Interim decay storage

The classical Purex process was designed to produce nearly pure uranium and plutonium. The Chemical Engineering Division of Argonne National Laboratory has demonstrated UREX+, an advanced aqueous process with five extraction trains that split commercial reactor spent fuel into five streams 1) a nearly pure uranium stream (95.5% of the heavy metal in the spent fuel) 2) technetium sent to transmutation (0.08 /o) 3) Pu/Np converted to MOX fuel for LWR fuel and Am/Cm for transmutation or fast-flux reactor fuel (0.962 /o) 4) Cs/Sb decay heat producers sent to interim decay storage (0.017 /o) and 5) a mixed fission product stream (3.44 /o) composed of gases and solids incorporated into a waste form for geological repository disposal.f The percentages shown are computed from Table 1. 

Fig. 5.5. FFTF driver fuel-handling sequence between interim decay storage and reactor vessel.

After reactor shutdown, the refueling plug in the reactor vessel lid is removed from the fuel transfer port and an adapter and floor valve are installed on the port. The control rod drive shafts are also discoimected, and the instrument trees are moved to their stored positions. The CLEM then picks up the CCP (with the fresh-fuel assembly) from the interim decay storage vessel, transports it to tiie reactor, and lowers it into the reactor through a fuel transfer port. 

The CLEM then picks up the CCP, containing the SNF assembly, and transfers it to the interim decay storage vessel. The cyclic process of moving fresh fuel to the reactor core and SNF back to the interim decay storage vessel continues until all the refueling operations have been completed. Before reactor startup, the IVHMs are placed in their stored positions in the reactor, the instrument trees and control rod shafts are restored to power-operation status, the adapters and floor valves are removed, and the fuel transfer ports are sealed with their plugs. 

After a suitable decay period, the bottom-loading transfer cask picks up the SNF assemblies from the interim decay storage vessel and transfers them out of containment to the fuel storage facility. This operation can be done after the reactor is back online. 

Component transfer. It is the transfer station between the bottom-loading transfer cask, which operates outside the containment area and CLEM, which remains inside the containment area and operates only when the reactor is shut down. Consequently, both the bottom-loading transfer cask rails and CLEM rails traverse the interim decay storage cover. 

The CLEM transfer of components from the reactor core to interim decay storage is a transient condition, with three cases indicated. As is realistically shown, longer transfer times result in steady-state temperatures that will not compromise the assemblies, and the cases shown represent maximum conditions. Interim decay storage for all but the maximum decay power assemblies (drivers or test assembly) will be nominally at temperatures of 204°C (400°F). 

Criticality Anaiyses for the FFTF interim Decay Storage Faciiity, W. L. Bunch, D. R. Marr (West-Han/ord)... 

The Interim Decay Storage (IDS) facility provides storage for fresh or irradiated fuel for the Fast Test Reactor (FTR), A series of one- and two-dimensional transport and diffusion theory calculations was made -to establish the hUective multiplication factor of the IDS facility when fully loaded with initial driver fuel for the FTR, and also to establish the upper plutonium content of fuel that can be stored in the facility. No consideration was given in these analyses to accidents in which sodium coolant would be lost or fuel spacing changed. 

Hg(I03)2, and Sr(IO3)2 Long time extrapolations of leach rates are uncertain to one or two orders of magnitude, but the data indicate that if the disposal form comes in continuous contact with the water the 1Z9I will be released before it has decayed. Thus, good disposal strategy includes a mechanism for dispersal such that dilution to harmless levels is achieved. For interim storage, where a dry environment can be assured, and for transportation, the forms appear to be adequate. 

To increase the interim storage capacity at nuclear power stations compact storage frames have been incorporated into the decay pools. 

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