Nested Core Catcher Layout for Corium Confinement Reliability
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Solution Overview
Problem
Existing nuclear power plants lack sufficient safety measures to contain and manage molten corium in the event of a severe accident, which can lead to core damage and the release of harmful radiation.
Innovation Solution
A nuclear power plant design featuring multiple containment levels, including a reactor pressure vessel, a primary core catcher, and a secondary core catcher, each with specific materials and cooling mechanisms to confine and cool molten corium, reducing the likelihood of total confinement failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single core catcher is used to contain molten corium, then the device complexity is reduced, but the reliability of confinement is insufficient
Solution Approach 1:
The containment system is divided into three independent segments: the reactor pressure vessel, the primary core catcher, and the secondary core catcher. Each segment can independently contain molten corium, so that failure of one segment does not lead to total confinement failure. This segmentation increases reliability while maintaining manageable complexity through modular design.
Solution Approach 2:
The containment structure follows a nested configuration where the primary core catcher is positioned inside the secondary core catcher, which in turn is inside the reactor pressure vessel. This nested arrangement allows multiple containment levels to coexist in a compact configuration, achieving enhanced reliability without excessive increase in overall system complexity.
2Temperature
If water cooling is applied to the reactor pressure vessel exterior, then the temperature control is improved, but the risk of structural integrity failure increases
Solution Approach 1:
An air gap is introduced as an intermediary thermal insulation layer between the reactor pressure vessel exterior and the water cooling system. This air gap reduces direct thermal coupling, allowing effective temperature control through water cooling while minimizing thermal stress and protecting the structural integrity of the reactor pressure vessel.
3Temperature
If the primary core catcher is submerged in water, then the cooling efficiency is improved, but the structural stability may be compromised
Solution Approach 1:
The primary core catcher is positioned on a support structure that acts as an intermediary between the core catcher and the water. This support structure provides mechanical stability and prevents direct contact between water and the core catcher, enabling effective water cooling while maintaining structural stability.
4Reliability
If multiple containment levels are implemented, then the safety against corium escape is improved, but the system dependency increases
Solution Approach 1:
The containment system is segmented into three independent functional units (reactor pressure vessel, primary core catcher, secondary core catcher), each capable of independently containing corium. This independence reduces system dependency, as the failure of one segment does not necessarily compromise the others, thereby improving overall safety while managing complexity.
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 triple-layer containment system effectively reduces the risk of corium escape by enhancing the likelihood of solidification through temperature and volume changes, minimizing decay heat, and reducing system dependency, thereby improving safety and reliability.
Implementation Method 1
means for water-cooling the exterior of reactor pressure vessel in the event of an emergency requiring cooling of the nuclear reactor
Implementation Method 2
a primary core catcher outwardly of the reactor pressure vessel, the primary core catcher being formed of a material suitable for retaining molten corium
Implementation Method 3
a secondary core catcher lining a tank which is water-filled in normal use of the plant to submerge and thereby water-cool the primary core catcher
Implementation Method 4
The delay in having to progress through the levels also reduces the decay heat levels in addition, the increased volume reduces the decay heat volumetric density, again increasing the likelihood of solidification
Implementation Method 5
the secondary core catcher being formed of a material suitable for retaining molten corium in the event corium escapes the primary core catcher
Data Source
AI summary
A nuclear power plant has a nuclear reactor including a reactor pressure vessel which houses plural fuel rods containing fissile material. The nuclear power plant further has means for submerging the reactor pressure vessel in water and thereby water-cooling the reactor pressure vessel in the event of an emergency requiring cooling of the nuclear reactor. The nuclear power plant further has a primary core catcher outwardly of the reactor pressure vessel, the primary core catcher being formed of a material suitable for retaining molten corium in the event corium escapes the reactor pressure vessel. The nuclear power plant further has secondary core catcher outwardly of the primary core catcher, the secondary core catcher lining a tank which is water-filled in normal use of the plant to submerge and thereby water-cool the primary core catcher. The secondary core catcher is also is formed of a material suitable for retaining molten corium in the event corium escapes the primary core catcher.