Neutron Path Device for Reactor Startup Detection
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Solution Overview
Problem
Fission type nuclear reactors face challenges in detecting neutron flux during startup and shutdown due to weak neutron signals from inert neutron sources, which can lead to 'blind' starts and inaccurate reactivity measurements, affecting safety and operational efficiency.
Innovation Solution
A neutron detection system that includes a neutron source configured to provide a stable neutron flux, combined with a neutron path device that minimizes attenuation by using a partial vacuum as the medium between the neutron source and detector, ensuring a reliable and consistent neutron flux is detected across various reactor operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a neutron source is used to provide neutron flux during reactor startup and shutdown, then the ability to initiate and monitor reactor operation is improved, but the neutron signal becomes too weak for detection instrumentation to reliably detect, leading to blind starts
Solution Approach 1:
A neutron reflector is positioned between the neutron source and the detector to redirect scattered neutrons toward the detector, increasing the detected neutron signal strength. This intermediary component solves the problem of weak neutron signals from inert sources during shutdown conditions, enabling reliable detection without compromising the source's ability to provide startup neutron flux.
2Reliability
If neutron detectors are configured to detect high levels of neutrons during reactor operation, then operational monitoring is improved, but the detectors cannot sufficiently detect low levels of neutrons during shutdown or startup
Solution Approach 1:
The neutron reflector acts as a signal amplifier for low-level neutron detection during shutdown and startup conditions. By reflecting scattered neutrons back toward the detector, it enhances the already-weak signals from inert neutron sources, allowing the same detector to operate effectively across both high-flux operational modes and low-flux startup/shutdown modes without requiring separate detection systems.
3Measurement precision
If the neutron source is placed close to the detector to improve detection sensitivity, then low-level neutron detection is improved, but the geometric arrangement may not be feasible during reactor operation
Solution Approach 1:
The neutron reflector enables the detector to be positioned at a greater distance from the neutron source while maintaining detection sensitivity. The reflector compensates for the increased path length and geometric spreading of neutrons, allowing a more practical spatial arrangement that works during both operational and shutdown conditions without requiring the detector to be in close proximity to the source.
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
This solution enables accurate detection of neutron activity during all reactor modes, preventing 'blind' starts and ensuring safe operation by maintaining a consistent neutron flux, even in attenuating environments, thus enhancing reactor monitoring and control.
Implementation Method 1
a neutron path device that provides a neutron attenuation path between the containment vessel and the reactor vessel... configured to provide a consistent level of neutron attenuation
Implementation Method 2
Spontaneous fission events produced by the fuel may be too weak for certain types of reactor monitoring instrumentation to detect
Data Source
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AI summary
A neutron detection system may include a neutron detection device located outside of a reactor vessel. The neutron detection device may be configured to detect neutrons generated within the reactor vessel. A containment region located intermediate the reactor vessel and a containment vessel may be configured to house a containment medium. A neutron path device may be at least partially located between the reactor vessel and the containment vessel, and the neutron path device may be configured to provide a neutron path to the neutron detection device through a neutron path medium contained within the neutron path device. A neutron attenuation coefficient associated with the neutron path medium may be smaller than a neutron attenuation coefficient associated with the containment medium.