ML17353A445
| ML17353A445 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 11/09/1995 |
| From: | Knorr J, Plunkett T FLORIDA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| L-95-283, LER-95-007-01, LER-95-7-1, NUDOCS 9511210125 | |
| Download: ML17353A445 (20) | |
Text
RIC) RIWY PACCELERATED Rl DS P ROC ESSIVE G)
REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9511210125 DOC-DATE: 95/11/09 NOTARIZED: NO DOCKET N FACIL:50-250 Turkey Point Plant, Unit 3, Florida Power and Light C 05000250 AUTH. NAME AUTHOR AFFILIATION KNORR,J.E. Florida Power & Light Co.
PLUNKETT,T.F. Florida Power & Light Co.
RECIP.NAME RECIPIENT AFFILIATION
SUBJECT:
LER 95-007-00:on 951017,manual RT occurred following drop of four control rods. Caused by water intrusion into rod control power cabinet 2BD.Inspected control power cabinet 2BD for other water damage.W/951109 ltr.
DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:
TITLE: 50.73/50.9 Licensee Event Report (LER), nciden Rpt, etc.
NOTES:
RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-1 PD 1 1 CROTEAU,R 1 1 INTERNAL: A ~D/RAB 2 2 AEOD/SPD/RRAB 1 1 ILE CRH~ 1 1 NRR/DE/ECGB 1 1 7DRQREKs 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB .1 1 NRR/DRCH/HQMB 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 RES/DSIR/EIB 1 1 RGN2'ILE 01 1 1 EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCE,J H 2 2 NOAC MURPHY,G.A 1 1 NOAC POORE,W. 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 iNOTE TO ALL"RIDS" RECIPI EYTS:
PLEASE HELP US TO REDUCE iVASTE! CONTACT THE DOCL'MEYTCONTROL DESK, ROOM P!.37 (EXT. 504.2083 ) TO ELI),IIiATEVOL'R NAME FROil DISTRIDUTIOYLISTS I:OR DOCL'NIEi'I'S YOU DOY"I'EED!
FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25
MOV08 l995 I,95-283 10 CFR 550.73 U S Nuclear Regulatory Comma.ssz.on Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:
Re: Turkey Point Unit 3 Docket No. 50-250 Reportable Event: 95-007-00 The attached Licensee Event Report, 250/95-007-00, is being provided in accordance with 10 CFR 50.73(a) (2) (iv) .
If there are any questions, please contact us.
Very truly yours, g.g(.3-~
T. F. Plunkett Vice President Turkey Point Plant JEK attachment CC: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Thomas P. Johnson, Senior Resident Inspector, USNRC, Turkey Point Plant
<~ U
'rr511210125 'rr51109 PDR ADOCK 05000250 S PDR an FPL Group company
LICENSEE EVENT REPORT LER FACILITY NAME (1)
DOCKET NUMBER (2) PAGE (3)
TURKEY POINT UNIT 3 05000250 OF 7
TITLE Manual Reactor Tri Followin Dro of Four Control Rods EVENT DATE 5 LER NUMBER 6 RPT DATE 7 OTHER FACILITIES INV. 8 MON DAY YR YR SE 4 Rt MON DAY YR FACILITY NAMES DOCKET 4 S 10 17 95 95 007 00 11 09 95 OPERATING MODE (9)
POWER LEVEL (10) 100 LICENSEE CONTACT FOR THIS LER 12 TEIEPHONE NUMBER J. E. Knorr, Regulation and Compliance Specialist 305-246-6757 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 13 CAUSE SYSTEM COMPONENT MANUFACTURER NPRDS2 CAUSE SYSTEM COMPONENT MANUFACTURER NPRDS2 SUPPLEMENTAL REPORT EXPECTED (14) NO YES 0 EXPECTED SUBMISSION DATE (15)
MONTH DAY (lf yosi cmnploto EXPECTED SUBMISSION DATE)
ABSTRACT (16)
On October 17, 1995, Florida Power & Light Company's Turkey Point Unit 3 was operating in Mode 1 at 100% power.
At 0449 hours0.0052 days <br />0.125 hours <br />7.423942e-4 weeks <br />1.708445e-4 months <br /> a Rod Control Urgent Failure alarm was received along with indication of 4 dropped control rods. The reactor was manually tripped twenty-two seconds later. Off Normal Operating Procedure 3-0NOP-028.3, "Dropped RCC," requires the reactor to be tripped rods drop into the core.
if more than two control The cause of the dropped rods was water intrusion into rod control power cabinet 2BD. The design of the drain in an air conditioner evaporator drip pan was found to be inadequate for the level of humidity in the cable spreading room.
The NRC operations center was notified at 0553 in accordance with 10 CFR 550.72(b) (2) (ii), Reactor Protection System Actuation.
LICENSEE ANT REPORT (LER) TEXT aNTINUATION FACILITY NAME TURKEY POINT UNIT 3 DOCKET NUMBER 05000250
'ER NUMBER 95-007-00 PAGE NO.
2OF7 I. DESCRIPTION OF THE EVENT On October 17, 1995, Florida Power & Light Company's (FPL) Turkey Point Unit 3 was operating in Mode 1 at 100% power.
At 0449 hours0.0052 days <br />0.125 hours <br />7.423942e-4 weeks <br />1.708445e-4 months <br /> a Rod Control Urgent Failure alarm [AA:JA] was received along with indication of 4 dropped control rods
[AA:ROD]. The reactor was manually tripped twenty-two seconds later. Off Normal Operating Procedure 3-0NOP-028.3, "Dropped RCC," requires the reactor to be tripped rods drop into the core.
if more than two control The NRC operations center was notified at 0553 in accordance with 10 CFR 550.72(b) (2) (ii), Reactor Protection System Actuation.
II. SYSTEM DESCRIPTION Group 2 of Control Bank B (4 of 8 rods in Control Bank B) dropped into the core, which by procedure requires a manual trip.
Control Bank B control circuit cards [AA:LCO] are contained in control power cabinet 2BD [AA:CAB] in the 3B motor control center (MCC) room on the 18 ft. elevation. Control power cabinet 2BD contains the control cards for the stationary coils [AA:CL] for Control Banks B and D and the control cards for the movable coils of Control Banks B and D. Other cards are also present in this control power cabinet but were not affected by the water intrusion. The stationary coil cards are specific to groups.
The movable coil cards are multiplexed such that more than one group is controlled by each card. Immediately above the 2BD control power cabinet is the cable spreading room floor. Both the cable spreading room and the Unit 3 MCC are air conditioned.
The drain pan for the evaporator coil for the cable spreading room air conditioning unit is immediately below the air conditioning unit with a drain running to a nearby standpipe.
III. CAUSE OF THE EVENT The root cause of the rod drop was a very small amount of water dropping onto the control cards which fed the stationary coils for the group 2 rods of Control Bank B. Due to the water on the stationary coil card, the 4 group 2 rods for Control Bank B dropped.
On October 16, 1995, at 16:29 an inadvertent automatic fire suppression system (Halon) [KQ:] actuation occurred in the cable spreading room. This occurred while restoring the Halon system after testing of the fire detection system [IC:] in vendor an area near the cable spreading room. After the actuation, the was called to aid in the determination of the cause of the actuation.
After extensive investigation by FPL and vendor personnel the cause is believed to be a voltage spike during system restoration. The spike could not be duplicated. The vendor also
LICENSEE ANT REPORT (LER) TEXT INTINUATZON FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 3OF7 determined as part of the investigation that the second of two Halon. bottles [KQ:] had not discharged and could possibly discharge at any time. As a result of the potential for the second bottle to discharge, Turkey Point personnel restricted access to the cable spreading room and left the doors open for ventilation of the room. The increased humidity in the room due to the open doors was condensed into a drain pan [VI:DRN] under the cooling coils of the air conditioning unit [VI:AHU] in the north west corner of the cable spreading room. The drip pan drain is sized for humidity levels with the door closed. With the door open, humidity levels rose causing condensed water to overflow onto the floor of the cable spreading room. Unknown to plant personnel, the water began to puddle on the cable spreading room floor and flowed to an area with support base plates held down with concrete anchor bolts. Due. to the depth of the anchor bolt hole, water from the cable spreading room migrated through a bottom patched anchor hole and dripped onto the top of control power cabinet 2BD in the MCC below. Some of the water collected on top of the 2BD control power cabinet and dripped onto the control cards within the cabinet, resulting in the dropped control rods.
f Additional investigation of the reason for the discharge of only one of two Halon bottles during the inadvertent actuation of the automatic suppression system, resulted in discovery of a check valve installed backwards. This check valve had been installed during the original installation of the Halon automatic discharge system in 1986. The remaining check valves installed on the primary and backup.Halon bottles were visually inspected and found to be installed correctly. The incorrectly installed check valve has been corrected and verified.
IV. ANALYSIS OF THE EVENT Rod Cluster Control Assembly (RCCA) Drop is a UFSAR analyzed accident. The dropped rod event is a Condition II event that is assumed to be initiated by a single electrical or mechanical failure which causes any number and combinatio'n of rods from the same group of a given bank to fall to the bottom of the core.
The resulting negative reactivity insertion causes nuclear power to decrease rapidly. An increase in the hot channel factor may occur due to the skewed power distribution representative of a dropped rod configuration. In this case the rod drop was symmetrical. Since this is a Condition II event, the analysis must show that the departure from nucleate boiling design basis is met for the combination of power, hot channel factor, and other system conditions which exist following the dropped rod.
The analysis for the Unit 3 Cycle 15 core design, assuming no turbine runback, verified that the departure from nucleate boiling ratio remains above the limit value for both core. the standard and optimized fuel designs which are present in the
LICENSEE ENT REPORT (LER) TEXT ONTINUATION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 4 OF 7 The alternate shutdown panel and associated procedures which would be used to shutdown the plant after a fire in the cable spreading room or control room do not take credit for any cabling within the cable spreading room. The suppression system is present in the cable spreading room due to a requirement of 10 alternate shutdown capability is still operable with Therefore, CFR 50 Appendix R.
a fire in the cable spreading room.
The Halon automatic suppression system for the cable spreading room consists of two 433 pound bottles of Halon with a manual transfer switch to two identical reserve bottles.
Due to the reverse orientation of a check valve on one of the primary Halon bottles, an analysis of the remaining capability of the single main Halon bottle for the cable spreading room has
-been performed. The 433 pounds of Halon available would have resulted in a Halon concentration of 3.3% in the cable spreading room for 30 minutes. While National Fire Protection Association (NFPA) 12A recommends a minimum design for flame extinguishment of 5%, actual cup burner tests on flammable liquids demonstrate flame extinguishment at concentrations between 3 and 4%. Flame extinguishment is provided by concentrations less than 3.3% for acetone, benzene, and methane.
In the event that a fire occurred, alarms in the control room would cause an investigation by operations. Upon confirmation by an operator that a .fire is present, the fire brigade would be mobilized. The smoke detection system is such that a single detector would be expected to alarm, resulting in operator investigation, prior to two alarms being received which would result in Halon actuation. Review of Off Normal Operating Procedure O-ONOP-16.8, "Response to a Fire/Smoke Detection System Alarm," indicates that if an alarm was received from the cable spreading room, the Halon system would be checked for actuation.
Notes in the ONOP indicate that the alarm should be cleared at the local alarm panel prior to transferring automatic Halon operation to the reserve bank to avoid inadvertent actuation.
The actions specified in O-ONOP-016.8 are expected to be performed by the operator on the scene prior to the arrival of the fire brigade. The fire brigade would be involved in reviewing the situation and assessing appropriate pre-established fire fighting strategies. If deemed appropriate, the fire of his brigade leader is provided with the option, as part training, of actuating the reserve Halon bank for the cable spreading room. The actuation of the reserve system is accomplished from outside the cable spreading room. In this event the reserve bank would have actuated as designed, if activated by the fire brigade with the original actuation signal still applied to the Halon system. The check valves in the reserve bank were inspected and found to be installed correctly.
Concurrent with these actions, if incorrect the fire were considered severe operation of control room enough, based on smoke or
. equipment, a decision could be made to evacuate the control room
LICENSEE ANT REPORT (LER) TEXT CONTINUATION FACILITY NAME DOCKET NUMBER -LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 5OF7 and commence proceduralized plant shutdown from the alternate shutdown panel. These actions are entirely independent of and do not rely upon cable spreading room suppression system operation,.
Note that the potential for a fire being initiated in the cable spreading room is considered quite low. Transient combustibles must be monitored at all times in this area as required by plant procedures. Procedures 'require permits for transient chemical combustibles in the cable spreading room;, above 1 gallon being strictly monitored and maintained in approved containers.
Likewise, flame retardant wood in excess of 100 pounds in this area would require a permit. Review of fire protection records indicates that no permits have been issued for the cable spreading room. Accordingly, any transient combustible would be less than 1 gallon and would be under strict control.
The loss of the use of one of two bottles of Halon from the main bank would result in partial loss of fire suppression capability.
However, the remaining bottle can be expected to prevent the propagation of a fire to some extent. The calculated Core Damage Frequency (CDF) for the cable spreading room is 2.8E-6 per reactor year. This analysis, using the FIVE methodology and equations, assumed the following:
The fire ignition frequency for cable spreading room =
7.8E-3/Yr The failure probability of Auxiliary Shutdown Panel (ASP) failure = 0.1 The failure probability of automatic Halon suppression 0.05 The failure probability of manual suppression = 1 For the circumstances which occurred, given that one bottle of the cable spreading room Halon system is out of service, the failure of Halon suppression would be increased to 0.5. A failure probability of 0.5 is reasonable compared to a failure probability of 1.0, since the main Halon system is partially operable and is expected to prevent the fire from propagating compared to the case where there is a total loss of the Halon system. This makes the possibility of taking manual action to initiate suppression more likely, thus a manual suppression failure probability of 0.2 is considered in this case. Keeping the ignition frequency and failure of the ASP failure as 7.8E-3/Yr and 0.1 respectively, would result in the CDF of 5.61E-6 per reactor year. The increased risk associated with this event is concluded to be small.
The following general conclusions can be made regarding this incorrectly installed configuration concern:
- 1. While the cable spreading room Halon system was degraded, it maintained some level of functionality in
LXCENSEE 4kNT REPORT (LER) TEXT NTINUATXON FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 6OF7 that it would have extinguished flames for certain types of chemicals. The degraded installation would i.nhibit the propagation of fires for most chemical substances (i.e., may "stall" the fire) . This would
~
provide additional time for the plant to respond and fight the fire.
- 2. The reserve system was fully functional. In the event of a significant fire, the fire brigade leader would have the option of discharging the reserve system, and thus extinguishing any fires.
- 3. The likelihood of a cable spreading room fire is low, and is shown above to be not risk significant.
V. CORRECTIVE ACTIONS Control power cabinet 2BD has been inspected for other water damage and appropriate testing has been completed to assure the operability of the control cards in the power cabinet.
Other cabinets in the area have been inspected to assure no other water intrusion has occurred.
- 2. The drain design of the air conditioner evaporator drip pan in the cable spreading room has been evaluated for flow .
capability. The size, routing and material used for the drain will be modified, if appropriate, to reduce the probability of an overflow. Other air conditioning evaporator drip pan drainage systems have been inspected for proper operation. Adequate drainage was found.
- 3. The anchor pads in the cable spreading room in the area that puddled during the event have been caulked to prevent a water path to the bolt holes beneath.
4 ~ The conduit penetration through the top of control power cabinet 2BD has also been caulked.
- 5. Proper installation of all check valves in the Turkey Point Halon automatic suppression systems has been visually verified.
Appropriate fire watches were posted while the Halon system was in a degraded configuration.
- 7. The Halon suppression system for the cable spreading room was returned to full service on October 24, 1995.
- 8. Electrical Maintenance Surveillance Procedure O-SME-091.1, "Fire and Smoke Detection System Semi-Annual Test," and Operating Procedure O-OP-016.5, "Halon Suppression System,"
have been revised to provide for a different removal-from-service technique to reduce the probability of spurious actuation of the automatic suppression system.
LICENSEE ANT REPORT (LER) TEXT O)NTINURTION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 7 OF 7 VI. ADDITIONAL INFORMATION EIIS Codes are shown in the format [EIIS SYSTEM: IEEE component function identifier, second component function identifier (if appropriate)).
NOV I) g 1ggg L-95-283 10 CFR 550 . 73 U. S ~ Nuclear Regu 1 atory Commission Attn: Document Contro 1 Desk Washington, D. C. 20555 Gentlemen: .
Re: Turkey Point Unit 3 Docket No . 50-250 Reportable Event: 95-007-00 The attached Licensee Event Report, 250/95-007-00, is being provided in accordance with 10 CFR 50 . 73 (a) (2) (iv) .
If there're any questions, please contact us .
Very truly yours, T. F ~ P lunkett Vice President Turkey Point Plant JEK attachment CC: Stewart USNRC D. Ebneter, Regional Administrator, Region II, Thomas P . Johnson, Senior Resident Inspector, USNRC, Turkey Point Plant all1 FPL Group colllpalllg
LICENSEE EVENT REPORT LER FACII ITY NA ME II) DOCKET NUMBER I2) PACE (3)
TURKEY POINT UNIT 3 05000250 oF 7 ITLE Manual Reactor Trio Fol lowincr DroI3 of Four Control Rods EVENT DATE 5 LER NUMBER 6) RPT DATE 2 OTHER FACILI r S INV 8 MON DAY YR YR SE I R) MON DAY YR FACIL ITY NAMES DOC K ET 4 S 10 17 95 95 007 00 11 09 95 OPERATING MODE (9)
POWER LEVEL (10) 100 LICENSEE CONTACT FOR THIS LER (12)
TELEPHONE NUMBER J. E. Knorr, Regulation and Compliance Specialist 305-246-6757 COMPLETE ONE LINE FOR EACH COMPONEN. FAILURE DESCRIBED IN THIS REPORT 13 CAUSE SYSTEM COMPONENT MANUFACTURER NPRDS2 CAUSE SYSTEM COMPONE¹ MANUFACTURER NPRDS2 SUPPLEME ITAL REPORT EXPECTED {14) NO YES 0 EXPECiED SUBMISSION DATE (16)
MONTH DAY Ill yes, coaplece EXPECTED SUBMISSION DATE)
ABSTRAC i (16)
On October 17, 1995, Florida Power & Light Company's Turkey Point Unit 3 was operating in Mode 1 at 100% power.
At 0449 hours0.0052 days <br />0.125 hours <br />7.423942e-4 weeks <br />1.708445e-4 months <br /> a Rod Control Urgent Failure alarm was received along with indication of 4 dropped control rods. The reactor was manually tripped twenty-two seconds later; Off Normal Operating Procedure 3-ONOP-028.3, "Dropped RCC," requires the reactor to be tripped rods drop into the core.
if more than two control The cause of the dropped rods was water intrusion into rod control power cabinet 2BD. The design of the drain in an air conditioner evaporator drip pan was found to be inadequate for the level of humidity in the cable spreading room.
The NRC operations center was notified at 0553 in accordance with 10 CFR 550.72(b) (2) (ii), Reactor Protection System Actuation.
LICENSEE SENT REPORT (LER) TEXXOONTINUATION FACZLZTY NAME DOCKET NUMBER LER NUMBER PAGE NO, TURKEY POZNT UNZT 3 05000250 95-007-00 ,2 OF 7 I. DESCRIPTION OF THE EVENT On October 17, 1995, Florida Power & Light Company's (FPL) Turkey Point Unit 3 was operating in Mode 1 at 100% power.
At 0449 hours0.0052 days <br />0.125 hours <br />7.423942e-4 weeks <br />1.708445e-4 months <br /> a Rod Control Urgent Failure alarm [AA:JA] was received along with indication of 4 dropped control rods
[AA:ROD). The reactor was manually tripped twenty-two seconds later. Off Normal Operating Procedure 3-ONOP-028.3, "Dropped RCC," requires the reactor to be tripped rods drop into the core.
if more than two control The NRC operations center was notified at 0553 in accordance with 10 CFR 550.72(b) (2) (ii), Reactor Protection System Actuation.
II. SYSTEM DESCRIPTION Group 2 of Control Bank B (4 of 8 rods in Control Bank B) dropped into the core, which by procedure requires a manual trip.
Control Bank B control circuit cards [AA:LCO) are contained in control power cabinet 2BD [AA:CAB] in the 3B motor control center (MCC) room on the 18 ft. elevation. Control power cabinet 2BD contains the control cards for the stationary coils [AA:CL) for Control Banks B and D and the control cards for the movable coils of Control Banks B and D. Other cards are also present in this control power cabinet but were not affected by the water intrusion. The stationary coil cards are specific to groups.
The movable coil cards are multiplexed such that more than one group is controlled by each card. Immediately above the 2BD control power cabinet is the cable spreading room floor. Both the cable spreading- room and the Unit 3 MCC are air conditioned.
The drain pan for the evaporator coil for the cable spreading room air conditioning unit is immediately below the air conditioning unit with a drain running to a nearby standpipe.
III. CAUSE OF THE EVENT The root cause of the rod drop was a very small amount of water dropping onto the control cards which fed the stationary coils for the group 2 rods of Control Bank B. Due to the water on the stationary coil card, the 4 group 2 rods for Control Bank B dropped.
On October 16, 1995, at 16:29 an inadvertent automatic fire suppression system (Halon) [KQ:] actuation occurred in the cable spreading room. This occurred while restoring the Halon system after testing of the fire detection system [IC:] in an area near the cable spreading room. After the actuation, the vendor was called to aid in the determination of the cause of the actuation.
After extensive investigation by FPL and vendor personnel the cause is believed to be a voltage spike during system restoration. The spike could not be duplicated. The vendor also
LICENSEE ENT REPORT (LER) TEXT)NTINUATION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNXT 3 05000250 95-007-00 3 OF 7 determined as part of the investigation that the second of two Halon bottles [KQ:] had not discharged and could possibly discharge at any time. As a result of the potential for the second bottle to discharge, Turkey Point personnel restricted access to the cable spreading room and left the doors open for ventilation of the room. The increased humidity in the room due to the open doors was condensed into a drain pan [VI:DRN] under the cooling coils of the air conditioning unit [VI:AHU] in the north west corner of the cable spreading room. The drip pan drain is sized for humidity levels with the door closed. With the door open, humidity levels rose causing condensed water to overflow onto the floor of the cable spreading room. Unknown to plant personnel, the water began to puddle on the cable spreading room floor and flowed to an area with support base plates held down with concrete anchor bolts. Due to the depth of the anchor
'bolt hole, water from the cable spreading room migrated through a bottom patched anchor hole and dripped onto the top of control power cabinet 2BD in the MCC below. Some of the water collected on top of the 2BD control power cabinet and dripped onto the control cards within the cabinet, resulting in the dropped control rods.
Additional investigation of the reason for the discharge of only one of two Halon bottles during the inadvertent actuation of the automatic suppression system, resulted in discovery of a check valve installed backwards. This check valve had been installed during the original installation of the Halon automatic discharge system in 1986. The remaining check valves installed on the primary and backup Halon bottles were visually inspected and found to be installed correctly. The incorrectly installed check valve has been corrected and verified.
IV. ANALYSIS OF THE EVENT Rod Cluster Control Assembly (RCCA) Drop is a UFSAR analyzed accident. The dropped rod event is a Condition II event that is assumed to be initiated by a single electrical or mechanical failure which causes any number and combination of rods from the same group of a given bank to fall to the bottom of the core.
The resulting negative reactivity insertion causes nuclear po~er to decrease rapidly. An increase in the hot channel factor may occur due to the skewed power distribution representative of a dropped rod configuration. In this case the rod drop was symmetrical. Since this is a Condition II event, the analysis must show that the departure from nucleate boiling design basis is met for the combination of power, hot channel factor, and other system conditions which exist following the dropped rod.
The analysis for the Unit 3 Cycle '15 core design, assuming no turbine runback, verified that the departure from nucleate boiling ratio xemains above the limit value fox both the standard and optimized fuel designs which are present in the core.
LICENSEE SENT REPORT (LER) TEXTOONTINUATION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 4 OF 7 The alternate shutdown panel and associated procedures which would be used to sou't'down 'the plant after a fire in the cable spreading room or control room do not take credit for any cabling within the cable spreading room. The suppression system is present in the cable spreading room due to a requirement of 10 alternate shutdown capability is still operable with Therefore, CFR 50 Appendix R.
a fire in the cable spreading room.
The Halon automatic suppression system for the cable spreading room consists of two 433 pound bottles of Halon with a manual transfer switch to two identical reserve bottles.
Due to the reverse orientation of a check valve on one of the primary Halon bottles, an analysis of the remaining capability of the single main Halon bottle for the cable spreading room has been performed. The 433 pounds of Halon available would have resulted in a Halon concentration of 3.3% in the cable spreading room for 30 minutes. While National Fire Protection Association (NFPA) 12A recommends a minimum design for flame extinguishment of 5%, actual cup burner tests on flammable liquids demonstrate flame extinguishment at concentrations between 3 and 4%. Flame extinguishment is provided by concentrations less than 3.3% for acetone, benzene, and methane.
In the event that a fire occurred, alarms in the control room would cause an investigation by operations. Upon confirmation by an operator that a fire is present, the fire brigade would be mobilized. The smoke detection system is such that a single detector would be expected to alarm, resulting in operator investigation, prior to two alarms being received which would result in Halon actuation. Review of Off Normal Operating Procedure O-ONOP-16.8, "Response to a Fire/Smoke Detection System Alarm," indicates that if an alarm was received from the cable spreading room, the Halon system would be checked for actuation.
Notes in the ONOP indicate that the alarm should be cleared at the local alarm panel prior to transferring automatic Halon operation to the reserve bank to avoid inadvertent actuation.
The actions specified in O-ONOP-016.8 are expected to be performed by the operator on the scene prior to the arrival of the fire brigade. The fire brigade would be involved in reviewing the situation and assessing appropriate pre-established fire fighting strategies. If deemed appropriate, the fire brigade leader is provided with the option, as part of his training, of actuating the reserve Halon bank for the cable spreading room. The actuation of the reserve system is accomplished from outside the cable spreading room. In this event the reserve bank would have actuated as designed, activated by the fire brigade with the original actuation signal if still applied wereto the Halon system. The check valves in the reserve bank inspected and found to be installed correctly.
Concurrent with these actions, if the fire were considered severe based on smoke or incorrect operation of control room
- enough, equipment, a decision could be made to evacuate the control room
LICENSEE IENT REPORT (LER) TEXT%)NTINUATION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POINT UNIT 3 05000250 95-007-00 50F7 and commence proceduralized plant shutdown from the alternate shutdown panel. These actions are entirely independent of and do not rely upon cable spreading room suppression system operation.
Note that the potential for a fire being initiated in the cable spreading room is considered quite low. Transient combustibles must be monitored at all times in this area as required by plant procedures. Procedures require permits for transient chemical combustibles in the cable spreading room; above 1 gallon being strictly monitored and maintained in approved containers.
Likewise, flame retardant wood in excess of 100 pounds in this area would require a permit. Review of fire protection records indicates that no permits have been issued for the cable spreading room. Accordingly, any transient combustible would be less than 1 gallon and would be under strict control.
The loss of the use of one of two bottles of Halon from the main bank would result in partial loss of fire suppression capability.
However, the remaining bottle can be expected to prevent the propagation of a fire to some extent. The calculated Core Damage Frequency (CDF) for the cable spreading room is 2.8E-6 per reactor year. This analysis, using the FlVE methodology and equations, assumed the following:
The fire ignition frequency for cable spreading room =
7.8E-3/Yr The failure probability of Auxiliary Shutdown Panel (ASP) failure = 0.1 The failure probability of automatic Halon suppression 0.05 The failure probability of manual suppression = 1 For the circumstances which occurred, given that one bottle of the cable spreading room Halon system is out of service, the failure of Halon suppression would be increased to 0.5. A failure probability of 0.5 is reasonable compared to a failure probability of 1.0, since the main Halon system is partially operable and is expected to prevent the fire from propagating compared to the case where there 's a total loss of the Halon system. This makes the possibility of taking manual action to initiate suppression more likely, thus a manual suppression failure probability of 0.2 is considered in this case. Keeping the ignition frequency and failure of the ASP failure as 7.8E-3/Yr and 0.1 respectively, would result in the CDF of 5.61E-6 per reactor year. The increased risk associated with this event is concluded to be small.
The following general conclusions can be made regarding this incorrectly installed configuration concern:
- 1. While the cable spreading room Halon system was degraded, it maintained some level of functionality in
LICENSEE kNT REPORT (LER) TEXT NTINUATION FACZLZTY NAME DOCKET NUMBER LER NUMBER PAGE NO.
TURKEY POZNT UNZT 3 05000250 95-007-00 6OF7 that it would have extinguished flames for certain types of chemicals. The degraded installation would inhibit the propagation of fires for most chemical substances (i:e.', may "stall" the fire) .- This would provide additional time for the plant to respond and fight the fire.
- 2. The reserve system was fully functional. In the event of a significant fire, the fire brigade leader would have the option of discharging the reserve system, and thus extinguishing any fires.
- 3. The likelihood of a cable spreading room fire is low, and is shown above to be not risk significant.
V. CORRECTIVE ACTIONS Control power cabinet 2BD has been inspected for other water damage and appropriate testing has been completed to assure the operability of the control cards in the power cabinet.
Other cabinets in the area have been inspected.to assure no other water intrusion has occurred.
- 2. The drain design of the air conditioner evaporator drip pan in the cable spreading room has been evaluated for flow capability. The size, routing and material used for the drain will be modified, if appropriate, to reduce the probability of an overflow. Other air conditioning evaporator drip pan drainage systems have been inspected for proper operation. Adequate drainage was found.
- 3. The anchor pads in the cable spreading room in the area that puddled during the event have been caulked to prevent a water path to the bolt holes beneath.
- 4. The conduit penetration through the top of control power cabinet 2BD has also been caulked.
- 5. Proper installation of all check valves in the Turkey Point Halon automatic suppression systems has been visually verified.
- 6. Appropriate fire watches were posted while the Halon system was in a degraded configuration.
- 7. The Halon suppression system for the cable spreading room was returned to full service on October 24, 1995.
- 8. Electrical Maintenance Surveillance Procedure O-SME-091.1, "Fire and Smoke Detection System Semi-Annual Test," and Operating Procedure O-OP-016.5, "Halon Suppression System,"
have been revised to provide for a different removal-from-service technique to reduce the probability of spurious actuation of the automatic suppression system.
LICENSEE SENT REPORT (LER) TEXTObNTINUATION I
FACZLZTY NAME DOCKET NUK3ER LER NUMBER PAGE NO.
TURKEY POZNT UNZT 3 05000250 95-007"00 7 OF 7 Vi. ADDITIONAL INFORMATION EIIS Codes are shown in the format [EIIS SYSTEM: IEEE component function identifier, second component function identifier (if appropriate)) .