ML17037C171

Letter Regarding a Review of the November 18, 1974 Submittal and a Request That Niagara Mohawk Submit an Application for Amendment to the License That Would Change the Technical Specifications to Be in Conformance with ...

ML17037C171
Person / Time
Site:	Nine Mile Point
Issue date:	07/25/1975
From:	Lear G Office of Nuclear Reactor Regulation
To:	Rhode G Niagara Mohawk Power Corp
References
Download: ML17037C171 (16)

Text

Docket No. 50-220 Niagara Mohawk Power Corporation ATN: Mr. Gerald K. Rhode Vice President - Engineering 300 Erie Boulevard Nest Syracuse, New York 13202 Gentlemen:

In tho summer of 1973 a significant number of hydraulic shock suppressors (snubbers) were found to bo inoperable at many reactor facilities. The failures were caused by severe degradation of seal materials and the subsequent leakage of hydraulic fluid. Subsequently, an extensive seal replacement program was carried out which significantly reduced the incidence of snubber failure. In addition, by letter dated October 1, 1973, we requested that Niagara Mohawk Power Corporation submit proposed changes to the Technical Specifications which would establish a snubber surveillance program for Nine Mile Point Unit l. Your letter of November 18, 1974 was responsive to our request.

Concurrent with our review of your November 18, 1974 submittal, the NRC staff developed model technical specifications and bases which provide additional assurance of satisfactory snubber operation. These model technical specifications reflect the accumulated industry-wide experience with respect to snubber performance and reliability. A copy of these specifications is enclosed. Since they were not prepared explicitly for your plant, some editing may be necessary in order to adapt them to the Nine Mile Point Unit 1 design and nomenclature.

H You are requested to submit, within 4S days from your receipt of this letter, an application for amendment to the license for Nine Mile Point Unit 1 that would change the technical specifications to be in conformance with the requirements of the enclosed model technical specifications.

In addition to the technical specification changes, please include in your submittal a separate listing of those hydraulic snubbers which you,(

consider to be non-safety related.

OPPICC~

CURNAMC8P'ATCSP Form hEC-S18 (Re7. 9-SS) hE(M 0240 4 U, 6; OOYCRNMCNT PRINTINO OPPICCI '1674 666 166

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We would be pleased this request.

to meet with you if you have questions concerning Sincerely, George Lear, Chief Operating Reactors Branch 03 Division of Reactor Licensing

Enclosure:

Model Technical Specifications cc w/encl:

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Arvin E. Upton, Esquire LeBoeuf, Lamb, Leiby $ MacRao 1757 N Street, N. W.

Washington, D. C. 20036 Anthony Z. Roisman, Esquire Berlin, Roisman 6 Kessler 1712 N Street, N. W.

Washington, D. C. 20036 Dr, William Seymour, Staff Coordinator New York State Atomic Energy Council New York State Department of Commerce 112 State Street Albany, New York 12207 Oswego City Library 120 L'. Second Street Oswego,. New York 13126

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t 1 MODEL TECHNICAL SPECIF1CATIONS LIMITING CONDITION FOR OPERATION SURVEILLANCE RE UIREMENT.

3.6. I Hydraulic Snubbers .6.I H draulic Snubbers

1. During all modes of operation The following surveillance apply to all hydraulic snubbers require-'ents except Cold Shutdown and Refuel, all hydraulic snubbers which listed in Table 3.6.I.

are required to protect the primary coolant system or any l. All hydrau1ic snubbers whose

. other safety related system or seal material has been demon'strated component shall be operable by operating experience, lab testin.

except as noted in 3.6.I.2 or analysis to be compatible through 3.6. I.4 below. These with the operating environment safety related hydraulic snubbers shall be visually inspected to are listed in Table 3.6.I. verify their operability in .

accordance with the following 2, From and after the time that scheduled:

a hydraulic snqbbqr is determined to be inoperable, continued Number of,Snubbers Next Required reactor operation is permissible Found Inoperable Inspection only during the succocding 72 During Inspection Interval hours unless the snubber is sooner or During Inspection made operable. Interval

3. If the yequirements of 3.6.I.l 0 18 12 months months

+

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250 259 and 3.6.I,2= cannot bc met, an 1 orderly shutdown shall be initiated 2 6 months + 259 and the reactor ppall be in a 3,4 124 days + 25'o cold shutdown condition with 5,6,7 62 days + 258 36 hours. >8 31 days + 25'o

4. If a hydraulic snubber is determined The required inspection interval to be inoperable while the reactor shall not be lengthened more is in the shutdown or refuel mode, than one step at a ti.-..e.

the snubber shall b9 made operable .

prior to reactor startup. Snubbers may be categorized in two groups, "accessible" or "inaccessible" based on their accessiblity for inspection during reactor operation.

These two groups may be inspected independently according to the above schedule.

2. All hydraulic snubbers whose seal materials have not been demonstrated to be compatible with the operating environment shall be visually inspected .

for operability every 31 days.

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4 1

LIMITING CONDITION FOR OPERATION SURVEILLANCE RE UIREMENT 4.6.I H draulic Snubbers (cont'd)

S. The initial inspection'hall be performed within 6 months from the date of issuance of these speci-fications. For the purpose of entering the schedule in Speci-fication 4.6.I.l, it shall be assumed that the facility had been on a 6 month inspection interval.

4. Once each refueling cycl,e, a representative sample of 10 snubbers or approximately 10'-'f the snubbers, whichever is less, shall be functionally tested for operability including verification of proper piston movement, lock up and bleed.

For each unit and subsequent unit found inoperable, an additional 10'r ten snubbers shall be so tested until no more failures are found or all units have, been tested'.

5, Once each refueling cycle at least two representative snubbers from a relatively severe environment shall be completely disassembled and examined for damage and abnormal seal degradation.

"I Identification No. Location Elevation

'I I BASES:

3.6.I and 4.6.I H draulic Snubbcrs Snubbers are designed to prevent unrestrained pipe motion under dynamic loads as might occur during an earthquake or severe transient, while allowing normal thermal motion during startup and shutdown. The consequence of an inoperable snubber is an increase in the probability of structural damage to piping as a result of a seismic or other event initiating dynamic loads. It is therefore required that all hydraulic snubbers required to protect the primary. coolant system or any other safety system or component be operable during reactor operation.

Because the snubber protection is required only during relatively low probability events, a period of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is .allowed for repairs or replacements. In case a shutdown.is required, the,. allowance of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to reach .a cold shutdoiiy copdition will permit an orderly shutdown consistent with standard operating procedures.

Since plant startup should not commeqce with knowingly defective safety related equipment, Specificati,on 3.6.I.4 prohibits startup with inoperable snubbers.

All safety related hydraulic snubbers are visually inspected for overall integrity and operability. The inspection will'include verification of proper oriengption,.

adequate hydraulic fluid level and pgoper attachment of snubber to piping hand structures'he inspcctio>> frequency is b'ased upon maintaining a constant level of snubber.

p1otection. Thus the required inspection interval varies inversely with the observed snubber failures. The number of inoperable snubbcrs found during a required inspection determines the time interval for the next required inspection. Inspections performed before that interval has elapsed may be used as a new reference point to determine the next, inspection. However, the results of such carly inspections performed before the original required time interval has elapsed (nominal time less 25'o') may, not be used to lengthen the requiped inspection interval. Any inspection whose results require a shorter inspection interval will override the previous schedule.

Experiencq at operating facile.ties has shown that the required surveillance prqgram should assure ap acceptable level of snubber performance provided that the seal materials are compatible with the operating environment.

Snubbers containing seal material which has not been demonstrated by operate.ng experie>>ce, lab tests or analysis to be compatible with the operating enviro>>ment Should be inspected pore frequeptly (every month) until material compatability is confirmed ox a>> appropriate,changeout is completed.

I Examination of defective snubbcrs at reactor facilitios and material tests performed at several laboratories (Reference 1) has shown that millable g1un polyurethane deteriorates rapidly under the temperature and moisture conditions present in many snubber locations. although molded polyurethane exhibits greater resistance to these conditions, it also may be unsuitable for application in the higher temperature enviro>>mengp., Data pre not currently available to precisely defj.ne an upper temperature limit for the molded polyurethane. Lab tests and zn-,p$ ant experience indicate that sea3, materials are available, primarily enhylene propylene

s BASES:

3.6.X and 4.6.1 H draulic Snubbers (cont'd) compounds; which should give satisfactory performance under the most severe conditions expected in reactor installations.

1 To further increase the assurance of snubber reliability, functional tests should be performed once each refueling cycle. These tests will include stroking of the snubbers 'to verify proper piston movement, lock-up and bleed. Ten percent or ten snubbers, whichever is less, represents an adequate sample for such tests.

Observed failures on these samples should require testing of additional units.

Snubbers in high radiation areas o'r those especially difficult to remove need not be selected for functional tests provided operability was previously verified.

To complement the visual external inspections, disassembly and internal examination for component damage and abnormal seal degradation should be performed. The examination of two units, each refueling cycle, selected from relatively severe environments should adequately serve this purpose. Any observed wear, breakdown or deterioration will provide a basis for additional inspections.

(1) Report, H. R. Erickson, Bergen Paterson to K, R. Goller, NRC, October 7, 1974

Subject:

Hydraulic Shock Sway Arrestors i ~ ~