February 10, 2010
From Rob Williams
Vermont Yankee reported ground water monitoring well sample results for today. GZ-10 continues to have the highest concentration of tritium, at 2.28 million picocuries per liter (pCi/L). Test results from this well have fluctuated up and down around 2.2 to 2.6 million pCi/L since the well went into service February 6.
Tritium concentrations in two other wells appear to be trending upward. GZ-7 is now reporting at 937,000 pCi/l, and GZ-14 is at 93,000 pCi/l. GZ-4 tested at 2,792 pCi/l, GZ-3 tested at 38,427 pCi/l, and GZ-12 tested at 22,636 pCi/l. These also appear to be trending higher as compared with previous days.
However, these are still relatively small numbers of samples from each well, and trends will only be reliable once many more samples are tested from each well.
All other wells – GZ-1, GZ-2, GZ-5, GZ-6, GZ-9, GZ-11, GZ-13, the COB, PSB and Main drinking water wells, and the Connecticut River have tested negative for tritium. Well GZ-8 is drilled but dry, and therefore not being sampled. No nuclear plant-related radionuclides were identified in the gamma spectroscopy of all of the above samples.
According to Vermont Yankee, excavation near the Advanced Off-Gas (AOG) drain line and other piping of interest has been completed to 4 feet in depth. Futher excavation is now on hold while comprehensive safety analyses are being made. Some limited work may begin again tomorrow, with possible excavation down to 10 to 15 feet beneath the surface on Friday and Saturday.
Inspection of the AOG pipe tunnel by boroscope and robotics continued today. Results are still inconclusive. The AOG pit sump continues to be evaluated for evidence of leaks in to the pit.
Three new wells, GZ-15, GZ-16 and GZ-17, are planned to be drilled around the AOG Building. These are intended to better understand the nature of the tritium plume and the nature of groundwater flow on site.
