How much energy is needed
to melt 50 kg of uranium dioxide when it melts at 2865 °C (3140 K) ?
From: http://en.wikipedia.org/wiki/List_of_nuclear_power_accidents_by_country
Saint-Laurent-des-Eaux, France
17 Oct 1969
50 kg of uranium dioxide melted inside of the A1 nuclear reactor of Saint-Laurent-des-Eaux, during a refueling operation
Melting point = 2865 °C (3140 K)
http://jcp.aip.org/resource/1/jcpsa6/v25/i6/p1089_s1?isAuthorized=no
More info:
http://www.jstor.org/discover/10.2307/3577916?uid=3739448&uid=2129&uid=2&uid=70&uid=3737720&uid=4&sid=21101552799357