05000331/LER-2013-005
| Duane Arnold Energy Center | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3312013005R00 - NRC Website | |
I. Description of Event:
On June 21, 2013, while operating at 100% power, Temperature Indicating Switch (TIS) 4480 Channel 1, Turbine Building Main Steam Line 'D', was found to have spiked from 133F to 150F. Since the indication was within the acceptance criteria of> 70F and 3.0.0-01, Instrument Checks, the instrument was not declared inoperable. On June 22, 2013, TIS-4480, Channel 1 was again found to be indicating erratically. A review of TIS-4480 indications from May 5, 2013, indicated a trend was present. Therefore, TIS-4480 was declared inoperable on June 22, 2013. A Past Operability Review (POR) was not completed based on the conclusions of a previous similar event that occurred in December 2012, reference License Event Report (LER) 2013-004. On October 22, 2013, a POR was completed and concluded that TIS-4480 was inoperable from May 5, 2013 to June 22, 2013.
Technical Specification (TS) 3.3.6.1, Primary Containment Isolation Instrumentation, Required Action D.1, requires the associated Main Steam Line to be isolated within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Neither of these Required Actions were completed. Therefore, this condition constituted a condition prohibited by TS.
There were no other structures, systems or components inoperable at the start of this event that contributed to the event.
II. Assessment of Safety Consequences:
The safety significance of this event is low based on the fact that the other 7 Main Steam Line Isolation Channels were operable during the time TIS-4480 was inoperable.
Technical Specification (TS) 3.3.6.1, Primary Containment Isolation Instrumentation, Required Action D.1, requires the associated Main Steam Line to be isolated within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Neither of these Required Actions were completed. Therefore, this condition constituted a condition prohibited by TS and is reportable to the NRC pursuant to 10CFR50.73(a)(2)(i)(B).
This event did not result in a safety system functional failure.
III. Cause of Event:
A Root Cause Evaluation was completed. The evaluation identified the following root causes of this event.
Root Cause 1 — An undetermined failure internal to the TIS affected its ability to provide accurate temperature indications.
Root Cause 2 — Procedural guidance of STP 3.0.0.0-01, Instrument Checks, did not include a requirement to perform a qualitative channel check as required by TS.
IV. Corrective Actions:
On June 23, 2012, TIS-4480 was replaced and returned to service.
In order to address the root cause of this event, the following corrective actions will occur.
A modification will be developed and implemented to replace the current Chromlox TIS with Yokogawa Recorders or other suitable instruments.
STP 3.0.0-01, Instrument Checks, will be revised to clearly state that a qualitative assessment of instrument performance should be performed for ANY instrument included in the STP that is being assessed to meet its CHANNEL CHECK surveillance requirement, not just for cases when the specified quantitative assessment cannot be performed.
V. Additional Information:
Previous Similar Occurrences:
A review of License Event Reports from the past 5 years did not identify any similar occurrence.
EIIS System and Component Codes:
IM - Temperature Monitoring System.
Reporting Requirements:
This event is being reported as an Operation or Condition Prohibited by TS, 10CFR50.73(a)(2)(i)(B).