05000454/FIN-2015007-04
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Finding | |
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| Title | Potentially Inadequate Evaluation/Corrective Actions: Diesel Oil Storage Tank (DOST) Vent Line Seismic Supports and Tornado Missile Protection |
| Description | The inspectors identified a concern that the licensees evaluation and corrective actions may have been inadequate following identification that DOST vent lines may not be seismically supported and adequately protected against tornado missiles as described in the Updated Final Safety Analysis Report (UFSAR) and in an NRC Safety Evaluation Report (SER). The deficient condition was NRC-identified and documented as an NCV in NRC Inspection Report 05000454/2009004-02; 05000455/2009004-02, which was issued in 2009; and was entered into the licensee CAP as AR 877430877430and AR 933712933712 According to the description in UFSAR Section 9.5.4.2, although the DOSTs are safety-related tanks required to remain operable during a tornado event, the tank fill and vent lines are classified as nonsafety-related. In response to an NRC reviewer comment during the license application process that these lines should be designed safety-related and tornado missile protected, the licensee provided a formal response which included, in part, the following (Question 040.99, Commonwealth Edison letter from T. R. Tramm to Harold R. Denton, dated December 28, 1981): Additional supports will be added to maintain integrity of the lines during design basis seismic events; Fill and vent lines are not safety-related while the tanks are; Impact from a tornado missile will not result in loss of function as breakage will occur before crimping; In the event of damage, a capped off 4 Category I line could be opened for use as an emergency vent or fill line; and A 4 Category I tank overflow line could be used as a vent. This position was accepted by the NRC based on the following as documented in the SER (NUREG 0876, February 1982, Section 9.5.4.2): Commitment to seismically support the fill and vent lines; In case of damage due to tornado missiles, availability of unused flanged connections that can be used as fill and vent openings; and the Lines are designed to American National Standards Institute (ANSI) B31.1 Following a review of available licensee documentation, the inspectors identified that the commitment for seismically supporting the vent lines may not have been met. The availability of the unused flanged connections was also uncertain as there were no administrative procedures in place for such actions. The licensee was also unable to justify the break prior to leak statement. Instead, the licensee was relying on the vent path through the overflow line as was discussed in the response to Question 040.99 above. Because of the loop seals in the overflow piping, additional evaluations and loop seal modifications were performed to demonstrate that the tanks were structurally adequate for the maximum vacuum associated with the loop seal configurations. The code of construction for the tanks was the American Society of Mechanical Engineers (ASME)Section III, Division 1, sub-section ND, 1974 edition. However, due to a partial vacuum resulting from the use of overflow piping as a vent path, the use of a methodology that was different than that described in licensee calculation BYR13096 was required. Based on discussions with the licensee, the licensees view is that since the alternate vent path is provided, the vent lines no longer require seismic supports. The inspectors interpretation based on the SER, UFSAR, and the licensee response to the NRC question as described above is that the acceptance of the alternate vent path scenario was applicable to the tornado missile event only, and that the licensee was still required to seismically support the vent lines. Additionally, while the licensee response to Question 040.99 included a discussion of using overflow lines as alternate vent paths, the NRC acceptance was based on the use of unused flanged lines. Further review is needed to determine the correct interpretation of the SER description and the design basis for seismic support and tornado missile protection requirements for the DOST vent lines. This issue will remain open pending further NRC review to ensure that the licensee is in compliance with their current licensing basis. (URI 05000454/2015007-04; 05000455/2015007-04, Potentially Inadequate Evaluation/Corrective Actions: Diesel Oil Storage Tank (DOST) Vent Line Seismic Supports and Tornado Missile Protection) |
| Site: | Byron  |
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| Report | IR 05000454/2015007 Section 4OA2 |
| Date counted | Sep 30, 2015 (2015Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | B Palagi C Thompson E Duncan J Benjamin J Draper V Meghania Shaikhb Palagi C Thompson G Hansen J Cassidy J Draper J Jandovitz J Mcghee L Smith M Holmberg V Meghani |
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Finding - Byron - IR 05000454/2015007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2015Q3
Self-Identified List (Byron)
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