RC-99-0147, Submits Attached Request for Relief from Performing SG PORV Strike Time Testing to Acceptance Criteria of Asme/Ansi OMa-1988

Submits Attached Request for Relief from Performing SG PORV Strike Time Testing to Acceptance Criteria of Asme/Ansi OMa-1988

ML20210F686
Person / Time
Site:	Summer
Issue date:	07/26/1999
From:	Gabe Taylor SOUTH CAROLINA ELECTRIC & GAS CO.
To:	Cotton K NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RC-99-0147, NUDOCS 9908020102
Download: ML20210F686 (5)

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A SCANA COMPANY R 99 014 Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555 Attention: Ms. K. R. Cotton Gentlemen:

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Subject:

VIRGIL C. SUMMER NUCLEAR STATION

• wy L Tayl" :

DOCKET NO. 50/395 g$'[','[,"[g OPERATING LICENSE NO. NPF-12 STEAM GENERATOR - PORV STROKE TIME RELIEF REQUEST (NRR 990001)

South Carolina Electric and Gas Company (SCE&G) hereby submits the attached request for relief from performing steam generator power operated

~7 relief valve (SG-PORV) stroke time testing to the acceptance criteria of ASME/ ANSI OMa-1988.Section XI of the 1989 Edition of the ASME Code

' South Cm!ino mctric a cos to ; requires that the 1988 addenda of part 10 to the ASME/ ANSI Operations and Virgil C 5mner Nodecr 5tation - Maintenance Code (OM-10) be used when performing inservice testing (IST) )

l' 0. Ba 881 for valves. This code effectively restricts the SG-PORV stroke time to a e ine, seuth tmlina tolerance of less than i 5 seconds of the reference value. The inherent stroke time variances in the operators of the VCSNS SG-PORVs preclude achieving so3345;m4-- consistent stroke times within the allowed OM-10 tolerances. SCE&G requests, 803345.5209 as an attemate requirement, to apply a maximum performance stroke time limit

- =55= as the acceptance criteria for the SG-PORVs in lieu of the OM-10 tolerance based on the reference value.

u This relief request is necessary because the inherent stroke time variances in ,

the design of the SG-PORVs' operators is greater than the tolerances allowed j by OM-10. However, these variances are well within the design requirements g for the valves function. The alternative requirements of this relief request will P -,  ; allow the performance monitoring of the SG-PORVs to be meaningful and realistic for the design of these valves and will prevent the exercise of unnecessarily applying the corrective actions of 4.2.1.9 of OM-10 when there is

( ,  ? no degradation. SCE&G has determined that this alternative acceptance criteria is an appropriate method of monitoring the performance and potential degradation of the VCSNS SG-PORVs due to the unique design of the valve operator and the plant conditions required to test the SG-PORVs. ,\

9909020102 990726 i. I \

c- PDR ADOCK 05000395 R q P PDR .LQ< g i V y . NUGLtAH tXUkLLENCE- A SUMMER TRADITION!  :

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- Docum:nt Control D:sk NRR 990001

. RC-99-0147 Page 2 of,2 :

l SCE&G requests the review and approval of this relief request'as expeditiously as practical.

Should you have any questions, please call Mr. David Haile at (803) 345-4322. or Mr.

Jim Turkett at (803) 345-4047.

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, Very truly yours, G . r DCH/JT/GJT/dr Attachment c: J. L. Skolds W. F. Conway R. R. Mahan (w/o Attachment)

R. J. White L. A. Reyes K. R. Cotton NRC Resident inspector J. B. Knotts, Jr.

NSRC RTS (NRR 990001)

File (810.19-2)

DMS (RC-99-0147)

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Document Control D:sk Attachment NRR 990001 RC-99-0147 Page 1 of 3 Request for Relief from ASME/ ANSI OM-10 Acceptance Criteria for Steam Generator PORV Stroke Time Tolerance

Subject:

This relief request relaxes the acceptance criteria for stroke time tolerances imposed by Section XI of the ASME code,1989 edition as they apply to the steam generator PORVs.

Components:

Steam generator power operated relief valves IPV-2000,2010, and 2020.

Current Code Requirement:

Subsection IWV and Subarticle IWA-1600 incorporates the 1988 addenda of the ASME

/ ANSI Operation and Maintenance Code, Part 10, (OM-10) for requirements related to I inservice testing of ASME Code Class 1,2, and 3 valves. Paragraph 4.2.1.8 of OM-10 l titled " Stroke Time Acceptance Criteria," sets stroke time tolerances for various valve types. Valves not stroking within the limits of this paragraph must comply with the applicable corrective actions of 4.2.1.9.(a), (b), (c), (d), and (e). Acceptance criteria 4.2.1.8(b) and (d) apply to the PORVs and states the following: _

1 4.2.1.8(b) Other power-operated valves (non electric-motor operated) with reference l stroke times greater than 10 seconds shall exhibit no more than i 25% change in stroke time when compared to the reference value.

4.2.1.8(d) Other power-operated valves (non electric-motor operated) sNith reference '

stroke times less than or equal to 10 seconds shall exhibit no more than 50% change in stroke time when compared to the reference value.

Note: 4.2.1.8(d), yields a maximum tolerance of i 5 seconds, and 4.2.1.8.(b), would require a reference value of 20 second.c to result in a i 5 seconds tolerance.

Alternative Requirement: '

As an altemative to the above requirements, the following stroke time acceptance criteria will be applied to IPV-2000, IPV-2010, and IPV-2020:

The valve stroke time will be recorded and must exhibit an opening stroke time of less than 16 seconds.

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' Document Control D:sk' Attachment NRR 990001

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Basis for Relief:

LThe inherent seoke time variances in the design of the SG-PORV operators are outside the tolerances adowed by the OM Code but well within the design requirements for the

, valves. The variances are characteristic of the operator design and are not indicative of

- the valve cperational condition.

Also, the conditions under which the valve is tested adversely affect the consistency of the stroke time. The followlag discussion will address the design requirements related to the -

valves, the reason the inherent variances in stroke time are not an indication of valve degradation, and how the test conditions are not conducive to stroke time consistency.

Desian stroke time The SG-PORVs are deceribed in the FSAR, Section 10.4.4 as operating in conjunction with the atmospheric dump valves to provide additional steam dump capacity and as power operated relief valves for the SG secondary side. The Main Steam Design Basis Document states the SG-PORVs regulate steam line pressure following a plant trip with loss of condenser dumps to hold no load conditions. The power relief valves are necessary for the controlled shutdown of the plant if the condenser is unavailable and are specifically relied upon during a Steam Generator tube rupture with a loss of offsite power to mitigate that accident. The main steam safety valves are designed to protect the steam generators from over pressurization, however,-the operation of the SG-PORVs avoids unnecessarily cycling the main steam safety valves.

As containment isolation valves, the SG-PORVs are normally closed and fail closed to prevent an uncontrolled steam release. During norrr,al plant operation, each valve is controlled automatically by steam line pressure or Tavg. The SG-PORVs are closed during normal plant operations and fail closed upon loss of control signal. The valves have a handwheel for local operation if required due to loss of air.

Thus, the SG-PORVs retain a control function for shutting down the reactor to the cold shutdown condition and/or mitigating an accident and a fail safe function for preventing an uncontrolled steam releasc. An engineering evaluation has

- determined that a SG-PORV opening time of 20 seconds fulfills the design function of controlling secondary pressure during a design basis event that closes the main steam isolation valves (MSIVs). There is no time associated with the fail safe function.

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Docum:nt Control D:sk-Attachment

- NRR 990001 RC-99-0147 Page 3 of 3 Va'vo I Operator Desian The opening function of the SG-PORVs must meet dual criteria. The valve must open quickly (20 seconds) to handle the steam dump demand of MSIV closure and must also be able to have fine control functions to regulate steam flow for a controlled shutdown. Due to this, the valve operator was designed to use a 1 pneumatic positioner, assisted by a pneumatic booster. When the valve receives a full open signal, the booster assists the valve open to approximately 80% in 2-4 seconds. The final 20% of the opening stroke is controlled at a much slower rate by the positioner. Slight changes in valve conditions such as packing friction, supply pressure, etc. will vary the effect of the pneumatic booster on the initial portion of the opening stroke This varies the percentage- of the total stroke assisted by the booster and thus varies the portion of the stroke controlled by the much slower positioner. Therefore, the valve's full open stroke time will vary even though the valve is functioning as designed.

Testina Conditions Due to the operational impact of stroking open a SG-PORV while at power, the SG-PORVs are tested while isolated. This has two negative impacts on the test  :

process. The first is that once a SG-PORV is isolated (from approximately 500*F ,

steam) it immediately begins to cool down and introduces thermal gradients in the I valves clearances and triction bearing surfaces. These gradients introduce conditions in the valve that would not be present during inservice conditions.

Secondly, the design of the valve is such that when the valve is pressurized the pressure actually assists the valve in opening. Therefore, testing the valves while they are isolated, eliminates that assisting opening force and thus affects stroke time.

For the reasons discussed above, the design of the valve and the test conditions for the SG-PORVs will continue to result in stroke times exceeding the tolerance that the OM Code allows. Also, these variances, inherent to the valve operator, would not be indicative of valve degradation. The attemative requirements of this relief request will allow the monitoring of the SG-PORVs performance to be meaningful, and realistic for the unique design of the SG-PORVs, and will prevent the unnecessary exercise of performing the corrective actions of 4.2.1.9 of OM-10 when there is no valve degradation.

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