ML19345G413
| ML19345G413 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 04/03/1981 |
| From: | Maine Yankee |
| To: | |
| Shared Package | |
| ML19345G412 | List: |
| References | |
| NUDOCS 8104070195 | |
| Download: ML19345G413 (5) | |
Text
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.q.
v 3.20 Shock Suppressets (Snubbers)
Applicability: Applies to those shock suppressors used on the primary coolan' system and on other safety related systems or components.
Objective:
To define the condition of the above defink shock suppressor, required for reactor operation.
Specification:
A.
During all modes of operation except Cold Shutdown and Refueling, all safety-related snubbers listed on Table 3.20-1 shall be operable except as noted in 3.20.B and 3.20.C below.
B.
If any snubber listed in Table 3.20-1 is fotrd to be Inoperable, within 'i2 hours it must be repaired and made operable or be replaced with one which is operable, an1 an engineering evaluation of the supported component shall be p6rformed to determine if the components supported by the snubbar were adversely affected by the inoperability of the snubber in order to ensure that the supported component remains capable of meeting the designed service.
C_.
If the requirements of specification B cannot be met, an orderly shutdown shall be initiated, and the reactor shall be in the cold shutdown condition within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
D.
If a snubber is determined to be inoperable while the reactor is in the shutdown or refueling mode, the snuhber shall be made operable or replaced prior to reactor startup.
E_. Snubbers may be added to safety related systems provided that a revisicn to Table 3.20-1 is included with the next license amendment.
Basis:
Snubbers are designed to prevent unrestrained pipe motion under dynamic loads that might occur during an earthquake or severe transient while allowing aormal thermal motion during startup and shutdown.
The consequence of an inoperable i
snubber is an increase in the probability of structural damage to piping as a result of a seismic or other event initiating i
dynamic loads. -It is, therefore, required that all. snubbers l
required to protect the primary coolant system or any other safety related system or component be operable during reactor l
operation.
Because snubber protection is required only during 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 l
repairs or replacement and a determination that the senported component remains capable of meeting the designed service.
l l
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 shutdown condition will permit an orderly
. shutdown consistent with standard operating procedures. - Since plant startup should not commence with knowingly defective safety related equipment, Specification 3.20.D prohibits startup with inoperable snubbers.
I 3.20-1
- 810407 0 M u
4.9 Shock Suppressor (Snubber) Surveillance Applicability: Applies to the surveillance requirements for those hydraulic shock suppressors listed in Table 3.20-1.
Objective:
To verify the operability of all safety related hydraulic shock suppressors.
Specification:
A.
All hydraulic shock suppressors shall be visually Tnspected to determine operability in accordance with the following schedule:
tomber of Snubbers Next Required Found Inoperable During Inspection Inspection or During Interval Inspection Interval 0
18 Months + 25%
1 12 Months T 25%
2 6 Months 7 25%
3, 4 124 Days
- 25%
5,6,7 62 Days 1 25%
_8 31 Days 1 25%
The required inspection interval shall not be lengthened more than one step at a time.
Exception Snubbers which are determined to be inoperable through a visual inspection may be considered operable for the purpose of estaMishing the next visual inspection interval if (1) the cause of the rejection is clearly established and remedied for that particular snubber and others that may be generic &lly susceptible to the same cause and (2) the affected snubber is functionally tested in the as found condition and determined to be operable.
This exception does not apply when the fluid port of a hydraulic snubber is found to be uncovered.
Snubbers may be categorired into two groups, " accessible" or
" inaccessible" based on t'eir accessibility for inspection during reactor operation.
These two groups may be inspected independently according to the above schedule.
B.
This visual inspection shall include but not necessarily L limited to, inspection of the hydraulic-fluid reservoir, fluid connections, and linkage connections to the piping and anchor.
The inspection shall verify operability by determining (1) there are no visible indications of damage or impaired operability (2) there are no visible indications that the attachments to the foundation or supporting structure are not secure.
4.9-1
- v. _
C.
Once each refueling cycle, a representative sample of 10 hydraulic snubbers or approximately 1% of the hydraulic snubbers, whichever is less, shall be functionally tested for operability.
For each unit ard subsequent unit found inoperable, an additional 1 m or 10 hydraulic snubbers shall be so tested until no more failures are found, or all enits have been tested.
Selection of snubbers for inclusion in functional testing representative samples shall be accomplished in a manner which provides systematic inclusion of safety related snubbers in all categories of Table 3.20-1.
Ibwever, snubbers of rated capacity greater than 50,000 lb. need not be included in the functional testing program until the 1983 refueling outage test sample.
In addition to the regular sample, snubbers which failed the previous functional tut 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 snuober shall be retested.
Test results of these snubbers may not be included for the resampling.
D_.
The functional test shall verify operability by determining that (1) Activation (restraining action) is achieved within the specified range of velocity or acceleration in both tension and compression and (2) snubber bleed, or release rate, where required, is within the specified range in compression or tension, and (3) the snubber is able to withstand load without displacement for snubbers specifically required not to displace under continuous load.
E.
If a snubber fails the functional test by failing to move or lockup, the cause of the failure will be investigated.
If the cause is determined to result from a design or manufacturing deficiency all snubbers of the same design subject to the same. deficiency shall be functionally tested.
Basis:
All safety related hydraulic snubbers are visually inspected for overall integrity and operability.
The inspection will include verification of proper orientation, adequate hydraulic fluid level and proper attachment of snubber to piping and structures.
The inspection frequency is based upon maintaining a constant level of snubber protection.
Thus the required inspection interval varies inversely with the observed snubber failures.
The number of inoperable snubbers 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. Never, the results of such early inspection performed before the original required time interval:
4.9-2 m
has elapsed (nominal time less 25%) may not be used to lengthen the required inspection interval. My inspection whose results require a shorter inspection interval will override the previous schedule.
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. Cbserved failures on these samples should require testing of additional units.
Snubbers of rated capacity greater than 50,000 lb. are exempt from the functional testing requirements until a practical method can be developed for performance of functional testing of these large snubbers either in place or in a bench test at less than rated capacity.
l (1) Report H. R. Erickson, Bergen Paterson to K. RO Galler, NRC, October. 7,
- 1974
Subject:
Hydraulic Shock Sway Arrestors 4.9-3
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a,
- i. Records of in-service inspections performed pursuant to these Technical Specifications.
J. Records of Quality Assurance activities required by the QA
. Manual.
k.
Records of reviews performed for changes made to
- procedures or equipment or reviews of tests and experiments pursuant to 10 CFR 50.59.
1.
Records of meetings of the PORC ar)d the NSAR Committees.
- m. ' Records of Environmental Qualification which are covered under the provisions of paragraph 5.13.
- n.. Records of the service lives of all snubbers listed on Table.3.20-1 including the date at which the service life commences and associated installation and maintenance
. records.
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