Fission product removal

The American faciUties also differed fundamentally from the British faciUties in regard to maintenance philosophy. The American plants were designed to employ remote maintenance, ie, to remove and replace equipment using shielded cranes operating inside the shielded stmcture. The British developed a contact approach based on simplified designs for equipment downstream of the fission product removal step. The British approach has been used at all commercial faciUties. 

Under similar conditions to those under which Np(V) is photogenerated from Np(IV) and/or Np(VI) (Eqs. 16-20), Pu(III), (IV) (VI) are photo-chemically converted to Pu(IV) and (VI) while all U species are ultimately converted to UC>22+. Pu(IV), Pu(VI) and U(VI) are extractable into TBP while Np(V) is not thus, this suite of reactions may form the basis of a process for Np separation. Within an advanced PUREX flowsheet, this would find utility at the point of fission product removal, the Np being routed with the HAW stream. 

G8. Goode, J. H. (ed.) Volatile Fission Product Removal from LMFBR Fuels, Report ORNL-TM-3723, 1972. 

In this approach, the decision about the adequacy of a proposed site could be taken only on the basis of the plant power level and, possibly, on the specific characteristics of its fission product removal systems (to be evaluated and possibly validated on a case by case basis). 

Fission Product Removal Requirement for Containment Spray... 

The pH of the aqueous solution collected in the containment sump after completion of injection of containment spray and ECCS water, and all additives for reactivity control, fission product removal, or other purposes, should be maintained at a level sufficiently high to provide assurance that significant long-term iodine re-evolution does not occur. Long-term iodine retention is calculated on the basis of the expected long-term partition coefficient. Long-term iodine retention may be assumed only when the equilibrium sump solution pH, after mixing and dilution with the primary coolant and ECCS injection, is above 7 (Reference...). This pH value should be achieved by the onset of the spray recirculation mode. 

One unit for fission products removal from containment ... 

FISSION PRODUCT REMOVAL BY CONTAINMENT SPRAYS OR POOL... 

A molten salt reactor (MSR) is a reactor in which fluorides of fissile and fertile elements such as UF4, PuFg, and/or Thp4 are combined with carrier salts to form a fluid fuel. MSRs can operate as simple burner reactors with high fuel economy or with the addition of online fission product removal and can achieve breeder status. Typical operation sees molten salt flowing between a critical core and an intermediate heat exchanger. A secondary coolant salt then transfers heat to a steam or closed gas cycle. The majority of work has involved fluoride salts, as corrosion-resistant alloys have been shown to be compatible with these salts. 

In 1968, the development of a new fission product removal method that could function in the presence of thorium and an ingenious technique to limit neutron leakage in a single fluid design along with the plumbing problems of the two fluid design mentioned above led ORNL to abandon its two fluid breeder concept. Liquid bismuth reductive extraction (ORNL-TM-3137,1971), while not a simple technique, was shown to be able to differentiate between thorium and the very important rare earth fission products. 

The recycle based on electrometallurgical recycle and remote vibropack refabrication technology produces a commixed stream of all transuranics and can achieve incomplete fission product removal such that the transuranic materials during processing at the centre and during fresh and used cassette shipping would be always at least as unattractive for military use as is LWR spent fuel [XXIV-19], No transuranics (except trace recycle loses) is assumed to go to the waste repository. 

After several runs of the electrolysis process, the active metal fission products such as alkali, alkaline earth and rare earth metals are accumulated in the molten salt. The accumulated fission products must be removed from the molten salt because they will affect the recovery efficiency of U and TRU. Periodically, the molten salt is removed from the electrolysis cell, purified using the salt purification process and recycled to the electrolysis cell. However, the molten salt always contains U and TRU with the fission products because the electrolysis is used to recover pure U and TRU without fission products. Therefore, fission products removed from the molten salt are always accompanied by some amount of U and TRU. It is necessary to optimize between the loss of U and TRU and the quantity of fission products removed because an increased removal of the fission products results in an increased contamination by the TRU in the waste stream. 

Regarding fission products °Sr, Cs, Cs and were assumed to be recovered with a 95% removal efficiency, to satisfy regulations on heat load and volume of the disposal facility. Table XXIV-5 and Table XXIV-6 list the evaluated total TRU and fission product waste production from pyro-processing for a DF = 2.3x10 and a 95% fission product removal efficiency, respectively. 

Develop updated fission-product removal system flow sheet, which is compatible with all goals... 

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