first_imgAs of today, Vermont Yankee reports that the refueling and maintenance outage is in Day 24 and work activities continue to noticeably wind down. Work at the cooling towers involving the third (and final) phase of the cooling tower upgrades continue, and the safety-related section of the west tower is complete. Also complete is the replacement of service water piping to “A” Emergency Diesel Generator and the routine cleaning of the intake bays.VY completed leak testing of tubes in the main condenser through the use of specialized “dimple” plugs, designed to identify even the smallest of leaks.  The source of power for the outage was transferred to the main transformer.  This allowed the next phase of work on the new Vernon Substation to commence.Preparations for start up continue on the refuel floor. The reactor pressure vessel has been reassembled and is being pressure tested today. In conjunction with this test, control rods will be tested. Tomorrow, the Integrated Leak Rate Test of the primary containment will be started. The test involves pressurizing the primary containment and then measuring the leakage rate or pressure drop over a several hour period.The test of the Emergency Core Cooling System was successfully conducted on Sunday, and all of the Emergency Core Cooling Systems responded as expected, but an unanticipated action occurred during the test. The initiating conditions for the test set the water level higher than normal in the reactor vessel. When the test began and steam valves automatically realigned, some of the excess water (above the steam lines) drained through a steam line to the torus which contains a back up supply of cooling water and is located in the reactor building. According to VY, there were no safety consequences and the incident was not immediately reportable. Still, plant management has taken steps to ensure this is not repeated in future tests. VY has also shared the issue with other nuclear plants. The steam lines will be drained and verified free of moisture.Work on the soil remediation from the tritium leak continued through the outage and is on schedule to be completed in the coming weeks. The rerouting of steam trap piping from the Advanced Off Gas system is complete and the reachable areas of the AOG pipe tunnel have been cleaned.The final stage of the outage will be switching and valve alignment of plant systems from their maintenance mode to their normal operations mode, and conducting final tests in preparation for start up. Once the plant is phased back on the grid, it will take several days to achieve full power. The outage is not considered over until the plant reaches 100 percent power. The staff will continue to test and monitor plant systems during the power ascension.Source: Vermont Yankee. May 18, 2010last_img