TNAG-0021-FCO40-57-Facilities-for-US-Forces-1968 — Page 104

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D.IB. 149 4.1.68

AMOUNT OF NEW DEBRIS FROM LATEST CHINESE TEST SMALL OVER HONG KONG

The monitoring of the radioactivity in air-borno dust over Hong

Kong during the period following the explosion over China on December 24

indicated that the amount of new dobris arriving over the Colony must bo

Small, a spokesman of the Royal Observatory said today (Thursday).

Had large quantities arrived it would havo been readily dotoctod

above the level of the activity due to naturally occurring radioactive

materials, he pointed out.

Since it was prosent in small amounts its presence could only be

confirmed after the naturally occurring radioactive materials had decayed.

This takes about four days from the time the dust sample is collected.

"This time had now elapsed and investigation shows that now fall-out

material began to arrive over the Colony between 9 a.m. on December 23 and

9 a.m. on December 29, he said.

The maximum total beta activity was 1.2 micro-micro curios per

cubic metre recorded botwoon 9 a.. on Docember 29 and 9 a.m. on

December 30. It is estimated that the sample removed on New Year's Day

contains no new fall-out material.

For comparison the maximum total bota activity (in micro-micro

curios per cubic metre) recorded in Hong Kong from previous incidents are:

96 for the 1962 weapons test period,

165 for the fourth Chinese test on

October 27, 1966,

Docember 27, 1966,

9.9 for the fifth Chinese test on

1.0 for the sixth Chinose test on June 17, 1967.

"It can be seen that the increase in the radioactivity in the air

over Hong Kong duo to the latest incident is insignificant," the spokesman

said.

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