05000348/FIN-2013002-02
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Finding | |
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| Title | Unit 1 Solid State Protection System Modifications |
| Description | The inspectors identified an URI associated with the implementation of the licensees process to comply with 10 CFR 50.59 for a digital modification of the solid state protection system (SSPS) logic and control boards. This item remains unresolved pending further review by the NRC staff. The SSPS logic and control boards provide the coincidence logic to produce actuation signals for operation of the reactor protection system (RPS) and the engineered safety features actuation systems (ESFAS). Design Change Package 1071563201, Unit 1 Solid State Protection System Modification 1R24, Version 4.0, evaluated a digital modification to the existing SSPS logic and control boards. This modification replaced existing obsolete printed circuit boards (PCBs) with replacement boards supplied by Westinghouse. The modification replaced universal logic PCBs, safeguards driver PCBs, undervoltage driver PCB, and semi-automatic tester PCB in Unit 1. The original circuit boards used fixed logic devices (i.e. transistor-transistor logic) whereas the replacement circuit boards used programmable logic devices (i.e. complex programmable logic devices (CPLDs)) to perform the required logic operation for the design function of the SSPS. The licensee performed a 50.59 screening for this modification in accordance with procedure NMP-AD-010. This procedure stated that its purpose was to describe the process for compliance with the requirements of 10 CFR 50.59 using the guidelines contained in NEI 96-07, Guidelines for 10 CFR 50.59 Evaluations, Revision 1. The procedure included the screening questions to be used to determine whether a plant change required an evaluation against the criteria in 10 CFR 50.59(c)(2). Procedure NMP-AD-010, Section 6, directed the user to refer to NEI 96-07, Revision 1 and NEI 01-01, Guideline on Licensing Digital Upgrades, Revision 1, for additional guidance on how to answer the screening questions. Section 4 of NEI 96-07, Revision 1, stated that a 10 CFR 50.59 evaluation is required when a change adversely affects the design function or the method of performing or controlling a design function. The guidance also states that an example that would require an evaluation is a change that introduces a new type of accident or malfunction. The guidance also states that if a change has both positive and adverse effects, the change would require a 50.59 evaluation and should focus on the adverse effects. Additionally, NEI 01-01, Revision 1, Section 4.3.2, stated that most digital upgrades to redundant safety systems should be conservatively treated as adverse and should require an evaluation. This section also states that some examples of adverse effects that should be evaluated are those that change functionality in a way that increases complexity and introduces different behavior or potential failure modes. The licensee concluded in their 50.59 screening that the replacement of SSPS cards did not require an evaluation against the criteria in 10 CFR 50.59(c)(2), because the modification did not adversely affect the function of the SSPS as described in the UFSAR. The basis for that conclusion consisted, in part, of the following statements in the 50.59 screening: The Westinghouse-recommended SSPS replacement circuit boards (CPLD-based circuit boards) for the PCBs had been demonstrated to be a suitable replacement for the existing PCBs. The CPLD-based circuit boards were an equivalent form, fit and function replacement that contained no software (programmable code) and would not decrease the reliability of the SSPS. The main CPLD operated as a fixed logic device. The boards were not susceptible to software common mode failure, were fully testable, and were not considered digital upgrades. Existing SSPS redundancies, automatic actuation, system interactions (including testability), input and output signal levels, response times, seismic and environmental qualification were not adversely affected by the replacement boards. For the safeguards driver, universal logic, and undervoltage driver boards, although most of the failures had low probability of occurrence and low impact, there were certain board failures that could cause inadvertent equipment actuations and/or safety equipment inoperability. However, the risk of failure was comparable to that of the original-design circuit boards. The replacements continued to provide the coincidence logic to develop reactor trip and ESFAS signals. The inspectors reviewed the 50.59 screening and Westinghouse supporting information for the replacement cards and indentified various issues of concern associated with the design, testing, and operation of the replacement circuit boards, which could represent adverse effects to the design function of the SSPS as described in the UFSAR. These potential adverse effects would have required an evaluation against the criteria in 10 CFR 50.59(c)(2) as directed by site procedure NMP-AD-010, and the self-imposed NEI guidance (NEI 96-07 and NEI 01-01). This issue remains unresolved pending NRC review of additional information to be provided by the licensee to address the five concerns described above, in order to determine the adequacy of the licensees 50.59 screening and whether or not the issue represents a violation of 10CFR 50.59, Changes, Tests, and Experiments. The licensee entered this issue in the corrective action program as CR 606581 to address operability of the SSPS and evaluate the need for a 50.59 evaluation. The licensee completed a prompt determination of operability (PDO). The resident inspectors reviewed the operability determination and did not identify any issues regarding the operability of the SSPS cards. This issue is being tracked as a URI 05000348/2013002-02; Unit 1 Solid State |
| Site: | Farley  |
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| Report | IR 05000348/2013002 Section 1R17 |
| Date counted | Mar 31, 2013 (2013Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.17 |
| Inspectors (proximate) | J Rivera-Ortiz W Loo M Speck M Coursey T Chandler T Lighty J Sowa C Dykes T Su D Berkshirea Nielsenj Rivera K Miller P Niebaum S Sandal T Su J Panfel |
| INPO aspect | |
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Finding - Farley - IR 05000348/2013002 | |||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Farley) @ 2013Q1
Self-Identified List (Farley)
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