05000275/LER-2013-009-01, Regarding Unanalyzed Condition Affecting Unit 1 Emergency Diesel Generators
| ML14135A001 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/14/2014 |
| From: | Allen B Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PG&E Letter DCL-14-044 LER 13-009-01 | |
| Download: ML14135A001 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 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)(i)(B), Prohibited by Technical Specifications |
| 2752013009R01 - NRC Website | |
text
Pacific Gas and Electric Company May 14, 2014 PG&E Letter DCL-14-044 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 Barry S. Allen Site Vice President 10 CFR 50.73 Licensee Event Report 1-2013-009-01, Unanalyzed Condition Affecting Unit 1 Emergency Diesel Generators
Dear Commissioners and Staff:
Diablo Canyon Power Plant Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424 805.545.4888 Internal: 691.4888 Fax: 805.545.6445 Pacific Gas and Electric Company (PG&E) submits the enclosed Licensee Event Report (LER) supplement for an unanalyzed condition that affected the Unif 1 emergency diesel generators. PG&E is submitting this LER supplement in accordance with 10 CFR 50.73(a)(2)(ii)(B) and 50.73(a)(2)(v)(D). PG&E is submitting this supplement to provide updated cause and corrective action information.
PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this report. All the corrective actions identified in this letter will be implemented in accordance with the Diablo Canyon Power Plant Corrective Action Program.
This event did not adversely affect the health and safety of the public.
Sincerely, J5'7 5_ At&-
Barry S. Allen SSZ1 /4040/50599190 Enclosure Cc\\enc.: Peter J. Bamford, NRR Project Manager Marc L. Dapas, NRC Region IV Administrator Thomas R. Hipschman, NRC Senior Resident Inspector IN PO Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- Wolf Creek
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 0113112017 (01-2014)
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- 3. PAGE Diablo Canyon Power Plant Unit 1 05000 275 1 OF 4
- 4. TITLE Unanalyzed Condition Affecting Unit 1 Emergency Diesel Generators
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 12 14 2013 2013 -
009 -
01 05 14 2014 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 2o.22o1(b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(i)(C)
D 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) 0 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
I 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)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4) 100 D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(C)
D OTHER D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in
I. Plant Conditions
LICENSEE EVENT REPORT (LER) r U.S. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET
- 2. DOCKET
- 6. LER NUMBER YEAR 05000-275 2013 SEQUENTIAL REV. NO NUMBER 009 01
- 3. PAGE 20F4 Unit 1 operated in Mode 1 (Power Operation) at approximately 100 percent reactor power with normal operating reactor coolant temperature and pressure throughout the event.
II. Problem Description A. Background Diablo Canyon Power Plant (DCPP) Unit 1 has three emergency diesel generators (EDGs) [DG] that provide vital backup power to three electrical buses [BU] to mitigate the consequences of a design basis accident (DBA) whenever normal or offsite power sources [EK] are unavailable. DCPP EDGs are designed to function so that a single failure of any EDG will not jeopardize the capability of the remaining EDGs to start and provide power to operate the shutdown systems required to mitigate any DBA condition.
The DCPP EDGs are cooled using engine-driven fans [FAN] that provide cooling air to the diesel generator radiators [HX]. The radiator fan draws air through the radiator, maintaining jacket water temperature and, in turn, maintaining lubricating oil temperature. Jacket water to the aftercooler also affects combustion air temperature. The radiator fan also draws ambient air through the engine compartment to cool the equipment housed within it.
Inability to maintain adequate radiator air flow will result in a rise in EDG jacket water temperature, higher component temperatures in the engine compartments, derating of the engine due to increased combustion air temperature, higher lubricating oil temperatures, and high cylinder jacket temperatures. This could result in a failure of the EDGs to perform their safety function.
For this analysis, "sustained high winds" is using as the average of Plant Process Computer (PPC) [PPC] data over a fifteen minute period.
B. Event Description
As reported in NRC EN 49634, DCPP identified that if atmospheric conditions were to develop that had both sustained high winds exceeding 60 miles per hour from the northwest (NW) to north northeast (NNE) direction, and ambient air temperature exceeding 97°F, the combination of these conditions could result in inadequate heat removal to support continuous operation of the Unit 1 emergency diesel generators.
On Unit 1, the main EDG radiator fan discharge flow is directed from the radiator, vertically though the turbine building 107 foot elevation floor, horizontally toward the west, out of the building on the west wall, and vertically through the exhaust plenums [DUCT]. A second exhaust flow path, however, is available for Unit 1. This second path is directed north along the EDG exhaust silencers, then out of the north wall either through a small set of louvers at the 107 foot elevation or downward and out the north wall through louvers at the 85 foot elevation.
FORM 366 (1 0-201 0) LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 1. FACILITY NAME Diablo Canyon Power Plant, Unit 1
- 2. DOCKET 05000-275
- 6. LER NUMBER YEAR 2013 SEQUENTIAL REV. NO NUMBER 009 01
- 3. PAGE 30F4 Sustained high winds blowing from a direction between 304° to 33° (NW to NNE) would oppose the normal air flow and create a backpressure on the EDG 1-1, 1-2 and 1-3 radiator fans through the exhaust flow paths on the north side of the turbine building. This could prevent adequate air flow and cooling through the EDG radiators.
High winds from the west would not adversely impact the exhaust flow out of the west wall plenum. The EDG ventilation system is not impacted by winds from other directions because of the site layout.
At the time of discovery, all offsite and onsite power sources were operable.
C. Status of Inoperable Structure, Systems, or Components That Contributed to the Event This issue is not currently impacting any plant equipment as winds are light and temperatures are mild. DCPP has no recorded evidence of sustained winds exceeding 55 miles per hour.
D. Other Systems or Secondary Functions Affected
A review of other systems, including the Unit 2 EDGs, concluded that design configurations preclude impacts from design basis winds and temperatures. Some of the systems reviewed had no safety or accident mitigation functions.
E. Method of Discovery
This was discovered during a review of the DCPP licensing basis by the PG&E Licensing Basis Verification Program team. They were investigating a concern brought to them by an outside agency.
F. Operator Actions
Operators verified that the EDGs were operable and issued shift orders that require, when conditions warrant, the implementation of existing procedural guidance to open plant doors. This will allow additional air flow, shown to provide adequate emergency diesel generator cooling to support continuous operation of the Unit 1 EDGs.
G. Safety System Responses None.
Ill. Cause of the Problem An apparent cause evaluation concluded that PG&E did not have a design process requirement in place to evaluate GDC-2 design criteria relative to SSC functional requirements other than for structural integrity issues.
IV. Assessment of Safety Consequences
DCPP performed a probabilistic risk assessment and documented the results in a formal calculation (PRA Calculation SOP 13-07). The risk contribution of the as-found condition was below the low risk significance guidance, deemed a "green" risk.
FORM 366 (1 0-201 0) 1. FACILITY NAME Diablo Canyon Power Plant, Unit 1 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 2. DOCKET 05000-275
- 6. LER NUMBER YEAR SEQUENTIAL REV. NO NUMBER 2013 009 01
- 3. PAGE 40F4 I
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V. Corrective Actions
A. Immediate Corrective Actions Operators verified that the EDGs were operable and issued shift orders that require, when conditions warrant, the implementation of existing procedural guidance to open plant doors. This will allow additional air flow, shown to provide adequate EDG cooling to support continuous operation of the Unit 1 EDGs.
A PPC alarm was established to warn operators of winds exceeding 60 miles per hour. If the plant is experiencing sustained winds exceeding 60 miles per hour from a direction between 304° (NW) and 33°(NNE),
operators will implement procedure steps to supplement EDG cooling.
Operators performed a plant walk down to verify that the instructions in the shift order were sufficient to physically implement the corrective actions.
B. Other Corrective Actions An increased monitoring sheet has been implemented utilizing PPC points for primary met tower ambient air temperature and wind speed. Should the combination of high ambient air temperature and high wind speed approach the thresholds for operability in the parametric study, operators will contact engineering for evaluation.
The PG&E design process procedures were revised to require evaluation of GDC-2 design criteria. PG&E will issue a design change to permanently modify the plant to resolve the wind issue.
VI. Additional Information
None.
A. Failed Components None.
B. Previous Similar Events
None.
C. Industry Reports None.
FORM 366 (1 0-201 0)