Passive Integral Isolation Valve for Nuclear Reactor
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Solution Overview
Problem
Existing motor-driven integral isolation valve (IIV) designs for the let-down line in nuclear reactors face challenges such as the need for quick response and robustness in high temperature and radiation environments, and they occupy space that disrupts reactor thermal insulation.
Innovation Solution
A valve assembly with a flange connected to the reactor pressure vessel, featuring a movable valve member that closes under reactor pressure and opens with pressurization of a plenum, eliminating the need for a motor actuator and utilizing the reactor coolant inventory and purification system's make-up line for pressurization, ensuring failsafe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a motor-driven integral isolation valve is used for the let-down line, then the valve can control coolant flow in both directions, but the motor actuator occupies space that disrupts reactor thermal insulation and is prone to failure in high radiation and temperature conditions
Solution Approach 1:
The motor actuator is completely removed from the valve assembly. The valve is designed to operate passively using reactor pressure to close the valve and plenum pressurization to open it, eliminating the unreliable motor-driven component while maintaining bidirectional flow control capability
Solution Approach 2:
The valve uses the reactor's own pressure system to operate. Reactor pressure automatically closes the valve during normal operation, and the make-up line pressurizes the plenum to open the valve when needed, making the valve self-operating without external motor actuators
2Ease of operation
If a motor-driven integral isolation valve is used, then the valve can be actuated remotely, but the actuator takes up space that disrupts reactor thermal insulation
Solution Approach 1:
The motor actuator is completely removed from the valve assembly. The valve is designed to operate passively using reactor pressure to close the valve and plenum pressurization to open it, eliminating the unreliable motor-driven component while maintaining bidirectional flow control capability
Solution Approach 2:
The valve uses fluid pressure (reactor coolant pressure and make-up line pressure) to operate the valve member. The plenum is pressurized through hydraulic connection from the make-up line to open the valve, replacing mechanical motor actuation with a pneumatic/hydraulic mechanism that requires no space-disrupting actuators
3Device complexity
If a check valve design is used for the let-down line, then the valve structure is simple, but it prevents normal let-down operation since let-down coolant flows out of the reactor
Solution Approach 1:
Instead of using a check valve that allows flow in one direction only, the invention inverts the approach by using reactor pressure to automatically close the valve and plenum pressurization to open it. This reversed logic allows the valve to control outward-flowing let-down coolant while maintaining structural simplicity
Solution Approach 2:
The valve uses the reactor's own pressure system to operate. Reactor pressure automatically closes the valve during normal operation, and the make-up line pressurizes the plenum to open the valve when needed, making the valve self-operating without external motor actuators
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 solution provides reliable and space-efficient isolation during a loss of coolant accident, reducing the risk of coolant loss and maintaining reactor safety without the need for motor-driven actuators, which are prone to failure in high radiation and temperature conditions.
Implementation Method 1
a movable valve member, the valve disposed inside the valve body with the movable valve member positioned so that pressure inside the reactor pressure vessel urges the movable valve member against the valve seat to close the valve
Implementation Method 2
The plenum is configured such that pressurization of the plenum via the inlet urges the movable valve member away from the valve seat to open the valve
Data Source
AI summary
A valve assembly includes a flange connected to a vessel penetration of a reactor pressure vessel of a nuclear reactor. A valve is disposed inside the flange or protrudes from the flange into the vessel penetration. The valve includes a valve seat and a movable valve member positioned so that pressure inside the reactor pressure vessel urges the movable valve member against the valve seat to close the valve. The valve assembly further includes a plenum having an inlet via which the plenum can be pressurized to apply pressure to the movable valve member that urges the movable valve member away from the valve seat to open the valve. The plenum may be defined in part by a surface of the movable valve member. The valve assembly preferably does not include a valve actuator.