05000254/FIN-2013003-04
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Finding | |
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| Title | Question Concerning Availability of Dam Following a Seismic Event |
| Description | The inspectors identified an unresolved item (URI) concerning the assumed availability of Lock and Dam No.14 following a design bases earthquake event. In a letter dated November 6, 1970 to the U.S. Atomic Energy Commission (now NRC), Commonwealth Edison (the licensee) addressed questions regarding the capability of the intake flume to withstand a seismic event. Specifically, the question stated: Demonstrate that the intake flume for plant cooling water either meets the seismic design requirements for a Class I structure or cannot fail in such a manner as to isolate the plant from the river cooling water source [emphasis added] in the event of a design basis earthquake. In response to Question 2.7, the licensee stated the retaining wall structure would remain intact during an operational bases earthquake and design bases earthquake. In addition, the licensee stated the earth embankment was found capable of resisting the sliding effects during a DBE. Lastly, the licensee stated the crib house would not fail and isolate the plant from the river water source. The design basis earthquake (DBE) at Quad Cities is 0.24g maximum horizontal ground acceleration coupled with other appropriate loadings to provide for containment and safe shutdown. The operating basis earthquake (OBE) is 0.12 g maximum horizontal ground acceleration. In 1998, the licensee contracted Ashton Engineering to determine the failure modes of Lock and Dam No. 14. In April 1998, Ashton Engineering provided the licensee with its conclusions, as documented in Study of Mississippi River Water Stage at Quad Cities Nuclear Power Station for Commonwealth Edison Company. The report cites the dam is located in Uniform Building Code (UBC) Seismic Zone 0 and therefore, design guidelines for the dam do not require evaluation for postulated earthquake loadings. The report does conclude the most likely damage during a seismic event would be a loss of the dam gate operating capability; however, the magnitude of the seismic event is not cited. Question 2.7 implies the river is considered available during a DBE event even though the downstream dam is not designed or constructed to remain functional during the assumed DBE. Although the site appears to be within their licensing bases (assume availability of the river during a DBE), the inspectors questioned whether this assumption considered actual potential consequences, i.e., the need to assume a loss of dam during a seismic event. This concern is considered an Unresolved Item (URI 5000254/2013003-04; 05000265/2013003-04, Question Concerning Availability of Dam Following a Seismic Event.) pending further consultation with the Office of Nuclear Reactor Regulation. |
| Site: | Quad Cities  |
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| Report | IR 05000254/2013003 Section 1R07 |
| Date counted | Jun 30, 2013 (2013Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.07 |
| Inspectors (proximate) | A Dahbur C Mathews J Cassidy J Neurauter K Carrington K Stoedter M Domke M Garza R Murray V Meyersb Cushmanc Lipa C Mathews D Szwarc G O'Dwyer J Bozga J Mcghee L Jones R Langstaff S Bell |
| INPO aspect | |
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Finding - Quad Cities - IR 05000254/2013003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Quad Cities) @ 2013Q2
Self-Identified List (Quad Cities)
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