IEC 62396-5:2014

Process management for avionics - Atmospheric radiation effects - Part 5: Assessment of thermal neutron fluxes and single event effects in avionics systems

IEC 62396-5:2014(E) provides a more precise definition of the threat that thermal neutrons pose to avionics as a second mechanism for inducing single event upset (SEU) in microelectronics. IEC 62396-5 addresses two main items:
- a detailed evaluation of the existing literature on measurements of the thermal flux inside of airliners, and
- an enhanced compilation of the thermal neutron SEU cross-section in currently available SRAM devices (more than 20 different devices). The net result of the reviews of these two different sets of data will be two ratios that are considered to be very important for leading to the ultimate objective of determining how large a threat is. This new edition includes the following technical changes with respect to the previous technical specification: document upgraded to an IEC international standard, change to title, updated references and bibliography, consideration of smaller geometries, addition of recent data on neutron cross-sections, etc.

General Information

• Status: Published
• Publication Date: 21-Aug-2014
• ICS: 03.100.50 - Production. Production management
• ICS: 31.020 - Electronic components in general
• ICS: 49.060 - Aerospace electric equipment and systems
• Technical Committee: TC 107 - Process management for avionics
• Current Stage: PPUB - Publication issued
• Start Date: 15-Sep-2014
• Completion Date: 22-Aug-2014

Relations

• Replaces: IEC TS 62396-5:2008 - Process management for avionics - Atmospheric radiation effects - Part 5: Guidelines for assessing thermal neutron fluxes and effects in avionics systems
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 62396-5 ®
Edition 1.0 2014-08
INTERNATIONAL
STANDARD
colour
inside
Process management for avionics – Atmospheric radiation effects –
Part 5: Assessment of thermal neutron fluxes and single event effects in
avionics systems
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IEC 62396-5 ®
Edition 1.0 2014-08
INTERNATIONAL
STANDARD
colour
inside
Process management for avionics – Atmospheric radiation effects –

Part 5: Assessment of thermal neutron fluxes and single event effects in

avionics systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
S
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-8322-1821-1

– 2 – IEC 62396-5:2014  IEC 2014
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 5
4 Overview of thermal neutron single event rate calculation . 5
5 Thermal neutron flux inside an airliner . 7
5.1 Definition of thermal neutron . 7
5.2 Overview. 7
5.3 Background on aircraft measurements . 7
5.4 Calculational approach . 8
5.5 Processing of in-flight neutron flux data . 9
6 Thermal neutron SEU cross-sections . 13
6.1 Overview of the issue . 13
6.2 Mechanism involved . 13
6.3 Thermal neutron SEU cross-sections and Ratio-2 . 15
7 Recommendation for devices in avionics at the present time . 17
7.1 General . 17
7.2 Ratio-1 . 17
7.3 Ratio-2 . 18
7.4 Thermal neutron upset rate . 18
8 Determining thermal neutron SEE rates for use in equipment assessments . 18
8.1 Demonstration of thermal neutron immunity to SEE . 18
8.1.1 Thermal neutron test . 18
8.1.2 Absence of boron 10 (B10) . 18
8.2 Determination of thermal neutron SEE where there is no evidence of thermal
neutron immunity . 19
8.2.1 Results from thermal neutron testing . 19
8.2.2 Conservative estimation . 19
8.2.3 High voltage devices . 19
9 Single event burn out in high voltage devices due to thermal neutrons . 19
Bibliography . 20

Figure 1 – Atmospheric neutron spectra measured in four aircraft . 10
Figure 2 – Neutron cross-sections for boron-10 including total cross-section (red), total
elastic cross-section (green) and (n,α) nuclear capture cross-section (blue) . 15

Table 1 – Tabulation of the various atmospheric neutron measurements used . 9
Table 2 – Comparison of thermal and high energy neutron fluxes and their ratios . 11
Table 3 – Calculated neutron fluxes in the Boeing 747 structure . 12
Table 4 – SRAM SEU cross-sections induced by thermal and high energy neutrons . 16

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 5: Assessment of thermal neutron
fluxes and single event effects in avionics systems

FOREWORD
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International Standard IEC 62396-5 has been prepared by IEC technical committee 107:
Process management for avionics.
This first edition cancels and replaces the first edition of IEC/TS 62396-5 published in 2008.
This edition constitutes a technical revision.
This edition includes the following technical changes with respect to the previous technical
specification:
a) Change to title.
b) Updated references and bibliography.
c) Subclause 6.2 expanded to consider smaller geometry devices.

– 4 – IEC 62396-5:2014  IEC 2014
d) Table 4 neutron cross-sections expanded to add more recent data and the ratio between
thermal and high energy neutron cross-section amended to 2,42 from 2,77.
e) Addition of reference section on thermal neutron high voltage burn out.
f) New clause on determination of thermal neutron SEE rates for use in equipment
assessments.
g) Document aligned as an IEC standard.
The text of this international standard is based on the following documents:
FDIS Report on voting
107/237/FDIS 107/242/RVD
Full information on the voting for the approval of this international standard can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62396 series, published under the general title Process
management for avionics – Atmospheric radiation effects, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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colour printer.
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 5: Assessment of thermal neutron
fluxes and single event effects in avionics systems

1 Scope
The purpose of this part of IEC 62396 is to provide a more precise definition of the threat that
thermal neutrons pose to avionics as a second mechanism for inducing single event upset
(SEU) in microelectronics. There are two main points that will be addressed in this part of
IEC 62396:
a) a detailed evaluation of the existing literature on measurements of the thermal flux inside
of airliners, and
b) an enhanced compilation of the thermal neutron SEU cross-section in currently available
SRAM devices (more than 20 different devices).
The net result of the reviews of these two different sets of data will be two ratios that are
considered to be very important for leading to the ultimate objective of how large a threat is
the SEU rate from thermal
...