Chernobyl Nuclear Accident Congressional Hearings Transcript

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As I MENTIONED BEFORE, THE REACTOR CONSISTS OF 1700 CHANNELS
LIKE INDEPENDENT SMALL REACTORS. ADDITIONALLY TO THE PHYSICS
CONTROL THESE SMALL REACTORS MADE BY ONE CHANNEL MUST BE CON-
TROLLED BY ENGINEERING SAFEGUARDS FOR THERMODYNAMIC REASONS,
So FAR AS WE KNOW, THIS IS VERY DIFFICULT AND THE PROBABILITY
OF MALFUNCTION OF THIS SYSTEM IS RATHER HIGH.
The REACTION OF GRAPHITE WITH STEAM OR AIR IS MUCH SLOWER. THE
REACTION OF ZIRCONIUM WITH STEAM IS FASTER AND IN THE FIRST STATE
OF THIS ACCIDENT, GRAPHITE WAS A HEAT SINK WHICH HAS A MODERATING
INFLUENCE TO DELAY THE REACTION. THERE ARE IMPORTANT DIFFERENCES
TO WESTERN REACTOR TYPES: THE REACTOR DID NOT HAVE A CONTAINMENT
FOR THE CORE AND ALSO NOT AN EMERGENCY COOLING SYSTEM IN THE
SENCE OF OUR SAFETY PHILOSOPHY.
I SHOULD MENTION THAT IN PRINCIPLE THE MAGNOX REACTOR TYPES IN
Great Britain and in France are similar systems. Instead of a
combination of zirconium and steam, these reactors have a similar
combination OF MAGNESIUM AND CARBON DIOXIDE. BUT IN ANY CASE,
THE MAGNOX Type reactors have a much lower power density AND
IS enclosed in a BIG CONCRETE CONTAINMENT. FOR THESE REACTORS
THERE ARE GOOD EXPERIENCE OVER 30 YEARS.
The HTR WORKING with low enrichment HAS ALSO A GRAPHITE MODERATOR.
Core melting in this reactor type is excluded. In a case of loss
OF coolant, graphite is a rather large heat sink and the temperature
in this system will increase in the case of a loss of cooling
BY 600 to 700 °C IN AVERAGE AFTER 8 TO 10 HOURS. AT THIS TIME