Mar 13 - Brattleboro Reformer



By Bob Audette, Brattleboro Reformer, Vt.

The condensate storage tank at Vermont Yankee nuclear power plant may be inspected a third time to determine if it is leaking tritiated water into the ground under the plant.

Yankee engineers are evaluating whether ultrasonic testing or a visual observation of the tank floor is needed, according to the Vermont Department of Health's daily update posted on its Web site.

The floor of this 500,000-gallon tank of radioactive reactor water was last inspected and repaired in 1993, stated the DOH.

 A condensate storage tank is used to store excess condensate and water as an emergency water source in case of a loss-of-coolant accident in a boiling water reactor. The tank is considered to be a safety-related component.

Yankee engineers also plan to test two underground pipes located beneath the foundation of the off gas building for their structural integrity, stated the DOH.

Meanwhile, an inspection of the plant's off gas system conducted through the use of a remotely operated vehicle concluded Thursday. The inspection revealed that two hydrogen recombiner trap drain lines are the only leaking components inside the tunnel, stated the DOH.

The recombiners oxidize hydrogen which is produced in the reactor when water is turned into steam. Recombining the hydrogen with oxygen produces steam and reduces the concentration of hydrogen to minimize the possibility of a hydrogen explosion.

While Yankee has not

yet confirmed that the "B" drain line is responsible for the tritium leak, it has confirmed that a crack found at the point where the line connects to the off gas pipe tunnel is the only leakage pathway to the environment found at this time.

Because the "B" pipe is in a place where it cannot be isolated, it will be kept in service until an upcoming refueling outage, which is scheduled for April 24 through May 19, according to statements made during Central Vermont Public Service's 2009 third quarter earnings call.

Existing leakage from the "B" line is being routed by the off gas pipe tunnel floor drain to the pit sump. From there it is pumped through underground pipes to the radioactive waste building for re-use, stated the DOH.

The leak in the "A" drain line was isolated and stopped on Feb. 14.

Plans to modify both pipes are being made to provide for a "leak-free path" to the off gas drain tank, stated the DOH, and "Some kind of leak monitoring method is being considered for the off gas pipe tunnel."

In addition to providing an inventory of other inaccessible pipe tunnels and other floor drains that must be checked for clogging, the DOH has also asked Yankee for a list of the inspection and remediation status of the 41 underground pipe systems that carry radioactive reactor water.

The drilling of the last monitoring well started on Thursday. It is located near the Connecticut River and is in the centerline of the plume.

Yankee may also drill an extraction well, to pump out contaminated water from the ground if Entergy chooses to clean up the tritium plume in this manner, according to the DOH.

Testing of on-site and off-site drinking water well samples, as well as water taken from the Connecticut River, continue to show no tritium in excess of the lower limit of detection, stated the DOH.

Bob Audette can be reached at raudette@reformer.com, or at 802-254-2311, ext. 273.

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