Dewatered CBPC Waste Form Radiolysis Mitigation
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Solution Overview
Problem
Hydrated chemically bonded phosphate ceramic (CBPC) waste forms are inadequate for stabilizing high-level radioactive wastes due to their susceptibility to radiolysis, which can lead to hydrogen gas generation, pressurization of storage containers, and increased risk of criticality, as well as high volume and weight issues.
Innovation Solution
A method involving the preparation of a slurry with waste, water, an oxide binder, and a phosphate binder, followed by curing and subsequent removal of bound water through heat application to produce a dewatered CBPC waste form, reducing radiolysis resistance and weight, and potentially volume, by driving off water without volatilizing other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hydrated CBPC waste forms are used to stabilize radioactive wastes, then the waste can be immobilized in a ceramic matrix, but the bound water is susceptible to radiolysis leading to hydrogen gas generation and pressurization
Solution Approach 1:
The patent applies the extraction principle by removing bound water from the hydrated CBPC matrix through thermal treatment. The process extracts the harmful water component that would otherwise undergo radiolysis, while preserving the stable ceramic matrix structure. This is achieved by heating the cured CBPC to drive off bound water, resulting in a dewatered waste form that maintains immobilization capability without the radiolysis vulnerability.
2Reliability
If bound water is removed from CBPC waste forms through heat treatment, then resistance to radiolysis is enhanced, but other non-water components may be volatilized at high temperatures
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thermal treatment parameters to achieve selective water removal. The heating temperature and duration are optimized to be sufficient to drive off bound water from the CBPC matrix but remain below the volatilization temperatures of metal and radioactive components. This parameter optimization enables differentiation between water removal and component preservation.
3Ease of manufacture
If conventional high-temperature waste treatment methods are used, then waste can be treated, but volatile contaminants may be released and secondary waste streams are generated
Solution Approach 1:
The patent applies parameter changes by transitioning from high-temperature treatment to low-temperature thermal treatment. The curing temperature is reduced sufficiently to prevent volatilization of contaminants while maintaining the chemical bonding and immobilization functionality of the CBPC matrix. This temperature parameter change enables waste treatment without the harmful effects of conventional high-temperature methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dewatered CBPC waste forms exhibit enhanced resistance to radiolysis, reduced weight, and in some cases, volume, effectively addressing the challenges of stabilizing high-level radioactive wastes while maintaining the encapsulation efficiency of hazardous and radioactive materials.
Implementation Method 1
the bound water is removed by applying heat to the cured CBPC matrix
Data Source
AI summary
A method of stabilizing a waste in a chemically bonded phosphate ceramic (CBPC). The method consists of preparing a slurry including the waste, water, an oxide binder, and a phosphate binder. The slurry is then allowed to cure to a solid, hydrated CBPC matrix. Next, bound water within the solid, hydrated CBPC matrix is removed. Typically, the bound water is removed by applying heat to the cured CBPC matrix. Preferably, the quantity of heat applied to the cured CBPC matrix is sufficient to drive off water bound within the hydrated CBPC matrix, but not to volatalize other non-water components of the matrix, such as metals and radioactive components. Typically, a temperature range of between 100° C.-200° C. will be sufficient. In another embodiment of the invention wherein the waste and water have been mixed prior to the preparation of the slurry, a select amount of water may be evaporated from the waste and water mixture prior to preparation of the slurry. Another aspect of the invention is a direct anyhydrous CBPC fabrication method wherein water is removed from the slurry by heating and mixing the slurry while allowing the slurry to cure. Additional aspects of the invention are ceramic matrix waste forms prepared by the methods disclosed above.