Hi,

I'm currently working on stressing a reactor (at 500°) and the piping connected to it. I modeled the reactor as 18" pipe with 4" pipe connected. I had to model the reactor as pipe because we needed to find out how much growth occurs. My question is this: If I need to find the reactions at the 4" nozzles connected to the reactor, how do I model the nozzles? Since they are connected to essentially another piece of pipe I keep getting the error "More than one non-zero length element attached to the nozzle".

I would probably model the reactor as a weightless rigid element instead but that part is up to you. Rigid elements do undergo thermal expansion. You should run a weightless rigid element from the centerline of the reactor at the elevation of your nozzle, out to the radius of the reactor so you have a node number at the actual nozzle location. From the error you indicated I would assume you are attepting to use a WRC297 nozzle flexibility calculation. That is fine, but you need a separate node number for the nozzle and vessel. You therefore simply use a different node number on that weightless rigid at the nozzle location than you do on the pipe element at the same location that represents your nozzle. Then in the WRC297 nozzle specification you give the pipe element node number as your nozzle node, and the rigid element node number as your vessel node. Then Caesar II will have thermal displacements accounted for and the reactor shell flexibility acting between the nozzle and vessel node numbers.