05000321/FIN-2016008-04
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Finding | |
|---|---|
| Title | Potential departure from protection system design basis |
| Description | The inspectors identified a URI regarding the licensees compliance with the design bases for the Analog Transmitter Trip System (ATTS). On April 16, 2010, Unit 1 received an invalid emergency core cooling system (ECCS) LOCA signal on high drywell pressure due to a failed ATTS slave card that caused a voltage perturbation within a single panel. The licenses root cause identified that the ATTS panel design did not comply with channel independence (IEEE 279-1971 Section 4.6). A design change (SNC116736) separated the specific cards that caused the false trip. During the review of design change, the inspectors identified that the ATTS panel design for other cards also do not comply with channel independence. A single failure within the ATTS panels could result in an interaction that can cause a failure of two channels. The licensee has provided documentation related to the original submittal of the design to the NRC and the NRCs acceptance of the design. In addition, the UFSAR section 7.3.1.2, System Descriptions, for the ECCS stated, in part, Instrumentation and control are designed to establish that the following functions are met: A. Each instrument channel functions independently of all others. B. Sensing devices respond to process variables and provide channel trips at correct values. C. Sensors and associated instrument channels respond to both steady-state and transient changes in the process variable within specified accuracy and time limitations, and they provide channel trips at correct values even when affected by process variations that may extend grossly beyond the expected trip setpoint. D. Paralleled circuit elements can perform their intended function independently. E. Series circuit elements are free from shorts that can abrogate their function. F. Redundant instruments of logic channels are free from interconnecting shorts that could violate independence if a single malfunction should occur. There is not an immediate safety concern because no specific examples have been identified that would prevent an actuation from occurring. This URI is being opened to determine whether a performance deficiency exists and is identified as URI 05000321/2016008-04 and 05000366/2016008-04, Potential Departure from Protection System Design Basis. |
| Site: | Hatch  |
|---|---|
| Report | IR 05000321/2016008 Section 1R17 |
| Date counted | Jun 30, 2016 (2016Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.17 |
| Inspectors (proximate) | E Stamm J Bartley T Fanelli M Greenleaf |
| INPO aspect | |
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Finding - Hatch - IR 05000321/2016008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Hatch) @ 2016Q2
Self-Identified List (Hatch)
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