HP-210 General: The HP-210 is a rugged, pancake geometry Geiger tube, principally designed for detecting beta radiation. The HP-210 probes have been modified by the addition of aluminized mylar resulting in a total window thickness of approximately 5 mg/em2, This approximates the 7 mg/em2 dead skin layer and gives a more accurate estimate of the hazard to humans. Calibration: Perform the following procedure at three-month intervals: 1. Inspect and clean or repair as necessary. 2. Set PRS-1 HV to 900V. 3. Using a 90sr-Y standard and the 1-minute scaler range, measure the cpm detected. Divide the epm detected by the dpm of the standard, the result is the probe efficiency. The reciprocal of probe efficiency is the calibration factor. 4 List the efficiency and calibration factor on the calibration label. HP-177C and HP-270 General: The HP-177C is a thin wall standard geometry Geiger tube with a rotating beta shield. It is capable of detecting gamma radiation alone or beta and gamma together. The HP-270 uses an energy-compensating shield to limit the characteristic over-response of Geiger tubes in the lower energy range. Calibration: Perform the following procedure at three-month intervals: 1. Inspect and clean or repair as necessary. 2. Set the PRS-1 HV to 900 volts. 3. Position the probe at the 1 mR/h distance on the calibration range with the beta Shield closed. Using the i-minute scaler range, measure the detected counts. Divide 1000 by the detected counts. The result is the calibration factor for .R/h. 4. Input the calibration factor into the rate multiplier board. 5. Position the probe on the range at the 10 mR/h and 0.1 mR/h distances. The PRS-1 indication must be 10,000 and 100 u.R/h + 20%, respectively. 6. List the calibration factor on the calibration label. SPA-2 General: The SPA-2 gamma scintillation probe uses a one-inch diameter by one-inch thick Nal(T1) crystal detector. It is a very sensitive gamma survey meter capable of monitoring in the pR/h range. : A-29-5