Neutron Moderator Collar Layout for Vacuum-Space Yield Loss
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Solution Overview
Problem
The vacuum space between the cold and thermal pre-moderator in tubular neutron moderators results in a significant loss of cold and thermal neutron yield due to limited neutron paths and absorption in the moderator walls, leading to a 'dead space' that reduces the overall neutron emission efficiency.
Innovation Solution
A pre-moderator collar is introduced around the cold neutron exit window to cover the vacuum space, bridging the gap between the cold and thermal pre-moderator, increasing the surface area for neutron exit and enhancing the thermal neutron yield by deflecting neutron trajectories towards the exit window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a vacuum space is introduced between the cold moderator and thermal pre-moderator to reduce heat conduction, then thermal insulation is improved, but neutron yield is significantly reduced due to limited neutron paths and absorption in moderator walls
Solution Approach 1:
The pre-moderator is segmented into two functional parts: a pre-moderator mantle surrounding the cold moderator and a pre-moderator collar at the exit window. This segmentation allows the collar to specifically address neutron path limitations in the vacuum space region while the mantle provides overall thermal insulation and neutron moderation.
Solution Approach 2:
The pre-moderator collar extends into the vacuum space region, utilizing the longitudinal dimension to bridge the gap between the cold moderator exit window and the pre-moderator mantle. This dimensional extension creates additional neutron paths through the vacuum space that would otherwise be unavailable.
2Productivity
If the pre-moderator collar covers the vacuum space, then neutron paths are increased and thermal neutron yield is enhanced, but the vacuum space functionality for thermal insulation is reduced
Solution Approach 1:
Different regions of the pre-moderator are assigned different functions: the pre-moderator collar at the exit window region is optimized for neutron path extension and thermal neutron production, while the pre-moderator mantle in the mid-section maintains thermal insulation functionality. This local differentiation resolves the contradiction between neutron yield enhancement and thermal insulation preservation.
3Productivity
If the pre-moderator collar is positioned to cover the vacuum space, then neutron emission efficiency is improved by redirecting neutron trajectories, but the cold moderator exit window area is reduced
Solution Approach 1:
The pre-moderator collar merges the functions of the vacuum space region and the pre-moderator into a single continuous structure. This merging creates a seamless neutron path from the cold moderator through the collar region, redirecting neutron trajectories that would otherwise be lost, while maintaining adequate exit window area for cold neutron emission.
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 significantly increases the total neutron yield of the moderator, maintaining cold neutron yield while enhancing thermal neutron yield, by utilizing the pre-moderator collar to redirect neutrons that would otherwise be lost in the vacuum space, thus improving the overall emission efficiency.
Implementation Method 1
The pre-moderator collar extending from the pre-moderator mantle towards the longitudinal axis at least one end of the pre-moderator, which substantially covers the portion of the vacuum space between the cold moderator and the pre-moderator mantle from the direction of the neutron exit window
Implementation Method 2
a vacuum space arranged along the longitudinal axis, the thermal pre-moderator having a pre-moderator mantle surrounding the cold moderator along the longitudinal axis and separated from the cold moderator by the vacuum space
Implementation Method 3
the medium (e.g. 20 K liquid para-H2) of the central cold moderator 2 is surrounded by a vacuum space 4, followed by the pre-moderator 3 (e.g. room temperature water)
Implementation Method 4
the neutrons thermalized here exit the pre-moderator 3 with a typically cosine directional distribution close to the normal distribution
Data Source
AI summary
The invention relates to a combined cold and thermal neutron moderator (10) having a longitudinal axis (t) and at least one neutron exit window (50) at a first end (11, 12), and a cold moderator (20) arranged along the longitudinal axis (t), a thermal pre-moderator (30) and a vacuum space (40), said thermal pre-moderator (30) having a pre-moderator mantle (32) surrounding the cold moderator (20) along the longitudinal axis (t) and separated from the cold moderator (20) by the vacuum space (40), characterized in that the pre-moderator (30) comprises a pre¬moderator collar (34) extending at least at the first end (11, 12) from the pre¬moderator jacket (32) towards the longitudinal axis (t), which substantially covers the portion of the vacuum space (40) between the cold moderator (20) and the pre¬moderator mantle (32) from the direction of the neutron exit window (50), leaving substantially free at least one end (21, 22) of the cold moderator (20) at the end (11, 12).WO