ML20206S163

Application for Amend to License NPF-43,revising Tech Spec Table 3.3.3-2 Re ECCS Actuation Instrumentation for 4.16 Kv Emergency Bus Undervoltage Relay Trip Setpoint.Fee Paid

ML20206S163
Person / Time
Site:	Fermi
Issue date:	07/02/1986
From:	Agosti F DETROIT EDISON CO.
To:	Adensam E Office of Nuclear Reactor Regulation
Shared Package
ML20206S166	List: ML20206S163 ML20206S168
References
VP-86-0076, VP-86-76, NUDOCS 8607070301
Download: ML20206S163 (11)

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22" Nuclear Operations Detroit rer a Edison 55E9FN c:1.

July 2, 1986 VP-86-0076 Director of Muclear Reactor Regulation Ms. Elinor G. Adensam, Director Project Directorate No. 3 Division of BWR Licensing U. S. Duclear Regulatory Commission Washington, D. C. 20$55

Reference:

1) Fermi 2 NRC Docket No. 50-341 NRC License No. UPF-43

2) Detroit Edison to NRC Letter, " Request for an Emergency Amendment to Fermi 2 Technical Specifications Governing Emergency Core Cooling System Actuation Instrumentation Setpoints", VP-86-0065, dated June 11, 1986.

Subject:

Request for Exigent Amendment to the Fermi 2 Technical Specifications Governing ECCS Actuation Instrumentation Setpoints (Degraded Grid Relay Setpoints)

In accordance with 10CPR50.90, Detroit Edison requests an amendment to the Fermi 2 Technical Specifications.

The requested amendment will change the trip setpoint values for the Division I 4.16kV emergency bus undervoltage degraded grid relays shown in Table 3.3.3-2, item 5.b, of the Fermi 2 Technical Specifications.

Detroit Edison previously filed a similar change request as an Emergency Technical Specification change.

(Reference 2). .The emergency. request was denied, but interim relief was granted by letters from Mr. R. M.

Bernero dated June 13, 1986, and from Mr. J. G. Keppler dated June 13, 1986.

The proposed change is required for restart of Fermi-2, scheduled for July 23, 1986.

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r Ms. Elinor G. Adensam July 2, 1986 VP-86-0076 Page 2 This does not permit the Commission to follow its usual 30-day prior notice procedures. Therefore, Detroit Edison requests that this be treated as an exigent change. The attached chronology which was discussed with the Staff in our meeting on June 19, 1986, supports Detroit Edison's request that the proposed Technical Specification change be processed as exigent.

The Technical Justification for the proposed change, a Significant Hazards evaluation, and a summary of the environmental impact of the proposed change are provided in the attachments to this letter.

In accordance with 10CFR50.91, a copy of this letter has been sent to the State of Michigan.

Detroit Edison has evaluated this amendment request against the criteria in 10CFR170.21. An application fee of one hundred and fifty dollars ($150.00) is enclosed as initial payment for this application for amendment under Facility Category A (Power Reactors).

Should you have any questions concerning this amendment, please contact Mr. Frank Sondgeroth (313) 586-4203.

Sincerely, d

Attachments cc: Mr. M. D. Lynch Resident URC Inspector Supervisor, Advance Planning and Review Section Michigan Public Service Commission USNRC Document Control Desk Washington, D. C. 20555 i

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!!s. Elinor G. Adensam July 2,'1986 VP-86-0076 Page 3 I, FRANK E. AGOSTI, do hereby affirm that the foregoing statements are based on facts and circumstances which are true and accurate to the best of my knowledge and

! belief.

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i h d FRANK E. AG6STI Vice President Nuclear Operations On this N- day of M- , 1986, before me personally appeared Fidnk Ef Agosti, being first duly-sworn and says that he executed the foregoing as his free act'and deed..

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J l Notary Public

, MA.7 CIA EUCK

' Notary Public, mshicnan County, MI

My Commission Expitcs Dec. 23,1931.

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Al-1 Attachment 1 Technical Justification Technical Specification Affected 3/4.3.3, " Emergency Core Cooling System Actuation Instrumentation",

Table 3.3.3-2, Emergency Core Cooling System Actuation Instrumentation Setpoints, item 5.b, 4.16kV Emergency Bus Undervoltage (Degraded Voltage) relay trip setpoint for Division I Amendment Request The proposed amendment changes the Division I Degraded Grid Voltage trip setpoints and allowable values for the 4.16 kv Emergency Bus Undervoltage relay settings. The undervoltage relays assure that Class lE equipment in Division I is protected against undervoltage conditions which exceed equipment design criteria. The voltage setpoint was 89% of nominal. The proposed value is 95% of nominal. The proposed amendment also changes the Division I time delay setpoints. This amendment request is based on changes in the calculation of the relay trip setpoints resulting from the Fermi-2 Design Calculation Update. A copy of the proposed Technical Specification is provided in Attachment 2.

! Discussion

Background

On May 27, 1986, Detroit Edison's Design Calculation Update program revealed a potential deficiency in the calculated trip setpoints of the degraded grid voltage relays associated with the 4.16kV Division I bus. Detroit Edison notified the NRC of this potential deficiency on June 3, 1986. The chronology of events is summarized in Attachment 3.

The deficiency resulted from the discovery of two assumptions included in the design calculations that could no longer be supported by documentation. One concerned the tolerances on allowable motor operated valve (MOV) operator voltages. The design calculation previously assumed that MOV operators could tolerate voltages within +10% to -20% of nameplate. Recent.information from the manufacturer indicates that the tolerance on most motors is actually +10% to -10%. Specific MOV operators have been verified by the vendor and documented to work at voltages below the -10%

tolerance. The other assumption in question concerned the margin assumed in choosing the degraded grid relay setpoint. The design calculation previously included a margin of 4%. Documentation of the basis for this assumption is no longer available and this margin has been deleted from the calculation. Although the calculations apply to both Division I and Division II Class lE equipment, only Division I requires resetting.

Al-2 As a result of these changes, it is necessary for Detroit Edison to revise the trip setpoint values shown in Fermi-2 Technical Specification Table 3.3.3-2 to conform to the revised design calculations.

NRC Requirements The design requirement for degraded grid relays is found in NRC Branch Technical Position (BTP) PSB-1, " Adequacy of Station Electric Distribution System Voltages". The BTP requires that, in addition to the undervoltage scheme provided to detect loss of offsite power at the Class lE buses, a second level of undervoltage protection with a time delay should be provided to protect the Class lE equipment. According to BTP PSB-1, this second level of undervoltage protection must satisfy the following criteria:

a) The celection of undervoltage and time delay setpoints shall be determined from an analysis of the voltage requirements of the Class IE loads at all onsite system distribution levels.

b) Two separate time delays shall be selected for the second level of undervoltage protection based on the following conditions:

1) The first time delay should be of a duration that establishes the existence of a sustained degraded voltage condition (i.e., something longer than a motor starting transient). Following this delay, an alarm in the control room should alert the operator to the degraded condition. The subsequent occurrence of a Safety Injection Actuation Signal (SIAS) should immediately separate the Class IE distribution system from the offsite power system.

2) The second time delay should be of a limited duration such that the permanently connected Class lE loads will not be damaged. Following this delay, if the operator has failed to restore adequate voltages, the Class lE distribution system should be automatically separated from the offsite power system.

c) The Technical Specifications shall include limiting conditions for operations, surveillance requirements, trip setpoints with minimum and maximum limits, and allowabic values foc the second-level voltage protection sensors and associated time delay devices.

Al-3 Fermi-2 Compliance with the BTP In letters EF2-53522, dated June 11, 1981 (Reference 6) and EF2-53888, dated June 26, 1981 (Reference 7), Detroit Edison provided a point-by-point comparison of the Fermi-2 undervoltage protection to NRC BTP PSB-1. An NRC inspection of the Electrical Distribution System was conducted by your Mr. A. Saeed on June 23, 1981. The Fermi-2 response to degraded grid conditions is discussed in FSAR section 8.2.2.5.3 and in FSAR Appendix E.5, item 222.31A. Updated setpoint values were incorporated in the draft Fermi-2 Technical Specifications reviewed by the NRC and were issued as approved Technical Specifications with the Fermi-2 license in March, 1985.

In accordance with FSAR Appendix E.5, item 222.31A, Detroit Edison installed the required second level of undervoltage relaying to sense the degraded grid condition. The specific features of the Fermi-2 design are described below, in a format which parallels the points of the BTP presented above.

Selection of Setpoints The undervoltage relays are set in accordance with design calculations to preclude damage to Class lE equipment. A time delay setting was chosen to avoid operation of the relay during notor starting conditions.

The design calculations used to determine undervoltage relay setpoints to ensure adequate voltages for Class lE loads at all onsite system distribution levels were recently updated. The updated calculations included changes in equipment, power loads and assumptions. The nethod used in the setpoint calculation is summarized in Attachment 4. The basis for the revised assumptions is found in the referenced design calculations. This information is available for inspection by the NRC at the Fermi-2 site.

The limiting piece of equipment for the Division I degraded grid condition was determined to be a Limitorque valve operator (RHR Suction Inboard Isolation Valve, Ell 50-F009). This valve operator is fed from a motor control center connected to Bus 64C via Bus 72C. Bus 64C and bus 64B are the two Class lE monitored 4160-volt buses. The bus arrangement of Division I is shown in the schematic diagran in Attachnent 5.

The limiting piece of equipment for the Division II degraded grid condition was determined to be a pump notor fed from a Division II 4160-volt bus. In Division II, buses 65E and 65F are Class lE, monitored 4160-vcit buses. The bus arrangement of Division II is shown in Attachneet 6.

- Al-4 Alarm Setpoint Alarm relaying is provided to alert operators that a lov voltage condition exists. The alarm relay setpoints were determined on the basis of the design calculations described above. The setpoint of the alarm relay (98%) is above that of the degraded grid trip setpoint (95%). This assures that operators notice grid voltage degradation before the voltage has fallen below the minimum voltage permitted to the Class lE equipment. The alarm response procedure (ARP 9D22) specifies immediate operator actions to correct the voltage degradation. Corrective actions include, but are not limited to, starting the Combustion Turbine Generator (CTG) peaking units at the site or transferring house loads to alternate offsite AC power sources.

The proposed change modifies the degraded grid relay setpoint for Division I buses only. The Division I design incorporates a load tap changing (LTC) transformer located between the offsite power supply and the Class lE 4160-volt buses. In contrast, the Division II design provides a fixed-ratio transformer between its offsite power supply and the Class lE 4160-volt buses. In Division II, voltage regulators, rather than an LTC transformer, are provided i between the 4160-volt buses and lower voltage bus loads. This reduces the voltage changes on the Division II ESF buses calculated for the degraded grid condition. The Division II degraded grid relay voltage and time delay settings are adequate as presently described in the Fermi-2 Technical Specifications.

The proposed change in the Division I setpoints raises the voltage level at which the Class lE buses are separated from offsite power. For a degraded grid condition, this change is conservative because it ensures the availability of higher AC operating voltages on the Class lE buses.

Time Delay Setpoint A time delay is employed in the undervoltage relaying to prevent the undervoltage relay from tripping during brief voltage reductions resulting from starting large motors. Without a suitable time delay, the relay would trip during these transients, which would lead to unnecessary actuation of Emergency Diesel Generators. Detroit Edison initially considered the existing time delay to be adequate. Subsequent analysis determined the existing time delay insufficient to avoid unnecessary actuations of the Emergency Diesel Generators when the revised degraded grid relay trip setpoint is implemented.

The time delay for actuation of the degraded grid undervoltage relay is selected to be as short as possible, without causing spurious trips from motor starts. The time delay must be long enough to prevent tripping for the worst case transient. The

, worst-case motor start transient is the start of two Residual Heat

Al-5 Removal (RHR) pump motors and two Core Spray pump motors per division from a Loss of Coolant Accident signal, with the grid voltage near its lover limit. The required tine delay setting was determined from calculations of the motor start times and the response time of the Load Tap Changer (LTC). The LTC response time was found to be the limiting time delay.

During the starting transient of large motors, the bus voltage dips below the voltage at which the degraded grid relay operates.

Therefore, a trip delay time must be employed to allow the bus voltage to recover to a value greater than the reset value of the degraded grid relay. The required delay time is the sum of: (1) the delay time of the LTC sensing relay, (2) the time required for the LTC to operate, and (3) a 10% margin. The sum of these values is the proposed trip delay time of 44 seconds. This value is shown in the markup of Fermi-2 Technical Specification 3.3.3-2 provided '

in Attachment 2.

For Division II, the degraded grid relay trip delay time is controlled by the motor start times. A ten percent margin is included in the calculated trip delay time. The calculated value and the current Technical Specification value is 21.4 seconds.

Technical Specification LCOs The limiting conditions for operation (LCOs) and surveillance requirements of the Fermi-2 Technical Specification 3/4.3.3,

" Emergency Core Cooling System Actuation Instrumentation", remain applicable. The markup of Technical Specification Table 3.3.3-2 shown in Attachment 2 provides the proposed trip setpoints for Division I with minimum and maximum limits and allowable values for the degraded grid voltage sensors and their associated time delay devices.

Effect on Diesels In denying Detroit Edison's original request, the NRC expressed concern that the new, higher setpoints might cause more frequent actuation of the Emergency Diesel Generators (EDG). This would increase the number of fast, nonprelubricated (" dry") starts experienced by the Fermi-2 EDGs. Detroit Edison has examined this possibility and concluded that the proposed change will have a negligible effect on the number of fast starts of the Fermi-2 EDGs.

Actuation of the EDGs requires the voltage on the Division I ESF buses degrade to 95% of nominal. Because of the LTC transformer on the 4160-volt bus, the voltage on the 120kV line would have to degrade to 92.6% of nominal (under worst-case house loads) for the voltage on the Division I ESP buses to reach the undervoltage trip setpoint. Before the Detroit Edison system voltage falls to 92.6%,

the Detroit Edison System Supervisors can initiate actions to restore voltage to nominal values. Concurrently, the Fermi-2 operators would take correctivc action to restore nominal voltage to house loads. The Fermi-2 operators can start the Combustion Turbine Generator (CTG) peaking units onsite (18 IIW each) and can switch house loads to an alternate offsite feed.

Al-6 Detroit Edison has examined the history of voltage levels on the offsite feeds to the Fermi site. The grid has normally operated between 120kV and 125kV. Assuming the worst case condition (i.e.,

full ESP bus loads, start of two RHR and two core spray pumps), the switchyard voltage would have to drop to IllkV to actuate the degraded grid relay. For the past ten years the lowest voltage seen by the Division I supply was 119 kv.

This examination supports the view that it is highly unlikely that the higher relay trip setpoint will lead to more frequent actuation of the EDGs. From the grid voltage required to actuate the degraded grid voltage relay and the dependability of the Detroit Edison transmission system, Detroit Edison concludes that there would be a negligible increase in the probability that additional EDG fast starts will result from implementing the proposed change in Technical Specifications.

Significant Hazards Consideration The Significant Hazards evaluation is provided in Attachment 7.

Environmental Impact A summary of the environmental effects of the proposed change is provided in Attachment 8.

Basis for Exigency The impact of the current situation on restart of Fermi-2 is the basis for Detroit Edison's request that the proposed change be processed as exigent. The impact on restart is summarized in Attachment 9.

, Conclusion Based on the foregoing, Detroit Edison concludes that the proposed Technical Specification change is technically justified.

Al-7 References

1) Fermi 2 NRC Docket No. 50-341 NRC License No. NPP-43

2) Detroit Edison to NRC Letter, " Request for an Emergency Amendment to Fermi 2 Technical Specifications Governing Emergency Core Cooling System Actuation Instrumentation Setpoints", VP-86-0065, dated June 11, 1986.

3) Detroit Edison to NRC letter, " Intent to Request an Emergency Amendment to the Fermi-2 Technical Specifications Governing Emergency Core Cooling System Actuation Instrumentation Setpoints", VP-86-0066, dated June 7, 1986.

4) R.M. Bernero (MRC) letter to P.E.Agosti (Detroit Edison),

dated June 13, 1986.

5) J.G. Keppler (NRC) letter to F.E. Agosti (Detroit Edison),

dated June 13, 1986.

6) Detroit Edison to MRC letter, EF2-53522, " Branch Technical Position PSB-1, Degraded Grid Protection", dated June 11, 1981.

7) Detroit Edison to NRC letter, EP2-53888, " Amended Response-PSB-1, Adequacy of Station Electrical Distribution System Voltage", dated June 26, 1981.

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A2-1 Attachment 2 Proposed Amendment Changes Page Affected Table 3.3.3-2, Page 3/4 3-28 See markup sheet attached.

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