Page 8 - Enclosure Fall-Winter 2023-24

Embedded Digital Devices

In the CGD Process

Including Safety Integrity Level Certification

By: John R. Hendricks, PE

Curtiss-Wright Nuclear

INTRODUCTION A recent acceptable approach for procuring and
accepting commercial grade digital equipment is to obtain
Glovebox designers and fabricators have been procuring an IEC 61508 safety integrity level (SIL) Certification.
analog components for the design and construction Utilizing IEC 61508 only applies to the dependability
of gloveboxes including sensors, actuated doors, critical characteristics (CC) and physical and performance
switches, lights, motors, cranes, fire suppression systems, CC still needs to be performed. IEC 61508 certifications
environmental monitoring systems, air flow monitors, most be issued by a functional certifying body (CB) that has
radiation monitors, HVAC systems, and others. Glovebox been accredited to ISO 17065 by an accreditation body
designers or integrators select commercial components (AB) who is a signatory of the International Accreditation
for their glovebox design from catalogs. Commercial Forum (IAF) Multi-Lateral Agreement (MLA) May be used
components suppliers are constantly updating their to address Dependability.
products with digital content to remove cost, improve
reliability, address sub-component obsolescence, and Embedded Digital Devices (EDD) are items that include
increase their competitive advantage. Generally, there is digital components with executable code or software-
no change in the commercial component suppliers model developed programmable logic that is permanently
number because the commercial component suppliers or semi-permanently installed within the device and is
consider the item to be identical in terms of form, fit, and commonly referred to as firmware. Firmware includes,
function, thereby challenging the selection of components but may not be limited to, devices such as programmable
for usage in the Glovebox design process. Increasingly, logic devices, field programmable gate arrays, application
components that have been entirely analog are being specific integrated circuits, erasable programmable read
produced with Embedded Digital Devices (EDD). only memory, and complex programmable logic devices.
A digital item is configurable in the sense that programs
The most effective way to address EDDs is to identify
this characteristic at the design stage. The impact of not and/or configuration data can be loaded and stored on it.
In some cases, the configuration is controlled only by the
discovering embedded digital devices (EDDs) in the design commercial component suppliers, and in other cases the
and fabricators process can result in costly schedule delay. configuration is controlled by the end user. User controlled
For example, EDD can result in $100,000’s of increased configurations are only possible by use of factory-controlled
procurement cost with a significant schedule delay of 6-12 configuration tools or interfaces that enable the user to
months. EDD are installation in locations where radiation program or set application-specific functions. In many
levels are below 1000 Rad. Historically radiation levels of cases, a digital item will be supplied with both a factory-
10,000 Rad for analog components was typical.
controlled internal configuration and tools or interfaces
Screening for digital content can be performed using that enable the user to program or set application-specific
supplier information during the evaluation process. This functions.
paper will present methodologies for addressing EDDs in The increasing use of microprocessor has introduced
the commercial grade dedication of commercial off-the- concerns because of the potential creation of additional
shelf items. EDD can introduce failure modes that should noise sources and the susceptibility of the equipment to
be evaluated during commercial grade dedication and the the electrical noise already present in a nuclear plant’s
equipment qualification process. These methodologies can environment. Additionally, performance advancements
be used by Glovebox design and integrators to recognize may have an adverse impact on a digital system’s operation,
EDD parameters in manufacturer’s literature, or during the especially regarding Electromagnetic Interference and
technical evaluation and verification process.
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