05000275/LER-2010-001, Regarding 2008 Loss of Auxiliary Building Ventilation System Exhaust Fans
| ML100880112 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/17/2010 |
| From: | Becker J Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-10-027 LER 10-001-00 | |
| Download: ML100880112 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(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)(i)(B), Prohibited by Technical Specifications |
| 2752010001R00 - NRC Website | |
text
Pacific Gas and Electric Company March 17, 2010 James R. Becker Site Vice President Diablo Canyon Power Plant Mail Code 104/5/601 R 0. Box 56 Avila Beach, CA 93424 805.545.3462 Internal: 691.3462 Fax: 805.545.6445 PG&E Letter DCL-10-027 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyons Unit 1 & Unit 2 Licensee Event Report 2-2010-001-00 2008 Diablo Canyon Power Plant Unit 2 Loss of Auxiliary Building Ventilation System Exhaust Fans
Dear Commissioners and Staff:
Pacific Gas and Electric Company submits the enclosed Licensee Event Report (LER) regarding an event that occurred in July 2008 when the Diablo Canyon Power Plant Unit 2 auxiliary building ventilation system exhaust fans where simultaneously turned off for a brief period of time (less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />). This LER is submitted in accordance with 10 CFR 50.73(a)(2)(v).
There are no new or revised regulatory commitments in this report.
This event did not adversely affect the health and safety of the public.
swh/2246/50295954 Enclosure cc/enc:
Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Alan B. Wang, NRR Project Manager INPO Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- San Onofre ° South Texas Project - WolfCreek
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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may not conductor sponsor, and a person is not required to respond to, the digits/Characters for each block) information collection.
- 13. PAGE Diablo Canyon Unit 2 05000323 1 OF 5
- 4. TITLE 2008 Diablo Canyon Unit 2 Loss of Auxiliary Building Ventilation System Exhaust Fans
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
[
- 8. OTHER FACILITIES INVOLVED SEUNILIRVFACILITY NAME DOCKET NUMBER MONTH DAY
'YEAR Y
SEQUENTIAL REV MONTH DAY YEAR NUMBER I
NO.
1FACILITY NAME DOCKET NUMBER 7
21 2008 2010 - 001 - 00 03 17 2010[.
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
S20.2201 (b)
El 20.2203(a)(3)(i)
[] 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) 1 El 20.2201(d)
[E 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)
El 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
[I 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL [1 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[1 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[I 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[1 73.71(a)(4)
] 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 100 El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or inNRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (include Area Code)
Steven W. Hamilton - Senior Regulatory Services Supervisor (805) 545-3449MANU-REPORTABLE MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX FACTURERACURTO EPEPX A
VF FAN R165 N
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On July 21, 2008, 05:04 PDT, Diablo Canyon Power Plant (DCPP) Unit 2 entered Technical Specification (TS) 3.0.3 when operators secured auxiliary building exhaust fan E-1 with auxiliary building exhaust fan E-2 cleared for maintenance. The securingof auxiliary building exhaust fan E-1 resulted in a loss of all DCPP Unit 2 auxiliary building ventilation system exhaust.
On July 21, 2008, 0534 PDT, DCPP Unit 2, TS 3.0.3 was exited when auxiliary building exhaust fan E-1 was restarted.
On January 28, 2010, PG&E conducted a review of past events for safety system functional failures. Past events included entries into TS 3.0.3. This review was conducted utilizing recently published U.S. NRC training material on this subject. This review concluded that the simultaneous inoperability of the DCPP Unit 2 auxiliary building exhaust fans constituted a safety system functional failure and as such was reportable under 10 CFR 50.73(a)(2)(v).
NRC FORM 366 (9-2007)
PRINTED ON RECYCLED PAPER
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISION NUMBER DiabloCanyonUnit2 050 0
0 3 2 3 2010 0
0 1
0 0
2 OF 5
TEXT
- 1.
Plant Conditions
At the time of the event Unit 2 was in Mode 1 (Power Operation) at approximately 100 percent reactor power with normal operating reactor coolant temperature and pressure.
I1.
Description of Problem A.
Background
The DCPP Auxiliary Building Ventilation System (ABVS) exhaust fans provide a constant exhaust air flow from the DCPP auxiliary building. The DCPP ABVS exhaust fans also:
" Maintain a negative pressure in the DCPP auxiliary building.
" Limit the maximum design engineered safety feature (ESF) equipment room temperature to 1040F in the auxiliary building.
" Ensure radioactivity is filtered during accident conditions and released through the exhaust system and monitored at the plant vent.
The ABVS has several modes of operation: Building Only operation, Safeguards operation, and Building and Safeguards operation. A safety injection signal ('S' signal) will cause a nonoperating, stand-by ABVS exhaust fan to start and align to the plant vent. An operating ABVS exhaust fan experiencing low inlet flow will shutdown down automatically. Should a low flow event occur, a system reset is required for the ABVS prior to manually restarting or auto-restart via an 'S' signal.
B.
Event Description
On July 21, 2008, 05:04 PDT, DCPP Unit 2 entered Technical Specification (TS) 3.0.3 when plant operators closed the suction dampers of the running exhaust fan E-1 prior to placing an 'S' signal into the system. This action resulted in tripping auxiliary building exhaust fan E-1 with auxiliary building exhaust fan E-2 cleared for maintenance. Placing a 'S' signal into the system would have opened an alternate flow path and would have prevented the trip of the running fan.
Failure to select the 'S' signal caused the only available exhaust fan to trip off on low flow, placing the plant in a one-hour TS action statement. This resulted in a loss of all DCPP Unit 2 ABVS exhaust.
On July 21, 2008, 0534 PDT, DCPP Unit 2 exited TS 3.0.3 when plant operators restarted auxiliary building exhaust fan E-1 by resetting the ABVS and inserting a
'S' signal.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISION NUMBER DiabloCanyonUnit2 050 0
0 3 2 3 2010
- - 10 0
1 0
0 3
OF 5
TEXT On January 28, 2010, PG&E conducted a review of past events for safety system functional failures. This review was conducted utilizing recently published U.S.
NRC training material on this subject. This review concluded that the simultaneous inoperability of the DCPP Unit 2 auxiliary building exhaust fans constituted a safety system functional failure and as such was reportable under 10 CFR 50.73(a)(2)(v).
C.
Status of Inoperable Structures, Systems, or Components that Contributed to the Event None.
D.
Other Systems or Secondary Functions Affected
No additional safety systems were adversely affected by this event.
E.
Method of Discovery
PG&E conducted a review of past events for safety system functional failures.
This review was conducted utilizing recently published U.S. NRC training material on this subject. This review concluded that the simultaneous inoperability of the DCPP Unit 2 auxiliary building exhaust fans constituted a safety system functional failure.
F.
Operator Actions
None.
G.
Safety System Responses Plant operators restarted DCPP Unit 2 auxiliary building exhaust fan E-1 in safeguards mode by initiating a system reset and inserting a 'S' signal.
Ill.
Cause of the Problem A.
Immediate Cause Plant operators incorrectly caused the operating auxiliary building exhaust fan E-1 to secure on low flow with auxiliary building exhaust fan E-2 cleared for maintenance.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISION Diablo Canyon Unit2 0N5U0 0 0 1 3 2 3 0 0 0
o 1
. 0 10 4
o 5 TEXT B.
Cause
Operations personnel performing the work were using a partially marked up procedure and a clearance to take the E-2 Fan out of service to allow maintenance work on the system. The operators did not recognize the sequence of the process required the 'S' signal be selected prior to closing the dampers isolating flow to the fan.
IV.
Assessment of Safety Consequences
Under 10 CFR'50.73(a)(2)(v), "Any event or condition that alone could have prevented the fulfillment of the safety function of structures or systems that are 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."
This event was reviewed to determine if it meets the criteria for a safety system functional failure. Based on a review of the event, equipment in the same system, ABVS exhaust fans E-1 and E-2, were not operable and available to perform the required safety function. The design of these fans impacts subsections (C) and (D),
regarding control the release of radioactivity by filtering the exhaust stream and mitigate the consequences of an accident by maintaining the ESF room temperatures below the design limits, as cited above.
Although both DCPP Unit 2 ABVS exhaust fans were not operating, placing the unit into TS 3.0.3, the allowed outage time for this specification was not exceeded and the ESF features for this system were fully capable of performing their design safety functions. Based on the foregoing, this event is not considered risk significant and did not adversely affect the health and safety of the public.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISION NUMBER Diablo Canyon Unit2 0 50 0 0 3 2 3 2010 0
0 1
0 0
5 OFT5 TEXT V.
Corrective Actions
A.
Immediate Corrective Actions
- 1. DCPP Unit 2 exited TS 3.0.3 when plant operators restarted auxiliary building exhaust fan E-1 by initiating a 'S' signal.
B.
Corrective Actions to Prevent Recurrence (CAPR)
- 1. ABVS exhaust fan clearances have been updated to clearly show that a 'S' signal must be initiated prior to removing the associated ABVS exhaust fan from service.
VI.
Additional Information
A.
Failed Components None B.
Previous Similar Events
None.
C.
Industry Reports None.