ML19350F097

Ro:On 810613,C-E Advised That Pipe Fittings Immediately Upstream of RCS Code Safety Valves Do Not Have Proper Inside Diameter.Reduction in Inlet Pipe Diameter Does Not Constitute Safety Hazard.Followup Rept Forthcoming

ML19350F097
Person / Time
Site:	Calvert Cliffs
Issue date:	06/16/1981
From:	Russell L BALTIMORE GAS & ELECTRIC CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 8106240209
Download: ML19350F097 (2)

Text

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June 16,1981

% ems Mr. Boyce H. Grier, Director Docket No. 50-317/30-313 Office of Inspection and Enforcement License No. OPR-33/DPR-69 IJ.S. Nuclear Regulatory Commission

• Region 1 l 631 Park Avenue King of Prussia. PA 19406

$UBJECT: LER 3162 (11.t): 1.ER 31-28 (t!-2)

Dear Mr. Griert ,

This letter is to confirm our verbal notification to your Mr. Ralph Architzel as required by Technical Specification 6.9.1.3.h, (errors discovered in transient or accident analyses) of an error discovered in the pipe sizing Reactor Cocolant System (RCS) code saf ety valves.

On Saturday, June 13, 1981 the Combustion Engineering Site Representative informed the Plant SupertTitendent that the pipe fittings immediately upstream et the Reactor Coolant System (RCS) code saf ety valves do not have a proper inside diameter. Calvert Clifis Units I and 2 were designed and constructed vith 21/2 inch schedule 160 pipe and, 2500 pound fittings immediately upstream of their Dresser Model 31739A Saf ety Valves.

These fittings have an inside diameter of 2 1/3 inches. The dresser interfsce requirements for this modet valve is a minimum upstream inside diameter of 21/2 inches, although this was not explicitly stated on their interf ace drawing.

The reduced inlet pipe diameter for tnese valves will reduce the valve discharge capability and invalidate the assumptions in plant overpressure protection report and any saf ety analyses which result in actuation of the pressurizer safety valves. While it is not possible to precisely predict the change in discharge capacity, it is believed to ':e small since the actual bore diameter of the Model 31739A Valve is only sbeut i 7/8 inches.

Since the valve bore is the limiting flow ares the only eff ect a short length upstream l

restriction will have is to modestly reduce the pressure upstream of the flow nozzle l l

thereby modestly reducing the critical flow rate.

Parametric contingency analyses recently performed in support of the EPRI Safety and Relief Valve Test Program have demonstrated a larte margin in the sizir:g of tSe pressurizer saf ety valves f or Calvert Cliffs. Based on the licensing methods for these 5 "~~ uy P00R 0 @ w

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tants, the calculated required sniety valve capacity is more than an order of magnitude icw that specified ior the olant. It is mlikely that the reduced valve capacity rcsulting from the smaller inlet piping could have a significant impact in light of this Theref ore, it is concluded that the above desc-ibed reduction in jarge design margin.intct pipe diamater for the Dresser Model 31739A Safety Valve does not cor substantial saf ety hazard for Calvert C1Lifs Units 1 and 2.

A more complete description of the event will be contained in the follow-up report.

Very truly yours, Y

1.. B. Russell Plcnt Superintendent k

" 4 f.CRammr .

cc: 3. A. Tiernan R. M. Douglass Director, Office of Management Information and Program Control R. E. Architzel L. B. Russell

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