(423a) Implementation of a New Defoamer in the Defense Waste Processing Facility to Reduce Batch Processing Time and Improve Safety

The legacy of the waste from the production of nuclear weapons materials is the biggest environmental challenge in the state of South Carolina, and one of the biggest in the United States. Although great progress has been made in processing and vitrifying high level waste at the Savannah River Site, approximately 35 million gallons remains to be processed. In this paper, we discuss the new defoamer that has been developed for use in processing high level radioactive waste. The use of the new defoamer will allow higher evaporation rates, leading to as much as a 50% decrease in processing time per batch.

The defoamer is novel because it is effective in the harsh conditions needed for processing high-level radioactive waste, including high temperatures, a wide pH range (4 to 13), strong oxidizing and reducing agents, and the presence of a myriad of metal catalysts. The defoamer has replaced an old antifoam agent that was chemically unstable at non-neutral pH and decomposed to form three flammable gases. Because the old antifoam agent decomposed quickly, processing changes were needed which resulted in increasing processing time, including lowering acid addition rates and evaporation rates.

The new defoamer is not only more effective at controlling foam but, as a result, will shorten the batch processing time and lead to safer and more efficient processing by eliminating the production of flammable gases. Testing demonstrated that the new defoamer would meet all the requirements needed for foam mitigation during DWPF processing. The new defoamer will shorten the mission lifetime, allowing the vitrification facility to be shut down several years early, potentially saving the federal government hundreds of millions of dollars in operating costs.

This paper will discuss the implementation of the new defoamer in the Defense Waste Processing Facility (DWPF). Use of the new defoamer has demonstrated that excessive foaming and foamovers have been eliminated allowing DWPF to increase acid addition rate and steam flow rate to maximum rates permitted by procedures and safety requirements.