ML20004B012

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Provides Addl Info to Support 800709 Request for Relief from Inservice Insp Requirements on Check Valves SI-159 & SI-160. Proposes 5-yr Alternating Insp Schedule,Based on Results of 1980 & Proposed 1981 Insps
ML20004B012
Person / Time
Site: Fort Calhoun Omaha Public Power District icon.png
Issue date: 05/20/1981
From: William Jones
OMAHA PUBLIC POWER DISTRICT
To: Clark R
Office of Nuclear Reactor Regulation
References
NUDOCS 8105270111
Download: ML20004B012 (3)


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M Omaha Public Power District 1623 MANNEY s OMAHA. NEsRASMA 68102 a TELEPHONE 536 4000 AREA CODE 402 May 20, 1981 n

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Mr. Robert A. Clark, Chief  ?;

U. S. Nuclear Regulatory Commission Office of idclear Reactor Reg'dation W' 4 N ?\ 'e Division of Licensing g y h,3 LV Operating Reactors Branch Nc. 3 'T ..;;,

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Washington, D.C. 20555 ,c ,

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Reference:

Docket No. 50-285 3; y,

Dear Mr. Clark:

N The attached is forwarded in response to several questions re-sulting from a telephone discussion on March 23, 1981, between Messrs.

C. Trarrmell and E. Chellf ah of the Commission and Messrs. T. Patterson, J. Fluehr, and R. Kellogg of Omaha Public Power District. The dis-cussion concerned the District's request dated July 9, 1980, for relief from Inservice Inspection (ISI) requirements on two check valves, SI-159 and SI-160.

The District's July 9,1980, letter requested a five year alter-nating inspection schedule on the two check valves, as a result of the inspection of one of the two check valves during the 1980 refueling outage. This inspection showed the valve to be in excellent condition.

However, the Commission has asked for additional information in support of the requested relief. The answers to Mr. Chelliah's specific questions are attached. Additionally, the District proposes that, during the 1981 refueling outage, the second check valve (SI-160) be inspected. If the insoection of SI-160 also shows no significant deterioration of valve internals, the District would then initiate a five year alternating in-spection schedule on the two check valves. The District believes this represents a viable compromise to Messrs. Trammell and Chelliah's position to test SI-160 this refueling and then inspect at alternating three year intervals.

Sincerely,

~

W. C. Jones hov7

.s Division Manager /

Production Operations ///

WCJ/KJM/TLP:jmm Attachment cc: LeBoeuf, Lamb, Leiby & MacRae

. 1333 New Hampshire Avenue, N.W.

l Washington, D.C. 20036 81e527e111

g RESPONSE TO COMMISSION'S QUESTIONS OF MARCH 23, 1981, TELECON Question 1 With the Duo-Chek valve design, do both halves of the check valve open independently? If so, can adequate flow be provided through one half the valve?

Response

The valve design is such that two halves of each valve operate independently of each other. First, the normal operating character-istics shall be examined. The valve is a 24-inch Mission Duo-Chek check

, valve. It consists of two semicircular plates, hinged along the diameter of the valve and spring loaded to remain closed when no pressure dif-ferential exicts. According to the manufacturer's flow chart, this valve would allow a flow rate of 180,000 gallons per minute if the pressure drop across the valve were 100 ft. water column head. In the application in the recirculation lines, the pressure head would be considerably less. The maximum accident flow rate in the line con-taining SI-159 is 4,400 gpm. The maximum flow rate in the line con-taining SI-160 is 2,800 gpm. The flow rate of 4,400 gpm is the limiting flow to be considered in analyzing the check valves. During the re-circulation modes, this flow is supplied to two containment spray pumps which require a net positive suction head (NPSH) of 16.8 ft. and to a high pressure safety injection pump with a required NPSH of 13 ft. -

Thus, the flow to the containment spray pumps is the limiting case.

According to the FSAR, the minimum available suc'. ion head to a con-tainment spray pump is 20.79 ft. This is calculated by subtracting the equivalent pipe and valve friction in feet and the centerline elevation of the pump from the minimum water elevation in the containment during the recirculation mode of operation. Thus, 996.8 ft. - 973.25 ft. -

, 2.76 ft. = 20.79 ft. The excess head for the spray pump is 20.79 ft. -

16.8 ft. = 3.99 ft. An assumption is made that a 4,400 gpm flow rate through the valve exists which contributes about 0.27 ft. head loss to the total head loss. Since 3.99 ft. excess is available, the total possible flow through the valve at 3.99 + 0.27 = 4.26 ft. is determined from the manufacturer's flow chart to be about 33,000 gpm. Comparing the possible flow through a properly functioning valve of 33,000 gpm with the required flow rate of 4,400 gpm, it is clear that the valve would permit more than sufficient flow should half of the valve be stuck in the closed position.

Question 2 -

What was the radiation exposure received as a result of the in-

. spection performed on SI-159?

Response

The total exposure for this work was 40 mR during a total of 16 manhours. Access to SI-160 is more limited, and it is expected that the manhours required to remove, inspect, and replace this valve would be at lea:t 30. The radiation exposures would similar1v Jouble to about 80 mR.

Question 3 ,

The District has indic&ted that a large volume of waste is gener-ated as a result of draining the Safety Injection and Refueling Water Tank (SIRWT) and the 24-inch outlet piping. How much waste is actually generated?

Response

Prior to removing valves SI-159 or SI-160, the SIRWT and associated piping must be drained. There are isolation valves between the SIRWT and the check valves. However,- they are metal disc, metal seat butter-fly valves not designed to be leak-tight. The SIRWT can be drained by pumping to the reactor and refueling cavities. Portable sump pumps are required to remove the last Ih to 2 ft. of water from the tank. This water is pumped up through hoses to the spent fuel pool. The recir-culation lines cannot be drained in a similar manner. The line con-taining SI-160 holds about 4,500 gallons of radioactively contaminated water requiring disposal. The waste evaporator concentrates the liquid to h of the original volume. This effluent requires 38 drums for final disposition. The present monthly waste allotment is 571 ft3 , or about 76 drums. The fact that a refueling outage would be underway at this time, creating a substantial waste burden, adds to the difficulty of waste management. Thirty-eight (38) more drums would be a considerable additional burden.

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