Physicist's Notes · Ranger Survey Meter
Four cadence bands, one survey instrument,and the AERB dossier built from data.
A working radiation-safety survey programme runs at four cadence bands — daily, weekly, monthly, annual — with the radiopharmacist owning daily, the physicist owning weekly and monthly, and the RSO owning annual. This post walks each band, the NORM-screening protocol that sits alongside routine surveys, and the six-item AERB inspection dossier the Ranger USB log feeds.
The four cadence bands
What to scan, what passes, what triggers escalation
| Band | Trigger | Scan | Pass | Fail action |
|---|---|---|---|---|
| Daily — radiopharmacist | Before the first dispensing run; end of dispensing shift | Bench surface, dispensing-area floor, dose-calibrator well, waste-area corridor | All locations within ± 2× ambient background | Investigate hot spot; clean if surface; escalate to physicist if persistent |
| Weekly — physicist | One scheduled slot per week | Full hot-lab + injection-room + waste-store walk-through | No location > 4× background; all readings logged to RMS | Identify source — usually a misplaced vial, glove drop or spill incident |
| Monthly — physicist | First working day of the month | Wipe tests on all sealed-source storage cabinets + dispensing benches | Removable activity < 0.4 Bq/cm² (typical AERB threshold for sealed sources) | Quarantine the source; clean the surface; document the incident |
| Annual — RSO | Once per calendar year; before AERB inspection | Calibration check against a NIST-traceable Cs-137 reference + full facility survey log review | Sensitivity within ± 20 % of published 3,340 CPM/mR/hr; calibration certificate renewed | Send for factory calibration; replace if drift exceeds calibration tolerance twice |
Source: AERB Safety Code for Nuclear Medicine Facility; AERB Atomic Energy (Radiation Protection) Rules 2004; IAEA Safety Reports Series 40.
NORM screening
The separate protocol that sits alongside routine surveys
- NORM screening covers naturally-occurring radioactive materials — Th / U decay products in scrap metal, building materials, mining samples and some industrial scrap.
- The Ranger's 10 keV photon threshold catches the U / Th X-ray complex (typically 12–20 keV) and the Bi-214 / Pb-214 progeny line at 295 keV — the two signatures NORM screening looks for.
- Screening protocol: pass the detector window across the surface at ≈ 2 cm distance, at a walk-speed slow enough that any spot stays under the window for ≥ 5 seconds.
- Alarm threshold: typically set at 3× ambient background. Investigation threshold at 5–10× background depending on site activity.
- When a hot spot is found: log the location, dose rate, and take a wipe sample. The wipe goes to gamma spectroscopy (well counter) for isotope identification.
AERB inspection dossier
Six items the Ranger USB log feeds
- USB log file for each survey day, exported from Observer software (CSV or PDF), timestamped to the device clock
- Annual NIST-traceable Cs-137 calibration certificate, retained for the AERB facility-licence period
- Wipe-test result log: location, surface area swabbed, gamma-spec result, removable activity in Bq/cm²
- Calibration drift trend: sensitivity reading at each annual calibration, plotted to catch instrument degradation early
- Incident log: any survey reading that exceeded the action threshold, including the response taken
- AERB inspection-ready package: all six items above bundled per inspection window
Source: AERB Safety Code for Nuclear Medicine Facility — record-keeping section; manufacturer Observer software.