ML20010G682

Part 21 Rept Re Heating, Ventilation & Air Conditioning Ductwork.New Design Info Shows Ducts Could Collapse If Subjected to High Negative Pressure Due to Dirty Filters. Stiffener Angles Will Be Added

ML20010G682
Person / Time
Site:	Three Mile Island
Issue date:	09/16/1981
From:	Barker N GILBERT/COMMONWEALTH, INC. (FORMERLY GILBERT ASSOCIAT
To:	Stello V NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
References
REF-PT21-81-494-000 PT21-81-494, PT21-81-494-000, NUDOCS 8109220405
Download: ML20010G682 (2)

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Gilbert / Commonwealth engincars and consuitants r x.

G!LBERT ASSGulATES, INC., P. O. Box 1498, Reading, PA 19603/Tel 215-775-2600/ Cable Gitasoc/ Telex 836-431 \N L September 16, 1981 y '

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United States Nuclear Regulatory Commission _.

Office of Inspection and Enforcement ' Qgeca ,

Washington, DC 20555 hi. V. Stello

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<,N-Attention:

Director \ 9/'/ j 5* Y

Subject:

Reportable Event -

HVAC Ductwork Subject To Negctive Pressure

Dear Mr. Stello:

This documents my report under 10CFR Part 21 to Mr. Roy Woods, by telephone, on September 11, 1981.

Individual Who Reported Norman R. Barker, Gilbert Associates - Quality Assurance Division - General Manager, at the above address, made the call.

Facility Involved Three Mile Island Unit No. 1 - GPU Nuclear Components Involved Two (redundant) duct sections connecting the Control Building Emergency Recirculation Fans (AHE-18A and B) with their associated filter plenums (AHF-3A and B). Each of the ducts is 60" X 60" square and approximately 15 feet long.

Nature of Defect Based on new design information (see below) it appears that the referenced ducts could collapse if subjected to high negative pressure resulting from dirty filters. Collapse, with or without rupture, would result in restricting air flow, preventing the system from performing its safety function.

Date Information Obtained The QA Division General Manager was informed of the final results of the engineering evaluation on September 11, 1981.

%h S 8109220405 810914 gDRADOCK 05000289 525 Lancaster Avenue. Readeg. PA, Morgantown Road, Green Hdis. Resom PA 215 775-2800 ,

209 East Washegton Avenue. Jacksor. MI 517 708-3(00,80 Pee Street New York. NY ! 12 s24480

A Mr. V. Stello Page 2' September 16, 1981 Corrective Action

- A review of GAI design of safety related hVAC ducts on other domestic nuclear

' projects indicates that the potential problem exists only with the two re-ferenced ducts. There is a possibility that a detailed analysis of these two ducts would prove them to be adequate. In lieu of the analysis, GAI'has-recommended that sur-A emental stiffener angles be welded - to the existing stiffeners as this was expedient and cost effective. CPU Nuclear will be responsible for implementation of corrective action.

Additional Information Prior to 1975, Gilbert Associates designed HVAC ductwork based on the 1969, 2nd Edition of the Sheet Metal and Air Conditioning Contractor National Association (SMACNA) High Velocity Duct Construction Standard. We recently learned through a discussion with a representative of SMACNA, that tests performed in 1971/1972 by SMACNA, proved that some ducts constructed in accordance with the referenced standard failed tests for negative pressure.

In reviewing the 1975, 3rd Edition of the SMACNA standard, it is obvious that most duct sizes in most pressure categories have been strengthened by specifying heavier steel members, and it also indicates that negative pressures require additional reinforcing.

The above information raised the concern that certain ducts designed' and constructed to the 1969 SMACNA standard could be operating in a marginal range. Our review has limited our concern to the two referenced ducts.

Very truly yours, t h '

N. R. Barker Vice President & General Manager Quality Assurance Division NRB:kb cc: H. Lorenz T. M. Demers V. Stello - 3 U. Potapovs - NRC Region IV Document Management Branch' i

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