05000388/LER-2012-001, For Susquehanna, Unit 2, Regarding Two Control Room Floor Cooling Systems Inoperable
| ML12192A205 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  (NPF-022) |
| Issue date: | 07/09/2012 |
| From: | Helsel J Susquehanna |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| PLA-6882 LER 12-001-00 | |
| Download: ML12192A205 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3882012001R00 - NRC Website | |
text
. I I
I Jeffrey M. Helsel Nuclear Plant Manager PPL Susquehanna, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3510 Fax 570.542.1504 jmhelsel@pplweb.com I
I I
'~ \\***/,~
...... ~
ppl.~~~:
U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-388/2012-001-00 UNIT 2 LICENSE NO. NPF-22 PLA-6882 Docket No 50-388 Attached is Licensee Event Report (LER) 50-388/2012-001-00 submitted for the Susquehanna Unit 2 event in which two Control Room Floor Cooling Systems were inoperable. The duration of the event was approximately fifteen minutes and resulted in a condition that could have prevented the fulfillment of a safety function. This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D).
There were no actual consequences to the health and safety of the public as a result of this event.
latory commitments are associated with this LER.
(
_ ~;~
J KtYsei Attachment: LER 50-388/2012-001-00 Copy:
NRC Region I Mr. P. W. Finney, NRC Sr. Resident Inspector Mr. R. R. Janati, DEP/BRP Ms. C. J. Sanders, NRC Project Manager TM
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:1 0/31/2013 (10-2010)
, the NRC digits/characters for each block) may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Susquehanna Steam Electric Station Unit 2 05000388 1 OF3
- 4. TITLE Two Control Room Floor Cooling Systems Inoperable
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 05 11 2012 2012
- - 001
- - 00 07 DCj 2012 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §:(Check all that apply) 1 0 20.2201(b) 0 20.2203(a)(3)(i) 0 50. 73(a)(2)(i)(C) 0 50. 73(a)(2)(vii) 0 20.2201 (d) 0 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(A)
D 50. 73(a)(2)(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4)
D 50.73(a)(2)(ii)(B) 0 50. 73(a)(2)(viii)(B)
- 10. POWER LEVEL 0 20.2203(a)(2)(i) 0 50.36(c)(1 )(i)(A) 0 50. 73(a)(2)(iii) 0 50. 73(a)(2)(ix)(A) 100%
0 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) 0 50. 73(a)(2)(iv)(A) 0 50. 73(a)(2)(x) 0 20.2203(a)(2)(iii) 0 50.36(c)(2)
D 50. 73(a)(2)(v)(A)
D 73.71 (a)(4) 0 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(5) 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50. 73(a)(2)(v)(C) 0 OTHER 0 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
~ 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME
~ELEPHONE NUMER (Include Area Code)
D. L. Filchner, Senior Engineer-Nuclear Regulatory Affairs (610) 774-7819
- 13. COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR
~ YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
D NO SUBMISSION 10 19 2012 DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On 5/11/12 at 1603 hours0.0186 days <br />0.445 hours <br />0.00265 weeks <br />6.099415e-4 months <br />, Unit 2 entered LCO 3.0.3 due to two control room floor cooling systems being inoperable. OV117A Control Room Floor Cooling Unit fan's discharge damper failed earlier during the same day at 0523 hours0.00605 days <br />0.145 hours <br />8.647487e-4 weeks <br />1.990015e-4 months <br />, rendering the associated OV117A fan inoperable. The redundant 'B' train ans and associated Control Structure Chiller automatically started as a result of a fan low flow interlock. The control switch for the 'A' train logic was left in
'Start' and the control switch for the 'B' train logic was left in 'Auto' as directed by the alarm response procedure. During application of a clearance order lfor repair of the failed OV117 A fan damper, the 'A' control room cooling fan switch was placed in 'Stop' position. This resulted in an automatic start of the
'A' Control Structure Chiller and all the associated 'A' fans except for the control room cooling fan, and a shutdown of the 'B' train fans and chiller. This condition caused the loss of both control room cooling fans and LCO 3.7.3 "Control Room Emergency Outside Air Supply (CREOAS) System,"
ConditionE; LCO 3.7.4 "Control Room Floor Cooling System," Condition D; LCO 3.0.3; and TRO 3.7.9 "Control Structure HVAC," were entered at 16: 03 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The control room operators immediately recognized the loss of cooling and took manual action to restart the 'B' train. LCO 3.0.3 was exited at 16:18 hours without a reactor power reduction. This event is reportable as a loss of entire safety function under 10CFR50.73(a)(2)(v)(D).
!The direct cause of this event was that the fan failure and the subsequent removal from service for repair, combined with the alignment of control switches ifor the equipment that auto started was not considered in the Alarm Response for Control Room Cooling fan failure or Off Normal Procedure for Loss of Control Structure Chilled Water. Operators were not procedurally directed to place the running equipment in a lead configuration. This resulted in knowledge based decisions that culminated in the loss of both Control Room cooling fans and resulted in the Unit 2 entering LCO 3.0.3.
Immediate corrective actions were taken to modify alarm response procedures.
Susquehanna Unit 1 was in Mode 5 at the time of the event and therefore unaffected because the associated Unit 1 Technical Specifications were not applicable.
The root cause, safety significance, and corrective actions will be provided in a supplement to this LER upon completion of the Root Cause Evaluation.
NRC FORM 366 (10-2010)
CONDITION PRIOR TO THE EVENT Unit 2-Mode 1, 100 percent Rated Thermal Power EVENT DESCRIPTION AND TIMELINE A chronological timeline or sequence of events leading up to and immediately following the event follows:
- 3. PAGE 20F3 On 05/11/2012 at 0523 hour0.00605 days <br />0.145 hours <br />8.647487e-4 weeks <br />1.990015e-4 months <br />s-control room personnel noted a change in Control Room HVAC background noise and found the OV117 A Control Room Floor Cooling Unit fan's discharge damper (HD-07831A) closed. Subsequently the
'A' train of CS HVAC (chiller and fans) shutdown on "OV117A low flow." Control Room personnel entered off normal procedure ON-030-001 "Loss of Control Structure Chilled Water." The 'B' train of CS HVAC (chiller and fans) automatically started following the shutdown of the 'A' train of CS HVAC.
LCO 3.7.3, LCO 3.7.4, TRO 3.7.9, and TRO 3.8.6 were entered for 'A' Control Room Cooling Inoperable due to failed fan discharge damper HD-07831A. A Condition Report was generated to document the issue and support repairs.
On 05/11/2012 at 1603 hour0.0186 days <br />0.445 hours <br />0.00265 weeks <br />6.099415e-4 months <br />s-during application of the clearance order for the damper repair work, when the fan hand switch HS-07831A was placed in "Stop," the low flow alarm logic fault for OV117A was bypassed. As a result, the OK112A Control Structure Chiller started and fans OV113A & OV115A started because OP162A, the chilled water loop pump control switch, had been left in the "Start" position from the previous trip while the loss of the OV117 A was still being investigated. Since the 'B' Chiller controls were left in 'AUTO,' the 'B' train of CS HVAC (chiller and fans) shutdown when the 'A' system re-started.
Off Normal Procedure ON-030-001 "Loss of Control Structure Chilled Water" was entered when Control Room Floor Cooling Unit Fan hand switch HS-07831A was placed to "Stop" to support repairs. This condition caused a loss of both Control Room Fans OV117A and OV117B. LCO 3.7.3, LCO 3.7.4, and subsequently LCO 3.0.3 were entered due to the loss of OV117 A and OV117B.
On 05/11/2012 at 1612 hour0.0187 days <br />0.448 hours <br />0.00267 weeks <br />6.13366e-4 months <br />s-the 'B' train of CS HVAC (chiller and fans) was started in accordance with the operating procedures to restore Control Room Cooling.
On 05/11/2012 at 1615 hour0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br />s-the 'A' Control Structure Chiller OK112A was placed in standby.
At 1618 hours0.0187 days <br />0.449 hours <br />0.00268 weeks <br />6.15649e-4 months <br /> LCO 3.0.3 was exited.
On 05/11/2012 at 2127 hour0.0246 days <br />0.591 hours <br />0.00352 weeks <br />8.093235e-4 months <br />s-an ENS notification (47919) was made to the NRC in accordance with 10 CFR 50.72(b)(3)(v) & (vi) for an event that could have prevented the fulfillment of a safety function. As such, this event is being submitted in accordance with 1 OCFR50. 73(a)(2)(v)(D) as a loss of entire safety function.
CAUSE OF THE EVENT
The direct cause was that the fan failure and the subsequent need to take it out of service for repair, combined with the alignment of control switches for the equipment that auto started was not considered in the Alarm Response for Control Room Cooling fan failure or Off Normal Procedure for Loss of Control Structure Chilled Water. Operators were not directed procedurally to place the running equipment in a lead configuration; this resulted in knowledge based decisions that culminated in the loss of both Control Room cooling fans and resulted in the Unit 2 entering LCO 3.0.3. Procedures were deficient to ensure a successful outcome. (10-2010)
U.S. NUCLEAR REGULATORY COMMISSION
- 1. FACILITY NAME LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 2. DOCKET
- 6. LER NUMBER Susquehanna Steam Electric Station Unit 2 05000388 YEAR I
SEQUENTIAL I REVISION NUMBER NUMBER 2012
- - 001-
- - 00
- 3. PAGE 30F3 Control room personnel did not anticipate that placement of the OV117A Control Room Floor Cooling Unit Fan hand switch to 'Stop' would cause the 'B' train of CS HVAC (chiller and fans) to shutdown. A step in the operating procedure OP-030-001 "Control Structure Chilled Water System" to align the chiller that auto started as the lead, (in service) chiller, was not required by procedure to be completed prior to placing the OV117A Control Room Floor Cooling Unit Fan hand switch to 'Stop' for repairs. Additionally, the sequence of blocking applied by the Clearance Order did not take the chiller control logic into account.
Upon completion of the root cause evaluation for this event, the root cause will be provided in a supplement to this LER.
ANALYSIS/SAFETY SIGNIFICANCE
Actual Consequences:
There are no actual safety consequences as a result of this event due to its short duration.
Potential Consequences:
The Control Room Floor Cooling System is capable of removing sensible and latent heat loads from the control room, including consideration of equipment heat loads and personnel occupancy requirements to ensure equipment operability. The system is designed for 30 day continuous occupancy and the control room cooling fans are also needed for pressure control of the habitability envelope. A loss of the Control Room Floor Cooling System for an extended period has the potential to affect these requirements.
Upon completion of the root cause evaluation, the actual safety significance and any potential consequences will be included in a supplement to this LER.
CORRECTIVE ACTIONS
An immediate corrective action was to revise alarm response procedures to include direction to place the running control structure chiller to a "start" configuration when it is decided to maintain that configuration.
Additional corrective actions determined during completion of the root cause evaluation will be included in a supplement to this LER.
PREVIOUS SIMILAR EVENTS
The following LER's were recently submitted related to Control Structure Cooling issues:
LER 387/2012-01-00, "Both Control Structure Chillers Inoperable" identified a condition that could have prevented the fulfillment of a safety function associated with the CS Chillers.
LER 387/2012-002-00, "8 Control Structure Chiller Inoperable Concurrent with "A" Emergency Diesel Generator Out of Service" identified a condition that could have prevented the fulfillment of a safety function associated with the CS Chillers.