WASH. REGULATORS WANT ACTION ON DAMAGED DST
WC MONITOR
1/17/2014
The state of Washington is growing impatient after no waste has been emptied from Hanford’s double-shell Tank AY-102 more than a year after the Department of Energy discovered a leak between the tank’s shells. The Washington State Department of Ecology told DOE in a strongly worded letter sent Jan. 9 that its lack of action was “unacceptable,” given state hazardous waste regulations. State regulations require DOE to inspect the tank to determine the cause of the leak, including removing as much of the waste as necessary to allow for the inspection, within 24 hours or as early as practicable, according to the state. DOE does not know the location of the leak, the rate of leakage or conditions at the leak site within the tank, according to the state. It also does not know when or how the leak might worsen or what effect changes in temperature will have on the leak. “We are deeply disappointed,” the state said about a DOE plan it described as calling for no action to remove waste from the tank until conditions worsen.
The 75-foot diameter tank holds more than 800,000 gallons of waste, most of it liquid and some of it sludge. Jane Hedges, manager of the state’s Nuclear Waste Program, wants DOE and Washington River Protection Solutions to work with the state to produce a workable plan by Feb. 15 for pumping waste from Tank AY-102. The DOE Office of River Protection has been actively monitoring and assessing the tank since a “small leak” between its shells was discovered in August, DOE said in a statement. It has worked with private industry to develop and deploy a robotic crawler in small channels within the tank’s leak detection pit system, which is outside the secondary tank. An inspection using the robotic crawler, weekly visual surveys and other evaluation tools have not detected any waste leaking from the outer shell into the soil beneath the tank, the statement said.
DOE Says It Would Need Up to 20 Months to Prepare
Tank AY-102 is part of a system of 28 newer double-shell tanks that are nearing capacity as they are used to hold waste from 149 older single shell tanks until the waste can be treated at the Hanford vitrification plant or elsewhere. At least one of the single-shell tanks is actively leaking waste into the soil and 67 tanks are suspected of leaking waste in the past. This past spring DOE estimated the AY-102 interior leak at 190 to 520 gallons of waste, but said a significant portion of the liquid has evaporated, leaving an estimated 20 to 50 gallons of drying waste between the shells.
DOE has installed a pump that could drain liquid waste from Tank AY-102. However, as long as 151,000 gallons of sludge remain in that tank, some of the 680,000 gallons of liquid also will need to be left in the tank to help cool it. The sludge generates heat as it radioactively decays, and heat can increase corrosion rates in the tank and contribute to generating potentially flammable hydrogen gas. The Defense Nuclear Facilities Safety Board has questioned DOE assumptions about pumping out some of the liquid waste, finding there were uncertainties about what a change in temperature, pressure or chemistry would mean to the rate of leaking and to the physical condition of the tank, which is more than 40 years old. To prepare to also remove sludge from the tank, DOE estimates it needs another 18-to-20 months.
There are risks to waiting to empty the double-shell tank, according to the letter of the state. The leak has the potential to clog ventilation channels, undermining the ability to moderate the heat in the tank and leading to greater corrosion of the tank bottom. The outer shell of the tank is thinner than its inner shell. DOE does not appear to have a plan for what to do if the ventilation channels clog or to predict how long the outer shell will hold, the state said. The state accepts that DOE was unable to immediately begin pumping waste from the tank when the interior leak was discovered and that some safety issues may need to be resolved to pump the tank. “However, this does not relieve you from the regulatory requirement to remove it at the earliest practicable time,” the state letter said. “We cannot support merely waiting for conditions to worsen before taking action.”
WRPS MISSED TANK GAS MONITORING DEADLINE
WC Monitor
1/17/2014
A paperwork mistake caused a deadline to check some Hanford single-shell tanks for the buildup of flammable gas to be missed for more than eight months. Regulations require the tanks in the A, BY and C Tank Farms be sampled every 365 days for flammable gases, said John Britton, spokesman for Hanford tank farms contractor Washington River Protection Solutions. WRPS realized on Dec. 21 that sampling had been missed in late March for the C Farm tanks, in early May for the A Farm tanks and in mid July for the BY Farm tanks. Sampling was done the next day with no serious problem discovered. DOE takes any violation seriously, it said in a statement. It is reviewing the quality of WRPS’s data management and compliance with required procedures.
The problem occurred when an incorrect date was entered on a spreadsheet used to track sampling, Britton said. The three tank farms include two dozen single shell tanks that still hold waste. Hydrogen gas can be produced as materials in the waste break down. However, the highest risk of flammable gas generation is in Hanford’s double-shell tanks, some of which have more recently generated radioactive waste and some of which are high heat tanks. They are actively ventilated with exhausters and monitored more frequently. In September 2012, the Defense Nuclear Facility Safety Board called for faster action to make improvements in ventilation systems for Hanford’s 28 double-shell tanks. It said that a significant flammable gas accident would have considerable radiological consequences, endanger personnel, contaminate portions of the tank farms and seriously disrupt the waste cleanup mission. DOE responded by instituting an improved testing and monitoring system for ventilation of double-shell tanks. Single-shell tanks, with their lower risk of flam-mable gas buildup, use a passive ventilation system.
WRPS has changed is procedures for single-shell tanks since the monitoring lapse was discovered, Britton said. Although there was not an immediate safety issue, not following the schedule for monitoring the single shell tanks for flammable gas buildup was an unacceptable lapse in conduct of operations, he said. “It’s a very serious error and we’re aggressively taking actions to remedy the issue,” he said.
