ML20237G206

Forwards Addl Info Re NUREG-0737,Item II.D.1, Performance Testing of Relief & Safety Valves, Per NRC 861231 Request

ML20237G206
Person / Time
Site:	Maine Yankee
Issue date:	08/13/1987
From:	Whittier G Maine Yankee
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM GDW-87-109, MN-87-92, NUDOCS 8708240003
Download: ML20237G206 (9)

Text

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MAIRE HARHEE ATOMICPOWERCOMPARUe ,uausrlll e lls h (207) 623-3521 e

August 13, 1987 MN-87-92 GDH-87-109 United States Nuclear Regulatory Commission Attention: Document Control Desk Hashington, D. C. 20555

References:

(a) License No. DPR-36 (Docket No. 50-309)

(b) USNRC Letter to MYAPCo dated December 31, 1986, Request for Additional Information, Item II.D.1 - NUREG-0737 (c) MYAPCo Letter to USNRC dated March 31, 1987 (MN-87-41)

Subject:

Response to Request for Additional Information, Item II.D.1 of NUREG-0737, Performance Testing of Relief and Safety Valves Gentlemen:

Reference (c) provided a partial response to Reference (b).

Enclosed is the additional information that was requested. He believe this information is complete, however, if you have any questions, please contact us.

Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY

. h)) /)y G. D. Whittier, Manager Nuclear Engineering and Licensing GDH/bjp Enclosure cc: Mr. Victor Nerses Mr. Hilliam T. Russell Mr. Pat Sears Mr. Cornelius F. Holden O

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. .. MolNE YANKEE QTOMIC POWER COMPANY ATTACHMENT A

-MAINE YANKEE RESPONSE TO REQUEST FOR

, ADDITIONAL INFORMATION ITEM II.D.1 - NUREG-0737 RELIEF AND SAFETY VALVE TESTING OUESTION 2 Provide the maximum expected backpressure for the safety valves and PORVs at Maine Yankee.

RESPONSE

The maximum expected backpressure behind the safety valves at Maine Yankee for the revised piping was computed to be 457 psia. The piping was analyzed using a steady flow, two-phase, homogeneous-equilibrium model along with the ASME steam tables in subroutine form (Bliss, D.B.,

Quackenbush, T.R., and Teske, M.E.: " Computational Simulation of High-Speed Steady Homogeneous Two-Phase Flow in Complex Piping Systems," 3 Transactions of the ASME, Volume 104, Pages 272-277, November 1982). The calculations very conservatively assumed all three safety valves and both PORVs were open and flowing in excess of the EPRI test values. The backpressure for the PORVs was not computed since their operation is not affected by backpressure.

QUESTION 4 Stability of the plant valve can only be assessed by comparing the plant inlet pressure drop to the test inlet pressure drop. The test valve most representative of Dresser 31709KA valves at Maine Yankee was the Dresser 31739A. Provide a comparison of the plant-specific pressure drop with the pressure drop in the 31739A valve tests on the inlet configuration most representative of the plant configuration. Provide this information for both valve opening and closing.

RESPONSE

The test valve most representative of the Dresser 31709KA valves at Maine Yankee was the Dresser 31739A. To test the applicability of one of the 31739A runs to Maine Yankee, the " Procedure for Assessment of Applicability of Specific EPRI Safety Valve Tests," Appendix 0 of the "EPRI PHR Safety and Relief Valve Test Program Guide for Application of Valve Test Program Results to Plant-Specific Evaluations" (Revision 2),

MPR Associates, Inc., July 1982, was followed. The four steps include: ,

valve ring settings, discharge piping backpressure, inlet piping pressure j effects, and inlet fluid condition. Our results are: j

a. For the geometrically scaled 31739A middle ring setting of -80 (Run 1008), the 31709KA valve middle ring setting is -68. This completes Step A (Valve Ring Settings).

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. . M AINE YANKEE ATOMIC POWER COMPANY

b. The computed backpressure of 457 psia is less than the run backpressure of 617 psia. This completes Step B (Discharge Piping Backpressure).

c. The pressure drop on valve opening is computed from the formulas given in Appendix B of the EPRI Program Guide to be 238 psid, which is less than the run value for piping "D" of 643 psid. The pressure rise on valve closing is computed from the formulas given in Appendix B of the EPRI Program Guide to be 72 psid, which is less than the run value for piping "D" of 150 psid.

d. The fluid conditions are the same as for Run 1008. This completes Step D (Inlet Fluid Condition). The applicability assessment is complete and run 1008 is determined to be applicable to the plant evaluation. Further confirmation of the behavior of the 31709KA valve was determined by utilizing the COUPLE computer code with the upstream piping in place, and the backpressure effect with all valves open. Stable valve operation was predicted.

OVESTION 6 It was stated the PORV control circuitry at Maine Yankee was designed to IEEE Standards 279-1968, 323-1974, and 344-1975. This information, by itself, is not sufficient to demonstrate qualification of the control circuitry under NUREG-0737. In order to demonstrate that the Maine Yankee control circuitry is qualified, the design qualifications must be compared to the environment the control circuits will be exposed to. Provide documentation to show that the PORV control circuitry has been qualified under 10CFR50.49, or to allow a complete review of the qualification of the control circuitry for the PORV under NUREG-0737, and provide the following: (etc.)

RESPONSE

As discussed in previous submittals, there are two different control circuits that will cause the PORVs to open, thus preventing the mechanical safety valves from lifting. These circuits are used during different modes of operation. The first circuit is used during plant heatup and ,

cooldown to protect against Low Temperature Overpressurization (LTOP) 1 condition. The second circuit provides protection during normal power {

operations. ~

In both circuits, the equipment was designed and purchased to IEEE Standards 279-1968, 323-1974, and 344-1975. However, these control  !

circuits are considered Non-Nuclear Safety (NNS) at Maine Yankee for the j following reasons: l i

a. At Maine Yankee the PORVs are not environmentally qualified as they are not credited for in any accident analysis,

b. If a PORV opens and cannot be closed, the block valves will be used to isolate the event. The block valves are environmentally qualified pursuant to 10 CFR 50.49 and maintained per the Maine Yankee Environmental Qualification Program.

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1 The only portion of the PORV power and control circuitry which is located l in a harsh environment are the pressure transmitters, PORV solenoids and {

associated cable. The circuit that is used during power operations uses a two-out-of-four logic generated in the RPS. Since the RPS transmitters are used for other purposes required for accident mitigation, they fall under the Maine Yankee Environmental Qualification Program. The LTOP circuits use a 1-out-of-1 logic and are the same model transmitter and associated equipment as required for the safety class circuits in the Maine Yankee Environmental Qualification Program. Since this equipment is not required to operate for a design basis accident, it was not included in the program.

00ESTION J Insufficient detail was received on the key parameters used in the STEHAM, NATAIR, and WATSLUG thermal-hydraulic analyses. Provide node diagrams of the thermal-hydraulic models. Provide information on the node spacing, i time step size, and choked flow locations used in the analyses. Discuss the rationale for their selection. Compare the values of these input parameters for the verification calculations requested in Question 7 to the plant-specific analyses. Justify any differences. Since the Dresser 31739A valve passed in excess of 118 percent of rated flow, justify use of 111 percent the ASME rated flow for the safety valves in the thermal-hydraulic analyses or provide the results of thermal-hydraulic and structural analyses which account for the larger flows seen in the tests.

Also, the flow rates used for the 31709KA valve in the thermal-hydraulic analysis, 228,000 lbm/hr, is less than the rated flow listed for the 31079KA valve in the EPRI Guide for ADDlication of Valve Test Proaram Results to Plant-SDecific Evaluations, Revision 2 Appendix B. The flow rate listed was 233,000 lbm/hr. Resolve this difference in light of the fact that MYAPC0 stated steam flows were adjusted to represent 111 percent of rated flow. Compare the rated and test measured flow rates for the Maine Yankee PORVs. If the test flows exceed the rated flow, provide the same information for the PORVs that was requested above for the safety valves. i l

RESPONSE

i A partial response to Question 8 was provided to you in Reference (c).

The remainder of our response is as follows:

-The two tested safety relief valves (SRV) are shown to be geometrically similar to the untested 31709KA valve in Table 1 and Figure 1. Table 1 shows that all radii are geometrically similar, while Figure 1 shows the compatibility between 31709NA and 31739A test runs, and the correspondence of the 31709KA setting of -68 middle ring setting to -80 for the 31739A.

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The flow rates for five EPRI/CE tests were then obtained at several different times and compared against COUPLE code predictions to compute the discharge coefficient shown in Figure 2. The COUPLE predictions are 1 based on an isentropic formulation where mass flow is proportional to the l square root of stagnation pressure. Bounding the discharge coefficient in Figure 2 for the lifts anticipated in the performance of the 31709KA valve gives the mass flow as a function of valve stem position at three percent ]

i accumulation as shown in Figure 3. The peak mass flow anticipated is {

233,000 lbm/hr. 1 He have reviewed our existing analysis for valve stability, forcing functions, and stress analysis assuming a peak mass flow rate of 233,000 lbm/hr. Based upon our review, we have concluded the following:

Valve stability was previously analyzed assuming SRV flow rates in excess of the 233,000 lbm/hr flow rate.

The two percent increase in the pressurizer SRV discharge flow from the j previously used peak of 228,000 lb/hr to the present estimated maximum 5 value of 233,000 lb/hr will have a negligible effect on the discharge l piping and supports. This conclusion is based upon two major points; i

.first, the forces and stresses resulting from the SRV discharge are not I major contributors to the system's high stress points; and second, the seismic accelerations used in the SRV/PORV piping analysis were based on very conservative criteria.

Since the SRV discharge stresses are combined with seismic inertial I stresses, reducing the seismic values to either original FSAR or'the newer 0.18g NUREG-0098 values will easily counterbalance the small increase in SRV discharge flow. ,

1 The PORV tested by EPRI was the same size as that installed at Maine Yankee. The flow rates estimated for the Maine Yankee PORVs were 156,400 lbm/hr which are greater than the EPRI test flows.

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. . TABLE 1 Dresser Valve Comparison .

Characteristic 31739A 31709NA 31709KA .

Weight (lbf-sec 2-ft) 1.6946 2.4586 1.4886 1 1.45 0.88 Spring Constant (lbf/ft) 168,000 238,500 138,228 1 1.42 0.82 r1 (ft) 0.0750 0.09796 0.0639 1 1.31 0.85 r2 (ft) 0.0879 0.11529 0.07525 1 1.31 0.86 r3 -(ft) ,

0.1158 0.15058 0,0975 1 1.30 0.84 r4 (ft) 0.1410 0.18417 0.1201 .

.1 1.31' O.85 rback (ft) 0.1052 0.1375 0.0897 -

1 1.31 0.85 Lower Ring Notches /rev 31 41 30 Threads /in 16 16 16 Middle Ring I Notches /rev 41 49 41

. Threads /in 16 16 16 1

The second line under each characteristic gives values of the characteristic l normalized by the 31739A value. j

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