05000390/FIN-2017007-05
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Finding | |
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| Title | Potential Failure to Address Environmental Qualification of Barton Transmitters |
| Description | The inspectors opened a URI to review the adequacy of the licensees justification for the qualified life of Barton Model 764 differential pressure transmitters, documented in EQ binder WBNEQ-XMTR-001. Description: The inspectors reviewed EQ binder WBNEQ-XMTR-001 for Barton 764 differential pressure transmitters. The qualification standards of record were IEEE 323-1974 and NUREG 0588, Interim Staff Position on Environmental Qualification of Safety-Related Electrical Equipment, Revision 1. The pressure transmitters contain a cover and a housing O-ring that are specified to be replaced following calibration at least every two years to maintain qualification, and internal mineral oil seal O-rings for the sensor diaphragms that are not regularly replaced. The binder specified that the transmitter internal electronics and the O-rings were qualified for 40 years. The transmitters in question are in lower containment specified at 120F and exposed to the maximum accumulated ambient radiation absorbed dose of 2E7 Rad over 40 years. Westinghouse (WEC) aged the transmitters for a 0.5eV activation energy at 125C including the electronics inside and the O-rings. The 0.5eV activation energy was specified for conservatism to account for the known synergistic effects of simultaneous thermal exposure and radiation exposure. This synergism can be significant and was also identified as significant for the O-ring material in EQ NUREGs (e.g. NUREG/CR-3629, NUREG/CR-3588) and various research papers. During the 0.5eV EQ testing, WEC noted that the transmitter O-rings (all) failed at 1,673 hours0.00779 days <br />0.187 hours <br />0.00111 weeks <br />2.560765e-4 months <br />, which equated to less than six years of aging at 120F. Westinghouse chose a new activation energy (0.92eV) for the O-rings, but continued to use 0.5eV for the electronics. The transmitter oil seal O-rings were replaced with new ones. Then, the transmitters with the original electronics and new oil seal O-rings were aged for an additional 350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br />, while the cover and housing O-rings were only replaced with new ones during the final 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />. The inspectors evaluated the end of the accelerated aging processes for 120F. The inspectors noted that the electronics aging was accelerated to less than 7.5 years total at 0.5ev. The oil seal O-ring aging was accelerated to 22.6 years at 0.92eV. The cover and housing O-ring aging was accelerated to 11 months at 0.92eV. Further information from the licensee is needed to evaluate the justification for the 40-year qualified life of the transmitters. Specifically, the justification for the deviation from the original 0.5eV activation energy provided by WEC and the demonstration that synergistic effects and uncertainties were accounted for when deviating from this activation energy. This URI is opened to determine if a performance deficiency exists and it is identified as URI 05000390/2017007-05 and 05000391/2017007-05, Potential Failure to Address Environmental Qualification of Barton Transmitters. |
| Site: | Watts Bar  |
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| Report | IR 05000390/2017007 Section 1R21 |
| Date counted | Jun 30, 2017 (2017Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | E Stamm T Fanelli T Su J Bartley |
| INPO aspect | |
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Finding - Watts Bar - IR 05000390/2017007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Watts Bar) @ 2017Q2
Self-Identified List (Watts Bar)
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