ML20042G169

Forwards Evaluation & Analysis Re Diesel Generator/Lpsi Pump Interlock Feature.Mod to Permanently Jumper Diesel Generator/Lpsi Pump Interlocks Initiated

ML20042G169
Person / Time
Site:	Fort Calhoun
Issue date:	05/07/1990
From:	Gates W OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LIC-90-0361, LIC-90-361, NUDOCS 9005110170
Download: ML20042G169 (14)

Text

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. ' Omaha Public Power District i

.1623 Harney Omaha, Nebraska 68102 2247 40T/536-4000 J

i May 7, 1990 LIC-90-0361 .

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U.- S. Nuclear Regulatory Commission [

Attn: Document Control Desk

' Mail Station P1-137 .

. Washington,-DC 20555 l,

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References:

1 ~. Docket No. 50-285

'2.-. Licensee Event' Report 90-006 dated March 28, 1990 ,

(LIC-90-0246) ,

, <3. Letter from NRC (S. J. Collins) to OPPD.(W. G. Gates) dated i-March 20, 1990.

l-r c Ger.tlemen:

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SUBJECT:

Diesel' Generator / Low Pressure Safety Injection Pump Interlock Feature l'

Reference 2 described an event which occurred at Omaha Public Power District's

-(OPPD) Fort' Calhoun: Station, involving a loss of .off-site power and Diesel L

Generator (DG) actuation. During the event, a low Pressure Safety Injection

.(LPSI) pump breaker. interlock functioned as designed and prevented the diesel .

from automatically energizing 4160 volt bus 1A4. OPPD committed to re-evaluate. .J the interlock feature and provide results of the evaluation. i L -0 PPD has completed an analysis' and calculation which; '

L .

L e -indicate that the DG/LPSI interlock is not necessary, a did not identify any applications similar to.the DG/LPSI interlock-which would prevent auto closure of the diesel output breaker under comparable circumstances, and i

m. found that ' dead loading the diesel generator with any one of the LPSI, High Pressure Safety Injection-(HPSI), or Containment Spray (CS) pumps (which are prevented. from load shedding when manually started) is acceptable.

The main text of the Engineering Analysis (without attachments) is enclosed.

9005110170 900507 PDR ADOCK 05000285 i P PDC

-4s ser4 Empioumengn En sai opportunitu l' i

1 1

Document Control Desk LIC-90-0361 *

.- Pag 6 2 OPPD has' initiated a modification to permanently jumper the DG/LPSI pump

. interlocks.. This modification will be completed by the end of the 1991 refueling outage. Procedures will be revised as necessary upon completion of the modification.

If you should have any questions, please contact me.

Sincerely, t

W.

W. G.. Gates Division Manager Nuclear Operations WGG/mc-Attachment p c: LeBoeuf, Lamb, Leiby & MacRae 1:

A. Bournia, NRC Project Manager R. D. Martin, NRC Regional Administrator, Region IV P. H. Harrell, NRC' Senior Resident Inspector l

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1.0 PURPOSE The purpose of this analysis is to- determine the impact on plant

-Safeguards Systems response if one of the Low Pressure Safety Injection "

(LPSI), High PressureSafetyInjection(HPSI),orContainmentSprar (CS) pumps -has been manually started and is running when a Design Basis Event-(LOCA, MSLB, Loss of Shutdown Cooling, Reactor Trip) occurs which:. ~

h 1.1 Requires automatic Engineered Safeguards Operation with offsite

• power supplying the Safeguards loads or with emergency diesel generators starting and supplying the Safeguards loads.

1.2 Requires the diesel generator to supply power to equipment needed to maintain the reactor in a safe shutdown condition following a Reactor Irip in-conjunction with a Loss of Offsite Power (LOP).

1.3 Require as a minimum one diesel generator to re-establish shutdown cooling (tPSI or CS pump, CCW. pump, raw water pump, air compressor,. and valves as required) in the event of a LOP while the reactor is on shutdown cooling. '

2.0 SCOPE The scope of this analysis is to define the impact of.the manually '

started Low Pressure Safety Injection (LPSI), High Pressure Safety injection (HPSI) or Containment Spray (CS) pump and the associated blocking of the pump motor breakers under voltage (normal loss of voltage or OPLS initiated degrade voltage) load shed breaker trip. .This' includes sequencing impacts. The areas to be assessed are:

2.1 The effect on the successful load sequencing of Safeguards pumps and fans on to the electrical system being supplied by the offsite power or the diesel generator (this is applicable for both safety trains) in response to a DBA (LOCA or MSLB).

2.2 The additional operator actions, if any, required to assure proper Safeguards Systems response to a DBA and the time frame for accomplishing these actions.

L 2.3 The required operator actions to place the plant. in a= safe configuration in the event of a reactor trip and Loss of Offsite Power with no DBA.

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2.4 The required operator actions to re-establish shutdown cooling-following a loss of offsite power and diesel: generator automatic.

start for the cases where either a LPSI or CS pump is used for coolant circulation through the reactor.

2.5 The advisability of a modification which would enable the F undervoltage load shed to operate after a manual start of an LPSI, HPSI or CS pump, and- the need to maintain the original design basis function permitting operator action to attempt pump operation regardless of bus voltage as a last resort measure:due to multiple failures of the electrical system beyond present

[ single failure assumptions. Several options will be assessed.

3.0 INPUTS TO THE ANALYSIS 3.1 OCR FC #9-73 Install Jumpers in Engineered Safeguards Undervoltage Load Shed Circuits 3.2 Surveillance Test ST-SI/CS-1, SI/CS Pumps and valves, Rev 56, 3.3 Operating InstrJCtlon 01-SC-1, Initiation of Shutdown Cooling, Rev. 34, 3.4 Abnormal Operating Procedure A0P-17 Loss of Shutdown Cooling, Rev. 1.

3.5 Operating Instruction 01-SI-1-1, Safety Injection Normal j Operation, Rev. 64.

3.6 Calculation FC 05393, Diesel-Generator Sequential Loading SI/CS i

Pumps Out of Normal Sequence, Rev. A.

l- 3.7 Calculation FC 04943, Bus 1A3 and Bus 1A4 OPLS Setpoints and FW-6 Starting, j i

3.8 Calculation FC 04315, Diesel Generator Sequential Loading.

3.9 Calibration Procedure SP-CP-08-Devar-TIA4, Rev. O. s 3.10 Surveillance Test ST-ESF-2, Safety Injection Actuation, Rev. 62.

3.11 Drawings Dwo. #/Sht. # Title Rev. #

11045-E-27, Sh. 1 Breaker 1AD1 Schematic Rev. 17 11405-E-27, Sh. 2- Breaker 1AD2 Schematic Rev. 16 161F597, Sh. 9 AI-30A Rev. 7

EA-FC-90-027 Rev. 0 Page 14

- eaj Dwa. #/Sht. # Title Rev. #

161F597, Sh. 5 AI-30A -Rev. 13 161F597, Sh. 4 AI-30A Rev. 13

. 161F597, Sh. 8 AI-30A Rev. 9 161F598, Sh. 9 AI-30B Rev. 7 161F598, Sh. 5 AI-30B Rev. 15 161F598, Sh. 4 AI-30B Rev. 8 161F598, Sh. 8 AI-30B Rev. 8 E-4027 OPLS Voltage Matrix Rev. 7

'11405-E-23 SI-1B Breaker Rev. 13 11405-E-17 SI-1A Breaker Rev. 17 11405-E-13 UV Load Shed Rev. 20 11405-E-142 HPSI Schematic Rev. 13 11405-E-143 CS Schematic Rev. 21 Fig. 8.1.1 Simplified One Line Rev. 45 3.12 Test SP-SI/CS-3 Simultaneous Operation of LPSI and HPSI Pumps on Minimum Recirculation Mode, Rev. O.

3.13 Station Blackout Coping Assessment, Impell Report 01-1390-1763, Rev. O.

4.0 REFERENCES

4.1 Modification MR-FC-88-110, SI-3/A/B/C Start Signal Logic Change, Rev. 1.

4.2 Licensee Event Report (LER) 90-05

i EA-FC-90-027 Rev. O Page 15 eaj 5.0 ASSUMPTIONS 5.1 During power operation, only one LPSI, -HPSI or CS pump is'in operation. This is consistent with the requirement and practice of the Operating Instructions and Surveillance Testing procedures listed in Section 3. One pump is operated at a time for ISI testing, Safety Injection Tank filling,- and verification of operability of a pump due to redundant pump's removal from service for testing or pump failure.

6.0 ANALYSIS 6.1 HPSI, LPSI, and Containment Sorav Pumo Motor Breaker-Interlocks 6.1.1 Each of the SI/CS pump motor breakers is wired such that if the pump is manually started via control switch on AI-30A or Al-308, contacts from the control switchinhibittheundervoltageload shed breaker trip of the running pump. The purpose of this load 1 shed is to permit the resequencing of the CS and SI Pumps on to the diesel generator if initially loaded on the safet to a DBA and subsequent Loss of Offsite Power (Input 1)y buses due 6.1.2 Each of the LPSI Pump Motor Breakers provides a permissive for the : associated diesel generator output. breaker to close and energize the safety related 4160V bus (DG-1-1A3 or DG-2-1A4).

This requires that the associated LPSI Pump Motor Breaker (SI-1A i for DG-1 and SI-1B for DG-2) be open (tripped condition), to permit automatic closure of the diesel generator output breaker.

6.2 Imoact of a CS or S1 Pumo Runnino on Response to a DBA 6.2.1 LPSI Pump Running Due to Manual Start 6.2.1.1 Event -

OBA (LOCA or MSLB)-Offsite Power Available-LPSI Pump  !

Running If a DBA were to occur and offsite power remained avail _able, the running LPSI Pump would continue operation while the balance of the Safeguards Loads not already running would sequence on as designed. The . impact on these systems during sequencing would occur at the time the loop injection. valves open and on the first load group. The effect on the loop injection valves would result in slightly lower voltages to the valve motors; this is judged insignificant in that the LPSI Pumps are 4160V motors and have minimal impact on the 480V power distribution level. The 250KVA load of a LPSI pump that is already loaded at 4160V buses 1A3 and' 1A4 load at 10,000 and 14,000KVA respectively is a very small load increase (Input 6). The effect on load group 1 is an improvement in the voltage available to accelerate the motors since there is no requirement to accelerate the LPSI pump.

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EA-FC-90-027 Rev. O Page 16 eaj.

i The. voltage at the loop injection valves. is expected to be. i' adequate during the first load group in that the transient load is reduced, reducing the voltage transient seen by the valve-motors and contactor controls.

6.2.1.2. Event-DBA - Loss of Offsite Power-LPSI Pump Running ,

If a DBA occurs ' coincident with a loss of offsite power or. l offsite power is lost subsequent to the DBA event the Safeguards .i must be sequenced on the diesel generator. -l The diesel generator breaker associated with the running LPSI l Pump will not automatically close and sequentially load.

Operator action to trip the LPSI pump motor breaker would be  ;

required to initiate automatic loading of the. Safeguards loads. .

6.2.2 CS or HPSI Running - Manually Started-0ffsite Power Available )

If a. DBA were to occur while one of the CS or HPSI pumps was- I running, the pump would continue to run while the remaining i Safeguards loads were sequenced on. 4 1

In this analysis the HPSI or CS pump running on a 480V bus during

sequencing has its prime impact on those motors which normally  ;

start before the HPSI or CS pump in question and are located on <

the same bus (load center) or bus and tied swing bus and secondarily and on total group acceleration time. The impact on.

motor acceleration time and the total load group start resultant voltage transient on the associated 4160V bus may actuate OPLS.  !

If the transient is over 4.75 seconds long and resulting 4160V bus voltage is less than the OPLS set point, an OPLS actuation i

will occur. Input No. 7 curves on page 63 through 68 were used i to determine the impact. For the 4160V -bus heavily loaded t condition the addition of a CS or HPSI pump running due to manual l start leaves little voltage.or time margin. An OPLS trip under these conditions may occur depending on which specific HPSI or CS L pump is running and would be considered a proper plant response.

l The OPLS trip load sheds the-bus and resequences the loads'onto the diesel generator. The effect on other Safeguards Motor Starts by a specific CS or HPSI pump running is discussed on a i pump-by-pump basis as follows.

6.2.2.1 HPSI" Pump SI-2A, Bus 183A, Load Group 1 The effect of this pump which normally starts in the first load group is that the transient is reduced on the first load group because the running current requirement of the motor is much less than the starting current. No impact is expected on tne second load group, beyond what has been already analyzed. No change is i

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EA-FC-90-027

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Rev. 0 Page 17-eaj-expected in loop injection valve performance, the first load group. start transient, which occurs during valve opening, is reduced- in magnitude and the pump running do.es -not have a significant effect on bus ~ voltage, because no other loads on that.

bus are sequenced on.until valve opening is nearly' complete at 8 seconds into the event.

6.2.2.2 HPSI Pump SI-28, Bus 184C, Load Group 1 The bus voltage response to this motor start is expectedito be the same as SI-2A, see section 6.2.2.1.

6.2.2.3 HPSI Pump SI-20, Bus 183A-4A, Load Group 2 The running of SI-2C is expected to have an effect'on the starting time for SI-2A, present worst case starting time is 3.52~

seconds, minimum allcwable time until next load group is 4.15 seconds, OPLS would occur at 4.75 seconds (earliest). If SI-2A-is not fully accelerated by the second load group start, OPLS i would be expected at 4.75 seconds with bus load shedding and ~;

sequential loading of the diesel generator. The loop injection valves are expected- to open if.SI-2A accelerates to full speed.

If not the diesel generator would provide power to open the. ,

valves. The impact on load group 2 if load' group 1 does not r initiate OPLS is . reduced due to the already running SI-2C, no-starting current is required.

6.2.2.4 CS Pump SI-3A, Bus 183C, Load Group 4 The running of SI-3A is expected to have its greatest impact on the starting of AC-3C on bus 183C-4 during the second load "

group. If AC-3C cannot accelerate OPLS will activate, there is little margin available. There are no loop injection valves 'i associated with bus 183C, no.cffect on these valves is expected.

6.2.2.5 CS Pump SI-3B, Bus 1848, Load Group 4 The running of SI-3B is expected to have its greatest impact on the starting time of CH-1C in the third load group. The size of the charging pump is 75 HP and is not expected to affect voltage recovery on bus 1A3, an OPLS actuation is not expected. There are no loop injection valves associated with Dus 1848, 6.2.2.6 CS Pump.SI-3C, Bus 1838-48, Load Group 5 The running SI-3C is expected to have the same effect on CH-1C and the loop injection valves as SI-38. During the starting of SI-3B, the affect of a running SI-3C is to increase acceleration ,

time of SI-3B that may result in a OPLS actuation.

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6.2.2.7 Operator Action - Offsite Power Available An assessment of two operator actions is required:-

a. If an operator desires'to manually trip a running SI Pump ,

or Containment Spray Pump to limit its starting transient '

effect (i.e., prevent possible trip of OPLS), a manual trip i of the pump needs to be accomplished within three seconds of the Safeguard Initiation Signal. All sequencing will be completed- within one minute. -Therefore, Operator action to

_ prevent a possible OPLS trip is not credible,

b. Due to the limited capacity (600 gpm) of the SI/CS Pump mini recirculation system,- operator action would be required to trip a CS pump if it were the pump running via a manual start and safeguards were initiated. The manual action would. only be required.if there was no LPSI, HPSI, or CS flow,- as could occur under certain-uncontrollad heat extraction events. The present safeguards logic .is designed to start the HPSI and LPSI pumps first and if containment spray is required (spray flow to the headers),

the CS pumps would be sequenced on the bus. In this .

arrangement the 2 LPSI and 3~HPSI pumps require-505 gpm- '

recirculation (LPSI 200 each, HPSI 35 each). A manually  ;

started running spray pump would require an additional 200 '

gpm recirculation flow. Under these conditions where there is a 95 gpm excess and an expected balancing of recirculation flow between all six running pumps, some pump heating is expected, however, based on Input 12 which shows no significant heating with 2 LPSI and 3 HPSI pumps running, is judged that adequate time (30 minutes or

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it more)wouldbeavailabletotriptheCSpump.

6.2.3 CS or HPSI Pump Running.- Loss of Offsite Power If a CS or HPSI pump is manually started the breaker will not- _

trip on Loss of Offsite Power and if Safeguards automatic loading-is required during this time the pump is running (in response to a DBA), the pump motor will be a dead load on the diesel generator. l l

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.Rev. 0 Page 19 eaj 6.2.3.1 Effect on Diesel Generator Sequential Loading A calculation was performed to model the diesel generator sequential loading and is listed as Input 6. The results of this. ,

calculation show that the demands on the diesel generator for the altered portion of the sequence are less than that calculated for '

the original plant design, Input 8. The Peak load kilowatts are as follows:

r Peak KW Requirement A Original Revised Per CS or HPSI Desion MR-FC-88-110 Pumo Runnino OG-1 3260* 3028.3 2678.4 l DG-2 3260* 2669.4 2694.8  !

• only one' calculation performed -'

Based on the above information, diesel generator operation is not-expected to be affected.

6.2.3.2 Operator Action 1

No operator action is required to assure diesel generator '

automatic loading with a CS or HPSI pump running.

-6.3 Imoact of an SI Pumo Runnino on Response to a Reactor Trio _ Loss  ;

of Offsite Power i

6.3.1 LPSI Pump Running If- a LPSI pump is running-the associated diesel generator would l start but would not automatically re-energize the bus. In this case, operator action is required to trip the LPSI pump so that '

the diesel generator can automatically re-energize the bus. Once this is complete response to a trip will be as directed in the E0Ps. If the redundant diesel generator is operating correctly 4 the tripping of the LPSI pump is not an immediate-priority action. In any event, adequate operator action is possible since the described event is bounded by the Station Blackout Study.

6.3.2 CS or HPSI Pump Running No specific operator response is required, the running pump is a dead load to the diesel generator and is well within the diesel generator capacity, an HPSI or CS pump is approximately 10% of the DG capacity. There are no automatic loads due to a reactor trip except FW-6 which is approximately 10% of the diesel generator capacity. Actions as directed in the E0Ps are considered adequate.

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6.4 ImDact of an SI Pump Runnino Durino Shutdown Coolino Response to loss of Offsite Power 6.4.1 LPSI Pump Running - One Diesel Generator Available

-If offsite power were lost the diesel generator associated with the running LPSI pump would automatically start but would not energize the bus. The operator would be required to trip the LPSI Pump then reload the pump after the diesel generator automatically energizes the bus. The operator would then manually start the other plant systems requ Ned to maintain shutdown cooling. This is, in fact, what occurred on 2/26/90 as described byLER90-06(Reference 4.2). The operator tripped the LPSI pump breaker and re-energized the bus via the DG within 44 secorids of loss of offsite power.

6.4.2 CS Pump Running - One Diesel Generator Available If the offsite power were lost the diesel generator would automatically start and re-energize the bus picking up the CS pump as a dead load. The operator would then manually start the other plant systems required to maintain shutdown cooling.

6.5 Identified Deficiencies and Corrective Actions 6.5.1 Design Dc?iciencies The following deficiency has been identified in the analysis to this point:

Diesei Bresker auto closure is blocked when a LPSI pump is manually started and running at the time offsite power is lost.

6.5.2 Possible Corrective Actions  !

6.5.2.1 Delete LPSI Breaker - Diesel Breaker Interlock The diesel generator breaker close permissive (see Section 6.1.2) could be deleted. The running LPSI pump is of such a size that it can be picked up as a dead load, with no effect on the.

generator sequential loading. D2ference 6, Calculation FC-05393, demonstrates that diesel generater loading will not be affected.

Therefore, the original justification for this design feature has been shown to be invalid and there is no negative impact from its deletion.

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e EA-FC-90-027 Rev. O Page 21 eaj 6.5.2.2 Delete Manual Start Override of Undervoltage Load Shed All CS and SI pump controls could be altered to trip on undervoltage load shed no matter how the pump is started. This could be done with a jumper in the control circuit to defeat the control switch block of load shed. The negative effect of this design change is that an operator would no longer have the ability to attempt a manual startup of any of these pumps during a post-accident, undervolta condition. However, this ability is likely not useful anyway,gesince a motor requires 90% or better.

of rated voltage to successfully start, As an alternative, a bypass switch could be added to enable load shed at all times during normal operation or placed in bypass to permit the operator to close the breaker regardless of bus voltage condition. Deletion of the diesel generator breaker auto close permissive of the LPSI Pumps would'not be necessary in this case. Please note that Human Factor considerations-indicate that all 8 SI and CS pumps should operate the same way.

7.0 CONCLUSION

The permissive 3 or interlock 3between LPSI pump breaker and DG breaker closure should be deleted (CorrectiveAction6.5.2.1). This eliminates the possibility of not having a diesel generator automatically load in-the event of a DBA and Loss of Offsite Power. This would result in a very small increase in the probability of an OPLS actuation in the event of a DBA. There is little margin between the-trip setpoints and expected bus voltaget Jnder low offsite power voltage conditions. The effect of an SI or CS pump running is approximately an additional 250KW in the first load groups with approximately 10,000KW on bus 1A3 and 14,000KW on bus IA4, which is a very small change. The OPLS would be functioning as designed under these conditions. Physically, this design change has very minor impact as it involves the jumpering of two contacts in the Control Room.

8.0 ATTACHMENTS Title Number of Paoes

1. DCR 9-73 43 i

2. ST-SI/CS-1, Rev. 56 39  ;

3. 01-SC-1, Rev. 34 7 I 4 A0P-19, Rev. 1 i 23 .l

5. 01-51-1, Rev. 64 32  !

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6. . Calculation FC 5393, Rev.'A 17 .l

p. ~7.- Calculation FC 4943, Rev. 0 106' '

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8. Calibration SP-CP-08-Devar TIA4 .Rev. O. 5  ?

g 9. ST-ESF-2, Rev. 62' 25 i

10. SP SI/CS-3, Rev. 0 23  !

11. ' Station Blackout Report, Rev. 0 - 67 't t

12. MR-FC-88-110, Rev._1 4 j, s

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