Ventilated Overpack for Radioactive Waste Cooling and Shielding
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Solution Overview
Problem
Existing ventilated systems for storing high level radioactive waste, such as spent nuclear fuel, pose a risk of radiation exposure to personnel due to the location of inlet ducts, which are vulnerable and do not provide adequate radiation shielding against gamma and neutron radiation.
Innovation Solution
A vertical ventilated overpack system with an annular air inlet vent and an axisymmetric air outlet vent, designed to introduce cool air at the bottom and remove warmed air from the top, featuring a cyclical thermosiphon flow for natural convective cooling, while providing extreme radiation blockage through neutron and gamma shielding materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If inlet ducts are positioned near the bottom of the overpack for ventilation, then heat removal from the canister is improved, but radiation exposure risk to personnel increases
Solution Approach 1:
The inlet vent is repositioned from a horizontal location near the bottom to a vertical location at the top of the overpack. This dimensional change in duct positioning allows heat removal to continue while eliminating the radiation exposure hazard associated with bottom-level horizontal ducts that require personnel proximity for monitoring.
Solution Approach 2:
A radiation shielding material is introduced as an intermediary substance within the inlet vent structure. This shielding material absorbs or blocks radiation while allowing air flow to pass through, thereby protecting personnel from radiation exposure while maintaining the ventilation function for heat removal.
2Temperature
If ventilation ducts are located near the bottom and top of the overpack, then natural convective cooling is improved, but radiation shielding effectiveness is reduced
Solution Approach 1:
The inlet vent structure is designed with localized radiation shielding material positioned specifically at the radiation-vulnerable inlet location. This localized shielding provides targeted protection against radiation while maintaining the overall convective cooling pathway, rather than requiring complete shielding of the entire ventilation system.
Solution Approach 2:
The inlet vent is constructed as a composite structure combining radiation shielding materials with ventilation-compatible materials. This composite design allows the vent to simultaneously perform both functions: removing heat through air flow while blocking radiation from reaching the external environment and personnel.
3Object-affected harmful factors
If the overpack structure is made massive with thick shielding, then radiation blockage is improved, but weight and structural complexity increase
Solution Approach 1:
Radiation shielding is applied locally only where radiation exposure occurs (at the inlet vent location) rather than requiring the entire overpack structure to be massively thick. This localized approach provides adequate radiation blockage while significantly reducing the overall weight and structural complexity compared to a fully massive design.
Solution Approach 2:
The overpack utilizes composite material construction with radiation shielding materials strategically positioned in the inlet vent and other critical areas. This composite approach provides effective radiation protection through material properties rather than relying solely on massive structural thickness, thereby reducing overall weight.
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 system effectively reduces radiation exposure risks and enhances radiation shielding, ensuring safe storage and cooling of high level radioactive waste by maintaining aerodynamic performance independent of air-stream direction and utilizing shielding materials to absorb radiation.
Implementation Method 1
featuring a cyclical thermosiphon flow for natural convective cooling
Implementation Method 2
utilize natural convective cooling
Implementation Method 3
providing extreme radiation blockage through neutron and gamma shielding materials
Data Source
AI summary
A system for storing high level radioactive waste. In one embodiment, the invention can be a system comprising an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor; an overpack lid positioned atop the overpack body to enclose the open top end of the cavity; an air inlet vent for introducing cool air into the cavity, the air inlet vent extending from an opening in an outer surface of the overpack body to an opening in the floor; and an air outlet vent in the overpack lid for removing warmed air from the cavity.