05000323/LER-2011-001, For Diablo Canyon Regarding Unit 2 Reactor Trip from Loss of Main Feedwater Pump 2-1

For Diablo Canyon Regarding Unit 2 Reactor Trip from Loss of Main Feedwater Pump 2-1

ML11152A069
Person / Time
Site:	Diablo Canyon  (DPR-082)
Issue date:	05/25/2011
From:	Becker J Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-11-063 LER 11-001-00
Download: ML11152A069 (5)

LER-2011-001, For Diablo Canyon Regarding Unit 2 Reactor Trip from Loss of Main Feedwater Pump 2-1

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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
3232011001R00 - NRC Website

text

I.b'"e Pacific Gas and Electric Company J

James R. Becker Site Vice President Diablo Canyon Power Plant Mail Code 104/5/601 P2 0. Box 56 Avila Beach, CA 93424 805.545.3462 Internal: 691.3462 Fax: 805.545.6445 May 25, 2011 PG&E Letter DCL-1 1-063 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 10 CFR 50.73 Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 Licensee Event Report 2-2011-001-00: Unit 2 Reactor Trip From Loss of Main Feedwater Pump 2-1

Dear Commissioners and Staff:

In accordance with 10 CFR 50.73(a)(2)(iv)(A), Pacific Gas and Electric Company is submitting the enclosed licensee event report regarding the Diablo Canyon Power Plant Unit 2 reactor trip from the loss of main feedwater pump 2-1.

There are no new or revised regulatory commitments in this report.

This event did not adversely affect the health and safety of the public.

swh2/50384994 Enclosure cc/enc:

Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Alan B. Wang, NRR Project Manager James T. Polickoski, NRC Licensing Project Manager INPO Diablo Distribution J~2AC~

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)

, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Diablo Canyon Power Plant 05000 323 1 OF

4. TITLE Unit 2 Reactor Trip From Loss of Main Feedwater Pump 2-1

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED RV MNHDA YER FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NUMBER NO.

105000 FACILITY NAME DOCKET NUMBER 03 26 2011 2011 1 1 0

05 25 2011 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

E] 20.2201(b)

[

20.2203(a)(3)(i)

E] 50.73(a)(2)(i)(C)

[

50.73(a)(2)(vii) 1

[]

20.2201(d)

[

20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A)

[

50.73(a)(2)(viii)(A) fl 20.2203(a)(1)

[

20.2203(a)(4) 50.73(a)(2)(ii)(B) r] 50.73(a)(2)(viii)(B)

[

20.2203(a)(2)(i) fl 50.36(c)(1)(i)(A) 50.73(a)(2)(iii)

[

50.73(a)(2)(ix)(A)

10. POWER LEVEL

[

20.2203(a)(2)(ii)

E 50.36(c)(1)(ii)(A)

I]

50.73(a)(2)(iv)(A)

[

50.73(a)(2)(x) 9f 20.2203(a)(2)(iii)

Q 50.36(c)(2) 50.73(a)(2)(v)(A)

[

73.71 (a)(4) 98 20.2203(a)(2)(iv)

[

50.46(a)(3)(ii)

[]

50.73(a)(2)(v)(B)

[

73.71 (a)(5) 5 20.2203(a)(2)(v) 5 50.73(a)(2)(i)(A) 5 50.73(a)(2)(v)(C) 5 OTHER E] 20.2203(a)(2)(vi)

[J 50.73(a)(2)(i)(B)

[J 50.73(a)(2)(v)(D)

Specify in Abstract below or in G. Safety System Responses An automatic actuation of the auxiliary feedwater system, steam generator blowdown isolation, and main feedwater isolation occurred during the plant shutdown. These actuations were expected and all components functioned as designed.

III. Cause of the Problem A. Immediate Cause The local MFW Pump 2-1 electronic components were subjected to hot feedwater spray from a leaking relief valve. As a result, when MFW Pump 2-1 was subjected to the hot feedwater spray from the XS-2-RV-95 failed inlet flange gasket, a grounded circuit for low-low lube oil reservoir level [SJ] caused the MFW Pump 2-1 automatic trip.

B. Root Cause The preliminary root cause identified that Maintenance Procedure MP M-54.1, "Bolt Fabrication and Tensioning," allowed the fasteners for bolted connections using sheet type gasket material to be tensioned to "snug tight" versus providing specific bolt torque requirements. As a result, flange gasket preload has not been consistently applied when sheet type gasket material is used. The failed gasket for the relief valve was installed using this maintenance procedure.

IV. Assessment of Safety Consequences

The DCPP Unit 2 shutdown was normal and as expected following the automatic feedwater pump trip and subsequent manual reactor trip. The Solid State Protection System functioned as designed upon receipt of the manual reactor trip signal. The reactor trip breakers opened and all control rods and shutdown rods inserted as designed. The automatic auxiliary feedwater system actuation was expected with all system components fuctioning as designed. This Condition I event was within the bounds of the Updated Final Safety Analysis Report and the post trip transient response was as expected. As such, this event is not considered risk significant and it did not adversely affect the health and safety of the public.

V. Corrective Actions

A. Immediate Corrective Actions Plant operators initiated a manual reactor trip in accordance with OP AP-15 following the automatic trip of MFW pump 2-1.

B. Corrective Actions to Prevent Recurrence (CAPR)

Using the change management process, Maintenance Procedure MP M-54.1, "Bolt Fabrication and Tensioning," was revised to specify torque requirements for tensioning fasteners that are greater than one half inch on bolted connections, regardless of classification and use, with the exception of soft gasket material (e.g. rubber, Teflon, and Neoprene).

VI. Additional Information

A. Failed Components XS-2-RV-95 inlet gasket

B. Previous Similar Events

The XS-2-RV-95 inlet gasket had previously failed during a plant shutdown for refueling on October 26, 2004. This previous gasket failure did not produce a MFW pump trip or unit shutdown.

C. Industry Reports INPO Operating Experience Report OE 33263, Main Feedwater Pump Amphenol Connection Water Intrusion Results in Manual Plant Trip (DCPP2).