ML20092M185
| ML20092M185 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 09/20/1995 |
| From: | Wadley M NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9509290097 | |
| Download: ML20092M185 (4) | |
Text
9 Northern states Power Company 1717 Wakonade Dr. E.
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Welch. MN 55089 Telephone 612-3881121 September 20,1995 10 CFR Part 50 Section 50.90 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Noa. DPR-42 50-306 DPR-60 Supplement to License Amendment Request Dated January 10,1995 Post Accident Monitoring Technical Specifications Conformance to Standard Technical Specifications l
Pursuant to discussions with your staff regarding the subject license amendment request, Northern States Power Company pro / ides the following information on the relationship between the reactor coolant system cold leg temperature (Teae) and the steam generator temperature derived from steam generator pressure. This
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discussion shows that the use of steam generator temperature (derived from steam generator pressure), in lieu of measured reactor coolant system Teou, is an acceptable alternative indication for controlling cooldown rate and placing the over-i pressure protection system (OPPS) in service during accident situations.
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Because heat is transferred from the reactor coolant system to the steam generator, steam generator temperature will be lower than T.S and the difference in temperature will be proportional to the heat removed. At 100% power, the steam generator temperature will be approximately 20 F lower than Teow. Following a l
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'S ptImber 20,1995 Page 2 of 4 reactor trip, the decay heat is only about 7% of rated power, and the temperature differencs between the steam generator and the reactor coolant system cold leg would only be about 1 to 2 F. This relationship exists whether there is forced or natural circulation in the reactor coolant system. Although for natural circulation, the temperature in a steam generator may be higher than the associated T w if that
-l steam generator is not being steamed, i.e., the reactor coolant system is not being cooled by that steam generator.
j in a post-accident situation, the T w indication is utilized by operations personnel to monitor and control the reactor coolant system cooldown rate and to determine when the over-pressure protection system should be placed in service. In both cases, using the steam generator temperature derived from steam generator pressure would be conservative to using the actual reactor coolant system T w indication.
Normally, the cooldown rate is developed by plotting the reactor coolant system average temperature (T ) over time. Because steam generator temperature is lower than T w, reactor coolant system T determined using steam generator temperature will be lower than the T., determined using the actual T w value.
Therefore, the cooldown rate calculated using the initial actual (pre-accident) reactor coolant system T and e post-accident T determined using steam i
generator temperature, would be conservatively higher than the actual cooldown i
rate. Thus, using the cooldown rate calculated from steam generator temperature to control the reactor coolant system post-accident cooldown would result in a lower actual cooldown rate. The lower actual cooidown rate would impart less stress on j
the reactor vessel.
With respect to placing the over-pressure protection system in service, reactor coolant system T determined using the steam generator temperature will be lower than the actual T... The use of the steam generator temperature derived T to determine when the over-pressure protection system should be placed in service will result in the over-pressure protection system being conservatively placed in l
service at a higher actual reactor coolant system temperature, further from the j
reference transition temperature of the reactor vessel.
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Therefore, based on the discussion above, steam generator temperature does correlate to reactor coolant system T w, and for the purpose of monitoring of reactor l
coolant system cooldown rate and placirig the over-pressure protection system in l
service, its use is conservative.
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The information provided by this letter does not modify the subject license l
amendment request, therefore the Safety Evaluation, Significant Hazards s
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'S*pt::mber 20,1995 Page 3 of 4 Determination and Environmental Assessment originally presented in the January 10r1995 submittal continue to bound the proposed amendments.
Northern States Powei Company will establish standing procedural guidance for the plant operators directing them to correlate steam generator tempereture to Tm in the event one or more Tm instrument channels is unavailable.
If you have any questions related to this information in support of the subject license amendment request, please contact myself or Dale Vincent at 612-388-6758 X4107.
[Yl)0YbW M. D. Wadley
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Plant Manager, V
l Prairie Island Nuclear Generating Plant i
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Regional Administrator-lil, NRC l
NRR Project Manager, NRC Senior Resident inspector, NRC i
i State of Minnesota Attn: Kris Sanda J E Silberg i
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USNRC t,
'Srptember 20,1995 Page 4 of 4 UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET NO. 50-282 50-306 REQUEST FOR AMENDMENT TO OPERATING LICENSES DPR-42 & DPR-60 LICENSE AMENDMENT REQUEST DATED January 10,1995 Northern States Power Company, a Minnesota corporation, provides this supplemental information in support of its license amendment request dated January 10,1995. This letter contains no restricted or other defense information.
NORTHERN STATES POWER COMPANY
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By M. D. Wadley Plant Manager Prairie Island Nuclear Generating Plant On this/d ay of
, If before me a notary public in and for said County, personally appedred M. D. Wadley, Plant Manager, Prairie Island Nuclear 4
Generating Plant, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not interposed for delay.
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j MARCIA K. LaCORE i
NOTARY PUBUC41NNE90TA HENNEPN COUNTY i.'
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