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Note added at 23 mins (2011-02-14 14:39:04 GMT)
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Там, по-моему, пропущено слово "source" после "Dry":



Category-I : Self-contained, Dry source storage
An irradiator in which the sealed source is completely contained in a
**dry container** constructed of solid materials, the sealed source is
shielded at all times, and human access to the sealed source and the
volume undergoing irradiation is not physically possible in its
designed configuration.
http://www.aerb.gov.in/T/PUBLICATIONS/CODESGUIDES/ss-6.pdf

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Note added at 24 mins (2011-02-14 14:40:40 GMT)
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А ниже там написано насчёт "влажного варианта":



Category-III : Self-contained, Wet source storage
An irradiator in which the sealed source is contained in a storage
pool **(usually containing water)**, the sealed source is shielded at all
times, and human access to the sealed source and the volume
undergoing irradiation is physically restricted in its designed
configuration and proper mode of use.

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Note added at 3 hrs (2011-02-14 17:16:51 GMT)
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Я про "несколько метров", вроде бы, нигде и не заикался... Это - не ко мне... Да и "мокрый" вариант упомянут мной лишь как альтернатива "сухому" (для лучшего понимания ситуации), и к самому вопросу, вообще-то, напрямую не относится...