Accidental Hydrogen Formation and Explosion at a Nuclear Reactor
The event occurred during the decommissioning of a nuclear power plant. It involved a tank containing 100 kg of residual sodium from the decommissioned experimental nuclear reactor which was using liquid sodium as coolant. The reactor had been shut for many years. A heavy alcohol compound was used to to create a stable salt (sodium is very reactive in presence of oxygen or water). This method had previously proved successful. This time however, the alcohol compound probably decomposed, releasing hydrogen and other gasses and eventually rupturing the tank.The pressure wave caused by the explosion caused one fatality, some injuries and the destruction of a gallery nearby.
Event Date
March 31, 1994
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes (Select all applicable options):
Cause Comments
According to one of the source (Nucleonics Week, see References), the alcohol used was ethyl carbitol, and research had already shown the possibility that the chemical decomposition (cracking, creating gaseous hydrogen) of this heavy alcohol could occur at temperatures much lower than previously assumed.
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
experimental nuclear reactor, waste treatment, storage tank with sodium
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The nuclear reactor was an experimental fast breeder using sodium as coolant.According to the New Scientist article (see References), most of the radioactive elements contained in the coolant had been filtered out of 37 t of sodium, by using an ad-hoc process. In this process, the sodium is mixed with a solution of sodium hydroxide. The reaction takes place in an oxygen-free environment to prevent explosions, and hydrogen is pumped out. The sodium left in the tank was thus radiation-free.
Currency
Lessons Learned
The sources do not mention corrective actions or recommendations issued to avoid the repetition of the accident, but the ARIA report (see References) states that the inspection experts identified a series of operative inadequacies and shortcoming in installation safety.
Emergency Action
The plant first responder were able to easily control the resulting fire of the alcohols.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
NewScientist news of 23 April 1994,
https://www.newscientist.com/article/mg14219221-400-fatal-blast-at-reti…
(accessed December 2020)
Event description in the French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/5135/
(accessed December 2020)