05000387/LER-2012-001, For Susquehanna Steam Electric Station Unit 1, Regarding Both Control Structure Chillers Inoperable

For Susquehanna Steam Electric Station Unit 1, Regarding Both Control Structure Chillers Inoperable

ML12145A069
Person / Time
Site:	Susquehanna
Issue date:	05/23/2012
From:	Helsel J Susquehanna
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
PLA-6857 LER 12-001-00
Download: ML12145A069 (5)

LER-2012-001, For Susquehanna Steam Electric Station Unit 1, Regarding Both Control Structure Chillers Inoperable

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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
3872012001R00 - NRC Website

text

Jeffrey M. Helsel Nuclear Plant Manager U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop OP1-17 Washington, DC 20555-0001 PPL Susquehanna, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3510 Fax 570.542.1504 jmhelsel@ pplweb.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-387/2012-001-00 LICENSE NO. NPF-14 PLA-6857 Docket No 50-387 Attached is Licensee Event Report (LER) 50-387/2012-001-00. The event involved both control structure chillers being inoperable at the same time resulting in a condition that could have prevented the fulfillment of a safety function and is being reported in accordance with 10 CFR 50.73(a)(2)(v). The condition is also reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.

There were no actual consequences to the health and safety of the public as a result of this event.

ulatory commitments are associated with this LER.

Attachment: LER 50-387/2012-001-00 Copy:

NRC Region I Mr. P. W. Finney, NRC Sr. Resident Inspector Mr. R. R. Janati, DEP/BRP Ms. C. J. Sanders, NRC Project Manager TM

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

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

3. PAGE Susquehanna Steam Electric Station Unit 1 05000387 1 OF4

4. TITLE Both Control Structure Chillers Inoperable

5. EVENT DATE

6. LEA 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 Susquehanna Steam Electric Station Unit 2 05000388 65 J3 FACILITY NAME DOCKET NUMBER 02 16 2012 2012

- 001

- 00 2012 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 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)

10. POWER LEVEL D 20.2203(a)(1)

D 20.2203(a)(4)

D 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) 99%

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)

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) 0 OTHER D 20.2203(a)(2)(vi)

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

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

Specify in Abstract below or in Failure Analysis 2012

- 001

- 00

3. PAGE 30F4 The failed ball-joint connector (guide vane end) was removed and sent to the Hazleton Chemistry Lab for material analysis. The opposite un-failed ball-joint connector (guide vane motor end) was also sent to the Lab. The Materials Lab Report noted the following:

The connector failure was due to cyclic fatigue. No pre-existing defect was found that acted as an initiator for the fatigue cracking.

Corrosion deposits observed on the bolt indicate the ball-and-socket is not as free to move, binding up, and transferring higher than desired loads to the narrow neck region of the bolt.

The fatigue failure is not fabrication related.

The unbroken connector also showed a small crack in the same area as the broken connector. The unbroken connector was also in the process of failing by fatigue.

It is likely that other ball-joint connectors are experiencing the same failure mechanism.

Two observations were made regarding the ball-joint connectors on the "B" CS chiller relative to this event:

The broken ball-joint connector was painted with light green paint typical of Carrier chillers. Hence, it is very likely the ball-joint connectors on the "B" CS chiller were never replaced and part of the original equipment.

With regard to the corrosion deposits observed on the ball-and-socket portion of the connector, the corrosion limited the free movement of the connector causing mechanical binding of the guide vane linkage. In turn, the binding of the guide vane linkage transferred higher than desired loads and stresses to the narrow neck region of the bolt initiating I accelerating the fatigue failure.

A chiller preventive maintenance (PM) review was performed and determined the ball-joint connectors are not currently replaced on any PM frequency. Hence, one of the primary causes of the failure was simply due to the age of the connector. The failed connector on the "B" CS chiller had been in-service for over 30 years contributing to the buildup of corrosion and subsequent fatigue failure over this service period.

CAUSE OF THE EVENT

The direct cause of the ball-joint connector failure was cyclic fatigue.

The apparent cause of the failure was determined to be cyclic fatigue initiated /accelerated by corrosion of the ball-joint connector.

ANALYSIS/SAFETY SIGNIFICANCE

Actual Consequences:

The chiller guide vanes regulate chiller load. As chiller load increases/decreases, the guide vanes open/close to maintain the chilled water outlet temperature at a setpoint. With the guide vane linkage broken, the "B" CS chiller would be unable to regulate itself to changing load conditions. The "B" CS chiller operated for approximately 2 days with its guide vane linkage broken until the "A" CS chiller was placed in-service on February 18, 2012. During this two day period, the "B" CS chiller operated at constant load. Due to minimal changes in chiller demand, the cooling load provided by the "B" CS chiller was sufficient to maintain CS room temperatures within normal operating bands.

Potential Consequences:

3. PAGE 40F4 During the period the guide vane linkage was broken, the "B" CS chiller was able to provide some minimal cooling load; however, the chiller would not be able to respond to changing load conditions. Consequently, the chiller was not capable of operating at design conditions considering the following changes in chiller load conditions:

ESW operation (higher condenser temperature than SW)

CREOASS operation (additional heat load)

LOCA conditions (additional heat load)

CORRECTIVE ACTIONS

The following are the key corrective actions associated with this issue:

1. The broken ball-joint connectors on the "B" CS chiller were replaced.

2.

The mechanical ball-joint connectors on the guide vane linkage will be replaced on other applicable chillers.

3.

Replacement of the ball-joint connectors on the chiller guide vane linkage will be included as a preventive maintenance activity for the "B" CS chiller and other applicable chillers.

4.

A root cause analysis on chiller reliability is in progress.

PREVIOUS SIMILAR EVENTS

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