Scoring DOSE-EQ from Cs-137 source

Fluka Experts,

I am trying to score to Dose Equivalent in uSv/hr at a locations 5cm
from the surface of a source holder designed for a 1 Ci Cs-137 source. I
have tried as hard as I can to glean the information I need from the
manual and previous postings to this list but I fear I still need some
clarifications.

I have setup and tested the attached input/geometry/flair files and I
believe I am on the right track.

I have an isotropic beam of 662 keV PHOTONS located at the planned
location of the Cs-137 source and the geometry plots as expected using
flair.

I am using a USRBIN for scoring using a XYZ cube that fully includes the
space of interest with 100 division on each axis.

I am scoring the DOSE-EQ generalised particle.

This setup runs successfully and generates output.

My question is regarding the meaning of the value for each USRBIN
scoring volume.

My current understanding is that this is pSv/primary beam particle, and
that to convert this to uSv/hr for a 1 Ci source I would need to
multiply this value by 37e9*85% (disintegrations per seconds for 1Ci *
by the percentage of disintegrations that produce the gamma of interest)
to determine the pSv/s for 1Ci from the 662 keV gamma rays. I do this
and the results are relatively close to simple hand calculations with
only basic corrections for build up. Is this generally on the right
track.

Secondly are there any settings with regard to EM transport that I am
missing that will greatly change the output of the USRBIN scoring.

Thanks in advance.

Robin Sheehy