Combustible Dust Testing

Laboratory testing to quantify dust explosion & reactivity hazards

Flammable Gas & Vapor Testing

Laboratory testing to quantify explosion hazards for vapor and gas mixtures

Chemical Reactivity Testing

Laboratory testing to quantify reactive chemical hazards, including the possibility of material incompatibility, instability, and runaway chemical reactions

DIERS Methodology

Design emergency pressure relief systems to mitigate the consequences of unwanted chemical reactivity and account for two-phase flow using the right tools and methods

Deflagrations (Dust/Vapor/Gas)

Properly size pressure relief vents to protect your processes from dust, vapor, and gas explosions

Effluent Handling

Pressure relief sizing is just the first step and it is critical to safety handle the effluent discharge from an overpressure event

Thermal Stability

Safe storage or processing requires an understanding of the possible hazards associated with sensitivity to variations in temperature

UN-DOT

Classification of hazardous materials subject to shipping and storage regulations

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Biological

Model transport of airborne virus aerosols to guide safe operations and ventilation upgrades

Radioactive

Model transport of contamination for source term and leak path factor analysis

Fire Analysis

Model transport of heat and smoke for fire analysis

Flammable or Toxic Gas

transport of flammable or toxic gas during a process upset

OSS consulting, adiabatic & reaction calorimetry and consulting

Onsite safety studies can help identify explosibility and chemical reaction hazards so that appropriate testing, simulations, or calculations are identified to support safe scale up

Mechanical, Piping, and Electrical

Engineering and testing to support safe plant operations and develop solutions to problems in heat transfer, fluid flow, electric power systems

Battery Safety

Testing to support safe design of batteries and electrical power backup facilities particularly to satisfy UL9540a ed.4

Hydrogen Safety

Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen

Spent Fuel

Safety analysis for packaging, transport, and storage of spent nuclear fuel

Decommissioning, Decontamination and Remediation (DD&R)

Safety analysis to underpin decommissioning process at facilities which have produced or used radioactive nuclear materials

Laboratory Testing & Software Capabilities

Bespoke testing and modeling services to validate analysis of DD&R processes

Nuclear Overview

Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant.

Severe Accident Analysis and Risk Assessment

Expert analysis of possible risk and consequences from nuclear plant accidents

Thermal Hydraulics

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Environmental Qualification (EQ) and Equipment Survivability (ES)

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Laboratory Testing & Software Capabilities

Testing and modeling services to support resolution of emergent safety issues at a power plant

Adiabatic safety calorimeters (ARSST and VSP2)

Low thermal inertial adiabatic calorimeters specially designed to provide directly scalable data that are critical to safe process design

Other Lab Equipment (DSC/ARC supplies, CPA, C80, Super Stirrer)

Products and equipment for the process safety or process development laboratory

FERST

Software for emergency relief system design to ensure safe processing of reactive chemicals, including consideration of two-phase flow and runaway chemical reactions

FATE

Facility modeling software mechanistically tracks transport of heat, gasses, vapors, and aerosols for safety analysis of multi-room facilities

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Recent Posts

Producing Statistical Analysis Regarding Severe Accident Uncertainty at Nuclear Power Plants

Posted by Nick Karancevic on 05.15.19

By Nick Karancevic, Senior Nuclear Engineer, Fauske & Associates, LLC

The Three Mile Island Severe Accident occurred in 1979, near Harrisburg, Pennsylvania. In 1986, the Chernobyl Criticality Accident occurred.  In 1986, what is widely considered as the worst commercial power reactor accident occurred at Chernobyl Power Station. In 1988, the US Nuclear Regulatory Commission issued Generic Letter 88-20,
MAAP5 Primary System Nodalization Scheme
MAAP5 Primary System Nodalization Scheme

"Individual Plant Examination for Severe Accident Vulnerabilities". These events prompted a development of computer codes that could accurately simulate Severe Accidents, such as Three Mile Island, for accident management evaluations and prompted the development of Severe Accident Management Guidelines (SAMG). But, what kind of computing power was available back then? This would in part guide the future definition of “accurate simulation”. And more relevant, what kind of computing power is available now?

I can recall vividly when one of my friends stated there would soon be a 1000 MHz CPU available. We were all in disbelief and shock. The year was 2000, and such things were unheard of. Fast forward to the year 2018, and I find myself writing a business case to purchase a single server that will sit on somebody’s desk, with 112 CPU cores which in the grand scheme of things is really not that many CPUs compared to the power harnessed at the United States national laboratories.

A 2003 European Commission study noted that “core damage frequencies of 5 × 10-5 [per reactor-year] are a common result” or in other words, one severe accident would be expected every 20,000 reactor years. From this value, assuming there are 500 reactors in use in the world, one core damage incident would be expected to occur every 40 years. Ominously, the Fukushima Daiichi nuclear disaster occurred in the year 2011.

After the Fukushima Severe Accident, it was now time to revisit the severe accident nuclear codes. A lot of research and wisdom has resulted from the Three Mile Island accident; however, a lot more remained unknown. For example, what are the specific combinations of criteria needed for the nuclear fuel pins to fail? Now that we have more computing speed available, can we run a more detailed simulation, with more nodes, and more physics models, and still expect an answer overnight, if not a few hours. 

Most importantly, we may never know the exact criteria for nuclear fuel pin failure, or the best correlation of the two excellent candidates that should be used for some key phenomena. We may be able to tame the numerical uncertainty of complex engineering calculations, but we will never fully mitigate it with one hundred percent certainty. For these reasons, the solution stands out: why not simulate the same accident scenario using all of the available state of the art correlations, and a representative range of key parameters to get the best possible scenario? Statistical sampling and analysis tools can help the severe accident analyst to say, “not only is the best case autoignition temperature testingsimulation showing this result, but an uncertainty and sensitivity analysis shows the same”. In the year 2009, the NRC issued NUREG-1855, Volume 1, “Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision Making”. Why not run a sensitivity and uncertainty analysis to determine how much time a nuclear reactor operator has to complete some action that will prevent core damage? I cannot envision a world where uncertainty and sensitivity analysis don’t become mainstream requirements of nuclear analysis, complementing other data analytics of today. 

There is much to share on sensitivity and uncertainty analysis for Severe Accident mitigation. Continue to see content like this by subscribing our blog below.

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Topics: severe accident, MAAP, nuclear

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