[ RadSafe ] Th-232 in capacitors

Rees, Brian G brees at lanl.gov
Thu Jul 24 13:48:26 CDT 2014

We recently came across some items labeled as capacitors that have Th-232, on the order of 4-5 uCi (1.5E5-1.85E5 Bq) each in a 2" x 13" cylinder.  They were part of 375 kV (electric) breakers.  The Th-232 was determined by HpGe spectroscopy.  They are not ceramic insulators.   There is no manufacturer data on them, just a simple label - Capacitance at rated voltage 208 pF @ rated power, Power factor at 10kV - max 65kV.

Does anybody have an idea of what function they provided, and why there's so much Th-232 in them?  I've never heard of Th-232 being in capacitors.  The breaker was built in 1980, I don't know if they are original.

Brian Rees

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