(1) A licensee shall calibrate the survey instruments used to show compliance with this section and WAC 246-240-587 before first use, annually, and following a repair that affects the calibration. A licensee shall:

(a) Calibrate all scales with readings up to 10 mSv (1000 mrem) per hour with a radiation source;

(b) Calibrate two separated readings on each scale or decade that will be used to show compliance; and

(c) Conspicuously note on the instrument the date of calibration.

(2) A licensee may not use survey instruments if the difference between the indicated exposure rate and the calculated exposure rate is more than 20 percent.

(3) A licensee shall retain a record of each survey instrument calibration in accordance with WAC 246-240-566.