RRFM 2009 Transactions - European Nuclear Society

Figure 2: The Si doping facility is approaching the irradiation channel
In order to allow the decay of the induced 31 Si activity the irradiated Si ingots are left for 2
days in the decay area of the FRM II’s storage pool. Subsequently they are taken out using
again the vacuum equipment for moving them from the irradiation basket into the loading
basket. Upon taking them out of the reactor pool the ingots are rinsed with fresh deionized
water and finally cleaned in an ultrasonic bath.
Before shipment back to the customer the Si is released according to the German
radioprotection regulations. The limiting values to be met are a surface contamination of
< 0.5 Bq/cm² and a specific activity of < 0.09 Bq/g. It is noteworthy that in general the
mentioned limits are kept without problems, a fact which impressively demonstrates the
purity of the starting material.
Already in 2007, the first year of operation of the semiautomatic Si doping facility, a total 3.8 t
of Si was processed in 180 separate irradiations. Since the industrial demand turned out to
be continuously high these numbers were increased in 2008 to 9.8 t and 526 single
irradiations. In order to satisfy this demand a two shift system for Si doping was implemented
at FRM II in June 2008.
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