Addressing flood risks in light of the Fukushima disaster: near-term advice for nuclear plants
/EINPresswire.com/ Among the first U.S. regulatory moves to come out of Japan's Fukushima Daiichi accident, the Nuclear Regulatory Commission (NRC) is now requiring all operating reactor licensees under 10 CFR Part 50 to complete new, updated flooding analyses.
Times have changed - and science has evolved since many of the nation's reactors were constructed. New regulations require nuclear energy facilities to assess their risk profile based on present-day methods and current site and upland characteristics, and compare that new analysis to design basis. The NRC estimates this will take 1,300 man hours, though that time may vary widely between plants.
Modeling efforts must start with the most conservative assumptions, and evaluate a number of potential risks, from extreme precipitation and river flooding due to snow melt to a catastrophic failure of upstream dams, to tsunamis, storm surges or seismic and flood events that divert a river. Depending on the results, operators may also need to evaluate protection for safety equipment and controls, and develop an integrated assessment that could take as long as 2,700 man hours to complete. New counter measures, as simple as higher door sills or as complex as relocating equipment out of harm's way, could also be required.
To prepare, engineers at Alden suggest facility managers answer three critical questions as soon as possible:
First Step: What's our timeframe?
Determine where each reactor is likely to sit on the NRC priority list, slated to be released this month. River plants are likely to be prioritized over those on the coast or on lakes. If flooding has been a recent concern, as it has along the Missouri River, expect to be on top of the list. It's important to take time to understand the likely risks of each individual site. For example, East Coast plants are likely not vulnerable to tsunamis but could face hurricane storm surges.
Second Step: What needs to be done?
Review NUREG-0800 and NUREG/CR-7046 to become familiar with the requirements. Per NUREG-0800 and CR-7046, many sites are likely to require sophisticated multi-dimensional modeling, including sediment transport simulations. All studies must be based on current topography and river bathymetry (where applicable), and that means if recent bathymetric data is not available, a data collection effort will be required. Model validation data will also be required. It's suggested that this data be collected during periods of high flow, making it critical to plan ahead because of the limited window of time in which that data will be available. To characterize risks and hazards and provide accurate modeling data, a site "walkdown" should include the actual location of essential equipment as well as site characteristics or changes that impact water running onto or off the site and the influence of nearby rivers, lakes and coastal areas. It may also be important for the modeling team to view the entire model domain including areas outside of the plant boundary.
Third Step: What resources will you need?
NUREG-0800/CR-7046 requires that 10CFR Part 50 Appendix B QA requirements are met. Flood modeling as required by the NRC is a highly specialized area, and one that many plants are not equipped to complete in-house. Plants that wish to contract out to meet the requirements will want to begin interviewing vendors and reserving space on their preferred vendor's calendar soon. While many civil/AE firms perform flood plain studies, few have an Appendix B program - so a resource crunch is widely anticipated. What's more, licensees must respond to the NRC with a site-specific procedure and schedule for walkdowns within 180 days of NRC approval of the response approach now being developed by the Nuclear Energy Institute. The walkdowns will require training for all participants. In-house or contracted flood plain and sedimentation experts must be involved early and should participate in the walkdowns to effectively gather the data they will need to complete accurate and thorough flooding simulations.
As the first few plants go through the process of addressing these new requirements, the industry as a whole can expect a learning curve. Smart plant operators will get a head start on planning now, and modify their approach as necessary based on the experiences of those facilities that complete their assessments early on.
About Alden
Alden (Alden Research Laboratory, Inc.) is an internationally acclaimed leader in the hydraulic modeling of extreme events. For more than 115 years, the company has provided engineering, field and laboratory solutions to the power and water industries related to flood stage prediction, flood control structures and sediment and debris transport modeling. On its 32-acre campus in Holden, Massachusetts and its offices in Fort Collins, Colorado, Alden applies its expertise in solving flow problems to a broad range of applications including hydraulic modeling, environmental engineering, gas flow systems modeling, flow meter calibration, and field services. Founded in 1894, Alden is the longest continuously operating hydraulic laboratory in the United States. Learn more at www.aldenlab.com.
CONTACT: David Schowalter, Ph.D
(508) 829-6000 ext. 6476 dschowalter@aldenlab.com
Times have changed - and science has evolved since many of the nation's reactors were constructed. New regulations require nuclear energy facilities to assess their risk profile based on present-day methods and current site and upland characteristics, and compare that new analysis to design basis. The NRC estimates this will take 1,300 man hours, though that time may vary widely between plants.
Modeling efforts must start with the most conservative assumptions, and evaluate a number of potential risks, from extreme precipitation and river flooding due to snow melt to a catastrophic failure of upstream dams, to tsunamis, storm surges or seismic and flood events that divert a river. Depending on the results, operators may also need to evaluate protection for safety equipment and controls, and develop an integrated assessment that could take as long as 2,700 man hours to complete. New counter measures, as simple as higher door sills or as complex as relocating equipment out of harm's way, could also be required.
To prepare, engineers at Alden suggest facility managers answer three critical questions as soon as possible:
First Step: What's our timeframe?
Determine where each reactor is likely to sit on the NRC priority list, slated to be released this month. River plants are likely to be prioritized over those on the coast or on lakes. If flooding has been a recent concern, as it has along the Missouri River, expect to be on top of the list. It's important to take time to understand the likely risks of each individual site. For example, East Coast plants are likely not vulnerable to tsunamis but could face hurricane storm surges.
Second Step: What needs to be done?
Review NUREG-0800 and NUREG/CR-7046 to become familiar with the requirements. Per NUREG-0800 and CR-7046, many sites are likely to require sophisticated multi-dimensional modeling, including sediment transport simulations. All studies must be based on current topography and river bathymetry (where applicable), and that means if recent bathymetric data is not available, a data collection effort will be required. Model validation data will also be required. It's suggested that this data be collected during periods of high flow, making it critical to plan ahead because of the limited window of time in which that data will be available. To characterize risks and hazards and provide accurate modeling data, a site "walkdown" should include the actual location of essential equipment as well as site characteristics or changes that impact water running onto or off the site and the influence of nearby rivers, lakes and coastal areas. It may also be important for the modeling team to view the entire model domain including areas outside of the plant boundary.
Third Step: What resources will you need?
NUREG-0800/CR-7046 requires that 10CFR Part 50 Appendix B QA requirements are met. Flood modeling as required by the NRC is a highly specialized area, and one that many plants are not equipped to complete in-house. Plants that wish to contract out to meet the requirements will want to begin interviewing vendors and reserving space on their preferred vendor's calendar soon. While many civil/AE firms perform flood plain studies, few have an Appendix B program - so a resource crunch is widely anticipated. What's more, licensees must respond to the NRC with a site-specific procedure and schedule for walkdowns within 180 days of NRC approval of the response approach now being developed by the Nuclear Energy Institute. The walkdowns will require training for all participants. In-house or contracted flood plain and sedimentation experts must be involved early and should participate in the walkdowns to effectively gather the data they will need to complete accurate and thorough flooding simulations.
As the first few plants go through the process of addressing these new requirements, the industry as a whole can expect a learning curve. Smart plant operators will get a head start on planning now, and modify their approach as necessary based on the experiences of those facilities that complete their assessments early on.
About Alden
Alden (Alden Research Laboratory, Inc.) is an internationally acclaimed leader in the hydraulic modeling of extreme events. For more than 115 years, the company has provided engineering, field and laboratory solutions to the power and water industries related to flood stage prediction, flood control structures and sediment and debris transport modeling. On its 32-acre campus in Holden, Massachusetts and its offices in Fort Collins, Colorado, Alden applies its expertise in solving flow problems to a broad range of applications including hydraulic modeling, environmental engineering, gas flow systems modeling, flow meter calibration, and field services. Founded in 1894, Alden is the longest continuously operating hydraulic laboratory in the United States. Learn more at www.aldenlab.com.
CONTACT: David Schowalter, Ph.D
(508) 829-6000 ext. 6476 dschowalter@aldenlab.com
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