05000263/LER-2013-006, Regarding Unanalyzed Condition for Emergency Diesel Generator Fuel Oil Pumps Train Separation
| ML13291A366 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 10/18/2013 |
| From: | Fili K Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-MT-13-104 LER 13-006-00 | |
| Download: ML13291A366 (5) | |
| 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 |
| 2632013006R00 - NRC Website | |
text
Xcel Energy*
October 18, 2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22 Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 L-MT-13-104 10 CFR 50.73 LER 2013-006 "Unanalyzed Condition for Emergency Diesel Generator Fuel Oil Pumps Train Separation" A Licensee Event Report (LER) for this occurrence is attached.
Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.
Karen D. Fili Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company-Minnesota Enclosure cc:
Regional Administrator, Region Ill, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 10/31/2013 (10-2010)
, the NRC rna& not conduct or sponsor, and a person is not required to respond to, the information collec 'on.
- 3. PAGE Monticello Nuclear Generating Plant 05000 -263 1 OF 4
- 4. TITLE Unanalyzed Condition for Emergency Diesel Generator Fuel Oil Pumps Train Separation
- 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 1 t-AviLII Y NAME DOCKET NUMBER 08 21 2013 2013 - 006 - 00 10 18 2013 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201 (b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(i)(C)
~ 50.73(a)(2)(vii) 1 D 20.2201 (d)
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2203(a)(1)
D 20.2203(a)(4)
~ 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(2)(i)
D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL D 20.2203(a)(2)(ii)
D 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x) 0 20.2203(a)(2)(iii)
D 50.36(c)(2)
~ 50.73(a)(2)(v)(A)
D 73.71(a)(4) 100%
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
~ 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
~ 50.73(a)(2)(v)(C)
D OTHER Specify in Abstract below or in D 20.2203(a)(2)(vi)
~ 50.73(a)(2)(i)(B)
~ 50.73(a)(2)(v)(D)
EVENT DESCRIPTION
- 3. PAGE 2 OF4 On August 21, 2013 with Monticello Nuclear Generating Plant (MNGP) in Mode 1, at 100% power, it was determined following receipt and review of Nuclear Regulatory Commission (NRC) Task Interface Agreement (TIA) 2012-03, that the design of the MNGP diesel fuel oil supply system [DC] was not consistent with the current and historical licensing and design basis documents. This condition affected the fuel oil (FO) supply from the diesel FO storage tank [TK] to both emergency diesel generators (EDG) [DG]. As a result Northern States Power Minnesota (NSPM) submitted Event Notification 49293 for an unanalyzed condition.
By letter dated August 20, 2013, the NRC determined that the diesel FO supply system design at MNGP was not consistent with current and historical licensing and design basis documents. The NRC stated that the MNGP current and historical licensing and design basis requires a fully redundant and independent diesel FO supply system from the FO storage tank to the individual EDG day tanks (i.e., two safety-related pumps that are physically separated and provided with independent piping and a safety-related power source).
Contrary to these requirements the NRC determined that the MNGP diesel FO supply system design does not follow the NRC approved design and licensing basis to provide for support of the EDG function.
Specifically, the design was deficient in the following areas:
Independence-The diesel FO supply pumps are not independent due to a crosstie line being open between the diesel FO supply pumps. The failure of the Division 2 EDG under loss of offsite power (LOOP) conditions renders the Division 1 diesel FO supply pump non-functional since the power supply will be inoperable.
Redundancy - The Division 1 diesel FO supply pump was not redundant to the Division 2 diesel FO supply pump due to lack of separation since the cross connect line between pumps has been left open. In this configuration a single passive pipe failure of the cross connect line renders both division diesel FO supply pumps inoperable.
Further, the NRC concluded that the original licensing basis does not include the need for manual actions to maintain or restore the fuel oil transfer function for the EDGs during design-basis accidents and that the licensee changed the basis to include a necessary manual action in order to compensate for the original single failure piping configuration without prior NRC approval.
Following completion of the corrective actions listed below and after review of this notification on August 22, 2013, the Division 1 diesel FO system was determined to be operable but not conforming.
EVENT ANALYSIS
This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition that significantly degraded plant safety and in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the Technical Specifications (TS).
This event is also reportable in accordance with 10 CFR 50.73(a)(2)(v) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to:
(A) Shut down the reactor and maintain it in a safe shutdown condition; (B) Remove residual heat; (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident.
- 6. LER NUMBER YEAR I SEQUENTIAL I REV NUMBER NO.
2013 006 00
- 3. PAGE 3 OF4 Finally, this event is reportable in accordance with 10 CFR 50.73(a)(2)(vii), as an event where a single cause or condition caused two independent trains to become inoperable in a single system designed to:
Shut down the reactor and maintain it in a safe shutdown condition; Remove residual heat; Control the release of radioactive material; or Mitigate the consequences of an accident.
SAFETY SIGNIFICANCE
The MNGP is required to be designed and constructed in accordance with the approved design and licensing bases. The design inadequacies in the diesel FO supply system could have affected the ability to protect the reactor during a LOOP event. Since there has been no LOOP event where diesel FO system design inadequacies caused a problem, there were no adverse consequences to the health and safety of the public or the plant and its personnel as a result of the identified deficiencies.
A risk assessment determined that a minimal risk change occurs when the current diesel FO system configuration is compared to full compliance with the design and licensing basis. Any change to this conclusion will be provided in the supplement to this Licensee Event Report (LER).
CAUSE
The root cause is under investigation by the site. A supplement to this LER will be submitted following completion of the investigation and will provide the root cause.
CORRECTIVE ACTION
Corrective actions performed to date include:
The cross connect line between the diesel FO supply pumps has been closed. Valves in the cross connect line were closed to provide independent diesel FO supply lines to each division EDG.
The Division 1 diesel FO pump was repowered from an essential powered bus instead of one that is load shed following a LOOP.
The diesel FO pump start/stop push buttons were replaced with maintained on/off switches which automatically restart each pump should an essential bus transfer occur. This modification coupled with the revised operation of these pumps, eliminates any operator action to manually start these pumps.
Other corrective actions are proposed to fully restore the diesel FO supply system to the design and licensing bases requirements.
The root cause is under investigation by the site. A supplement to this LER will be submitted following completion of the investigation and will provide corrective actions to address the root cause.
PREVIOUS SIMILAR EVENTS
- 3. PAGE 40F4 A review of LERs identified three previous similar events for failure to understand or correctly incorporate design and licensing bases information into the plant design and implementing documentation.
On September 29, 2011 as supplemented on February 28, 2012 the site identified in LER 2011-007-01 that the surveillance test procedure used to demonstrate compliance with TS surveillance requirement (SR) 3.8.1.7, involving load reject testing of the EDG with the single largest post-accident load, did not satisfy the TS SR. The cause of the event was an inadequate surveillance test procedure resulting from a failure to fully reflect the changes enacted through the implementation of Improved TS (ITS) in 2006. The SR was not correctly translated into an adequate test to meet SR 3.8.1. 7 and hence was not correctly implemented as part of the ITS implementation process.
On July 5, 2012 the site identified in LER 2012-001 that the degraded voltage transfer scheme was not in compliance with TS 3.3.8.1. The cause of the event was a failure to completely include the licensing basis for the 1AR Transformer time delay (5 seconds) degraded voltage requirements in the TSs. Corrective actions included revising the site TS through a license amendment to eliminate the time delay relay from the TSs and remove the relay from the plant.
On July 30, 2013 as supplemented on September 26, 2013 the site identified in LER 2013-003-01 that there was an institutionalized misunderstanding of the design and licensing bases associated with preparations and mitigation activities to support responding to a Probable Maximum Flood (PMF) event. The corrective actions from this event include clarifying the design and licensing bases in plant documents, preplanning for a PMF, and incorporating the PMF plan consistent with the licensing basis into a plant procedure.
ADDITIONAL INFORMATION
Energy industry identification system (EllS) codes are identified in the text within brackets [xx].