DOE Office of River Protection: Preparing for safe tank waste treatment

Forty years of plutonium production — from World War II through the Cold War — at the Hanford Site have yielded a challenging nuclear waste legacy — approximately 56 million gallons of radioactive chemical waste accumulated in 177 aging underground storage tanks.

The Department of Energy’s Office of River Protection (ORP) is responsible for safely storing, retrieving and treating Hanford’s tank waste and closing the tank farms.

We are adamant that work be done as safely as possible. To show that commitment, ORP and its contractors, Bechtel National Inc., and Washington River Protection Solutions (WRPS), were recognized with the Department of Energy’s Voluntary Protection Programs “Star of Excellence” Program status in 2015, validating the priority we all place on worker safety.

Companies with “Star” status have achieved injury and illness rates at or below the national average within their respective industries and show strong worker participation in safety. This is the highest award for safety in DOE.

We continue our path to begin tank waste treatment as soon as 2022 through use of a Direct-Feed Low-Activity Waste (DFLAW) process to dramatically reduce the volume of low-activity waste stored on the Hanford Site.

Part of the DFLAW process will include building a Low-Activity Waste Pretreatment System (LAWPS) facility, which will separate tank waste into low-activity and high-level waste streams and feed the low-activity waste (LAW) component directly to the WTP LAW vitrification facility.

Vitrification is a process in which the radioactive liquid waste is mixed with glass-forming materials, heated to 2,100 degrees, and poured into stainless steel containers where it cools to a solid glass form for long-term storage or disposal.

Construction continues on the Waste Treatment and Immobilization Plant (WTP) Low-Activity Waste Facility, Balance of Facilities and the Analytical Laboratory. Production engineering continues on the High-Level Waste Facility. Last year, workers transitioned from construction to startup of all major systems for three Balance of Facilities (BOF), indicating these systems are ready for operational testing.

The systems are associated with the WTP Switchgear, BOF Switchgear and Non-Radioactive Liquid Waste Disposal facilities.

We are also working to resolve technical issues associated with the WTP Pretreatment Facility (PT) and to a lesser extent, the High-Level Waste Facility. Last year, we approved the use of a full-sized vessel for the WTP Full-Scale Vessel Test of pulse-jet mixers, a key component in the safe mixing of the waste in the PT. The full-sized test vessel will be delivered this year.

Other progress at the WTP includes the placement of the refractory for the two 300-ton melters installed in the Low-Activity Waste Facility. The refractory is the fire- and heat-resistant brick lining for the melters. These melters are the largest of their kind in the world.

In parallel, we are and have been taking steps to ensure that the waste is safely stored until it can be disposed of. This includes addressing reported worker exposures to vapors in the tank farms. The diversity of the physical and chemical properties of the waste make the clean-up mission very complicated. While interim stabilization saw the liquid moved from the older single-shell tanks (SSTs) to the newer and larger-capacity double-shell tanks (DSTs), we’re now in the process of retrieving the rest of the waste — the sludge and saltcake — from the SSTs to ensure it is adequately secured and safely maintained until it can be treated.

With tank C-102, we have completed retrieval of our 15th SST, leaving just two tanks to be retrieved in C Farm. We will continue retrieval work on those — C-105 and C-111 — and apply what we’ve learned from retrievals in the C Farm to preparing A and AX tank farms for retrieval.

Also, we will start retrieving waste from the leaking DST AY-102 this spring.

One way we are reducing waste volume is through use of our 242-A Evaporator. In 2015, we met our goal of four “campaigns” and evaporated about 1,930,000 gallons of excess water from the DSTs — the size of two DSTs — which provides us flexibility and more available space for waste transferred from the SSTs. This year, ORP plans to capitalize on last year’s successes and continue to progress even further through use of the 242-A Evaporator.

Contributing to our goal to be fully transparent about our work, you can view data on each of our tanks in real-time with our PHOENIX Tank Farms application available on the Hanford.gov website.

This story was originally published March 22, 2016 at 10:33 PM with the headline "DOE Office of River Protection: Preparing for safe tank waste treatment."