05000331/FIN-2010004-06
Finding | |
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| Title | Water Intrusion into Cable Vaults Containing Safety-Related Cables |
| Description | An Unresolved Item was identified by the inspectors for the licensees failure to promptly identify that water intrusion into the turbine building cable vault could have affected safety-related cables. Specifically, the licensee failed to identify and evaluate whether conduits containing safety-related cables were subject to water intrusion following discovery of water filling an adjacent conduit containing non-safety related cables in the same cable vault. In order to close this URI, the licensee needs to complete their evaluation to determine if the conduits containing safety-related cable were actually submerged
During the inspectors review of water intrusion issues since 2008, they noted several condition reports documenting water intrusion into the 1A2 non-essential switchgear room, the Turbine Building (TB) east corridor and cable vault, and several exterior manholes containing electrical cables. The NRC issued a Green NCV in IR 05000331/2009005 for failing to maintain safety-related cables in manhole 1MH109 in an environment for which they were designed. This was following an inspection of 1MH109 that found safety-related ESW cables submerged in water. As a result of this finding, the licensee performed CE 07853 and developed several corrective actions to prevent long term cable submergence at the station. Immediate corrective actions included dewatering the manholes; interim corrective actions included the development of periodic inspection work tasks to be performed in manholes that were subject to water intrusion. The periodic inspections were to take place until the final corrective actions could be implemented; including the installation of sleeve extensions (to raise the top of the manhole) to prevent water intrusion, and the installation of sump pumps Additional review by the inspectors noted that on October 23, 2009, the licensee generated CAP 070736 which documented the source of water intrusion found in the 1A2 non-essential switchgear room. There had been a trend of water seeping from underneath the 1A2 non-essential switchgear and pooling around the breaker cabinets in the room. Investigation revealed the water was coming through cable conduit K208 leading to the 1A210 breaker (General Service Water Pump 1P-89C). This conduit was traced back to the TB east cable vault and the cable was found to originate from manhole MH206. The licensee determined that as rain water would fill MH206, water would leak through the cable penetrations in MH206 and migrate to the TB east cable vault and 1MH109. As water entered the TB east cable vault, the water would enter open conduits below the penetrations and also fill the floor of the cable vault. The inspectors noted that CAP 070736 did not identify whether conduits containing safety-related cables were in the vault or if they had been filled with water According to corrective action (CA) 53855 for CAP 070736, the licensee had established an administrative limit of 6inches of accumulated rainfall to initiate a CR in order to inspect the condition of manholes MH206 and 1MH109, and dewater if necessary. The inspectors questioned the basis for the 6 of rainfall since it was not documented in the corrective action document. Review of all corrective action documents did not indicate what condition the licensee was intending to prevent (i.e., prevent safety-related cables in 1MH109 from becoming submerged or prevent non-safety related cables in MH206 from becoming submerged and therefore prevent water from entering the TB) On August 16, 2010, CR 573648 was initiated to document recent intense rains approaching the 6inch accumulated rainfall limit, and Work Request 94007646 was written to remove the manhole covers and inspect for water. On August 31, 2010, the inspectors identified water on the floor of the 1A2 switchgear room and the licensee wrote CR 577166 on September 1, 2010, which again identified the need to inspect manholes MH 206 and 1MH109 (since this was previously identified as the source of water into 1A2), and also noted that Work Request 94007646 had not yet been completed. On September 2, 2010, the manholes were inspected and revealed that MH206 contained approximately seven feet of water and 1MH109 contained approximately 6 inches of water. The licensee dewatered both manholes and dug a trench to help direct any new rainfall away from the lid of MH206 On September 9, 2010, the inspectors questioned the licensee whether the TB east cable vault contained any safety-related cables and what type of environment the cables were exposed to. The licensee wrote CR 579006 on September 10, 2010, to document potential standing water behind Door 112 which accesses the TB east cable vault. Inspection of the TB east cable vault on September 13, 2010 showed approximately two inches of water on the floor of the vault. The inspectors noted that water level in the vault likely had fallen since there was evidence of water seeping into the TB through the vault wall. There was additionally evidence of water streaking on the walls of the vault below the cable penetrations. The licensee noted in AR 579006 it is reasonable to assume that there may be water in some if not all of the conduits exposed to the water coming into the Turbine Building in this vault. The inspectors determined that there were two possible ways water was entering safety-related conduits. First, as water entered the vault at the cable penetration, it could spray into the open conduits located below the cable penetrations. Second, as water filled the bottom of the cable vault, it could submerge the conduit penetration on the floor and leak into the conduit The inspectors noted that by not performing the manhole inspections for two weeks after CR 573648 was written and as required by CA 53855 (documenting the need for the manhole inspections), additional rainfall was sufficient to allow for water intrusion into the TB east cable vault and 1MH109, and furthered the potential to submerge safety-related cables with water. The licensee has planned inspections of the conduits in the TB cable vault to identify if water had actually entered the conduits. These inspections are planned under WO 40046280. Once these inspections are completed by the licensee, the inspectors will be able to determine if a violation of NRC requirements exist and close this URI (URI 05000331/201004-06). |
| Site: | Duane Arnold  |
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| Report | IR 05000331/2010004 Section 4OA2 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | C Zoia K Riemer M Mitchell R Baker L Haeg R Walton B Cushman R Murrayk Riemerr Orlikowski J Cassidy M Mitchell M Phalen R Baker D Jones A Wilson L Haeg R Walton C Scott R Murray A Scarbeary |
| INPO aspect | |
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Finding - Duane Arnold - IR 05000331/2010004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Duane Arnold) @ 2010Q3
Self-Identified List (Duane Arnold)
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