Abstract: According to an embodiment of the present invention, a rotating nozzle assembly includes a rotatable shaft having a bore to transport a cryogenic fluid therethrough. The rotatable shaft has an upstream portion associated with a feed chamber and a downstream portion. The nozzle assembly further includes a seal disposed within the feed chamber and surrounding at least a portion of the rotatable shaft, and a seal backup disk disposed proximate the seal. The seal backup disk includes an orifice surrounding an outside diameter of the rotatable shaft, the orifice having a diameter such that, when the cryogenic fluid is flowing through the bore of the rotatable shaft, the rotatable shaft can freely rotate while the seal prevents the cryogenic fluid from seeping past the seal.