ML20072T912
| ML20072T912 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 09/07/1994 |
| From: | Mcmeekin T DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9409160033 | |
| Download: ML20072T912 (8) | |
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DuneIbwer Company (704)875-4000 lJ McGuire Nuclear Station
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12700 Hagers Ferry Road
- HunterscWe. NC28078-8985 i
DUKEPOWER September 7, 1994 i
U.
S. Nuclear Regulatory Commission l
Attention: Document Control Desk Washington, D.
C.
20555 1
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Subject:
McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 Request for Exemption - ASME Code. Case N-514 i
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Dear Sir:
l By letter dated June 28, 1994, and as supplemented by letter dated August 18, 1994, an exemption from certain requirements of 10 CFR 50.60, " Acceptance criteria for fracture prevention measures for light water nuclear. power i
reactors for normal operation", was submitted for McGuire Nuclear Station.
This exemption was requested to allow the application of American Society of Mechanical Engineers (ASME) Code Case N-514, " Low Temperature Overpresssure Protection", for determining the setpoint for the Low f
Temperature Overpressure Protection (LTOP) system for McGuire Units 1 and 2.
In support of the NRC staff review of the exemption request please find attached clarification regarding the information previously provided by letters dated June 28, 1994 and j
August 18, 1994.
1 As stated in the June 28, 1994 letter, NRC approval of this exemption is requested prior to the establishment of low temperature conditions for the start of Unit 1 cycle 10.
The anticipated date for establishing low temperature conditions is the week of October 3, 1994.
Please contact Paul Guill at (704) 875-4002 if there are any questions regarding this submittal.
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Very truly yours, fila
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C. McMeehin T.
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ADOCK 05000369 PDR
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S. Nuclear Regulatory Commission September 7, 1994 page 2 xc:
Mr.
S.
D.
Ebneter Regional Administrator, Region II U.
S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. George F. Maxwell Senior NRC Resident Inspector, McGuire McGuire Nuclear Station Mr. Victor Nerses, Project Manager Office of Nuclear Reactor Regulation U.
S. Nuclear Regulatory Commission One White Flint North, Mail Stop.9H3 Washington, D.C.
20555 i
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S. Nuclear Regulatory Commission September 7, 1994 page.3 i
bec: With Attachment J. E.
Snyder j
J. M. Washam J.
F. Nolin J.
D. Gilreath M.
D. Rains i
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D.
Curtis l
G. A. Copp l
P.
F. Guill l
ELL (EC050) l File: 801.01 i
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c ATTACHMENT DUKE POWER COMPANY MCGUIRE NUCLEAR STATION
INTRODUCTION l
The exemption requested by letter dated June 28, 1994, and as supplemented by letter dated August 18, 1994 would allow the application of American Society of Mechanical Engineers
(. SME)
A Code Case N-514, " Low Temperature Overpressure Protection", in determining the acceptable Low Temperature Overpressure Protection (LTOP) system setpoint for McGuire Nuclear Station, Units 1 and 2.
The following discussion provides clarification in regards to the information provided within the August 18, 1994 letter.
DISCUSSION OF APPENDIX G LIMITS As discussed within the August 18, 1994 letter, the worst case peak pressure is 571 psig.
The August 18, 1994 letter, provided a discussion regarding the determination of the peak pressure j
resulting from the worst case overpressure event at low
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temperatures.
Technical Specification (TS) Figures 3.4-2, 3.4-3, 3.4-4 and 3.4-5 provide the reactor coolant system heatup and cooldown curves for McGuire Units 1 and 2.
These pressure / temperature (P/T) limits were developed in accordance with the regulatory requirements and guidance of Appendices G and H to 10 CFR 50; l
Regulatory Guide 1.99, revision 2; Standard Review Plan (SRP)
Section 5.3.2 and Generic Letter 88-11.
The current P/T limits are valid for 10 effective full power years (EFPY) and were approved by the NRC in a letter dated November 15, 1990.
Both sets of Technical Specification P/T curves include margins for instrument uncertainty (10 F and 60 psig).
As noted in the discussion regarding the determination of the peak pressure resulting from an LTOP event, a margin of 70 psig and 12 F is included in the setpoint calculation for instrument uncertainties.
As such, the margin provided for instrument uncertainty (10 F and 60 psig) within the TS P/T curves, needs to be removed.
Accordingly, Table 1 provides the ASME Section XI Appending G limits after the assumed margins for instrument error are removed from the TS heatup and cooldown curves.
The data provided in Table 1 is limited to a range of 85 F to 160 F.
This temperature range is believed to be sufficient to illustrate the need for ASME Code Case N-514.
As can be seen from the data provided in Table 1, the ASME Section XI Appendix G limits would be exceeded if an LTOP ovent occurred during normal heatup or cooldown operations and the temperature of the reactor coolant system (RCS) is equal to or less than 140 F.
Further, the Appendix G limits would also be exceeded if an LTOP event occurred during steady state, isothermal conditions, and the RCS temperature was equal to or less than 125 F.
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From another perspective, following a refueling outage significant portions of the RCS will tend to approach the lower containment-ambient temperature, which could be 100 F or less.
The Appendix G limit for a heatup rate of 60 F/hr is 514.19 psig (see Table 1).
To ensure this limit is not exceeded, the PORV setpoint would have to be set at 328.49 psig, which takes into account the following factors: 1) elevation corrections; 2) DP corrections due to RCS flow; 3) instrumentation uncertainty; and
- 4) PORV accumulation.
The August 18, 1994 letter provides a discussion ~of these factors.
This would only provide a margin of 3.49 psig above the minimum required pressure for the operation of a Reactor Coolant pump.
This would be insufficient margin in preventing the inadvertent opening of a PORV.
TABLE 1 1
DATA POINTS FOR HEATUP AND COOLDOWN CURVES (Without Margins for-Instrumentation Error)
INDICATED STEADY STATE:
20*F/HR COOLDoWN 60'F/ER TENPERATURE (*F)
INDICATED RATE INDICATED HEATUP RATE PRESSURE (PSIG)
PRESSURE (PSIG)
INDICATED PRESSURE (PSIG) i 85 519.27 477.80 514.19
^
90 524.20 482.88 514.19 95 529.51 488.38 514.19 100 535.21 494.19 514.19 105 541.23 500.55 514.54 110 547.82 507.44 516.81 115 554.91 514.86 521.00 120 562.53 522.82 526.75 125 570.72 531.43 534.12 130 579.52 540.57 542.78 135 588.87 550.55 553.01 140 599.04 561.27 564.58 l
145 609.99 572.85 577.58 150 621.75 585.16 591.80 155 634.25 598.57 607.62 160 647.85 612.98 624.88 Note la The data points are 10CFR50 Appendix G limits for McGuire Unit 1, without margins for instrument uncertainties. Y 4-4, Unit 1 cooldown This represents the 0 F/hr curve of TS Figure Note 2:
curve (without instrument error) i PAGE 2 l
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'l IMPACT OF ASME CODE CASE N-514
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ASME Code Case N-514 allows setting the LTOP actuation setpoint such that the ASME Section XI, Appendix G limits are not exceeded i
by more than 10%.
Using Code Case N-514, the revised Appendix G limit for steady state, isothermal conditions would be 571.2 psig (519.27 1.1 = 571.2).
For a cooldown rate of 20 F/hr, the Appendix G limit would be 525.58 psig.
The Appendix G limit for i
a heatup rate of 60 F/hr would be 565.61 psig.
To ensure that the ASME Section XI Appendix G limits will not be exceeded during all modes of operation (steady state, heatup and cooldown), restrictions regarding the operation of the Reactor j
Coolant pumps are imposed.
This affects the value associated i
with the DP Corrections due to RCS Flow, in that if no Reactor Coolant pumps.are operating, the pressure difference across the reactor vessel due to flow would be virtually zero.
For l
conservatism, a 0.3 psig value for no Reactor Coolant pumps operating is assumed.
As a result, the peak pressure resulting from the worst case LTOP event would be 525.3 psig.
The resulting peak pressure from the LTOP event without Reactor i
Coolant Pumps running will not exceed the Appendix G allowable l
pressure for a cooldown rate of 20. F/hr (the limiting case i
discussed above).
In summary, the application of the provisions of Code Case N-514, in conjunction with restrictions on heatup. rates, cooldown rates, i
I and the number of Reactor Coolant pumps-operating at the lower temperature region, will ensure that the Appendix G allowable pressure will not be exceeded during an overpressure event at low-i temperature conditions.
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CLARIFICATION OF TABLES WITHIN AUGUST 18, 1994 LETTER The attachment to the August 18, 1994 letter provided two tables,
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one on page 3 and the other on page 4.
These two tables are j
reproduced within this document for consistency purposes (see l
Tables 2 and 3).
Additional information regarding the data l
provided by these tables is discussed below.
I TM2 2 TABLE LOCATED ON PAGE 3 OF THE AUGUST 18, 1994 LETTER CONDITION MINIMUM ACTUAL MINIMUM INDICTED TEMPERATURE TEMPERATURE Steady State 125 F 137 F 5 F/ hour cooldown 130 F 142 F l
10 F/ hour heatup 128 DF 140 F
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j TABLE 3 TABLE LOCATED ON PAGE 4 OF THE AUGUST 18, 1994 LETTER CONDITIONS MINIMUM ACTUAL MINIMUM INDICATED TEMPERATURE TEMPERATURE Steady State 85 F 97 F 10 F/ hour cooldown 102 F 114 F 30 F/ hour heatup 100 #F 112 0F For both tables, the ' minimum actual temperature' is the RCS temperature without instrument error.
This temperature is determined by comparison of the calculated peak pressure [571 psig for Table 2, or 519 psig {571/1.1=519) for Table 3] with the Appendix G limits (Table 1).
The minimum indicated temperature is the result of adding margin for instrument uncertainty (12 F) to the minimum actual temperature. The intent of the tables is to illustrate the minimum RCS temperature required to operate a Reactor Coolant pump for a given mode of operation (steady state, heatup and cooldown).
The difference between Table 2 and Table 3 is that Table 2 is based on the current Appendix G limits for Unit 1 and Table 3 is based on the allowable pressures as i
determined by the provisions of Code Case N-514.
Normally, to start a Reactor Coolant pump, the RCS pressure needs to be greater than 325 psig and the temperature of the RCS would be of secondary concern.
As shown in Table 2, the RCS would have to be heated to a temperature of greater than 140 F (displayed by the instrumentation) before a Reactor Coolant pump can be started.
Heating the RCS without using the Reactor Coolant Pumps will introduce non-uniformity in the RCS temperature, and' requires larger operating ranges to control the temperature and pressure transient created by starting a Reactor Coolant Pump.
j As can be seen in Table 3, the use of Code Case N-514 would significantly improve the situation.
By including a restriction on RCS temperature when operating Reactor Coolant pumps, the allowable P/T limits will not be exceeded in the event of an overpressure transient. This has resulted in the need to operate the station in a risk significant configuration in order to re-start following a cold shutdown or l
refueling operation.
The application of code case reduces the l
' minimum RCS temperature needed to operate a Reactor Coolant pump l
such that the station does not have to be operated in a risk I
significant configuration A discussion of the risk significant i
configuration utilized is provided by the August 18, 1994 letter.
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