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l The enclosed Information Notices Nos. 81-27 and 81-28, " Flammable Gas Mixtures In the Waste Gas Decay Tanks in FWR Plant's and Failure of Rockwell-Edward Main Steam Isolation Valves", is forwarded to you for information. No written responsa is required.
If you desire additional information regarding this t
matter, please cJatact this office.
Sincerely, h
Roriald C. Haynas Director
Enclosure:
IE In'ormation Notices Nos. 81-27 with 1 attachment and 81-28 with 2 attachments CONTACT:
D. L. Caphton (215-337-5287)
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SSINS No.: 6835 Accession No.:
8103300415 IN 81-27 UNITED STATES NUCLEA2 REGULATORY COMMISSICN OFFICE OF INSFECTION AND ENFORCEMENT WASHI)9 TON, D.C.
20555 September 3, 19?.1 IE INFORMATION NOTICE NO. 81-27:
FLWMABLE GAS MIXTURES IN THE WASTE GAS DECAY TANKS Di PWR PLANTS Descriotion of Circumstances:
In July 1981, hydrogen ignition occurred in one gaseous waste decay tank at San Onofre Unit 1 while the plant was in cold shutdown.
This resulted in.a release of about 3.8 curies of noble gases and minor tank damage.
The cause of the hydrogen ignition was air contamination of the inert nitrogen system which is used to control the hydrogen-oxygen concentrations in the tank.
The source of air was identified as instrument air leaking through check valves it the cross connections between instrument air and nitrogen lines.
Under normal operating conditions, the pressure in the instrument air system is higher than that of the nitrogen systam.
These cross connections had been installed in response to TMI Action Plan requirement item II.E.1.2 of NUREG-0737. The nitrogen tystem provided a backup gas supply to the. air-operated ;;eam suopiy valve for tra steam-driven auxiliary feedwater pump.
This backup was installed to provide x " safety grade" auxiliary feedwater system that satisfies the single-failure criteria.,0ther cross connections, which apparently did not leak air into the nitrogen system, had been previously installed in response to TMI Action Plan requirement II,G.1 of NUREG-0737 to provide a redundant gas supply to the air-operated pressurizer relief valves and the associatec clock valves.
Following the occurrence, the licensee sampled all potentially affected tanks and determined that most of the tanks had oxygen levels above 10 to 15 percent.
l Generally, the gas in pressurized water reactor (PWR) waste gas systems is hydrogen rich and the oxygen concentr tion is controllel to prevent flammable gas mixtures.
Flammable concentration of gas mixtures can be prevented by limiting aither the hydrogen or the oxygen concentration to less than 3 percent.
To eliminste the possibility of recurrence, the licensee has now completely separated those portions of the nitrogen system that are a backup supply to the air system from the balance of the nitrogen system that supplies cover gas.
Bottles of compressed nitrogen are now used to provide the backup to the air system.
We are aware of another instance of flammable mixtures in waste gas tanks.
In August 1980, Arkansas Power and Light Company (AP&L) discovered flamnable concentrations of hydrogen and oxygen in the waste gcs decay tanks at Arkansas Nuclear One, Unit 1.
The flammable gas mixtures were created after the primary coolant picked up oxygen from the air during refueling and maintenance.
No ignition or explosion was reported.
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IN 81-27 Septemb:r 3, 1981 Page 2 of 2 It appears that licensees need to devote more attention to the potential effects of nitrogen-air system cross connections when systems are modified te use nitrogen as a backup to air systems.
If cross connections exist, the potential for the formation of flammable gas mixtures should be evaluated. A sampling program to assure that flammable gas mixtures do not exist in tanks should be considered.
No written response to this information notice is required.
If you need additional information with regard to this subject, please contact the Director of the appropriate NRC Regional Office.
Attachment:
Recently issued IE Information N.itices
/
Attachment TN 81-27 September 3, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date
~ Issued to
~
Notice No.
Issued 81-26 Compilation of Health 8/28/81 All holders of a power Physics Related reactor OL or CP, Information Items Research Reactor, Fuel Facilities and Priority Material License 81-25 Open Equalizing Valve 8/24/81 All holders of a of Differential Pressure power reactor Transmitted Causes OL or CP Reactor Scram and Loss of Redundant Safety Signals 81-24 Auxiliary Feed Pump 8/5/81 All holders of a Turbine Bearing power reactor Failures OL or CP S1-23 Fuel Assembly Damaged 8/4/81 All holders of a due to Improper power reactor Positioning of Handling OL-or CP Equipment 81-22 Section 235 and 236 7/31/81 All holders of a power Amendments to the or research reactor OL Atomic Energy Act or CP, all fuel fabrication of 1954 2nd reprocessing and spent fuel storage licensees and applicants 81-21 Potential loss of 7/21/81 All holders of a Direct Access to power reactor Ultimate Heat Sink OL or CP 81-20 Test Failures of Elec-7/13/81 All holders of a trical Penetration power reactor Assemblies CL or CP 81 '9 Lost Parts in Primary 7/6/81 All holders of a Coolant System power reactor OL or CP 81-18 Excessive Radiation 6/23/81 Specified licensees Exposures to the Fingers holding Byproduct of Three Individuals licenses Incurred During Cleaning and Wipe Testing of Radioactive Sealed Sources at a Sealed-Source Manufacturing Facility
SSIN Na.: 6335 Accession Ns.:
8103300413 IN 81-28 UNITED STATES NUCLEAR REGULATORY CCMMISSICN OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, 0.^, 20555 September 3, 1981 IE INFORMATION NOTICE NO. 81-28:
FAILURE OF ROCKWELL-ECWARD MAIN STEAM ISOLATION VALVES Descriotion of Circumstances:
There have been several recent mechanical failures of the "Rockwell-Edward Flite l
Flow Stop Valve," a "Y" pattern globe valve made by Rockwell International, used
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for main steam isolation valves (MSIV) at same BWR facilities.. Operating SWR facilities using this valve include Brunswick Unit 1 and 2, Coocer, Quane Arnold.
Fit: patrick, Hatch Unit 2,.and Vermont Yankee. Of the seven total reported mechanical failures, five occurred at Brunswick Unit 2 and one each occurred at Brunswick Unit 1 and Hatch Unit 2.
The valve components that have failed are shown in Figure 1. The piston assembly is attached to the main disk (2) by thread engagement and then restrained from unwinding by pin (4).
The stem disk (1) is. also attached to the stem (6) by thread engagement tightened to 1050 ft-lb torque specifications with an anti-rotation restraint provided by pin (3).
The valve is closed primarily by spring forces.
The valve is installed so that reactor steam pressure works to seat the main disk. The stem disk provides pressure equalization action to reduce over-seat load for opening the main disk against system pressure.
The failures that have occurred involved a mechanical separation of valve i nternal s. This separation was either at the stem-to-stem-disk threaded connection or at the main-disk-to piston threaded connection.
Either failure permits the main disk to be free of the stem.
The failure in either mode results from failure of the threaded connection, which in some cases is caused by vibration-induced rotation of the disk so that it becomes disconnected from its threaded mate.
Such rotation is believed to be causec by or aided by the propensity of steam flow to produce vibration and to create turning forces on valve internal components when antirotation restraint is inadequate due to a failed or missing pin. Other contributing causes are believed to result from reassembly of the valve after disassembly at the site; such reassembly may have included inadequately torqued connections and failure to properly install the pins.
Also, an examination of spare parts at the Brunswick site showed that the thread dimensions on the stems and stem disks did not meet drawing tolerances.
The individual failures are described below in chronological order.
1.
In January 1976, the Brunswick Unit 2 "0" steam line inboard valve main disk separated from the piston.
There was no evidence that pin (4) was installed.
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IN 81-28 3:ptemb:r 3, 1981 Page 2 of 2 2.
On Jaauary 30, 1979, the Brunswick Unit 2 "A" steam line inboard valve stem disk separated from the stem. A square pin was used in the round hole at l
point (3).
The corners of the pin experienced high stress,'thereby causing cracking of the pin.
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3.
On January 15, 1981, the Brunswick Unit 2 "C" steam liae outboard valve main disk separated from the piston.
There was no evidence that pin (4) was dver inserted.
This was deduced from finding the hole not deformed and no sign of a plug weld.
4.
On March 5,1981, the Hatch Unit 2 "A" steam line inboard valve stem disk separated from the stem.
Pin (3) was not fully inserted.
5.
On March 30, 1981, the Brunswick 'init 1 "C" steam line outboard valve stem disX separated from the stem.
Pin (3) failed and was not recovered.
6.
On July 2,1981, the Brunswick Unit 2 "C" steam line inboard valve stem cisk separated from the stem.
Pin (3) was not properly installed.
7.
On July 18, 1981, the Brunswick Unit 2 "0" steam line inboard valve main disk separated from the piston.
Pin (4) was not fully inserted.
These failures nave *aised concerns regarding (1) the capabi'ity of the valve to perform its required safety function and (2) increased challenges to scfety systems.
However, it is noted that the failures to date have resulted in the main disk going closed (i.e., not cocking open) with some uncertainty only as to its leak tightness.
Detailed investigation of the July failures at Brunswick Unit 2 led to the preliminary findings of possible excessive vibrations on valve internals from steam flow turbulences created by the piping direction changes.
In addition, t5ere was evidence of loose thread connections.
Further invastigations and evaluations are currently in progres;.
Preliminary corrective actions by the licensee include increasing the stem pin size frca 5/16-inch to 3/8-inch, using three pins instead of one or two pins, and increasing.ne hole depth 1/8-inch into the stcm.
In addition, corrective actions for ths. main-disk-to piston connection include aeding an extra pin (of the same 1/2-inch size) and increasing the hole depth by 1/8-inch.
This information is provided as notification of a potentially significant matter that is still under review by the NRC staff.
In case the continuing NRC review finds that specific licensee actions would be appropriate, an IE circular or bulletin may be issued.
In the interim, we expect that licensees will review this information for applicability to their facilities.
No written response to this information is required.
If you need add'ticnal inform'ation regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Attachments:
1.
Figure 1 2.
Recently issued IE Information Notices 9
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!!! 81-28 September 3, 198i 1.
STEM DISX 2.
MAIN DISK 3.
ANTIR0TATION PIN - STEM OISK TO STEM 4.
ANTIKOTATION PIN - MAIN UlSX 10 PISTON 5.
STELLITED DISK GUIDES. 3 RIBS,120* APART (CUT OF SHOWN VIEW) 5.
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IN 81-28 September 3, 1981 1
RECENTLY ISSUE 0 IE INFORMATION NOTICES Information Subj5ct Date Issued to Notice No.
Issued 4
81-27 Flammable Gas Mixtures 9/3/31 All holders of a in the Waste Gas Decay power reactor Tanks in PWR Plants OL or CP 81-26 Compilation of Health 8/28/81 All holders of a power Physics Related reactor OL or CP, Information Items Research Reactor, Fuel Facilities and Priority Material '.icense 81-25 Open Equalizing Valve 8/24/81 11 holders Of a of Differential Pressure power reactor Transmitted Causes OL or CP Reactor Scram and Loss of Redundant Safety Signals f
81-24 Auxiliary Feed Pump 8/5/81 All holders of a Turb':ne Bearing power reactor Failures OL or CP 81-23 Fuel Assembly Damaged 8/4/81 All holders of a due to Improper power reactor Positioning of Handling OL or CP Equipment 81-22 Section 235 and 236 7/31/81 All holders of a power Amendments to the or research reactor OL Atomic Energy Act or CP, all fuel fabrication of 1954 and reprocessing and spent fuel storage licensees and applicants 81-21 Potential Loss of 7/21/81 All holcers of a Direct Access to power reactor Ultimate Heat Sink OL or CP 81-20 Test Failures of Elec-7/13/81 All holders of a trical Penetration power reactor Assemblies OL or CP 81-19 Lost Parts in Primary 7/6/81 All holders of a
. Coolant System power reactor OL or CP i
LIST OF HOLDERS OF NUCLEAR POWER REACTOR OPERATING LICENSES AND CONSTRUCTION PERMITS RECEIVING IE INFORMATION NOTICES NOS. 81-27 and 81-28 Baltimore Gas and Electric Company Docket Nos. 50-317 ATTN: Mr. A. E. Lundvall, Jr.
50-318 Vice President, Supply P. O. Box 1475 Baltimore, Maryland 21203 Boston Edison Company M/C Nuclear Docket No. 50-293 ATTN: Mr. A. V. Morisi Nuclear Operations Support Manager 800 Boylston Street Boston, Massachusetts 02199 a
Connecticut Yankee Atomic Power Company Docket No. 50-213 ATTN:
Mr. W. G. Counsil Vice President - Nuclear Engineering and Operations P. O. Box 270 Hart crd, Connecticut 06101 Consolidated Edison Company Li Occket Nos. 50-03 New York, Inc.
50-247 ATTN:
Mr. John O. O'Toole Vice President - Nuclear Engineering and Quality Assurance 4 Irving Place New York, New York 10003
/ Duquesne Lignt Company Docket No. 50-334 ATTN: Mr. J. J. Carey Vice President Nuclear Division P. O. Box 4 Shippingport, Pennsylvania 15077
/ Jersey Central Power and Light Company Docket No. 50-219 ATTN: Mr. Philip R. Clark Vice President - Nuclear GPU Nuclear 100 Interpace Parkway Parsippany, New Jersey 07054 w -
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2 Maine Yankee Atomic Power Company Docket No. 50-309 ATTN: Mr. Robert H. Groce Senior Engineer-Licensing 1671 Worcester Road Framingham, Massachusetts 01701
/ Metropolitan Edison Company Docket No. 50-289 ATTN: Mr. H. D. Hukill Vice President and Director of TMI-1 P. O. Box 4to Middletown, Pennsylvania 17057 s/ etropolitan Edison Company Cocket No. 50-320 M
ATTN: Mr. G. K. Hovey Vice President and Director of TMI-2 P. O. Box 480 Middletown, Pennsylvania 17057
/ Niagara Mohawk Power Corporation Docket No. 50-220 ATTN:
Mr. T. E. Lempges Vice Dresident Nuclear Generation 300 Erie Boulevard West Syracuse, New York 13202 Ncrtheast Nuclear Energy Company Docket Nos. 50-336 AITN:
Mr. W. G. Counsil 50-245 Senior Vice President - Nuclear 50-423 Engineering and Operations Group P. O. Box 270 Partford, Connecticut 06101 y/ Philadelphia Electric Company Docket Nos. 50-277 ATTN:
Mr. S. L. Daltroff 50-278 Vice President Electric Production 230'. Market Street Philadelphia, Pennsylvania 19101 v/ ower Authority of the State of New York Docket No. 50-286 P
Indian Point 3 Nuclear Power Plant ATTN: Mr. J. C. Brons Resident Manager P. O. Box 215 Buchanan, New Yer% 10511
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/ Power Authority of the State of New York Docket No. 50-3?'
James A. FitzPatrick Nuclear Power Plant ATTN: Mr. R. J. Pasternak Resident Manager P. O. Box 41 Lycoming, New York 13093
!PublicServicaElectricandGasCompany Docket Nos. 50-272 y
ATTN: Mr. F. W. Schneider 50-311 Vice President - Producti n 80 Park Plaza - 15A Newark, New Jersey 07101 Rochester Gas and Electric Corporation Docket No. 50-244 ATTN:
Mr. Jol.n E. Maier l
Vice President Elec:ric and Steam Production 89 East Avenue Rochester, New York 14649 Vermont Yankee Nuclear Power Corporation Docket No. 50-271 AT7M: Mr. Robert L. Smith Licensing Engineer 1671 Worcester Road Framingham, Massachusetts 01701 Yankee Atomic Electr'c Company Docket No. 50-29 v ATTN: Mr. James A. Kay Senior Engineer-Licensing 1671 Worcester Road Framingham, Massachusetts 01701 v/ uquesne Light Company Docket No. 50-412 D
ATTN: Mr. E. J. Woolever Vice President 435 Sixth Avenue 1
Pittsburgh, Pennsylvania 15219 l
v/ Jersey Central Power & Light Company Docket No. 50-363 ATTN: Mr. J. T. Carroll Acting Director Oyster Creek Nuclear Generating Station P. O. Box 388 Forked River, New Jersey 08731 Long Island Lighting Company Docket No. 50-3;2 ATTN: Mr. M. S. Pollock Vice President - Nuclear 175 East Old Country Road Hicksville, New York 11801
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]NiagaraMohawkPowerCorporation Docket No. 50-410 ATTN: Mr. Gerald K. Rhode Vice President System Project Management c/o Miss Catherine R. Seibert 300 Erie Boulevard, West Syracuse, NY 13202 Pennsylvania Power & Light Company Occket Nos. 50-387 ATTN: Mr. Norman W. Curtis 50-388 Vice President Engineering and Construction - Nuclear 2 North Ninth Street Allentown, Pennsylvania 18101 v/ Philadelphia Electric Company Docket Nos. 50-352 ATTN:
Mr. John S. Kemper 50-353 Vice President Engineering and Research 2301 Market Street Philadelphia, Pennsylvania 19101 v/ Public Service Electric & Gas Company Docket Nos. 50-354 ATTN:
Mr. T. J. Martin 50-355 Vice President Engineering and Construction 80 Park Plaza - 17C Newark, New Jersey 07101
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Public Service Company of New Hampshire Docket Nos. 50-443 ATTN:
Mr. h. C. Tallman 50-444
. Chairman and Chief Executive Officer 1000 Elm Street Manchester, New Hampshire 03105 w.
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