Title: Deciding when defence in depth control strategies are necessary for risk management and crisis response

Authors: Marcus Seidl; Xiang Wang

Addresses: Department of fuel Management and Disposal, PreussenElektra GmbH, Tresckowstrasse 5, 30456 Hannover, Germany ' College of Nuclear Science and Technology, Harbin Engineering University, 145 Nantong St., 15000, 1 Harbin, China

Abstract: Defence in depth is a time-tested strategy in some technical fields, such as cybersecurity or nuclear reactor technology. In view of potentially devasting consequences of exponential growth, the implementation of such a strategy is almost self-evident in this case. Less obvious is a formal explanation of why and when such a control strategy is necessary compared to traditional risk management approaches and which systems or organisations can benefit from it. Quantitative arguments are given based on the properties of heavy tail stochastic variables. Particularly, their single big-jump property provides the rationale to require a hierarchy of barriers for containment of a cascade of daughter events. The COVID-19 pandemic has vividly demonstrated how difficult it is to implement an appropriate control strategy under these circumstances. Concretely, it is shown that the spread of transport vectors in this case has heavy tail properties and consequently requires a defence in depth response.

Keywords: defence in depth; heavy tail; COVID-19; precautionary principle; exponential growth; chain reaction; self-reinforcing process.

DOI: 10.1504/IJRAM.2023.132330

International Journal of Risk Assessment and Management, 2023 Vol.26 No.1, pp.44 - 57

Received: 06 Apr 2022
Received in revised form: 03 Oct 2022
Accepted: 05 Dec 2022
Published online: 18 Jul 2023 *

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