05000529/LER-2012-001, Regarding Technical Specification LCO 3.1.7 Completion Time Exceeded
| ML12101A100 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/26/2012 |
| From: | Mims D Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 102-06495-DCM/KAC LER 12-001-00 | |
| Download: ML12101A100 (6) | |
| 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 |
| 5292012001R00 - NRC Website | |
text
P 10 CFR 50.73 ZAMA subsidiary of Pinnacle West Capital Corporation Palo Verde Nuclear Generating Station Dwight C. Mims Senior Vice President Nuclear Regulatory and Oversight Tel, 623-393-5403 Fax 623-393-6077 Mail Station 7605 P. O. Box 52034 Phoenix, Arizona 85072-2034 102-06495-DCM/KAC March 26, 2012 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 2012-001-00 Enclosed, please find Licensee Event Report (LER) 50-529/2012-001 -00 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER reports a condition prohibited by Technical Specification (TS) 3.1.7, Regulating Control Element Assembly (CEA) Insertion Limits, after a regulating CEA group was not fully withdrawn within the TS required time limits following a reactor power cutback.
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 Mark McGhee, Operations Support Manager, Regulatory Affairs, at (623) 393-4972.
Arizona Public Service Company makes no commitments in this letter.
Sincerely, DCM/TNW/MAM/KAC/hsc Enclosure cc:
E. E. Collins Jr.
B. K. Singal L. K. Gibson J. R. Hall M. A. Brown NRC Region IV Regional Administrator NRC NRR Project Manager for PVNGS (electronic / paper)
NRC NRR Project Manager for PVNGS (electronic)
NRC NRR Senior Project Manager (electronic)
NRC Senior Resident Inspector for PVNGS A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
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- 13. PAGE Palo Verde Nuclear Generating Station (PVNGS) Unit 2 05000529 1 OF 5
- 4. TITLE Technical Specification LCO 3.1.7 Completion Time Exceeded
- 5. EVENT DATE
- 6. LER NUMBER__
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YE FACILITY NAME DOCKET NUMBER NUMBER NO.
MNH DY YA FACILITY NAME DOCKET NUMBER 01 25 2012 2012
- - 001 00 03 26 2012
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all 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)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
[I 20.2203(a)(1)
[I 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[I 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
[] 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
E] 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
E] 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) 60 El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
[I 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 CEDMCS controls can raise or lower CEAs in groups or individually. When moved as a group, withdrawal is limited by the upper group stop (UGS) feature, which limits outward group travel to 145.5 inches withdrawn. To fully withdraw the CEAs, past the UGS position, the operator must withdraw each CEA individually to the fully withdrawn position as defined in the COLR.
The reactor power cutback system (EIIS: JD) quickly reduces plant power, when greater than 75% power, for events such as large load rejection or loss of a single main feedwater pump. This function is performed by full insertion of regulating CEA groups 4 and 5 and a rapid turbine load reduction (if the main turbine is not tripped). The steam bypass control system (SBCS) will operate simultaneously to provide additional heat removal, as necessary, to match primary plant power with steam demand. The reactor regulating system (RRS) will operate to insert or withdraw regulating CEA groups in order to match reactor power with steam demand. Following a reactor power cutback, plant power will decrease to approximately 50 to 60 percent with the RRS, SBCS, Digital Feedwater Control System, and other related control systems operating simultaneously to stabilize the plant.
- 3.
INITIAL PLANT CONDITIONS
On January 25th, 2012, Unit 2 was in Mode 1 operating at 100 percent power. There were no structures, systems, or components inoperable at the time of the event that contributed to the event.
- 4.
EVENT DESCRIPTION
On January 25th, 2012 at 1005, Unit 2 experienced a loss of a non-class 1E 4.16 KV power bus, which caused a low suction pressure trip of the "B" main feedwater pump, resulting in a reactor power cutback. Following the reactor power cutback, regulating CEA groups 4 and 5 inserted as designed and were subsequently withdrawn per the reactor power cutback abnormal operating procedure to restore CEA group overlap and to restore the CEAs to within their insertion limits as required by TS LCO 3.1.7. Regulating CEA group 3 inserted as designed and was subsequently withdrawn to the UGS position of 145.5 inches at 1124. No additional changes were made to regulating group 3 CEA positions for the remainder of the day shift. Following shift turnover, the regulating group 3 CEAs were individually withdrawn to
149.25 inches at 2030, at which time regulating group 3 CEAs were in compliance with the insertion limits of TS LCO 3.1.7 and the COLR.
During a review of plant reactor power cutback response, a reactor engineer noted that initial withdrawal of regulating group 3 CEAs was stopped at the UGS position. At 2101, the reactor engineer notified the control room staff that regulating group 3 CEAs at the UGS position potentially did not satisfy TS LCO 3.1.7 transient insertion limits because the COLR required regulating CEA group 3 to be fully withdrawn to >/= 147.75 inches. Although in compliance at the time, Operations determined that regulating CEA group 3 at the UGS position of 145.5 inches had not met the fully withdrawn requirements of the COLR and TS LCO 3.1.7.
- 5.
ASSESSMENT OF SAFETY CONSEQUENCES
This condition did not adversely affect plant safety or the health and safety of the public. The condition did not result in any challenges to the fission product barriers or result in any releases of radioactive materials. The safety limits for departure from nucleate boiling ratio and fuel peak centerline temperature were not exceeded as a result of this event. Therefore, there were no actual adverse safety consequences as a result of this condition.
An evaluation was performed to quantify the effect of the excess regulating CEA group 3 insertion on the available shutdown margin. This evaluation determined that the reactivity effect from regulating CEA group 3 being inserted 2.25 inches below its transient insertion limit was sufficiently compensated for by the reactivity associated with the positions of regulating CEA groups 4 and 5. Therefore, the failure to comply with TS LCO 3.1.7 insertion limits did not reduce available shutdown margin below the minimum acceptable value and did not affect the associated safety function to safely shutdown the reactor. The small deviation from the transient insertion limit did not represent an unanalyzed condition that significantly degraded plant safety.
This event did not prevent the fulfillment of a safety function and did not result in a safety system functional failure as described by 10 CFR 50.73(a)(2)(v).
- 6.
CAUSE OF THE EVENT
The root cause was determined to be inadequate procedural guidance necessary to ensure regulating CEA group 3 was fully withdrawn to comply with the requirements of TS LCO 3.1.7 insertion limits.
Contributing causes included inadequate procedure use and adherence and operator knowledge weaknesses.
- 7.
CORRECTIVE ACTIONS
To prevent recurrence, the procedures for operation following a reactor power cutback event will be revised to include direction on positioning all CEA groups above the limits required by TS LCO 3.1.7 and the COLR.
To address related procedure use and adherence and operator knowledge weaknesses, licensed operator continuing training simulator sessions will be conducted involving the revised abnormal operating procedures that will include restoring CEA positions to address compliance with TS LCO 3.1.7 insertion limits. Licensed operator training tasks will be revised to require periodic training on compliance with CEA insertion TSs following reactor power cutback.
- 8.
PREVIOUS SIMILAR EVENTS
A similar event occurred in 1996 in Unit 3 where several regulating group 3 CEAs were not withdrawn to the TS required fully withdrawn position following a load rejection reactor power cutback event. At that time, TS LCO 3.1.3.6 specified a fully withdrawn position of >/= 144.75 inches which was below the UGS position of 145.5 inches.
When regulating group 3 CEA motion was stopped at the UGS position, several group 3 CEAs remained below the fully withdrawn position due to normal system operation which allows small position differences within a group. During surveillance testing it was noted that several regulating group 3 CEAs remained below the fully withdrawn acceptance criteria that existed at that time (>/= 144.75 inches). The 1996 corrective actions did not implement adequate barriers to prevent recurrence because no causal evaluation was done and specific guidance was not established to ensure CEA insertion limits are restored following reactor power cutback.