Severity
Incident
Leak
Uncertain
Ignition
No

A liquid hydrogen neutron moderator developed a leak between the canister that contains liquid hydrogen and the insulating vacuum jacket.

The moderator assembly consists of an exterior metal vacuum jacket with an interior metal transfer line and canister that contain liquid hydrogen. The moderator canister is constructed of aluminum and is approximately five inches wide, five inches high, and two inches deep. The liquid hydrogen supply lines to the moderator canister are constructed of stainless steel. The operating temperature of the moderator varies from -420 degrees Fahrenheit to a possible 300 degrees Fahrenheit. Mechanical operators discovered a leak following a cleaning operation on the moderator. The cleaning operation was performed to remove impurities that could freeze and reduce flow in the transfer line. Since the moderator is constrained and not readily accessible by personnel, inspections could not be performed to determine the exact location or cause of the leak.

Possible causes for the leak were:

Material failure from the cycling of the unit between the working temperature of -420 degrees Fahrenheit to 300 degrees Fahrenheit.
Changes in material caused by possible overheating of the unit. The existing moderator did not have a thermocouple so that temperatures could be monitored and operations modified, if necessary.
Over-pressurization of the unit from possible overheating.

Incident Date
Sep 14, 1995
Setting
Equipment
  • Hydrogen Storage Equipment
  • Vessel
Damage and Injuries
Probable Cause
Contributing Factors
Characteristics
When Incident Discovered
Lessons Learned

Designs for high-tech systems/components evolve based on operating experience. The design changes should resolve identified deficiencies and are part of a continuous improvement process to increase reliability and productivity.

Key:

  • = No Ignition
  • = Explosion
  • = Fire
Hydrogen Incident Summaries by Equipment and Primary Cause/Issue
Equipment / Cause Equipment Design or Selection Component Failure Operational Error Installation or Maintenance Inadequate Gas or Flame Detection Emergency Shutdown Response Other or Unknown
Hydrogen Gas Metal Cylinder or Regulator   3/31/2012
4/30/1995
2/6/2013
4/26/2010 12/31/1969     3/17/1999
11/1/2001
12/23/2003
Piping/Valves 4/4/2002
2/2/2008
5/11/1999
4/20/1987
11/4/1997
12/31/1969
8/19/1986
7/27/1991
12/19/2004
2/6/2008
10/3/2008
4/5/2006
5/1/2007
9/19/2007
10/31/1980
2/7/2009 1/24/1999
2/24/2006
6/8/1998
12/31/1969
2/7/2009

9/1/1992
10/31/1980

10/3/2008  
Tubing/Fittings/Hose   9/23/1999
8/2/2004
8/6/2008
9/19/2007
1/1/1982 9/30/2004
10/7/2005
  10/7/2005  
Compressor   10/5/2009
6/10/2007
8/21/2008
1/15/2019
    10/5/2009 8/21/2008  
Liquid Hydrogen Tank or Delivery Truck 4/27/1989 12/19/2004
1/19/2009
8/6/2004 12/31/1969   1/1/1974 12/17/2004
Pressure Relief Device 7/25/2013
5/4/2012
1/15/2002
1/08/2007
12/31/1969        
Instrument 1/15/2019 3/17/1999
12/31/1969
2/6/2013
    11/13/73    
Hydrogen Generation Equipment 7/27/1999     10/23/2001      
Vehicle or Lift Truck   7/21/2011         2/8/2011
12/9/2010
Fuel Dispenser   8/2/2004
5/1/2007
6/11/2007
9/19/2007
  2/24/2006
1/22/2009
     
Fuel Cell Stack            

5/3/2004
12/9/2010
2/8/2011

Hydrogen Cooled Generator       12/31/1969
2/7/2009
     
Other (floor drain, lab
anaerobic chamber,
heated glassware,
test chamber,
gaseous hydrogen
composite cylinder,
delivery truck)
  11/14/1994
7/21/2011
7/27/1999
6/28/2010
8/21/2008
12/31/1969
3/22/2018
    6/10/2019
  • = No Ignition
  • = Explosion
  • = Fire