[en] As a result of experimental investigations, a restrictor unit for the Dragon fuel element purge flow to be placed in series with each fuel element has been developed. If the total purge flow is constant at a value of 5 litres/sec of helium at 350°C and 20 atm., and the normal pressure drop down a fuel element ≈ 4 p.s.i., in the event of one fuel element being badly seated on its spike, the effect of the restrictors will be to maintain the purge flows through the other 36 fuel elements to within #Tilde operator#95% of their intended values.