ML20067D255
| ML20067D255 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 02/04/1991 |
| From: | SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | |
| Shared Package | |
| ML20067D254 | List: |
| References | |
| TSP-910003, TSP-910003-0, NUDOCS 9102130007 | |
| Download: ML20067D255 (13) | |
Text
_
- to Document Control Desk Letter TSP 910003-0 PROPOSED TECHNICAL SPECIFICATION CHANGE TSP-910003-0 VIRGIL C. SUMMER NUCLEAR STATION LIST OF AFFECTED PAGES EARe 3/4 7-16 3/4 7-17 3/4 7-18 3/4 7-20 3/4 7-21 3/4 7-22 8 3/4 7-4 8 3/4 7-5 4
910213oo07 910204 ADOCK0500g;95 PDR P
PLANT SYSTEMS 3/4.7.7 SNUBBERS MMITINGCONDITIONFOROPERATION 3.7.7 All snubbers on systems required for safe shutdown / accident mitigation shall be OPERABLE.
This includes safety and non-safety related snubbers on systems used to protect the code boundary and to ensure the structural integ-rity of these systems under dynamic loads.
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 srubbers 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 per Specification 4.7.7.g on the attached component or declare the attached system inoperable and follow the appropriate ACTION statement for that system.
SURVEILLANCE REQUIREMENTS 4.7.7 Each snubber shall be demonstrated OPERABLE by performance of the
-following augmented inservice inspection program and the requirements of Specification 4.0.5.
a.
Inspection Types As used in this specification, type of snubber shall mean snubbers
/
of the same design and manufacturer, irrespective of capacity, b.
Visual Inspections p
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'The first inservice visual inspection of each type of snub 11 h
e formed after 4 months but within 10 months of c cing POWER OPERA and shall include all snubbers defined ection 3.7.7.
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If less t two snubbers of each type are fo
'noperable during the first ins ice visual inspection,_the and inservice visual j
inspection shall performed 12 months 5% from the date of the first inspection.
erwise, subse
_t visual inspections shall be performed in accordanc with th lowing schedule:
No. Inoperable Snubbe f'each Subsequent Visual
}
Inspection Period *y type per Inspectio er 0
N' 18 months 2 25%
1 12 months 2 25%
i 6 months t 25%
3,4 124 days i 25%
5,6,7 62 days t 25%
8 or more days t 25%
"The inspec on interval for each type of snubber shall n be lengthened more th one step at a time unless a generic problem has b identified and rected; in that event the inspection interval may be len ened one st the first time and two steps thereafter if no inoperable snubb of at type are found.
provjsions of Spe g cation 4.0.2 are not applicable.
SUMER - UNIT 1 3/4 7-16 Amendment Ho. 41
.b D ais e r 4 7 7 6
INSERT 4.7.7.-b.
Snubbers are categorized as accessible or inaccessible during power operation.
Each of these categories may be inspected independently according to the schedule determined by Table 4.7-2.
The visual inspection interval for each type of snubber shall be determined based on the :;riteria provided in Table 4.7-2.
INSERT 4.7.7 d.
unacceptable for determining the next inspection interval. A review and evaluation shall be performed and documented to justify continued coeration with an unacceptable snubber'.
If continued operation can not be justified, the snubber shall be declared inoperable, c
7 4
PLANT SYSTEMS SURVEILLANCE REQUIREMENTS (Continued) c.
Refueling Outage Inspections EacA,pc/arfugvufp lo n~ nth-nspection shall be performed of all ioni m.
g.,
thesnubbersdefinedinSeclion3.7.7attachedtosectionsofsafety l
no systems piping that have experienced unexpected, potentially damaging transients as determined from a review of operational data and a visual inspection of the systems.
In addition to satisfying the visual inspection acceptance criteria, freedom of motion of mechanical snubbers shall be verified using at least one of the following:
(i) manually induced snubber movement; (ii) evaluation of in place snubber piston setting; or (iii) stroking the mechanical snubber through its full range of travel, d.
Visual Inspection Acceptance Criteria Visual inspections shall verify (1) that there are no visible indications of damage or impaired OPERABILITY and (2) attachments to the foundation or supporting structure are secure.. Snub)ers which) appear inoperable as a result of visual inspections M
'* da+- - -4 OT:IJCLC-for the purpose of establishing the next shual inspection { ( '
interval, provided that (1) the cause of the rejection is clearly h
established and remedied for that particular snubber and for other I,
snubbers irrespective of type that may be generically susceptible;.
y and (2) the affected snubber is functionally tested in the as found i
i condition and determined OPERABLE per Specifications 4.7.7.f.
When a fluid port of a hydraulic snubber is found to be uncovered the snubber shall be declared inoperable and shall not be determined t
i OPERABLE via functional testing unless the test is started with the piston in the as found setting, extemiing the piston rod in the 1
tension mode direction.
All snubber 'onnected to an ing erable I
common hydraulic fluid reservoir sha becountedafu;mm:
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Functional Tests Dur'ing the first refueling shutdown and at least once per 18 months thereaf ter during shutdown, a representative sample of either:
(1) At least 10I. of the total of-each type of snubber in use in the
'L plant shall be functionally tested either in place or in a bench test.
For each snubber of a type that does not meet the functional test acceptance criteria of Specification 4.7.7.f, an additional 10% of that type of snubber shall be functionally tested until no more failures are found or until all snubbers of that type have been functionally tested, or (2)'A representative sample of each type of snubber shall be functionally tested in,accordance with Figure 4.7-1, "C" is the total number of snubbers of a type found not meeting tha acceptance requirements of Specification 4.7.7.f.
The cumulative number of snubbers of a type tested is denoted by "N."
At the end of each day's testing, the new values of "H" and "C" (previous day's total plus current c'ay's increments) shall be i plotted on Figure 4.7 1.
Ii os L-s Lm r ;n g i -, T 1,.r ony in thc "P, eject" re@n all enwbbe,. # 'het tns.n.1 um f=ctic=11y tut:S If at any time the point plotted falls in SUMMER - UNIT 1 3/4 7-17 Amendment No. 41
PLANT SYSTEMS SURVEILLANCE REQUIREMENTS (Continued) e.
Functional Tests (Continued) the " Accept" region testing of that type of snubber may be terminated. When the point plotted lies in the " Continue Testing" region, additional snubbers of that type shall be tested until the point falls in the " Accept" region - " ""-j- '" -^f-or all d
the snubbers of that type have been tested.
The representative sample selected for functional testing shall include the various configurations, operating environments, and the range of size and capacity of snubbers of each type. The represen-tative sample shall be weighted to include more snubbers from severe service areas such as near heavy equipment.
Snubbers placed in the same location as snubbers which failed the previous functional test shall be included in the next test lot if the failure analysis shows that failure was due to location, f.
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
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2.
Snubber bleed, or release rate where required, is present in both tension and compression, within the specified range.
3.
Where required, the force required to initiate or maintain motion of the snubber is within the specified range in both direction of travel.
4.
For snubbers specifically required not to displace under continuous load, the ability of the snubber to withstand load without displacement.
5.
Fasteners for attachment of the snubber to the component and to the snubber anchorage are secure.
Testing methods may be used to measure parameters indirectly or parameters other than those specified if those results can be correlated to the specified parameters through established methods, g.
Functional Test Failure Analysis An engineering evaluation shall be made of each failure to meet the functional test acceptance criteria to determine the cause of the failure.
The results of this evaluation shall be used, if applicable, in selecting snubbers to be tested in an effort to determine the OPERALILITY of other snubbers irrespective of type which may be subject to the same failure mode.
SUPNER - UNIT 1 3/4 7-18
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l FIGURE 4. 7-1 SAMPLING PLAN FOR SUNBBER FUNCTIONAL TEST l
SUMMER - UNIT 1 3/4 7-20
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TABLE 4.7-2 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' S
12 25 400 8
18 36 500 12 24 48
~750 20 40 78 29 56 109
.1000 or greater TABLE NOTATION (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 internal. Snubbers may be categorized, based upon their accessibility during power operation, j
as accessible or inaccessible. These categories may be examined p
separately or jointly. However, the licensee must make and document-that L
decision before any inspection and shall use that decision as the basis upon which to detennine the next inspection interval for that category.
(2)
Interpolation between population or category si2es e d the number of unacceptable snubbers is permissible. Use next lower (nteger for the value of the, limit for Columns A, B, or C if that includes a fractional value of l_
unacceptable snuchers as determined by interpolation.
1 (3)~
If the number of ur: acceptable soubbers 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 toonths.
(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 i
interval shall be the same as the previous interval.
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SUMMER - UNIT 1 3/4 7-21 t
. _, _ _. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _l
SNUBBERS TABLE 4.7-2 (CONTINUED)
TABLE NOTATION (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.
(6)
The provisions of Specification 4.0.2 are applicable for all inspection intervals up to and including 48 months.
I-l SUMMER - UNIT 1 3/4 7-22
PLANT SYSTEMS BASES T
SNUBBERS (Continued)
To provide assurance of snubber functional reliability one of two sampling and acceptance criteria methods are used:
1) functionally test 10 percent of a type of snubber with an additi.onal 10 percent tested for each functional testing failure, or 2) functionally test a sample size and determine sample acceptance ee---
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= 7;';;t'a, using Figure 4.7-1.
Figure 4.7-1 was developed usinD "Wald's Sequential Probability Ratio Plan" as described in " Quality Control anu Industrial Statistics" by Acheson J. Duncan.
The service life of a snubber is established 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 temperatere area, etc...).
The requirement to monitor the snubber service life is included to ensure that the snubbers p6riodically undergo a performance evaluation in view of their ane 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.
Permanent or other exemptions from the surveillance program for individual snubbers may be granted by the Commission if a justifiable basis for exemption is presenteu and, if applicable, snubber life destructive testing was performed to qualify the snubber for the applicable design conditions at either the 1
completion of their fabrication or at a subsequent date.
Snubbers so exempted shall be listed in Section 3.7.7 with footnotes indicating the extent of the exemptions.
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SUMMER - UNIT 1 B 3/4 7-5 Amendment No. 41 l
ll PLANT SYSTEMS BASES ULTIMATE HEAT SINK (Continued)
The limitations on minimum water level and maximum temperature are based on providing a 30 day cooling water supply to safety related equipment without exceeding their design basis temperature and is consistent with the recommendations of Regulatory Guide 1.27, " Ultimate Heat Sink for Nuclear
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Plants", March 1974.
3/4.7.6 CONTROL ROOM NORMAL AND EMERGENCY AIR HANDLING SYSTEM The 06ERABIL:TY of the control room ventilation system ensures that
- 1) the ambiet air temperature does not exceed the allowable temperature for continuous duty rating for the equipment and instrumentation cooled by this system and 2) the control room will remain habitable for operations personnel during and following d i credible accident conditions.
The OPERABILITY of this system in conjunction with control room design provisions is based on limiting the radiation exposure to personnel occupying the control room to 5 rem or less whole body, or its equivalent.
This limitation is consistent with the requirements of General Design Criteria 19 of Appendix "A",10 CFR 50.
3/4.7.7 SHUBBERS A M snubbers on systems required for safe shutdown / accident mitigation shall be OPERABLE.
This includes safety and non-safety related snubbers on systems used to protect the code boundary and to ensuro the structural integrity of these systems under dynamic loads.
Snubbers are classified and grou:*d by design and manufacturer but not by size.
For cxample, mechanical snubbe-utilizing the same design features of the 2 kip,10 'do and 100 kip capacity manufactured by company "A" are of the same type.
The same design mechanical snubber manufactured by company "B" for the purposes of this specification would be of a different type, as would hydraulic snubbers from either manufacturer.
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.IInspectionr-performed before that interval has elapsed may be used as a newWference
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Any inspection whose results require a shorter inspection interval will._ override the previous schedule.
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SUMP.R - UNIT 1 B 3/4 7-4 Amendment No. 41
' to Document Control Desk Letter
- 1
-TSP 910003-0 Page 1 of 1 PROPOSED TECHNICAL SPECIFICATION CHANGE - TSP 910003-0 VIRGIL C. SUMMER NUCLEAR STATION DESCRIPTION AND SAFETY EVALVATION DESCRIPTION OF CHANGE SCE&G proposes to modify the Virgil C. Summer Nuclear Station Technical Specifications (TS) to revise TS 4.7.7 and associated Bases 3/4.7.7 in accordance with GL 90-09; additionally, the REJECT line in figure 4.7-1 and all references to this line are _ deleted f rom the text. The proposed amendment changes the snubber visual inspection schedule of surveillance requirement 4.7.7 to the alternste visual inspection schedule specified by GL 90-09,'and. changes the associated Bases 3/4.7.7.
I 1
SAFETY EVALUATION z
' Snubbers are designed to prevent unrestrained motion of piping systems and
-components under dynamic loading, while allowing normal thermal expansion and contractions to occur during plant-startup, operation, and shutdown. The
-proposed changes do not. involve any change to the plant configuration or its mode of operation as described.in the safety analysis report.
Existing safety analyses and safety assumptions are not affected nor need to be changed. All snubbers and related components will continue to be visually and functionally inspected; therefore..their operability will not be affected. Deletion of the Reject line from figure 4.7-1 and its references in the text are needed to reflect actual testing strategy. The use of the Reject line is incorrect since this line assumes a totally homogeneous sample and that the failures of the total population are in the same ratio as the failures in the selected sample, a-
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' to Document Control Desk Letter n
TSP 910003-0 Page 1 of 2 PROPOSED TECHNICAL SPECIFICATION CHANGE - TSP 910003-0 VIRGIL C. SUMMER NUCLEAR STATION DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION DESCRIPTION OF CHANGE SCE&G proposes to modify the Virgil C. Summer Nuclear Station *.ichnical j
Specifications (TS) to revise TS 4.7.7 and associated Bases 3/4.7.7 in accordance with GL 90-09 additionally, the REJECT line in figure 4.7-1 and all. references to this line are deleted from the text. The proposed amendment changes the snubber visual inspection schedule of surveillance requirement 4.7.7 to the alternate visual inspection schedule specified by GL 90-09, and changes the associated Bases 3/4.7.7.
J SIGNIFICANT HAZARDS EVALVATION SCE&G has evaluated.the proposed technica.1 specification change and has determined that it does not represent a significant bazard consideration based on the criteria established in.10 CFR 50.92. Operation of Virgil C.
Summer Nuclear Station in accordance with the porposed ammendment will not:
(1)-
involve a-sighificant increase in the probability or consequences of an accident previously evaluated.
The proposed change will allow extension of subsequent visual surveillance intervals based on the number of unacceptable snubbers found during the previous inspection,:in accordance with the guidance contained in GL 90-09. This change will not involve any change to the
. actual surveillance requirements. There will be no increase in the probability.of failure of components and sytems that would result from l
extending the visual surveillance interval. Reliability is ensured by functional testing which provides a 95 percent confidence level that 90 t
I to 100 percent of the snubbers will operate within their specified-acceptance limit.
The Reject-line, developed using Wald's Sequential Probability Ratio Plan, assumes that the sample i totally homogeneous, and that the g
l' failure in.the total population is in the same ratio as the failures L
observed-in a given sample, This is not correct when functionally testing snubbers in nuclear power stations. Snubbers can not be
- considered a homogeneous population, since the sampling for functional testing includes various configurations, different environmental conditions, different sizes, capacities and types of snubbers, and the sample is weighted to include more snubbers from severe service areas.
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. to Document Control Desk Letter TSP 910003-0 Pege 2 of 2 (2) create the possibility of a new or lfferent kind of accident from any previously analyzed.
The proposed change will not make physical alterations to any plant system, structure or component, will not change the method by which a safety-related system performs its function, and will not change the way the surveillance requirement is performed. The proposed change will only allow extension of a subsequent snubber visual inspection if the number of unacceptable snubbers found during a given inspection is equal or less than the number of unacceptable snubbers given in the new SNUBBER VISUAL INSPECTION INTERVAL table. Deletion of the Reject line from figure 4.7-1 does not contribute to any new or different kind of accident.
(3) involve a significant reduction in a margin of safety.
The proposed change will not alter existing surveillance requirements; therefore, the reliability, ensured through functional testing, will not be degraded. Visual examinations complement the functional testing of snubbers and provide additional confidence of snubber reliability.
VCSNS operating experience indicates that. existing maintenance programs are effective in minimizing snubber failures, as demonstrated by the low snubber failure rate experienced. During VCSNS' most recent inspection, eight snubbers were found unacceptable by visual inspection out of a total population of 1127 TS snubbers. These unacceptable snubbers were subsequently tested, root cause anlyses were performed, corrective actions were taken, and were later declared acceptable.
Deletion of the Reject line in Figure 4.7-1 does not contribute to e.y reduction in the margin of safety.
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