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

Blog

Our highly experienced team keeps you up-to-date on the latest process safety developments.

Process Safety Newsletter

Stay informed with our quarterly Process Safety Newsletters sharing topical articles and practical advice.

Resources

With over 40 years of industry expertise, we have a wealth of process safety knowledge to share.

Recent Posts

MAAP5 Analysis of Various Injection Strategies during Extended Loss of AC Power

Posted by The Fauske Team on 05.17.17

Fauske & Associates, LLC (FAI) is deeply involved in the analysis of severe accidents and the development of severe accident computational models. FAI uses the Modular Accident Analysis Program (MAAP) software that is owned and licensed by the Electric Power Research Institute (EPRI). MAAP is utilized by nuclear utilities worldwide to analyze abnormal plant transients and severe accidents, such as station blackouts (SBO) or loss of coolant accidents (LOCA), and to guide development of severe accident management guidelines (SAMGs). Severe accident management consists of mitigation actions before and after core damage has occurred.

During shutdown conditions, the severe accident progression is not very sensitive to the initial water level in the vessel except with regard to the time of core uncovery and core damage. However, the thermal hydraulic conditions in the primary system, steam generators, and containment can affect the SAMG actions and progression of the accident. If mobile equipment is unavailable for an extended loss of AC power (ELAP) during shutdown conditions with an open RCS (pressurizer or steam generator manways are open), establishment of gravity injection from the refueling water storage tank (RWST) or condensate storage tank (CST) into the RCS can be an important operator action.

An example analysis of gravity injection during an extended loss of AC power (ELAP) is shown for how MAAP5 was used for shutdown SAMG development. Three sample MAAP runs were performed for a typical Westinghouse type four loop plant:

  1. One 5” gravity injection line without any containment heat removal and without containment vent
  2. One 5” gravity injection line with containment vent (8” vent line opened at 1.22 bar (3 psig) and left open)
  3. Two 5” gravity injection lines with containment vent

The runs were stopped when the core exit temperature exceeded 1200 °F. An analysis of the results is provided in the following paragraph.

After the loss of residual heat removal (RHR) cooling, the core temperature reaches the saturation temperature soon and boiling occurs in the core. The boiling in the core pushes two-phase water into the hot leg and the pressurizer. As a result, the water level in the pressurizer increases as shown in Figure 1(a). Without the containment vent, the gravity injection soon stops because of the high containment pressure and high water level in the pressurizer. With the containment vent available, the high pressurizer level and up to 3 psig of containment back pressure shuts off the gravity injection from time to time resulting in core uncovery in both cases with one and two injection lines. Figure 1(b) shows the mixture water level in the core. When the injection flow stops, the core was uncovered and the mixture level decreases enough to reduce the steaming rate and the two-phase carry-over to the pressurizer.

In most conditions, the pressurizer surge line is flooded and water drainage from the pressurizer to the hot leg is prevented. However, the pressurizer level decreases from time to time due to counter-current water drainage when the core is uncovered. Figure 1(c) shows the containment pressure. Without the containment vent, high containment pressure prevents gravity injection. For the other two cases, an 8” containment vent line was opened at 3 psig and remained open throughout the remainder of the sequence. Figure 1(d) shows the hottest core node temperature. The number of lines used for gravity injection makes some difference in the pressurizer water level and timing of core uncovery. However, the general responses between two cases are similar. For the case with two injection lines, the run is stopped because the core exit temperature exceeded 1200 F.

The success of gravity injection during an ELAP with the pressurizer manway open depends on several plant specific factors:

  1. Elevation difference between the RWST and RCS and the water level in the RWST
  2. Availability of external RWST makeup
  3. Containment vent (or containment heat removal) available or not
  4. Number of injection lines, size, and the discharge coefficient of the piping
  5. Decay heat

containment-vent-injection-line

In the samples above, MAAP5 was used to predict the primary system and containment response to gravity injection during an ELAP with and without containment venting and at various injection flow rates. Analysis can also be done to determine timings of events such as timing of core uncovery and time to vent the containment for various scenarios such as:

  1. Accidents initiated during shutdown conditions when the RCS is closed and SG injection is available to 1 steam
    generator
  2. Gravity injection from the RWST during an ELAP (as demonstrated here)
  3. External injection using a fire pump for a case when the gravity injection has failed, and more


The insights from plant specific MAAP5 calculations similar to the sample calculations can be used to guide SAMG development.

Topics: archived

cta-bg.jpg

Is My Dust Combustible?

A Flowchart To Help You Decide
Download Now