Chalk River Unidentified Deposits were discovered by the Chalk River Laboratory. They discovered corrosion deposits mixing in with the primary coolant loop of the nuclear reactor.
Thermal and hydrolic shocks would jar the CRUD loose causing the radiation to skyrocket
See: Chalk River Laboratories for more information.
By 1944 the ChalkRiver Labs were opened and in September, 1945 the facility saw the first nuclear reactor outside of the United States go operational.
ChalkRiver Labs are also near the site of Canada's first nuclear power plant, a partnership between AECL and Hydro-Electric Power Commission of Ontario, which went online in 1962.
ChalkRiver Labs remain an AECL facility to this day and are used as both a research (in partnership with the NRC) and production facility (on behalf of AECL) in support of other Canadian electrical utilities.
Look up CRUD, crud in Wiktionary, the free dictionary.
CRUD (acronym), Create, Read, Update, and Delete, the basic functions of a database in computing
Chalkriverunidentifieddeposits, in nuclear engineering a type of radioactive solid which can disturb the process through encouraging the formation of emulsions known often as third phases.