The accumulation and behavior of radon in the home, school, preschool and other buildings during the summer

A. Vasidov, U. S. Salikhbaev,

A. A. Kist, and R. I. Radyuk

MEASUREMENT OF THE VOLUME ACTIVITY

OF RADON IN URANIUM WASTE ZONES

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the radon level averaged over a long period of time. It is the prolonged measurements that have a direct bearing on the eval-

uation of the yearly effective irradiation dose obtained by humans. The 25 

×

25 mm CR-39 (Italy) calibrated detectors were

secured to the bottom of a plastic vessel and suspended, from the room’s ceiling, 2 m from the floor and 1.5–2 m from the

walls of the room [3]. The number of 

α

-particle tracks from the surface of the CR-39 detector was counted visually from a

monitor screen connected through a TV camera with an optical microscope [3, 4].

Prior to the investigations, control measurements were performed of the radon level by the RRA-01M, PRM-145,

and CR-39 instruments in a closed cellar room to check the accuracy of the indication of the radon meters. The difference in

the indications of these instruments was 30–50% with average radon level 450 Bq/m

3

.

The radioactive wastes from spent deposits of the Yangiabad and Krasnogorsk ore fields, about 50 km

2

in area and

5·10

5

and 7.7·10

5

m

3

in volume, respectively, are located in Tashkent oblast. The radon level on the grounds of the wastes

was measured with the RRA-01M and PRM-145 instruments. The interval of the variation of the volume activity of radon on

the territory of both waste sites in the morning under windless conditions was 30–60 Bq/m

3

with background 

≤

10 Bq/m

3

at

distances 70–80 cm from the surface of the ground. The equivalent dose rate of the 

γ

-radiation within the contaminated areas

was 0.6–2.0 

μ

Sv/h, rarely to 150 

μ

Sv/h.

The Pap region of the Namangan Oblast contains radioactive wastes from the development of the uranium deposits

in Chorkesar. The radioactive materials are placed in dumps covered with neutral soil. In some places atmospheric precip-

itation has destroyed the cover. The water is seeping out of the temporarily closed shafts. The equivalent dose rate of the

γ

-radiation on the surface of the wastes is 3–4.5 

μ

Sv/h, and the volume activity of the radon on the grounds of the ore deposit

reaches 70–100 Bq/m

3

during the morning under windless conditions.

The volume activity of radon was measured in homes constructed from fired and unfired brick, administrative build-

ings, hospitals, children’s, and other institutions during the winter and summer. As Table 1 shows, the volume activity in

homes in Yangiabad which were built from fired brick the volume activity of radon does not exceed 37 Bq/m

3

in the summer

and 162 Bq/m

3

in the winter; in homes built from unfired brick (local clay) it activity is 50–90% higher and equal to 75 and

260 Bq/m

3

, respectively [4]. In rooms of the administrative buildings, schools, nursery school, and hospital it is the range of

the admissible concentration 45–200 Bq/m

3

(the maximum admissible concentration (MAC) is 200 Bq/m

3

). The exceptions

are the dump rooms, where the radon volume activity varied in the first room from 700 Bq/m

3

during the summer up to

1000 Bq/m

3

during the winter and from 1100 to 1700 Bq/m

3

, respectively, in the second room. The measurement of the radon

yield from the wall and floor surfaces of the rooms performed with a CR-39 detector showed that its source is the soil on

Room

Yangiabad

Krasnogorsk

Chorkesar

Summer

Winter

Summer

Winter

Summer

Winter

Brick house:

fired brick

37–78

45–160

35–75

42–160

68–210

96–350

unfired brick

75–130

85–260

64–126

64–230

95–330

150–590

Administrative buildings

66–88

98–140

42–110

67–150

50–83

78–160

School

70–110

80–150

34–120

67–190

41–83

64–150

Nursery school

60–85

50–90

40–70

65–110

83–140

120–210

Hospital

45–75

56–90

44–58

55–110

190–240

260–400

Polyclinic

88–150

120–220

32–52

48–78

120–210

150–290

Dump

700–1100

1000–1700

Pharmacy

230

410

334

TABLE 1. Radon Concentration in the Rooms in Winter and Summer, Bq/m

3