Comparing identification of human failure events with two HRA methods in an ex- control room action

Ilkka Karanta; Essi Immonen

doi:10.3850/ESREL2026061419_esrel26-p27747-cd

Comparing identification of human failure events with two HRA methods in an ex- control room action

Ilkka Karanta^*
, Essi Immonen

^*Corresponding author for this work

BA4503 Severe accident analysis

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

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Abstract

We compare two human reliability assessment methods, THERP and Phoenix, in human failure event (HFE) identification in an ex-control room setting. First, we consider briefly what HFE identification should encompass. Then we introduce the example scenario used, a part of a post-earthquake scenario where two operators attempt to even out water levels in steam generators utilizing an emergency water source. We describe briefly how HFE identification is conducted in the two methods, and conduct HFE identification in the scenario with each method. We compare the methods by conducting HFE identification with them on the example scenario. A major difference between the two is that THERP is procedure-based whereas Phoenix is model-based. Another difference is that THERP does not guide HFE identification much, which gives analysts freedom to apply their judgment, but may lead to considerable differences in analysis results by different analysts. In contrast, the HFE
identification process of Phoenix is structured, model-based and with considerable guidance, and therefore likely promotes reduction of differences in analysis results between different analysts.

Original language	English
Title of host publication	Proceedings of the European Safety and Reliability Conference (ESREL 2026)
Editors	José C. Matos, Paulo B. Lourenco, Michael Beer, Daniel Oliveira, Edoardo Patelli, Hélder S. Sousa, Rui A. Silva, Monica Santamaria, Chiara Turco
Publisher	Research Publishing Services
Pages	460-467
ISBN (Electronic)	978-981-94-6718-1
DOIs	https://doi.org/10.3850/ESREL2026061419_esrel26-p27747-cd
Publication status	Published - Jun 2026
MoE publication type	A4 Article in a conference publication
Event	European Safety and Reliability Conference ESREL 2026 - Braga, Portugal Duration: 14 Jun 2026 → 19 Jun 2026

Conference

Conference	European Safety and Reliability Conference ESREL 2026
Country/Territory	Portugal
City	Braga
Period	14/06/26 → 19/06/26

Funding

The study has been partly funded by Finnish National Nuclear Waste Management Fund through SAFER2028 research programme. The scenario considered in this paper, together with support materials, has been supplied by Fortum E&P corporation.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 11 Sustainable Cities and Communities

Keywords

human reliability analysis
human failure event
ex-control room action
THERP
Phoenix
seismic

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10.3850/ESREL2026061419_esrel26-p27747-cd

esrel26-p27747

Cite this

Karanta, I., & Immonen, E. (2026). Comparing identification of human failure events with two HRA methods in an ex- control room action. In J. C. Matos, P. B. Lourenco, M. Beer, D. Oliveira, E. Patelli, H. S. Sousa, R. A. Silva, M. Santamaria, & C. Turco (Eds.), Proceedings of the European Safety and Reliability Conference (ESREL 2026) (pp. 460-467). Research Publishing Services. https://doi.org/10.3850/ESREL2026061419_esrel26-p27747-cd

Karanta, Ilkka ; Immonen, Essi. / Comparing identification of human failure events with two HRA methods in an ex- control room action. Proceedings of the European Safety and Reliability Conference (ESREL 2026). editor / José C. Matos ; Paulo B. Lourenco ; Michael Beer ; Daniel Oliveira ; Edoardo Patelli ; Hélder S. Sousa ; Rui A. Silva ; Monica Santamaria ; Chiara Turco. Research Publishing Services, 2026. pp. 460-467

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title = "Comparing identification of human failure events with two HRA methods in an ex- control room action",

abstract = "We compare two human reliability assessment methods, THERP and Phoenix, in human failure event (HFE) identification in an ex-control room setting. First, we consider briefly what HFE identification should encompass. Then we introduce the example scenario used, a part of a post-earthquake scenario where two operators attempt to even out water levels in steam generators utilizing an emergency water source. We describe briefly how HFE identification is conducted in the two methods, and conduct HFE identification in the scenario with each method. We compare the methods by conducting HFE identification with them on the example scenario. A major difference between the two is that THERP is procedure-based whereas Phoenix is model-based. Another difference is that THERP does not guide HFE identification much, which gives analysts freedom to apply their judgment, but may lead to considerable differences in analysis results by different analysts. In contrast, the HFE identification process of Phoenix is structured, model-based and with considerable guidance, and therefore likely promotes reduction of differences in analysis results between different analysts.",

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Karanta, I & Immonen, E 2026, Comparing identification of human failure events with two HRA methods in an ex- control room action. in J C. Matos, P B. Lourenco, M Beer, D Oliveira, E Patelli, H S. Sousa, R A. Silva, M Santamaria & C Turco (eds), Proceedings of the European Safety and Reliability Conference (ESREL 2026). Research Publishing Services, pp. 460-467, European Safety and Reliability Conference ESREL 2026, Braga, Portugal, 14/06/26. https://doi.org/10.3850/ESREL2026061419_esrel26-p27747-cd

Comparing identification of human failure events with two HRA methods in an ex- control room action. / Karanta, Ilkka ; Immonen, Essi.
Proceedings of the European Safety and Reliability Conference (ESREL 2026). ed. / José C. Matos; Paulo B. Lourenco; Michael Beer; Daniel Oliveira; Edoardo Patelli; Hélder S. Sousa; Rui A. Silva; Monica Santamaria; Chiara Turco. Research Publishing Services, 2026. p. 460-467.

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

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AU - Immonen, Essi

N1 - "This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the ESREL 2026 Organisers or the Publisher."

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N2 - We compare two human reliability assessment methods, THERP and Phoenix, in human failure event (HFE) identification in an ex-control room setting. First, we consider briefly what HFE identification should encompass. Then we introduce the example scenario used, a part of a post-earthquake scenario where two operators attempt to even out water levels in steam generators utilizing an emergency water source. We describe briefly how HFE identification is conducted in the two methods, and conduct HFE identification in the scenario with each method. We compare the methods by conducting HFE identification with them on the example scenario. A major difference between the two is that THERP is procedure-based whereas Phoenix is model-based. Another difference is that THERP does not guide HFE identification much, which gives analysts freedom to apply their judgment, but may lead to considerable differences in analysis results by different analysts. In contrast, the HFE identification process of Phoenix is structured, model-based and with considerable guidance, and therefore likely promotes reduction of differences in analysis results between different analysts.

AB - We compare two human reliability assessment methods, THERP and Phoenix, in human failure event (HFE) identification in an ex-control room setting. First, we consider briefly what HFE identification should encompass. Then we introduce the example scenario used, a part of a post-earthquake scenario where two operators attempt to even out water levels in steam generators utilizing an emergency water source. We describe briefly how HFE identification is conducted in the two methods, and conduct HFE identification in the scenario with each method. We compare the methods by conducting HFE identification with them on the example scenario. A major difference between the two is that THERP is procedure-based whereas Phoenix is model-based. Another difference is that THERP does not guide HFE identification much, which gives analysts freedom to apply their judgment, but may lead to considerable differences in analysis results by different analysts. In contrast, the HFE identification process of Phoenix is structured, model-based and with considerable guidance, and therefore likely promotes reduction of differences in analysis results between different analysts.

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A2 - Santamaria, Monica

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PB - Research Publishing Services

T2 - European Safety and Reliability Conference ESREL 2026

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Karanta I , Immonen E. Comparing identification of human failure events with two HRA methods in an ex- control room action. In C. Matos J, B. Lourenco P, Beer M, Oliveira D, Patelli E, S. Sousa H, A. Silva R, Santamaria M, Turco C, editors, Proceedings of the European Safety and Reliability Conference (ESREL 2026). Research Publishing Services. 2026. p. 460-467 doi: 10.3850/ESREL2026061419_esrel26-p27747-cd

Comparing identification of human failure events with two HRA methods in an ex- control room action

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UN SDGs

Keywords

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