External Hazards - Revision history

Admin: 1 revision imported

2025-01-24T18:23:31Z

1 revision imported

← Older revision	Revision as of 18:23, 24 January 2025
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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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	==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
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			__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.

Admin at 21:36, 12 June 2024

2024-06-12T21:36:00Z

← Older revision		Revision as of 21:36, 12 June 2024
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	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 roadmap.

	~~==EPRI Activities==~~

Admin: /* External Hazards */

2024-04-17T21:33:02Z

External Hazards

← Older revision		Revision as of 21:33, 17 April 2024
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	==External Hazards==		==External Hazards==
	One of the main conclusions of TECDOC 1487 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 (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.