Isolation Valve Vessel Assembly for Type 1 LOCA Containment
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Solution Overview
Problem
Light water nuclear reactors face challenges in preventing Type 1 Loss of Coolant Accidents (LOCAs) due to leaks between the reactor vessel and valve rooms, which can lead to uncontrolled coolant discharge and complicate long-term cooling processes.
Innovation Solution
The implementation of an isolation valve assembly with a sealed volume and redundant check valves within the pressure vessel to prevent fluid flow out of the vessel, including a spool piece and an isolation valve vessel connected via flanges, and an external valve for redundancy, which can be actuated electrically, hydraulically, or manually to control coolant flow and prevent backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation valves are placed in valve rooms connected to the reactor vessel, then coolant flow can be controlled, but leaks between the vessel and valve rooms can cause Type 1 LOCAs with uncontrolled coolant discharge
Solution Approach 1:
The patent extracts the isolation valve from the external valve room environment and places it inside the reactor vessel. This eliminates the vulnerable connection between the vessel and valve room that enables Type 1 LOCAs, while maintaining the essential function of coolant flow control. The valve operates within the sealed vessel environment, preventing uncontrolled discharge.
Solution Approach 2:
The patent introduces a sealed transition piece as an intermediary component that connects the reactor vessel to the external piping system. This sealed intermediary allows coolant flow control while preventing the type of leaks that cause Type 1 LOCAs, effectively mediating between the internal vessel environment and external valve room connections.
2Ease of operation
If multiple vessel penetrations are provided for coolant lines, then coolant management is improved, but the likelihood of severe LOCA events increases
Solution Approach 1:
The patent merges multiple coolant line functions into a single integrated penetration point within the reactor vessel. Instead of having separate penetrations for different coolant lines that could each fail independently, the design consolidates these functions, reducing the number of potential failure points while maintaining comprehensive coolant management capability.
3Power
If external piping is used to connect steam generators, then heat exchange efficiency is maintained, but pipe breaks can cause uncontrolled coolant loss
Solution Approach 1:
The patent extracts the isolation valve function from external piping and relocates it to the reactor vessel interior. This eliminates the vulnerable external pipe sections that are prone to breaks causing uncontrolled coolant loss, while maintaining the heat exchange efficiency of the steam generator connections through properly designed internal flow paths.
Data Source
AI summary
Apparatuses for reducing or eliminating Type 1 LOCAs in a nuclear reactor vessel. A nuclear reactor including a nuclear reactor core comprising a fissile material, a pressure vessel containing the nuclear reactor core immersed in primary coolant disposed in the pressure vessel, and an isolation valve assembly including, an isolation valve vessel having a single open end with a flange, a spool piece having a first flange secured to a wall of the pressure vessel and a second flange secured to the flange of the isolation valve vessel, a fluid flow line passing through the spool piece to conduct fluid flow into or out of the first flange wherein a portion of the fluid flow line is disposed in the isolation valve vessel, and at least one valve disposed in the isolation valve vessel and operatively connected with the fluid flow line.