inspections (CDBIs) are conducted by

the NRC to review risk significant components and ensure that these components are capable of performing their intended safety functions.

• Inservice Testing (IST) is performed to assess operational readiness and detect and act upon indications of degradation to ensure that components are capable of performing their intended safety functions.▫ Although the objectives are similar, they are not identical.

• CDBI reports and findings indicate that there is an increasing emphasis on testing and test margins to ensure that design bases are adequately demonstrated to the satisfaction of the inspector.▫ Increasingly, the capacity to meet design requirements has been

linked to inservice test (IST) programs.▫ This expectation is heightened when a design basis test has not

been developed.

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IST 101• IST is intended to assess the operational readiness of

components that may be required to place the plant in safe shutdown, maintain safe shutdown or mitigate the consequences of a design basis accident.▫Assessment is accomplished by testing the

component when known to be operating acceptably at a point that may be readily duplicated during subsequent tests.

▫Reference values are established at this test point and subsequent tests are then performed at this reference point with the intent of:1. Assessing continued operational readiness.2. Detecting and taking actions in response to

degrading component conditions.

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IST 101• IST acceptance limits are determined by

imposing a specific band around the original reference values. The multipliers used to derive these bands vary dependent on both the component and the design of the component.

• Limiting values for many IST components may also be found in the UFSAR or Technical Specifications. These limits are usually expressed in terms of hydraulic performance for pumps and limiting stroke time values for power operated valves.▫UFSAR or Technical Specification limits take

precedence over ASME Code derived limits.

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Regulatory• In December of 1997, the NRC issued Information

Notice (IN) 97-090 to alert licensees to potential problems associated with safety-related pump surveillance testing

• IN 97-090 cited Appendix B, Criterion XI, "Test Control” 10 CFR Part 50 and stated that licensees have concentrated on inservice testing (IST) requirements without ensuring that design requirements were met.

• IN 97-090 also stated that there are two applicable primary requirements for safety-related pump testing: 1. To ensure that Criterion XI is met in that each safety-

related pump achieves its minimum design-required performance.

2. To ensure that each safety-related pump meets the requirements of the ASME OM Code.

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Regulatory• Criterion XI of Appendix B to 10 CFR Part 50

requires that a test program be established with written test procedures that incorporate the requirements and acceptance limits contained in applicable design documents.

• Although licensees have established IST acceptance criteria that meet the requirements specified in the ASME Code, the criteria at some plants allowed safety-related pumps to degrade below the performance assumed in the accident analyses.

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Regulatory• IN 97-090 summary:

▫ IST is intended to monitor degradation of components; however, does not require that pumps be tested at design-basis conditions.

▫ASME tests may be used to verify compliance with the ASME Code and the pump design requirements contained in plant design-basis documentation such as the FSAR.

▫ If the minimum design performance as specified in the plant design documentation is more stringent than the ASME Code acceptance criteria, then the test acceptance criteria must be adjusted to the more conservative requirements.

▫Original plant design-basis calculations, or revisions to these calculations must be properly integrated into surveillance test procedure acceptance criteria.

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NRC Inspection Guidance• The NRC Inspection Manual, Attachment 71111.21

contains prescriptive guidance for the conduct of a Component Design Bases Inspection.

• This manual defines design margin as the margin in the design calculations related to the performance of the component.▫ For example, the analytical margin for a pump includes flow

and head required for the pump to perform its function compared to the calculated capacity of the equipment.

• The Inspection Manual also requires that the inspector determine whether the design basis is met by the installed and tested configuration.▫ How this requirement is met is somewhat subjective.

Without clear guidance, CDBI related conflicts are likely as evidenced by industry OE.

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IN 2008-02, IST Specific• In March of 2008, the NRC issued IN 2008-02,

Findings Identified During Component Design Bases Inspections - Testing.

Failure to account for EDG under frequency in pump test acceptance criteria.

Failure to appropriately account for instrument uncertainties.

Failure to ensure adequate test equipment. Failure to account for valve pressure locking effects. Failure to verify the minimum containment cooling

coil fouling factor assumed in analyses. Failure to consider the effects of service water

strainer plugging on flow rate.

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The Dilemma• The ASME OM Code does not discuss design

basis capability, but does refer to operational readiness. Typically, the IST program is used in conjunction with other programs to confirm operability.

• Without question, the design basis must be protected; however, the details related to what constitutes an adequate design basis test program, what elements must be considered or where this program should reside are confusing to many.

• IST limits should be established in a manner that envelopes design limits. ▫ For example, IST limits must consider instrument

accuracy when establishing limiting values.

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The Dilemma• This example is just one of many that illustrates

the conflict that may exist and the basis for the differing expectations between the regulating authority and the IST Engineer.

• Examples of questions provided on the following slides indicate an increasing need for ISTOG to become involved and provide assistance to IST Engineers. To do this, guidance may be needed or clarifications to existing requirements developed to provide a uniform set of rules. ▫ Currently, guidance is being provided in the form of

Operating Experience.• It is important to maintain perspective - Design

Basis testing need not be established in IST Procedures.

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Industry OE - Example #1ConcernInstrument uncertainty is not accounted for in development of IST acceptance criteria.

Considerations1. Instrument accuracy is

addressed by ASME; however, uncertainty is not.

2. What is the overall impact when additional penalties associated with instrument drift, M&TE equipment, temperature changes, orifice plate tolerance, etc. are factored into the total error for a parameter using the square root of the sum of the individual errors squared (SRSS) methodology?

3. Minimize the effects by performing post test calibration checks of test instruments.

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Industry OE - Example #2ConcernInstrument uncertainty is unaccounted for in shaft speed for variable speed pumps.Examples:1. Steam driven turbine

pumps.2. Variable speed motor

driven pumps.

Considerations1. Account for instrument

accuracy for variable speed pumps.

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Industry OE - Example #3ConcernCheck valve acceptance criteria lack adequate basis and does not ensure design requirements are met.Examples:1. Differential pressure

does not ensure that idle pumps are not rotating.

2. Differential pressure does not consider additional stress on the pump shaft when a start signal is received.

Considerations1. Assess check valve reverse

flow acceptance criteria and tighten limiting values, if possible.

2. Supplement the closure test by including an additional requirement to verify idle pumps are not rotating. For example:

The check valve acceptance criteria is met when measured differential pressure is > 80 psid AND the idle pump is observed and is not rotating.

3. Develop calculations to bound the limiting values.

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Industry OE - Example #4ConcernThe effects of limit switch settings used in determining the open and closed positions of valves is not factored into IST acceptance limits.

Considerations1. Reduce the limiting value to

account for limit switch error. MSIVs closure may provide

one of the more limiting challenges.

2. Is this concern only relevant when addressing closure?

3. Does this concern vary dependent on the valve design?

4. Can ISTOG develop a product to address this concern?

5. Input from AOV, MOV Engineers would be helpful.

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Industry OE - Example #5ConcernThe effects of EDG frequency droop on pump and valve performance. Most Technical Specifications permit frequency variations as low as 58.8 hz. Examples:1. Motor stall for MOVs.2. Lower EDG frequency

translates to slower pump speed. Pump speed is directly proportional to flow rate and pump head squared.

Considerations1. Incorporate the impact of the

lowest allowable EDG frequency into pump and power operated valve calculations.

2. Minimize the impact by revising Technical Specifications to impose a tighter band. Some plants have

incorporated a new limit of + 0.5hz. ▫ The upper limit restriction

is in response to recent findings associated with EDG over frequency concerns.

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Industry OE - Example #6ConcernThe station did not have a process in place to evaluate or prevent unacceptable preconditioning of IST components. 1. The NRC utilizes Inspection

Procedure, Part 9900 to evaluate a stations ability to prevent unacceptable preconditioning.

2. The Inspection Procedure is more detailed than public information provided in the form of two previous Information Notices.

▫ INs 96-024 and 97-016 addressed preconditioning, but did not address the subject in detail and in present terms.

Considerations1. A procedure can easily be developed to

mirror the NRC Inspection Procedures. ISTOG has already developed a

Position Paper.2. There is a valid concern related to the

differing views offered by the original INs and the subsequent inspection procedure.

3. Also, many are unsure of the requirement to adhere or commit to an NRC Inspection Procedure, particularly one that differs from previous guidance and was not formally introduced.

4. This is a work management concern that has inappropriately burdened IST.

5. PM models for valves that are tested at cold shutdown can be revised to obtain an as-found stroke prior to maintenance.

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Industry OE - Example #7ConcernSurveillance testing drained water from piping for a safety related system with no provisions to ensure the system was refilled. Air was found in the system after the inspectors questioned the condition.

Considerations

1.NRC GL 2008-01, Managing Gas accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems

2.Review procedures that drain systems or portions of systems. Most vulnerable when

performing check valve closure tests.

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Industry OE - Example #8Concern• The licensee

inappropriately took credit for post-maintenance valve testing as inservice testing. This was not a valid inservice test because it was not representative of baseline valve performance.

Considerations

1.Once again, this is a Preconditioning topic.

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Industry OE - Example #9Concern• The licensee failed to

demonstrate how instrument uncertainties were correctly translated into technical specification values or acceptance criteria of surveillance tests.

• HPCI and RCIC pump performance test acceptance criteria did not bound the applicable design values. Licensee verified pump operability based on actual performance test results.

Considerations

1.Include instrument error or provide adequate test margin. Be extremely careful with

low margin components.

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Industry OE - Example #10Concern• The licensee failed to

ensure that the turbine driven emergency feedwater (EFW) pump steam admission valve inservice tests had stroke time acceptance criteria that incorporated design basis requirements. The licensee restored the valve to its design basis stroke time range.

Considerations

1.Include instrument error or provide adequate test margin.

2.A firm understanding of design basis requirements is necessary.▫ For older plants, making

this determination may be challenging.

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Industry OE - Example #11Concern• The licensee had not

verified the adequacy of design for the turbine driven AFW pump. Specifically, the pump hydraulic analysis was non-conservative, but was used to verify adequacy of surveillance test acceptance criteria for pump minimum discharge pressure.

Considerations

1.Include instrument error or provide adequate test margin.

2.Post test calibration checks of M&TE.

3.Ensure that variance around the reference band is included in these determinations.▫ It may be necessary to

restrict the allowable variance. This will also result in

more consistent test results.

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SUMMARY•Systems and components are designed and operated, as described in the current licensing basis and incorporate design margins, to ensure that some loss of quality does not lead to immediate failure.

•Current licensing basis includes commitments to specific codes and standards, design criteria, and some regulations that also dictate margins.

•Conservatism is typically incorporated into test criteria to ensure that a partial loss of quality does not immediately impact component operability.

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SUMMARY•The problem for the IST Engineer and station personnel is that 10 CFR Part 50, Appendix B, Criterion XI requirements applicable to Test Control is subjective.

•A better understanding is required for station personnel to meet governing expectations.▫For this to occur, the expectations must be clear and concise.

▫The Station may then determine the appropriate manner to meet these expectations.