05000410/LER-1987-045, Corrected LER 87-045-00:on 870729,two Separate ESF Actuations Occurred.Caused by Lack of Administrative Controls & Personnel Error.Surveillance Procedures Revised to Prohibit Concurrent Performance
| ML20237K852 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 08/28/1987 |
| From: | Lempges T, Randall R NIAGARA MOHAWK POWER CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML17055D185 | List: |
| References | |
| LER-87-045-01, LER-87-45-1, NMP26443, NUDOCS 8709080072 | |
| Download: ML20237K852 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| 4102087045R00 - NRC Website | |
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Robert G. Randall, Superv'sor sTechnical Support .a'3 f6,, 349-2>'4 5 CoM.titi e4E Leht som tacw cou,ong%f pastung og scaisto ik twig at, oat n,i caa/ s. m v cow os m "t:lF "Ml^!;' c..si s. ev c:v nis- l "q:;f ag;;;;s
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On July 29, 1987 Fine Mile Point Unit 2 experienced two separate Engineered Safety Feature (ELF) actuations. Both ESF actuations consisted of secondary containment- isolations with subsequent Standby Gas Treatment System (GTS) ini tiation s.. At the time of the events the mode switch was in the "STARTUP" position with reactor peser at 3.5 percent.'
) The cause of ,the first event was lack of administrative coqtrols to prohibit l j' concurrent performance of surveillance procedures which af #ect the same or l, ,
closely related systems. The cause of the second event was personnel error when operators atterpted to return the Reactor building Ventilatio: Sfstem (HVR) back
'to normal with an emergency recirculation fan running.
87090faOO72 P70831 Corrective actions include: PDR ADOCA 05000410 S PDR
- 1. Establish a policy which prohibits concurrent performance of surveillance l
procedures which are closely related. /
- 2. Revise procedures which were involved in the event to prohibit their concurrent performance. ,
- 3. Add a note to the " Lessons i. earned" book in the Cchtrol Room detailing system lineups required before restoring HVR back in'o service and emphasizing the need to strictly adhere to the operating procedures.
- 4. An independent evaluation shall be performed which will explore ways to reduce unnecessary challenges to the GTS from other interrelated systems.
Modifications and ;r procedure changes shall be made as determined by this independent evaluatior.
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l I. DESCRIPTION OF E IT ;
I Or, July 29, 1987 Nine Mile Point Unit 2 experienced two separate Engineered /
Safety Feature (ESF) actuations. Both ESF actuations consisted cf secondary containment isolations with subseauent Standby Gas Treatment System initiations.
At the' time of the events the mode switch was in the "STARTUP" position with reactor power at 3.5 percent. The first event was the result of performing two interrelated surveillance procedures concurrently without identifying the adverse consequences one procedure had on the other. The second event was caused by the improper restoration of the Reactor Building Ventilation System (HVR) back into service following tM first event with an emergency recirculation fan running.
Plant conditions leading up to the ESF actuations were as follows:
- 1. Standby Gas Treatment Train A was running for monthly surveillance test N2-0SP-GYS-M001, " Standby Gas Treatment System Functional Test". In support of this test, Trair. A of the Reactor Building Ventilation System (HVR) Emergency Recirculation Subsystem was in operation in the recirculation-test mode in accordance with Operating Procedure N2-0P-52, " Reactor Building Ventilation System". The emergency recirculation units 2HVR-UC413A and B normally take their suction on the normal ventilation exhaust plenum (Figure 1) which serves the areas of the reactor building below the refueling floor. Each recirculation unit suction duct is eodipped with an air-operated damper 2HVR*A006A and B and an air-operated test damper 2HVR*AOD34A and B (Figure 1). The test dampers allow test operation of the recirculation units while the respective suction dampers are closed. While in the recirculation-test mode the emergency recirculation units draw suction through 2HVR*AOD34A and B and the normal dampers, 2HVR*A006A and B, are closed.
- 2. Radi8 tion Protection Surveillance Procedure N2-RSP-RMS-M108, " Channel Functional Test of the Reactor Building Above the Refuel Floor Process Radiation Monitors", was also in progress. This monthly test provides direction for performing a channel functional test of the Reactor Building above the Refuel Floor process radiation monitors, 2HVR*RE14A and 2HYR*RE14B (Figure 2). The test was being performed for 2HVR*RE14A. Upon receipt of a high radiation signal these process radiation monitors perform the following actions:
Isolate the Reactor Building Ventilation system by closing secondary containment isolation dampers.
Provide auto-start permissive signals to emergency recirculation units UC413A and 4138.
Start the Standby Gas Treatment system f an and filter train.
- Energize a high radiation annunciator in the control room.
During the performance of N2-RSP-RMS-M108, the energizing and de-energizing of the primary relays for the automatic trip functions resulting from exceeding the high radiation trip setpoint are verified. This includes the primary relays that would provide the isolation of the Normal Reactor Building Ventilation System, activation of the Reactor Building Emergency Recirculation System, and activation of the Standby Gas Treatment System.
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Nine Mile Point Unit 2 o ls t o l o l o l 410 87 - 045 - 00 03 or OS ven ~ ., , - m - m ,
The first event occurred at 1023 hours0.0118 days <br />0.284 hours <br />0.00169 weeks <br />3.892515e-4 months <br />. Jumpers had been installed per N2-RSP-RMS-M108 to prevent a Division I secondary containment isolation upon energization of the associated trip relay. Per procedure, a high radiation ,
signal was then simulated into the trip relay for 2HVR*RE14A. This caused the l inlet test damper to 2HVR*Urd13A (2HVR*AOD34A) to close and the normal inlet i danper (2HVR*AOD6A) to open. This resulted in 2HVR*UC413A taking suction on the Below Refuel Floor Exhaust Plenum which is a comon suction with the Below Refuel Floor Exhaust Fans 2HVR*FN2A and B. Thus both the emergency recirculation unit, 4 2HVR*UC413A, and the Below Refuel Floor Exhaust Fan 2HVR*FN2A were drawing suction on their common exhaust plenum. The comon fan suction duct for Below Refueling Floor Exhaust Fans 2HVR*FN2A and B, is equipped with two flow switches 2HVR*FS37A and B. These switches actuate on low flow. With 2HVR*'UC413A drawing suction on the same plenum as the exhaust fan 2HVR*FN2A and recycling air back into the reactor building an air flow inbalance was created. In this case more ,
air was being supplied to the reactor building than was being exhausted. The flow inbalance caused the reactor building pressure to increase from -0.78 to
+0.32 inches of water gauge pressure before the flow switches 2HVR*FS37A and B actuated on low flow. This resulted in a secondary containment isolation and 1 subsequent auto-start of GTS Train B (Train A was already running) which restored l reactor building pressure to normal. The total duration of the event was i approximately 90 seconds. j l The second event occurred at 1058 hours0.0122 days <br />0.294 hours <br />0.00175 weeks <br />4.02569e-4 months <br />. While attenpting to restore Reactor l Building Ventilation system back to nortnal operation from the first event another secondary containment isolation occurred. GTS Train B had been restored to normal prior to the event. The Niagara Mohawk licensed operator at the remote panel started a normal supply (2HVR*FN1A) and a normal Below Refuel Floor Exhaust Fan (2HVR*FN2B). He then started another supply fan and the normal Above Refuel Floor Exhaust Fan (2HVR*FN5A). He then noticed that the Below Refuel Floor Exhaust Fan he had previously started (2HVR*FN2B) had tripped. A start of the l
Standby Below Refuel Floor Exhaust Fan (2HVR*FN2A) was attempted but this fan I tripped on notor electrical fault. Thus, with two supply fans and one exhaust fan running, the reactor building overpressurized causing all reactor building supply fans to trip off and a subsequent low flow secondary containment isolation. A Niagara Mohawk licensed operator in the control room noticed reactor building inside /outside differential pressure approaching its high setpoint (greater than 3 inches water gauge pressure) and had manually started GTS System Train B to assist in restoring pressure to normal. This action did not prevent the Reactor Building from equaling its high differential pressure setpoint of +3.00 inches of water gauge.
{ Af ter reaching a maximum differential pressure of +3.00 inches of water gauge, l the pressure decreased to a differential pressure of -0.257 inches of water gauge due to the manual start of the GTS thus ending the event. The total duration of the event was approximately three and one half minutes.
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Nine Mile Point Unit 2 oisjolol0l 410 87 - 045 - 00 04 or 08 II. CAUSE OF EVENTS A root cause analysis has been conpleted for each of the events per Site Supervisory Procedure S-SUP-1, " Root Cause Evaluation Program".
The root cause of the first event has been attributed to inadequate administrative controls. There is no policy to prohibit concurrent perfomance of surveillance procedures which affect the same system or closely related systems. If operators in the control room had not allowed both surveillance tests to be run simultaneously, the event would not have occurred.
Contributing to this event was a personnel error by an Assistant Station Shif t Supervisor (ASSS) who made an attenpt to identify any adverse consequences of perfoming the two surveillance tests concurrently but failed to identify the action of the contacts mentioned above.
The cause of the second event was cognitive personnel error by the operator who was restoring the HVR back to nomal operation. Operating Procedure N2-0P-52,
" Reactor Building Ventilation", gives detailed instruction for the startup of the nomal reactor building ventilation system. A low flow trip of the below refuel floor exhaust fan (2HVR*FN2A) was caused by the emergency recirculation unit 2HVR*UC413A operating in its normal mode with the normal damper 2HVR*A0V6A open and the test damper 2HVR*A0V34A closed. This resulted in 2HVR*UC413A and 2HVR*FN2A drawing suction on a common plenum. With both units competing for air from the same plenum their flow rates fell causing a low flow trip signal from 2HVR*FS37A and B.
The operating procedure specifies that a valve and danper lineup be verified before starting the nomal reactor building ventilation system. This line up specifies that 2HVR*A0V34A and 2HVR*A0V6A be closed. The procedure also specifies that 2HVR*UC413 be secured if running.
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0l0 0l5 of 0 l8 w w,, . w. wcn,su mn III. ANALYSIS OF EVENT
.The secondary containment at Nine Mile Point Unit 2 is designed to be maintained at a negative pressure of 0.25 inches of water gauge with respect to the surrounding outside atmospheric pressure. The secondary containment provides a means of controlling fission product release to the environment. Upon exceeding the high differential pressure setpoint of +3.00 inches of water gauge the Standby Gas Treatment System initiated (operator action was taken before +3.00 inches of water was reached) and the Secondary Containment Isolation Valves closed as designed to re-establish a relative vacuum in the Reactor Building.
Thus, all systems responded as designed. No safety consequences would have resulted from these events at any other power level.
IV. CORRECTIVE ACTIONS l
Initial operator action for each event was to verify that reactor building pressure returned to normal and that all automatic systems had responded as designed. Immediate corrective action was to initiate a work request (WR 123415) to troubleshoot the cause of the Standby Below Refuel Floor Exhaust Fan motor electrical fault. 3 l
To prevent similar events from recurring in the future the following corrective actions have been or will be taken:
1 A policy shall be established that prohibits concurrent performance of surveillance procedures which affect the same system or closely related systems unless explicitly stated in the procedures.
- 2. Steps shall be added to the applicable procedures which were involved in the first event to prohibit their concurrent performance. j l
- 3. A note shall be added to the " Lessons Learned" book in the Control Room detailing the system lineups reauired before restoring the HVR back into j service and emphasizing the need to strictly adhere to the operating i procedure when doing so.
4 An Independent Safety Evaluation Group (ISEG) recommendation has been implemented which requests that an evaluation independent of the original designers and startup engineers be performed to reduce unwanted GTS initiations. The focus of this evaluation shall be to enhance GTS auto initiation logic to reduce unnecessary challenges to the GTS from the ,
Radiation Monitoring System (RMS) and the HVR. Modifications and/or j procedure changes shall be made as determined by this independent evaluation.
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00 06 oF 08 TLKT 15 moor enece e soeuved. use addrogvmet kMC $w JEGCol Oh V. ADDITIONAL INFORMATION Identification of Cogonents Referred to in this LER IEEE 803 IEEE 805 Component EIIS Funct System ID Standby Gas Treatment System N/A BH Emergency Recirculation Subsystem N/A VA Reactor Building Ventilation System N/A VA exhaust fans FAN VA supply fans FAN VA Flow Switch FIS VA Dagers DMP YA Relay RLY VA There have been three previous similar GTS initiations due to operators trying to return HVR back to nonnal operation with an emergency recirculation fan running.
Detail of these similar events may be found in LERs 86-12 and 87-36 for Nine Mile Point Unit 2.
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August 28, 1987 United States Nuclear Regulatory Comission Document Control Desk
- Washington, DC 20555 RE
- Docket No. 50-410 LER 87-45 rAntlemen:
In accordance with 10 CFR 50.73, we hereby submit the following Licensee Event Report:
LER 87-45 Is (a)being(submitted (2) iv), "Any eventin accordance with 10 or condition thatCFR 50.73in manual resulted or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS).
However, actuation of an ESF, including the RPS, that resulted from and was part of the preplanned sequence during testing or reactor operation need not be reported."
A 10 CFR 50.72 report was made at 1350 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.13675e-4 months <br /> on July 29, 1987.
This report was conpleted in the format designated in NUREG-1022 Supplement No. 2, dated September 1985.
Very truly yours,
, 9 ~4 m Thomas E. Lempges l Vice President !
Nuclear Generation I l
TEL/CDS/mjd I Attachme nts f
l cc: Regional Administrator, Region 1 i Sr. Resident Inspector, W. A. Cook
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