ML20198J518

Forwards TS Interpretation for Applicability of Quadrant Power Tilt Ratio Limits

ML20198J518
Person / Time
Site:	Prairie Island
Issue date:	12/21/1998
From:	Kim T NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
TAC-MA4363, TAC-MA4364, NUDOCS 9812300205
Download: ML20198J518 (5)

Text

. _. _ _. _ _. _. _ _ _ _ _ - _ _.

gg December 21, 1998 L

l Mr. Roger O. Anderson, Director Nuclear Energy Engineering Northern States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401

SUBJECT:

TECHNICAL SPECIFICATION INTERPRETATION FOR APPLICABILITY OF QUADRANT POWER TILT RATIO LIMITS FOR PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 (TAC NOS. MA4363 AND MA4364)

Dear Mr. Anderson:

i In a letter dated December 10,1998, as supplemented on December 17,1998, Northern States Power Company submitted a request for an interpretation of the Prairie Island Nuclear Generating Plant technical specifications (TS) with respect to the applicability of the quadrant power tilt ratio (QPTR) limits specified in TS.3.10.C at power levels less than 50 percent of the rated reactor thermal power. Enclosed is the staff's evaluation. Based on its evaluation, the staff concluded that TS.3.10.C is not applicable at power levels less than 50 percent of the rated reactor thermal power.

i Sincerely, Original signed by:

Tae Kim, Senior Project Manager Project Directorate lil-1 Division of Reactor Projects - lil/IV Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306

Enclosure:

Staff Evaluation cc w/ encl: See next page I[

DISTRIBUTION:

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DOCUMENT NAME: G:\\WPDOCS\\ PRAIRIE \\TSl4363.WPD To receive a copy of this document, indicate in the box C= Copy w/o attachment / enclosure E= Copy with attachment / enclosure N

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' Mr. Roger O. Anderson, Director Prairie Island Nuclear Generating Northern States Power Company -

Plant cc:

J.' E. Silberg, Esquire Site Licensing

' Shaw, Pittman, Potts and Trowbridge Prairie Island Nuclear Generating

^:

2300 N Street, N. W.

Plant Washington DC 20037 Northern States Power Company, 1717 Wakonade Drive East Plant Manager Welch, Minnesota 55089 Prairie Island Nuclear Generating Plant Tribal Council i

Northem States Power Company

_ Prairie Island Indian Community 1717 Wakonade Drive East ATTN: Environmental Department l

Welch, Minnesota 55089 5636 Sturgeon Lake Road Welch, Minnesota 55089 Adonis A. Nebiett L

Assistant Attorney General i

Office of the Attorney General 455 Minnesota Street Suite 900 St. Paul, Minnesota 55101-2127.

U.S. Nuclear Regulatory Commission Resident inspector's Office 1719 Wakonade Drive East Welch, Minnesota 55089-9642 i

i l

Regional Administrator, Region lli U.S. Nuclear Regulatory Commission 801 Warrenville Roact j

Lisle, Illinois 60532-4351 l

Mr. Stephen Bloom, Administrator L

Goodhue County Courthousa Box 408 l

. Red Wing, Minnesota 55066-0408 e

Kris Sanda, Commissioner l

Department of Public Service i

121 Seventh Place East Suite 200 St. Paul, Minnesota 55101-2145 June 1998

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UNITED STATES i

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NUCLEAR REGULATORY COMMISSION lY e

WASHINGTON, D.C. 2006H001 Q**CR* /

l TECHNICAL SPECIFICATION INTERPRETATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i

RELATED TO TECHNICAL SPECIFICATION TS 3.10.C AS APPENDED l

TO FACILITY OPERATING LICENSE NOS. DPR-42 AND DPR-60 NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT. UNITS 1 AND 2 DOCKET NOS. 50-282 AND 50-306

1.0 INTRODUCTION

By a letter dated December 10,1998, as supplemented on December 17,1998, Northern States Power Company (NSP) submitted a request for an interpretation of the Prairie Island Nuclear Generating Plant (PINGP) technical specifications (TS) with respect to the applicability of the quadrant power tilt ratio (QPTR) limits specified in TS.3.10.C, such that the OPTR limits of this specification are not applicable at power levels less than 50 percent of the rated reactor thermal power. QPTR limits ensure, in part, that power 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. The licensee indicated that, based on prior experience, the planned startup of Unit 2 from a refueling outage will likely result in QPTR greater than 1.02 at power levels less than 50 percent, and that the unit could be in this condition (QPTR greater than 1.02 at less than 50 percent power) for longer than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> due to planned testing of the new low pressure turbine rotors. Therefore, the licensee is seeking the interpretation to prevent any unnecessary plant shutdown during a plant startup operation in which QPTR of greater than 1.02 at power levels below 50 percent is expected.

2.0 EVALUATION PINGP 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:

a.

Correct the QUADRANT POWER TILT RATIO to less than 1.02, i

l b.

Restrict core power level so as not to exceed RATED THERMAL POWER l

less 2% for every 0.01 that the QUADRANT POWER TILT RATIO exceeds 1.0.

)

2 TS.3.10.C.2 states:

If the OUADRANT 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 r. Ming, for testing, shall be permitted.

TS.3.10.C.3 states:

Except for PHYSICS TESTS if the OUADRANT 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.

and 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.

The bases for TS.3.10.C states:

Operational experience shows that normal OUADRANT POWER TILT RATIOS are less than 1,01. Thus, sufficient time is available to recognize the presence of a tilt ano correct the cause before a severe tilt could build up. During start-up and power escalation, however, a large tilt could be initiated. Therefore, the Technical Specification has been written so as to prevent escalation above 50 percent THERMAL POWER if a large tilt is present.

The bases for Section 3.2.4 of Standard Technical Specifications for Westinghouse Plants (NUREG-1431, Vol. 2, Rev.1) states:

Applicability in Mode 1 s 50% RTP [ rated thermal power] 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% and Fo (Z)

LCOs [ limiting conditions for operation) still apply, but allow progressively higher peaking factors at 50% RTP er lower.

The technical specifications for both Ginna and Point Beach nuclear power plants (similar in design and vintage to the PINGP: 2-loop Westinghouse plants) specify the applicability of OPTR limits at power levels greater than 50 percent of the rated thermal power. Technical Specification 3.2.4 for Ginna (Ginna has converted to Standard Technical Specifications) has applicability of " MODE 1 with THERMAL POWER ) 50% RTP," for the OTPR limits. Technical Specification 15.3.10.3.a for Point Beach also specifies applicability of the OTPR limits to "During power operation with thermal power greater than 50 percent of rated thermal power..."

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3 The NSP's letter dated December 17,1998, stated in part that "Nothing in any of the core or safety analyses for Prairie Island relies on limiting the OPTR below 50% RTP Below 50% RTP there is either insufficient stored energy in the fuel or insufficient energy being transferred to the reactor coolant to require any limitations on OPTR. Therefore, the OPTR is not a concern for operation of the Prairie Island units below 50% RTP."

3.0 CONCLUSION

Based on its evaluation of the NSP's submittal, the staff concludes that TS.3.10.C is not applicable at power levels less than 50 percent. This is consistent with the Standard Technical Specifications for Westinghouse Plants (NUREG-1431, Vol. 2, Rev.1) and the TSs of plants sirnilar in design and vintage to the PINGP (i.e., Ginna and Point Beach). The staff's conclusion is also based, in part, on the NSP's statement in its letter dated December 17,1998, that the OPTR limits at power levels less than 50 percent RTP present no safety concern for the PINGP since (1) there is either insufficient stored energy in the fuel or insufficient energy being transferred to the reactor coolant to require any limitations on OPTR below 50 percent RTP, and (2) that nothing in any of the core or safety analyses for PINGP relies on limiting the OPTR below 50 percent RTP.

Date: Decernber 21, 1998 i

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