[ RadSafe ] Immersion, vs submersion

[Mengers, Timothy]

A colleague recently asked me a question that I thought I understood, but when he pushed for derivations I became a little less certain.   Both the 10CRF20 appendix B and the DOE's 10CFR845 refer to Immersion and Submission with respect to Derived Air Concentrations.  As I understand it, the one (immersion) is intended to address uptakes received while breathing (or absorbing through the skin?) in air while the other (submersion) is intended to address external exposure (penetrating gamma or beta) in a semi-infinite cloud (i.e. 2 pi rather than 4 pi geometry and accounting for air self-shielding and sky shine, and a non-source solid floor).   

Can someone direct us to the base reference documents (ICRP reports?) for which these were derived and provide any referenced modifiers for applying.  For example are there established or tabulated modifiers adjusting for:  when the geometry is less than infinite (small room); when a greater that two pi geometry (eg. on a cat walk), or when the media density is greater or less than standard atmospheric dry air?

Are there any similar established submersion DACS that could be applied for diving in a spent fuel pool or similar solutions/suspensions other than air?