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10 CFR 835, Appendix C was published in the Federal Register on January 25, 2011 (76 FR 4258) to provide updated Derived Air Concentration (DAC) values for determining radiation dose from inhaled radioactive material. The updated dose conversion factors were based on an 8 hour work day exposure time instead of the previously used 24 hour calendar day exposure. The DAC values for several radionuclides having a half-life of less than 2 hours and a certain decay mode were inadvertently not revised for the 8 hour work day exposure time. The proposed amendment to Appendix C would provide the correct DAC values for this small group of radioactive materials.

10 CFR Part 835, Appendix E was published in the Federal Register on November 4, 1999 (63 FR 59689). This appendix listed incorrect minimum amounts of radioactivity for 2 isotopes of rhodium which are necessary to activate certain requirements in the rule for controlling these materials. The proposed amendment to Appendix E would provide the correct values.