TNAG-1776-FCO40-2530-Daya-Bay-nuclear-power-station-project-safety-concerns-in-Ho-1988 — Page 173

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water samples at different depths in, say, a reservoir. A carrier solution should be added to the water sample to prevent plateout of the radionuclides on the walls of the container. Milk samples should be collected, again using polythene containers, from the bulk tanks at individual farms. A preservative should be added to the milk at the

time of collection.

If helicopters are used to conduct surveys of deposition, they should be equipped with scintillation detectors and ratemeters which are capable of detecting a level of deposited activity of 13 kBq m-2 I-131 from a height of 50-100 ft. There are a number of sophisticated systems for aerial radiation survey work (ref 22), but in view of the limited requirement in Hong Kong it is recommended that only basic equipment should be kept in readiness.

Monitoring Equipment for the Recovery Stage

Monitoring of foodstuffs, both locally produced and imported, will require use of a large number of contamination monitors. Instruments should be available for suitably trained Agriculture and Fisheries Department, and Municipal Services Branch personnel to carry out monitoring of produce and foodstuffs. It is recommended that at least 20 such instruments should be kept in readiness.

The lower DERL for contamination of green vegetables is such that they may be monitored fairly easily using simple instruments. Monitoring for contamination of livestock is more difficult, although livestock monitors have been developed. Monitoring of meat may (depending upon the DERL value used) require laboratory preparation and analysis of samples.

Laboratory Equipment for the Emergency Monitoring Programme

Samples collected during the emergency monitoring programme will be returned to the Radiation Laboratory at King's Park, or other predetermined laboratories.

During the early phase of an emergency, before the radioactive plume has dispersed, available resources will be concentrated on the testing of air sample material, in order to determine the magnitude and extent of the dose to population and to determine the composition of nuclides in the release. The laboratory equipment that will be needed during the early phase is described in Appendix IV.

In the intermediate and recovery phases of the accident, analyses will follow the pattern of the routine environmental testing programme, but with a greatly increased volume of samples and consequently a greatly increased workload. In terms of testing vegetation, milk, and other foodstuffs, soil samples, and water samples, the throughput of sample analysis will be governed by the availability of testing equipment and trained laboratory staff. Due to the remoteness of the risk of a major accident it is not considered justifiable to supplement the equipment or staff involved in routine testing to cover all possible demands in an emergency, however some analyses could be carried out at other laboratories (see Section 12.17). It will be essential to plan the priorities of testing to concentrate resources on samples that will provide the information which is most valuable in assessing the need for countermeasures to protect the public, and defining the areas where countermeasures are to be applied.

All samples brought back to the King's Park or any other laboratories must be checked for contamination on the outer containers and also dose rate from the sample before being allowed into the laboratory. This is to ensure that loose contamination is not brought into the laboratory, and to ensure any highly active sample does not significantly affect the radiation background in the laboratory. A suitable ante-room and equipment should be provided for this purpose.

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