ML20070E541

Proposed Tech Spec Revising Visual Exam,Visual Exam Acceptance Criteria & Functional Testing of Snubbers

ML20070E541
Person / Time
Site:	Wolf Creek, Callaway, 05000000
Issue date:	12/15/1982
From:	STANDARDIZED NUCLEAR UNIT POWER PLANT SYSTEM
To:
Shared Package
ML20070E523	List: ML20070E520 ML20070E541
References
NUDOCS 8212170293
Download: ML20070E541 (8)

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PLANT SYSTEMS 3/4.7.8 SNUBBERS.

LIMITING CONDITIONS FOR OPERATION 3.7.8 All snubbers listed in Tables 3.7-4a and 3.7-4b shall be OPERABLE.

APPLICABILITY: MODES 1, 2, 3 and 4. (MODES 5 and 6 for snubbers located on systems required OPERABLE in those MODES).

ACTION:

With one or more snubbers inoperable, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> replace or restore the inoperable snubber (s) to OPERABLE status and perform an engineering evaluation on the supported component or declare the supported system inoperable and follow the appropriate ACTION statement for that system.

SURVEILLANCE REQUIREMENTS 4.7.8 Each snubber shall be demonstrated OPERABLE by performance of the followina inservice inspection program.

a. VISUAL EXAMINATION The first inservice visual examination of snubbers shall be performed at the first refueling outage and shall include all snubbers listed in Tables 3.7-4a and 3.7-4b. Subsequent visual examinations shall be performed in accordance with the following schedule.

Number Unexplained Inoperable Snubbers in Group Being Subsequent Visual Examined Per Examination Period Examination Period *

< 5% 18 months + 25% l

~ 5% + 1 12 months + 25%

5% + 2 6 months T 25%

5% + 3, 4 124 days T 25%

5% + 5, 6, 7 62 days T 25%

5% + 8 or more 31 days T 25%

Major groups of snubbers may be categorized as accessible or inaccessible during reactor operation. Additionally, snubbers may be grouped based on physical characteristics, environmental conditions, or others which can be justified.

If there are no unacceptable snubbers resulting from the examination of a group of snubbers during two successive refueling outages the semple size for the next required examination of the group in which there -are no unacceptable snubbers may be reduced to 50% of the snubbers within the eligible group, upon approval of the NRC. Subsequent examinations in which all snubbers within a particular group were acceptable may be further reduced in steps to 25% and 10% of that eligible group. All snubbers subject to examination must equal at least 10% of the total number of snubbers listed in tables 3.7-4a and 3.7-4b, as applicable.

• - The provisions of Specification 4.0.2 are not applicable.

I 8212170293 821215 PDR ADOCK 05000482 A PDR

SURVEILLANCE REQUIREMENTS (CONTINUED)

When an unacceptable snubber is found during a required group exam-ination, the sample size for that examination shall be increased to 100% of the group in which the unacceptable snubber was found.

b. Visual Examination Acceptance Criteria Visual examinations shall verify (1) that there are no visual indications of damage or impared operability, and (2) attachments to the foundation or supporting structure are secure. Snubbers which appear inoperable as a result of visual examinations may be determined OPERABLE for the purpose of establishing the next visual examination interval, providing that (1) the cause of the rejection is clearly established and remedied for that particular snubber and for other snubbers for that group, or (2) the affected snubber is functionally tested in the as-found condition and determined OPERABLE per Specification 4.7.8.d. When the fluid port of a hydraulic snubber is found to be uncovered or the fluid is less than the specified amount, the snubber shall be determined IN0PERABLE unless a test is performed to determine the snubber OPERABLE. Snubbers determined to be unacceptable shall be verified OPERABLE, restored to a known OPERABLE condition or replaced with known OPERABLE snubbers.

c. Functional Testing For the purpose of functional testing of safety related snubbers, the sample plan and resample plan should provide a confidence level of 95% that 90% to 100% of the snubbers are operable. Several sample plans are known to meet this criteria. These sample plans are listed, as options to allow latitude for continued investigation leading to the implementation of the most effective sample plan.

The NRC Regional Administrator shall be notified in writing of the option selected for implementation prior to the iniation of the functional testing program. If notice is not given prior to the initiation of the functional testing program, that option implemented in the most recent refueling outage shall be implemented.

SAMPLE PLAN (0PTIONS)

OPTION #1 During each refueling outage, a representative sample of 10%

of all snubbers listed in tables 3.7-4a and 3.7-4b shall be l functionaly tested either in place or in a bench test.

For the first sample tested, a sample which is representative of the snubber designs and installations shall be selected.

For each snubber failing-the functional test acceptance criteria, an additional sample lot of 1/2 the size of the initial lot, within the group represented by the failed snubber, shall be tested.

Testing shall continue within the representative group until no failures are found in subsequent sample lots or all units in the representative group have been tested.

At subsequent testing intervals, each representative sample shall consist of previously untested snubbers.

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i SURVEILLANCE RE0UIREMENTS (CONTINUED)

OPTION #2

During each refueling outage, a representative sample of at least 37 snubbers listed in Tables 3.7-4a and 3.7-4b shall be functionally tested. Additional testing shall be in accordance with Figure 4.7-1 which includes ccceptance and rejection criteria. "C" is the cumulative total number of snubbers found not meeting the functional test acceptance criteria. The cumulative number of snubbers tested is denoted by "N". At the end of each testing day, the new values of "N" and "C" shall be plotted on the Figure 4.7-1. If at any time the point plotted falls in the " Reject" region, all snubbers of that group shall be functionally tested.

If at any time the point plotted falls in the " Accept" region, testing of that group of snubbers shall be terminated. When the point plotted falls in the " Continue Testing" region, additional snubbers shall be tested until the point falls in the " Accept" region or the " Reject" region, or all the snubbers of that group have been tested.

OPTION #3 During each refueling outage, a representative sample of 55 snubbers listed in tables 3.7-4a and 3.7-4b shall be functionally tested. For each snubber failing the functional test acceptance criteria another sample of at least 1/2 the initial lot shall be tested until the total number tested is equal to the initial sample size multiplied by the factor, "I + C/2" where "C" is the number of snubbers found failing the functional test aceptance criteria. Another sample of at least 1/2 of the initial test lot shall be tested for each subsequent snubber deterrrined to fail the functional test acceptance criteria.

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.

For the purpose of functional testing, the hydraulic and mechanical snubbers will be considered as independent groups with sampling and testing criteria applied accordingly.

If it is determined by an engineering analysis that a series of unit i f ailures is unique to a certain group or model, then the sample quantities I need not exceed the total number of snubbers in that group.

Snubbers identified in tables 3.7-4a and 3.7-4b as "Especially Difficult To Remove" or in "High Radiation Zones During Shutdown" shall be included in the represent 8ive sample.

Inservice operability testing may be accomplished with the snubber installed in its permanent location by utilizing owner-approved test methods and equipment.

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SURVEILLANCE REOUIREMENTS (CONTINUED)

If. it is extermely difficult to utilize the conventional test methods, due to the physical size of the snubber or inaccessibility of location, the snubber subcomponents shall be examined and tested in accordance i with approved procedures. Reassembly ofindividual components must be

! in accordance with approved procedures.

The snubbers of parallel and multiple installation locations shall be identified and counted individually.

Snubbers shall not recieve prior maintenance specifically for the purpose of meeting an operablilty test requirement.

d. Functional Test Acceptance Criteria The snubber functional test shall verify that:

1. Activation (restraining action) is achieved within the specified range in both tension and compression, except that inertia-dependent, acceleration limiting mechanical snubbers may be tested to verify only that activation takes place in both directions of travel.

2. Snubber bleed rate for hydraulic snubbers, is present in both tension and compression, within the specified range.

3. For mechanical snubbers the force required to initiate or maintain motion of the snubber is not great eaough to overstress the attac.hed piping or component during thermal movement, or to indicate impending failure of the snubber.

4. Testing methods may be used which measure parameters indirectly or parameters other than those specified if those results can be correlated to the specified parameters through established methods.

e. Service Life Monitoring Program i

SNUBBER SERVICE LIFE MONITORING PROGRAM 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 in high radiation area, insnubber, seal replaced, high temperture area, spring) etc... . replaced, The requirement to monitor the snubber service life is included in Station Procedures 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 seal service life of hydraulic snubbers shall be monitored to ensure that the seals do not fail between surveillance examinations. The maximum expected service life for the various seals, seal materials, and applications shall be estimated based on engineerinc, information, and the seals 4

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.o SURVEILLANCE REQUIREMENTS (CONTINUED) shall be replaced so that the maximum expected service life does not expire during a period when the snubber is required to be operable. The seal replacements shall be documented and the documentation shall be retained in accordance with Station Procedures.

Mechanical snubber drag force increases greater than 50 percent of previously measured values shall be evaluated as an indication of impending failure of the snubber. These evaluations, and any associated corrective action such as, repair or replacement of the snubbers, shall be documented, and the documentation shall be retained in accordance with Station Procedures.

f. Exemption from Visual Examination or Functional Tests Permanent or other exemptions from the surveillance program for individual snubbers may be granted by the Commission if a justifiable basis for exemption is presented and, if applicable, snubber life destructive testing was performed to qualify snubber operability for the applicable design conditions at either the completion of their fabrication or at a subsequent date. Snubbers so exempted shall be listed in Table 3.7-4c.

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PLANT SYSTEMS 3/4.7.8 SNUBBERS BASES All snubbers included in this inspection program are required to be OPERABLE to ensure that no failure of a snubber could affect the function of a safety related plant feature to an unacceptable level during Seismic Category I events.

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 to replace or restore the inoperable snubber (s) to operable status and perform an engineering evaluation on the supported component or declare the supported system inoperable and follow the appropriate limiting condition for operation statement for that system. The engineering evaluation is performed to determine whether the mode of failure of the snubber has adversely affected any safety-related component or system.

The visual examination frequency is based upon maintaining a constant level of snubber protection to safety related systems. Therefore, the required examination interval varies inversely with the observed snubber failures and is determined by the number of inoperable snubbers found in a particular group during an examination period. Examinations performed before that period has elapsed may be used as a new reference point to determine the next examination. However, the results of such early examinations performed before the original required time period has elasped (nominal time less 25%) may not be used to lengthen the required examination period. An examination whose results require a shorter examination period will override the previous schedule.

When the cause of the rejection of a snubber or group of snubbers is clearly established and remedied for that snubber or group and verified by inservice functional testing, that snubber may be exempt from being counted as inoperable. Snubber groups are those which are of a specific make or model or have the same design features directly related to rejection of the snubber by visual examination, or are similarly located or exposed to the same enviromental conditions such as temperature, vibration, and radiation (hydraulic snubbers).

When a snubber is found inoperable, an engineering evaluation is performed in addition to the determination of the snubber mode of failure 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.

To further increase the assurance of snubber reliability, functional tests shall be performed during each refueling outage. These tests will include stroking of the snubbers to verify proper movement, activation, and bleed rate. The performance of hydraulic snubbers generally depends on a clean, deaerated fluid contained within variable pressure chambers, flowing at closely controlled rates. Since these characteristics are subject to change with exposure to the reactor environment, time, and other factors, their performance within the 1

BASES (CONTINUED) specified range should be verified. Mechanical snubbers which depend upon overcoming the inertia of a mass and the braking action of a capstan spring contained within the snubber for limiting the acceleration of the attached component (within the load rating of the snubber) are not subject to changes in performance in the same manner as hydralic snubbers.

Pending the development of information regarding the change during the service of the snubber of the acceleration / resistance relationship and the optimum method for detecting this change, these mechanical snubbers may be tested to verify that when subjected to a large change in velocity, the resistance to movement increases greatly. The performance change information is to be developed in order to establish test methods to be used during and af ter the first refueling outage.

Qualitative testing, therefore, may be used in lieu of quantitive measurements in meeting the requirements for functional testing, provided adequate justification can be presented and accepted for this position by the regulatory authority having jurisdiction over the factilty. In l those cases, the owner shall obtain sufficient data to justify, based upon service history of life cycle testing, the ability of the parameter in question to be within specification over the life of the snubber. For example, demonstration that activation takes place without measurement of the activation level. A test report shall be available for each snubber exempted from an inservice quantitative test requirement. The test report must verify the parameter was within specifications to allow exemption of the snubber from quantitative testing of the parameter.

When quantitative functional tests are performed on mechanical snubbers, the snubbers will be tested at loads greater than ten percent of rated load.

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