NRC Generic Letter 1984-13
UNITED STATES
toNUCLEAR
l REGULATORY COMMISSION
WASHINGTON, D. C. 20555 May 3, 1984 To All Power Reactor Licensees (Except SEP Licensees) And All Applicants For Licenses To Operate Power Reactors Subject: Technical Specification For Snubbers (Generic Letter 84-13)
For several years a technical specification for snubbers has been included in the technical specifications for new facility operating licenses. A model specification was transmitted to power reactor licensees as Revision 1 of the Surveillance Requirements for snubbers by an enclosure to my Generic Letter of November 20, 1980.
During the last several years, a large number of license amendments have been required to add, delete or modify the snubber listing within the technical specifications. We have reassessed the inclusion of snubber listings within the technical specifications and conclude that such listings are not necessary provided the snubber technical specification is modified to specify which snubbers are required to be operable. You should also note that the record- keeping requirements of paragraph 4.9.7.f. of the snubber technical speci- fication are not altered by this revision. Paragraph 4.9.7.f. requires that the plant records contain a record of the service life, installation date, etc. of each snubber. Since any changes in snubber quantities, types, or locations would be a chance to the facility, such changes would be subject to the provisions of 10 CFR Part 50.59 and, of course, these changes would have to be reflected in the records required by paragraph 4.7.9.f.
Enclosed is a revision to Revision 1 of the Surveillance Requirements which was attached to my Generic Letter of November 20, 1980. This revision is limited to a modification to Specification 3.7.9 to specify which snubbers are subject to the requirements of this technical specification and to the elimination of Tables 3.7-4a and 3.7-4b. Specification 3.7.9 now includes as part of the Limiting Condition for Operation the same criterion as was in the bases section of my November 20, 1980 Generic Letter. This criterion states that all snubbers other than specified exceptions are required to be operable. The requirement in Specification 3.7.9 of Revision 1, that snubbers be listed in Tables 3.7-4a and 3.7-4b is no longer necessary and is eliminated by this revision.
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-2- No change in existing technical specifications that include a list of snubbers to is required. However, a licensee may choose to request a license amendment delete the tabular listing of snubbers from its technical specifications.
Unless and until deleted, the list of snubbers shall be maintained in accordance with the requirements of Revision 1 of the Surveillance Requirements for snubbers that was enclosed with my Generic Letter of November 20, 1980.
A few recently issued licenses have included technical specifications without tabular listings of snubbers. This revision will be applied to future operating licenses and the technical specifications will not include lists of snubbers.
Sincerely, G. enhut, Director Division of L'censing Enclosure:
Revised Model Te hnical Specification r Snubbers cc: w/enclosure I
ENCLOSURE
PLANT SYSTEMS
3/4.7.9 SNBERS
LIMITING CONDITION FOR OPERATION
3.7.9 All snubbers shall be OPERABLE. The only snubbers excluded from this requirement are those installed on nonsafety-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.
APPLICABILITY: MODES 1, 2, 3 and 4 (MODES 5 and 6 for snubbers located in systems required OPERABLE in those MODES).
ACTION:
With one or more snubbers inoperable, witjiin 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 per Specification 4.7.9.c on the supported component or declare the supported system inoperable and follow the appropriate ACTION statement for that system.
SURVEILLANCE REQUIREMENTS 4.7.9 Each snubber shall be demonstrated OPERABLE by performance of the following augmented inservice inspection program and the requirements of Specification 4.0.5.
a. Visual Inspections The first inservice visual inspection of snubbers shall be performed after four months but within 10 months of commencing POWER OPERATION
and shall include all snubbers. If less than two (2) snubbers are found inoperable during the first inservice visual inspection, the second inservice visual inspection shall be performed 12 months +/- 25%
from the date of the first inspection. Otherwise, subsequent visual inspections shall be performed in accordance with the following schedule:
No. Inoperable Snubbers Subsequent Visual per Inspection Period Inspection Period*#
18 months +/- 25X
1 12 months +/- 25%
2 6 months +/- 25%
3,4 124 days +/- 25%
5,6,7 62 days +/- 25%
8 or more 31 days +/- 25%
The snubbers may be categorized into two groups: Those accessible and those inaccessible during reactor operation. Each group may be inspected independently in accordance with the above schedule.
- The inspection interval shall not be lengthened more than one step at a tine.
- The provisions of Specification 4.0.2 are not applicable.
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PLANT SYSTEMS
SURVEILLANCE REQUIREMENTS (Continued)
b. Visual Inspection Acceptance Criteria Visual inspections shall verify (1) that there are no visible indica- tions of damage or impaired OPERABILITY, (2) attachments to the foundation or supporting structure are secure, and (3) 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. Snubbers which appear inoperable as a result of visual inspections may be determined OPERABLE for the purpose of establishing the next visual inspection interval, providing that
(1) the cause of the rejection is clearly established and remedied for that particular snubber and for other snubbers that may-be generically susceptible; and (2) the affected snubber is functionally tested In the as found condition and determined OPERABLE per Specifi- cations 4.7.9.d or 4.7.9.e, as applicable. However, when the fluid port of a hydraulic snubber is found to be uncovered, the snubber shall be determined inoperable and cannot be determined OPERABLE via functional testing for the purpose of establishing the next visual inspection interval. All snubbers connected to an inoperable common hydraulic fluid reservoir-shall be counted as inoperable snubbers.
c. Functional Tests At least once per 18 months during shutdown, a representative sample
(10% of the total of each type of snubber in use in the plant shall be functionally tested either in place or in a bench test. For each snubber that does not meet the functional test acceptance criteria of Specification 4.7.9.d or 4.7.9.e, an additional 10% of that type of snubber shall be functionally tested).
or (that number of snubbers which follows the expression 35 [l + C]
where c* is the allowable number of snubbers not meeting the The value c will be arbitrarily chosen by the applicant and incorporated into the expressions for the representative sample and for the resample prior to the issuance of the Technical Specifications. The expressions are intended for use in plants with larger numbers of safety-related snubbers (>500) and provide a confidence level of approximately 95% that 90% to 100% of the snubbers in the plant will be OPERABLE within acceptable limits. That is, the confidence level will be provided no matter what value is chosen for c.
It is advised, however, that discretion be used when initially choosing the value for c because the lower the value of c (the lower the amount of snubbers in the representative sample), the higher the amount of snubbers required in the re-sample will be. To illustrate: If c = 2 and 3 snubbers are found not to meet the functional test acceptance criteria, there will be
70 snubbers in the representative sample and 31 snubbers required for testing in the re-sample; If c = 2 and 4 snubbers fail the functional test, there will be 70 snubbers in the representative sample and 62 snubbers required for testing in the re-sample; If c = 0 and 1 snubber fails the functional test, there will be 35 snubbers in the representative sample and 140 snubbers required for testing in the re-sample; If c = 0 and 2 snubbers fail the functions test, there will be 35 snubbers in the representative sample and
280 snubbers required for testing in the re-sample.
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7i-.
PLANT SYSTEMS
SURVEILLANCE REQUIREMENTS (Continued)
acceptance critetia selected by the operator, shall be functionally tested either in-place or in a bench test. For each number of snubbers above c which does not meet the functional test acceptance criteria of Specifications 4.7.9.d. or 4.7.9.e, an additional sample selected according to the expression 35 (1 + 2) (c 2 )2 (a - c)
shall be functionally tested, where a is the total number of snubbers found inoperable during the functional testing of the representative sample.
Functional testing shall continue according to the expression b [35(1 + 2) (c 2 )2 where b is the number of snubbers found inoperable in the previous re-sample, until no additional inoperable snubbers are found within a sample or until all snubbers have been -functionally tested}.
The representative sample selected for functional testing shall include the various configurations, operating environments and the range of size and capacity of snubbers. At least 25% of the snubbers in the representative sample shall include snubbers from the following three categories:
1. The first snubber away from each reactor vessel nozzle
2. Snubbers within 5 feet of heavy equipment (valve, pump, turbine, motor, etc.)
3. Snubbers within 10 feet of the discharge from a safety relief valve Snubbers that are especially difficult to remove or in high radiation zones during shutdown shall also be included in the representative sample.*
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 re-sampling.
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.
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PLANT SYSTEMS
BASES
3/4.7.9 SNUBBERS
Snubbers are provided 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.
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 adversly 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 provide assurance of snubber functional reliability, a representative sample of the installed snubbers will be functionally tested during plant shutdowns at 18 month intervals. Selection of a representative sample according to the expression 35 (1 + ') provides a confidence level of approximately 95% that 90% to 100% of the snubbers in the plant will be OPERABLE within acceptance limits.. 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.
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PLANT SYSTEMS
BASES
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.
3/4.7.10 SEALED SOURCE CONTAMINATION
The limitations on removable contamination for sources requiring leak testing, including alpha emitters, is based on 10 CFR 70.39(c) limits for plutonium. This limitation will ensure that leakage from byproduct, source, and special nuclear material sources will not exceed allowable intake values.
Sealed sources are classified into three groups according to their use, with surveillance requirements commensurate with the probability of damage to a source in.that group. Those sources which are frequently handled are required to be tested more often than those which are not. Sealed sources which are continuously enclosed within a shielded mechanism (i.e. sealed sources within radiation monitoring or boron measuring devices) are considered to be stored and need not be tested unless they are removed from the shield mechanism.
3/4.7.11 FIRE SUPPRESSION SYSTEMS
The OPERABILITY of the fire suppression systems ensures that adequate fire suppression capability is available to confine and extinguish fires occurring in any portion of the facility where safety related equipment is located. The fire suppression system consists of the water system, spray and/or sprinklers, CO Halon, fire hose stations, and yard fire hydrants.
The collective capability of the fire suppression systems is -adequate to minimize potential damage to safety related equipment and is a major element in the facility fire protection program.
In the event that portions of the fire suppression systems are inoperable, alternate backup fire fighting equipment is required to be made available in the affected areas until the inoperable equipment is restored to service. When the inoperable fire fighting equipment is intended for use as a backup means of fire suppression, a longer period of time is allowed to provide an alternate means of fire fighting than if the inoperable, equipment is the primary means of fire suppression.
The surveillance requirements provide assurance that.the minimum OPERABILITY requirements of the fire suppression systems are met. An allowance is made for ensuring a sufficient volume of Halon in the Halon storage tanks by verifying either the weight or the level of the tanks. Level measurements are made by either a U.L. or F.M. approved method.
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A:4 I
4'LANT SYSTEMS
SURVEILLANCE REQUIREMENTS (Continued)
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 snubbers not meeting the functional test acceptance criteria.
For the snubber(s) found inoperable, an engineering evaluation shall be performed on the components which are supported by the 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 The hydraulic snubber functional test shall verify that:
1. Activation (restraining action) is achieved within the specified range of velocity or acceleration in both tension and compression.
2. Snubber bleed, or release rate, where required, is within the specified range in compression or 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 The mechanical snubber functional test shall verify that:
1. 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.
2. Activation (restraining action) is achieved within the specified range of velocity or acceleration in both tension and compression.
3. Snubber release rate, where required, is within the specified range in compression or tension. For snubbers specifically required not to displace under continuous load, the ability of the snubber to withstand load without displacement shall be verified.
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PLANT SYSTEMS
SURVEILLANCE REQUIREMENTS (Continued)
f. Snubber Service Life Monitoring A record of the service life of each snubber, the date at which the designated service life commences and the installation and mainte- nance records on which the designated service life is based shall be maintained as required by Specification 6.10.2.1.
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 recon- ditioned so as to extend its service life beyond the date of the next scheduled service life review. This reevaluation, replace- ment or reconditioning shall be indicated in the records.
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V4-I
'.ADMINISTRATIVE CONTROLS
e. Records of changes made to the procedures required by Specification
6.8.1..
f. Records of radioactive shipments.
g. Records of sealed source and fission detector leak tests and results.
h. Records of annual physical inventory of all sealed source material of record.
6.10.2 The following records shall be retained for the duration of the Unit Operating License:
a. Records and drawing changes reflecting unit design modifications made to systems and equipment described in the Final Safety Analysis Report.
b. Records of new and irradiated fuel inventory, fuel transfers and assembly burnup histories.
c. Records of radiation exposure for all individuals entering radiation control areas.
d. Records of gaseous and liquid radioactive material released to the environs.
e. Records of transient or operational cycles for those unit components identified in Table 5.7-1.
f. Records of reactor tests and experiments.
g. Records of training and qualification for current members of.the unit staff.
h. Records of in-service inspections performed pursuant to these Technical Specifications.
i. Records of Quality Assurance activities required by the QA Manual.
j. Records of reviews performed for changes made to procedures or equip- ment or reviews of tests and experiments pursuant to 10 CFR 50.59.
k. Records of meetings of the (URG) and the (CNRAG).
1. Records of the service lives of all hydraulic and mechanical snubbers including the date at which the service life commences and associated installation and maintenance records.
m. Records of secondary water sampling and water quality.
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