Section 39.33 - Radiation detection instruments(a) The licensee shall keep a calibrated and operable radiation survey instrument capable of detecting beta and gamma radiation at each field station and temporary jobsite to make the radiation surveys required by this part and by part 20 of this chapter. To satisfy this requirement, the radiation survey instrument must be capable of measuring 0.001 mSv (0.1 mrem) per hour through at least 0.5 mSv (50 mrem) per hour.(b) The licensee shall have available additional calibrated and operable radiation detection instruments sensitive enough to detect the low radiation and contamination levels that could be encountered if a sealed source ruptured. The licensee may own the instruments or may have a procedure to obtain them quickly from a second party.(c) The licensee shall have each radiation survey instrument required under paragraph (a) of this section calibrated-(1) At intervals not to exceed 6 months and after instrument servicing;(2) For linear scale instruments, at two points located approximately 1/3 and 2/3 of full-scale on each scale; for logarithmic scale instruments, at midrange of each decade, and at two points of at least one decade; and for digital instruments, at appropriate points; and(3) So that an accuracy within plus or minus 20 percent of the calibration standard can be demonstrated on each scale.(d) The licensee shall retain calibration records for a period of 3 years after the date of calibration for inspection by the Commission.52 FR 8234, Mar. 17, 1987, as amended at 63 FR 39483, July 23, 1998