Information Notice 1988-56, Potential Problems With Silicone Foam Fire Barrier Penetration Seals

Potential Problems With Silicone Foam Fire Barrier Penetration Seals

ML031150042
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	08/04/1988
Revision:	0
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-88-056, NUDOCS 8807290111
Download: ML031150042 (9)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555August 4, 1988NRC INFORMATION NOTICE NO. 88-56: POTENTIAL PROBLEMS WITH SILICONE FOAMFIRE BARRIER PENETRATION SEALS

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

This information notice is being provided to alert addressees to potentialproblems in their installed fire barrier penetration seals that could resultin the reduction of fire-resistive capabilities for protection of safety-relatedredundant equipment and electrical power and control circuits. It is expectedthat recipients will review this information for applicability to their facili-ties and consider actions, as appropriate, to avoid similar problems. However,suggestions contained in this information notice do not constitute NRC require-ments; therefore, no specific action or written response is required.

Description of Circumstances

.In May 1987, B&B Promatec submitted a 10 CFR Part 21 notification advising NRCthat some silicone foam fire barrier penetration seals at Wolf Creek NuclearGenerating Station (WCNGS) did not meet minimum requirements. The noncon-forming conditions reported by B&B Promatec were described as voids, shrinkage,and lack of fill. The conditions were not obviously visible because they weremasked by fire-resistant boards that were typically installed on both sides ofa wall penetration and the bottom side of a floor penetration. WCNGS licenseepersonnel found the problems during replacement of damaged fire-resistant boards.Thereafter, WCNGS adopted an inspection methodology in which the fire boardswere removed, the silicone foam barriers were inspected and reworked as neces-sary, and the boards replaced.Initial results from sample inspections indicated that over 25 percent of theinspected seals were nonconforming. Additional inspections performed beforeOctober 1987 revealed that 107 of 430 inspected seals required repair or reworkand that 65 of the 107 contained voids. The licensee for WCNGS subsequentlydetermined that the void problem was caused, at least in part, by underfillat the time of installation. As a result of the WCNGS report, NRC has beenevaluating whether the silicone foam nonconforming conditions found at WCNGShave generic applicability for plants other than those notified by B&B Promatec.Part of this evaluation included a review of abstracts of licensee event reports.880729011 Z-D IN 88-56August 4, 1988 Information obtained from this review indicates that a number of licensees havereported various fire barrier penetration seal nonconforming conditions. Someof the previously reported nonconforming conditions appear to be similar to thosereported for WCNGS but are not limited to any particular vendor or installer.Silicone foam was the only fire barrier penetration seal material that wasspecifically mentioned in the information reviewed, although some reports didnot specifically identify the particular sealing material for the affected seals.On the basis of this information, NRC believes that if generic problems exist,they may be limited to only silicone foam fire barrier penetration seals butnot to any particular vendor or installer.Discussion:This notice alerts addressees of the possibility that some installed fire barrierpenetration seals may contain nonconforming conditions such as splits, gaps,voids, and lack of fill in the sealing material. These conditions may not bedetected during routine inspection because the surface of the seal material istypically covered by a fire-resistant dam material. Information that Is avail-able suggests that the extent of the possible problem may be limited to firebarrier penetrations filled with silicone foam material.Silicone foam has been used extensively as a fire barrier penetration sealingmaterial in many nuclear power plants since the early 1970's. For siliconefoam seals installed since the mid 1970's, the silicone sealing material hasbeen formulated of a two-component RTV 3-6548 base product manufactured by DowCorning. The silicone foam seals are produced by mixing the two components,which then chemically react ("snap") a short time after they are mixed. Theresulting snap causes gas formation and material expansion, which produces asilicone foam cell structure. Experience with silicone foam indicates thatany one of many factors could affect the adequacy of the final seal instal-lation. These factors include the method of installation (e.g., dammingtechnique), technical and quality control of material, material mixing process,pouring and curing process, method of final inspection, training and experienceof installing personnel, and environmental factors, such as temperature andhumidity. Loss of control for any one of these factors could result in sealsthat do not meet minimum requirements.In many silicone foam fire barrier penetration seals, a permanent dam constructedfrom a fire-resistant material is used. These dams must be present if they werepart of the qualified seal design. Normally, a permanent dam is located on thebottom of floor and ceiling penetrations and on both sides (although sometimesonly on one side) of wall penetrations. One common installation method used inthe past called for installing the permanent damming material first so that itwould contain the liquid seal material during pouring and curing. Since thepermanent dam was part of final installation and because removal and reinstal-lation of the dam could be difficult and time consuming, final inspection ofmany silicone foam seals was performed with the permanent dam in place. Whenthis approach was used, final determination of whether a proper seal had beenattained was made without direct visual inspection of the seal surface, whichappears to be a questionable practice. Instead, indirect methods of checking, IN 88-56August 4, 1988 such as tapping on the dam or inserting probe wires through the dam, were used.In addition to precluding direct visual inspection of a new seal, installed damsalso hinder subsequent detection of nonconforming conditions that may have beenpresent since initial installation or that may have developed after initialinstallation.As mentioned earlier, licensees have reported various fire barrier penetrationseal nonconforming conditions in the past. The reported conditions that suggesta generic problem are discussed below:Voids -One nonconforming condition for silicone foam seals is the presence ofvoids. Voids can be created in a number of ways. First, proper preparation ofthe volume to be sealed is required before liquid fill. Proper preparationincludes ensuring that the penetrating items (pipes and cables) have sufficientseparation to permit the liquid to fill all the space in the volume. Second,the mixed sealing material requires a sufficiently long "snap" time to ensurethat the expansion process does not prevent free flow of sealing liquid to allspaces in the volume. Third, the gas formed during the expansion process needsto diffuse from the material without creating large gas bubbles or pockets.Finally, a sufficient quantity of sealing material must be injected to ensurethat all spaces within the volume will be filled.Gaps -Another nonconforming condition is the presence of gaps or the pullingaway of silicone foam material from the surface of penetrating items or insidesurfaces of the fire barrier. In some cases, these gaps extend only a shortdistance into the seal thickness. In a few cases, gaps have been observed toextend completely through the entire thickness of the seal. Causes of the gapshave been variously given as failure to inject sufficient sealing materialduring filling, bulging of damming material, shrinkage of silicone foam, andcontraction of silicone foam caused by a temperature change. The physicalcharacteristics of the silicone foam are such that a 1 percent reduction involume can be expected for a decrease of 200F in temperature.Splits -A third nonconforming condition is splitting (cracking of solidifiedmaterial) of the silicone foam material. This condition was not reported atWCNGS but was reported by other licensees. In conversations with NRC, B&BPromatec stated that the reasons for silicone foam splitting are not completelyunderstood and that splitting is a topic of discussion in the power sealer andinsulation industry.Some of the actions taken by licensees as a result of finding nonconformingsilicone foam fire barrier penetration seals include (1) programs for inspec-tion and periodic reinspection of installed seals, (2) repair of nonconformingseals, (3) evaluation of alternative materials for repairing old seals and in-stalling new seals, and (4) development of alternative methods for installingand inspecting new silicone foam seal IN 88-56August 4, 1988 No specific action or written response is required by this information notice.If you have any questions about this matter, please contact one of the technicalcontacts listed below or the Regional Administrator of the appropriate regionaloffice.es.osslDrDivision of Operat nts AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Joseph J. Petrosino, NRR(301) 492-0979C. Vernon Hodge, NRR(301) 492-1169

Attachment:

List of Recently Issued NRC Information Notices AttachmentIN 88-56August 4, 1988 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. -Subject Issuance Issued to88-5588-5488-53Potential Problems Causedby Single Failure of anEngineered Safety FeatureSwing BusFailure of Circuit BreakerFollowing Installation ofAmptector Direct TripAttachmentLicensee Violations of NRCRegulations, Which Led toMedical DiagnosticMisadministratfonsFailure of IntrauterineTandem of FletcherApplicator BrachytherapyDevices During PatientTreatment8/3/887/28/887/28/887/27/88All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All manufacturers anddistributors of radio-pharmaceuticals forhuman use, nuclearpharmacies, andmedical licensees.Medical licensees.88-5288-46,Supplement 1Licensee Report ofDefective RefurbishedCircuit Breakers7/26/88All holders of OLsor CPs for nuclearpower reactors.88-5188-50Failures of Main SteamIsolation ValvesEffect of CircuitBreaker Capacitanceon Availability ofEmergency Power7/21/887/18/88All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.OL = Operating LicenseCP = Construction Permit IN 88-56August 4, 1988 No specific action or written response is required by this information notice.If you have any questions about this matter, please contact one of the technicalcontacts listed below or the Regional Administrator of the appropriate regionaloffice.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Joseph J. Petrosino, NRR(301) 492-0979C. Vernon Hodge, NRR(301) 492-1169

Attachment:

List of Recently Issued NRC Information NoticesTransmitted from DRIS on June 22, 1988*SEE PREVIOUS CONCURRENCES*SEE PREVIOUS PAGE FOR CONCURRENCE*OGCB:DOEA:NRRCVHodge07/22/88*D:DEST:NRRLShao07/29/88*RPB:ARMTechEd07/19/884 RRCERos/07ttj /88*C/OGCB:DOEA:NRRCHBerlinger07/26/88*D:DRIS:NRRBKGrimes07/28/88i IN 88-XXAugust xx, 1988 No specific action or written response is required by this Information notice.If you have any questions about this matter, please contact the technicalcontact listed below or the Regional Administrator of the appropriate regionaloffice.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation

Technical Contact:

Joseph J. Petrosino, NRR(301) 492-0979

Attachment:

List of Recently Issued NRC Information NoticesTransmitted from DRIS on June 22, 1988*SEE PREVIOUS CONCURRENCES*SEE PREVIOUS PAGE FOR CONCURRENCE*OGCB:DOEA:NRRCVHodge07/22/88D:DPLSh "o:'07/ /88*RPB: ARMTechEd07/19/88*C/OGCB:DOEA:NRRCHBerlinger07/26/88*D:DRIS:NRRBKGrimes07/28/88D:DOEA:NRRCERossi07/ /88 IN 88-XXJuly xx, 1988 No specific action or written response is required by this information notice.If you have any questions about this matter, please contact the technicalcontact listed below or the Regional Administrator of the appropriate regionaloffice.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation

Attachments:

Joseph J. Petrosino, NRR(301) 492-09791. Partial List of Reports of Nonconforming ConditFire Barrier Penetration Seals2. List of Recently Issued NRC Information Noticesions inTransmitted from DRIS on June 22, 1988*SEE PREVIOUS CONCURRENCESOGCB:DOEA:NRRCVHodge07/7,,V88C/OGCB:DO A:NRRCHBerlinger07/6&88*RPB:ARMTechEd07/19/88D:DOEA:NRRCERossi07/ /88P/reB .tIRz. ~*eD40M :SK nme.7bslt B%&^

I,. 88-04, Supplement 1July xx, 1988 No specific action or written response is required by t Us information notice.If you have any questions about this matter, please cotacV the technicalcontact listed below or the fegional _idministrator of the appropriate regionaloffice.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation

Technical Contact:

Joseph J. Petrosino, NRR(301) 492-0979Attachments /' i¢- 4e 7 X1. Partial ary-of NonconformingAPenetration Seals2. List of Recently Issued NRC Information NoticesAej fe <7. {DE 5 J0OGCB:DOEA:NRRCVHodge07/ /88RVIB:DRIS:NRRJJPetrosino07/ /88ECEB:DEST:NRRDKubicki07/ /88(PB:ARMTechEd07///i/88D/DOEA:NRRCERossi07/ /88C/OGCB: DOEA:NRRCHBerlinger07/ /88