Defining criteria for cemented waste produced from legacy liquids

Atomic Energy of Canada Limited (AECL) has several hundred cubic metres of legacy radioactive waste stored in underground tanks at the Chalk River Laboratories (CRL) site in Chalk River, Ontario. As part of a larger campaign to reduce its legacy liabilities, AECL intends to remove and immobilize this waste using a cementation system. The cemented waste form is intended to be suitable for both interim storage in existing CRL facilities, and long-term management in a future disposal facility, without further treatment. In addition, the entire process must be acceptable to the Canadian nuclear regulator. AECL plans to hire an external contractor to design and operate a cementation skid to remove and condition the liquid wastes. Clear and measurable waste form criteria must be determined and provided to the contractor in order for the contractor to demonstrate that a safe and stable waste form has been produced. However, defining these criteria has been a challenge due to several factors, including: 1) The future long-term disposal facility does not exist, and therefore the current Waste Acceptance Criteria (WAC) for such a facility are only strategic and do not provide sufficient detail. 2) The Canadian regulatory documentation for such wastes provides general guidance rather than specific, easily measurable criteria, therefore appropriate criteria must be deduced. In addition, from a practical point of view, the waste form criteria must be achievable and demonstrable. In AECL's case, the liquid wastes are unique in that virtually all tanks each require a specially-tailored cementation formulation, thus the effort required to evaluate and demonstrate acceptability for all waste forms is significant. The paper discusses the approach taken by AECL to select appropriate criteria. This approach includes an evaluation of criteria, standards and practices used in other countries; development of Waste Acceptance Criteria for the envisioned future long-term disposal facility; and an extensive test program to provide confidence that the criteria identified are practical and achievable. (author)