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LER 96-006-00:on 960207,average Reactor Power Level Exceeded License Limit Due to Insufficient Procedural Guidance. GOP-12 Revised to Treat 2,530 Mwt Limit as Absolute Limit Requiring Immediate Corrective Action If Exceeded
	ML18065A572
Person / Time
Site:	Palisades
Issue date:	03/11/1996
From:	Flenner P; CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	;
Shared Package
ML18065A571	List: ML18065A570; ML18065A572;
References
	LER-96-006, LER-96-6, NUDOCS 9603180315
	Download: ML18065A572 (4)
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NRC FORM 366 (4195)

. *U.S. NUCLEAR REGULATORYCOMMISSION

APPROVED BY OMB NO. 3150--0104 EXPIRES 4130/98 ESTIMATED BIJUJEN PER RESPONSE TO COMPLY WIT>< THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS LEARNED ARE INCORPORATED LICENSEE EVENT REPORT (LER) INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANC>i (T-8 F33). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 2055!>-

0001, ~O TO THE PAPERYilORK REDUCTION PROJECT (31~1°', OFFICE OF (See reverse for required number of digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON. DC 20503 FACILITY NAME (1) DOCKET NUMBER (2) Page (3)

PALISADES NUCLEAR PLANT 05000255 1of4 TITLE(4)

Licensee Event Report 96-006 - Average Reactor Power Level Exceeded License Limit EVENT DA TE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR I SEQUENTIAL NUMBER REVISION NUMBER MONTH DAY YEAR FACILITY NAME FACILITY NAME DOCKET NUMBER 05000 DOCKET NUMBER 02 07 96 96 - 006 - 00 03 11 96 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check one or more) (11)

MODE (9) 20.2201(b) 20.2203(a)(2)(v) 50. 73( a)(2)(i) 50.73(a)(2)(iii)

N 20.2203(a)(1) 20.2203(a)(3)(i) x 50. 73(a)(2)(ii) 50.73(a)(2)(x)

I POWER LEVEL (10) I100 I 20.2203(a)(2)(i) 20.2203(a)(2)(ii) 20.2203(a)(3)(ii) 20.2203(a)(4)

50. 73(a)(2)(iii)

50. 73(a)(2)(iv) x 73.71 OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50. 73(a)(2)(v) Specify in Abstract below or I I 20 2203(a)(2)(iv) 50.36(c)(2)

LICENSEE CONTACT FOR THIS LER (12)

50. 73(a)(2)(vii) in NRC Form 366A NAME TELEPHONE NUMBER (Include Area Code)

Philip D Flenner, Licensing Engineer (616) 764-8913 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TONPRDS TONPRDS SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR x

I YES If ves, COMPLETE EXPECTED COMPLETION DATE I NO EXPECTED SUBMISSION DATE (15) 04 30 96 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On February 7, 1996, a planned delithiation procedure was started in accordance with plant procedures. The expected result of this action was a slight increase in the power level of the reactor due to a decrease in the boron concentration. This power level increase was controlled and monitored with the maximum hourly average power reached being approximately 100.3%.

During review of the reactor power level log entries on February 8, 1996, it was determined that the license limit for maximum steady-state reactor core power level was probably exceeded. Since the hourly average power level did exceed 100% for nine consecutive hours, it was determined that this event should be viewed as a violation of Palisades License Condition 2.C.(1) which limits steady state reactor power to a maximum of 2530 Mwt. This event did not violate plant operating procedures. The procedure specified that power averaged over 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months must be less than the licensed power level. The procedure was nonconservative, however, in that it should have utilized eight-hour averaging periods rather than 24- hour periods. Further investigation has also revealed that measurement uncertainties may not have been adequately addressed in the design analyses for the power operating limits specified in plant procedures. Our investigation is continuing.

9603180315 960311 PDR ADOCK 05000255 S PDR

NRC FORM 366a 4195 -

LICENSEE EVENT REPORT {LER)

TEXT CONTINUATION

U.S. NUCLEAR REGULATORY COMMISSION I

FACILITY NAME 11 \ DOCKET12\ LER NUMBER 6\ PAGE 13\

YEAR SEQUENTIAL REVISION NUMBER NUMBER PALISADES NUCLEAR PLANT 05000255 2 OF 4 96 006 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

EVENT DESCRIPTION On February 7, 1996, with the plant operating normally at full power, a planned primary coolant delithiation procedure was started. The expected result of this action was a slight increase in the .

power level of the reactor due to a decrease in the boron concentration. This power level increase was controlled and monitored in accordance with plant procedure GOP-12 with the maximum hourly average power reached being approximately 100.3%. Nine consecutive hourly power readings (1100 - 1900) were above 100%. It was determined that power level should not exceed the full steady-state licensed power level when averaged over an eight-hour shift rather than the 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months specified in GOP-12. During two successive eight hour shifts (defined in GOP-12 as 0800 to 1500 and 1600 to 2300), the average power.level did exceed 100%.

The Palisades License Condition 2.C.(1) provides a steady state power limit of 2530 Mwt. It states:

2.C.(1) Maximum Power Level The licensee is authorized to operate the facility at steady-state reactor core power levels not in excess of 2530 Megawatts thermal (100 percent rated power) in accordance with the conditions specified herein.

If the power increase during delithiation is viewed as a transient condition, as would be consistent with GOP-12, the license limit was not violated. However, Lising eight-hour shift averaging to determine the steady state condition, a license violation occurred since this event would not be viewed as a transient. This was discovered on February 8, 1996 at* 1600 ET during a review of the hourly reactor power level log entries for February 7, 1996.

On March 7, 1996, at 1538 ET, it was determined that reactor power measurement uncertainties may not have been adequately addressed in the design analyses for the power level limits specified in plant procedures. This was reported as a probable condition outside the design basis in accordance with 10 CFR Part 50.72(b)(1 )(ii)(B). Investigation of this aspect of the event is continuing.

EVENT ANALYSIS A requirement was added in GOP-12, Revision 7 dated February 5, 1993, to maintain the reactor power level at an average of ~ 100% over a 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months period. The previous direction to Operations had been to use an eight-hour average. Since this previous direction was not considered to be based on a formal requirement, a conscious decision was made to bas.e the power level

NRC FORM 366a 4195

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME 11\

I DOCKETl2\ LER NUMBER 61 PAGE 13\

YEAR SEQUENTIAL REVISION NL'.'.lBER NUMBER PALISADES NUCLEAR PLANT 05000255 **-- 3 OF 4 96 - 006 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) calculation on 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months rather than on an eight hour shift. The procedure revision was approved in accordance with the requirements of Administrative Procedures. The procedure continued to permit the use of 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months averaging through Revision 12 of GOP-12 which was the effective revision during this event.

Other occurrences of exceeding an eight-hour average of 100% power were not found in the recent past. This was not unexpected since recent plant operation has been slightly derated. The ability to approach 100% power level during this cycle has only been achieved during the recent months.

The previous direction to the Operations Department to monitor the power level such that the ~ight hour average was below the steady state license limit was issued in 1989 in response to Event Report E-PAL-89-038. This corrective action resulted from questions about nuclear power level inputs to the Reactor Protection System. The intent of the action ,was not to address concerns about violations of license power levels; the direction was issued.in part to provide further assurance that the axial shape index limits of the Technical Specifications would be met. This direction.was superseded when GOP-12, Rev 7 was issued.

A review of the basis for the heat balance calculation resulted in the determination that the calculated uncertainties referenced in GOP-12 may not have been adequately considered when the operating power limits were specified. These uncertainties of nearly 2%; when considered with 1 1

a power level above 100%, create the possibility that the transient analysis assumptionof an initial power" level of 102% could have been exceeded. This was, therefore, reported to the N RC per 10CFR50.72(b)(1)(ii)(B) as a supplement to the original 24-hour report required by the license.

SAFETY SIGNIFICANCE The safety implications of the power level slightly in excess of 100% are minor. The highest eight hour shift averag~ power level reached on February 7, 1996 was 100.1 %. Power level peaked slightly°above 100.3% on an hourly average. The issue had been considered and was determined

.to be safe during the review of GOP-12, Rev 7 when the 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months averaging was incorporat~d.

The recent discovery that the design analyses assumption of an initial power level of 102% could have been exceeded due to measurement uncertainties is a potentially significant issue however.

This is being investigated further.

I NRC FORM 366a .

4195

LICENSEE EVENT REPORT (LER)

- U.S. NUCLEAR REGULATORY COMMISSION I TEXT CONTINUATION FACILITY NAME 11 l DOCKET12\ LER NUMBER 6\ . PAGEl3l YE.:JR SEQUENTIAL REVISION NUMBER NUMBER PALISAuE;:;; NUCLEAR PLANT 05000255 - --------- 4 OF 4 96 006 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

CAUSE OF THE EVENT The root cause for the initial event was that the procedural guidance for the operators regarding compliance with licensed steady state reactor core power levels was not sufficiently conservative.

Palisades made a conscious decision to develop their own criteria for the acceptable tolerance for the reactor power level. This decision was based on a misunderstanding of the significance of the 100% power level limit.

The root cause evaluation is in progress for the discovery that the calculated power measurement uncertainties were not adequately considered when specifying operating limits in procedures. A supplement to this LER will be submitted when this evaluation is complete.

CORRECTIVE ACTIONS The following corrective actions were accomplished:

Upon realizing that there was some possibility that the design analysis assumptions could be exceeded due to measurement uncertainties, immediate direction was given to the Operators to avoid knowingly exceeding 2530 Mwt and to take immediate action to reduce power below 2530 Mwt if it was exceeded.

Procedure GOP-12 has been revised to treat the 2530 Mwt limit as an absolute limit which would require immediate corrective action if it is exceeded. This action was completed with the issuance of Revision 14 to GOP-12.

The following corrective action will be taken:

A review of the required limits on reactor power, including uncertainties, will be performed to determine the limits that should be incorporated into the operating procedures. These limits will then be incorporated into the applicable procedures if they are different from the current limits.

PREVIOUS EVENTS No previous similar events have been found.

ML18065A572

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