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Insp Rept 50-285/88-22 on 880629-0718.Potential Violations Noted.Major Areas Inspected:Thermal Margin/Low Pressure Protection Sys Trip Setpoint & Limiting Condition for Operation for Excore Monitoring of Linear Heat Rate
	ML20151R914
Person / Time
Site:	Fort Calhoun
Issue date:	07/27/1988
From:	Harrell P, Reis T, Westerman T; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	;
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ML20151R908	List: ML20151R905; ML20151R914;
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	50-285-88-22, NUDOCS 8808120343
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APPENDIX A

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U.S. NUCLEAR REGULATORY COMMISSION

REGION IV

NRC In'spection Report: 50-285/88-22 License: DPR-40

Docket: 50-235

Licensee: Omaha Public Power District (0 PPD)

1623 Harney Street

Omaha, Nebraska 68102

Facility Name: FortCalhounStation(FCS)

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Inspection At: Fort Calhoun Station, Blair, Nebraska

Inspection Conducted: June 29 through July 18, 1988

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Inspectors: Z [.

P. H. Harrell, Senior Resident Redctor

[ 7/17/98'

Date

Inspector

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7 7 u]ezkm .A

I. Reis, Resident Reactor Inspector

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Approved: 7 f, / tz dw

T. F. Westerman,'. Chief, Project Section B Date

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DivisionofReactorProjects

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8808120343 880729

PDR ADOCK 05000285

Q PDC

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Inspection Summary

Inspection Conducted June 29 through July 18, 1988 (Report 50-285/88-22)

Areas Inspected: Special, unannounced inspection of the thermal margin / low

pressure reactor protection system trip setpoint and the limiting condition for

operation for excore monitoring of linear heat rate.

Results: Two potential violations (inoperability of the thermal margin / low

pressure

reporting trip function of information,

of inaccurate the reactor protection

paragraph system,dentified.

7) were i paragraph 3; and

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DETAILS'

1. Persons Contacted

OPPD

K. Morris, Division Manager, Nuclear Operations

W. Gates, Plan'c Manager

J. Fisicaro, Supervisor, Nuclear Regulatory and Industry Affairs ,

J. Gasper, Manager, Administrative and. Training Services

K. Holthaus, Manager, Nuclear Engineering

R. Jaworski, Section Manager, Technical Services

J. Kecy, Reactor Engineer

L. Kusek, Manager, Nuclear S?.foty Review Group (Acting Plant Manager)

D. Matthews, Supervisor, Nuclear Licensing

R. DeMeu1meester, Shift Supervisor

- C. Simmons, Plant Licensing Engineer

J. Spilker, Op cations Support Engineer

W. Weber, Supervisor, Reactor Perfonnance and Analysis

Denotes attendance at the exit interview conducted on July 8,1988.

Denotes attendance at the exit interview conducted on July 18, 1988.

The NRC inspectors also contacted other plant personnel including

operators, technicians, and administrative personnel.

2. Improper Limit on Excore Monitoring of Linear Heat Rate

On June 28, 1988, licensee engineers were performing setpoint analyses and

developing reactor protection system trip setpoint.1 for the upcoming

twelfth fuel cycle. The analyses revealed that the data for the limiting

condition for operation (LCO) for excore monitoring of linear. heat

rate (LHR) was incongruous with the results obtained for the previous

eleventh fuel cycle. The plant is currently operating in the eleventh

fuel cy:le. The licensee alerted the core vendor, Combustion

Engineering (CE), of the discrepancy. Together, they investigated and

found the LC0 for excore monitoring of LHR was nonconservative for

Cycle 11.

During the current cycle, the licensee was not required to monitor the LHR

with the excore detectors. The use of excore detectors is required only

when the incore detectors are inoperable. Had the licensee monitored this

parameter during the cycle with the excore cetectors, the current -

Technical Specification (TS) LC0 2.10.4(1)(c) would have allowed power

operation at a maximum level of 90 percent when the reanalysis

demonstrated that the maximum level should have been 86 percent to prevent

exceeding the required LHR margin.

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The limitation on LHR ensures that, in the event of a loss-of-coolant

accident, the peak temperature of the fuel cladding will-not exceed

2200" This limitation is normally monitored by the incore detection

sys h which provides an alarn function. In the absence 'of incore

monitoring, linear heat is evaluated by the excore detectors. However, in-

this mode, operation is limited by TS LC0 2.10.4(1)(c). This LC0 requires

operation within the bounds of TS Figure 2-6. In developing the limits of

TS Figure 2-6, the licensee failed to incorporate the required overpower

margin (ROPM) in the calculations. This resulted in an allowed

operational power greater (i.e., 90 percent versus 86 percent) than that

allowed had the R0PM been properly incorporated into the calculations.

The licensee contended that had the use of the excore monito-ing LC0 been

necessary during Cycle 11, the required LHR margin would not have been

exceeded since sufficient margin would have existed due to the margin

between the actual total planar-radial peaking factor and the TS limit of

1.85. The maximum total planar radial peaking factor recorded in the

current cycle is 1.72.

3. Nonconservative Reactor Protection System Setpoint

After the licensee confirmed the error concerning the excore monitoring 'of

the linear heat rate, the entire Cycle 11 setpoint analyses were

independently verified. It was found that the thermal margin / low

pressure (TM/LP) trip function of the r:! actor protection system was set in

a nonconservative direction by 79 pounL per square inch (psia). This

nonconservatism rendered all four TM/LP channels inoperable. Continuous

operation with inoperable reactor protection system channels is an

apparent violation of TS 2.15. (285/822-01)

The TM/LP trip .s provided to prevent operation when the departure from

nucleate boiling ratio (DNBR) is less ^.t.an 1.18. DNBR is a function of

total integrated radial peaking factor, mass flow rate, average coolant

temperature, total flow, and reactor coolant system pressure,

in calculating the TM/LP setpoint for Cycle 11, the licensee failed +o

incorporate a penalty factor involving the total integrated radial peaking

factor into the calculation. This resulted in a TM/LP setpoint lower than

would normally be allowed. The significance of this is that during a

depressurization event, the reactor would not trip until pressure

decreased by 79 psia below the desired setpoint. This reduced pressure

would cause conditions which would put the core closer to DNB.

FCS has not oxperienced any depressurization events during Cycle 11. The

licensee contends that had one occurred, the violation of-the TM/LP

limiting safety system setting would not have allowed the DNBR limit to be

exceeded because of the conservatism of the total integrated radial

peaking factor inherent in the Cycle 11 core. This conservatism is

reported by the licensee to be 180 psia.

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The total

reactor radial p(eaking

pressure Pvar) wasfactor used

1.80 as in thebycalculation

allowed of thermal

TS. Paragraph 3.4.5 margin

of the

Updated Safety Analysis Report states that the maximum expected total

integrated radial peaking factor for Cycle-11:is 1.69. - The actual maximum

recorded to date has been 1.68. Using the' smaller value of the total

radial peaking factor in calculating Pvar would trend this pressure in the

conservative direction. The licensee stated that a value of 1.80 was used

because the engineers realized that the value was conservative. The

licensee stated that this cognitive action was taken to coaservatively

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establish core operating limits as the engineers routinely add as much

conservatism as possible to the calculations. This was done to ensure.

that the plant is opented with as much conservatism as possible within

the established plant imitations.

The licensee reported at the error resulting from the failure to

incorporate the total .ategrated radial peaking factor penalty factor into

the computations was 79 psia in the nonconservative direction. This

results in the as-found TM/LP setpoint being conservative by (180-79)

101 psia as reported by the licensee.

NRR will review the licensees calculations to verify the conservatism

asserted by the licensee.

4. Root Cause

Prior to Cycle 11, the licensee performed its setpoint analyses manually

using an NRR-approved methodology. The results were verified internally

within the licensee's organization. Beginning with Cycle 11, the licensee

employed a computer-aided technique of performing the setpoint analyses.

Due to a misunderstanding between CE and the OPPD staff during training, i

the licensee wrongly assumed that the R0PM term and the total integrated !

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radial peaking factor penalty factor had been incorporated into the

computer program algorithm, while' the CE instructor training licensee

personnel on the use of the new software assumed that the licensee would

incorporate these factors.

The NRC inspector determined that the computer program supplied by CE was

purchased under the requirements of the licensee's quality assurance (QA)

program and the computer program is maintained in accordance with QA

requirements. However, the licensee stated that no instruction manual was

supplied with the computer program to inform the user on how to properly

input data into the program.

When the licensee changed from manual calculations to computer program j

calculations, NRR was not notified via a change to the Topical Report used 1

to describe the method of setpoint analyses used by the licensee. The

licensee stated that a change was not required because the .me nathod was "

being used, but in a computer program fonnat.

The licensee personnel that performed the calculations for Cycle 11 were

somewhat taxperienced in performing the calculations because they had

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only done the calculations one previous time. This fact may have

contributed to the omission of the R0PM in the calculation. To ensure

that errors are not inadvertently made by the plant staff during the-

performance of setpoint analyses in the future, the licensee stated that

they will have CE independently review all analyses.

5. Generic Implications

The licensee stated that for CE analog plants only FCS and Maine Yankee.

perform their 'own setpoint analyses. CE provides this service for the

remainder of the domestic units. CE has asserted to the licensee that

Maine Yankee methodology is not applicable and that this error was not

generic to CE analog plants.

On July 11, 1988, CE issued a letter to the licensee's supervisor of

reactor performance analysis confirming that OPPD is the only utility

organization utilizing their own personnel to generate plant setpoints by

employing the CE setpoint methodology.

6. Sequence of Events and Corrective Action

The excore monitoring of linear heat rate was found to be nonconservative

at approximately 5 p.m. on June 28, 1988. Engineers continued working

that evening and discovered that the TM/LP setpoint had also been affected

by the transition from manual to computer-aided calculations. At this

time, neither of the errors had been quantified and it was not known

whether the TM/LP was affected conservatively or nonconservatively. The

TM/LP setpoint was found to be nonconservative and this fact reported to

the reactor engineer at approximately 7:30 a.m. on June 29, 1988. At this

time, the nonconservative error had not yet been quantified.

The NRC inspector became aware of the potential problem when reviewing the

shift supervisor's log at approximately 7:30 a.m. on June 29, 1988. The

reactor engineer had left instructions in the log to call him in the event

the linear heat rate monitoring by incore detectors became inoperable

during the night.

In addition, the reactor engineer advised the onshift operations staff via

log entry that there may be some errors in the TM/LP calculation. The

reactor enoineer informed the staff that he had detennined th1. if l

cold-leg temperature was maintained below 541 F, the margin would be !

acceptable. It was further conveyed to the operaticn. staff that there !

appear?d to be no reportability requirements on these items.

The NRC inspector also observed an additional log entry on June 29, 1988,

in which it was reported tht.t the reactor engineer called and stated that j

due to the TM/LP problem he did not want the operations staff to reset the

variable high power trip on a power increase from the present 90 percent

setting.

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At 10 a.m. on June 29, 1988, the plant manager, reactor engineer, and

technical assistants briefed the NRC inspector on the situation. They

explained that they had declared .the TM/LP channels inoperable and had

entered LC0 2.15(3) of the TS at 9:20'a.m. This LC0 requires that the

reactor be placed in hot shutdown within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months if the channels are not

returned to service. Plant management stated that resetting the TM/LP

trip setpoints had begun and that the situation would be reassessed in

4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months and at that time, if it did not appear that the equipment could be

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returned to operability within a reasonable time, an orderly shutdown

would commence. A reasonable time frame was defined as leaving 4 to

6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months for a controlled shutdown.

It was further explained that administrative controls had been placed on

monitoring linear heat rate with the excore detectors. The licensee had

determined that the parameters of TS Figure 2-6 were nonconservative.

Therefore, the shift supervisor was directed to reduce power to 80 percent

in the event that incore monitoring of linear heat rate became inoperable.

Pursuant to 10 CFR Part 50.72(b)(2)(111), the licensee made a 4-hour

report on the inoperability of the TM/LP channels to NRC Headquarters.

The report was made at 12:50 p.m.

Throughcut the day, the NRC inspector observed I&C technicians reset Ing

the TM/LP setpoints of the reactor protection system with the use of

approved procedures. The reactor engineer monitored their progress and

assisted almost continuously. At 4 p.m., three of the four channels had

been reset. The NRC inspector met with the plant manager at 4:30 p.m. to '

discuss the situation. The plant manager felt at that time the situation

was under control and he would not have to commence shutdown, although he

, was prepared to do so. At 5:30 p.m., on June 29, 1988, all four channels

of TM/LP were declared operable.

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In response to the errors identified ir, tia Cycle 11 analyses, the I

licensee requested that CE perfom an independent review for the analyses )

that were done for Cycle 10. No problems were identified during th !

review. A review of the analyses was not performed by CE for Cycles 8 l

and 9. Cycle 8 was selected by the licensee as the appropriate cycle to i

perform reverification on the analyses since the analyses method was

changed by the licensee starting with Cycle 8. The licensee submitted a !

Topical Report change to NRR and the Topical Report was approved. The

licensee felt that a reverification of the Cycle 8 analyses was not

appropriate since CE independently reviewed the analyses at the time the

calculations were performed. The licensee felt that reverification of the

Cycle 9 analyses was not required since CE worked closely with licensee

personnel during performance of the calculations.

In addition to the above actions, the licensee is also mobilizing the

management investigative safety team (MIST) to provide an indepth,

independent review of this event. The MIST was established by the

licensee to identify the root causes of events and provide recommendations

for the pennanent corrective actions to be taken to prevent recurrence.

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When the MIST completes a review of these events in the near future, the

licensee will take actions to implement the MIST recommendations.

7. Reporting

in July 1,1988, the licensee submitted a letter to the NRC sunnarizing a

telephone discussion held between the licensee, Region IV, and NRR on

'une 30,1988, regarding the nonconservative errors discovered in the

cycle 11 setpoint analyses and the corrective actions taken. The NRC

inspector reviewed this document and found some of the information to be

inaccurate.

The letter states, in part, that on June 28, 1988, the reactor engineer

contacted th shift supervisor and discussed with him the conservative

actions to te taken until the errors could be quantified. The letter

further sta'.es that the shift supervisor placed, in his log, instructions

that if any situation arose that necessitated the use of the excore linear

heat rati LC0, the unit would be brought to 80 percent power and not the

90 percent power level identified in TS Figure 2-6.

The NRC inspector reviewed the shift supervisors log entry and found the

instructions did not state that power should be reduced to 30 percent if

the affected LCO was entered. Instead, the instructions stated that the

shift supervisor should call the reactor engineer if the incore detectors

became inoperable. The NRC inspector interviewed the on-duty (3:30 p.m.

to 11:30 p.m.) shift supervisor who initially received the instructions

from the reactor engineer and the p.m. snift supervisor could not recall

receiving instructions that if the excore monitoring LC0 war invoked to

reduce power to 80 percent. At that time, he only recalls discussing a

nonconservative but nonquantified error existing with TS Figure 2-6.

In addition, the p.m. shift supervisor did not recall the 80 percent limit

being presented to him until the following day. The NRC inspector

interviewed other personnel associated with the information provided to

the on-duty p.m. shift supervisor. The reactor engineer stated that he

diriussed the 80 percent limit with the on-duty p.m. shift supervisor on

two occasions. The reactor engineer also stated thct he discussed the

80 percent limit with the night (11:30 p.m. to 7:30 a.m.) shif t supervisor ,

and the plant manager. During an interview with the night shift i

supervisor, the NRC inspector determined that the night shift supervisor :

also could not recall the reactor engineer discussing the 80 percent power j

limit. However, the night shift supervisor stated that the on-duty p.m.

shift supervisor notified him af the 80 percent power limit during siifft

turnover. j

During an interview with the plant manager, the plant manager stated to I

the NRC inspector that he had called the on-duty p.m. shif t superviser and l

had stated that, should problems with the incore detecters occur, power

should be reduced to 80 percent Therefore, it appears, eeen though the

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on-duty p.m. shift supervisor could not recall being provided with' the

information, approximately 10 days after -the event, that the information

had been provided..to him.

However, the information submitted by the licensee in the letter dated

July 1,1988, provided inaccurate information. .This is an apparent -

violation of 10 CFR Part 50.9. (285/8822-02)

8. Exit Interview

The NRC inspectors met with Mr. L. T. Kusek-(Acting Plant Manager) and

other members of the licensee staff on July 8,1988. At this meeting, the

NRC inspectors sumarized the scope of the inspection and the findings.

On July 18, 1988, the NRC inspector met with Mr. W. G. Gates (Plant.

Manager) to discuss additional information related to this inspection that

was discovered after the initial exit interview had been given.

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APPENDIX'B

. PROPOSED. ENFORCEMENT CONFERENCE AGENDA

'0MAHA PUBLIC-POWER DISTRICT- 4

August'1988 ~~

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I. Introduction and Purpose of Meeting L.-J. Callan

II. Licensee Presentation .OPPD Staff

III. NRC Contents L. J. Callan

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~IV. Licensee Response OPPD Staff

V. Closing Coments L. J. Callan

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ML20151R914

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