External Hazards - Revision history

Admin: 1 revision imported

2026-07-30T00:10:12Z

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en>Admin: /* External Hazards */

2026-07-24T16:35:54Z

External Hazards

← Older revision		Revision as of 16:35, 24 July 2026
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	==External Hazards==		==External Hazards==
			===<span style="color:black; background-color:{{{2\|yellow}}}">New Research</span><noinclude>===
			'''Collocated Industrial Facilities'''

			Colocation of nuclear power plants with industrial facilities may introduce new external hazards, such as combustion loads and heat or electrical load rejection from the end user. In existing assessments, potential events have been identified and discussed from a very specific focus, such as risk from electrolytic hydrogen production and storage, but no overarching assessment has been performed that covers a comprehensive set of interactions.

			The objective of future research regarding collocated industrial facilities is to perform a comprehensive assessment of potential effects on the technical elements of a nuclear plant PRA and assess the potential changes in magnitude, frequency, or consequences of accident scenarios affected by the type of collocated industrial facility. The assessment plans to select a representative set of advanced reactor designs and industrial applications as the basis for the evaluation to produce insights for a broad range of reactor designs and industrial facilities.

			'''Rare Seismic Events'''

			While the Licensing Modernization Project (LMP) aims to provide flexibility and cost efficiency through performance-based criteria, its frequency-consequence (F-C) target of 5E-7/yr for high-consequence Beyond Design Basis Events (BDBEs) can lead to overly conservative seismic requirements for structural design. Analyses show that meeting this target would require increasing design-basis ground motions by up to three times current U.S. Nuclear Regulatory Commission (USNRC) criteria, significantly raising costs without proportional safety benefits.

			The following path is recommend for RIPB seismic design of SSCs
			in advanced reactors, consistent with LMP from NEI 18-04 [[References\|[8]]] and based on EPRI [https://www.epri.com/research/products/000000003002032031 3002032031] [[References\|[72]]]:

			*For safety-related SSCs, the DBHL earthquake need not exceed the GMRS defined according to RG 1.208.
			*High-consequence seismic BDBEs are allowed to exceed the F-C target provided that the union of these BDBEs demonstrates a seismic margin (HCLPF capacity) equal to at least 1.67 times the GMRS; and the cumulative risk metrics acceptance criteria or USNRC-endorsed surrogates (such as being developed in ANL/NSE-24/42 [9]) are met.
			*The seismic design basis for non-safety related SSCs may follow commercial design codes and standards with special treatment as warranted to risk-significant SSCs.

			===Historical===

	One of the main conclusions of [https://nucleus.iaea.org/sites/smr/Lists/Publications/DispForm.aspx?ID=130 TECDOC 1487] [[References\| [42]]] is that “the development of an external event PRA in parallel with the early plant design may help to identify the vulnerabilities as well as potentially overly conservative design features at an early stage, leading to a well-balanced and cost-effective improvement in safety”. Therefore a core issue that needs to be clearly addressed moving forward is the balance between the cost and benefit of developing detailed External Events PRA models with insights that can be used to adequately and robustly screen external events that may otherwise be expected to be fully included (e.g., is such an approach feasible, justifiable; can a graded approach be provided that accounts for increased margin to safety goals with sufficient consideration of uncertainty and degree of confidence). In relation to the section describing passive system reliability, a large part of determining the uncertainty of a passive system is being able to determine the risk associated with certain external events and how it relates to the designed passive safety systems. For example, external events have the potential to change assumed system boundary conditions which could result in the failure of the passive system to successfully perform its intended safety function.		One of the main conclusions of [https://nucleus.iaea.org/sites/smr/Lists/Publications/DispForm.aspx?ID=130 TECDOC 1487] [[References\| [42]]] is that “the development of an external event PRA in parallel with the early plant design may help to identify the vulnerabilities as well as potentially overly conservative design features at an early stage, leading to a well-balanced and cost-effective improvement in safety”. Therefore a core issue that needs to be clearly addressed moving forward is the balance between the cost and benefit of developing detailed External Events PRA models with insights that can be used to adequately and robustly screen external events that may otherwise be expected to be fully included (e.g., is such an approach feasible, justifiable; can a graded approach be provided that accounts for increased margin to safety goals with sufficient consideration of uncertainty and degree of confidence). In relation to the section describing passive system reliability, a large part of determining the uncertainty of a passive system is being able to determine the risk associated with certain external events and how it relates to the designed passive safety systems. For example, external events have the potential to change assumed system boundary conditions which could result in the failure of the passive system to successfully perform its intended safety function.

Admin: 1 revision imported

2025-01-24T18:23:31Z

1 revision imported

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Admin: /* External Hazards */

2025-01-17T21:51:30Z

External Hazards

← Older revision		Revision as of 21:51, 17 January 2025
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	__FORCETOC__		__FORCETOC__
	==Purpose==		==Purpose==
	Taking External Hazards into account is an important part of quantifying the reliability of advanced reactor designs. While extreme external hazards can be very rare, it is important that they are still considered as one extreme external event can quickly lead to total plant failure, as seen in the ~~Fukushima~~ Daiichi accident.		Taking External Hazards into account is an important part of quantifying the reliability of advanced reactor designs. While extreme external hazards can be very rare, it is important that they are still considered as one extreme external event can quickly lead to total plant failure, as seen in the Fukashima Daiichi accident.

	==Scope==		==Scope==
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	One of the main conclusions of [https://nucleus.iaea.org/sites/smr/Lists/Publications/DispForm.aspx?ID=130 TECDOC 1487] [[References\| [42]]] is that “the development of an external event PRA in parallel with the early plant design may help to identify the vulnerabilities as well as potentially overly conservative design features at an early stage, leading to a well-balanced and cost-effective improvement in safety”. Therefore a core issue that needs to be clearly addressed moving forward is the balance between the cost and benefit of developing detailed External Events PRA models with insights that can be used to adequately and robustly screen external events that may otherwise be expected to be fully included (e.g., is such an approach feasible, justifiable; can a graded approach be provided that accounts for increased margin to safety goals with sufficient consideration of uncertainty and degree of confidence). In relation to the section describing passive system reliability, a large part of determining the uncertainty of a passive system is being able to determine the risk associated with certain external events and how it relates to the designed passive safety systems. For example, external events have the potential to change assumed system boundary conditions which could result in the failure of the passive system to successfully perform its intended safety function.		One of the main conclusions of [https://nucleus.iaea.org/sites/smr/Lists/Publications/DispForm.aspx?ID=130 TECDOC 1487] [[References\| [42]]] is that “the development of an external event PRA in parallel with the early plant design may help to identify the vulnerabilities as well as potentially overly conservative design features at an early stage, leading to a well-balanced and cost-effective improvement in safety”. Therefore a core issue that needs to be clearly addressed moving forward is the balance between the cost and benefit of developing detailed External Events PRA models with insights that can be used to adequately and robustly screen external events that may otherwise be expected to be fully included (e.g., is such an approach feasible, justifiable; can a graded approach be provided that accounts for increased margin to safety goals with sufficient consideration of uncertainty and degree of confidence). In relation to the section describing passive system reliability, a large part of determining the uncertainty of a passive system is being able to determine the risk associated with certain external events and how it relates to the designed passive safety systems. For example, external events have the potential to change assumed system boundary conditions which could result in the failure of the passive system to successfully perform its intended safety function.

	The impacts of external hazards will likely provide a substantially greater fraction of the contribution to risk to the public than is the experience from the current fleet of ~~LWRs~~. Because the current state of knowledge of potentially dominant very low frequency external hazards (phenomenology, event occurrence frequencies) is less developed than for internal events, the larger fractional contribution to overall risk will have a greater level of uncertainty. This situation also may require modifications to processes and criteria that have been used for the existing fleet of plants to assess and screen external hazards from consideration as providing a negligible contribution to PRA results. Some external events may be screened out through a deterministic and probabilistic process.		The impacts of external hazards will likely provide a substantially greater fraction of the contribution to risk to the public than is the experience from the current fleet of water reactors. Because the current state of knowledge of potentially dominant very low frequency external hazards (phenomenology, event occurrence frequencies) is less developed than for internal events, the larger fractional contribution to overall risk will have a greater level of uncertainty. This situation also may require modifications to processes and criteria that have been used for the existing fleet of plants to assess and screen external hazards from consideration as providing a negligible contribution to PRA results. Some external events may be screened out through a deterministic and probabilistic process.

	Research Roadmap (EPRI [https://www.epri.com/research/products/000000003002026495 3002026495]) actions supported for passive system reliability include:		Research Roadmap (EPRI [https://www.epri.com/research/products/000000003002026495 3002026495]) actions supported for passive system reliability include:

Admin at 15:38, 17 July 2024

2024-07-17T15:38:49Z

← Older revision		Revision as of 15:38, 17 July 2024
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	__FORCETOC__		__FORCETOC__
	==Purpose==		==Purpose==
	Taking External Hazards into account is an important part of quantifying the reliability of advanced reactor designs. While extreme external hazards can be very rare, it is important that they are still considered as one extreme external event can quickly lead to total plant failure, as seen in the ~~Fukashima~~ Daiichi accident.		Taking External Hazards into account is an important part of quantifying the reliability of advanced reactor designs. While extreme external hazards can be very rare, it is important that they are still considered as one extreme external event can quickly lead to total plant failure, as seen in the Fukushima Daiichi accident.

	==Scope==		==Scope==

Admin at 16:24, 10 July 2024

2024-07-10T16:24:28Z

← Older revision		Revision as of 16:24, 10 July 2024
Line 1:		Line 1:
			__FORCETOC__
	==Purpose==		==Purpose==
	Taking External Hazards into account is an important part of quantifying the reliability of advanced reactor designs. While extreme external hazards can be very rare, it is important that they are still considered as one extreme external event can quickly lead to total plant failure, as seen in the Fukashima Daiichi accident.		Taking External Hazards into account is an important part of quantifying the reliability of advanced reactor designs. While extreme external hazards can be very rare, it is important that they are still considered as one extreme external event can quickly lead to total plant failure, as seen in the Fukashima Daiichi accident.

Admin: /* External Hazards */

2024-07-10T16:09:39Z

External Hazards

← Older revision		Revision as of 16:09, 10 July 2024
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	*Demonstrate Risk-Informed and Performance Based Approach		*Demonstrate Risk-Informed and Performance Based Approach

	A higher level of detail for these actions can be found in the report.		A higher level of detail for these actions can be found in the [https://www.epri.com/research/products/000000003002026495 report].

Admin: /* External Hazards */

2024-07-05T23:33:59Z

External Hazards

← Older revision		Revision as of 23:33, 5 July 2024
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	The impacts of external hazards will likely provide a substantially greater fraction of the contribution to risk to the public than is the experience from the current fleet of LWRs. Because the current state of knowledge of potentially dominant very low frequency external hazards (phenomenology, event occurrence frequencies) is less developed than for internal events, the larger fractional contribution to overall risk will have a greater level of uncertainty. This situation also may require modifications to processes and criteria that have been used for the existing fleet of plants to assess and screen external hazards from consideration as providing a negligible contribution to PRA results. Some external events may be screened out through a deterministic and probabilistic process.		The impacts of external hazards will likely provide a substantially greater fraction of the contribution to risk to the public than is the experience from the current fleet of LWRs. Because the current state of knowledge of potentially dominant very low frequency external hazards (phenomenology, event occurrence frequencies) is less developed than for internal events, the larger fractional contribution to overall risk will have a greater level of uncertainty. This situation also may require modifications to processes and criteria that have been used for the existing fleet of plants to assess and screen external hazards from consideration as providing a negligible contribution to PRA results. Some external events may be screened out through a deterministic and probabilistic process.

	Roadmap actions supported for passive system reliability include:		Research Roadmap (EPRI [https://www.epri.com/research/products/000000003002026495 3002026495]) actions supported for passive system reliability include:
	*Develop Enhancements to Licensing Process		*Develop Enhancements to Licensing Process
	*Establish Decoupling Framework for Nuclear Beyond Electricity (NBE) Users		*Establish Decoupling Framework for Nuclear Beyond Electricity (NBE) Users

Admin: /* External Hazards */

2024-07-05T23:33:09Z

External Hazards

← Older revision		Revision as of 23:33, 5 July 2024
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	One of the main conclusions of [https://nucleus.iaea.org/sites/smr/Lists/Publications/DispForm.aspx?ID=130 TECDOC 1487] [[References\| [42]]] is that “the development of an external event PRA in parallel with the early plant design may help to identify the vulnerabilities as well as potentially overly conservative design features at an early stage, leading to a well-balanced and cost-effective improvement in safety”. Therefore a core issue that needs to be clearly addressed moving forward is the balance between the cost and benefit of developing detailed External Events PRA models with insights that can be used to adequately and robustly screen external events that may otherwise be expected to be fully included (e.g., is such an approach feasible, justifiable; can a graded approach be provided that accounts for increased margin to safety goals with sufficient consideration of uncertainty and degree of confidence). In relation to the section describing passive system reliability, a large part of determining the uncertainty of a passive system is being able to determine the risk associated with certain external events and how it relates to the designed passive safety systems. For example, external events have the potential to change assumed system boundary conditions which could result in the failure of the passive system to successfully perform its intended safety function.		One of the main conclusions of [https://nucleus.iaea.org/sites/smr/Lists/Publications/DispForm.aspx?ID=130 TECDOC 1487] [[References\| [42]]] is that “the development of an external event PRA in parallel with the early plant design may help to identify the vulnerabilities as well as potentially overly conservative design features at an early stage, leading to a well-balanced and cost-effective improvement in safety”. Therefore a core issue that needs to be clearly addressed moving forward is the balance between the cost and benefit of developing detailed External Events PRA models with insights that can be used to adequately and robustly screen external events that may otherwise be expected to be fully included (e.g., is such an approach feasible, justifiable; can a graded approach be provided that accounts for increased margin to safety goals with sufficient consideration of uncertainty and degree of confidence). In relation to the section describing passive system reliability, a large part of determining the uncertainty of a passive system is being able to determine the risk associated with certain external events and how it relates to the designed passive safety systems. For example, external events have the potential to change assumed system boundary conditions which could result in the failure of the passive system to successfully perform its intended safety function.

	The impacts of external hazards will likely provide a substantially greater fraction of the contribution to risk to the public than is the experience from the current fleet of LWRs. Because the current state of knowledge of potentially dominant very low frequency external hazards (phenomenology, event occurrence frequencies) is less developed than for internal events, the larger fractional contribution to overall risk will have a greater level of uncertainty ~~(in relation to the values of the risk metrics) than occur for the existing fleet of operating plants, which have a more mature understanding of their dominant risk contributors~~. This situation also may require modifications to processes and criteria that have been used for the existing fleet of ~~plant~~ to assess and screen external hazards from consideration as providing negligible contribution to PRA results. Some external events may be screened out through a deterministic and probabilistic process~~. External events that are screened out may not be commensurate with risk involved with specific reactor designs~~.		The impacts of external hazards will likely provide a substantially greater fraction of the contribution to risk to the public than is the experience from the current fleet of LWRs. Because the current state of knowledge of potentially dominant very low frequency external hazards (phenomenology, event occurrence frequencies) is less developed than for internal events, the larger fractional contribution to overall risk will have a greater level of uncertainty. This situation also may require modifications to processes and criteria that have been used for the existing fleet of plants to assess and screen external hazards from consideration as providing a negligible contribution to PRA results. Some external events may be screened out through a deterministic and probabilistic process.

	Roadmap actions supported for passive system reliability include:		Roadmap actions supported for passive system reliability include:

Admin: /* External Hazards */

2024-06-19T22:18:36Z

External Hazards

← Older revision		Revision as of 22:18, 19 June 2024
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	*Demonstrate Risk-Informed and Performance Based Approach		*Demonstrate Risk-Informed and Performance Based Approach

	A higher level of detail for these actions can be found in the ~~roadmap~~.		A higher level of detail for these actions can be found in the report.