Small tritium sample found in new monitoring well at Vermont Yankee

The groundwater monitoring process at Vermont Yankee continues with a total of 32 monitoring wells being sampled for tritium. Although the monitoring wells with tritium have shown a gradual overall reduction in concentration as the groundwater in that area has been pumped to the surface, this week Vermont Yankee received positive indications for tritium in a previously unaffected monitoring well located about 150 feet to the north of the area affected by the leak that was identified in January 2010.
The new positive level is at 9,200 pico curies per liter, a low level that is, in fact, well below regulatory reporting requirements.
However, Governor Peter Shumlin was not comforted by that fact and issued this statement: "Vermont Yankee notified my administration today of the new results, and the Department of Health is posting information on its website to help the public understand the situation. I am very concerned about this change at the Vermont Yankee site.
"Yankee officials are developing a plan to determine the cause of this elevated tritium detection and trying to determine whether it emanates from the plume associated with the leak previously discovered at the site, or instead is from a potentially new leak location.
"I look forward to quick and transparent action by Vermont Yankee."
The Department of Health was notified this morning by Entergy Vermont Yankee officials that a sample taken from groundwater monitoring well GZ-24S has been confirmed as being contaminated with tritium.
Groundwater monitoring well GZ-24S is a newer well completed and first sampled last November. GZ-24S is located 150-200 feet north of the bulk of the plume released from the Advanced Off-Gas (AOG) Building. ( Map )
The source of this tritium contamination is not yet known. Entergy Vermont Yankee is investigating possible sources of any new leaks, including four drain lines from the reactor and turbine building ventilation system, and one drain line from the AOG Building. Plant officials are also investigating whether other plant structures might serve as "conduits" of tritium contaminated water away from the estimated AOG plume area.
According to information provided to the Department of Health today by Entergy Vermont Yankee, the concentration of tritium in GZ-24S has been trending upward since late December. At that time, a sample taken from well GZ-24S tested at a concentration of approximately 2,500 picocuries per liter (pCi/L). A sample from that well taken January 20, 2011, had a concentration of about 9,000 pCi/L. On December 6, 2010, the only sample from well GZ-24S that was provided by Vermont Yankee to the Department of Health Laboratory for analysis tested at less than the lower limit of detection (LLD).
Entergy Vermont Yankee officials report that its on-site laboratory has not detected tritium above the LLD at groundwater monitoring wells near GZ-24S. However, a sample from well GZ-6 independently analyzed by the Department of Health Laboratory as well as by Entergy Vermont Yankee’s contract laboratory has tested for tritium slightly above the LLD. ( Health Department Lab Analyses )
Entergy Vermont Yankee is now sampling well GZ-24S daily. The Department of Health has requested split samples of GZ-24S to be provided weekly for analysis.
Vermont Yankee stated its technicians are working with engineers and hydrologists to investigate the cause of the elevated indication in this well.
The well was installed in November 2010 specifically for the purpose of monitoring for tritium. It is not a drinking water well and does not present a risk to public health and safety.
Groundwater extraction continues and a total of 314,300 gallons have been a pumped for above-ground storage, offsite transport and processing.
Source: Vermont Yankee; Vermont Department of Health 1.21.2011