Cf-252 Neutron Source Multiplier Assembly

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Solution Overview

Problem

Current neutron sources for nuclear reactors and industrial applications are inefficient in utilizing the radioactive energy of californium-252 (252Cf), as only 3.1% of its decay events result in spontaneous fission neutrons, while the remaining energy is lost as high-energy alpha decays, and the use of beryllium is hazardous due to toxicity and limited availability of 252Cf.

Innovation Solution

A fast neutron emitting source multiplier assembly is created by combining a 252Cf driver source with a beryllium multiplier, where the beryllium (n,2n) reaction transforms a significant portion of 252Cf's radioactive energy into neutrons, and a shield curtain can be used to modulate neutron strength by stopping alpha particles, resulting in a nine-fold increase in neutron source strength per unit mass of 252Cf.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If californium-252 is used as a primary neutron source, then neutron source strength is improved, but the majority of radioactive energy (96.9%) is lost as alpha decays rather than producing neutrons

Engineering Contradiction:

Improveneutron source strengthVSAvoidradioactive energy loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The invention converts the harmful alpha particle emissions (which constitute 96.9% of Cf-252 decay and were previously wasted energy) into useful neutron production by introducing a beryllium multiplier. The alpha particles strike the beryllium nuclei, triggering (n,2n) reactions that transform these harmful decays into additional neutrons, thereby converting energy loss into energy gain.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The beryllium multiplier serves as an intermediary substance between the Cf-252 source and the neutron output. It mediates the energy transformation process by absorbing alpha particles and converting them into neutrons through nuclear reactions, enabling efficient utilization of the radioactive energy for neutron production.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If beryllium is used as a neutron multiplier, then neutron source strength is improved, but toxicity and limited availability become problematic

Engineering Contradiction:

Improveneutron source strengthVSAvoidtoxicity

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The invention segments the system into distinct functional components: a sealed Cf-252 driver source encapsulated in a reflective housing, and a separate beryllium multiplier assembly. This segmentation allows the toxic Cf-252 to be isolated in a hermetically sealed unit, protecting operators from exposure while maintaining the neutron multiplication function in a separate, controllable beryllium assembly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention employs a disposable sealed Cf-252 driver source that can be manufactured remotely and installed in the neutron source assembly. Once the Cf-252 decays or the source becomes problematic, the entire sealed driver unit can be removed and replaced without exposing personnel to the toxic material, effectively treating it as a disposable component that eliminates long-term handling risks.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Power

If more beryllium is used to increase neutron multiplication, then neutron source strength increases, but the amount of required 252Cf decreases, extending source lifetime

Engineering Contradiction:

Improveneutron source strengthVSAvoid252Cf amount

Core Design Contradiction:

PowerVSQuantity of substance

Solution Approach 1:

The invention uses a preliminary action approach by pre-encapsulating the Cf-252 driver source in a hermetically sealed reflective housing before installation. This preliminary preparation allows the source to be manufactured remotely under controlled conditions and then simply installed in the neutron source assembly, eliminating the need for ongoing handling or adjustment of the toxic Cf-252 material and enabling the system to operate with minimal 252Cf quantities.

Inventive Principle:

Principle #10Preliminary action

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 approach reduces the required amount of 252Cf by approximately 8 times, extending the source's lifetime and increasing neutron source strength, while minimizing beryllium usage and addressing toxicity concerns through remote manufacturing and efficient energy transformation.

Implementation Method 1

only 3.1% of its decay events result in spontaneous fission neutrons

Methodology Applied

Scientific EffectSpontaneous fission: Nuclear Fission

Implementation Method 2

the remaining energy is lost as high-energy alpha decays

Methodology Applied

Scientific EffectAlpha decay: Radioactive Decay

Implementation Method 3

the beryllium (n,2n) reaction transforms a significant portion of 252Cf's radioactive energy into neutrons

Methodology Applied

Scientific EffectBeryllium (n,2n) reaction: Nuclear Fission

Implementation Method 4

a shield curtain can be used to modulate neutron strength by stopping alpha particles

Methodology Applied

Scientific EffectAlpha particle absorption: Absorption (physical)

Data Source

PatentEP2625696B1Primary neutron source multiplier assembly

Publication Date: 2018.03.07 WESTINGHOUSE ELECTRIC CORP

Figure 1
Figure 2A~2B
Figure 3A~3B

AI summary

A neutron emitting assembly, which is useful in nuclear reactors and other industrial applications, is made of a major amount of beryllium encapsulating a minor amount of 252Cf, which can be placed in a capsule having end plugs and a holding spring.