A Taiwanese 1999 conference abstract documents lost cobalt-60 sources entering an electric arc furnace with scrap and producing contaminated rebar in 1982-83
A paper by Chao and colleagues, presented at TENR II (Rio de Janeiro, 12-17 September 1999) and printed in IAEA-TECDOC-1271, reports that cobalt-60 sources were lost and "entered the electric arc furnace" in Taiwan between October 1982 and January 1983, yielding contaminated rebar. The abstract dates the rebar by its cobalt-60 activity and trace-element concentrations.
The same abstract gives counts for 1994-1999: "53 discoveries of radioactivity in ferrous scraps by steel companies," comprising 15 orphan radioactive sources, 16 cobalt-60 contaminated rebars, 20 NORM-contaminated scraps, and two unknowns.
This is a demonstrated source-in-the-charge route: a discrete Co-60 source melted with scrap. It is a high-activity, accidental case. It does not show that the same route explains the trace (mBq/kg-scale) cobalt-60 measured in ordinary commercial stainless steel; connecting the two is inference. The route is of the same family as the generic scrap-feedstock attribution in claim-zhang-2016-names-scrap-metal-feedstock-as-commercial-steels-cobalt-60-source and the gauge-source assertion in claim-heusser-1995-traces-steel-cobalt-60-contamination-to-furnace-gauge-sources. Like them, it names no atmospheric pathway (claim-no-primary-source-names-atmospheric-entrainment-as-steels-cobalt-60-pathway).
The record's printed title misspells "Cobalt" as "Cobald"; it is reproduced as printed.
Source
“The cobalt-60 activity and trace elements concentrations of contaminated rebars confirm that all of them were produced domestically in the period from Oct. 1982 to Jan. 1983, when the cobalt-60 sources were lost and entered the electric arc furnace to produce the contaminated rebars.”
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