05000275/LER-2012-004, Regarding Mode Transition with Turbine-Driven Auxiliary Feedwater Pump 1-1 Inoperable
| ML12227A290 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/13/2012 |
| From: | Welsch J Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-12-079 LER 12-004-00 | |
| Download: ML12227A290 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(8) 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)(8) 10 CFR 50.73(a)(2)(viii)(8) 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)(8) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2752012004R00 - NRC Website | |
text
Pacific Gas and Electric Company August 13, 2012 PG&E Letter DCL-12-079 James M. Welsch Station Director Diablo Canyon Power Plant Mail Code 104/ 5/ 502 P. O. Box 56 Avila Beach, CA 93424 805.545.3242 Internal: 691.3242 Fax: 805.545.4234 Internet: JMW1@pge.com u.s. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 10 CFR 50.73 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 Licensee Event Report 1-2012-004-00, Mode Transition with Turbine-Driven Auxiliary Feedwater Pump 1-1 Inoperable Dear Commissioners and Staff; Pacific Gas and Electric Company (PG&E) submits the enclosed Licensee Event Report (LER) regarding an improper mode transition with an inoperable turbine-driven auxiliary feedwater pump. PG&E is submitting this LER in accordance with 10 CFR 50.73(a)(2)(i)(8) and providing the cause, corrective actions and assessment of safety consequences for the event.
PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this report.
This event did not adversely affect the health and safety of the public.
Sincerely,
~~
James M. Welsch Interim Site Vice President wrl8/50491 007 Enclosure cc/enc:
Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Joseph M. Sebrosky, NRR Senior Project Manager INPO Diablo Distribution A member of the STARS (Strategic Team i ng and Resource Sharing) All i ance Ca ll away. Comanche Peak. Diab l o Canyon. Palo Verde. San Onofre. South Texas Project. Wolf Creek
NRC FORM 366 (10-2010)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME
- 3. PAGE Diablo Canyon Power Plant
- 2. DOCKET NUMBER 05000-275 1 OF 4
- 4. TITLE Mode Transition with Turbine-Driven Auxiliary Feedwater Pump 1-1 Inoperable
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER NUMBER NO.
MONTH DAY YEAR MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 06 13 2012 2012 00 08 13 2012
- 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)
D 50.73(a)(2)(vii)
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)
D 50.73(a)(2)(ii)(8)
D 50.73(a)(2)(viii)(8) 3 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)
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)
B 50.36(c)(2)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iv) 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(8)
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) 71 50.73(a)(2)(i)(8)
D 50.73(a)(2)(v)(D)
Sp~cify in Abstract below I.!...J or In NRC Fonm 366A
- 10. POWER LEVEL o
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME I
TELEPHONE NUMBER (Indude Area Code)
Wilbert R. Landreth, Regulatory Services Engineer (805) 545-6980 MANU-REPORTABLE FACTURER TO EPIX
- CAUSE, SYSTEM COMPONENT
- 14. SUPPLEMENTAL REPORT EXPECTED D YES (If yes, complete 15. EXPECTED SUBMISSION DA TE) 0 NO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
CAUSE
SYSTEM COMPONENT
- 15. EXPECTED SUBMISSION DATE MANU-REPORTABLE FACTURER TO EPIX MONTH DAY YEAR On June 13,2012, at 1115 PDT, during the 17th Refueling Outage for Unit 1 (lR17), Diablo Canyon Power Plant (DCPP) entered Technical Specification (TS) 3.7.5.B, due to one auxiliary feedwater (AFW) train being inoperable in Mode 3. After entering Mode 3, steam turbine-driven AFW Pump (TD AFW PP) 1-1 failed its routine and post-maintenance surveillance testing when the pump speed was higher than the acceptable limit and could not be lowered. Plant operators declared TD AFW PP 1-1 inoperable as required by TS 3.7.5. TS 3.7.5.B.l requires action to restore the AFW train to operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 10 days from discovery of failure to meet the Liming Condition for Operation.
Mechanical Maintenance (MM) rebuilt TD AFW PP Governor Valve FCV -15 and replaced the valve stem during 1 R17.
MM reassembled the valve and installed the stem positioning jam nuts. However, due to inadequately detailed work instructions, the jam nuts were installed such that the valve could not be fully closed. The procedure used to perform the work did not include steps requiring a [mal verification that the valve would fully close. During troubleshooting activities, MM confirmed that FCV -15 was partially open when it should have been fully closed. After repair and reassembly of FCV -15, plant operators successfully completed surveillance testing for TD AFW PP 1-1. On June 14,2012, at 2256 PDT, plant operators declared the AFW train operable within the TS time limit imposed. DCPP will revise plant procedures to provide detailed instructions to verify a full-closed valve position.
NRC FORM 366 (10-2010)
I. Plant Conditions
During surveillance testing of the Unit 1 auxiliary feedwater (AFW) system [BA], Unit 1 transitioned from Mode 4 (Hot Shutdown) to Mode 3 (Hot Standby). The reactor [RCT] coolant system (RCS) [SJ] temperature and pressure at this time were about 500 degrees Fahrenheit and 1880 pounds per square inch (psig) respectively. The steam generator (SG) [SG]
pressure was approximately 650 psig.
II. Description of Problem A. Background Diablo Canyon Power Plant's (DCPP's) AFW system consists of three AFW supply trains. One train has a full-capacity, approximately 780 gallon-per-minute (gpm), steam turbine-driven AFW Pump (TD AFW PP) 1-1 aligned to all four SGs.
The other two trains have half-capacity, motor-driven AFW Pumps 1-2 and 1-3, each supplying approximately 390 gpm to two of the four SGs, with the capability to be manually aligned to any of the four SGs. The function of the AFW system during unit startup and shutdown is to supply the SGs with a secondary heat sink while the main feedwater system [SJ] is unavailable.
Technical Specification (TS) Limiting Condition for Operation (LCO) 3.7.5, "Auxiliary Feedwater System," requires three AFW trains to be operable in Mode 1 (Power Operation), Mode 2 (Startup), and Mode 3. TS LCO 3.7.5 is modified by a note that prohibits mode transition with an inoperable AFW pump [P]. Surveillance Requirement (SR) 3.7.5.2 requires testing of TD AFW PP 1-1 to be performed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after reaching 650 psig steam pressure in the SGs.
B. Event Description
Mechanical Maintenance (MM) rebuilt TD AFW PP Governor Valve FCV -15 [FCV] and replaced the valve stem during the 17th Refueling Outage for Unit 1 (lRI7). After the rebuild, and after the new governor valve stem was installed, MM reassembled the valve and installed the stem positioning jam nuts. However, due to inadequately detailed work instructions, the jam nuts were later found to be installed such that the valve could not travel to its full-closed position.
The procedure that MM was using to perform the work did not include any steps that required a [mal verification that the valve would fully close.
Plant operators reviewed the maintenance that was performed on FCV-15, completed post-maintenance testing, and concluded requirements for declaring TD AFW PP 1-1 operable were satisfied as described by SR 3.0.1 Bases, allowing operators to proceed to Mode 3 where other necessary post-maintenance tests can be completed.
After entering Mode 3 during lR17, TD AFW PP 1-1 failed its routine and post-maintenance Surveillance Test Procedure (STP) P-AFW-ll when the pump speed was found to be too high, but still below the over-speed trip setpoint, and could not be lowered within the acceptable range using the TD AFW PP speed controller. On June 13,2012, at 1115 PDT, during 1 R17, Pacific Gas and Electric Company (PG&E) entered TS 3.7.s.B, with one AFW train inoperable in Mode 3 due to TD AFW PP 1-1 failing its surveillance test. TS 3.7.5.B.l requires action to restore the AFW train to operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 10 days from discovery of failure to meet the Liming Condition for Operation.
During troubleshooting activities, MM detennined that FCV-15 was about 1/8 inch open when it should have.been fully closed. MM corrected the improper position of the valve stem, and reassembled the valve. After final reassembly, plant staff completed surveillance testing of the TD AFW PP and detennined that the required surveillance perfonnance criteria was successfully met, confinning satisfactory perfonnance of the valve and thus, the speed control of the pump.
On June 14,2012, at 2256 PDT, plant operators declared the AFW train operable within the 72-hour time limit imposed by TS Action 3.7.5.B.1. PG&E detennined that TD AFW PP 1-1 was consequently inoperable during the mode transition from Mode 4 to Mode 3.
C. Status of Inoperable Structures, Systems, or Components that Contributed to the Event None.
D. Other Systems of Secondary Functions Affected None.
E. Method of Discovery
The unsatisfactory perfonnance ofTD AFW PP 1-1 was discovered during the perfonnance of post-maintenance surveillance testing. Troubleshooting detennined that plant operators were unable to control the speed ofthe pump because FCV -15 would not fully close.
F. Operator Actions
As described in Section B, "Event Description."
G. Safety System Responses None.
III. Apparent Cause The FCV -15 valve stem was not installed properly due to insufficiently detailed instructions for the governor valve.
IV. Assessment of Safety Consequences
The as-found condition ofFCV-15 prevented TD AFW PP 1-1 from meeting its surveillance acceptance criteria at recirculation flow. Troubleshooting confinned the governor was functioning properly, and that the valve was slightly open with the governor servo at its travel limit in the closed direction due to improper positioning because of insufficiently detailed governor valve instructions. Once the improper position was corrected, the governor controller functioned nonnally, satisfying the surveillance acceptance criteria at recirculation flow. PG&E's evaluation concluded that full-flow perfonnance would not have been affected in the as-found condition.
V. Corrective Actions
PG&E will take the following corrective actions:
- 6. LER NUMBER YEAR I SEQUENTIAL I NUMBER 2012 004 REV NO.
00
- 3. PAGE 4
OF 4
- 1) Revise plant procedure MP M-3.8, "Teny Turbine Governor Valve Maintenance," to provide detailed instructions for removal and reinstallation of the governor valve stem to ensure governor valve can be fully closed.
- 2) Revise plant procedure MP M-4.25 "Auxiliary Feedwater Pump Turbine Governor Maintenance,"to provide detailed instructions for [mal verification of the governor valve position.
VI. Additional Information
A. Failed Components None.
B. Previous Similar Events
A previous event occurred on January 3, 2011, when PG&E identified that the TD AFW PP 1-1 was inoperable on November 6, 2010, due to an improperly set speed governor in Mode 3. The TD AFW PP 1-1 post maintenance test identified that the TD AFW PP 1-1 as-found condition exceeded the engineering-established acceptance criteria of 4,260 revolutions per minute for surveillance testing of the pump. PG&E determined that the TD AFW PP 1-1 was consequently inoperable during the mode transition from Mode 4 to Mode 3 (Ref. Licensee Event Report 1-2011-001-01).
PG&E replaced the Unit 2 TD AFW PP 2-1 speed governor during the 14th Refueling Outage for Unit 2 and discovered that the TD AFW PP 2-1 exhibited issues similar to the above. On April 10, 2008, after entry into Mode 3 from Mode 4, the TD AFW PP 2-1 as-found pump speed was lower than the minimum value specified in the STP. PG&E determined that the TD AFW PP 2-1 was consequently inoperable during the mode transition from Mode 4 to Mode 3. This event was recognized more than 3 years after the incident and was therefore not reported in accordance with 10 CFR 50.72 or 50.73.