A radiation survey without a calibrated instrument can find where an electroscope behaves differently from its baseline, and nothing more: it cannot rate an area safe, because the device cannot be calibrated and its sensitivity is unknown. A survey party therefore works conservatively, with a baseline test first, a fixed spacing between readings, an outside contact who knows the route, a rule to stop and retreat on any change, and a written record.
Part of Radiation Safety
A radiation survey is a systematic walk to locate where radiation or contamination is elevated, so that people can be kept away from it and the places to avoid can be mapped.
Decide Whether To Go At All
A survey is itself an exposure. Before sending anyone, ask what decision the survey serves: a route, a water source, a field, a building. If the answer is “curiosity”, do not go. If the area is a nuclear facility, do not go; the right relationship with a damaged facility is distance, as set out in Nuclear Facility Hazards. A survey party cannot assess a reactor, a fuel pool or a waste store from its edge.
The Parent Article’s Procedure, With Its Limits Stated
The parent article, Nuclear Safety, sets out six steps. They are kept here with what each can and cannot support:
- Approach from upwind. Airborne dust blows downwind. This reduces the dust you walk into, but ground that has already received contamination stays contaminated whichever way the wind blows now. Upwind is not clear. Wind directions are named for where the wind comes from; see Wind Direction Reading.
- Take an electroscope reading every 200 meters. This is the parent’s spacing, not a derived value. Along a 2 km line at 200 m, that is 2,000 / 200 = 10 intervals and 11 readings including the start.
- Mark locations where readings change on your map. Use a shared legend; see Sketch Mapping and Map Making.
- If readings increase, stop, note the position and retreat to reassess.
- Never approach a suspected nuclear facility alone, and keep someone outside the area who knows your route and timeline.
- Limit exposure time to the minimum needed in any area showing elevated readings.
Before Each Walk
- Test the electroscope at the base on the day, in the same way as the baseline (see Electroscope Construction). If it falls faster than usual at base, the weather has changed; do not start.
- Agree the route, the turn-back time and the outside contact. Write them down.
- Dress for contamination (Personal Protection).
Reading The Result Honestly
| Result | Meaning | Action |
|---|---|---|
| Leaf fall matches baseline | Nothing detected; sensitivity unknown | Treat the area as unconfirmed, not clear |
| Leaf fall faster than baseline | Something discharges the air; may be humidity or radiation | Stop, retreat, repeat at the last good point |
| Fast fall in seconds | Possible strong field | Withdraw at once and mark the position |
Because the device cannot say how much, a survey like this manages distance, time and shielding by assumption. That is an argument for conservatism rather than for improvising a number. Classify the ground with Zone Classification, and record the results; see Record Keeping.
After The Walk
Everyone and everything that went out is treated as possibly contaminated: remove outer clothing outdoors, bag it, wash exposed skin and hair, then log times and positions. See Decontamination.
Common Mistakes
- Spacing readings by convenience. Keep the same interval so that the map is comparable.
- Surveying alone. If you collapse, nobody knows where.
- Continuing “just a bit further” after an increase.
- Writing “clear” on a map. Write “no change detected”.
Safety
The survey is a dose
Every minute spent on contaminated ground adds to a total you cannot measure. Keep the party small, the route short and the time fixed. Do not eat, drink or smoke in the survey area. Anyone feeling unwell, vomiting or confused ends the survey and goes to treatment, not onward.
What’s Next
- Learn next: Zone Classification — turning results into rules for each place
- Combine with: Contamination Zones — mapping and managing hot spots