This code system http://hl7.org/fhir/v2/0935 defines the following codes:

CodeDisplayComments
ASCApheresis Software Crash
BSCManufacturing Software Crash
CFTCouldn't follow through with donation (scared)
DBBBathroom
DCWCouldn't wait
DNIPhlebotomy Issue
GFEGeneral Facility EmergencyPower outage, natural disaster (tornado, flood, hurricane, etc.), air conditioning failure, etc.
NRGNo reason given, donor decided to stop without giving a reason
PCDPhone Call-Donor