ML18153C515

Proposed Tech Specs Re Visual Snubber Insp Program

ML18153C515
Person / Time
Site:	Surry
Issue date:	01/31/1991
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18153C514	List: ML18153C513 ML18153C515
References
NUDOCS 9102060212
Download: ML18153C515 (13)

Text

• TS4.17-1 4.17 SHOCK SUPPRESSORS (SNUBBERS)

Appl icabi Iity Applies to all hydraulic and mechanical shock suppressors (snubbers) which are required to protect the reactor coolant system and other safety-related systems. Snubbers excluded from this inspection are those installed on non-safety-related systems and then only if their failure or failure of the system on which they are installed would have no adverse effect on any safety-related system.

Obiective To specify the minimum frequency and type of surveillance to be applied to the hydraulic and mechanical snubbers required to protect the reactor coolant system and other safety-related systems.

Specification Each snubber shall be demonstrated operable by performance of the following augmented inservice inspection program and the requirements of Specification 4.0.3. As used in this specification, "type of snubber" shall mean snubbers of the same design and manufacturer, irrespective of capacity.

A. Visual Inspections

1. Snubbers are categorized as inaccessible or accessible during reactor operation. Each of these categories (inaccessible and accessible) may be inspected independently according to the schedule determined by Table 4.17-1. The visual inspection interval of each type of snubber shall be determined based upon the criteria provided in Table 4.17-1.

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• TS 4.17-2 B. Visual Inspection Acceptance Criteria

1. Visual inspections shall verify that:

a. the snubber has no visible indications of damage or impaired operability,

b. attachments to the foundation or supporting structure are functional,

c. fasteners for the attachment of the snubber to the component and to the snubber anchorage are functional, and

d. in those locations where snubber movement can be manually induced without disconnecting the snubber, that the snubber has freedom of movement and is not frozen up.

2. Snubbers which appear inoperable as a result of visual inspections shall be classified as unacceptable and may be reclassified acceptable for the purpose of establishing the next visual inspection interval, provided that:

a. the cause of the rejection is clearly established and remedied for that particular snubber and for other snubbers irrespective of type that may be generically susceptible, and

b. the affected snubber is functionally tested in the as-found condition and determined OPERABLE per Specification 4.17.D or E.

When hydraulic snubbers which have uncovered fluid ports are tested for operability, the test shall be performed by starting with the piston at the as-found setting and extending the piston rod in the tension mode direction.

3. All snubbers found connected to an inoperable common hydraulic fluid reservoir shall be counted as unacceptable for determining the next inspection interval.

• TS 4.17-3

4. A review and evaluation shall be performed and documented to justify continued operation with an unacceptable snubber. If continued operation cannot be justified, the snubber shall be declared inoperable and the action requirements of Specification 3.20 shall be met.

C. Functional Tests

1. At least once per 18 months during shutdown, a representative sample of 10% of the total of each type of snubber used in the plant shall be functionally tested either in place or in a bench test.

2. The representative sample selected for functional testing shall include the various configurations, operating environments and the range of size and capacity of snubbers. This representative sample shall not, to the extent practicable, include those snubbers tested in a previous representative sample.

3. At least 25% of the snubbers in the representative sample shall include snubbers from the following three categories:

a. the first snubber away from each reactor vessel nozzle,

b. snubbers within 5 feet of heavy equipment (valve, pump, turbine, motor, etc), and

c. snubbers within 1O feet of the discharge from a safety relief valve.

• TS 4.17-4

4. Snubbers identified as "Especially Difficult to Remove" or in "High Radiation Zone During Shutdown" shall also be included in the representative sample.*

5. In addition to the regular sample, snubbers which failed the previous functional test shall be retested during the next test period. If a spare snubber has been installed in place of a failed snubber, then both the failed snubber (if it is repaired and installed in another position) and the spare snubber shall be retested. Test results of these snubbers may not be included for the resampling.

6. For each snubber that does not meet the functional acceptance criteria of Specification 4.17.D or 4.17.E, an additional 10% of that type of snubber shall be functionally tested.

7. For snubbers of 50 kips and above that are extremely difficult to remove or in high radiation zones that fail the functional testing, an engineering evaluation is required to determine the failure mode.

If the failure is determined to be non-generic, an additional 10% of that category will be tested during the next functional test period.

8. If any snubber selected for functional testing either fails to lockup or fails to move, i.e., frozen in place, the cause will be evaluated and if caused by manufacturer or design deficiency all snubbers of the same design subject to the same defect shall be functionally tested. This testing requirement shall be independent of the requirements stated above for snu~bers not meeting the functional test acceptance criteria.

• Permanent or other exemptions from functional testing for individual snubbers in these categories may be granted by the Commission only if a justifiable basis for exemption is presented and/or snubber life destructive testing was performed to qualify snubber operability for all design conditions at either the completion of their fabrication or at a subsequent date.

• TS 4.17-5

9. For the snubber(s) found inoperable, an engineering evaluation shall be performed on the components which are supported by snubber(s). The purpose of this engineering evaluation shall be to determine if the components supported by the snubber(s) were adversely affected by the inoperability of the snubber(s) in order to ensure that the supported component remains capable of meeting the designed service.

D. Hydraulic Snubbers Functional Test Acceptance Criteria

1. The hydraulic snubber functional test shall verify that:

a. Activation (restraining action) is achieved within the specified range of velocity or acceleration in both tension and compression.

b. Snubber bleed, or release rate, where required, is within the specified range in compression and tension. For snubbers specifically required to not displace under continuous load, the ability of the snubber to withstand load without displacement shall be verified.

E. Mechanical Snubbers Functional Test Acceptance Criteria

1. The mechanical snubbers functional test shall verify that:

a. The force that initiates free movement of the snubber rod in either tension or compression is less than the specified maximum drag force. Drag force shall not have increased more than 50% since the last functional test.

b. Activation (restraining action) is achieved within the specified range of velocity in both tension and compression.

• TS 4.17-6

c. Snubber release rate, where required, is within the specified range in compression and tension. For snubbers specifically required not to displace under continuous load, the ability of the snubber to withstand load without displacement shall be verified.

F. Snubber Service Life Monitoring

1. A record of the service life of each snubber, the date at which the designated service life commences, and the installation and maintenance records on which the designated service life is based shall be maintained as required by Specification 6.5.B.9.

2. Concurrent with the first inservice visual inspection and at least once per 18 months thereafter, the installation and maintenance records for each snubber shall be reviewed to verify that the indicated service life has not been exceeded or will not be exceeded prior to the next scheduled snubber service life review.

If the indicated service life will be exceeded prior to the next scheduled snubber service life review, the snubber service life shall be reevaluated or the snubber shall be replaced or reconditioned so as to extend its service life beyond the date of the next scheduled service life review. This reevaluation, replacement or reconditioning shall be indicated in the records.

Bases

• TS 4.17-7 All snubbers are required operable to ensure that the structural integrity of the reactor coolant system and all other safety-related systems is maintained during and following a seismic or other event initiating dynamic loads. Snubbers excluded from this inspection program are those installed on non-safety-related systems and then only if their failure or failure of the system on which they are installed would have no adverse effect on any safety-related system.

The visual inspection frequency is based upon maintaining a constant level of snubber protection to systems. Therefore, the required inspection interval varies inversely with the observed snubber failures and is determined by the number of inoperable snubbers found during an 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 early inspections performed before the original required time interval has elapsed (nominal time less 25%) may not be used to lengthen the required inspection interval. Any inspection whose results require a shorter inspection interval will override the previous schedule.

When the cause of the rejection of a snubber is clearly established and remedied for that snubber and for any other snubbers that may be generically susceptible, and verified by inservice functional testing, that snubber may be exempted from being counted as inoperable. Generically susceptible snubbers are those which are of a specific make or model and have the same design features directly related to rejection of the snubber by visual inspection, or are similarly located or exposed to the same environmental conditions such as temperature, radiation, and vibration.

When a snubber is found inoperable, an engineering evaluation is performed, in addition to the determination of the snubber mode of failure, in order to determine if any safety-related component or system has been adversely affected by the inoperability of the snubber. The engineering evaluation shall determine whether or not the snubber mode of failure has imparted a significant effect or degradation on the supported component or system.

• TS 4.17-8 To provide assurance of snubber functional reliability, a representative sample of the installed snubbers will be functionally tested during plant shutdowns at 18 month intervals. Functional testing is to be in accordance with ASME Section XI 1980 Ed., Subsection IWF. Observed failures of these sample snubbers shall require functional testing of additional units.

Hydraulic snubbers and mechanical snubbers may each be treated as a different entity for the above surveillance programs.

The service life of a snubber is evaluated via manufacturer input and information through consideration of the snubber service conditions and associated installation and maintenance records (newly installed snubber, seal replaced, spring replaced, in high radiation area, in high temperature area, etc.... ). The requirement to monitor the snubber service life is included to ensure that the snubbers periodically undergo a performance evaluation in view of their age and operating conditions. These records will provide statistical bases for future consideration of snubber service life. The requirements for the maintenance of records and the snubber service life review are not intended to affect plant operation.

• TABLE 4.17-1

• TS 4.17-9 SNUBBER VISUAL INSPECTION INTERVAL NUMBER OF UNACCEPTABLE SNUBBERS Population Column A Column B Column C or Category Extend Interval Repeat Interval Reduce Interval (Notes 1 and 2) (Notes 3 and 6) (Notes 4 and 6) (Notes 5 and 6) 1 0 0 1 80 0 0 2 100 0 1 4 150 0 3 8 200 2 5 13 300 5 12 25 400 8 18 36 500 12 24 48 750 20 40 78 1000 or greater 29 56 109 Note 1: The next visual inspection interval for a snubber population or category size shall be determined based upon the previous inspection interval and the number of unacceptable snubbers found during that interval. Snubbers are categorized, based upon their accessibility during power operation, as accessible or inaccessible. These categories may be examined separately or jointly. However, the licensee must make and document that decision before any inspection and shall use that decision as the basis upon which to determine the next inspection interval for that category.

Note 2: Interpolation between population or category sizes and the number of unacceptable snubbers is permissible. Use next lower integer for the value of the limit for Columns A, B, or C if that integer includes a fractional value of unacceptable snubbers as determined by interpolation.

Note 3: If the number of unacceptable snubbers is equal to or less than the number in Column A, the next inspection interval may be twice the previous interval but not greater than 48 months.

Note 4: If the number of unacceptable snubbers is equal to or less than the number in Column B, but greater than the number in Column A, the next inspection interval shall be the same as the previous interval.

Note 5: If the number of unacceptable snubbers is equal to or greater than the number in Column C, the next inspection interval shall be two-thirds of the previous interval. However, if the number of unacceptable snubbers is less than the number in Column C, but greater than the number in Column B, the next interval shall be reduced proportionally by interpolation, that is, the previous interval shall be reduced by a factor that is one-third of the ratio of the difference between the number of unacceptable snubbers found during the previous interval and the number in Column B to the difference in the numbers in Columns B and C.

Note 6: The provisions of Specification 4.0.2 are applicable for all inspection intervals up to and including 48 months.

• ATIACHMENT2 VIRGINIA ELECTRIC AND POWER COMPANY TECHNICAL SPECIFICATION CHANGE REQUEST SNUBBER VISUAL INSPECTION FREQUENCY DISCUSSION OF CHANGE AND SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION

• DISCUSSION OF PROPOSED CHANGE

• In Generic Letter 90-09, "Alternate Requirements for Snubber Visual Inspection Intervals and Corrective Actions," dated December 11, 1990 the NRC has identified that the existing Technical Specifications specify a schedule for visual inspections of snubbers that is based on the number of inoperable snubbers found during the previous visual inspection and do not take into consideration the size of the snubber population. Performing these inspections at the frequency determined by the existing Technical Specifications requires a significant amount of resources and unnecessary radiological exposure. In contrast, the same level of confidence in the operability of snubbers can be obtained at longer inspection intervals by proper grouping and a statistical sample program for the visual inspection of snubbers.

The NRC has developed an alternate inspection schedule for visual inspections of snubbers that maintains the same confidence level as the existing Technical Specifications inspection schedule and will generally allow the inspections to be performed during plant outages. The new method for determining the next interval for the visual inspection of snubbers is based on the number of unacceptable snubbers found during the previous inspection, the total population or category size for each snubber type, and the previous inspection interval.

Surry Power Station is proposing a Technical Specification change that incorporates the guidance of Generic Letter 90-09 for visual inspection of snubbers. The existing Surry Technical Specifications require that snubbers with uncovered fluid ports be declared inoperable for the purpose of determining the next visual inspection interval.

In accordance with the generic letter guidance this requirement is being eliminated, which will allow functional testing of snubbers with uncovered fluid ports to determine snubber operability. Functional testing of snubbers with uncovered fluid ports is permitted in the North Anna Technical Specificatons to establish operability and determine the next visual inspection interval. The NRC's Safety Evaluation dated November 25, 1985, for that North Anna Technical Specification change considered functional testing as an acceptable method of determining operability which did not cause a reduction in the safety margin. Those snubbers found with uncovered fluid ports will be tested in the "as-found" condition in the tension mode which is conservative since the fluid is required to be supplied to the valve block and cylinder to accommodate piston rod movement in the tension direction.

. . ~

• The requirement to test the snubber in the "as-found" condition in the tension direction will be incorporated into the Technical Specifications. In addition, we have chosen to retain a fourth acceptance criterion (item 4.17.B.1.d) for visual snubber inspections which is presently in the Surry Technical Specifications.

This Technical Specification change impacts only the visual inspection requirements in Technical Specification Section 4.17.A and B. The remaining sections of the Technical Specification, 4.17.C through F and the Bases were reformatted to eliminate blank or deleted pages.

Surry Unit 1 completed its most recent refueling outage and snubber inspections in December, 1990. We have discussed the timing of the Surry outage and snubber inspection with the NRC Surry Project Manager in light of the recent issuance of the generic letter. The conclusion reached in those discussions is that a relatively short period of time will have elasped between the completion of the Unit 1 snubber inspections and the issuance of the license amendment. Accordingly, when the amendment is issued, it would be permissible to apply the criteria for determining the inspection interval in the amendment to the Unit 1 refueling outage visual inspection results and then redetermine the inspection interval at that time.

Therefore we are not including the phrase "and the first inspection interval determined using this criteria shall be based upon the previous inspection interval as established by the requirements in effect before amendment (*)" to the proposed Technical Specification Surveillance Requirement 4.17.A, Visual Inspections.

• SIGNIFICANT HAZARDS CONSIDERATION

• Virginia Electric and Power Company has reviewed the proposed changes against the criteria of 1O CFR 50.92 and has concluded that the changes as proposed do not pose a significant hazards consideration. Specifically, the proposed Technical Specifications change provides a visual inspection program consistent with the guidance of the NRC's Generic Letter 90-09, "Alternative Requirements for Snubber Visual Inspection Intervals and Corrective Actions," dated December 11, 1990. Thus, operation of the Surry Power Station in accordance with the proposed changes will not:

1. Involve a significant increase in the probability of occurrence or consequences of any accident or malfunction of equipment which is important to safety and which has been evaluated in the UFSAR. The revised visual snubber inspection program in conjunction with the functional testing program will continue to provide a 95% confidence level that 90% of the snubbers will be operable at any time. This confidence level (reliability) is equivalent to that provided by the existing snubber inspection requirements. Plant equipment and system operation are not being modified or changed.

2. Create the possibility of a new or different type of accident from those previously evaluated in the safety analysis report. By maintaining the same level of confidence (reliability) with the proposed snubber inspection program there is no impact on plant design or operation. Therefore, no new accidents could be created from those previously analyzed in the safety analysis report.

3. Involve a significant reduction in the margin of safety. No physical plant modifications, changes in plant operations, or changes in accident analysis assumptions are being made. The proposed visual inspection program provides the same level of reliability as the existing inspection requirements.

Therefore, the accident analysis assumptions remain bounding and safety margins remain unchanged.