ML20203C818

Forwards Response to NRC 981217 Telcon RAI Re risk-basis of Nitrogen Accumulator Action Statement to Complete NRC Review of 951025 Proposed TS Changes

ML20203C818
Person / Time
Site:	North Anna
Issue date:	02/05/1999
From:	Christian D VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20203C822	List: ML20203C818 ML20203C825
References
99-006, 99-6, NUDOCS 9902120262
Download: ML20203C818 (17)

Text

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Vincista EimcTHIC AND POWER CONWANY RacissioNis Vinois:A 2326:

1 February 5, 1999 U.S. Nuclear Regulatory Commission Serial No.99-006 Attention: Document Control Desk NL&OSETS R1 Washington, D.C. 20555 Docket Nos.

50-338 50-339 License Nos.

NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATION CHANGE ALLOWED OUTAGE TIME FOR PORV NITROGEN ACCUMULATOR AND SEPARATE ACTIONS FOR PORV OPERABILITY REQUEST FOR ADDITIONAL INFORMATION in a letter dated October 25,1995 (Serial No.95-498), Virginia Electric and Power Company requested amendments, in the form of changes to the Technical Specifications and to Facility Operating License Numbers NPF-4 and NPF-7 for North Anna Power Station Units 1 and 2, respectively.

The proposd changes would establish an allowed outage time for the nitrogen accumulators and separate actions for the power-operated relief valves (PORV).

In a December 17, 1998 telephone conference call, the NRC staff requested additional information about the risk-basis of the nitrogen accumulator action statement to complete their review of the proposed Technical Specifications changes. The response to these questions is provided in to this letter.

This action statement for the nitrogen accumulators for the PORVs was supported with both deterministic and risk insights as descr' ed in the October 25,1995 submittal.

However, at that time, the NRC had not fmalized their position on risk-informed Technical Specifications and did not require the implementation of a risk management process for risk-informed Techr;ical Specifications. Since that time, Virginia Electric and Power Company has received approval of a risk-informed action statement for the emergency diesel generato s.

As part of that amendment, a Configuration Risk Management Program (CRMP) was incorporated into the Administrative Control Section of Technical Specifications, the action statement was annotated to identify it as

" risk-informed," and the basis was modified to address risk management.

For consistency in the implementation of risk-informed Technical Specifications, similar risk-informed annotation and discussion is being proposed for the action statement associated with the backup nitrogen accumulator for the pressurizer power operated i

I relief valves (PORV).

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I Therefore, pursuant to 10 CFR 50.90, Virginia Electric and Power Company requests additional changes to Technical Specifications to supplement the changes requested in l

l the October 25,1995 submittal. These proposed supplemental changes will identify that the proposed 14-day action statement for the backup nitrogen accumulators is j

" risk-informed" and the basis will address invoking the CRMP when using/ entering the action statement. The discussion of the proposed changes is provided in Attachment 2.

l The proposed supplemental Technical Specifications changes have been reviewed and approved by the Station Nuclear Safety and Operating Committee and the

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Management Safety Review Committee. It has been determined that the proposed 1

Technical Specifications changes do not involve an unreviewed safety question as i

l defined in 10 CFR 50.59 or a significant hazards consideration as defined in 10 CFR j

50.92. The proposed supplemental Technical Specifications changes are provided as a mark-up on the October 25, 1995 proposed Technical Specifications pages.

A Technical Specification amendment has been approved by the NRC since the October 25, 1995 submittal that has affected some of the Technical Specif' ations pages c

associated with the proposed changes. Therefore, the original Technical Specifications changes, including the proposed supplement, are provided in Attachment 4.

Please use these pages to complete your review of the proposed Technical Specifications changes.

The basis for our determination that these changes do not involve a significant hazards consideration provided in the October 25,1995 submittal remains valid since these i

changes are administrative in nature.

If you have any further questions, please contact us.

Very truly yours, D. A. Christian Vice President-Nuclear Operations Commitments made in this letter:

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The Configuration Risk Management Program (CRMP) will be invoked when the i

fourteen day risk-informed allowed outage time for the nitrogen backup supply for the PORVs is used/ entered.

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Attachments l

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U.S. Nuclear Regulatory Commission Region ll Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 i

Mr. M. J. Morgan NRC Senior Resident inspector North Anna Power Station l

Commissioner Department of Radiological Health Room 104A i

1500 East Main Street Richmond, VA 23219 i

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l COMMONWEALTH OF VIRGINIA ).

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COUNTY OF HENRICO.

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The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mr. D. A. Christian, who is Vice President - Nuclear Operations. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this 8Pday of 3 dia m.19_f_1 My Commission Expires:

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/huAk Notary Public i

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PROPOSED TECHNICAL SPECIFICATION CHANGE j

ALLOWED OUTAGE TIME FOR PORV NITROGEN ACCUMULATOR i

AND SEPARATE ACTIONS FOR PORV OPERABILITY REQUEST FOR ADDITIONAL INFORMATION 1

1 North Anna Power Station Units 1 and 2 Virginia Electric and Power Company

Response to NRC Request for Additional Information Operating Experience of Power-Operated Relief Valves (PORV) 1.

Provide the power-operated relief valves.(PORV) reliability and unavailability I

data for the last.5 yeam.

Response-Pressurizer PORV unavailability data for both North Anna units are provided in Table 1.

The hours shown for each month are the cumulative total for the previous twelve months. The significant PORV unavailability during this time has been due to leakage. Reliability data for the PORVs are provided in Table 3.

2.

Discuss and/or provide the data associated with the reliability and unavailability ofInstrument Air.

Response

Instrument Air unavailability for both North Anna un:ts are provided in Table 1.

Reliability data for the instrument air system are provided in Table 3.

3.

Provide the incidents that required the use of the AOT due to inoperable backup motive power (last 5 years).

Response

. The unavailability of the Nitrogen accumu'ator tanks and pressure control valves is tracked as part of the maintenance rule program. Table 2 shows that the components have not been out of service during period from February 1995 to the present.

4.

Provide the number of loss of offsite power events /SGTR events.

Response

There has been no loss of offsite power events at either unit of North Anna as documented in Reference 3. There has been one steam generator tube rupture and one steam generator tube leak at North Anna as documented in Reference 4.

It should be noted that both of these events occurred before the steam generators were replaced at North Anna. Performance with the inconel tube, Type-F, steam generators has been excellent.

5.

Provide the number of events that required the operators to use the backup motive power.

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Page 1 of 8

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Response

It is not possible to respond to this question without a detailed review of licensee event reports, which would require a substantial effort. Reference 4, Table D-5, indicates that there has been no loss of instrument air events at North Anna during the 1985 to 1996 period. Therefore, it can be concluded that since the instrument air system reliability has been good the backup motive power source has rarely been required to respond to initiating events.

Configuration Control / Maintenance Rule l

1.

Provide a discussion on the PORV reliability and unavailability within your maintenance rule implementation.

1

Response

The pressurizer PORVs are within the scope of the maintenance rule for North Anna. The nitrogen supply to the pressurizer PORVs is also included within the scope of the maintenance rule for North Anna. The PORVs have been assigned the following performance criteria:

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> per valve per year (includes time PORV is isolated with the MOV)

One maintenance preventable functional failure (MPFF) of either functional equipment group (FEG) per PORV per two years. Failures

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include fsilure of the PORV to open automatically or the MOV to open and does not include failures during NDT protection.

The nitrogen supply system has the following performance critena.

j 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> per RCS PORV per year and 1 MPFF per PORV (failure to supply adequate Nitrogen pressure - two years) 3.

Provide a discussion on the need for an appropriate control of plant activities to avoid potential high risk configurations during the proposed AOT.

Response

The evaluation of configuration risk at Virginia Power is governed by an i

administrative procedure that requires the use of an on-line maintenance matrix to evaluate the removal of risk significant equipment from service as part of the I

work planning process.

The matrix also treats emergent work.

Since the pressure control valves and the accumulator tanks are risk significant this equipment would not be removed from service during power operation without doing a PRA evaluation.

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NRC evaluated the current approach to configuration risk management during an inspection in November 1997. With regard to this area of the maintenance rule the inspection report cited below commented that "The licensee had effectively implemented a comprehensive process for performing safety assessments for on-line maintenance activities."

Consistent with our implementation of the Emergency Diesel Generator risk-informed allowed outage time, the Configuration Risk Management Program (CRMP) will be invoked when the fourteen day risk-informed allowed outage time for the nitrogen backup supply for the PORVs is used.

PRA/ Risk 1.

What would be the expected annual unavailability for backup motive power given i

the new 14-day AOT? Please provide a brief discussion on the basis to your response.

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Response

The annual unavailability of risk significant components within the scope of the maintenance rule is controlled by the performance criterion. As stated above the current unavailability performance criterion for the backup motive power is 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> per tank per year. As of December 15,1998 neither train of backup

, motive power had been out of service during the year. Thus, it is concluded based on planned usage (the performance criterion) and actual usage (the actual unavailability) that there would be little change in the expected annual unavailability for backup motive power.

2.

A discussion that the risk impact of the proposed change in terms of the total plant CDF (core damage frequency)/LERF (large early release frequency) would be negligible.

Response

The risk impact of the proposed change has been evaluated using the calculation module of WinNUPRAtm (see Reference). The calculation module was used to quantify the existing cut set equation with revised basic event probabilities for the unavailability of the accumulators. The table below provides the results of the calculation.

Sensitivity CDF/ year ACDF/ year LERF/ year ALERF/ year 0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> 4.049E-5 5.492E-6 l

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> 4.052E-5 3E-08 5.540E-6 SE-08 7 days 4.060E-5 1E-07 5.594E-6 1E-07 14 days 4.071 E-5 2E-07 5.696E-6 2E-07 4

Page 3 of 8

As the above table indicates the change in risk is small for the proposed ACT even assuming an average of 14 days of unavailability per year. It is concluded that this change meets the acceptance guidelines in Section 2.2.4 of RG 1.174.

References 1

NRC inspection Report Nos. 50-338/97-08 and 50-339/97-08, November 24, 1997.

2 WinNUPRAtm User's Manual, Version 1.11, May 1998.

3 Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1980 - 1996, Table C-5.

4 Rates of Initiating Events at U.S. Commercial Nuclear Power Plants 1987 through 1995, Table D-10.

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Table 1 12/22/98 North Anna Unavailability 24 Month Trend 01/94 to 01/96 Component Information Datei Unavailability Trending Data lutark Number 01/94 02/94 03/94 04/94 05/94 06/94 07S4 08/94 09/94 10/94 1154 12/94 System Function Criteria Report Date = 01/95 01/95 02/95 03/95 04/95 05/95 06/95 07/95 08/95 09/95 10/95 11/95 12/95 1-M-C-1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 m

M004 175 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 00 2-IA-C-1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 m

M004 175 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1-RC-PCV-1455C 0.0 0.6 0.8 0.8 0.9 6.5 6.7 7.3 7.9 8.3 12.4 12.4 RC RC002 36 44.7 44.5 44.5 44.5 45.0 39.4 39.5 39.0 40.6 40.4 38.4 38.8 1-RC-PCV-1456 0.0 0.0 0.0 0.0 0.2 0.2 0.3 0.3 42.6 42.8 46.9 46.9 RC RC002 36 72.7 72.9 73.0 73.0 73.0 73.0 73.0 73.0 30.9 30.9 26.7 26.8 2-RC-PCV-2455C C.0 0.0 0.3 0.3 0.3 0.3 0.3 0.6 0.6 0.6 0.8 1.1 RC RC002 36 1.3 1.5 1.5 1.9 1.9 1.9 1.9 1.6 2.9 3.1 3.1 3.3 2-RC-PCV-2456 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.5 RC RC002 36 0.6 0.8 0.9 1.1 1.1 1.1 1.1 0.9 1.3 1.4 1.4 1.5 12/22/98 North Anna Unavailability 24 Month Trend 01/96 to 0158 Component informatlon Date 1 Unavailability Trending Data Mark Number 01/96 02/96 03/96 04/96 05/96 06/96 07/96 08/96 09/96 10/96 11/96 12/96 System Function Criteria Report Date = 01/97 01/97 02/97 03/97 04/97 05/97 06/97 07/97 08/97 09/97 10/97 11/97 12/97 1-M-C-1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.5 15.5 15.5 15.5 M

M004 175 15.5 15.5 15.5 152.3 152.3 152.3 169.1 169.1 173.8 173.8 173.8 231.6 2-M-C-1 0.0 0.0 0.0 0.0 47.0 47.0 47.0 47.0 47.0 64.0 64.0 64.0 M

M004 175 107.9 107.9 190.1 190.1 143.1 160.6 185.5 217.4 217.4 225.4 225.4 225.4 1-RC-PCV-1455C 6.9 6.9 6.6 7.0 6.9 6.9 6.9 7.3 5.3 5.4 3.6 3.2 RC RC002 36 3.2 2.7 2.8 2.6 2.2 22 1.8 1.6 2.3 2.3 2.3 3.0

9C-PCV-1456 1.2 1.2 1.1 1.2 1.0 1.0 1.0 1.2 1.2 1.3 1.4 1.3 RC RC002 36 1.3 1.2 1.2 1.2 1.2 1.2 1.1 1.3 1.5 1.5 1.6 1.9 2-RC-PCV-2455C 3.4 3.3 3.5 3.1 3.1 3.1 3.4 4.0 2.7 2.5 2.3 2.1 RC RC002 36 2.1 2.0 1.9 2.1 2.5 2.7 2.5 4.2 5.0 5.4 58 5.8 2-RC-PCV-2456 1.5 1.4 1.4 1.3 1.3 1.3 1.4 1.6 1.2 1.1 1.0 0.9 RC RC002 36 0.9 0.8 0.8 1.0 1.1 1.3 1.2 1.1 1.1 1.3 1.5 2.6 Page 5 of 8

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Table 3 Reliabili Data for the Pressurizer PORVs and the Instrument Air S stem s.

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96-1-IA -C -1 3/23/96 1-lA-C-1 Tripped on 3/25/96 CLOSE TO RCE 96-0663 DUE TO TRAINING Y

IA004 IA 0663 motor overload on DEMANDS.

3/23/96 at 1625.

96-1-IA -C -1 5/16/96 ON 5/16/96 AT 0449,1-5/16/96 Corrective maintenance was completed under Y

IA004 IA I

1005 IA-C-1 tripped on WO #00341805-01&O3. No additional actions

' cooling system fault.'

are required at this time.

I upon investigation at 1-lA-C-1, the cooling skid pump (1-IA-P-1) was found tripped and had a buming smell.

96-2-IA-D-1 8/1/96 IA pressure dropped 11/7/96 A tubing line ruptured causing the air dryer to Y

IA 1391 to approx. 80 psi The blowdown. The cause was due to overtorquing instrument air dryer of the copper tubing fittings.

was blowing down.

96-2-IA-SOV-9/21/93 lA tubing ruptured 11/7/96 Tubing was overtorqued as in DR 96-1391.

Y lA 2008 207A causing the air dryer Tubing material was changed to SS to eliminate to blowdown. IA reoccurence. Not placed in A-1.

pressure went approx 81 psi.

97-1-IA-C-1 3/26/97 Weld leak found on 4/16/97 Leak was due to MIC which has already Y

IA 0754 inlet piping to 1-IA-E-identified previously and the system is already in 1B for 1-IA-C-1 on A-1 as result.

the SW side.

97-1-IA-E-1 B 3/27/97 Found thru-wall lead 4/16/97 Leak was due to MIC which has already Y

lA 0758 on water outlet piping identified previously and the system is already in of compressor.

A-1 as result.

97-2-IA-C-1 6/27/97 Tripped on Hi HP 8/20/97 The failure was an MRFF/MPFF as we allowed Y

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1959 inlettemp. Placed the compressor to fail when indication of Hi Coppus blower on temps known.

compressor.

98-1-IA-C-2A 9/23/98 "A" Containment IA 10/13/98 The failure is a FS & is an MRFF/MPFF.

Y IA004 IA 2988 compressor couldn't maintain pressure.

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Table 3 (Continued)

Reliability Data for the Pressurizer PORVs and the Instrument Air System

'94-2-RC -PCV 6/2/94 0501,2-RC-PCV-2456 6/2/94 Diaphragm was replaced although not a factor in this Y

RC010 RC 0730

-2456 failed 2-PT-212.30, failure. stem was cleaned & lubed w/ neo-lube &

stroked too slow.

proper valve operation was obtained. use of anti-seize to lube stem & packing has been stopped. this should preclude a recurrence of this failure.

94-2-RC -PCV 6/5/94 2135, CYCLING 2-RC-6/5/94 Corrective maintenance was completed under w.o.

Y RC010 RC 0751

-2455C PCV-2455C PER 2-OP-no further action required.

5.1, mid position was indicated on 'a' train limits with valve fully dosed.

95-2-RC -PCV 3/27/95 AT 2350 ON 3/27/95, 3/28/95 Extended from 4/18 (dwr). close to category 2 RCE Y

RC002, RC 0451

-2456 PORV-2456 FAILED 95-0451.

RC006 CLOSED.

95-2-RC -MOV 3/31/95 2-RC-MOV-2536 motor 4/3/95 E.T. SE 95-002, REV. O, an engineering evaluation, Y

RC002 RC 0516

-2536 went to locked-rotor (sta!!)

provided the recommended corrective actions to while closing during votes retum the mov to operable status. W.r. 030830 was testing. apparent cause written to remove the stem and penetrant test (pt) the is contactor stuck close in valve stem. The actuator tear-dowm and inspection.

breaker cubicle.

discovered on 3/31/95 at 1600.

95-2-RC -PCV 5/22/95 On 5/22/95 at 1526, 5/23/95 PER WO #319082, the coil was replaced and the pcv Y

RC006 RC 0945

-2455C attempted to cycle 2-rc-will function properfy. the alarms still come in pcv-2455c via keyswitch.

sporadically and will be evaluated via task #2 of WO Valve did not change

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position.

95-1-RC-PCV-8/14/95 AT 0845 during lamp test 8/15/95 The socket was removed and cleaned. New bulbs Y

RC010 RC 1345 1456 for 1-pt-44.7, it was found were installed. After it was reinstalled, it tested 5

that 'H' train of open (red) satisfactority repeatedly. No further corrective actions light for 1-RC-PCV-1456 are needed would not light up.

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PROPOSED TECHNICAL SPECIFICATION CHANGE RISK-INFORMED ALLOWED OUTAGE TIME FOR PORV NITROGEN ACCUMULATOR Discussion of Supplemental Changes 4

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North Anna Power Station Units 1 and 2 Virginia Electric and Power Company

Discussion of Change introduction and Background in an October 25,1995 letter (Serial No.95-498), Virginia Electric and Power Company requested changes to the Technical Specifications to provide a separate action statement for the inoperability of the backup nitrogen accumulator for the pressurizer power operated relief valves (PORV). This action statement was supported with both deterministic and risk insights as described in the October 25, 1995 submittal.

However, at that time, the NRC had not finalized their position on risk-informed Technical Specifications and did not require the implementation of a risk management process for risk-informed Technical Specifications. Since that time, Virginia Electric and Power Company has received approval of a risk-informed rection statement for the emergency diesel generators. As part of that amendment, a CRMP was incorporated into the Administrative Control Section of Technical Specifications, the action statement was annotated to identify it as " risk-informed," and the basis was changed to discuss the risk management aspects of the Technical Specifications.

Consequently, for consistency in the implementation of risk-informed Technical Specifications, similar risk-informed annotation and discussion will be provided for the action for backup nitrogen accumulator for the pressurizer power operated relief valves (PORV) as well.

Therefore, pursuant to 10 CFR 50.90, Virginia Electric and Power Company requests additional changes to Technical Specifications to supplement the changes requested in the October 25, 1995 submittal.

These proposed supplemental changes will identify that the proposed 14-day action statement for the backup nitrogen accumulators is " risk-informed" and will require invoking the configuration risk management program (CRMP) when using/ entering the action statement.

These changes are administrative in nature and do not modify the plant or its operation in any way. Therefore, an unreviewed safety question is not created.

Background

Current Licensing Basis and Design Basis The current licensing and design bases are described in the Discussion of Change provided in the October 25,1995 submittal.

Specific Changes The following changes supplement the changes proposed in the October 25, 1995 submittal:

l Proposed Action 3.4.3.2.A.2 for an inoperable backup nitrogen accumulator is being revised to include the term "(Risk-informed)" as an operator aid to implement the CRMP.

The fcilowing sentence is being included in Basis Sections 3/4.4.2 and 3 to address the CRMP:

"A configuration risk management program (CRMP) defined in Administrative Control Section 6.8.4.g is implemented to evaluate risk associated with an inoperable backup nitrogen supply."

The list of risk-informed Technical Specifications in Specification 6.8.4.g is being updated to include the proposed 14-day action statement for the backup nitrogen accumulators (3.4.3.2.A.2)

Safety Significance These supplemental changes to the proposed Technical Specifications for the PORVs, submitted in our October 25,1995 submittal, are administrative in nature.

These supplemental proposed changes are to identify that the proposed 14-day action statement for the backup nitrogen accumulators is " risk-informed" and will require invoking the configuration risk management program (CRMP) when using/ entering the action statement.. Plant systems and their operation are not affected by this administrative change. Furthermore, the change does not affect the Chapter 15 accident analysis or the Environmental Protection Plan.

Since the operation of the plant and its systems are not being modified nor are operability requirements for any system or component being changed:

There is no increase in the probability of occurrence for any accident or the consequences of any accident previously analyzed.

The change does not create the possibility of any accident or malfunction of a different type.

The margin of safety as defined in the basis of any Technical Specification is not decreased.

Therefore, there is no unreviewed safety question generated by this administrative change to the Technical Specifications.

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PROPOSED TECHNICAL SPECfFICATION CHANGE RISK-INFORMED ALLOWED OUTAGE TIME FOR PORV NITROGEN ACCUMULATOR l

Mark-up of Supplemental Changes j

identification of Risk-Informed Action Statement l

North Anna Power Station Units 1 and 2 Virginia Electric and Power Company l

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