Clarification on the scope of control masses

[Panderson]

I understand that Thermodynamics studies systems at the macroscopic level, but I am still somewhat confused with respect to closed/isolated systems. Does nuclear radiation still count as a control volume? Our instructor asked if the ISS was technically a closed/open system. Would the constant flux of radiation even be considered?

 

[Bystander]

Depends. Long run, open system. Short term? Maybe, maybe not. How sensitive is your mass measurement?