Answer to Question #2816 Submitted to "Ask the Experts"

This answer will consist of the three independent responses.

1. Response from Phil Egidi:

I am working on this very issue in Colorado right now with our Water Quality Control Division and Solid Waste Unit. We have many districts in Colorado that are out of compliance with the MCLs (maximum contaminant levels).

The spent resins may be quite contaminated, particularly with ²²⁶Ra. Uranium is a little easier to deal with since it is less toxic, yielding higher disposal numbers. In Colorado, if the resins are contaminated primarily with ²²⁶Ra, they have to go through the Rocky Mountain Low-Level Waste Compact and end up in Washington (our compact specifically defines radium as low-level waste—long story). Therefore, I would not use Colorado as an example in the response.

Since these residuals are not licensed material, each state would deal with them in its own way. Our state uses a case-by-case approach at the moment. I am putting together a guidance document now that addresses workplace monitoring and monitoring and disposal of residuals.

What I do is try to divide the problem into the main "chunks"—sludges (ferric chloride, sand filtration, etc.) that have relatively low-activity, resins or other contaminated media, and the liquids.

What we do with the low-activity sludges is either have our Solid Waste Group permit monofills that have requirements in the certificate of designation that only the residuals can go in there, and have cap and liner requirements (can give more details if necessary); or other applications have been approved for low-activity sludges—berms in golf courses, etc.—based on risk assessment. Some land farming has been approved, but with very, very low levels. We have also allowed certain industrial landfills to take limited amounts of sludges also based on risk assessment. Our uranium mill may also take them, but has not agreed to at this point in time.

The media and resins we treat as waste and cut a provisional license to the water company to deal with the waste broker—gets expensive on the water districts, but we have no other option at the moment. Again, uranium is a little easier to deal with than radium.

The liquids are the toughest for us out here. If sewer disposal is possible, that is perhaps the best bet, providing the POTW (publicly owned treatment works) is amenable to the gift of the TENORM (technologically enhanced naturally occurring radioactive material) in the inflows. Deep well injection is also a possibility, but very expensive. Evaporation is another method, providing the surface area is available to the facility (the residual sludges are disposed as discussed above). We have some rural districts that do not have sewers, evaporation space, or deep well, and we are scratching our heads now on how to get them in compliance. There are also point-of-use units that could add up to a logistical challenge real quick. How do you license the resins from in-home units (owned by the District)? This is not an easy one to work out. The treatment de jour may be zeolites. They seem to be quite effective in removing metals from the waters. I am not sure if this is the answer you are looking for, but there is no one answer. Contact your friendly state regulator.

2. Response from Tom Gesell, PhD:

If the question is asking about safety concerns to plant personnel while the exhausted resins are stored at the plant pending disposal, there should not be any external radiation concern from the uranium. However the water may contain radium which will likely also be removed by the resin, leading to a measurable external radiation field. Safety concerns would of course depend upon the likelihood and proximity of exposure, ALARA (as low as reasonably achievable) considerations, etc. If you are concerned about the safety of disposal, then you need to be aware of the regulations applying to disposal of NORM and TENORM, which of course vary from state to state. There is a company in Utah that will accept uranium-contaminated materials for recycling, after which the residue is disposed of as uranium mill tailings.

3. Response from Paul Frame, CHP, PhD:

I will start with the assumption that you have identified the means by which you would dispose of this radioactive resin. If not, the State of Nevada's radiation control program might provide some assistance. It should be consulted in any case.

As I see it, the key concern would be the workers' exposures to the gamma rays emitted by the radioactive material that accumulates on the resin. Even though you have specified the expected concentration of the uranium on the resin, the gamma-exposure rates are still hard to predict because they would depend on (among other things) the total amount of resin being used and the concentrations of any other radionuclides that might end up on the resin, ²²⁶Ra and its decay products, for example. The uranium concentrations might be higher than the radium concentrations but the radium might still be the main contributor to the exposures.

If it hasn't been done, it would be a good idea to perform a complete analysis of all the radioactive material on some resin after it has been used in a small-scale test. Once the radionuclides and their concentrations are known, computer codes can be used to predict the exposure rates around a resin bed of a specified geometry.

If necessary, the structural components of the facility (for example, concrete walls) could then be redesigned so as to shield the gamma rays more effectively. The exposures could also be minimized by controlling the time the workers spend near the resin.

Once the facility goes into operation, the radiation levels might have to be monitored via environmental dosimeters and/or routine surveys. Workers might, or might not, require dosimeters.