ML18136A868

FAQ 18-02 Rev 2 Proposed NRC Response Rev 2

ML18136A868
Person / Time
Site:	Watts Bar
Issue date:	05/17/2018
From:	Alex Garmoe NRC/NRR/DIRS/IRAB
To:
Garmoe A, NRR/DIRS, 415-3814
References
Download: ML18136A868 (6)

Text

FAQ 18-02 Rev. 2 Watts Bar Critical Hours - Proposed NRC Response Plant: Watts Bar Nuclear Plant, Unit 2 (WBN 2)

Date of Event: 12/31/2017 Submittal Date: 2/21/2018; Rev. 4/13/18 Engineer/Licensee

Contact:

Kim Hulvey/Beth Wetzel Tel/email: (423) 365-7720/(423)751-2403 NRC Contact Jared Nadel Watts Bar Tel/email: (423) 365-1776 Performance Indicators:

IE01 WBNU2 Unplanned Scrams per 7000 Critical Hours (automatic and manual scrams during the previous four quarters)

IE03 WBNU2 Unplanned Power Changes per 7000 Critical Hours (over previous four quarters)

Site-Specific FAQ (Appendix D)? - Yes FAQ to become effective when approved.

Question Section:

TVA requests either:

• The effective date of Watts Bar Unit 2 Unplanned Scrams per 7000 Critical Hours (IE01) and (IE03) Unplanned Power Changes per 7000 Critical Hours be extended until 3Q18 (through Jun 30, 2018) to allow sufficient data for an accurate assessment value, or

• Review the nature of the outage relative to new plant start-up in addition to the nature of the scrams to either:

o The Watts Bar Unit 2 Unplanned Scrams per 7000 Critical Hours (IE01) and (IE03) Unplanned Power Changes per 7000 Critical Hours be revised to include the missing critical hours from the 2017 Watts Bar Unit 2 Main Condenser outage, or o The effective date of Watts Bar Unit 2 Unplanned Scrams per 7000 Critical Hours (IE01) and (IE03) Unplanned Power Changes per 7000 Critical Hours be extended until 2Q18 (through March 31, 2018).

This request is based upon a October 22, 2015 NRC letter to TVA stating If, as the licensee approaches four quarters after either the IE or MS cornerstones become monitored, new information shows that a PI may still not provide accurate assessment value, the Frequently Asked Questions process will be utilized in accordance with NEI 99-02 to reach a conclusion on how to proceed.

NEI 99-02 Guidance needing interpretation:

NRC Letters to TVA dated November 21, 2016 (ML16326A210) and October 22, 2015 (ML15295A253).

NEI 99-02 Page 10 line 25 The number of unplanned scrams during the previous four quarters, both manual and automatic, while critical per 7,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />.

NEI 99-02 Page 14 line 9 The number of unplanned changes in reactor power of greater than 20% of full-power, per 7,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of critical operation excluding manual and automatic scrams.

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FAQ 18-02 Rev. 2 Watts Bar Critical Hours - Proposed NRC Response NEI 99-02 Page E-1 line 12 There are several reasons for submitting an FAQ:

NEI 99-02 Page E-1 line18

3. To request an exemption from the guidance for plant-specific circumstances, such as design features, procedures, or unique conditions.

Event or circumstances requiring guidance interpretation:

This FAQ concerns the Watts Bar Unit 2 new plant startup and subsequent March 23, 2017 Main Condenser failure that resulted in an estimated loss of 3100 critical hours for repair. The reactor was shut down from March 23, 2017 until July 30, 2017 while extensive repairs were completed to the Main Condenser. The cause of the failure was inadequate vendor design (1970s vintage) of the condenser wall support structure leading to support and wall failure. In addition, an extended 39 day refueling outage was completed in the fourth Quarter of 2017.

This resulted in an additional estimated loss of 930 critical hours. Being the first refueling outage following WBN Unit 2 commercial operation, many additional tests were required to meet commitments as dictated by the operating license. This resulted in a longer than baseline outage.

The main condenser repairs coupled with the extended refueling outage has resulted in a low number of critical hours (approximately 4588) for the period defined in the Oct 22, 2015 letter.

For related background, WBN Unit 2 experienced two scrams and one unplanned power change for the previous 4 quarters. Details are as follows:

• A 1Q17 scram was caused when workers inadvertently depressed a local trip pushbutton on a Hotwell Pump. The pump trip resulted in a secondary plant transient and subsequent reactor scram. The event was attributed to human performance in that workers failed to practice situational awareness around scram sensitive equipment.

Corrective actions included coaching Operations personnel on the need to control work activities near operating equipment and installation of bump guard covers on local pushbuttons for a number of Unit 2 secondary pumps.

• A 4Q17 scram was caused by an intermittent circuit card connection in the 2AC Rod Control Power Cabinet. The equipment malfunction resulted in 4 dropped control rods and a subsequent manual reactor scram by control room operators. Corrective actions included a 100% inspection of circuit card connections in the Rod Control Power Cabinets and replacement of suspect cards. No common cause was assessed to exist between the two scrams.

• A 3Q17 unplanned power change was caused by a Main Turbine steam leak.

Per the October 22, 2015 letter from NRC to TVA, the NRC stated that the transition of WBN Unit 2 to the full oversight of the ROP will be a phased approach on an individualized cornerstone basis. One of the objectives of the letter was to determine the validity of performance indicators upon transition and provide an augmented inspection plan for PIs that will not be immediately valid.

Additionally, the letter states the transfer to full ROP oversight will occur while recognizing that not all PIs will be immediately valid at the time of transition and thus would likely not provide an accurate indicator of plant performance. PIs will be declared valid once sufficient time has passed to accumulate enough representative data to provide a reasonable assessment result.

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FAQ 18-02 Rev. 2 Watts Bar Critical Hours - Proposed NRC Response The plan for the IE01, IE03, and MSPI were not to be considered as valid inputs into the Action Matrix until a minimum of four quarters of information had been provided. For IE01 and IE03, the NRC stated in order to establish the necessary baseline of critical hours to prevent falsely inflating the data, these indicators will become valid after four full calendar quarters have passed following transition of the cornerstone. The NRC went on to say that if new information shows that a PI may still not provide accurate assessment value, the FAQ process will be utilized in accordance with NEI 99-02 to reach a conclusion on how to proceed. It is TVAs position that the 4th quarter 2017 PI value for IE01 does not provide an accurate assessment value of plant performance. The indicator value has over one quarter (3100 hours0.0359 days <br />0.861 hours <br />0.00513 weeks <br />0.00118 months <br />) of missing critical hours for the initial four full calendar quarters as desired in NRCs 2015 letter (which produced a PI value marginally over 3, at the hundredths place). At the end of the 1st quarter 2018, the IE01 PI value immediately returned to a green value in the middle of the band and provides an accurate assessment value of the PI.

While TVA acknowledges the foundational aspect of the NEI 99-02 document relative to 2400 critical hours and IMC 0608 relative to extended shutdowns, the 2015 letter supersedes it qualitatively for transitioning Watts Bar Unit 2 into the ROP, and TVA views the letters silence on the 2400 critical hours and extended shutdown wording as intentional. The Watts Bar Unit 2 ROP Transition Plan meeting history and context supporting the 2015 letter made clear the NRC cognizance of Watts Bar Unit 2 being a new plant with awareness of the challenges of a plant in its first year of operation. TVAs view is the appropriate review standard should reflect new plant challenges in the first year of life and whether these challenges influenced the numerator and/or denominator per the 2015 letter with specific values purposely omitted (i.e., a qualitative standard relative to the plant challenges). TVAs position is that the denominator was dramatically influenced with over a full quarter of missing data, and falsely inflated the data and did not provide the necessary baseline of critical hours. The existing plant precedent and review standard the NRC is utilizing in the proposed response is not applicable in this situation because it is based on existing plants with extended plant shutdowns, not a plant in the first year of life..

If licensee and NRC resident/region do not agree on the facts and circumstances explain:

The NRC Watts Bar Site Resident Inspector was informed of this FAQ.

Potentially relevant FAQs:

FAQ 13-01 Turkey Point Unplanned Scrams per 7000 Hours Critical FAQ 17-04 Watts Bar Unit 2 MSPI Effectiveness Date Similar to this FAQ request, FAQ 17-04, Watts Bar Unit 2 MSPI Effectiveness Date, was recently approved by the NRC to grant an extension for MS01 (Emergency AC Power System),

MS07 (High Pressure Injection System), MS08 (Heat Removal System) and MS10 (Cooling Water Systems). The basis for this extension was the loss of critical hours within the first 12 months of operation due to the main condenser repair outage.

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FAQ 18-02 Rev. 2 Watts Bar Critical Hours - Proposed NRC Response Response Section:

Proposed Resolution of FAQ:

Due to the uniqueness of new construction and starting-up a new unit, TVA requests either:

• a two quarter extension to the effective date for WBN Unit 2 IE01 and IE03 indicators (July 1, 2018) due to the loss of a significant number of critical hours. The IE01 indicator objective is to limit the frequency of those events that upset plant stability and challenge critical safety functions during power operations. The IE03 indicator monitors the number of unplanned power changes that could challenge safety functions. NEI 99-02 states that the indicators are based on 7000 critical hours which provides allowance for a routine outage. As of December 31, 2017, the total number of reported critical hours for 2017 was 4588. Extending the effective date to July 1, 2018 will allow four quarters of operation after the extended main condenser repair shutdown to provide a representative assessment result, or

• add the condenser outage time to the denominator of WBN Unit 2 IE01 and IE03 indicators. If the condenser outage is viewed as new plant related, which TVA believes, then TVA views that four full quarters, as per the 2015 letter, would not have occurred until March 31, 2018 at a minimum with the missing quarter (2Q17), or TVA recommends that the condenser outage and related testing time be added back in, so as to not overly penalize new plants due to new plant problems in spirit with the basis behind the 2015 letter. TVA would request the NRC review the nature of the outage relative to new plant start-up, in addition to the nature of the scrams, to keep in concert with what TVA believes to be the supporting basis behind the 2015 letter.

If appropriate, provide proposed rewording of guidance for inclusion in next revision:

None PRA update required to implement this FAQ? No MSPI Basis Document update required to implement this FAQ? No Proposed NRC Response:

Both the IE01 and IE03 PIs are baselined to an occurrence rate per 7,000 critical hours and include a built-in lower limit of 2,400 critical hours, under which the indicator output is N/A to preclude misleadingly high values at low critical hours. The ROP transition letter, dated October 22, 2015, noted that, in order to establish the necessary baseline of critical hours to prevent falsely inflating the data, the IE01 and IE03 PIs would become valid after four full calendar quarters have passed following cornerstone transition to the ROP. Since the IE cornerstone was transitioned in November 2016, the IE01 and IE03 PIs became effective when 4Q2017 data was submitted. As of the end of 4Q2017, Watts Bar Unit 2 had accumulated more than 6,200 critical hours since initial startup, almost 2,700 critical hours following the main condenser maintenance outage, and the IE01 and IE03 PI calculations for 4Q2017 included nearly 4,600 critical hours in the prior four quarters. Given that the 2,400 critical hour lower limit to preclude unreasonably high PI values was exceeded by both critical hours accrued since initial startup and the number of critical hours included in the 4Q2017 IE01 and IE03 PI reporting period, the staff views the IE01 and IE03 PIs as providing reasonable assessment values.

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FAQ 18-02 Rev. 2 Watts Bar Critical Hours - Proposed NRC Response As noted by the licensee in this FAQ, the NRC previously approved an extension request for the MSPIs in FAQ 17-04. The ROP transition letter from October 22, 2015, referred to a sensitivity study on the impact of low critical hours on MSPIs. The study concluded that the MSPIs, which nominally use the prior 36 months of data in the calculations, would produce relatively normal values after 12 months of data. The ROP transition letter used this information in determining that the MSPIs would become valid for Watts Bar Unit 2 after 12 months of operation. Because of the roughly three months of lost critical hours, the licensee requested an extension of the MSPIs by one quarter. The staff approved that request since the plant had not yet accrued the 12 months of minimum critical hours necessary for the MSPIs to provide a reasonably accurate assessment value.

The NRC reviewed FAQ 13-01, in which a similar request was made to extend the effective date of the IE01 PI due to low critical hours following an extended outage. The final NRC response to that FAQ denied the request, noted that the IE01 PI already had a built-in minimum limit before it became effective to preclude misleadingly high values, and concluded that low critical hours does not represent a unique condition that would warrant an exemption. Furthermore, the staff does not view the three month maintenance outage as an outage of sufficient length to reset PI effective dates. Section 07.03 of IMC 0608 discusses that some PIs may not provide valid indications of performance during extended shutdowns. An extended shutdown is defined in IMC 0608 as a condition in which a nuclear power reactor has been subcritical for at least six months. Additionally, the MSPI sensitivity study, while silent on the IE cornerstone, recommended that MSPIs be grayed out after a six month shutdown or greater. The staff also identified a recent three month refueling and maintenance outage (Grand Gulf in fall 2016) in which no PIs were grayed out or otherwise made invalid, and also noted that the 4Q2016 PIs for Grand Gulf were based on 4,602.4 critical hours, a very similar number of critical hours as the Watts Bar 4Q2017 PIs. The NRC has found no basis in this case to deviate from these prior staff positions.

The staff reviewed the two scrams that were included as inputs to the 4Q2017 PI to determine whether they were indicative of issues unique to a new plant. In one instance workers inadvertently depressed a local trip pushbutton on a hotwell pump, with the resulting transient ultimately causing a plant scram. The second instance involved an intermittent circuit card connection that resulted in four dropped rods and a subsequent manual scram. The staff did not find these scrams to be situations unique to a new plant.

Following discussion of the staffs proposed response to FAQ 18-02, Revision 0, at the April 5, 2018, ROP Task Force public meeting, TVA submitted Revisions 1 and 2 of FAQ 18-02 with additional information and proposed resolutions. In addition to the initial request to delay the effective date of the IE01 and IE03 PIs by two quarters, TVA provided two additional options: (1) to include the missing critical hours from the condenser maintenance outage or (2) to extend the effective date of the IE01 and IE03 PIs by one quarter. Additional background information was also included in the revised FAQs. The staff reviewed the additional background information, discussed the information with staff involved in developing the Watts Bar Unit 2 ROP transition plan, and considered the additional resolution options proposed.

The staff does not agree with the first additional option to include the missing critical hours from the condenser maintenance outage in the PI calculation. The existing calculation for the IE01 and IE03 PIs for 4Q2017 used actual scram and critical hours data from the prior four quarters.

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FAQ 18-02 Rev. 2 Watts Bar Critical Hours - Proposed NRC Response If the staff were to artificially adjust the number of critical hours in the PI calculation (the denominator), there is no way to determine how to make a corresponding adjustment to the number of events that might have occurred had the plant been operating (the numerator). In reviewing the second additional option to extend the effective date of the IE01 and IE03 PIs by one quarter, the staff determined that the existing proposed response already addressed why a one quarter delay in the effective date is not necessary for the PIs to provide reasonable assessment values.

In summary, the NRC staff does not support granting Watts Bar Unit 2 an extension to the effective date of the Unplanned Scrams per 7,000 Critical Hours PI or the Unplanned Power Changes per 7,000 Critical Hours PI, nor artificially adjusting the number of critical hours included in the PI calculations.

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