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Figure 8.2 – Graph for determining zones of a radioactive cloud after an
accident at the NPP: L – length of zone, km; b – width of zone, km; M –
Radiation Hazard Zone; A – Low-Radiation Zone; B – Medium-Radiation Zone; V
– High-Radiation Zone; G – Extreme Caution Zone

The actual radiation situation are appeared by the detection radiation after
the fallout of radioactive substances from the radioactive clouds. To collect data,
perform the operations in next order:
1. Measure the radiation levels P meas. at the different points of the area on the
time t meas. relative to the accident, hour – R/hour. Measurement time relative to the
accident is determined as:
t meas. =T meas – T accid. , hour (8.1)
where T acid. – time of accident; T meas. – measurement time (astronomic).
2. Recalculate the radiation levels on 1 hour after the accident by the
formula:
, rad/hour (8.2)

where P t meas. – radiation level at the time of measurement relative to the accident,
rad/hour;
K tmeas. – coefficient of conversion of radiation level at the time of
0.3
measurement t meas. , defined by table 8.3 or calculation: K tmeas. = (t meas. ) – for
0.4
reactors RBMK – 1000; K tmeas. = (t meas. ) for reactors VVER – 1000.
3. Recalculated radiation levels on 1 hour, P are plotted on a map in the
1
relevant measurement points.
4. Items with radiation levels equal or close to their values on outside the
boundaries of the zones M (0.014 rad/hour), A (0.14 rad/hour), B (1.42 rad/hour),

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