ML20042D259
| ML20042D259 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 12/22/1989 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C311-89-2143, TAC-75103, NUDOCS 9001080161 | |
| Download: ML20042D259 (5) | |
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GPU Nuclear Corporation
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One Upper Pond Road u
Parsippany, New Jersey 07054 201 316-7000 TELEX 136 482 Writer's Direct Dial Number:
Decmber 22, 1989 C311-89-2143 U. S. Nuclear Regulatory Commission Attn Document Centrol Desk Washington, DC 20555 Gentlemen:
Three Nile Island Nuclear Generating Station, Unit 1 (THI-1)
Operating Licenso No. DPR-50 Docket No. 50-289 Response to NRC Request For Additional Information -
Technical Specification Change Request No. 196 (TAC No. 75103)
This letter provides the GPUN response to NRC's Request for Additional Information, dated November 1, 1989, concerning Technical Specification Change Request No. 196.
The attachment provides a responce to each question.
If additional information is required, please contact us.
Sincerely, 1
1 Attachment Vice President and Director, THI-1 cc J. Stoir., USNRC R. Hernan, USNRC W.
T. Russell, USNRC, Region I F. Young, USNRC TMI-1 i
GPU Nuclear Corporation is a subsidiary of General Pubhc Utikties Corporation
t C311-89-2143 Sheet 1 of 4 ATTACHMENT l
NRC Ouestion 1 One of the proposed changes would increase the positive limit of the modgratortemperaturecoefficient (MTC) from +0.5 x 10~4 to +0.9 x 10' delta k/k/degf. Although the existing TSAR Chapter 14 accident analysis acceptance criteria and margins of safety would still be maintained with the proposed MTC increase, the staff has previously expressed its concerns regarding trends in current reload designs that may lead to initial HTCs that may be less conservative than were assumed for ATWS analyses.
In view of this, discuss the impact of the proposed MTC increase on the B&W/BWOG generic ATWS assumptions.
P CPUN Reerionsg The MTC values of +0.5 x 10'4 and +0.9 x 10'4 delta k/k/degf stated in the NRC question are Technical Specification limits for power levels between 0 and 95 % Full Power (FP). Above 95 %FP, the HTC is required tobenegativebyTechnicalSpecifigations. Since it is not possible for the MTC to drop from +0.5 x 10' or +0.9 x 10'4 delta k/k/degf to less than zero between 94.9 %FP and 95.1 %FP, the reload evaluation and Physics Test Program verify compliance with the +0.5 x 10'4 or
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+0.9 x 10~4 delta k/k/degf limit by comparing it against a calculated l
and measured hot zero power (HZP) HTC.
The ATWS analysis defined the l
accident that would maximize the ATWS consequences as a loss of main feedwater flow (LOMFW) from 100 %FP.
The MTC values used in these analyses were hot full power (HFP) values and are not directly l
comparable to the +0.5 x 10' or +0.9 x 10-4 delta k/k/degf HZP limit.
The GPUN submittal to the NRC with regard to an ATWS mitigation (C311-89-2058, dated October 4,1989)is supported by THI-1 specific ATWS analyses performed by GPUN. A MTC value of -0.849 x 10~4 delta k/k/degf is used in the GPUN ATWS analyses and ensures that the hot full power (HFP) HTC will be more negative than this value for 95% of an 18 monghfuelcycle.
This value is more positive than the value of -1.05 x 10' delta k/k/degt used by B&W in their generic analyses.
CPUNhasperformedascopingLOMFWATWSanagysisusingaMTCof-0.605x 10'4 delta k/k/degf. This MTC is 0.4 x 10" delta k/k/degf more positive than the BWFC generic ATWS analysis.
The results of this scoping analysis (4768 psi) showed that the peak RCS pressure was 935 i
psi higher than the B&W generic analysis (3833 psia). The use of a constant MTC value is very conservative and unrealistic because the MTC will become increasingly more negative ao the pressure and temperature increase due to the ATWS.
The effect of the increasingly more negative MTC as pressure and temperature increase will more than offset the more positive initial MTC caused by increasing the cycle length.
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1 C311-89-2143 Sheet 2 of 4 l
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t AogcondscopingLOMFWATWSanalysisstartingwithaMTCof-0.605x 10~
delta k/k/degf and allowing the MTC to change as a function of the RCS pressure and temperature was performed. The results of this scoping analysis (3753 psi) showed that the peak RCS pressure was 80 psi lower than the B&W generic analysis (3833 psia) and 483 pai lower than the results of the ATWS analysis (4236 psia) submitted by CPUN for a constant HTC.
Thus it is concluded that the GPUN ATWS analysis which supports our ATWS submittal to the NRC will remain conservative with respect to an ATWS response for longer cycles.
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I 2-c311-89-2143 Sheet 3 of 4 NRC Ouestion 2 Although thermal-hydraulic stability has not been considered a. serious problem ~in PWRs in the past, a more positive MTc is in the direction of instabilities and may become a concern. Discuss any adverse impact of the larger positive MTc on the hydraulic stability of the TMI-1 core.
GPUN Response As stated in the' response to Question #1 the +0.5 x 10~4 or +0.9 x 10'4 delta k/k/degf limit is a hot zero power (HZP) value. The hydraulic stability of the reactor is normally evalue.ted at the hot full power condition (HFP).
TMI-1 Technical Specifications continue to require a negative MTc at power levels greater tnan 95 %FP.
The two conditions that have the largest effect on the hydraulic stability of the reactor are the use of a closed-channel configuration and a highly voided coolant (BWR parameters).
Since THI-1 is a PWR with an open
-channel configuration and virtually.a void free coolant no adverse impact is expected on the hydraulic stability of the reactor due to a slightly larger positive MTc.
The hydra *alic stability of the TMI-1 reactor is not expected to be differcnt from the other B&W reactors at crystal River 3, oconee 1, 2, and 3, nancho Seco and Davis Besse which are already licensed for an MTc limit
't +0.9 x 10~4, delta k/k/degf from 0 to 95 %FP.
c311-89/4
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C311-89-2143
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NRC Ouestion 3 How does the larger positive MTC affect the neutronic stability of the core?
GPUN Response As stated in the response to Question #1 the +0.5 x 10~4 or +0.9 u 10~4 delta k/k/degf limit is a hot zero power (HZP) value. The neutronic stability of the reactor is normally evaluated at the hot full power condition (HFP).
TMI-1 Technical Specifications continue to require a negative MTC at power levels greater than 95 %FP.
The neutronic stability of the THI-1 reactor is not expected to significantly change due to the slightly positive MTCs seen at low power levels. The response of the control room personnel to a temperature change with respect to both the actions taken and the time to take those actions is not expected to significantly change. Therefore, there is no adverse impact expected on the neutronic stability of the reactor due to a slightly larger positive MTC.
The neutronic stability of the THI-1 reactor is not expected to be different:from the other B&W reactors at Crystal River 3, Oconee 1, 2, and 3, Rancho seco and Davis Besse which are already licensed for an MTC limit of +0.9 x 10~4, delta k/k/degf from 0 to 95 %FP.
C311-89/5 i.
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