Leslie Dewan on CNN's Global Public Square: Waste Annihilating Molten Salt Reactor (WAMSR)

USNRC and EPRI Announce New Seismic Source Characterization Model for NPPs

The US Nuclear Regulatory Commission (USNRC), together with the Electric Power Research Institute(EPRI) and the US Department of Energy (USDOE) today released details of a new model for calculating the seismic risk for Nuclear Power Plants (NPPs) in the Central & Eastern United States (C & E US). This replaces the EPRI Report NP-4276 Seismic Hazard Methodology for the Central and Eastern United States of July 1986; and the Lawrence Livermore National Laboratory Model, Seismic Hazard Characterization of 69 Nuclear Plant Sites East of the Rocky Mountains, (Bernreuter, D.L., et al., 1989, NUREG/CR-5250, Volumes 1–8), and is the result of a 4-year long joint EPRI-USNRC project to revise the ground motion estimates that can be expected at a given NPP location in the C&E US.

Speaking broadly, the new model results in a greater ground motion for a given NPP location, and the greatest increases in ground motion estimates have been obtained for nuclear power plants in the vicinity of the New Madrid (TN) and Charleston (SC) fault systems, based on a 7-plant sample selected for detailed study by the USNRC. The new, higher ground motion estimates do not by themselves translate to a higher nuclear safety risk for NPPs at those locations - each NPP must re- calculate its safety risk based on details of its own design and plant layout, relative to the enhanced ground motion risk it faces.

The USNRC is asking the NPPs it regulates to re-evaluate their seismic risk based on this new model, and the model will also be used in assessing the seismic risk for new nuclear plants in the region during the new licensing process. While the new seismic and ground motion risk estimates have been in development for the last several years, the Commission direction in this regard is also part of regulatory initiatives in response to the events at the Fukushima nuclear power plant following the Tohoku earthquake and tsunami-following, on 11 March 2011.

World Economic Forum Global Risks Report 2012

The World Economic Forum Annual Meeting begins in Davos-Klosters, Switzerland, tomorrow, January 25 2012. In advance of the meeting, the Forum has published its 7th Annual Global Risks Report, created with its partners - Marsh & McLennan, Swiss Re, the Wharton Center for Risk Management, and Zurich Financial Services.

A most interesting read, the report develops 5 major global risk categories – Economic, Environmental, Geopolitical, Societal and Technological, and reports results of a broad survey of risk perceptions among representatives from 5 broad categories of Stakeholder Groups – Business, Academia, NGO, Government, and International Organization. Within the 5 risk categories are a total of 50 risk scenarios, roughly 10 in each risk category, each differing in likelihood and impact – e.g., in the Economic risk category: Chronic Fiscal Imbalances is considered to have the highest likelihood-impact combination; while Major Financial Systemic Failure is considered less likely, but considered to have the highest impact. Unmanageable Inflation or Deflation is considered least likely, while Unforeseen Negative Consequences of Regulations is considered to have the least impact.

The report proceeds to define, in each of the 5 Risk Categories, a Center of Gravity (CoG) – as the risk scenario with the highest (judgment-weighted) combination of likelihood and impact. Thus, the Economic Risk CoG is Chronic Fiscal Imbalances, while the Environmental, Geopolitical, Societal and Technological CoGs are respectively Rising Greenhouse Gas Emissions, Global Governance Failure, Unsustainable Population Growth and Critical Infrastructural Systems Failure. The survey also included a feature where respondents could write in ‘X-factors’ – risk scenarios that had unknown likelihood and impact, but which were nevertheless felt important enough to be thought about. This resulted in risk scenarios such as Volcanic Winter, Mega-accidents, and Neotribalism.

The report develops a series of risk constellations, where the cascading effect of different consequential risk scenarios across the 5 categories is explored. Three major cases are examined – a socio-economic dystopia, a governance dystopia and a technological dystopia, in each case setting out the different combinations of the 50 risk scenarios which could lead to each. The concept of 'critical connectors' is elucidated as the set of risk scenarios which link to the CoG of more than one risk category. Four critical connectors, all of them Economic risk scenarios, link 3 or more of the 5 CoGs.

Finally, the report presents detailed data and analyses of the Survey itself, and I found the data on the differential risk perceptions across the 5 Stakeholder groups, as well as across geographic affiliations particularly interesting. For example, on geographic variation, Europeans rank Chronic Fiscal Imbalances more likely than Middle Easterners and North Africans; while Asians see Unmanageable Inflation or Deflation as more likely than either Europeans or North Americans. Across stakeholder classes, Business saw the likelihood of Negative Consequences of Regulation as being higher than did Academia, while NGOs saw Negative Consequences of Nanotechnology as being more likely than did Academia.

Even more interestingly, subject matter experts (across the 5 stakeholder classes) ranked the likelihood of the scenarios within their area of expertise (among the 50 risk scenarios) higher than generalists across the board (with the exception of nanotechnology, where generalists ranked the likelihood of unforeseen negative consequences higher than subject matter experts). This is very interesting, in that, on macroeconomic, socio-economic or environmental issues, where the risk is more easily grasped by generalists, the general level of concern appears lower than might be warranted, while on 'esoteric' technological issues,which by their nature are harder to properly grasp, the general level of concern appears higher than might be warranted strictly on an existing-knowledge basis.

I have sketched here a rather broad summary of the report, but it is well worth a detailed read. In addition to the themes I have outlined, the report also contains a Special Section on the Great East Japan Earthquake of 11 March 2011 (the Tohoku quake). In the video clip below, David Cole, Chief Risk Officer at Swiss Re, talks about the WEF's Global Risk Report 2012. He points out that risk assessments conducted by governments and companies in the past have been inadequate, subjecting nations to extreme economic risks. He urges that a Country Risk Officer be appointed for each country, who would aggregate and prioritize different kinds of risks, and bring them to the attention of policymakers.

In another clip within the same playlist, Axel Lehmann, Chief Risk Officer of Zurich Financial Services emphasizes that no single individual, company, or even government can fully appreciate all aspects of the risks involved, and urges, on as many levels as possible, the formation of public-private partnerships for risk identification, analysis and mitigation. Erwann Michel-Kerjan, Director of the Wharton Risk Management Center, in another clip, points out that for high level decision makers, it is necessary to become familiar with all kinds of risks, not only the ones that their training or background predisposes them to consider. He emphasized also that the other side of risk is always opportunity, and the winners are those who not only protect themselves from the negative consequences of risk events, but those who positively profit from them :

Next Steps in Seismic Hazard / Earthquake Loss Assessment Models

Just as the events at the Fukushima nuclear plant following the Tohoku earthquake of 11 March 2011 pointed to new directions in nuclear plant safety assessment (see my earlier blogpost), so also the property/casualty losses following the quake point to logical next steps in earthquake CAT loss models.

The recent Swiss Re Report on Lessons from Recent Major Earthquakes highlighted a number of ways that CAT Models could improve their loss estimates for portfolios insured against earthquakes. Emphasizing first of all that 2011 set the record both for total economic losses from earthquakes ($ 226 B) and for insured claims ($ 47 B), it underlined that the Tohoku earthquake of 11 March 2011, with insured claims of $35 B, was the most expensive natural CAT of all time, not just among earthquakes, but all natural CATs.

Next, the report turned to perceived inadequacies in current generation CAT loss estimation models. The Swiss Re report pointed out that while most CAT models used by property/casualty underwriters appeared to have adequately modeled property losses following from ground shaking alone, they typically underestimated (if they modeled them at all) the losses resulting from secondary loss agents – (i) the tsunami(s) following, (ii) the seismic aftershocks, (iii) soil liquefaction (iv) business interruption (BI) and (v) contingent business interruption (CBI). Losses due to fires following earthquakes, another secondary loss agent, however, appear to be well modeled.

Tsunamis Where CAT modelers had considered tsunamis following quakes, the height, consequent inland penetration, and damaging force of the tsunami were underestimated. This was true both in the Tohoku quake in Japan, as well as with the recent earthquakes in Chile.

Seismic Aftershocks A major seismic event is often followed by aftershocks for a considerable period afterward. In some cases, a single aftershock can be more damaging than the original event; and very often the cumulative impact of the aftershocks is greater than that of the original event. Such cumulative effects and the clustering of smaller magnitude events following the original quake are important contributions to total losses, and need to be modeled more carefully.

Soil Liquefaction This is a phenomenon where, after an earthquake, the soil loses its normal resistance to plastic deformation, and begins to flow like a fluid with a temporal and spatially variable viscosity. This was observed both in the aftermath of the Tohoku quake and in the recent Christchurch quakes in New Zealand, although in the Tohoku quake the tsunami damage far overwhelmed damage from soil liquefaction. As a secondary loss agent, soil liquefaction impacts total property replacement costs in the following ways: by damage from subterranean flooding, costs of land restoration, and in the case of large structures, damage from differential settlement (caused by spatial viscosity variations in the liquefied soil). In geospatial modeling of soil liquefaction potential, important factors to consider include the existence of a shallow ground water table; properties built on reclaimed land, near a river bank, or on poorly consolidated sandy soils that are most prone to liquefaction. Many of these risk factors are easily satisfied in urban areas where large commercial properties are usually built.

Business Interruption (BI) losses are usually underestimated by models, because they underestimate the time period over which production facilities could remain damaged; and Contingent Business Interruption (CBI) losses are usually underestimated by models because they capture insufficiently well supply chain dependencies, location, and geographic factors.

These considerations point to logical next steps for Earthquake CAT loss estimation model developers to undertake as improvements in their models. While the Tohoku earthquake and the tsunami that followed was the most devastating CAT in history, it is worth remarking that, from the modelers' perspective, it was also geophysically the most well-recorded CAT of all time. Following the devastating Kobe quake of 1995, a large, dense, high-bandwidth, high-connectivity and high-sensitivity network of ground motion sensors was set up. This network spanned the area which was impacted by the Tohoku quake and tsunami, both on the ground and in the ocean, thus generating significant amount of data relative to the spatial distribution and magnitude of ground shaking intensity following the quake,both above ground as well as on the ocean-bed. In addition, following the Sumatra-Andaman earthquake-tsunami of 2004, a network of tsunami sensors and deep-water pressure gauges was also set up. The result is that a rich dataset is now available, which modelers can use to calibrate their ground motion loss estimate modules, and the correlation between earthquake moment magnitude with the size of the tsunami it can generate. However, on a larger scale, the lesson of the Tohoku tsunami quake is likely still to be that the historical record of tsunamis following earthquakes is as yet too sparse to enable confidence about the correlation between seismic moment magnitude and the temporal return periods. Nevertheless, CAT modelers can still proceed to remove the underestimation bias in the loss potential from secondary loss agents that was seen following recent earthquakes.

USDOE Issues Funding Opportunity Announcement for SMRs

The US Department of Energy (USDOE) issued a draft Funding Opportunity Announcement (FOA) this week, intended to support activities related to the design and licensing of Small Modular Reactors (SMRs), defined as reactors with an electric output of 300MWe or less; which can be manufactured remotely, transported to point of construction, with on-site assembly largely limited to system integration of components for operation.

Importantly, the USDOE is interested in designs with passive safety (e.g., against consequences of a nuclear accident) as well as inherent safety (e.g., against natural catastrophes such as earthquakes, windstorms or floods), in addition to designs with long inter-refueling periods, low capital cost outlays, low maintenance and operating costs, and high proliferation resistance. The stated intention is to support up to 2 reactor designs through the USNRC design and licensing process, with the ability to be deployed ‘expeditiously’ being an important merit criterion. 2022, a decade from now, is the target year for commercial operation.

Proponents may choose to pursue licensing from the USNRC under either 10 CFR 50 or 10 CFR 52. Stakeholders are encouraged to form consortia, and proponents are encouraged to form design-centered working groups (DCWGs) across the supply and value chains e.g., SMR manufacturers, power utilities, local bodies; and the activities funded by USDOE are required to draw at least 50% of their total resources required, from internal sources. The total amount of funding available from USDOE is estimated to be $452 M, subject to Congressional appropriations. The current draft FOA will be issued in final form after feedback from, and consultation with, stakeholders.

NRC Seeks Prompt Action on Fukushima Near-Term Task Force Recommendations

The US Nuclear Regulatory Commission today directed its staff to complete several actions over the next 45 days in response to the 12 recommendations of its Near-Term Task Force on the Fukushima Nuclear Accident, which submitted its report on July 12.

The Commission has asked the staff to produce a paper by September 9, outlining which of the recommendations 2-12 (recommendation 1 was that the entire regulatory framework be holistically reviewed) should be implemented immediately, including a public dialogue on the process, the schedule for which will be announced soon. It has also asked the staff to produce, by October 3, another paper prioritizing recommendations 2-12, explaining the rationale, and also engaging both the public and other stakeholders. Over the next 18 months, the staff will consider recommendation 1, to review the entire regulatory framework, balancing risk -informed regulation, and defence-in-depth considerations.

Gaps in Current Probabilistic Risk Analysis (PRA) Methodology

Probabilistic Safety Analysis (PSA) of nuclear reactors (in the IAEA's usage), or Probabilistic Risk Analysis (PRA) in the USNRC's usage, is a technology that is being continually refined, both in response to those of its existing inadequacies that are already known to the original analysts and reviewers, and also in response to events that specifically underline one or more of such gaps. The Fukushima nuclear disaster, for example, increased the perceived urgency of addressing major gaps in nuclear reactor safety analyses and PSA/PRA techniques.

The USNRC was recently briefed on Severe Accidents and Options for Proceeding with Level 3 Probabilistic Risk Analysis (PRA Level 3). Meeting Agenda, Slides presented by Biff Bradley from the Nuclear Energy Institute (NEI) , Stewart Lewis of the Electric Power Research Institute (EPRI), Karl N. Fleming (of KNF Consulting), and NRC Staff. Meeting Transcript.

The two main gaps as seen by the US NRC Staff include:

Modeling of Consequential Linked Events
Current PSA techniques have not focused on risk implications of event sequences where a consequent initiating event occurs while a plant is responding to the first. PSA/PRA methodologies traditionally have not considered the risk implications of initiating events leading to accidents at multiple units at the same site - such as the near-simultaneous swamping by the tsunami of diesel generating systems supplying emergency power to several different nuclear reactors, each of which then suffered core damage as a consequence.

Aqueous Dispersion of Radionuclides
The risk implications of a containment breach have traditionally been considered in PRA Level 3, but the focus has been on atmospheric dispersion. Fukushima showed that the possibility of aqueous dispersion of radionuclides, must also be studied and modeled, both from spent reactor fuel pools and from the reactor core itself. The water in the sprays used to cool the spent fuel pools and the core, as emergency measures in severe accident mitigation, resulted in both internal and external floods, and the radiological consequences of radionuclide dispersal through such events deserve to be better understood.

NRC Briefing: Severe Accidents and Level 3 PRA

The staff of the US Nuclear Regulatory Commission today held a briefing for the Commissioners on Severe Accidents, and Options for proceeding with Probabilistic Risk Asessment - Level 3 (PRA Level 3).

Traditionally, PRA/PSA Level 3 has not been a strong regulatory requirement because the results of Level 1 (usually the core damage frequency, CDF) and the results of Level 2 (large early release fraction/frequency, LERF) can be used as surrogate proxies for the types of Risk Metrics that a Level 3 PSA/PRA might generate, which could include the following: the number of early fatalities; the number of early injuries, the number of latent cancer fatalities, or the total population dose at different locations; as well as the individual early and latent fatality risk, and the economic cost of mitigation actions taken following a severe accident. The CDF, for example, can proxy for the latent cancer risk, while the LERF could proxy for the prompt fatality risk.

However, a number of potential benefits are foreseen for a full PRA Level 3 analysis, including feedback into risk-informed regulatory guidance for new reactors and use of risk insights in forthcoming SMR design reviews. In addition, capabilities such as modeling of radionuclide aqueous dispersion modes, and multi-unit risk assessment could also be addressed. The modeling of radionuclide dispersal in the event of a severe accident which is initiated by an external event such as an earthquake, tsunami or hurricane also calls for additional modeling efforts, since meteorological variables such as windspeed & direction, ambient precipitation and humidity may not correspond to what is normally expected for that site at that time of year (for example).

NRC Staff plan to use an existing SPAR (Standardized Plant Assessment Risk) model as the basis for proceeding to PSA Level 3. The SPAR model is essentially a plant-specific PSA/PRA Level 1 designed to incorporate both external and internal initiating events, recent modifications of which include capabilities to yield LERFs. Since external hazards are site-specific, much greater value can be expected to be derived if the SPAR model selected for development to PRA Level 3 is for a NPP site that is either representative of the entire population of NPPs, or, has a larger than average number and type of external hazards.

NRC Releases Near-term Report of Fukushima Task Force

The United States Nuclear Regulatory Commission has released the Near-Term Task Force Review of Insights from the Fukushima Da-ichi Accident: Recommendations for Enhancing Reactor Safety in the 21st Century.

The report has 12 recommendations, which I cite here in full, verbatim.

Clarifying the Regulatory Framework
1. The Task Force recommends establishing a logical, systematic, and coherent regulatory framework for adequate protection that appropriately balances defense-in-depth and risk considerations.
Ensuring Protection
2. The Task Force recommends that the NRC require licensees to reevaluate and upgrade as necessary the design-basis seismic and flooding protection of structures, systems, and components for each operating reactor.
3. The Task Force recommends, as part of the longer term review, that the NRC evaluate potential enhancements to the capability to prevent or mitigate seismically induced fires and floods.
Enhancing Mitigation
4. The Task Force recommends that the NRC strengthen station blackout mitigation capability at all operating and new reactors for design-basis and beyond-design-basis external events.
5. The Task Force recommends requiring reliable hardened vent designs in boiling water reactor facilities with Mark I and Mark II containments. (Section 4.2.2)
6. The Task Force recommends, as part of the longer term review, that the NRC identify insights about hydrogen control and mitigation inside containment or in other buildings as additional information is revealed through further study of the Fukushima Dai-ichi accident.
7. The Task Force recommends enhancing spent fuel pool makeup capability and instrumentation for the spent fuel pool.
8. The Task Force recommends strengthening and integrating onsite emergency response capabilities such as emergency operating procedures, severe accident management guidelines, and extensive damage mitigation guidelines .
Strengthening Emergency Preparedness
9. The Task Force recommends that the NRC require that facility emergency plans address prolonged station blackout and multiunit events.
10. The Task Force recommends, as part of the longer term review, that the NRC pursue additional emergency preparedness topics related to multiunit events and prolonged station blackout.
11. The Task Force recommends, as part of the longer term review, that the NRC should pursue emergency preparedness topics related to decisionmaking, radiation monitoring, and public education.
Improving the Efficiency of NRC Programs
12. The Task Force recommends that the NRC strengthen regulatory oversight of licensee safety performance (i.e., the Reactor Oversight Process) by focusing more attention on defense-in-depth requirements consistent with the recommended defense-in-depth framework.