IR 05000352/1993005
| ML20034F093 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 02/12/1993 |
| From: | Carrasco J, Gray E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20034F055 | List: |
| References | |
| 50-352-93-05, 50-352-93-5, 50-353-93-05, 50-353-93-5, NUDOCS 9303020263 | |
| Download: ML20034F093 (8) | |
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U.S. NUCLEAR REGULATORY COMMISSION
REGION I
REPORT / DOCKET NOS. 50-352/93-05 50-353/93-05 LICENSE NOS.
NPF-39 NPF-83 LICENSEE:
Philadelphia Electric Company Post Office Box A Sanatoga, Pennsylvania 19464 FACILITY NAME:
Limerick Generating Station, Units 1 & 2 INSPECTION AT:
Chesterbrook and Sanatoga, Pennsylvania INSPECTION DATES:
Jan -
25-29, 1993
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INSPECTOR:
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J. E@, Reactor Engineer, Date Materials Section, EB, DRS h 8/9
) -/S - 73 APPROVED BY:
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E H'arold Gray, Chief, Apiterials section, Date '
Engineering Branch, DRS Areas Insnected: A safety inspection was conducted to determine whether the licensee's design, installation, and modification of safety related dynamic pipe restraints (DPRs) and static (rigid) pipe supports were performed in accordance with regulatory requirements,
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engineering specifications and properly documented instructions. Furtherrnore, it was determined whether the snubber surveillance was performed as required by 10 CFR'
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50.55a(g) and the Technical Specification (TS), the ASME Code Section XI, Inservice Inspection / Inservice Testing (ISI/IST) and license commitments.
i 9303020263 930218 PDR ADOCK 05000352 G
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2 Results: The design of the selected supports was adequate, properly' controlled and the configuration ofindividual supports was maintained current, with the exception of an apparent drafting error that is being corrected by the licensee's engineering staff.
It was emphasized that there is a need to establish a solid root cause investigation.to prevent further failure of snubbers due to dry grease. Replacing snubbers upon failure does not constitute a comprehensive corrective action. The licensee' stated that it will initiate a root -
cause analysis to begin a comprehensive corrective action. - This is an Unresolved item No.
93-05-01, pending the NRC review of the licensee's corrective action. A functional test at Unit 2 was conducted with state-of-the art technology in a controlled environment and by qualified individuals. Additionally, the record keeping was found to be computerized and in compliance with the Technical Specification.
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1.0 PURPOSE AND SCOPE The purpose of this inspection was to determine whether the licensee's design, installation, and modification of safety related dynamic pipe restraints (DPRs) and static (rigid) pipe supports were performed in accordance with regulatory requirements, engineering _
specifications and properly documented instructions. Furthermore, it was to determine -
l whether the snubber surveillance was performed as required by 10 CFR 50.55a(g) and the Technical Specification (TS), the ASME Code Section XI, Inservice Inspection (ISI/IST) and license commitments.
2.0 DESIGN AND DESIGN MODIFICATION OF PIPE SUPPORTS I
Revie.w of Selected Samole of Pine Suonorts During a system walkdown, the inspector selected the pipe supports of the residual heat removal (RHR) system for review of critical design attributes.
I Piping Revision Piping System Support No.
Support Type Isometric No.
Drawing No.
Snt ber
GBB-216-1
RHR, Reactor GBB-216-H29 Building-Unit 2 GBB-216-H26 -
Snubber GBB-216-H30 Variable
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Strut GBB-216-2
RHR, Reactor
. GBB-216-H3 Strut Building Unit 2 GBB-216-H4 -
Variable GBB-216-H5 Rigid Shock &
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Sway Arrestor The piping isometric drawings were accurate in terms of piping configuration, number of supports and general location of the individual support. In addition, the selected pipe supports were verified for geometric configuration, orientation and general key dimensions.
The inspector verified that the proper magnitude and orientation of the resultant loads from stress problem No. 2-10-86 were properly used in the design of these pipe supports. The geometric configuration of individual supports was verified by comparing the as-built drawing with the as-designed drawing. In addition, for the computer aided pipe support calculations using "STRUDL" computer program, the analytical model was checked to verify the accuracy of the geometric configuration, material properties, and input loads. A spot
check was performed on key numerical values of a limited sample of the hand calculations to verify that the resultant stresses were within the pertinent code allowable limits.
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Findings The inspector found the reviewed key design attributes acceptable. Ibwever, the inspector found a discrepancy in the location of penetrations P013 and P038 on isometric GBB-216-1.
The penetration numbers were reversed on isometric GBB-216-1. This finding was confirmed by the licensee to te correct by reviewing drawing PSA-712-2. The licensee was udvid of the finding and after their investigation, an action request was generated to correct the drafting error of Isometric GBB-216-1.
Conclusion Based on the review of a sample of safety related supports, as is described above in a tabular form, the inspector concluded that their design was adequate, properly controlled and the configuration of individual supports was maintaine<' current, with the exception of the apparent drafting error that is being corrected by the licensec's engineering.
3.0 ISI/'ST SNUBBER SURVEILLANCE PROGRAM AT LIMERICK GENERATING STATION (LGS), UNITS 1 AND 2 (70370)
Background Snubbers are restraining devices used to control the movement of pipe and equipment during abnormal conditions such as seismic events, turbine trips, safety / relief valve discharge, and rapid valve closure. Snubbers permit displacement of the pipe as a result of slow movements such as thermal expansion, but restrains rapid motions such as those induced by earthquakes and water hammers. However, while snubbers present convenient solutions in design and analysis, the use of snubbers has proven to have many practical and economic disadvantages.-
Malfunction of snubbers in the lockup mode during normal plant operation has created unanticipated high pipe thermal stresses. Because of these haidware problems, snubbers have contributed to the escalating maintenance cort as a result of inservice inspection and testing requirements. Industry experience has shown that piping systems often have more snubbers than are actually required for protecting the piping from earthquakes. At LGS, Units 1 and 2, the snubber population consists of the following:
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' UNIT 1 COMMON UNIT 2
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INITIAL TOTAL 1562 110 1180 NON-TECHNICAL-147
79 SPECIFICATION
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REMOVED BY SNUBBER-155
413 REDUCTION PROGRAM TOTAL TECHNICAL 1260 110
.688 SPECIFICATION Findings Limerick Generating Station Unit No. I has completed its snubber functional tesiing and overhauls for refueling outage IRO4 on March,1992. The scope consisted of fifty-five (55)
mechanical snubbers and one mechanical compensating strut. These 56 functional tests
identified by the licensee's contractor met the ASME Section XI and Technical Specification (TS) requirements using the 55 plan. Failure to meet the acceptance criteria for plan 55 resulted in an additional 24 snubbers that were included in the initial scope for functional test.
At the end of this Spring Refueling Outage 1992, the licensee functionally tested a total of
693 mechanical snubbers and one compensating strut. The test included.75 spare mechanical snubbers, and a spare compensating strut. Ninety-three mechanical snubbers were retested and met the acceptance criteria.
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The results of this snubber surveillance showed that 55 mechanical snubbers failed to meet tre acceptance criteria. This resulted in 55 non-conformance reports (NCRs), of which 14
were resolved by engineering evaluation. The remaining 41 snubber failures failed due to
physical abnormalities. The inspector focused on the 41 from which 17 failed due to " dry gre se."
A vendor speci6 zing in nac%ar radiation resistance (NRR) jubricants supplied the licensee with NRR grease 159. Their technical specification stated that grease NRR 159 would retain
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its properties and lubricating ability through a temperature range cf-10 to 325 degrees fahrenheit ("F) and up to 30 times 100 Million Rads (a rad is a unit of radiation energy i
absorption). The inspector made a comparison of the values obtained by empirical tests of
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the grease by itself, the grease in the snubbers Aring functional test, and in the expected plant's environment. The inspector found the following:
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I ATTRIBUTES GREASE SNUBBER LICENSEE SUPPLIER SUPPLIER REQUIREMENTS Normal Operating-20 to +300 135(avg.),150 (max)
Range *F Abnormal Operating-10 to + 325 (< 12 hr) 350 340 / 320 / 250 Range F Radiation Dose Limit
30
.64 (X100M RAD)
no limits all steam or 100%
Relative Humidity
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Conclusion Based on the values observed above, it appears that neither temperature nor radiation caused the snubber's grease to dry. However, the inspector emphasized the fact that there is a need to establish a root cause investigation to prevent further failure of snubbers due to " dry 3rease." The inspector added that replacing snubbers upon failure does not constitute a comprehensive corrective action. The licensee stated that they will initiate a root cause analysis to begin a comprehensive corrective action. This is an Unresolved item No. 93-05-01, pending the NRC review of the licensee's corrective action.
REVIEW OF PROCEDURE FOR FUNCTIONAL EXAMINATION OF SNUBBERS The inspector walked-through the functional testing facility and observed the functional test in progress for mechanical snubbers of LGS Unit 2. In the testing facility, the inspector interviewed the responsible personnel to capture and evaluate details of these tests. In addition, the inspector reviewed the pertinent procedures. These procedures implemented the requirements of the Technical Specifications, surveillance requirements, 4.7.4 for LGS Units 1 and 2 addressing the surveillance, the administrative control of snubber data, the scheduling of snubber visual examinations, and functional testing.
The inspector observed the functional test for snubbers, consisting of drag and acceleration tests. These tests are conducted with state-of-the-art technology in a controlled environment and by qualified individuals. The test report is generated in-situ, on form ST-4-103-301-2, j
and ready to be signed by the level III responsible reviewer. Breakaway drag, initial running drag, acceleration limit, and final running drag were recorded and compared with the acceptance criteria. Thee tests are illustrated by plots at very small time intervals.
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The inspector verified that the record of snubber service life monitoring pursuant to Technical Specification is properly recorded and is in accordance with the Technical Specification (administrative controls). This is accomplished by using a coriputer program to determine that it precisely conforms to the Technical Specifications, procedures,xnd specific needs of the plant.
Conclusion Based on the review of the functional test at Unit 2, the inspector concluded this test was
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conducted with state-of-the art technology in a controlled environment and by qualified individuals. Additionally the record keeping was found to be computerized and in
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compliance with the Technical Specification.
In addition, the inspector reviewed a sample of snubber testing records, and found that the contractor personnel performing the snubber testing are qualified and certified to test j
The inspector verified that visual testing (VT-3) examinations were performed for integral
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and non-integral attachments of snubbers, such as lugs, bolting, pins, and clamps.
4.0 MANAGEMENT MEETINGS Licensee management was informed of the scope and purpose of the inspection at the beginning of the inspection. The findings of the inspection were discussed with the licensee management at the January 29,1993 exit meeting. See Attachment 1 for attendance.
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ATTACIIMENT 1
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Persons Contacted Philadelnhia Electric Company Jay Doering LGS Plant Manager
J.J. Gyrath Branch Head Engineering Assurance
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D.B. Neff LGS Licensing Engineer K. Hudson Engineer, NED
- D. Schmidt Engineer, Site U.S. Nuclear Regulatory Commission
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- T. Kenny Senior-Resident Inspector
- T. Eastick.
Resident Inspector
- Denotes those present at the exit meeting
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