According to a statement from Entergy Vermont Yankee Sunday night, the source of the tritium leak has not yet been definitively identified nor has the status of the situation changed much at the Vernon site. Vermont Yankee engineers and technicians continue their investigation into the source of tritium in the plant s groundwater.
The last inspection of the Advanced Off Gas concrete pipe tunnel using a boroscope revealed little change in conditions over the past week. Any water in the tunnel continues to be collected in a sump and removed. Plans continue to test for leakage paths to the ground from the tunnel floor using pure water. This will help determine if and where the tunnel theoretically may be leaking water into the ground. This test will be performed after excavation exposes the tunnel floor so that technicians might be able to observe any leakage paths. Water used during the test will be collected and processed through plant systems.
Tritium concentration monitoring is ongoing. Contingency plans to relocate well (GZ-10) located in the excavation area are underway in the event that the excavation affects the ability to use this well.
Engineers and vendor experts approved the design of the engineered shoring for excavation work yesterday and excavation in the AOG area commenced last night. The design assures protection for workers and accounts for nuclear safety. As the excavation proceeds, shoring is being installed to hold back the dirt wall to prevent the possibility of a cave in. As of noon today, the excavation has reached the seven foot level. Sunday afternoon, workers expect to excavate down to 11 feet. At that point, excavation will stop temporarily so that additional cross bracing can be welded in place. An engineered solution to capture potential leakage encountered at the unearthed AOG tunnel has also been prepared if it is needed. The enclosure above the excavation area is in progress and will be completed after the shoring is moved into place and excavation has reached 15 feet.
The installation of the two new deep monitoring wells is complete and they are in the process of being developed (GZ-13D and GZ-14D). Digging for two additional shallow groundwater monitoring wells continues. The information from these new wells will help engineers and hydrology experts better understand groundwater flows beneath the site.
While this investigation continues, it is important to note that there has been no tritium levels found in any samples taken from drinking water wells or the adjacent Connecticut River.
For more details on the tritium investigation, the Vermont Department of Health has a thorough status report on the investigation at this web link: http://healthvermont.gov/enviro/rad/yankee/tritium.aspx
Source: Vermont Yankee. 2.21.2010
Vermont Yankee tritium leak still sought
Submitted by tim
on