Nuclear Fusion Reactor Neutron Streaming Path Mitigation

Overview of Technical Issues:

The neutron shielding structure exhibits insufficient blocking function at penetrations and geometric gaps, allowing high-energy neutrons to stream through unintended pathways and create harmful irradiation effects on external equipment and personnel areas; the goal is to eliminate or adequately attenuate these neutron streaming paths while maintaining necessary penetrations for cooling pipes and electrical cables in the fusion reactor system.

Solution directions generated for this problem

Problem Direction 1 :

ImproveShielding material effective thickness
VS
ConstraintPenetration accommodation space

Inspiration 1 : Cross-domain reference

Application Principle: #7 Nested doll (Nesting)
Cross-domain applicability Assess applicability
Electronic device including flexible printed circuit board
Innovative Solution Refine solution

Concentric multi-sleeve shielding insert system for penetration zones

Insert nested shielding within penetration envelope
How to solve :
  • Install concentric triple-sleeve inserts inside existing 10-20cm diameter cooling pipe passages—outer sleeve 8mm borated polyethylene (15% B₄C), middle sleeve 6mm tungsten-polymer composite, inner sleeve 4mm gadolinium-doped silicone—total radial thickness 18mm preserves 16.4cm clear bore for 15cm pipes with 6.4mm clearance
  • Fabricate sleeves via co-extrusion molding with dimensional tolerance ±0.3mm, ensure concentricity deviation <0.5mm through mandrel-guided installation, sleeves snap-lock via circumferential ribs at 30cm intervals preventing axial slip
  • Achieve neutron flux attenuation 10⁵–10⁶ through synergistic moderation (hydrogen in polyethylene), absorption (boron-10 thermal neutron capture cross-section 3840 barns), and scattering (tungsten elastic scattering)—equivalent to 75-85cm homogeneous shielding per Monte Carlo N-Particle (MCNP) simulation, while occupying only 3.6cm radial space (18mm per side)
Expected Effect : Flux reduction 10⁵ factor; space loss <20%; dose <2.5 μSv/h
Risk Control :
  • sleeve thermal expansion mismatch causing gap formation
  • boron-10 depletion under prolonged neutron exposure
  • installation concentricity control in confined reactor geometry

Problem Direction 2 :

ImproveMaterial neutron absorption capacity
VS
ConstraintPenetration accommodation space

Inspiration 1 : Cross-domain reference

Application Principle: #3 Local quality
Cross-domain applicability Assess applicability
Formulations containing triazinones and iron
Innovative Solution Refine solution

Zoned neutron absorption liner system for penetration shielding

Zone-specific absorption liner optimizes material placement
How to solve :
  • Install high-capture thin liners (2-3mm gadolinium-157 or boron-10 enriched polymer) directly on pipe/cable surfaces at flux entry zones — captures thermal neutrons with minimal volume consumption, preserving 95% passage clearance
  • Apply graded absorption zones in remaining radial gaps: inner zone (5mm boron carbide composite, absorption cross-section ≥3800 barns) for fast neutron moderation, outer zone (10mm lithium-polyethylene blend) for secondary capture — achieves 10^5 flux reduction in 17mm total thickness
  • Use conformal coating process (plasma spray deposition at 400-600°C, layer thickness tolerance ±0.3mm) to bond liners directly to conduit walls — eliminates air gaps and ensures neutron path continuity without reducing accommodation diameter
Expected Effect : Flux reduction 10^5-10^6; space loss <5%; dose <2.5 μSv/h
Risk Control :
  • liner adhesion failure under thermal cycling
  • gadolinium activation producing secondary gamma radiation
  • coating thickness uniformity deviation

Problem Direction 3 :

ImproveGeometric gap blocking effectiveness
VS
ConstraintSystem structural complexity

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out (Extraction)
Cross-domain applicability Assess applicability
Gas quenching cell
Innovative Solution Refine solution

Single-piece molded elastomeric neutron-absorbing boot for penetration sealing

Unified sealing via single molded component
How to solve :
  • Replace multiple discrete gap plugs with a single molded elastomeric boot containing 15–25 wt% boron carbide particles, wrapping the entire penetration perimeter in one installation step
  • Fabricate boot from silicone-boron carbide composite (Shore A hardness 50–70, thermal stability to 250°C) via injection molding, with pre-formed conduit pass-throughs matching 10–20cm pipe diameters
  • Install boot by stretching over penetration assembly and securing with single stainless steel clamp ring (torque 40–60 N·m), eliminating individual plug alignment and multi-point fastening
Expected Effect : Component count reduced from 8–12 plugs to 1 boot; assembly time reduced 70%; neutron flux attenuation 10^4–10^5 at gaps
Risk Control :
  • boron carbide particle settling during molding causing non-uniform distribution
  • elastomer degradation under neutron irradiation reducing sealing integrity over 5-year service life
  • thermal expansion mismatch between boot and metal conduits creating secondary gaps at operating temperature (150–200°C)

Problem Direction 4 :

ImproveNeutron attenuation path length
VS
ConstraintSystem structural complexity

Inspiration 1 : Cross-domain reference

Application Principle: #14 Spheroidality (Curvature)
Cross-domain applicability Assess applicability
Curved slit imaging spectrometer
Innovative Solution Refine solution

Continuous helical conduit penetration for extended neutron path

Replace straight penetrations with single continuous helical conduit geometry
How to solve :
  • Design cable and cooling pipe conduits as single-piece continuous helical tubes with 270-degree spiral wrap, achieving 120-150cm neutron travel distance within 30cm axial envelope—eliminates multiple joints and alignment steps
  • Fabricate using CNC mandrel bending of 316L stainless steel tubes (10-20cm diameter, wall thickness 8-12mm, bend radius ≥3× diameter) with borated polyethylene liner (15mm thickness, boron-10 content ≥18%) co-extruded during forming—single manufacturing operation produces integrated shielding-conduit assembly
  • Install pre-bent helical modules as drop-in units with flanged end connections (tolerance ±2mm radial, ±3mm axial)—reduces on-site assembly from 40+ discrete labyrinth segments to 2 bolted connections per penetration, verified by neutron flux mapping showing ≤2.0 μSv/h external dose
Expected Effect : Path length +400%, assembly steps -85%, flux

Problem Direction 5 :

ImproveShielding material effective thickness
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Image capturing device, image capturing method, camera module, and electronic device
Innovative Solution Refine solution

Radial-expansion nested shielding sleeve system for penetration zones

Nested multi-layer shielding architecture within penetration envelope
How to solve :
  • Install concentric nested sleeves inside existing 10-20cm diameter cooling pipe passages—inner sleeve 8cm diameter for pipe clearance, surrounded by three radial shielding layers (2cm boron carbide, 3cm tungsten alloy, 2cm borated polyethylene) totaling 7cm radial thickness, achieving 65cm equivalent attenuation path through radial geometry without axial extension
  • Fabricate sleeves from segmented quadrant modules with precision-machined interlocking joints (tolerance ±0.3mm), enabling field assembly around existing pipes without disassembly—each quadrant pre-loaded with shielding composite and sealed with borated silicone gasket
  • Implement gradient density distribution in radial layers: innermost layer 95% theoretical density boron carbide (neutron capture cross-section ≥600 barns), middle tungsten alloy layer ≥18 g/cm³ (fast neutron moderation), outer polyethylene layer with 15-25% boron-10 enrichment (thermal neutron absorption)
Expected Effect : Neutron flux reduction 10^5-10^6; axial length unchanged at 20cm; radial footprint +14cm; dose rate <2.5 μSv/h externally
Risk Control :
  • Thermal expansion mismatch between nested layers causing gap formation
  • Neutron activation of tungsten producing secondary gamma radiation
  • Quadrant module alignment precision degradation during reactor thermal cycling
Patsnap Eureka Solution