05000498/LER-2017-001

From kanterella
Jump to: navigation, search
LER-2017-001, Unit 1 failure of a timing relay during a Technical Specification surveillance
South Texas Unit 1
Event date: 03-10-2017
Report date: 05-11-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4982017001R00 - NRC Website
LER 17-001-00 for South Texas, Unit 1, Regarding Failure of a Timing Relay During a Technical Specification Surveillance
ML17131A353
Person / Time
Site: South Texas STP Nuclear Operating Company icon.png
Issue date: 05/11/2017
From: Connolly J
South Texas
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-17003479, STI: 34494823
Download: ML17131A353 (9)


I. Description of Event

A. Reportable event classification

Since Technical Specification 3.3.2, Action 20A was not met, this event is reportable under 10 CFR 50.73(a)(2)(i)(B).

B. Plant operating conditions prior to event

Prior to the event at 1045 on March 10, 2017, Unit 1 was operating in Mode 1 at 100 percent power.

D. Narrative summary of the event

During a Technical Specification surveillance, the as-found operating time (3.295 seconds) of a timing relay (Undervoltage Agastat Timing Relay, model number ETR14D3A004, made by TE Connectivity, system identifier EB, component identifier 62), installed in a safety related 4160 kV switchgear, was greater than the Technical Specification allowable value equal to or less than 1.93 seconds. The performers of the surveillance measured the as-found test value and it was greater than the Technical Specification allowable value. The Control Room Unit Supervisor consulted with the Electrical Maintenance Supervisor and directed the performers to adjust the relay component as allowed by the procedure, and continue with the test.

C. Status of structures, systems, and components (SSCs) that were inoperable at the start of the event and that contributed to the event Before continuing the surveillance, an inspection of the testing equipment was performed to ensure the equipment was functioning correctly. No issues were found and no changes were made to the testing equipment. The maintenance personnel retested the relay timing, without adjustment, and the result was 1.902 seconds. Due to the change in value, an additional test was performed with a result of 1.766 seconds, which was within the prescribed as-left procedure acceptance criteria of 1.715 to 1.785 seconds. Additional re-tests were performed with the same results, (i.e., a value of 1.766 seconds) obtained. Contrary to Control Room Unit Supervisor's directions, during relay retesting, no adjustments were made to the timing relay.

The Surveillance Test was completed and logged as satisfactory at 1202 on March 10, 2017, and the component was declared Operable.

Other than the undervoltage relay being tested, there were no other systems, structures, or components that were inoperable at the start of the event that contributed to the event.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

The failed relay was determined to be inoperable per Technical Specifications for approximately

99 hours
0.00115 days
0.0275 hours
1.636905e-4 weeks
3.76695e-5 months

prior to discovery. The failed component was discovered as a result of reviewing surveillance test results. Following discovery, the relay was replaced and the channel declared operable within

24 hours
2.777778e-4 days
0.00667 hours
3.968254e-5 weeks
9.132e-6 months

. Based on the last successful surveillance test, the last time the equipment was determined to be capable of performing its safety function is September 22, 2016.

E. Method of discovery

On March 14, 2017, an STP engineer completed a review of the condition report documenting the surveillance test for the relay and determined that the relay reliability was questionable. This was based on the relay timing found outside Technical Specification limits and returned to Operable status with no adjustments. The Control Room was contacted and, based on the System Engineer's analysis, the Unit 1 Shift Manager determined that the relay should not have been declared Operable on March 10 and declared it inoperable on March 14, 2017 at

1500 hours
0.0174 days
0.417 hours
0.00248 weeks
5.7075e-4 months

. Technical Specification 3.3.2, Action 20A, was entered.

C. Safety Consequences and Implications of the Event During the event, the condition of the system was in a 2 out of 4 logic scheme. Protection for an under voltage condition remained intact for a 2 out of 3 logic, and thus maintained the safety function of the system. If an actual undervoltage condition occurred, the other relays would have performed as designed.

The Shift Manager determined that the relay should have remained Inoperable on March 10 until replaced. Technical Specification 3.3.2, Action 20A, requires the channel to be placed in the tripped condition within

72 hours
8.333333e-4 days
0.02 hours
1.190476e-4 weeks
2.7396e-5 months

. The failed undervoltage timing relay was subsequently replaced, satisfactory completion of surveillance test was performed, and the component was declared Operable.

The event was of very low risk significance and no radioactive release occurred; therefore, there was no adverse effect on the health and safety of the public.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

III. Cause of the Event

Based on the conditions identified and using information collected during discussions with the relay manufacturer subject matter expert, the cause of the component failure is not known. The relay was retained following the event, and inspected with satisfactory results. The failure could not be recreated, and the failure mode and mechanism is not known.

The causes for the event were the following:

The Electrical Maintenance Supervisor did not exhibit sufficient questioning attitude when consulted on this task. The relay did not exhibit the reliability to perform within limits through the next surveillance interval, and this was not recognized. Though the electricians did request clarification from the supervisor as expected, a proper questioning attitude from the supervisor would have determined that further expertise was needed to proceed. In addition, a misinterpretation of the procedure allowed the actions as performed, but the procedure intent was not maintained.

The start of this event consisted of the undervoltage relay as-found operating time being outside the Technical Specification required value. After retesting, the surveillance test timing improved as observed in subsequent retests. The failed condition could not be recreated upon further testing.

In addition, the Control Room staff displayed an inadequate questioning attitude regarding the adverse performance of the relay. When the information was shared with the Control Room that no adjustment was made to the timing relay, both individuals should have confirmed adequate information was collected to ensure that it was appropriate to proceed with closing out the surveillance rather than simply agreeing with the results of the completed test.

1. Unidentified Material Condition with the failed component (i.e. relay) 2. Less than adequate questioning attitude by Electrical Maintenance Personnel 3. Less than adequate questioning attitude by Operations Personnel - 00 2017 - 001

CONTINUATION SHEET

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

IV. Corrective Actions

The Table 1 below contains the corrective actions planned as a result of the event:

Table 1: Corrective Actions Corrective Actions Description Status 1 Relay was replaced and Surveillance Test completed Satisfactory. (Relay replaced by PM WAN 560042) Complete 2 Perform one on one sessions with EM personnel involved in this event to determine the reason for the shortfall on questioning the reliability of the subject relay device and any other corrective actions required to include coaching opportunities.

Complete 3 Perform coaching session with individuals involved to ensure clear understanding of 0POP01- ZO-0011 procedure requirements In process 4 Discuss event and refresh on procedure requirements of 0POP01-ZO-0011 with all Licensed Operations Personnel In process comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

V. Previous Similar Events

A review of similar events at STP was performed by reviewing the STP Corrective Action Program and Licensee Event Reports submitted for the previous 10 years. The review concluded that there have been many occurrences where the as-found condition of this or similarly functioning timing relays were found out of acceptance criteria or outside Technical Specification criteria. However all events involved the old model E7000 timers. It is important to note that the older model relays are diaphragm type designs, while the new relay timers are solid state designs. Since these timers were replaced (starting in 2012) this condition is the first case of its kind. In all occasions identified, the proper notifications and corrective actions were performed.

VI. Additional Information

The discovery date is March 14, 2017 when Unit 1 discovered the need to perform a reportability evaluation on the event. The event date is March 10, 2014, the date when the relay failed to pass the surveillance test. The report date is May 11, 2017, within 60 days after discovery of the event, as required per 10 CFR 50.73(a)(1).

Dates and approximate times of occurrences:

3/10/17: Electrician requested Control Room staff to log surveillance as Satisfactory. Discussion held on steps performed. All involved were aware that no adjustment was made.

3/10/17 1045: Surveillance Test commenced for the Unit 1 E1B undervoltage relay (Relay declared inoperable for planned testing).

3/10/17: Electrician's initial as-found measurement (3.295 Seconds) of the timing relay was found outside Technical Specification and Acceptance Criteria (1.715 to 1.785 seconds) per procedure.

3/10/17: Electrician notification and discussion with Unit 1 Control Room Supervisor. Direction given to continue in accordance with procedure and make adjustments to within band (acceptance criteria).

3/10/17: Electrician's discussion with Electrical Maintenance Supervisor. Direction given to continue with test and document findings in Condition Report.

3/10/17: Electrician's retest of timing relay was performed. (Retest 1: 1.902 seconds, retest 2-9:

1.766 seconds). No adjustment was made. No issues identified with test equipment.

A search for License Event Reports was performed that focused on events deemed similar reportable under 50.73(a)(2)(i)(B). Several events were found to meet this criteria, but none were directly applicable to this event.

- 00 2017 - 001

CONTINUATION SHEET

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.