ML20197J664
| ML20197J664 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/10/1998 |
| From: | Sorensen J NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9812150178 | |
| Download: ML20197J664 (4) | |
Text
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orthern states P4wer Company Prairie Island Nuclear Generating Pknt 1717 Wakonade Dr. E.
Welch, MN 55089 December 10,1998 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos.50-282 License Nos. DPR-42 50-306 DPR-60 Technical Specification Interpretation for Applicability c,f Quadrant Power Tilt Limits Northern States Power Company (NSP) hereby requests an interpretation of the Prairie Island Nuclear Generating Plant (PINGP) Technical Specifications w!th respect to the I
applicability of the Quadrant Power Tilt Ratio (QPTR) Limits of Technical Specificat;cn TS.S.10.C. Per our December 4,1998, telephone discussion with the NRC, NSP proposes that TS.3.10.C be interpreted such that, at power levels less than 50% RTP, the OPTR limits of this specification are not applicable.
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Justification for this Interpretation PINGP Technical Specification TS.3.10.C has four sub-paragraphs: TS.3.10.C.1 through TS.3.10.C.4.
TS.3.10.C.1 states:
"Except for PHYSICS TESTS, if the QUADRANT POWER TILT RATIO exceeds 1.02 but is less than 1.07, the rod position indication shall be monitored and logged once each shift to verify rod position within each bank assignment and, within two hours, one of the following steps shall be taken:
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USNRC NORTHERN STATES POWER COMPANY December 10,1998 Pagp 2 a'. Correct the QUADRANT POWER TILT RATIO to less than 1.02.
- b. Restrict core power level so as not to exceed RATED THERMAL POWER less 2% for every 0.01 that the QUADRANT POWER TIL1 RATIO exceeds 1.0."
At its most restrictive, TS.3.10.C.1 limits power to 86% if QPTR is 1.07. Thus, TS.3.10.C.1 is not applicable at less than 50% power.
TS.3.10.C.2 states:
"If the QUADRANT POWER TILT RATIO exceeds 1.02 but is less than 1.07 for a sustained period of more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, or if such a tilt recurs intermittently, the reactor shall be brought to the HOT SHUTDOWN condition.
Subsequent operation below 50% of rating, for testing, shall be permitted."
i TS.3.10.C.3 states:
"Except for PHYSICS TESTS if the QUADRANT POWER TILT RATIO exceeds 1.07, the reactor shall be brought to the HOT SHUTDOWN condition. Subsequent operation below 50% of rating, for testing, shall be permitted."
i Both TS.3.10.C.2 and TS.3.10.C.3 allow " subsequent" operation of below 50% RTP i
regardless of QPTR (for testing). Thus, the QPTR limits of these specifications do not apply at less than 50% power.
TS.3.10.C.4 states:
"If the core is operating above 85% power with one excore nuclear channel inoperable, then the core quadrant power balance shall be determined daily and after a 10% power change using either 2 movable detectors or 4 core thermocouples per quadrant, per Specification 3.11.
TS.3.10.C.4 explicitly states it applies only when power exceeds 85% and, thus, does not apply when power is less than 50% RTP.
The basis for TS.3.10.0 notes:
" Operational experience shows that normal QUADRANT POWER TILT RATIOS are less than 1.01. Thus, sufficient time is available to recognize the presence of a tilt and correct the cause before a severe tilt could build up.
During start-up and power escalation, however, a large tilt could be initiated.
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USNRC NORTHERN STATES POWER COMPANY DecGmber 10,1998 PagG 3
. Therefore, the Technical Specification has been written so as to prevent l
escalation above 50 percent THERMAL POWER if a large tilt is present."
Therefore, it appears that none of the OPTR limits of TS.3.10.C should be applied at less than 50% RTP. This would be consistent with the Technical Specifications of plants similar to the PINGP (i.e., Ginna and Point Beach). Ginna Technical Specification 3.2.4 (Ginna has converted to Standard Technical Specifications) has Applicability of" MODE 1 with THERMAL POWER > 50% RTP." Point Beach Technical Specification 15.3.10.3.a also limits applicability to "During power operation with thermal power greater than 50 percent of rated thermal power...."
Thus, NSP believes the intent has always been that quadrant power tilt limits in the PINGP Technical Specifications were not applicable at power levels less than 50%
RTP. Currently, NSP expects that the proposed quadrant tilt limits in our pending improved standard technical specification submittal will not be applicable at lower than 50% RTP.
Safety Significance of this Interpretation QPTR limits ensure, in part, that peaking factors are maintained within the assumptions of the safety analysis, such that power density at any point in the core does not violate the fuel design criteria. At power levels less than 50%, peaking factor limits would not be challenged unless an exceedingly large QPTR existed.
The bases for Section 3.2.4 of Standard Technical Specifications for Westinghouse Plants (NUREG-1431, Vol. 2, Rev.1) notes:
" Applicability in MODE 1 s 50% RTP and in other MODES is not required because there is either insufficient stored energy in the fuel or insufficient energy being transferred to the reactor coolant to require implementation of a OPTR limit on the distribution of core power. The OPTR limit in these conditions is, therefore, not important. Note that the F"an and Fo(Z) LCOs still apply, but allow progressively higher peaking factors at 50% RTP or lower."
The assertion that QPTR limits are not important when thermal power is less than 50%
RTP is reflected in the fact that the PINGP's safety related QPTR alarms are automatically disabled when power is less than 50%. Note that the non-safety related QPTR alarms at the PINGP are not automatically disabled below 50% RTP.
NSP believes that the health and safety of the public will still be protected if we interpret the quadrant power tilt limits in TS.3.10.C to not be applicable if power is less than 50%
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USNRC NORTHERN STATES POWER COMPANY
- December 10,1998 l
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RTP. NSP believes it will continue to operate the PINGP in a safe manner and in l
compliance with Technical Specifications with this interpretation.
l Your timely response to this request for interpretation would be appreciated, since l
Prairie Island Unit 2 is currently in a refueling outage and start-up operations will likely result in QPTR greater than 1.02 at power levels less than 50%. Unit 2 could be in this condition (QPTR greater than 1.02 at less than 50% power) for longer than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, l
particularly, since we will be performing tests on the new low pressure turbine rotors.
Thus, we foresee the need to invoke this interpretation in the near future.
In this letter we have made no new NRC commitments. Please contact Jeff Kivi (651-388-1121) if you have any questions related to this letter.
r l P. Sorensen Plant Manager i
Prairie Island Nuclear Generating Plant c: Regional Administrator-Region lil, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg i
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