ML20094L137

Forwards Request for Relief from ASME Code,Section XI Hydrostatic Test Requirements Involving RCS & Small Section of Connected ECCS Piping.Replacement of Check Valves 2-VLV-63-587 & 2-VLV-63-588 Expected by 920407

ML20094L137
Person / Time
Site:	Sequoyah
Issue date:	03/17/1992
From:	Joshua Wilson TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M75030, NUDOCS 9203240344
Download: ML20094L137 (9)

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J l WGon Vu e Pfer tN4 5eg q 4'g fiat tw PW t March 17, 1992 U.S. Nuclear Regulatory Commission ATTN: Docuinent Control Desk Washington, D.C. 20555 Gentlemen:

In the Ma*.ter of

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Docket Nos. 50-328 Tennessee Valley Authority

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s'QUOYAH NUCLEAR PLANT (SQN) - REQUEST FOR RELIEF FROM THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME), SECTION XI, HYDROSTATIC PRESSURE TEST REQUIREMENTS

Reference:

NRC letter to TVA dated May 31, 1990, " Relief from Code Hydrostatic Pressure Test Requirements for Reactor Coolsnt System (TACq5030)-SequoyahNuclearPlant, Unit 1"

' Enclosed is a relief request from the ASME Code, Secti<.n XI, hydrostatic 3

-test requirements involving the reactor coolant system (RCS) and a small seetion of connected emergency core cooling system (ECCS) piping for Unit 2.

This relief from the code requirements has become necessary as the result of the anticipated replacement of Check Valves 2-VLV-63-587,

-588, and -547.

During the Unit 2 forced outage in November 1991, TVA continued its investigation of possible sou-ces of inleakage into the cold-leg accumulators. TVA now conriders these three check valves to be-suspecc in contributing to the accumt.lator inleakage problem and therefore has decided to remove / repair the valves as a planned outage activity.

Valve.4 2-VLV-63-587 and -588 are 1-1/2 inch primary check valves in the saiety injection. lines to RCS 1. oops 2 and 3 cold legs, respectively.

Valve 2-VLV-63-547 is a 2-inch secondary check valve in the safety injection line to RCS Loop 2 hot leg.

9203240344 920317 S!

I PDR ADOCK 05000328

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-U.S. NuclearfRegulatory Commission Page 2 March.17 1992 Because the valves being replaced are not isolable from the RCS, a

-hydrostatic pressure test of the entire RCS would be required to comply with the /SME Section XI Code (1980 Edition, Winter 1981 Addenda.

IWA-4400 [a}"and IWA-5500). Pursuant to 10 CFR 50.55a(a)(3) and 10 CFR 50.55a(g)(5)(iii), ITA has determined that conformance to the code wonid be impractical and-would present'an undue hardship. This request is.similar to TVA's previous hydrostatic exemption for the replacement of a cLeck_ valve (VLV-63-551) on Unit 1.-

NRC approval of TVA's previous request for relief-on Unit 1

=>a provided in the referenced letter.

Replacemert of the Unit 2 check valves is required to ensure that the RCS

' leakage requirements specified in Technical Specification Limiting Condition for operation 3.4.6.1 and the SQN Section XI testing program continue _to be met.- contains a description of the maintenance activity and the basis for TVA's exemption request. contains the request for relief.

Replacement-of - Check Valves 2-VLV-63-587 and 2-VLV-63-588 is presently scheduled _during the core empty period between March 27 and April 7, 1992, of-the_ Unit 2 C> ele 5 refueling outage. A leak rate test of 2-VLV-63-547 Lis scheduled to be complete by March 15. 1992 (Mode 5 entry). Based on

.the results:of the leak rate testing on 2-7LV-63-547. SQN Site Licensing will inform NRC of the status regarding replacement of 2-VLV-63-547.

TVA requests NRC review of the relief requests before the replacement of the-check valves such thet alternatives may be coneidered should the relief request be denied.

Plehen direct questions concerning this issue to Don V. Goodin at

(/ASA 843-7734.

sincirely.

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U.S. Nuclear Regulatory Comission Page 3' March 17, 1992-z Enclosures cc (Enclosures)t Mr. D. E. 1.aBarge, Project Manager U.S. Nuclear Regulatory Comissico One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 NRC Resident Inspector Sequoyah Nuclear Plant l -

2600_.Igon Ferry Road 1

Soddy Daisy.. Tennessee 37379 Mr. B. A. Wilson, Project Chief L

U.S. Nuclear Regulatory Commission Region II-101 Marietta Street, NW, Suite 2900

Atlanta,: Georgia 30323 L

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1 ENCLOSURE 1 5

1. -DESCRIPTION OF THE MAINTENANCE ACTIVITY Primary Check Valves 2-VLV-63-587 and 2-VLV-63-588 in the 1-1/2 inch safety injection-tine to the reactor coolant system (RCS) Loop 2 ano 3 cold legs, respectively, and secondary Check Valve 2-VLV-63-547 in the 2-inch safety injection line to the RCS Loop 2 hot leg are planned to be removed and replaced. These replecements will be like-for-like changeouts of the socket-welded check valves.

The valve locations are shown on FSAR Figure 6.3.2-1.

II.

BASIS-FOR RELIEF IWA-4400(a) of the American Society of Mechanical Engineers (ASME)

Section XI Code (1980 Edition, Winter 1981 Addenda) states that "After repairs by welding on the oressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA-5500."

L Code-required hydrostatic test pressures are based on the RCS L

temperature. Test pressures range from 2,280 pounds per square inch ~

gauge (psig) at a temperature of 500 degrees Fahrenheit (F) or higher to a maximam of 2,460 psig at 100 degrees F or less. The valve-replacements, as previously described, involve sections of piping and

't velds-that cannot be isolated from the rest of the RCS; therefore, a hydrostatic test of the entire RCS would be required following the repairs and prior to the unit returning to power operation.

This requirement prescnts an undue hardship for the following reasonst

.1.

The performance of a low-temperature /high-pressure hydroctatic test

.(cold hydrostatic pressure test) would require removal of the RCS safety relief valves and installation of blind flanges.- In addition, pressurization of the secondary. side of the_ steam generators-would be

-required in order to prevent overpressurization of the steam jenerator-tubes.'-These measures result in unusual plant

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configuration'and-require additional downtime to perform. The

. additional downtime represents a substantial cost in replacement power to TVA's' system.

2.. The performance of a high-temperature / low-pressure-hydrostatic pressure test during start-up (1.e., Mode 3) presents a problem with lift.ing of the RUS pressurizer safety valves.1 The~ lowest;hy0 Pct tic test _ pressure allowed by-the code is 1.02 times-the RCS operating pressure,for 2.280 psig.

the setpoint for the RCS. pressurizer safety _

valves is 2,485 psig +1 percent.- Even though.the hydrostatic test pressure is well below the lift setpoint, the potential for smal1~

steam leaks occurring-through the valve' increases as RCS pressure L

approaches the setpoint.- The leak-tight _ pressure for thest-valves has been certified by the vendor at!approximately 10 percent below

- the setpoint' pressure..Above this pressure, the valves begin to discharge small amounts of, steam priorLto full lift. According to the valve manufacturer, this discharge could become excessive, and l

-the' proper reseating offthe relief valves would not be possibles In L

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such a case, it would be necessary to coal the unit back down and depressurize the RCS to repair the valves. Cagging or removal of the valvec for installation of a blind flange cannot be perfo med within-the LCO action timeframe required by Technical Specification (TS) 3/4.4.3.

This TS requires these valves to be operabic in Modes 1, 2, and 3.

3.

For personnel safety reascas, it is impractical to perform the visual examination of the RCS piping following a 4-hour hold period at the high-temperature / low-pressure (500 degrees F) condition.

Paragraph IWA-5245 of the ASME Section XI Code recognizes the high temperature levels that would be encountered by examination personnel and thereby allows the RCS temperature to be lowered (following the 4-hour hold time) to 200 degrees F for performance of the visual examination (VT-2).

The provision for lowering the RCS temperature will require several start-up tests to be performed again during the second heatup.

'nis places the plant in transition i

from heatup.to cooldown and imposes additional thermal cycles on the RCS that are limited by Sequoyah Nuclear Plant (SQN) TS 5.7.1.

The transition timeframe will also require two to three additional days of outage time for reperforming start-up tests.

III. _ ALTERNATIVE TESTING 1

In-lieu of the required hydrostatic pressure test, TVA proposes to perform a reduced pressure test on the new welds and component while in

-Mode 3.

The new welds downstream of 2-VLV-63-587 and 2-VLV-63-588 will

'oe tested at full RCS pressure (2,235 psig). The new welds downstream of 2-VLV-63-547 and upstream of 2-VLV-63-587 and 2-VLV-63-588 will be tested at approximately 2,000 psig using a temporary hydrostatic pump.

The new weld upatream of 2-VLV-63-547 will"be tested at approximately 1,500-psig using_the safety injection pump. Each new weld will_be visually inspected for leakage during these: reduced pressure tests. The requiled nondestructive. examination (NDE) will be performed on each new weld to' meet construction code requirements.

IV.

CONCLUSION TVA requests _ relief from the' hydrostatic pressure test requirements of the.ASME Section XI Code for replacement of Check Valver 2-VLV-63-547, 2-VLV-63-587, and 2-VLV-63-588 for SQN Unit 2._ Conformance to the code-

. requirements for hydrostatically pressure testingLthe entire RCS following the subject maintenance has been determined by TVA to result in' undue hardship.' TVA finds the reduced pressure test while. in Mode 3, in conjunction with the-NDE of'the welds and thw weld design, provides L

an acceptable alternative for ensuring.the structural integrity of the RCS pressure boundary.-. This relief request is submitted in accordance-p with 10 CFR 50.55a(a)(3) and 10 CFR 50.55a(g)(5)(111).

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l ENCLOSURE 2

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-Systems-Emergency Core Cooling System (ECCS)

-TVA Drawing: 47W811-1 Component:

2-VLV-63-547 Class:

American Society of Mechanical Engineers (ASME) Claes 1 (TVA Class A)

Function:

Provides secondary pressure isolation bounoary for the reactor coolant system (RCS) ECCS interface.

-Code l

Requirement:

IWA-4400(a), 1980 Edition, Winter 1981 Addenda of the ASME

(~

.. Boiler and Pressure Vessel Code,Section XI, states that "After repairs by welding on the pressure retaining boundary, a

-system hydrostatic test shall be performed in accordance with l

IWA-5000."

i-Basis l

h for Relief:

The replacement of 2-VLV-63-547 involves a section ci piping and welds that cannot be isolated from the rest of the RC.i; l

l therefore, a hydrostatic test of the entire RCS vould be L

required to comply with-the code requirement. This presents an undue hardship for tne following reasons:

1. -The p2rformance of a low-temperature /high-pressure test l(cold' hydrostatic pressure test) would require removal of the RCS safety relief valves and insta11adon of blind l

flanges.

In addition, pressurization of the secondary side l

of the steam generators would be required in order to; prevent overpressurization of the steam generator tubes, These measures result in unusual plant configuration and; require additional-downtime ~to perform. The-additirnal-h downtime represents a substantial cost in replacement power to TVA's system.

2..

The performance of-a high-temperature / low-pressure hydrostatic pressure test during start-up (i.e., Mode 3) presents a problem with lifting of the RCS pressurizer I

_ safety valves. The lowest; pressure _ allowed by the code is j

1.02 times the-RCS operating pressure. For Sequoyah Nuclear l-

' Plant (SQN), this is equal to.l.02. times 2,235 pounds per L

square inch (psig), or 2,280_psig. ~The setpoint-for the RCS pressurizer safety valves is:2.485 psig il percent. The

,j leak-tight pressure for these valves has been certified by

.the vendor at s.pproximately 10 percent below-the setpoint l

pressure o'r.2.236 psig. Above this pressure, the valves

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sbegin to'. discharge small amounts of steam prior to full lift. According to the valve _manuf acturer, this discharge -

could become excessiva, and the proper reseating of.the relief valves would not be possible.

In such a case, it-2

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would be necessary to cool the unit back down and depressurize the RCS to repair the valves. Cagging or remcval of the valves for installation of a blind flange cannot be performed within the LCO action timeframe required by Technical Specification (TS) 3/4.4.3.

This.TS requires these valves to be operable in Modes 1, 2, and 3.

3.

For personnel safety reasons, it is impractical to perform the visual examination of the RCS piping following a 4-hour hold period at the high-temperature / low-pressure (500 degrees F) ~ condition.

Paragraph IWA-5245 of the ASME Section XI Code recognizes the high temperature levels that would be encountered by examination personnel and thereby-allows the RCS temperature Lo be Icmered (following the 4-hour hold time) to 200 degrees F for performance of the visual examination (VT-2).

The provision for lowering the RCS temperature will requite several start-up tests to be performed again during the second power ascension. This places-the plant-in transition from heatup to cooldown and requires 'approxinately two to three additional days of outage time.for reperforming start-up tests.

- Proposed Alternative:

In 11eu of a hydrostatic pressure test, TVA proposes to perform the followings-1...The downstream welds will be visually inspected for leakage at a test pressore of approximately 2,000 psig. This will be accomplished by using a temporary hydrostatic pump to pressure the section of piping between the primary and secondary check valves (2-VLV-63-559 and 2-VLV-63-547, respectively).

2.

The upstream wold will be visually inspected for leakage-at a pressure of.approximately 1,500 psig.

in addition, the required nondestructive examinations will be performed.to meet construction code requirements.

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Unit:

2 System:

Emergency Core Cooling System (ECCS)

TVA Drawing:

47W811-1 Component:

2-VLV-63-587 and 2-VLV-63-588 Class:

American Society of Mechanical Engineers (ASME) Class 1 (TVA Class A)

Function:

Provides primary pressure isolation boundary for the reactor coolant system (RCS) ECCS interface.

Code l

. Requirement:

IWA-4400(a), 1980 Edition Winter 1981 Addenda of the ASM2 Boiler and Pressure Vessel Code,Section XI, states that "After

_ repairs by welding on'the pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA-5000."

l Basis for Relief:

The replacement of 2-VLV-63-587 and 2-VLV-63-588 involves a section of piping and welds that cannot be isolated from the rest of the RCS; therefore, a hydrostatic test cf the entire RCS

~

would be required to comply with the code requirement.

This presents an undue hardship for the following reasons 1.

The performance of a low-temperature /high-pressure test (cold hydrostati pressure test) would require removal of the RCS safety reliref valves and installation of blind flanges.. In addition, pressurization of the secondary side of the steam generators would be required in order to prevcat ossrpressurization of the steam generator tubes.

-The1e meastres result in unusual plant configuration and y

reqaire add.!tional downtime to' perform. The additional dowatime rep esents a substantial cost in replacement power to TVA's system.

2.

The performance of a high-temperature /1.ow-pressure hydrostatic _ pressure test during start-up (i.e., Mode 3) pr*sonts a problem with lifting.of the RCS pressarizer safety v'alves. The lowest pressure allowed by the code 1.

1.02 times the RCS operating pressure. -For SQN this is

_ equal-to 1.02 times 2,235 psig, or 2.280 psig. The setpoint for the RCS pressurizer safety _ valves in 2,485 psig +1 percent. 'The leak-tight pressure for these valves has been certified by the vendor at-approximately 10 percent below the setpoint pressure, or 2,236 psig. Above this pressure, the valves begin-to discharge small amounts of steam prior to full lift. According to the valve manufacturer, this discharge could become excessive, and the proper resenting of the relief valves would not be possible.

In such a case,

4

)

2 it would be necessary to cool the unit back down and depressurize the RCS to repair the valves. Cagging or removal of the valves for installation of a blind flange cannot be performed within the LCO action timef rame required by Technical Specification (TS) 3/4.4.3.

This TS requires these valves to be operable in Modes 1, 2, and 3.

3.

For personnel safety reasons, it is impractical to perform the visual examination of the RCS piping following a 4-hour hold period at the high-temperature / low-pressure (500 degrees F) condition.

Paragraph 'IWA-5245 of the ASME Section XI Code recognizes the high temperature levels that would be encountered by examination personnel and thereby allows the RCS temperature to be lowered (following the 4-hour hold time) to 200 degrees F for performance of the visual examination (VT-2).

The provision for lowering the l

RCS temperature will require several start-up tests to be performed again during the second power ascension.

This places the plant in trensition from heatup to cooldown und l

requires approximately two to three additional days of l

outage time for reperforming start-up tests, l

Proposed Alternative:

In lieu of a hydrostatic pressure test, TVA proposes to perform the following:

1.

The downstream welds will be ter.ted in conjunction with the l

l-RCS leak test that is performed during reatart in Mode 3 at l

normal operating pressure.

2.

The upstream welds will be tested by use of a hydrostatic pump at a test pressure of approximately 2,000 psig.

In addition, the required nondestructive examination will be performed to meet construction code requirements.

t PLO90205/424 1

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