ML16340B460
| ML16340B460 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/27/1981 |
| From: | Engeleken R, Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8102280551 | |
| Download: ML16340B460 (16) | |
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'OAL".UTCREEK, CALIFORNIA9<596 January 27, 1981 Docket No. 50-323 Pacific Gas and Electric Comoany P. 0.
Box 7442 San Francisco, California 94106 Attention:
Mr. Philip A. Crane, Jr.
"ssis-.am Generai Counsel Gentlemen:
The enclosed Bulletin 81-01 is T'orwarded to you for information.
Ho written response is required. if you desire additional information regarding this
- matter, please conTacz this office.
Sincerely, R.
H. Engelken Jirecxor
Enclosures:
1.
Recently issued IE Bulletins cc w/enclosures:
E.
B. Langley, Jr.,
PG8E M. Raymond, PG8E R.
C. Thornberry, Plant Manager
'i y0888C55 1
lI
SSIHS No.:
6820 Accession No.:
8005050075 IEB 81-01 UNITED STATES NUCLEAR REGULATORY COMMISS ION OFFICE OF INSPECTION AND ENFORCEMEHT WASHINGTON, D.C.
20555 January 27, 1981 IE Bulletin No. 81-01:
SURVEILLANCE OF MECHANICAL SNUBBERS Description of Circumstances:
Several instances of failures of mechanical snubbers supplied by International Nuclear Safeguards Corporation
( INC) have been identified that indicate possible deficiencies in tnese snubbers.
A summary of the failures that have occurred is provided below:
On August 9, 1974, the Tennessee Valley Authority submitted event report BFAO-50-260/741W identifying 11 of 14 INC Model MSVA-1A snubbers that were found inoperable on Browns Ferry Nuclear Power Station Unit 2 and subsequently identified 5 of 14 inoperable units on Browns Ferry 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 parts 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 F'lorida Power and Light Corporation submitted event report No. 50-335-76-.9 wherein five IHC Model )lSVA-1 snubbers were identified as inoperable because they were found to be frozen.
The failures were caused bv oxidation on the internals and by improper assembly.
All INC mechanical snubbers were replaced with units produced by another 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 ailure 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, Washington, to obtain information on DOE experience with INC snubbers at the Fast Flux Test Facility (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 5'~ of those
- examined, were frozen.
The plant 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-amolitude vibration (0.003 inches or less).
These snubbers were of both the combined carbon steel and stainless steel construction and the all stain'less steel con-struction.
Detailed test data are not available to the NRC at this time.
However, all three snubbers froze after beina 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, insoections showed the failures were caused by imoroper assemo]y; overheatina of internal components caused by welding (durina fabricaiion); and sensitivity of the desian to dirt, corrosion, and inadeauaie or excessive lubrication.
DOE concluded that there were generic deficiencies in ihe desian of the.snubbers of this specific manufacturer for application to the FFTF facility and for pipes subjected io vibration.
All INC mechanical snubbers in FFTF, have been replaced with snubbers produced by another manufaciurer.
5.
On Hay 31, 1980, Georaia Power Company reporied eight INC snilbbers 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 ihai caused a frozen condi tion.
In an attempt to free a snubber (750-pound capaci iy), forces up to 1500 pounds were applied in both ihe "extend" and "retract" directions and the snubber did not move.
The inspection of INC snubbers was completed 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-fied as inoperable and three of the 42 snubbers that were inspected on Unit 2 were inoperable.
All inoperable snubbers were replaced prior to startup o
ihe 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 pipina affected by the locked up snubbers
~
In addition to INC snubber failures, Failures of mechanical snu4bers by anothe~
manufacturer are identified be'ow:
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 Generatina 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 pioing.
Failure of the snubbers
IEB 81-01 January 27, 1981 Page 3 of 6 aopeared 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 oroduced by the same manufacturer.
2.
On April 10,
- 1979, Consumers Power Comoany reported a failure of eioht 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 Harch 15 and June 11, 1979, Florida Power and Light reported failures of Paci=ic Scientific Comoany mechanical snubbers on main steam and feedwater systems ai Turkey Point Plant Units 3 and 4 (LER 79-006/03L-0 and
,79-009/03L-0 respectively).
The cause in boih cases was attributed to excessive loading.
The nature of the above mechanical snubber failures is to prevent the oiping
- systems, to which ihey are attached, from moving freely during ihe normal thermal heat up and cool down associated wiih plant operations.
Restraining this thermal motion results in higher than normal siresses which, if high enough and repeated frequenily enough, can lead to a premature fatigue failure of the piping system.
These mechanical snubbers have been insialled for a.number of years without any NRC requiremenis for periodic surveillance io deiermine.their condition.
As a result, their current condition is unknown to NRC and therefore NRC is requesting a prompt examination of all mechanical snubbers installed to date.
Because of.he 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.
';lithin 30
'avs 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.
b.
Perform a visual examination for damage
- and, wi thout 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.
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 and on a representative sample (105 of the total of this type of snubber in use in the plant or 35, which ever's less) of the
- "Normally accessible" refers io those areas of the plant that can be entered during reactor operation.
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 tyoe of snubber shall be tested.
This cycle shall be repeated unti 1 no more failures have been found or until all snubbers of this type have been'ested.
The samples should be made up of snubbers representing the various sizes.
C.
Snubbers which have been examined and tested in a manner comparable to Items la and 1b above within ihe last six months may be exempted.
d.
e.
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 plant shutdown shall be performed within 30 days after the discovery of the first inoperable snubber and inspections conducted in accordance wiih Item 2a and 2b below, unless justification for continued operation has been provided to the t<RC.
2.
'lisualiy 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.
'lisually examine and manually test all inaccessible snubbers as described in Item la above.
b.
Per-orm an operability test on a representative sample of inaccessible snubbers as describe4 in Item lb above.
c ~
d.
Snubbers which have been examined and tested in a manner comparable to Items 2a and 2b above w',thin 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
~
Include all snubbers installed on safety-related systems; Include the visual examination and manual test described in Item la above for all snubbers;
4
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 1d and 2d above; and e.
Be completed prior to the completion'f 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 ooerations unless some other basis for assurance of snubber operability is orovided to the NRC.
Submi ~ a report of the results of the inspections, testing and evaluation reaueszed in Item 1 to NRC within 45 days of the issuance date of this bulletin.
Report the results of the inspections, testing and evaluation reouested in Item 2 within 30 days after the inspection and testing have beon completed.
The resoonse to Item 3 shall be submitted within 60 davs of the issuance date of this Bulletin.
The results of.the inspections performed for Item 3 shall be submi tted within 60 days after the completion of the inspection.
The reports shall contain the following:
a.
c ~
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 sha!1 also be provided for the snubbers exempted by Items 1c, 2c, and. 3c above.
Actions to be Taken b,
the Followinq Licensees Holdin Construction Permits:
Diablo Canyon Nuclear Power Plant Unit 1; San Onofre Nuclear Station Unit 2; Watts Bar Nuclear Plant Units 1 and 2; and Virgil 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 Ii'lC 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 comoression and tension.
The tests shall be performed on a representative sample
( 10% of the total of this type of snubber in use in the plant or 35, which ever is less).
'or each snubber that does not meet the test acceptance cri teria, 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 tyoe of snubber shall be tested.
This cycle shall be repeat d uncoil 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 correczive action prior to fuel loading.
2.
The schedule for the inspections and tests requested in Item j. 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 iHRC within 30 days after the inspection and testing have been completed.
The reports shall contain tne following:
a.
A description of the visual examinations and tests performed.
b.
incumber of snuobers examined and tested.
Grouping by manufacturer
- name, model
- number, and size is acceptable.
c.
i'lumber of failures identified; manufacturer
- name, model
- number, size, mode of failure, cause of failure, 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 tlRC Regional Office and a copy shall be forwarded to the Director of the ilRC Office of Inspection and Enforcement, washington, 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.
Bulletin No.
Subject RECENTLY ISSUED IE BULLETINS Date Issued IEB 81-01 January 27, 1981 Issued To 80-25 Supplement 4
to 80-17 80-24 80-23 80-22
'oerating Problems with Target Rock Safety-Relief Valves at BHRs Failure of Control Rods to Insert Durina a Scram at a
BHR Preveniion of Damage Oue to Hater Leakage Inside Containmeni (October 17, 1980 Indian Poini 2 Even')
Failures of Solenoid Valves i'lanufactured by
'!alcor Enaineering Corporation Automaiion indus tries, liodei 200-520-008 Sealed-Source Connectors 12/19/80 12/18/80 11/21/80 11/14/80 9/11/80 All BWR facilities with OL & specified near term OL BWR facilities
& ail BWRs with a CP To specified BWRs with an OL
& All BWRs with a CP All power reactor facilities with OL or CP All power reacior facilities with GL or CP All radiography licensees 80-21 Supplement.
3 to 79-01B Supplement 2
to 79-01B Valve yokes suppi i ed by 11/6/80
!'1al colm Foundry
- Company, Inc.
Environmental qualification 10/24/80 of Class lE Equipment Environmental gual ification 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 80-22 79-26 Revision 1
Automation Industries, flodel 200-520-008 Sealed-source Connectors Boron Loss from O'HR Control Blades 9/11/80 8/29/80 All radioaraphy licensees All BWR power facilities with an OL OL = Operating License CP
= Construction Permit
I