ML16341B535
| ML16341B535 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/27/1981 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8102280583 | |
| Download: ML16341B535 (16) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION REGION V
'I990 N. CALIFORNIABOULEVARD SUITE 202, WALNUTCREEK PLAZA WALNUTCREEK, CALIFORNIA94596 CP January 27, 1981 Docket No. 50-275 Pacific Gas and Electric Comoany P.
0.
Box 7442 San Francisco, California 94106 Attention:,
Hr. Philip A. Crane, Jr.
Assistant General Counsel II
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J Cgy~~~gN EO$Y Gentlemen:
The enclosed IE Bulletin No. 81-01 is forwarded for your action with regard to your nuclear power facilities with operating license or near term operating license (NTOL).
To assist the NRC in evaluating ihe value/impact of each bulletin on all licensees, it would be helpful if you would provide,. an estimate of the manpower expended in the review and preparation of the report(s) required by the bulletin.
Please estimate separately the manpower associated with corrective actions required by this bulletin.
Should you have any questions regarding this bulletin or the actions required of you, please contact this office.
Sincerely, R.
H. Engelken Director
Enclosures:
l.
Recently issued IE Bulletins cc w/enclosures:
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B. Langley, Jr.,
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C. Thornberry, Plant Manager 81022 8 OS'
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT MASHINGTON, D.C.
20555 January 27, 1981 SSINS No.:
6820 Accession No.:
8005050075 IEB 81-01 IE Bulletin No. 81-01:
SURVEILLANCE OF MECHANICAL SNUBBERS Descri tion of Circumstances:
Several instances of failures of mechanical snubbers supplied by International Nuclear Safeguards Corporation,(,INC) have been identified that indicate possible deficiencies in these snubbers.
A summary of the failures that have occurred is provided below:
On August 9, 1974, the Tennessee Valley Authority submitted event report BFAO-50-260/74lll identifying 11 of 14, INC Mode'} MSVA-1A snubberq that were found inoperable on Browns Ferry Nuclear j'ower Station Unit 2 and subsequently identified 5 of 14 inoperable units on Browns perry Nuclear Power Unit No 3.
All of these units were found to be frozen, and the cause was attributed to a failure to lubricate the par ts during assembly.
The failed snubbers were replaced with new units produced by the same manufacturer.
2.
3.
On April 12, 1976, the St. Lucie Plant Unit 1 facility.of Florida Power and Light Corporation submitted event report No. 50-335-76-.9 wherein five INC Model MSVA-1 snubbers-were identified as inoperable because they were found to be frozen.
The failures were caused by oxidation on the internals and by improper assembly.
All INC mechanical snubbers were replaced with units produced by anothe} manufacturer.
On April 8,
- 1977, Iowa Electric Light and Power Company submitted event report No. 77-23 for the Duane Arnold Energy Center facility that identi-fied 13 INC Model 1MSVA-1 Type AS snubbers to be frozen; the cause of.
failure was attributed to large amounts of interior oxidation.
The units were replaced with those produced by another manufacturer.
On December 5,
1979, personnel from the Nuclear. Regulatory Commission visited Department of Energy (DOE) facilities at Richland, llashington, to obtain information on DOE experience with INC snubbers at the Fast )lux Test Facilitv (FFTF).
The DOE-owned FFTF was equipped with more than 4,000 mechanical pipe restraints (snubbers) supplied by INC.
In 1978, FFTF examined more than 800 of these mechanical snubbers by removing them from their installation and found that 43, or about 5X of those
- examined, were frozen.
The pl'ant was still under construction so the snubbers had seen no service and had been subjected to only normal construction environments for 1 to 2 years.
IEB 81-01 January 27, 1981 Page 2 of 6 Tests were conducted on three operable snubbers by installing them on a
Hanford Engineering and Development Laboratory (HEDL) process line.
The three snubbers were subjected to flow-induced low-amplitude vibration (0.003 inches or less).
These snubbers were of both the combined carbon steel and stainless steel construction and the all stainless steel con-struction.
Detailed test data are not'available to the, NRC at this time.
However, all three snubbers froze after being subjected to the vibration for periods of 3 to 30 days.
The failure modes on all units inspected and tested involved a number of different mechanisms leading to,the, freezing of the snubbers.
Following disassembly of some of the snubbers, inspections showed the fai lures were caused by improper assembly; overheating of internal components caused by welding (during fabrication);
and sensitivity of the design to dirt, corrosion, and inadequate or excessive lubrication.
DOE concluded that there were generic deficiencies in the design of the.snubbers of this specific manufacturer for application to the FFTF facility and for pipes subjected to vibration.
All INC mechanical snubbers in FFTF.,have been replaced with snubbers produced by another manufacturer.
5.
On Hay 31, 1980, Georgia Power Company reported eight INC snubbers located on instrument and drain lines at Edwin I. Hatch Nuclear Plant Unit 1 were identified as inoperable (LER 321-80-55).
The cause of the failures was identified as internal corrosion that caused a frozen condition.
In an attempt to free a snubber (750-pound capacity), forces up to 1500..pounds were applied in both the "extend" and "retract" directions and the snubber did not mov'e.
The inspection of INC snubbers was,.compjeted, at the Hatch facility and, on June 30,
- 1980, NRC received a supplemental report that 45 of the 61 snubbers that had been inspected on Unit:1 had.been identi-'ied as inoperable and three of the 42 snubbers that were inspected on Unit 2 were inoperable.
All inoperable snubbers were replaced prior to startup of the affected unit.
Some were replaced with mechanical units produced by another manufacturer, some were replaced with, later-model INC
- snubbers, and three were replaced with rigid restraints.
,Plans are being made to replace all INC snubbers during upcoming refueling outages.
Analyses are also being performed on the piping affected by the locked up snubbers.
In addition to INC snubber failures, failures of mechanical snu4bers by another manufacturer are identified below:
1.
On September 7, 1979, Public Service Electric and Gas Company reported the failure of three Model PSA-3 mechanical snubbers manufactured by Pacific Scientific Company that were located on a main feedwater line of Salem Nuclear Generating Station Unit 1 (LER 79-54).
These three snubbers could not be rotated around their spherical rod end bearings.
The snubbers were removed and inspection revealed that the lead screw and traveling nut
- assembly, which translates linear to rotational motion, had failed.
The snubbers no longer provided seismic shock restraint under this condition.
These snubbers are directly upstream of the nuclear Class II piping boundary and are included in the stress calculations for the seismic analysis of the nuclear portion of the main feedwater piping.
Failure of the snubbers
IEB 81-01 January 27, 1981 Page 3 of 6 appeared to result from a force many times greater than the design load of the snubbers.
This force was either an extreme shock load or occurred when the snubber was in the fully retracted condition.
The snubbers were replaced with units produced by the same manufacturer.
2.
On April 10, 1979, Consumers Power Company reported a failure of eight Model PSA-3 Pacific Scientific snubbers at their Big Rock Point Nuclear Plant facility, (LER 79-017/03L-0).
The cause of the failure was improper installation in that a spherical washer -was omitted from the transition tube.
3.
On March 15 and June 11, 1979, Florida Power and Light reported failures of Pacific Scientific Company mechanical snubbers on main steam,and feedwater systems at Turkey Point Plant Units 3 and 4
(LER 79-006/03L-0 and 79-009/03L-0 respectively).
The cause in both cases was attributed to excessive loading.
The nature of the above mechanical snubber failures is to prevent the piping
- systems, to which they are attached, from moving freely during the normal thermal heat up and cool down associated with plant operations.
,Restraining this thermal motion results in higher than normal stresses which, if high enough and repeated frequently enough, can lead to a premature fatigue failure of the piping system.
These mechanical snubbers have. been installed for a.number of years without any NRC requirements for periodic surveillance to determine.their condition.
As a result, their current condition is unknown to NRC. and therefore HRC is requesting a prompt examination of all mechanical snubbers installed.to,date.
Because of the high percentage of failures discovered with the INC snubbers, the time frame for their examination is the shortest and additional opera-bility tests are called for.
Actions to be Taken b
Licensees of 0 eratin Reactors:
1.
Within 30 days of the issuance date of this bulletin, all.normally accessible*
INC mechanical snubbers installed on safety-related, systems or in storage shall be visually examined and tested as follows; a.
Perform a visual examination for damage and, without causing the system to be inoperable except as permitted by the facility technical specifications, verify that the snubbers have freedom of movement by performing a manual test over the range of the stroke in both com-pression and tension.
b.
Perform an operability test to confirm that.(1) activation (restraining action) occurs in both compression and tension and (2) the drag forces are within the specified range in both. compression and tension.
The tests shall be performed on all snubbers in storage
'nd on a representative sample (10Ã of the total of this type of snubber in use in the plant or 35, which ever is less) of the
- "Normally accessible" refers to those areas of the plant that can be entered during reactor operation.
J
S IEB 81-01 January 27, 1981 Page 4 of 6 normally accessible snubbers that are in service and can. be indiv-idually removed without causing the system to be inoperable, except as permitted by the facility technical specifications.
For each snubber that does not meet the test acceptance
- criteria, an.additional representative sample (as defined above) of this type of snubber shall be tested.
For each of these additional snubbers that do not meet the test acceptance criteria, another representative sample of this type of snubber shall be tested.
This cycle shall be repeated until, no more failures have been found or until all snubbers of this type have been tested.
The samples should be made up of snubbers representing the various sizes.
C.
d.
e.
Snubbers which have been examined and tested in a manner, comparable to Items la and 1b above within the last six months may be exempted.
If any failures are identified in Items la or.lb above,.take corrective action and evaluate the effect of.the failure, on.the system operability pursuant to the facility technical specifications for continued. operation.
If failures are identified in Items la and lb above, and. if INC snubbers are known to be located in any inaccessible areas.,
a pjant.shutdown shall be nerformed within 30 days after the discoveryof the first inoperable snubber and inspections conducted in accordance with Item 2a and 2b below, unless justification for continued operation has been provided to the NRC.
2.
Visually examine and test all inaccessible INC mechanical snubbers installed on safety related systems at the next outage of, greater than five days duration as follows:
a
~
Visually examine and manually test all inaccessible snubbers as described in Item la above.
b.
Perform an operability test on a representative sample of inaccessible snubbers as described in Item 1b above.
c ~
Snubbers which have been examined and tested in a manner comparable to Items 2a and 2b above within the last six months may be exempted.
If any failures are identified in Items 2a or 2b above, take corrective action to evaluate the effect of the failure on system operability pursuant to the facility technical specifications for resuming operation.
3.
Provide a schedule for an inspection program covering mechanical snubbers produced by other manufactures.
As a minimum, this inspection program shall:
a
~
b.
Include all snubbers installed on safety-pelated systems; Include the visual examination and manual test described in Item la above for all snubbers;
iv
IEB 81-01 January 01, 1981 Page 5 of 6 c.
Snubbers which have been examined and tested in a manner comparable to Item 3b above within the last twelve months may be exempted:
d.
Require the corrective action and evaluations described, in Items ld and 2d above; and e.
Be completed prior to the completion of the next refueling outage.
Plants which are currently in a refueling outage should perform the visual examination and manual t'ests of inaccessible mechanical snubbers before resumption of operations unless some other basis for assurance of snubber operability is provided to the NRC.
4.
Submit a report of the results of the inspections, testing and evaluation requested in Item 1 to NRC within 45 days of the issuance date of this bulletin.
Report the results of. the inspections, testing and evaluation requested in Item 2 within 30 days after the inspection and testing have been completed.
The response to Item 3 shall be submitted within 60 days of the issuance date of this Bulletin.
The results of.the inspections performed for Item 3 shall be submitted. within 60 days after the completion of the inspection.
The reports shall contain the following:
a
~
b.
c ~
d.
A description of the visual examinations and tests.
performed.
Number of snubbers examined and tested.
Grouping by, manufacturer
- name, model
- number, and size is acceptable.
Number of failures identified; manufacturer
- name, model number, size, mode of failure, cause of failure, corrective action, snubber location, effect, of failure on plant and system safety, and justification for continuing or resuming operation.
The above information shall also be provided for the snubbers exempted by Items 1c, 2c, and 3c above.
Actions to be Taken b
the Following Licensees Holdin Construction Permits:
Oiablo Canyon Nuclear Power. Plant Unit 1; San Onofre Nuclear Station Unit 2; llatts Bar Nuclear Plant Units 1 and 2; and Yirgil C.
Summer Nuclear Station Unit 1.
1.
After preoperational and/or hot functional testing and preceding fuel loading, visually examine and test the mechanical snubbers installed on safety-related systems as follows:
a.
For all snubbers perform a visual examination for damage and verify that the snubbers have freedom of movement by performing a manual test over the range of the stroke in both compression.and tension.
IEB 81-01 January 27, 1981 Page 6 of 6 b.
For INC snubbers, perform an operability test. to confirm that (1) activation (restraining action) occurs in both compression and tension and (2) the drag forces are within the specified range in both compression and tension.
The tests shall be performed on a representative sample (10K of the tota] of this type of snubber in use in the plant or 35, which ever is 'jess).
For each snubber that does not.meet the test acceptance
- criteria, an additional representative sample (as defined above) of this type of snubber shall be tested.
For each of these additional snubbers that do not meet the test acceptance criteria, another representative sample of this type of snubber shall be tested.
This cycle shall be repeated until no more failures have been found or until all snubbers of this type have been tested.
The samples should be made up of snubbers that represent the-various sizes.
c.
If any failures are identified in Items a or.b above, take corrective action prior to fuel loading.
2.
The schedule for the inspections and tests requested in Item
- 3. above, shall be submitted within 60 days of the issuance date of this bulletin.
The results of the inspections,
- testing, and evaluation requested in Item 1
shall be reported to NRC >>ithin 30 days after the inspection and testing have been completed.
The reports shall contain the following; a.
A description of the visual examinations and tests performed.
b.
Number of snubbers examined and tested.
Grouping by manufacturer
- name, model
- number, and size isacceptable.
c.
Number of failures identified; manufacturer
- name, model
- number, size, mode of fai lure, cause of fai lure, corrective action, and snubber location.
- Reports, signed under oath or affirmation, under the provisions of Section 182a of the Atomic Energy Act of 1954, shall be submitted to the Director of the appropriate NRC Regional Office and a cony shall be forwarded to the Director of the HRC Office of Inspection and Enforcement, Hashington, D,
C.
20555.
If you desire additional information regarding this matter, please contact the IE Regional Office.
Approved by GAO B-180225 (S81003) expires December 31, 1981.
r
RECENTLY ISSUED IE BULLETINS IEB 81-01 January 27, 1981 Bul 1 etin No.
80-25 Supplement 4
to 80-17 80-24 80-23 80-22 Subject Operating Problems with Target Rock Safety-Relief Valves at BHRs Failure of Control Rods to Insert During a Scram at a
BHR Prevention of Damage Due to Hater Leakage Inside Containment (October 17, 1980 Indian Point 2
Event)
Failures of Solenoid Valves Manufactured by Valcor Engineering Corporation Automation Industries, Model 200-520-008 Sealed-Source Connectors Date Issued 12/19/80 12/18/80 11/21/80 11/14/80 9/11/80 Issued To All BHR facilities with OL 8 specified near term OL BWR facilities
& all BHRs with a CP To specified BWRs with an OL 8 All BHRs with a CP All power reactor facilities with OL or CI'll power reactor facilities with OL or CP A'I] radiography licensees 80-21 Supplement 3
to 79-01B Supplement 2
to 79-01B 80-22 Valve yokes supplied by 11/6/80 Malcolm Foundry
- Company, Inc.
Automation Industries, Model 200-520-008 Sealed-source Connectors 9/11/80 Environmental gual ifi cation 10/24/80 of Class 1E Equipment Environmental qualification 9/30/80 of Class 1E Equipment All light water reactor facilities with OLs or CPs All power reactor facilities with an OL All power reactor facilities with an OL Al1, radi ography licensees 79-26 Revision 1
Boron Loss from BHR Control Blades 8/29/80 All BHR power facilities with an OL OL = Operating License CP
= Construction Permit
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