E. Washington officials try again to fire up world’s largest radioactive waste melter
A second attempt began on Saturday to heat up the world’s largest radioactive waste melter to turn waste into a stable glass form at the Hanford nuclear reservation site.
It’s a significant step toward getting the massive Hanford vitrification plant operating after construction started 21 years ago and a crucial step toward getting millions of gallons of radioactive waste treated and into permanent disposal.
Early Monday morning the melter temperature had reached 313 degrees, and the heat up was paused for 48 hours for a preplanned evaluation.
The goal is to get the temperature to 2,100 degrees Fahrenheit, the temperature needed to eventually glassify radioactive waste.
“DOE is following a carefully planned approach in the heat up process that will take several weeks to ensure the temperature increase slowly and steadily toward the target temperature,” DOE said in a statement.
Bechtel National, the contractor building and commissioning the plant for the Department of Energy, attempted to heat up the vit plant’s first 300-ton melter Oct. 8.
But the heating was halted just after midnight the morning of Oct. 10 as temperatures were close to 300 degrees after a problem was discovered with the power supply to the melter’s startup heaters.
Temperatures were rising in the power supply cabinets, and pictures taken after the heat up was halted showed blackened inductors in the worst of the three cabinets.
Then DOE had expected to run the melter continuously for five years, requiring operating the plant around the clock.
Dropping the melter’s temperature can damage the melter’s insulation, or refractory, which can harden and become ineffective if the temperature cools while the melter holds molten glass.
But with temperatures not yet significantly high and the melter still empty during the aborted October heat up, Bechtel was able to slowly lower the heat without damaging the melter.
Since October, DOE and Bechtel have been troubleshooting the problem, seeing how widely it extended and making changes, including ordering and installing some new parts or equipment, before a restart of the heat up.
How melter heat up done
The Hanford nuclear reservation site in Eastern Washington adjacent to Richland has 56 million gallons of radioactive and hazardous waste stored in underground tanks until it can be treated for disposal. The oldest of the tanks are prone to leaking waste into the ground, where it will move toward the Columbia River once it reaches groundwater.
The waste is left from the past production nearly two-thirds of plutonium for the nation’s nuclear weapons program from World War II through the Cold War.
Initially, the vitrification plant will glassify the least radioactive waste in the tanks, with plans still being made to vitrify the high level radioactive tank waste.
DOE had planned to start treating low activity radioactive waste at the vitrification plant, or Waste Treatment Plant, by the end of this year. But the COVID-19 pandemic and now the delay in startup of the melter have led to the need for a new schedule, which Hanford officials will work on now that the melter heating has started again.
The melter heat up is done with two sets of heaters.
Heating was started Saturday on the vitrification plant’s first melter using temporary startup heaters, with the heating planned to gradually transition to operational, or Joule, heaters as glass beads is added to the melter and molten glass rises to meet the Joule heater electrodes.
During the heat up only glass beads will be added to the melters, but during actual operations bubblers will be inserted into the melter to keep the waste mixed and prevent any hot spots from forming.
The initial heating is done gradually to slowly dry out the insulation within the melter.
Dropping the melter’s temperature after the melter contains molten glass can damage the melter’s insulation, or refractory, which can harden and become ineffective if the temperature cools.
Once the melter temperature reaches 2,100 degrees, the next month or two will be used for evaluation and checks of the initial process.
Work also is expected to start later this year on a second melter at the vitrification plant’s Low Activity Waste Facility.
Then the melters will be tested using first a nonradioactive waste simulant and then radioactive waste before the facility is turned over for waste treatment operations.
Full review of melter equipment
The problem with the initial heat up that started in October was detected by operators who noted the increased heat in the power supply system about 36 hours into operation.
Bechtel called worker performance in identifying and responding to the issue with the power supply “a demonstration in operational excellence.”
Technical experts and computer modeling determined that the inductors were not designed for the low power of the startup.
But Hanford officials also wanted to take time to check whether there could be similar problems elsewhere in melter components, including in the Joule heaters.
Although a similar problem was not found, there were other issues detected that resulted in a fine detail check of components.
The full review of all melter heater equipment resulted in some redesign and the purchase of some new equipment. Then testing was done to verify all systems were ready for the second attempt at the melter heat up that began Saturday.