ML20085E703
| ML20085E703 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/23/1976 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8308160522 | |
| Download: ML20085E703 (3) | |
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TENNESSEE VALLEY AUTHORITY N
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lir. Hornan C. !!oselcy Director 2-
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6 U.S. Nuclear Regulatory Commission Region II - Suite 818 230 Peachtree Street, NW.
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Dear Mr. !!oseley:
BR0' INS FERRY NUCII.AR PLANT UNIT 3. - REPORTABLE DEFICIPNCY - RESTRAINTS FOR STANDBY GAS TREAT 11ENT SYSTElf DUCTS Initial report of the subject reportable deficiency was made to C. R. Elingler, NRC-IE, Region II, on Juno 15, 1976.
In compliance with paragraph 50.55(e) of 10 CFR Part 50, we are enclosing a final report of the deficiency.
As discussed with Mr. Klingler on July 22, 1976, we regret that this report is being outmitted past the established dua date. Ua will attempt to prohibit subuitting late reports in the future.
Very truly yours, J. E. C111 eland Assistant Manager of Power Enclosure CC (Enclosure):
Dr. E. Volgenau Director '/
Office of Inspection and Enforcement U.S. Nuc3 car Regulatory Commission Washington, DC 20555
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PDR b$c$ h An Equal Opportunity Employer
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ENCLOSUPJ:
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EJI;G FFRRY ITCLE/dl }Udii' (THITO 1 /d:D 3 RESTRAI!.TS FOR STid!DLT C/.3. TitEATIEI.'T SYSTDI DUCTS DDIt235 FIllAL REPORT. " " *'
On June 35, 1976, an initial report was made by telephone to IIRC-0TE Region II Inspector, Gerald R. Klingler, by 'd. K. Anders, T. U. Earhalcw, L. W. Blevins, and D. J. Cash in accordance with 10CFR50 55(e).
This is the final report on this deficiency and covers both units 1 and 3 Description of Deficiency While conducting a field inspection of the installation of seismic restraints on ductuork, an engineer found two instances where the actual installation did not conform to design criteria which had been issued on July 9,1970.
An east-west run of 28-inch duct for the Standby Gas Treatment System (SGTS) between column lines R15 and P20 and between the p and q lines at elevation 621 feet of unit 3 had restraints installed in locations different from those shown on the design drawing.
Also, the drawing shows three restraints on a hori-zontal run, but only two were actually installed.
The other case of inadequate seismic restraint was along this same duct in a north-south run through the unit 1 reactor building.
IIo restraints had been installed on this run since the design drawing does not show any. However, the design criteria were revised on April 22, 1971, to specifically address the restraint of this 28-inch duct.
In this revision it was stated that a spacing of 52.0 feet between horizontal seismic restraints provides adequate support. The run of duct in the unit 1 reactor building was approximately 91 feet between restraints and therefore was inadequately restrained.
Cause of Deficiency The deficiency in the unit 3 reactor building resd1ted frem a misinterpretation of the design drawing which showed the locations for the 28-inch duct and its seismic restraints. The construction personnel interpreted the drawing as requiring three restraints.
They located one restraint uhere the ductuork passed through the floor to another elevation. The other two restraints were located along the horleontal run at points located in accordance with the revised April 22, 1971, criteria.
These locations did not coincide with the ones shown on the drawings.
Also, these field changes were not reviewed by design per-sonnel until the field inspection occurred, approximately 18 months after the work was complete.
The design personnel had intended that the drawing should require four restraints, one at the floor penetration and three along the horizontal run. 1:rwever, only the three locations along the hori: ental run were shown. A detail showing the fourth restraint located at the floor pene-tration uns not referenced on the plan view and uns overlooked by construction personnel.
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The deficiency in the unit 1 reactor buildinh $[sulted from the drawing chowing the 28-inch duct and its seirmic restraints not being revised to reficct the April 22, 1971, changes to the design criteria.
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construction personnel were not aware that an additional restraint should have been located on that run of duct.
Safety Imolications The SGTS provides a~ means for minimising the release of radioactive material from the containment to the environmsnt by filtering and exhausting the atmosphere from any, or all, zones of the reactor building during containment isolation conditions.
All portions of the system, including the 28-inch duct, are designed to withstand the safe shutdown carthquake without impairing the ability of the system to operate at design capacity. The 28-inch duct is co==on to all three trains of the SGTS and is a continuous run throughout the reactor building.
Failure at a given point in the duct could isolate all sections upstream of that point.
The SGTS would not be able to provide filtration and ventilation to areas of the plant served by the isolated sections of duct.
This deficiency reduced the ability of the duct to withstand the safe shutdown carthquake.
Description of Corrective Action The corrective action consists of two activities:
revising the applicable drawings to show duct support locations which meet current requirements and installing additional restraints. The drawing showing the three restraints on the horizontal run of duct in unit 3 has been revised to reference the detail of the fourth restraint and to show the as-installed locations of the two restraints originally installed on this run. The drawing showing the 91-foot duct run in unit 1 reactor building has been revised to place a restraint at the midpoint of the duct run.
A third restraint has been installed on the horizontal duct run in unit 3
' A restraint has been added at the midpoint of the 91-foot duct run in unit 1.
Means Taken to Prevent a Recurrence g
The entire run of 28-inch duct has been field inspected to insure that its ceismic restraints are installed as designed.
Also, as a result of an earlier similar deficiency, a memorandum has been issued by the Director of Engineering Design requesting Project Managers to reevaluate existing drawing verification controls. This memorandum also instructed Project Managers to make appropriate changes or* additions to detailed project level engineering procedures to assure compliance with procedure EN DES-EP 310, " Design verification Methods and Performance of Design Verifications." TVA believes that compliance with this memorandum reduces to an acceptable level the change of a similar deficiency recurring.
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