ML20196K416
| ML20196K416 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 03/04/1988 |
| From: | Eury L CAROLINA POWER & LIGHT CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-85-003, IEB-85-3, NLS-88-037, NLS-88-37, NUDOCS 8803150309 | |
| Download: ML20196K416 (6) | |
Text
ccj y Cp&L Carolina Power & Light Company 9ys % 0g.\\B nee SERIAL: NLS-88-037 Dr. J. Nelson Grace, Regional Administrator United States Nuclear Regulatory Commission 101 Marietta Street, NW Atlanta, GA 30303 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 DOCKET NOS. 50-325 & 50-324/ LICENSE NOS. DPR-71 & DPR-62 IE BULLETIN No. 85-03 "MOTOR-OPERATED VALVE COMMON MODE FAILURES DURING PLANT TRANSIENTS DUE TO IMPROPER SWITCH SETTINGS"
REFERENCES:
(1) CP&L letter from Mr. A. B. Cutter to Dr. J. Nelson Grace (NRC-Region 11) dated October 2,1986, Serial No. NLS-86-300 (2) BWR Owners' Group Report on the Operational Design Basis of Selected Safety-Related Motor-Operated Valves, Dated September 2,1986
Dear Dr. Grace:
e Carolina Power & Light Company's (CP&L) initial response to IE Bulletin No. 85-03 was submitted via Reference 1. The submittal provided the results of CP&L's review, per action (a) of the Bulletin, of the design basis for the operation of the applicable MOVs in the High Pressure Coolant Injection System and the Reactor Core isolation Cooling System. A description of the program and an implementation schedule for completing actions (b) through (d) of the Bulletin were also included.
The October 2,1986 response specified the maximum expected opening and closing differential pressures for those valves identified by Reference 2 as subject to the Bulletin requirements. The differential pressures reported in Reference I were ca:culated using the methodology as described in the BWR Owners' Group Report and contained several very conservative assumptions. These assumptions resulted in the calculated differential pressures exceeding the actual initial design dif ferential pressure for several of the valves. As committed by Reference 1, we are notifying you of revisions to the max. mum expected differential pressures for the subject valves listed on Tables 1 and 2 of Reference 1. The attachments to this submittal provide the data for the applicable valves and the basis for each revision.
As stated in Reference 1, the IE Bulletin 35-03 requirements will be completed and a final report submitted by the end of the BSEP Unit 2 refueling outage. This outage is currently scheduled for completion by April 30,198S.
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- Document Control Desk NLS-88-037 / P:g? 2 Should you have any questions regarding this submittal, please contact
. Mr. Arnold Schmich of my staff at Extension (919) 836-8759.
Yours very truly,
/
M LWE/AWS/ mss (5376AWS)
Attachments cc:
Mr. W. H. Ruland Mr. E. D. Sylvester NRC Document Control Desk L. W. Eury, having been first duly sworn, did o pose and say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of Carolina Power & Light Company.
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ATTACHMENT 1 Design Basis Information Action (a) of the Bulletin requires that CP&L review and document the design basis for the operation of the MOVs in the High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) Systems required to be tested for operational readiness in accordance with 10CFR50.55a(g). This documentation should include the maximum expected differential pressure during both opening and closing of the valve.
The Boiling Water Reactor Owners' Group (BWROG), of which CP&L is a member, developed a program to address action (a) of the Bulletin on a generic basis. Reference 2 provided this generic methodology. Calculations of the maximum expected differential pressures provided in Reference I were based on this BWROG generic methodology and contained several very conservative assumptions. The valves analyzed as requiring calculation of the differential pressures in the BWROG report are listed in Tables 1 and 2 of Reference 1, along with the maximum expected differential pressure in the direction of opening and/or closing. A discussion of the valve function and design basis, assumptions used to determine the maximum expected differential pressure, and differential pressure location (upstream or downstream) were provided in Reference 2.
Due to the excessively conservative assumptions contained in the BWROG generic methodology, the calculated differential pressure for several MOVs were listed as greater than the actual value. For those valves affected, the revised data is provided in. The basis for deviation from the generic methodology is presented below for each af fected MOV.
MOV E41-F012 MOV E41-F012 is the HPCI pump minimum flow-line isolation valve, and discharges to the torus. As discussed in the BWROG report, the safety functions of the valve are to open when other discharge line valves are closed to avoid damage to the pumps, and to close in order to isolate the torus and divert all flow to the reactor vessel.
Since the valve is a globe valve, flow will assist in opening the valve. With the opening torque switch jumpered out, full motor torque can be applied to opening the valve. As stated in the BWROG report, maximum pressure is expected upstream of the valve and therefore assists in opening the valve.
The opening differential pressure calculated using the BWROG methodology was 1374 psid. The conservatism included was that the valve opened at pump deadhead pressure at maximum normal turbine speed. Realistically, the turbine speed is reduced to 3300 rpm prior to closing the injection valve or the full-flow test valve. The valve therefore opens against a 920 p:i pump discharge pressure. Using the BWROG methodology and accounting for this difference, a valve opening differential pressure of 950 psid results.
The closing differential pressure calculated using the BWROG methodology was 1426 psid. The conservatism included was that the valve closed at its required setpoint at maximum normal turbine speed. Realistically, on a normal turbine startup, the turbine has accelerated before the valve reaches the fully closed position (approximately 20 seconds from startup). Line pressure is then only slightly (=40 psi) above reactor pressure. Since this is actual injection pressure, the pressure due to the elevation difference is included. The dif ferential pressure resulting from valve closure, the "water l
(53764s / mss )
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hammer" term, also does not apply. This term accounts for the deceleration of the fluid during closure and uses the pressure wave movement through the pipe. Since this valve l
only closes when another flow path is available, the pressure wave is eliminated by the flow path.- The actual closing differential pressure is therefore 1140 psid.
The existing valve design differential pressure is !!40 psid, and has been tested at that differential pressure prior to shipment to the plant. No further testing is therefore required. Reference 1, Table 1 information has been revised to reflect the new differential pressures and is presented in Attachment 2.
MOV E51-F010 MOV E51-F010 is the RCIC pump Condensate Storage Tank (CST) suction valve. As discussed in the BWROG report, the safety function of the valve is to close when the RCIC suction is transferred to the torus from the CST.
The cpening dif ferential pressure calculated using the BWROG methodology was 40 psid. The conservatism included was in the calculation of the "water hammer" term.
The upstream piping length used in the calculation was the length from the valve to the CST. The 6-inch RCIC suction pipe actually taps off the 16-inch common supply header only 27-feet upstream of the valve. Due to the large diameter change (and thus velocity change), this should be used as the suction source, not the CST. Using the BWROG methodelogy with this difference results in a valve closing differential pressure of 30 psid.
The existing valve design differential pressure is 30 psid and has been tested at that differential pressure prior to shipment to the plant. No further testing is therefore required. Reference 1, Table 2 information has been revised to reflect the new differential pressures and is presented in Attachment 2.
MOV E51-F013 The E51-F013 is the RCIC pump injection valve. As discussed in the BWROG report, the safety functions of this valve are to open to provide reactor inventory makeup and to close to provide primary containment isolation.
The opening dif ferential pressure calculated using the BWROG methodology was 1234 psid. The conservatism included was that the valve opened at pump deadhead pressure at maximt.a normal turbine speed. Ret.listically, the valve starts to open once the stean admission valve is 4% open (approximately 2 seconds from initiation). The valve therefore only sees the initial startup pressure peak (this peak is only momentary),
not pump deadhead pressure. Using an initial peak of 1200 psi (startup traces reflect approximately 1100 psi) the B4 MOG methodology with this difference results in a valve opening differential pressure of 1140 psid.
The closing differential pressure calculated using the BWROG methodology was 1367 psid. The conservatism included was that the valve closed at pump deadhead pressure at maximum normal turbine speed. Realistically, the turbine speed is reduced to 2300 rpm prior to closing the valve. The valve therefore closes against a 340 psi pump discharge pressure. Using the same methodology, with this difference, results in a valve closing differential pressure of 440 psid.
(5376AWS/ mss)
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E The existing valve design dif ferential pressure is 1140 psid, and has been tested at that differential pressure prior to shipment to the plant. No further testing is therefore required. Reference 1, Table 2 information has been revised to reflect the new differential pressure and is presented in Attachment 2.
MOV E51-F019 The E51-F019 is the RCIC pump minimum flow-line isolation valve and discharges to the torus. As discussed in the BWROG report, the safety functions of the valve are to open when other discharge-line valves are closed to avoid damage to the pumps, and to close to isolate the torus and divert all flow to the reactor vessel.
Since the valve is a globe valve, flow will assist in opening the valve. With the opening torque switch jumpered out, full motor torque can be applied to opening the valve. As stated in the BWROG report, maximum pressure is expected upstream of the valve and therefore assists in opening the valve.
The opening differential pressure calculated using the BWROG methodology was -
1324 psid. The conservatism included was that the valve opened at pump deadhead 4
pressure at maximum normal turbine speed. Realistically, the turbine speed is reduced to 2300 rpm prior to closing the injection valve or the full-flow test valve. The valve therefore opens against a 340 psi pump discharge pressure. If the initial startup pressure peak of 1100 psi is used instead as the opemng pressure (though this peak is only momentary), the valve opening differential pressure becomes 1124 psid.
The closing differential pressure calculated using the BWROG methodology was 1362 psid. The conservatism included was that the valve closed at its required setpoint at maximum normal turbine speed. Realistically, on a normal turbine startup, the turbine has accelerated before the valve reaches the fully closed position. Line pressure is then only slightly (=110 psi) above reactor pressure. Using the same methodology with this difference results in a valve closing differential pressure of 1280 psid.
The existing valve design differential pressure is 1330 psid, and has been tested at that differential pressure prior to shipment to the plant. No further testing is therefore required. Reference 1, Table 2 information has been revised to reflet.t the new differential pressure and is presented in Attachment 2.
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(5376AWs/ mss)
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ATTACHMENT 2 MOV DESIGN DATA (Revisions to October 2,1986 submittal)
Maximum Expected CP&L Differential Pressure Valve Valve Open Close System Tag No.
Function (psid)
Comments HPCI:
E41-F012 Minimum Flow Bypass 950 1140 See Note A, B, and C RCIC:
E51-F010 CST Suction N/A 30 See Note B and C E51-F013 Injection 1140 440 See Note A, B, and C E51-F019 Minimum Flow Bypass 1124 1280 See Note A, B, and C Notes:
A)
Opening torque switch is jumpered out.
B)
Closing limit switch is jumpered out.
C)
Valve previously tested against calculated differential pressure and requires no further testing.
w (5376AWS/ mss) 1