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During Unit 2s most recent RFO, L2R15, maiDuring Unit 2s most recent RFO, L2R15, maintenance was performed on normally unisolable sections of the reactor recirculation system. To facilitate this maintenance, temporary seals were installed on the jet pumps inside the reactor vessel; however, three of the individual jet pump plug seals somehow became detached from the plug assemblies and were lost in the reactor. The first seal was lost on February 8, 2015, from the plug at the jet pump number 5 location as documented in AR 02449326. A potential safety concern was later identified by licensee personnel on February 11, as documented in AR 02450949. This AR stated that the seals could potentially block reactor coolant flow to peripheral fuel bundles, potentially leading to TS Safety Limits being exceeded. Two additional seals were lost on February 18 from the plug at the jet pump number 14 location, as documented in AR 02455054. These three seals were not successfully retrieved from the reactor vessel and the unit was restarted on February 26 with the lost seals still in the reactor. Unit 2 was held at approximately 22 percent power until March 15, 2015, when reactor recirculation pump speed was upshifted to reach approximately 50 percent power, and remained at this power level until March 25, when full power was achieved. These restrictions to power operation were to ensure that safety limits were not violated until testing and evaluation was completed to ensure the seals had degraded to a point that they would safely pass through the most limiting fuel support piece orifice. At the time of this report, the licensee was conducting a root cause evaluation to determine the causal factors that led to the loss of the three plugs. This issue is considered a URI pending the inspectors review of that root cause report to determine if a performance deficiency exists.ermine if a performance deficiency exists.  +
23:59:59, 31 March 2015  +
05000374  +
23:59:59, 31 March 2015  +
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00:52:54, 21 February 2018  +
23:59:59, 31 March 2015  +
Loss of Jet Pump Plug Seals during L2R15  +