So you are going to put the fissile material which operates at muti megawatts in a briefcase and carry it away?
Disregarding the health and safety issues of the briefcase carrier the briefcase is sure to turn into a pile of molten radioactive sludge very quickly.
I believe the 1% of nominal output is a reasonable ballpark for cooling requirements after a reactor is shut down. 1% of 1MW is still 10kW. You probably don't want to transport that in a briefcase.
Disregarding the health and safety issues of the briefcase carrier the briefcase is sure to turn into a pile of molten radioactive sludge very quickly.