Tramp uranium

Fission products can be released from defects in the fuel rods or from tramp uranium on the fuel cladding. Of special importance are the volatile fission products 131—i35j M7>i38Xe in BWR steam). Cations include the Sr and Cs isotopes,... 

Small amounts of fission products leaking from faulty fuel pins or generated from uranium (leached from damaged fuel or initially present as inqiurity) deposited on the surfaces in the core (so called tramp uranium) and small amounts of activation products (most troublesome... 

The presence of radioactive noble gases in the off-gas is monitored continuously. Abrupt increases occur when fuel pins are penetrated. By considering the differ t half-lives and activities it is oftoi possible to make a rough differ tiation between tramp uranium, old leaks, pinholes and large new leaks in the fuel. 

Another application of solvent extraction to redox speciation studies is the method developed for iodine (Malmbeck and Skamemark 1995). It was used for online speciation of iodine in the Forsmark BWR power plant in Sweden. Iodine can enter the reactor water in two ways, either by fission of tramp uranium (uranium that is adsorbed on the outer surface of the fuel pins) or via leaking fuel pins. In this method, a tiny stream of water was withdrawn fi-om the reactor system and used as feed for a 20 stage mixer-settler battery. The mixer-settlers were arranged in four batteries with 4, 4, 6, and 6 mixer-settler units. Part of such a mixer-settler battery is shown in O Fig. 52.4. 

Experience has shown that removal of fuel contamination from the cladding proceeds very slowly, both when it originates from fabrication as well as from tramp uranium the predominant fraction stays on the cladding until discharge of the assemblies from the reactor core. 

Fission products also enter the coolant from residual surface contamination of the cladding by uranium (the efficiency of the cleaning in the manufacturing process is not absolute) and also from the uranium content of the cladding (a few ppm). A limit for uranium contamination ( tramp uranium ) therefore needs to be specified. 

The main probiems in design and operation of RIP plants are associated with the screens which are necessary to separate resin (or activated-carbon granules) from the pulp overflowing from each tank and finally to the effluent. These not (mly block readily with tramp rulfoi but tii are broken by careless operators and abrade resin if vibrated. Extensive piiot-plant work has been done by Carman and Read to develop a plant with resin floating in the puip in efforts to develop a scteenless RIP recovery process for both uranium and gold. 

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