b'Design of Severe Accident Test Station Fission Gas Release CapabilityPrincipal Investigator: Jason HarpTeam Members/ Collaborator: Yong Yan, Adam James, Chuck Baldwin, Nathan CappsT he available data on transientperformed that results in a fission gas release (tFGR)mechanistic model for tFGR.relevant to light water reactorsUnderstanding tFGR will require (LWR) is sparse [16] and the fuelcollecting data on a variety of fuel conditions covered by this data areconditions in separate experimental also limited. Creating additionalapparatus some of which isolate key relevant tFGR data that is applicablevariables while some evaluate the to different fuel irradiation historiesintegral tFGR response.To this end, is complex for several reasons. ORNL is developing two systems to There is not a viable surrogate forfurther study tFGR.One system is irradiated nuclear fuel that candesigned to focus on visualization be used to study this behavior. and tFGR from small samples of This limits the study of tFGR tofuel during rapid heating (featured facilities that can safely handleelsewhere in this document). The and refabricate irradiated fuel intoother system will focus on integral relevant test items.The availabletFGR tests under as representative data suggests tFGR testing must beas possible conditions.It will be carried out under fuel pin relevantcoupled with the ORNL Severe Acci-pressure (~10 MPa) to be characteristicdent Test Station (SATS) and builds of in-pile conditions [2,6].Thisupon previous ORNL experience with increases the complexity of systemsthe Core Conduction Cooldown Test designed to capture tFGR becauseFurnace (CCCTF) [7].they must handle high pressures.Measurement of tFGR is typicallyProject Description:accomplished by measuring theThe goal of the integral testing is to release of the long-lived radioactivecapture the onset temperature of fission product Kr-85 with gammatFGR and the amount (moles of gas) spectrometry. An additional compli- of tFGR for a segment experiencing a cation to detecting tFGR is the shortrepresentative loss of coolant accident timescale over which tFGR occurs. (LOCA) transient.This release is also The release appears to occur in abeing measured while the fuel is burst at certain on-set temperaturesunder mechanical constraint by the [3,4].Attempts to capture the onsetcladding and under representative of release at pressure have previously fuel pin internal pressure prior to used a stepwise approach to collectingthe segment bursting. For the ORNL Kr-85 [6].Given the complexity ofapproach, segments of irradiated fuel this phenomenon, it is doubtfulwill be cut into 15 to 30 cm segments.that a perfect experiment can be These segments will be refabricated with end-caps and connected to 88 2022|AFC ACCOMPLISHMENTS'