(ii)
airborne radioactivity,
(iii) dose rates from radioactivity deposited on the ground.
Initially the readings of dose rate from the fixed stations, if telemetered to the Monitoring and Assessment Centre, would in conjuction with meteorological data provide an early estimate of the radiation levels likely to be experienced in different areas of Hong Kong. This information should be supplemented as soon as possible with readings from portable monitors in widespread locations.
It is advised that arrangements should be made with the Fire Services, who hold suitable survey monitors at some Fire Stations, to transmit information at regular intervals after the alert. A reading of gamma dose rate external to the building should be taken at selected stations every half-hour and results recorded and transmitted to the Monitoring and Assessment Centre by radio or by telephone.
Consideration should be given to equipping about ten suitably located Stations with such monitors and to equipping some Stations with simple air-sampling equipment. (Alternatively, the Environmental Protection Department which has considerable experience in air-sampling could be called on to assist.) Readings of ambient dose rate at Fire Stations will provide a check on the initial estimates of dose patterns, which may be updated on the basis of this information. Air-sample media may be retained for collection and subsequent counting and analysis of the composition of the airborne activity.
At least three manned and equipped vehicles should be mobilised within one hour of the receipt of the warning of a major release. The mobile teams would initially be required to measure ambient radiation dose rates at a fixed height and to take air samples. The equipment needed will be simple hand-held monitors, and battery-operated air samplers. The only special requirement for the vehicles is that they should be equipped with a radio to keep in contact with the Monitoring and Assessment Centre to receive instructions and to transmit results.
The vehicles described will provide the basic requirement for mobile monitoring, and since any vehicle fitted with suitable radio communications equipment can be used, this system provides a great degree of flexibility. The use of specially adapted vehicles, with gamma spectrometry and beta counting facilities, may be considered as a means for rapid assessment of the levels of airborne activity, composition of the release, and deposition on grass and vegetation. However, it should be borne in mind that the cost of equipping and maintaining dedicated vehicles may not be justified by the likelihood of their being used, and there is a possibility that at least one vehicle may be under repair or maintenance at the time of an incident. It is therefore recommended that if fully-equipped vehicles are acquired they should be augmented by additional pre-designated vehicles which can be loaded with a prepared package of portable monitoring and sampling equipment at the time of the alert.
The use of helicopters to measure ambient dose rate and for air-sampling is possible, however, there is little experience of their use for monitoring a radio-active plume, (see comments in Section 12.9). The use of helicopters for district surveys of ground radioactivity is established and so at a later stage use of them may be made to measure deposited activity, (see comments later in this Chapter).
Deployment of monitoring vehicles will be the responsibility of the Survey Co-ordinator at the Monitoring and Assessment Centre. Routes for vehicles should be defined by identifying a number of routes (say 3 or 4) at different distances from the potential source, running in a direction approximately perpendicular to the likely plume axis (ie NW-SE). Survey points at about 2 km intervals should be defined and marked on maps available in emergency vehicles or with emergency equipment prepared for loading. These maps must also be available in the Monitoring and Assessment Centre and in the Civil Control Centre. The Survey Co-ordinator will deploy vehicles on these routes and request the teams to monitor dose rates and take samples at appropriate survey points. Initially, one
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