[ RadSafe ] Feild instruments for low activity gamma in soil

[Owen, Austin Andrew]

Hello,
Does anyone know of a field instrument capable of detection of 7 pCi/gm gamma in soils for Thorium remediation.  To be used in Northern Illinois with a higher than average Rn background?  
If so, has DOE or EPA approved use of instrument to meet free release criteria and/or screening for lab analysis. 
I would also be interested in any previous technical papers used to justify use of instrument or combination of scanner and scalar. 
Thanks

Andy Owen
Health Physicist
DOE - AMSTS
Engineering and ISC Services Division
(865) 576-0852