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The HyRAM toolkit is the first-ever software toolkit that integrates deterministic and probabilistic models for quantifying accident scenarios, predicting physical effects, and characterizing hydrogen hazards’ impact on people and structures. HyRAM incorporates generic probabilities for equipment failures and probabilistic models for heat-flux impact on humans and structures, with computationally and experimentally validated models of hydrogen release and flame physics.

The initial modules can be used to quantify the likelihood and thermal consequences associated with gaseous hydrogen releases from user-defined hydrogen installations. Future development activities will integrate additional consequence models and develop user interfaces for additional audiences. When completed, the toolkit will enable industry-, SDOs (standards development organizations)-, and CDO (code development organizations)-led quantitative risk assessment and performance-based engineering with state-of-the-art, validated science and engineering models.


Developing hydrogen codes and standards is challenging because the relevant models and information span multiple science and engineering disciplines. The HyRAM toolkit integrates state-of-the-art models and data for assessing hydrogen safety. HyRAM provides a common platform for stakeholders conducting quantitative risk assessment and consequence analysis for hydrogen systems. The resulting information provides the scientific basis to ensure code requirements are consistent, logical, and defensible.

Fact Sheet


  • ƒƒGeneric data for gaseous hydrogen (GH2) systems:
    component leak frequencies, ignition probability; modifiable by users
  • Models of GH2 physical effects for consequence modeling
    • Release characteristics (plumes, accumulation)
    • Flame properties ( jet fires, deflagration within enclosures)
  • ƒƒProbabilistic models for human harm from thermal and overpressure hazards
  • ƒƒFast running: to accommodate rapid iteration
  • ƒƒCalculates common risk metrics for user-defined systems:
    FAR, AIR, PLL; frequency of fires
  • Ongoing development activities to add liquid hydrogen systems and features to add usability


  • ƒƒQRA and consequence calculations used to inform GH2 separation distances (NFPA 2, 2008)
  • QRA results used to inform indoor fueling requirements (NFPA 2, 2011)
  • Developed performance-based framework for establishing safety distances & mitigations (NFPA 2, 2016 and ISO TR-19880)
  • Ongoing activities: Liquid hydrogen separation distance (NPFA 2, 2019)
  • Future opportunities: Evacuation zone analysis, enclosure risk modeling

Sample Data



Risk Metric Value
PLL 7.362e-05
FAR 0.0168
AIR 3.362e-07
Scenario End State Type Avg. Events/Year
100pct Release No Ignition 0.0008
10pct Release No Ignition 0.0012
1pct Release No Ignition 0.0015
0.1pct Release No Ignition 0.0050
0.01pct Release No Ignition 0.0348

Sample HyRAM output: plots of jet flame temperature and heat flux for user-defined hydrogen releases; PLL, FAR, AIR, and frequency of unignited releases from a user-defined hydrogen installation

Questions Addressed

Given a user-defined system, risk analysts can use HyRAM to answer the following types of questions:

  • How would changes to system design affect overall risk?
  • Which design is the safest?
  • Will this enhance system safety? (If used with an economic model: is the increase in system cost justified?)
  • ƒƒWhat is the likelihood of a release from an installation?
  • How likely is it that a jet fire or deflagration would occur ?
  • What is the heat flux from a jet flame associated with a specific hydrogen release?
  • At what distance does heat flux reach the no-harm threshold?

About Sandia’s Hydrogen Program

Sandia’s Hydrogen Program supports the nation’s energy strategy —helping to diversify America’s energy sector and reduce our dependence on foreign oil through the advancement of hydrogen and fuel cell technologies. HyRAM is developed for the U. S. Department of Energy Fuel Cell Technologies Office by Sandia National Laboratories.

HyRAM documentation

Suggested citation for HyRAM 1.1: Katrina M. Groth, Ethan Hecht, John T. Reynolds, Myra L. Blaylock, Erin Carrier HyRAM (Hydrogen Risk Assessment Models), Version 1.1. Sandia National Laboratories, (2/28/2017); software available at http://hyram.sandia.gov

HyRAM 1.1 Technical Reference Manual. KM Groth, ES Hecht, JT Reynolds, ML Blaylock, EE Carrier. Methodology for assessing the safety of Hydrogen Systems: HyRAM 1.1 Technical Reference Manual. SAND2017-2998. March 2017

Katrina M. Groth, Ethan Hecht, John T. Reynolds, Myra L. Blaylock, Isaac W. Ekoto, and Gregory W. Walkup (2016). HyRAM (Hydrogen Risk Assessment Models), Version 1.0. Sandia National Laboratories, 2016; software available at http://hyram.sandia.gov

We also recommend including the full version number (e.g. HyRAM in your work. The version number can be found in HyRAM on Help/About HyRAM.

SNL analyses conducted with HyRAM

John T. Reynolds
HyRAM Lead Developer
(505) 284-2208
Chris LaFleur
Hydrogen Program Manager
(505) 844-5425

First published: January 2015. Last modified February 28, 2017.