05000529/LER-2011-001, For Palo Verde Unit 2, Irradiated Fuel Movement with Misaligned Control Room Essential Filtration System
| ML11168A060 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/07/2011 |
| From: | Mims D Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 102-06366-DCM/DCE LER 11-001-00 | |
| Download: ML11168A060 (9) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 5292011001R00 - NRC Website | |
text
10 CFR 50.73 LAM-A subsidiary of Pinnacle West Capital Corporation Palo Verde Nuclear Generating Station Dwight C. Mims Senior Vice President Nuclear Regulatory Affairs and Oversight Tel. 623-393-5403 Fax 623-393-6077 Mail Station 7605 P.O. Box 52034 Phoenix, Arizona 85072-2034 102-06366-DCM/DCE June 07, 2011 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS) Unit 2 Docket No. STN 50-529 License No. NPF-51 Licensee Event Report 2011-001-00 Enclosed please find Licensee Event Report (LER) 50-529/2011-001-00 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER reports a condition prohibited by Technical Specifications that occurred as a result of continued irradiated fuel movement while the Control Room air intake radiation monitors were inoperable with the Control Room Essential Filtration System not in the essential filtration mode required for post-accident emergency alignment.
In accordance with 10 CFR 50.4, copies of this LER are being forwarded to the Nuclear Regulatory Commission (NRC) Regional Office, NRC Region IV and the Senior Resident Inspector. If you have questions regarding this submittal, please contact Marianne Webb, Section Leader, Regulatory Affairs, at (623) 393-5730.
Arizona Public Service Company makes no commitments in this letter.
Sincerely, DCM/TNW/M NW/DCE/gat Enclosure cc:
E. E. Collins Jr.
L. K. Gibson J. R. Hall M. A. Brown NRC Region IV Regional Administrator NRC NRR Project Manager for PVNGS (electronic / paper)
NRC NRR Senior Project Manager (electronic / paper)
NRC Senior Resident Inspector for PVNGS A member of the STARS (Strategic Teaming and Resource Sharing) Alliance f
Callaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- San Onofre
- South Texas
- Wolf Creek
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Palo Verde Nuclear Generating Station (PVNGS) Unit 2 05000529 1 OF 8
- 4. TITLE Irradiated Fuel Movement with Misaligned Control Room Essential Filtration System
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FAITYNMDOKTUBE NUMBER NO.
_________ IFACILIT NAME DOCKET NUMBER 04 08 2011 2011 001 00 06 07 2011
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMI'TED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check al/that apply)
El 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) 6 El 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
[1 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
[] 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 0 El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
Z 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in Separate ductwork, exhaust fans, and exhaust dampers are provided for the kitchen and restroom facilities inside the Control Room ventilation envelope. The kitchen and restroom exhaust dampers close when actuated by CREFAS.
Upon actuation by a CREFAS, dampers close to isolate the Control Room normal AHU, the communication and inverter rooms and the Control Room kitchen and Control Room restrooms. Air returning from the Control Room is drawn into the Essential AHUs which filter the air and discharge it to the essential supply distribution ducts. This post-CREFAS alignment (essential filtration mode) ensures a positive pressure exists inside the Control Room to prevent in-leakage from outside air.
TS Limiting Condition for Operation (LCO) 3.3.9 requires only one of the two CREFAS channels to be OPERABLE during Mode 6 or irradiated fuel movement.
An OPERABLE CREFAS channel consists of a CREFAS manual trip, actuation logic, and a Control Room air intake radiation monitor. If any of those three components are inoperable, LCO 3.3.9 Condition C Required Actions are to either:
Place one CREFS train in operation, immediately (C.1), or Suspend movement of irradiated fuel assemblies, positive reactivity additions, and core alterations, immediately (C.2.1, C.2.2, and C.2.3).
The safety function of a CREFAS is to actuate CREFS to mitigate the consequences of analyzed accidents, including a fuel handling accident, to ensure Control Room habitability is maintained in accordance with General Design Criterion 19 of 10 CFR 50 Appendix A.
- 3.
INITIAL PLANT CONDITIONS
On April 8, 2011, Palo Verde Unit 2 was in Mode 6 (Refueling). The 120 VAC Class 1 E bus D25 had been deenergized since 0956 that day, which rendered train "A" Control Room air intake radiation monitor RU-29 and its associated CREFAS channel inoperable.
Deenergized bus D25 similarly affected the "A" channels of CPIAS and FBEVAS, which were rendered inoperable. The opposite "B" train channels of CREFAS, CPIAS, and FBEVAS remained OPERABLE. Reactor core offload was in progress with irradiated fuel
movement occurring in the Fuel Building. The essential AHU for Train "B" CREFS was in service and isolated from normal Control Room ventilation, providing filtered air to the Control Room. The isolation dampers for the communication and inverter rooms and the Control Room kitchen and Control Room restrooms were open. In this condition, the Control Room does not have the positive pressure associated with the CREFS essential filtration mode required for post-accident emergency alignment.
4. EVENT DESCRIPTION
On April 8, 2011, at 1803, during shift turnover, the train "B" Control Room air intake radiation monitor RU-30 was declared INOPERABLE upon notification of a communication failure between the radiation monitor and the Radiation Monitoring System Remote Indication and Control unit. This communication failure resulted in RU-30 being unable to initiate a CREFAS.
The Control Room Supervisor (CRS) (utility, licensed) directed the Reactor Engineer (utility, non-licensed) to stop fuel movement and gave permission to continue movement of the irradiated fuel assembly on the Spent Fuel Handling Machine to place it in a safe location, consistent with the bases for LCO 3.7.11.
The CRS informed the Shift Manager (SM) (utility, licensed), who was engaged in shift turnover, of the loss of RU-30 and the direction provided to the Reactor Engineer to cease irradiated fuel movement. The SM and the CRS reviewed TS LCO 3.3.9 and concluded that the condition of Required Action C.1 (one train of CREFS in operation) was met since the Train "B" Control Room Essential AHU, was running. The TS Basis for LCO 3.3.9 was not referenced by either the SM or CRS.
The SM authorized recommencement of irradiated fuel movement since the Unit was understood (incorrectly) to be in compliance with LCO 3.3.9 Required Action C.1. The CRS, at 1808 notified the Reactor Engineer that irradiated fuel movement could recommence.
Following the completion of turnover a Control Room log entry was made to document that the Unit was in compliance with LCO 3.3.9 Required Action C.1 and that CREFS train "B" was in service.
At 2140, the Outage Shift Manager (utility, licensed) entered the Control Room and noted that the Control Room envelope was not pressurized to the extent expected. The Outage Shift Manager questioned the actions that were taken to comply with LCO 3.3.9 Required Action C.1. At this time, Control Room staff determined that Control Room ventilation had not been
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realigned to the CREFS essential filtration mode required for post-accident emergency alignment, as stipulated in the LCO 3.3.9 Technical Specification Basis. The wording in the basis document states:
"Condition C applies to the failure of two channels of CREFAS Manual Trip, Actuation Logic, and Radiation Monitor channel in MODE 5 or 6, or when moving irradiated fuel assemblies. The required actions are immediately taken to place one OPERABLE CREFS train in the emergency mode of operation (i.e., fan running, valves/dampers aligned to the post CREFAS mode, etc.) or to suspend CORE AL TERA TIONS, positive reactivity additions, and movement of irradiated fuel assemblies. The [Immediate]
Completion Time recognizes the fact that FBEVAS, or CPIAS are available to initiate Control Room filtration in the event of a fuel handling accident."
At 2146, the Control Room ventilation dampers were re-aligned to comply with LCO 3.3.9, Required Action C.1. Irradiated fuel movement was not suspended at this time because re-alignment of CREFS occurred immediately. The Completion Time for this LCO Required Action was exceeded by approximately three hours and forty-five minutes.
4. ASSESSMENT OF SAFETY CONSEQUENCES
The safety analysis of record for a fuel handling accident credits the CPIAS or FBEVAS to provide the safety function to actuate CREFAS. Those two signals are actuated by corresponding radiation monitors in the containment and fuel buildings should a fuel handling accident occur. The CREFAS actuation automatically places CREFS in the essential filtration mode required for post-accident emergency alignment to ensure the corresponding control room habitability safety function is maintained.
The required "B" train channels for CPIAS and FBEVAS were OPERABLE at the time the condition occurred. Therefore, the inoperable control room air intake radiation monitors RU-29 and RU-30 would not have prevented the fulfillment of the CREFAS safety function to mitigate the consequences of a fuel handling accident.
This event did not result in any challenges to the fission product barriers or result in the release of radioactive materials. There were no actual safety consequences as a result of this event. This event did not prevent the fulfillment of a safety function nor did it result in a safety system functional failure as described by 10 CFR 50.73 (a)(2)(v).
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- 5.
CAUSE OF THE EVENT
The direct cause of the failure to comply with TS LCO 3.3.9 was the decision to allow irradiated fuel movement to recommence with Control Room ventilation not in the essential filtration mode required for post-accident emergency alignment.
The root cause was imprecise terminology in LCO 3.3.9 Required Action C.1, in that it failed to specify that CREFS shall be placed in the essential filtration mode required for post-accident emergency alignment.
Contributing causes included:
A latent organizational weakness existed in the reinforcement of Operations expectations for Technical Specification Decision Making, which allowed the Technical Specification decision to be made without consulting the Technical Specification Bases for LCO 3.3.9 Required Action C.1.
" Inadequate guidance to facilitate meeting the requirements of LCO 3.3.9, Required Action C.1 in that there is inconsistent terminology relative to Control Room ventilation modes of operation among the LCO, LCO bases, and procedures.
" An operator knowledge deficiency exists in the area of the Control Room ventilation system and related Technical Specifications.
- 6.
CORRECTIVE ACTIONS
The Control Room ventilation dampers were re-aligned to be in compliance with the requirements of LCO 3.3.9, Required Action C.1 at 2146 on April 8, 2011.
To prevent recurrence, a License Amendment Request (LAR) will be submitted to the NRC to revise LCO 3.3.9 Required Actions A.1 and C.1 to ensure more specific direction is provided regarding the alignment of CREFS when LCO 3.3.9 Conditions A or C are entered. The LAR will also request similar revision to related LCO 3.7.11 (CREFS) which contains similar imprecise required actions. Following implementation of revised LCOs 3.3.9 and 3.7.11, a NNU 1UXM ibbA ~1U-iU1U()
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simulator scenario in Licensed Operator Continued Training will be included that requires crews to exercise the amended Required Actions of these LCOs.
The following additional corrective actions will be taken to address the contributing causes:
" Change the Technical Specification Decision Making process expectations and procedures to emphasize that Technical Specifications and Bases must be used together to understand and comply with the license.
Revise Control Building ventilation procedures to support compliance with LCO 3.3.9 and 3.7.11 Required Actions.
Incorporate additional training into Licensed Operator initial and continuing training programs to correct the identified knowledge deficiency.
The above and any additional corrective actions taken as a result of the investigation of this event will be implemented in accordance with the requirements of the Palo Verde corrective action program. If information is subsequently developed which would significantly affect a reader's understanding or perception of this event, a supplement to this LER will be submitted.
7. PREVIOUS SIMILAR EVENTS
The station has not identified prior TS violations related to CREFS not being placed in the essential filtration mode required for post-accident emergency alignment while irradiated fuel movement was in progress.
Although not related to irradiated fuel movement in Mode 6, an adverse condition report identified a similar event. The adverse condition report, generated on June 18, 2007, addressed Control Room log entries that incorrectly identified affected LCOs for inoperable, bypassed Engineered Safety Features Actuation System functions, including CREFAS. For example, one of the log entries cited the following:
"LCO 3.7.11 Required Action D. 1 was met due to "B" CR ESS [ "B" Train Control Room Essential ] AHU Fan running. However the Bases identifies that the train must be in "emergency mode of operation (i.e., fan running, valves/dampers aligned to the post-CREFAS mode, etc.)." At 0826 on 6/18/07 it was identified I-qNIIN I tU UIN ~(tLAULtU,-'I4rt~(
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that the smoke exhaust and communication equipment room isolation dampers were not aligned to the 'post CREFAS' mode."
The corrective actions of the condition report focused on correcting the log entries and did not evaluate the causes for the incorrect log entries regarding Required Actions and bases for LCO 3.7.11 with respect to system alignments. Therefore, the corrective actions of that condition report would not have prevented this event.PRINTED ON RECYCLED PAPER