Answer to Question #10400 Submitted to "Ask the Experts"

Category: Radioactive Waste Disposal — Mixed Waste

The following question was answered by an expert in the appropriate field:


Do heavy metal contents like 73As, 125Cd, etc., make the radioactive waste "mixed" and, if so, is there a list of metals and their parts per million that will make them exempt from being classified as mixed? Or must each individual liquid container need to be evaluated?


40 CFR 262.11 provides an identification method to determine whether or not materials intended for disposal should be classified as hazardous waste. The identification method can be conducted by answering the following questions:

  1. Is the material excluded from regulation based on 40 CFR 261.4?
  2. Is the material listed in 40 CFR 261 Subpart D?
  3. If not listed in Subpart D, does the material meet the hazard characteristics of hazardous waste described in Subpart C? This can be achieved by performing specific testing (e.g., toxicity characteristics leaching procedure [TCLP]) or by applying generator's knowledge (e.g., "best guess" knowledge of the constituents used in the "waste" generating process).

Materials that meet the definition of class 7 (radioactive) materials are not considered solid waste as per 40 CFR 261.4(4). However, it is necessary to examine the chemical conditions of the substance for disposal. 10 CFR 261 Subpart D provides "waste" codes for the substances that are considered hazardous. The lists are process-specific and substance-specific. Therefore, specific knowledge of the "contents" and process(es) that generate the residual materials should be considered in order to determine if the residual materials classify as mixed waste or not. From the information provided in your question, it is not possible to determine if the substances should be considered hazardous. Furthermore, it is possible to determine if a substance is hazardous or not based on alternative methods. TCLP tests may be performed to determine if the substances meet or exceed the specific hazardous characteristics and limits described in 40 CFR Subpart C and thus are deemed as hazardous. Generator's knowledge may also be used to determine if the substance's constituents meet the hazardous characteristics. For example, chemical balances of chemical process may be used to determine the waste constituents and quantities and subsequent verification against Subpart D and C, respectively.

Based on the aforementioned process and the information provided in your question, we can conclude that if the substance containing radioactive materials is listed in Subpart D or does meet the hazardous characteristics or limits listed in Subpart C, then the substance should be considered as "mixed waste." For the purpose of disposal, the disposal facility may impose acceptance limits. These may be based on regulatory limits or explicit limitations on the disposal methods.

I always suggest that you consult with the disposal facility or processor in order to determine the specifics that are applicable to your material for disposal. These interactions are not only of benefit for the generator to characterize the "waste" material, but also ease the disposal process.

Manuel Diaz

Answer posted on 12 September 2012. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.