ML20198Q643
| ML20198Q643 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/30/1986 |
| From: | Carey J DUQUESNE LIGHT CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 2NRC-6-055, 2NRC-6-55, 86-05, 86-5, NUDOCS 8606090289 | |
| Download: ML20198Q643 (4) | |
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'Af Ducluesrie Udit Beaver Valley No. 2 Unit Project Organization 2NRC-6-055 SEG Bu11di"9 (412) 643 5200 sEnkpo!.PA
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15077 May 30, 1986 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 ATTENTION:
Dr. Thomas E. Murley Administrator
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Diesel Generator Exhaust Hood Insulation Failures Report (86-05)
Gentlemen:
This Potentially Reportable Signi-ficant Deficiency Report relating to diesel generator exhaust hood insulation failures is being submitted pursuant to the requirements of 10CFR50.55(e).
This is a final report.
It is anti-cipated that no additional reports will be submitted.
DUQUESf:E LIGHT COMPANY By Jfj0(J6 rey
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Vice President GH0/kam Attachment cc:
Mr. P. Tam, Project Manager (w/a)
Mr. J. M. Taylor, Director (3) (w/a)
Mr. W. Troskoski, Sr. Resident Inspector (w/a)
Mr. L. Prividy NRC Resident Inspector (w/a)
INP0 Records Centar (w/a)
NRC Document Control Desk (w/a) 8606090289 060S30 PDR ADOCK 05000412 g
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f Duquesne Light Company Beaver Valley Power Sation Unit No. 2 Project Organization Regulatory Affairs Department Report on a Potential Significant Deficiency Involving the Structural Failure of Pipe Insulation or. the Diesel Generator Exhaust Nozzles and Insulation Within the Reinforced Concrete Exhaust Hoods 1)
SUMMARY
During testing of diesel generator 2EGS*EG2-1, the thennal insulation lining of the exhaust hood and the exhaust pipe collapsed.
This in-sulation could have blocked the screened outlets of the exhaust hoods, thus increasing diesel exhaust back pressure and possibly decreasing diesel power output.
Also, on March 15, 1986, construction debris and the asphalt and gravel roofing of the dic:sel generator building were ignited by the high temperature exhaust gasses.
2)
IMMEDIATE ACTION TAKEN The fire was extinguished immediately by site security forces using portable C02 extinguishers.
The fire brigade wet the entire roof with a water spray.
A fire watch was established for the rmaining portion of the load test (approximately 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> duration).
After this test, all oper-ational testing of both diesel generators was suspended until a pre-liminary assesment was performed by Engineering.
Subsequently, it was determined that with the tenporary reoval of the screens and the addition of several heat shields, no permanent damage would occur during the testing period.
These temporary measures were implemented and diesel testing was allowed to recommence.
3)
DESCRIPTION OF THE PROBLEM There are two 38 in. diameter exhaust nozzles per diesel generator.
The exhaust nozzles are insulated with calcium silicate insulation held together by aluminum jacketing.
The diesel generator exhaust nozzles discharge beneath a reinforced concrete hood which provides protection from tornado missiles.
The inner surfaces of the hood are lined with a 5 in, composite section of Foamglas insulation.
m
Reinforced Concrete Exhaust Hoods Page 2 The opening in the underside of the reinforced concrete hood, through which diesel exhaust is discharged to the atmosphere, are protected by No. 2 mesh, stainless steel screens with a wire diameter of 0.063 in.
(" bird screen").
During testing of the diesel generator, the aluminum jacketing failed, causing the calcium silicate insulation to fall onto the screens.
Additionally, the adhesive that bonded the composite section of Foam-glas insulation failed, causing the insulation to fall onto the scre-ens.
The accumulation of aluminum jacketing, calcium silicate insu-lation, and Foamglas insulation on the screens could restrict the exhaust flow, and possibly result in exhaust back pressures in excess of design requirements.
The roof of the diesel generator building in the areas beneath the exhaust hoods is protected by Johns Manville JM-23 firebrick.
The brick is multi-layered with a total thickness of at least 1 f t-0 in.
on the roof surface.
4 The firebrick was not affected by the high temperature exhaust gasses.
However, the exhaust gasses affected the surrounding asphalt and gravel roofing, causing it to melt.
4)
ANALYSIS OF SAFETY IMPLICATIONS The emergency diesel generators are required during design basis events to supply electric power to the safety-related components.
The collapse of the exhaust pipe insulation and exhaust hood wall insulation could significantly block the diesel exhaust flow by col-lecting on the discharge screens.
This could result in high diesel exhaust back pressure and subsequent reduction of diesel power oc diesel trip.
5)
CORRECTIVE ACTION TO REMEDY THE DEFICIENCY The aluminum jacketing of the calcium silicate pipe insulation has been replaced with stainless steel jacketing.
Subsequent testing of the diesel generator has showed the stainless steel jacketing is adequate to withstand the high temperatures.
The thickness of the Foamglas insulation and the method attaching the Foamglas to the reinforced concrete surfaces is being reviewed to provide adequate protection of the concrete for the accident cond-itions during which the diesel generators are required.
The adhesive that will be used is a refractory cement adhesive that is designed for temperatures far in excess of the temperatures readings that have been observed.
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i deinforced Concrete Exhaust Hoods e'
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The extent of the roof area covered by firebrick will be increased to provide adequate protection of the asphalt and gravel roofing for the accident conditions during which the diesel generators are required.
Insulation will be added to adequately protect the walls adjacent to the exhaust hood.
4 6)
FINAL REPORT This is the final report on this subject.
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