Transient Radiation Effects
on Electronics

Electronics and hardening

For more than 40 years, NUCLETUDES has pioneered in setting up the basic means and methods to harden systems exposed to neutrons, protons, X and ϒ photons, electrons, or heavy ions and to harsh electromagnetic environments. For nuclear industry applications, this hardening activity is typically performed for equipment nuclearization.

In this frame, NUCLETUDES has developed unique methods and skills to address the issue of electronics survivability to such aggressions, whether they come from a nuclear explosion, the natural or some specific artificial environment (nuclear power plant, accelerator,…).

The functional effects created by these rays or particles in the equipments are:

• transient perturbations that may cause dysfunctions at equipment and system levels,
• equipment performance degradation,
• local or general destruction at equipment level.
  

 Whatever the feared effect is, the same approach is followed:

• vulnerability threshold assessment,
• comparison between the vulnerability threshold and the aggression level,
• design modification allowing for an increase of the vulnerability level above the aggression level with the required margin,
• hardened design validation and qualification.

 
Vulnerability and hardening to radiation and electromagnetic environments

Electronic, opto-electronic and electromechanical components are the most sensitive elements. One needs to also consider the sensitivity of optical fibers and optics to radiations.

Radiations effects on electronic components can be divided into two categories:

• transient effects resulting from transient radiations or from the interaction of single particles with the atomic structure of the component,
• permanent effects resulting from the accumulation of ionizing rays in the elementary electronic structure of the component.
  

 The following transient effects are typically considered:

• functional perturbations induced by a quasi-instantaneous flux of high energy photons (nuclear explosion) or electrical constraints induced by electromagnetic couplings,
• Single Event Transients (or SETs) generated by the interaction of heavy particles with the electronic component.
  

 The different types of permanent effects are listed hereunder:

• performance degradation due to the combination of different radiation effects (total ionizing dose, neutrons fluence) that may reach a functional destruction,
• electrical state evolutions,
• destructions induced by a single shot aggression (Single Event Burn-Out or SEB, ionizing dose rate, electrical constraints due to electromagnetic couplings),
• logical state freezing due to a single shot aggression.
  

Methodology

The hardening methodology is based on a 2-step approach:

• equipment vulnerability assessment,
• identification of the additional protections to be implemented before going into the hardening validation/qualification process.

Vulnerability assessment

Design-to-hardening and vulnerability studies require to follow the steps listed below :

• design rules and electronic components policy set up,
• parts and technologies selection,
• electronics expertise (architecture, diagrams, data sheets analysis) based on vulnerability studies including simulations and tests,
• characterization of components under radiation exposure (definition of hardened electronic devices to activate the component during the test, implementation and exploitation of irradiation tests on electronic components and complete equipment : see components testing page),
• the use of in-house software tools (e.g. SEE cross section assessment, heavy ions energy deposition computation, behavioral simulation for electronic functions).

Additional protections definition

The previous phase gave the level of sensitivity of the equipment with respect to the specified radiations and electromagnetic constraints.

When the sensitivity level of the equipment is above the objective, NUCLETUDES proposes improvements such as :

• shielding design and modeling (radiations and electromagnetic environments),
• design modification recommendations to reach the required immunity.

Once agreed by the equipment manufacturer, these design modifications are validated through simulation and tests under radiation exposure at function or equipment level.

The process ends with the qualification step consisting in submitting the complete equipment to the specified constraints.