Patent Number: 055531091
Section: claims

1. Apparatus for simulating a nuclear fuel rod bundle transient comprising: a vessel for containing a coolant;  a plurality of nuclear fuel rod simulating members disposed in said vessel for disposition in the coolant and forming a simulated nuclear fuel rod bundle;  each member including a pair of heating elements;  a power supply for supplying power over time to each of said heating elements; and  means for independently controlling and thereby varying the supply of power over time to each said heating element of each member of said plurality of nuclear fuel rod simulating members thereby to simulate a change over time in both power output and axial flux shape of a nuclear fuel rod bundle.  independently supplying power to said heating elements of each said member; and  controlling said supply of power to said heating elements independently of one another to vary the power supply over time to each element to simulate a change over time in both the (i) power output and (ii) axial flux shape of a nuclear fuel bundle.  providing at least one nuclear fuel rod simulating member within a vessel containing a coolant;  providing said member with a pair of heating elements extending substantially the full length of said member;  independently supplying power to said heating elements of said member; and  controlling said supply of power to said heating elements independently of one another to vary the power supplied over time to each element to simulate a change over time in both the (i) power output and (ii) axial heat flux shape of a nuclear fuel bundle. 2. Apparatus according to claim 1 wherein said pair of heating elements terminate at one end within said vessel and at other ends outside said vessel. 3. Apparatus according to claim 1 wherein said pair of heating elements have ends terminating outside said vessel. 4. Apparatus according to claim 1 wherein said heating elements comprise a double helix arrangement thereof, a surrounding tubular cladding and electrical insulating material between said heating elements and said cladding. 5. Apparatus according to claim 1 wherein said heating elements are coaxial relative to one another and an electrically insulating material between said coaxially arranged heating element. 6. Apparatus according to claim 5 wherein said pair of heating elements have ends terminating outside said vessel. 7. A method for simulating a nuclear fuel rod bundle transient in a vessel having a plurality of nuclear fuel rod simulating members, each member having two heating elements, comprising the steps of: 8. A method for simulating a nuclear fuel rod bundle transient comprising the steps of: