Fuel assembly for fast reactors

A fuel assembly for fast reactors comprising:

• a hexagonal wrapper tube;
• an entrance nozzle for coolant provided on a lower end of said wrapper tube;
• a handling head provided on the other end of said wrapper tube and having a coolant outlet opening;
• a supporting member secured to a lower inside portion of said wrapper tube;
• and
• a bundle of fuel elements arranged in rows in three directions equiangularly oriented in said wrapper tube and supported by said supporting member, said bundle of fuel elements consisting of A-type fuel elements and B-type fuel elements, the number of B-type fuel elements being substantially less than the number of said A-type fuel elements, said A-type fuel elements consisting of fuel pins of a first diameter having a wire spacer of a first diameter wrapped therearound, said B-type fuel elements consisting of fuel pins smaller in diameter than said fuel pins of said A-type fuel elements and having a wire spacer larger in diameter than said wire spacers of said A-type fuel elements wrapped therearound, said B-type fuel elements being dispersedly arranged in each row of said bundle of fuel elements so that a sum of gaps formed between said wire spacers of said A-type fuel elements and said fuel pins of said B-type fuel elements increases by at least one-half of the diameter of said wire spacer of said A-type fuel element, and a pitch between adjacent ones of said A-type and B-type fuel elements in said bundle of fuel elements is substantially equal to a pitch between adjacent ones to said A-type fuel elements.

A fuel assembly for fast reactors comprising:

• a wrapper tube;
• a plurality of first fuel pins arranged in rows in said wrapper tube and forming a major part of a bundle of fuel pins;
• a plurality of first wire spacers, one of said first wire spacers being wound around a respective one of said first fuel pins so as to maintain a distance between adjacent ones of said first fuel pins;
• a plurality of second fuel pins arranged in said rows of said first fuel pins and forming a minor part of said bundle of fuel pins, said second fuel pins having a diameter smaller than the diameter of said first fuel pins;
• a plurality of second wire spacers, one of said second wire spacers being wound around a respective one of said second fuel pins, said second wire spacers having a diameter larger than the diameter of said first wire spacers, a pitch between adjacent ones of said first and second fuel pins being substantially equal to a pitch between adjacent ones of said first fuel pins, said second fuel pins and said second wire spacers being arranged in said rows of said plurality of said first fuel pins and said first wire spacers so that a sum of gaps between said first wire spacers and said second fuel pins in each of said rows is approximately the diameter of one of said first wire spacers.