Elevated Ventilated Module for Spent Nuclear Fuel Storage
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Solution Overview
Problem
Conventional ventilated dry storage modules for spent nuclear fuel face inefficiencies in cooling due to blockages, variable wind directions, and solar heating, which can lead to inadequate heat dissipation and radiation exposure.
Innovation Solution
A ventilated dry storage system with radially oriented cooling air inlet ducts and a 360-degree radial air outlet configuration, utilizing natural circulation and radiation shielding to enhance cooling efficiency and prevent neutron streaming, while elevating inlet openings to avoid floodwater and thermal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air inlets are positioned close to the support pad for easy air access, then cooling efficiency is improved, but the inlets become susceptible to blockage by snow, debris, or floodwater
Solution Approach 1:
The air inlet openings are elevated vertically above the support pad surface, transitioning from a ground-level position to an elevated position. This dimensional change allows the inlets to access cooling air from above while avoiding blockage from snow, debris, or floodwater on the pad surface, resolving the contradiction between cooling efficiency and blockage resistance
2Reliability
If air inlet openings are elevated above the support pad to avoid blockage, then reliability is improved, but thermal interference from the pad heats the incoming air
Solution Approach 1:
The support pad is designed with a thermal barrier layer (insulation material) between the pad surface and the air inlet openings. This local modification creates a thermally isolated zone around the inlets, allowing them to be elevated for blockage resistance while preventing heat transfer from the pad to the incoming cooling air
3Device complexity
If conventional ventilation is used without radiation shielding, then device complexity is reduced, but neutron streaming occurs from the canister to the atmosphere
Solution Approach 1:
Radiation shielding material is introduced as an intermediary substance within the ventilation system, positioned between the spent fuel canister and the external environment. This mediator blocks neutron streaming through the ventilation pathways while maintaining the passive natural circulation design, resolving the contradiction between system simplicity and radiation protection
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 achieves effective passive cooling of spent nuclear fuel by maximizing ambient air circulation and radiation shielding, ensuring efficient heat dissipation and radiation protection, even in challenging environmental conditions.
Implementation Method 1
The inlet ducts each draw cooling air radially inwards into the cavity via natural circulation
Implementation Method 2
The cooling air flows alongside the canister and upwards in the cavity due to the natural chimney effect as it is heated by the heat emitted by the SNF inside the canister
Implementation Method 3
In some embodiments, radiation attenuation shielding comprising steel or other radiation attenuation inserts or shields may be incorporated into the ducts to enhance radiation blocking
Data Source
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AI summary
A passively cooled storage module for spent nuclear fuel includes an elongated body including a top end, bottom end, sidewall, baseplate, detachable lid, and cavity for holding a fuel canister containing heat-emitting spent nuclear fuel assemblies. Cooling air inlet ducts spaced draw ambient cooling air radially inwards into a lower portion of the cavity. The air flows upwards in the cavity along the canister and is discharged from the top end of the module to atmosphere via natural circulation. The air inlet ducts may have a multi-angled and recurving configuration comprising one or more obliquely angled sections in one embodiment. The exterior inlet end openings of the inlet ducts are arranged at a higher elevation than the interior outlet end openings to prevent the ingress of standing and flood-related waters. The ducts and lid include radiation shielding features.