ML20010F172
| ML20010F172 | |
| Person / Time | |
|---|---|
| Site: | Monticello, Dresden, Davis Besse, Palisades, Perry, Fermi, Kewaunee, Point Beach, Byron, Braidwood, Prairie Island, Callaway, Duane Arnold, Clinton, Cook, Quad Cities, La Crosse, Big Rock Point, Zion, Midland, LaSalle, Zimmer, Bailly, Marble Hill  |
| Issue date: | 09/03/1981 |
| From: | Carroll D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wright G ILLINOIS, STATE OF |
| References | |
| NUDOCS 8109090455 | |
| Download: ML20010F172 (2) | |
Text
{{#Wiki_filter:m._ i ~' SEP 3 1981 Illinois Department of Nuclear Safety ATTN: Mr. Gary N. Wright, Manager Nuclear Facility Safety 1035 Outer T'..rk Drive, 5th Floor Springfield, IL 62704 Gentlemen: The enclosed IE Information Notices No. 81-27 and No. 81 28 titled " Flammable Gas Mixtures in the Waste Gas Decay Tanks in PWR Plants" and " Failure of "lockwell-Edward Main Steam Isolation Valves," respectively, was sent to the licensees listed below on September 3, 1981: American Electric Power Service Corporation Indiana and Michigan Power Company S D. C. Cook 1, 2 -(50-315,- 50-316) Cincinnati Gas & Electric Company Zimmer.(50-358) Cleveland Electric Illuminating Company Perry 1, 2 -(50-440, 441) Commonwealth Edison Company tn Braidwood I, 2-(50-456,*50-457) gd p F H Byron 1, 2 -(50-454, 50-455) I+ Dresden 1, 2, 3 (50-10, 50-237, 249) h M U LaSalle 1, 2 (50-373, 50-374) Quad-Cities 1, 2 -(50-254, 50-265) ? 02 0 91981. D 9 Zion 1, 2 (50-295, 50-304) u% m% ~j Consumers Power Company
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Big Rock Point (50-155) v A._ O sD Midland I, 2 -{50-329, 50-330) % / 91.\\.f ~ Palisades.(50-255) Dairyhnd Power Cooperative g /Of LACBWR*(50-499) f 914, Jj'seL~(,h'V ql 0 i b l 0109090435 810903 PDR ORG ESGILPH 1 O PDR ,..- 7
.m 1 Illinois Department cf - Nuclear Safety Detroit Edison Company Fermi 2-(50-341) Illinois Power Company Clinton 1, 2 (50-461, 50-462) Iowa Electric' Light.and Power. company Duane Arnold"(50-331) 4' Northern' Indiana Public Service Company Bailly -(50-367) Northc.n States Power Company Monticello-(50-263) Prairie Island 1, 2-(50-282 r 50-306) Public Service of Indiana Marble Hill-1, 2,(50-546,-50-547) Toledo Edison Company Davis-Besse 1 450-346) Union Electric Company-Callaway 1, 2,(50-483.-50-486) Wisconsin Electcle Power Company Poine Beach 1, 2.(50-266,*50-301)- Wisconsin Public Service Corporation Kewrinee (50-305) Sincerely, 1 ? '. ho ',
- he thy Word Processing and Document Control Section
Enclosures:
= 1. IE Information Notice No. 81-27 2. IE Information Notice No. 81-28 cc w/encls: Mr. D. W. Kan o, S-rgent & Lundy Resident Inspectors, RIII J. G. Keppler,RIII' Division Directors, RIII P. R. Wohld, RIII RIII. okI 9/3/81 c-cz ~
F SSINS No.: 6835' l Accession No.: 8103300415 ~~ IN 81-27 UilITED STATES NUCLEAR REGULATORY COMMISS' M OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTOS, D.C. 20555 September 3, 1981 IE INFORMATION NOTICE N0. 81-27: FLAMMABLE GAS MIXTURES IN THE WASTE GAS DECAY TANKS IN PWR PLANTS Description of Circumstinces: In July 1981, hydrogen ignition occurred in ene gaseous waste decay tank at San Onofre Unit I while the plant was in cold shutdown. This resulted in a release of about 8.8 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 chec'K valves at 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 system. These cross connections had been installed in response to TMI Action Plan requirement item II.E.1.2 of NUREG-0737. The nitrogen system provided a backup gas supp y to the air-operated steam supply valve for the steam-driven auxidiary feedwater pump. This backup was installed to provide-a " safety grade" auxiliary feedwater system that satisfies the single-failure criteria. Other cross connections, unich apparently did not leak air into the nitrogen system, hao 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 associated block 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. Generally, the gas in pressurized water reactor (PWR) waste gas systems is hydrugen rich and the oxygen concentration is controlled to prevent flammable gas mixtures. Flammable concentration of gus mixtures can be prevented by }imiting either the hydrogen or the oxygen concentration to less than 3 percent. To eliminate 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 i.e 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 flammable concentrations of hydrogen and oxygen in the waste gas 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 mainunance. No ignition or explosion was reported.
- m:1 IN 81-27 September 3, 1981 Page 2 of 2 It appears that licensees need to devote more attention to the potential. ef fects of nitrogen air system cross connections when systems are modified to 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 mixturer do not exist in tanks should be considered. No written response to this information ratice is required. If you need additional information with regard to this subject, please contact the Director of the appropriate NRC Regional Office. J
Attachment:
Recently-issued IE Information Notices l l t l l l l' l l l t' I
8. AJ Atttchment IN 81-27. l September 3, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No. Subject Issue Issued to 81-26 Compilation of. Health 9/3/81 All power reactor Physics Related Information facilities with an-Items OL or CP t 81-25 ' Open Equalizing Valve 8/21/81 All power reactor of Differential Pressure facilities with an Transmitter Causes Reactor OL or cP Scram and Loss of Redundant i - Safety Signals 81 Auxiliary Feed Pump 8/5/81 All power reactor Turbine Bearing Failures facilities with an OL or CP 81-23 Fuel Assembly Damaged 8/4/81 All power reactor due to Improper Positioning facilities with an i of Handling Equipment OL or CP 81-22 Section 235 and 236 7/31/81 All power research Amendments to the reactor, fuel Atomic Energy Act fabrication and of 1954 reprocessing, and spent fuel storage licensees and applicants 81-21 Potential Loss of Direct 7/21/81 All power reactor Access to Ultimate Heat Sink facilities with an OL or CP l 81-20 Test Failures of Electrical 7/13/C.1 All power reactor (' ' Penetration Assemblies facilities with an OL or CP 81-19 Lost Parts in Primary 7/6/81 M1 power reactor Coolant System facilities with an OL or CP OL = Operating Licenses CP = Construction Permits b n.
SSIN No.: 6835 Accession No.: 8103300413 IN 81-28 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 September 3, 1981 IE INFORMATION NOTICE NO. 81-28: FAILURE OF ROCKWELL-EDWARD MAIN STEAM ISOLATION VALVES ' Description of Circumstances: There have been several recent mechanical failures of the "Rockwell-Edwarc Flite Flow Stop Valve," a "Y" pattern globe valve made by Rockwell International, used for main steam isolaticn valves (MSIV) at some BWR facilities. Operating BWR facilities using this valve include Brunswick Unit 1 and 2, Cooper, Scane Arnold, Fitzpatrick, Hatch Unit 2, and Vermont Yankee. Of the seven total reported mechanical failures, five occurred at Brunswick Unit 2 and one each occurreo 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 clcsed 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 internals. 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 i from its threaded mate. Such rotation is believed to be caused by or aided by the propensity of steam flow to produce vibration and to create turning forces on valve internal components when antirotation restraint ic inadequate due to a failed or missing pin. Other contributing causes are balieved 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. j 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. L The individual failures are described below in chronological order. 1. In January 1976, the Brunswick Unit 2 "D" steam line inboard valve main disk separated from the piston. There was no evidence that pin (4) was installed. b k
m I!! 81-28 S:ptcmber 3, 1981 Page 2 of 2 2. On January 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 point (3). The corners of the pin experienced high stress, thereby causing cracking of the pin. 3. On January 15, 1981, the Brunswick Unit 2 "C" steam line outboard valve main disk separated from the piston. There was no evidence that pin (4) was ever inserted. This was deduced from finding the hole not deformed and ne 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 Unit 1 "C" steam line outboard valve stem disk 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 disk separated from the stem. Pin (3) was not properly installed. 7. On July 18, 1981, tne Brunswick Unit 2 "D" steam line inboard valve main disk separated from the piston. Pin (4) was not fully inserted. These failures have raised concerns regarding (1) the capability of the valve to perform its required safety function and (2) increased challenges to safety systems. !!owever, 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. l l Detailed investigation of the July failures at Brunswick Unit 2 led to the preliminary findings of possible excessive vibrations on valve internals from l steam flow turbulences created by the piping direction changes. In addition, there was evidence of loose thread connections. Further investigations and evaluations are currently in progress. Preliniinary corrective actions by the licensee include increasing the stem pin size from 5/16-inch to 3/8-inch, using. i-three pins instead of one or two pins, and increasing the hole depth 1/8-inch into the stem. In addition, corrective actions for the main-disk-to pistor i connection
- nclude adding en extra pin (of the same 1/2-inch size) and increasing l
the hole depth by 1/8-inch. This information is provided as notification of a potentially signifirant 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 cr 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 additional l information regarding this matter, please contact the Director of the appropriate NRC Regional Office. Attachments: 1. Figure 1 l l 2. Recently issued IE Information Notices
t 1. STEM DISK 2. MAIN DISK 3. ANTIR0TATION PIN - STEM DISK TO STEM 4. ANTIR0TATION PIN - MAIN DISK TO PISTON 5. STELLITED DISK GUIDES, 3 RIBS,120' APART (OUT OF SHOWN VIEW) 6. STEM i s t' V l ' } N . N k / ~ 1 l \\
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k. . s nj.x gn P. J h /* / am71 / / // I' ~ Y .x ~ 5TO.LITED --d 4 2.sraasx.4 i MAIN DISK ASSEMBLY OF ROCKWELL-EDWARD FL7TE FLOW STOP VALVE y i y 4 =t
Att chment ,c IN 81-28 September 3, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No. Subject Issue Issued to 81-27 Flammable Gas Mixtures 9/3/81 All power reactor in the Waste Gas Decay facilities with an Tanks in PWR Plants OL or CP 81-26 Compilation of Health 9/3/31 All power reactor Physics Related Information facilities with an Items OL or CP 81-25 Open Equalizing Valve 8/21/81 All power reactor of Differential Pressure facilities with an Transmitter Causes Reactor OL or CP Scran and Loss of Redundant Safety Signals 81-24 Auxiliary Feed Pump 8/5/81 All power reactor Turbine Bearing Failures facilities with an OL or CP 81-23 Fuel Assembly Damaged 8/4/81 All power reactor due to Improper Positioning facilities with an of Handling Equipment OL or CP 81-22 Section 235 and 236 7/31/81 All power research Amendments to the reactor, fuel Atomic Energy Act fabrication and of 1954 reprocessing, and spent fuel storage licensees and applicants 8L-21 Potential Loss of Direct 7/21/81 All power reactor Access to Ultimate Heat Sink facilities with an OL or CP 81-20 Test Failures of Electrical 7/13/81 All power reacter Penetration Assemblies facilities with an OL or CP 81-19 Lost Parts in Primary 7/6/81 All power reactor Coolant System facilities with an OL or CP 'OL = Operating Licenses CP = Construction Permits -}}