ML20197D473

Forwards Safety Evaluation Supporting Util 850807 & 861014 Requests for Relief from ASME Code Requirements.Requests Claim Impracticality & That Relief Authorized by Law & Will Not Endanger Life or Common Defense & Security

ML20197D473
Person / Time
Site:	Maine Yankee
Issue date:	04/07/1987
From:	Sears P Office of Nuclear Reactor Regulation
To:	Randazza J Maine Yankee
Shared Package
ML20197D440	List: ML20197D436 ML20197D442 ML20197D473
References
NUDOCS 8704100021
Download: ML20197D473 (2)

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l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l i RELATED TO REQUEST FOR RELIEF FROM INSERVICE TESTING REQUIREMENTS FOR PUMPS AND VALVES MAINE YANKEE ATOMIC POWER COMPANY, MAINE YANKEE ATOMIC POWER STATION DOCKET NO. 50-309 Introduction By letter dated August 7, 1985, Maine Yankee Atomic Power Company (the licensee), submitted a letter to the Commission requesting changos to the Maine Yankee Inservice Testing Program for Pumps and Valves. By way of these changes, the licensee requested relief from certain requirements of the 1980 ASME Code Section XI, Subsection IWP (Pumps) and IW (Valves) as being impractical for the physical configuration of the Maine Yankee Atomic Power Station. 10 CFR 50.55 a(g)(6)(i) authorizes the Commission to grant relief from Code requirements and to impose such alternative require-ments as it determines is authorized by law upon making the necessary find-ings. This safety evaluation is for the licensee's relief request sub-l mitted in the above letter and as amended by a letter dated October 14, 1986.

Evaluation and Discussion i On May 12 and 13, 1986, the staff visited the Maine Yankee Atomic Power l Station to discuss the licensee's relief request. This visit is documented i

in the staff's Inspection Report 50-309/86-08. During this onsite visit, applicable piping and instrument drawings and IST procedures were re-viewed. The locations of the high pressure safety injection pumps suction gauges were also physically inspected. The staff informed the licensee that, as written, the relief requests submitted on August 7, 1985, did not l includesufficienttechnicaljustification,forthestafftocomplete

! its evaluation. The licensee was informed that in addition to the part-tal stroke test for check valve CS-53, a full stroke test of the check valve, even if by disassembly, must be accomplished when plant conditions permit and at a frequency consistent with plant safety.

The licensee submitted a revised relief request by a letter dated October 14, 1986, to address the staff's concerns. The licensee's relief request is evaluated below.

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1. Containment Spray System Suction Check Valves-Relief Request No. V-37 A. Relief Requested / Proposed Changes

' Containment spray system valves, CS-93 and CS-94, containment spray pump suction check valves (Recirculation Mode), should be exempted from the following inservice tests:

(1) Full stroke quarterly (Q)

(2) Full str, e cold shutdown (C)

(3) Partial stroke cold shutdown (Cp)

(4). Full stroke each refueling (R)

B. Code Requiren,ent 1980 ASME Code Section XI, Subsection IW.3521 requires that check valves be exercised at least once every 3 months except as provided in Subsection IW.3522.

Subsection IW.3522 requires that check valves shall be exercised to the position required to fulfill their function unless such operation is not practical during plant operation. If only limited operation is practical, during plant operation the check valve shall be part-stroke exercised during plant operation and full-stroke exercised during cold shutdowns. Valves that cannot be exercised during plant operation shall be specifically identified by the Owner and shall be full-stroke exercised during cold shutdowns. Full-stroke exercising during cold shutdowns for all valves not full-stroke exercised during plant operation shall be on a frequency determined by the intervals between shutdowns as follows: for intervals of 3 months or longer, exercise during each shutdown; for inter-vals of less than 3 months, full-stroke exercise is not required unless 3 months have passed since the last shutdown exercise.

Valves that are normally closed during plant operation and whose function is to open on reversal of pressure differential shall be tested by proving that the disk moves promptly away from the seat when the closing pressure differential is removed and flow through the valve is initiated, or when a mechanical opening force is applied to the disk. Confirmation that the disk moves away from the seat shall be by visual observation, by electrical signal initiated by a position indicating device, by observation of substan-tially free flow through the valve as indicated by appropriate pressure indications in the system, or by other positive means. This test may be made with or without flow through the valve. If it is made without flow through the valve, a mechanical exerciser shall be used to move the disk.

The force or torque delivered to the disk by the exerciser must be limited to less than 10% of the equivalent force or torque represented by the minimum emergency condition pressure differential acting on the disk, or

to 200% of the actual observed force or torque required to perform the exercise on the valve when the valve is new and in good operating condition, whichever is less, except that'for vacuum breaker valves the exerciser.

force or torque delivered to the disk may be equivalent to the desired functional pressure differential force. The disk movement shall be sufficient to prove that the disk moves freely off the seat.

C. Basis For Relief Flow testing these check valves would require operating a 5,000 gpm pump taking suction from the safeguards sump located on the

-2 ft. alevation in the containment building. The safeguards sump only holds approximately 400 gallons which is not enough to operate a 5000 gpm pump. The only way to provide enough suction through the safeguards sump would be by flooding the containment building from the -39 ft. elevation to about the 0 ft. eleva-tion. This would require an enormous amount of water and would submerge many plant components. Flow testing these check valves is considered to be impractical. An alternate test will be per-formed.

The only other practical method of ensuring that these valves operate satisfactorily is by disassembling the valve and manu-ally operating the clapper. This, however, cannot be done during normal plant operation because isolating these valves would ren-der one train of low pressure safety injection and one train of containment spray inoperable.

The primary grade borated water in these valves is very compat-ible with the valve internals. These valves are not subject to any vibration induced failures because the RAS sump is only used during an accident.

These valves have been disassembled and manually stroked in the past and have been found to be as good as new. Based on past l performance and the fact that disassembling these valves re-quires working in a highly contaminated area with respirators, disassemb'ing and exercising, alternately, one valve each refuel-ing will provide reasonable assurance that these valves will

, continue to perform their intended function. I D. Proposed Alternate Test Alternately, one valve will be disassembled and exercised every re-fueling outage. If a degraded condition is found, the valve in the other train will be disassertbled and exercised.

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4 E. Technical Evaluation / Discussion

'j The staff's review confirms that it is impracticable within the exist-ing facility design to achieve the necessary testing flow from-the containment sump. The staff agrees that a valve sampling disassembly and inspection utilizing a manuul full stroke of one disk is an acceptable method to verify check valve full stroke capability. In order to sample only one valve each refueling outage, both valves must be of the same design, manufacture, size, model number, and materials of construction and must have the t,ame service; otherwise, both valves are to be disassembled each refueling outage. Addition-ally, at each disassembly, it must be verified that the disassembled valve is capable of full stroking and that its internal parts are structurally sound (no loose or corroded parts).

Based on this review and review of the licensee's justification, the staff agrees with the licensee's basis; and, therefore, relief, sub-ject to the conditions stated above, should be granted from the re-quirements of the ASME Code Section.XI, Subsection IW, Articles 3521 and 3522 for the tsst and test frequencies listed in the relief re-quest. The licensee has demonstrated that, because of the system con-figuration, it is impractical to test the check valves in the manner specified in the Code.

F. Conclusion The staff concludes that due to system configuration, the relief re-quested should be granted and the additional sampling requirements as stated in paragraph 1.E above are imposed. The proposed alternate testing should give reasonable assurance of valve operability re-quired by the Code; therefebe, the staff concludes that the relief granted will not endanger life or property or the common defense and security of the public.

2. Containment Spray Systpm Recirculation Line Check Valve. Relief Request No.V-63 i 1

A. Relief Requested / Proposed Changes .

L Containment spray system valve, CS-53, minimum recirculation check valve, should be exempted from the following inservice test:

(1) Full stroke quarterly (Q),

(2) Full stroke cold shutdown (C),

< (3) Partial stroke cold shutdown (Cp), and j

(4) Full stroke each refueling (R)

8. Code Requirements 1980 ASME Code Section XI, Subsection IW.3521 requires that check valves be exercised at least once every 3 months except as provided in Subsection IW.3522.

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Subsection IWV.3522 requires that check valves shall be exercised to the position required to fulfill their function unless such operation is not practical during plant operation. If only limited operation is practical, ,

during. plant operation the check . valve.shall be part-stroke exercised during plant operation and full-stroke exercised.during cold shutdowns.' Valves that cannot be exercised during plant operation shall be specifically'ide'ntified ,

by the Owner and shall be full-stroke exercised during cold shutdowns.

Full-stroke exercising during cold shutdowns for all valves.not full-stroke exercised during plant operation shall be on a~ frequency. determined by.the intervals between shutdowns as follows: :for intervals of 3 months or longer, exercise during each shutdown; for intervals of-less than 3 months, full-stroke exercise is not required unless 3 months have passed since the-last shutdown exercise.

Valves that are normally closed during plant operation and whose function is to open on reversal of pressure differential shall be tested by proving.

that the, disk moves promptly away from the seat when the closing pressure differential is removed and flow through the valve is initiated, or when a '

mechanical opening force is applied to the disk. Confirmation that the disk moves away from the seat shall be by visual observation, by electrical 4

signal initiated by a position indicating device, by observation of substan-j tially free flow through the valve as indicated by appropriate pressure indications in the system, or by other positive means.. This test may be made with or without flow through the valve. If it is made without flow

! through the valve, a mechanical exerciser shall be used to move the disk.

l The force or torque delivered to the disk by the exerciser must be limited to less than 10% of the equivalent force or torque represented by the mini-mum emergency condition pressure differentia 1' acting on the disk, or to 200% of the actual. observed force or torque required to perform the exercise on the valve when'the valve is new and in good. operating condition,'which-ever is less, except that for vacuum breaker valves the exerciser force or torque delivered to the disk may be equivalent to the desired functional-pressure differential force. The disk movement shall be sufficient to

, prove that the disk moves freely off the seat.

1 C. Basis for Relief CS-53 is a 6-inch check valve which allows minimum recirculation flow

from the low pressure safety injection (LPSI) and.three-containment j spray (CS) pumps back to the refueling water storage tank. -To be sure ,

!- that this valve goes full open and passes the maximum design flow, four-

, of these pumps would have to be run in the full recirculation mode simul-

taneously. Operating four of these pumps in the recirculation mode simul-taneously would render both trains of LPSI and CS inoperable. The tech-nical specifications require both trains to be operable during normal plant operation. This would also render both trains of residual heat removal (RHR) inoperable during cold shutdowns. For these reasons, it is imprac -

ticable to perform a full stroke flow test on this valve during normal

plant operation and cold shutdowns.

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. D. Proposed Alternate Test CS-53 shall be partially stroked quarterly (QP) during monthly test- l ing and shall be disassembled, inspected, and manually full stroked while disassembled during each refueling outage (Cp).

E. Technical Evaluation / Discussion The staff reviewed the licensee's technical specifications and draw-ing 11550-FM-92A, " Operating Valve No.5 Diagram RHR, Containment Spray, and Low Pressure Safety Injection Piping," for purposes of eval-uating the licensee's original relief request dated August 7,1985.

Review of the drawing confirmed to the staff that it is impractical to get full design flow through this check valve. As previously noted in section 1.E of this safety evaluation, disassembly and inspection utilizing a manual full stroke of the disk is an accept--

able method to verify full stroke capability.

Based on the above review, including the licensee's submitted just-ifications, the staff agrees with the licensee's basis and, there-fore, relief should be granted from the requirenents of ASME Code Section XI, Subsection IW, Articles 3521 and 3322 for the test and test frequencies listed in the relief request. The licensee has de-monstrated that, because of the system configurations, it is impract-ical and potentially unsafe to test this check valve in the manner specified in the Code.

F. Conclusion The staff concludes that, due to system configuration, the relief re-quested should be granted and the proposed alternate test is imposed.

The proposed alternate testing should give reasonable assurance of valve operab1;'.ty required by the Code; therefore, the staf f concludes that the relief granted will not endanger life or property or the common defense and security of the public.

3. Power Operated Valve Stroke Times Generic Relief Request A. Relief Requested / Proposed Change Generic relief is requested from the requirement to use the previous stroke time test results for the basis of increased test frequency.

The use of a fixed reference value determined from the stroke time results from several previous tests would be used instead.

B. Code Requirement IW-3417(a) states that, if, for power operated valves, an increase in stroke time of 25% or more from the previous test for valves with full-stroke times greater that 10 seconds or 50% or more for valves with full-stroke times less than or equal to 10 seconds is observed, test frequency shall be increased to once each month until corrective action is taken, at which time the original test frequency shall be resuared.

C. Basis for Relief Using a fixed reference value provides a more logical and stringent basis for determining increased test frequencies. Adhering to the Code as stated above, a valve's stroke time could increase during each test and still be considered acceptable, while in fact, the valve could be failing or, at least, worthy of being tested at an increased frequency. Using a fixed reference value as a standard would give rise to an increased test frequency much sooner than the standard set forth in the Code.

Having a fixed reference value would provide a means for promptly making known whether or not a valve is operating in the' normal, alert, or inoperative range. The reference values with corresponding alert and inoperative values may be incorporated into plant surveil-lance procedures which control valve testing; and, therefore, would allow one to immediately assess whether or not a valve is operating satisfactorily.

D. Proposed Alternate Basis for Increased Test Frequencies Vice IWV 3417(a)

If a fixed reference value is exceeded by either:

1.) 25% or more for those reference values greater than 10 seconds, or

2. ) 50% or more for those reference values less than or equal to 10 seconds, The frequency of testing shall be increased to once a month until the condition is corrected.

E. Technical Evaluation / Discussion The staff agrees with the licensee's basis; and, therefore, relief should be granted from the requirements of ASME Section XI Subsection IWV, Article 3417(a) for corrective action criteria as listed in the relief request. The licensee has demonstrated that their method for evaluating power operated stroke times is more conservative than that i

specified in the Code. By using a constant reference value, a grad-ual drift in stroke times can be precluded.

F. Conclusion The staff concludes that the relief request should be granted; and, the alternate test basis is imposed. The alternative evaluation criteria is bounded by that currently required by the Code; there-fore, the staff concludes that the relief granted will not endanger life or property or the common defense and security of the public.

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1 . 4. High Pressure Safety Injection Pumps Suction Gauges Relief Request No.P-5 L A. Relief Requested / Proposal Change Installed suction gauges of the three high pressure injection pumps P-14A, P-148 and P-145 be allowed to remain-at the current range of

' 0-120. psi or four times reference value rather that be changed to a range of 0-90 PSI or three times reference value as specified in the Code.

B. Code Requirements IWP-4120 -

The full-scale range of each instrument shall be three j times the reference value or less.

C. Basis for Relief During a normal plant operation, these pumps are aligned as charging pumps and have a suction pressure of around 30 psia. ASME Section XI requires that the gauge used to measure the suction pressure during inservice pump tests shall have a maximum range of zero to three times the reference value which, in'this case, is 0-90 psia. Also, the accuracy must be within i 2% of full scale. However, during an acci-

dent situation, these pumps are realigned as high pressure safety in-

, jection pumps and, after a recirculation actuation signal (RAS), take 4

suction from the discharge of the containment spray pumps. In this situation, the suction pressure of the pumps would exceed 90 psia. A suction pressure in excess of 90 psia could potentially, damage a 0-90 psia gauge.

Therefore, Maine Yankee deems it necessary to use a 0-120 psia gauge

, to ensure that the gauge will be operable during an accident situa-tion. Also, this 0-120 psia gauge is calibrated to within i 1% of full scale (1.2 psi) as compared to the code required accuracy for the 0-90 psia gauge of i 2% of full-scale (1.8 psi). Therefore, the 0-120 psia gauge is more accurate than the code requires. The pumps also have a large differential pressure of about 2500 psi. This means that significant~ variations'in suction pressure will cause small percentage changes in differential pressure. For example, a 10 psi error in the suction pressure reading would give a change in dif-ferential pressure of only 0.4%. This is well within the code allow- ,

ed variation of the acceptable differential pressure range of plus 2%

to a minus 7%.

4 D. Alternate Test n For the reasons stated above, the currently installed 0-120 psia gauges will continue to be used to measure the suction pressure on the high pressure safety injection pumps duringLinservice testing.

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E. Technical Evaluation / Discussion The staff confirmed that HPSI pump measured discharge pressures were approximately 2475 psig and suction pressures approximately 40 psig.

Measured discharge pressures for the containment spray pumps were approximately 195 psig. The above test data confirm the licensee's calculations. The staff notes that the containment spray pumps-discharge would do potentially less damage to a 0-120 psi gauge than to a 0-90 psia gauge when those pumps discharge to the suction side of the high pressure injection pumps. The licensee has demonstrated that use of 0-90 psia gauge would provide no improvement in safety or inservice test results; and, in fact could create a situation potentially more damaging to those gauges. The staff also notes that IWP-4110 requires the licensee to assure instrument accuracy to with-in 12% of full scale.

Based on the above review and review of the licensee's justificat-ions, the staff agrees with the licensee's basis. Therefore, relief should be granted from the requirements of Section XI, Subsection IWP

, Article 4120 for HPSI pumps suction gauges listed in the relief re-quest.

F. Conclusion The staff concludes that the relief requested should be granted. The alternate use of higher range suction gauges will not affect eval-uations of high pressure safety injection pumps performance; there-fore, the staff concludes that the relief granted will not endanger life or property or the common defense and security of the public.

Date: April 7,1997 Principal Contributor:

N. J. Blumberg, R:I

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