Entergy Corporation today announced that a recently completed root cause analysis of a tritium leak at the Vermont Yankee Nuclear Power Plant determined that the leak was primarily caused by an earlier design deficiency and inadequate inspection of an underground area of the plant that could not be accessed.
Tonight (June 22, 2010), the Nuclear Regulatory Commission will host an open house (4 pm to 6 pm) and public meeting (6 pm to 9 pm) on June 22 at Brattleboro Union High School. NRC staff will discuss the NRC Demand for Information and Groundwater Protection reports, an annual assessment of Vermont Yankee, and other information about the Vermont Yankee tritium investigation and groundwater protection efforts.
The 74-page root cause analysis listed several concurrent contributing causes of the leak. Specifically, the plant s advanced off-gas (AOG) pipe tunnel was not accessible for inspection which prevented staff from identifying the two leaking AOG pipes and that the tunnel drain line was blocked with construction-related material left in the tunnel after work there in 1972. The blockage prevented the tritiated water from passing through the drain-line and into a tank. Subsequently, design and construction in 1978 of an unrelated pipe connected to the tunnel created a pathway into the ground. The leakage from the two AOG pipes into the tunnel was caused by internal corrosion.
The root cause analysis also found that Entergy Vermont Yankee did not fully implement groundwater protection measures recommended in a voluntary industry initiative. The analysis faulted an inadequate commitment by management to implement the initiative which created a lack of clearly defined organizational roles, responsibilities and program definition. The analysis concluded that the groundwater protection initiative, if fully implemented, may have prevented or led to more timely identification of the tritium leakage to the groundwater.
The self-critical root cause analysis was performed by a multi-disciplinary team lead by members of the Vermont Yankee Chemistry Department over the last several months using an established procedure to ascertain the root causes and contributing causes of events.
The leak itself was stopped on February 15, 2010. At no time did the tritium leak present a threat to public health and safety and there has been no detectable tritium levels found in any drinking water well samples or in Connecticut River water.
Vermont Yankee has implemented a groundwater remediation plan that involves pumping the water to the surface for filtering and storage for use in the plant. That process has been successful in steadily reducing the concentration of tritium in the site s groundwater. Other radionuclides, including cesium, strontium, cobalt, zinc and manganese, normally produced during plant operation, were identified in soil at low levels in very close proximity to the leak site. The removal of that soil is essentially complete. Vermont Yankee expects that there will be no additional cost to eventual decommissioning of the plant due to the leakage.
Entergy has stated its intention to be an industry leader in tritium leak prevention and mitigation, announcing on March 25 a six-point groundwater protection initiative. The company has begun implementation of more than 50 corrective actions toward that goal, many of which have already been completed. Entergy Vermont Yankee has provided the final root cause analysis findings to state and federal regulators, other operators of U.S. nuclear plants and to the public.
Source: Entergy Vermont Yankee. 6.22.2010. Entergy Corporation is an integrated energy company engaged primarily in electric power production and retail distribution operations. Entergy owns and operates power plants with approximately 30,000 megawatts of electric generating capacity, and it is the second-largest nuclear generator in the United States. Entergy delivers electricity to 2.7 million utility customers in Arkansas, Louisiana, Mississippi and Texas. Entergy has annual revenues of more than $10 billion and over 15,000 employees.