TNAG-1503-FCO40-2061-Guangdong-nuclear-power-station-project-at-Daya-Bay-safety-c-1986 — Page 77

4. Ten channels in the reactor will be adapted for rapid acting safety rods. These will act over a period of 1-2 seconds (compared with 20 seconds previously).

for use in these rods has not yet been chosen.

The material

Bone marrow syndrome occurred in patients who had received doses about 2 Grays (200 rads). They were treated as far as possible in sterilised ward conditions even though standard wards had to be developed for this purpose.

There was considerable press reporting of the bone marrow transplant operations. These were not successful for the patients concerned who had, however, received doses in the region of 4 Grays (400 rads) and most were suffering both from severe radiation sickness and severe radiation burns.

Professor Kuskova warmly commended work by Sir Edward Pochin on risks from radiation, which had proved in Soviet experience to be accurate.

Dosimetry

The meeting then heard from Professor Pavlovski on dosimetry matters. Immediately after the accident people in the largest town in the area, Pripyat, were advised only to shelter because dose rates in the town were still comparatively low. Iodine was distributed to children's establishments because children (high consumers of milk) were seen to be more particularly at risk from thyroid dose. When the dose rate reached 1 roentgen per hour a day after the accident, evacuation had been ordered. It had now been calculated following the very considerable monitoring of people that for 97% of the people evacuated from Pripyat the iodine content of the thyroid indicated a thyroid dose of 30 rad (said by the speaker to be close to UK experience in the Windscale 1957 accident). Mortality from thyroid cancer may have been increased by 1%.

Measurements suggested that the majority of the population in the 30 km zone did not exceed a dose of 25 rem, although a few people may have received 30 to 40 rem. The collective dose estimated for the evacuated population was 1.6 million

manrems.

The accident had perhaps increased the death rate in the region by 1.6%.

Decontamination

Dr Krakov then spoke about decontamination. Obviously contamination at the reactor site, around all 4 units was considerable.

area were:

The principles worked to in decontaminating the

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