Luis Neves / Alcides Pereira - OCW Usal

ocw.usal.es

Luis Neves / Alcides Pereira - OCW Usal

Luis Neves / Alcides Pereira

Laboratório de Radioactividade Natural

Departamento de Ciências da Terra

Universidade de Coimbra

www.dct.uc.pt/lrn


Summary

Basics (radioactivity, units, natural radioactive elements, decay

chains)

Exposure to ionizing radiation (biological effects; dose; dose

assessment).

The radon gas (basics; source and migration in rocks and soils;

average concentration in rocks, soils, water, building materials

indoor and outdoor; human health effects, legislation)


Summary (continuation)

Radon in Portugal and Europe (previous data)

The Laboratory of Natural Radioactivity (University of Coimbra)

Methods and techniques avaliable

Results

Geological and non-geological factors that control the indoor

radon in dwellings

Mitigation (risk maps and engineering solutions)


Ionizing radiation:

gama

Free electron

Ionized atom (ion)

Ionizing capacity

8 µ

alfa

γ – 70 ionizations

γ α – 23000 “ “

alpha

beta

gamma

Desintegration of an

atom with releasing

of energy as

radiation

properties

Paper

Aluminum foil

Concrete or lead

gama

beta

– Bq (Becquerel) – desintegration of an atom in

each seconddo (Bq/l; Bq/m-3 /Bq.kg-1 Units

)

- Sv (Sievert) – estimates biological effects

(dose)


Main radioactive natural elements

2.8 %

Average crustal concentration (Taylor e McLennan, 1985)

10.7 ppm

2.8 ppm


Decay chains

Potassium

Thorium

Uranium

238 U

235 U

40 K

232 Th


206 Pb

210 Po

210 Bi

210 Pb

214 Po

214 Bi

214 Pb

218 Po

211 Po

207 Pb

211 Bi

211 Pb

215 Po

219 Rn

222 Rn

207 Tl

212 Po

226 Ra

208 Pb

212 Bi

212 Pb

216 Po

220 Rn

224 Ra

223 Ra

208 Tl

230 Th

228Th

227 Th

234 U

Decay chains

Type of radiation

228 Ac

231Pa

234 Pa

alpha

beta

40 Ar

40 Ca

228 Ra

231 Th

234 Th

+ gamma

40 K

232 Th

235 U

238 U


Ingestion

Rocks

Food / water

External exposure

Extraterrestrial

Air

Inhalation

Internal exposure


Direct effects

Indirect effects

Biological effects from exposure to ionizing radiation

Breaks in DNA chain

Growing of oxidizing molecules

(OH - e H + ).

a) b)

Damage induced by alpha radiation in: a) lung tissue; b) geological materials


Biological effects from exposure to ionizing radiation

Adapt. of Bettencourt (1998)

Main organizations in the field of radioprotection

Deterministic effects

- Only in high doses;

- Individual dose-response .

Sv


Natural and artificial sources of ionizing radiation

Thermoelectric

power plants

Nuclear

power plants

Nuclear

accidents

Military tests

(atmosphere)

Artificial sources, excluding medicine

Total annual average: ca. 0,015 mSv (UNSCEAR,

2000)


Radon

Internal

radiation

External

radiation

Cosmic

radiation

Artificial

sources

Medicine

Natural and artificial sources of ionizing radiation

0 0,2 0,4 0,6 0,8 1 1,2

mSv

Average annual dose : 2,7 mSv (UNSCEAR, 2000)

40%

15%

45%

Radon Other natural soureces Artificial / medical sources


238 U

234 Th

234 Pa

234 U

230 Th

226 Ra

222 Rn

218 Po

214 Pb

214 Bi

Radon gas

Source and properties

Alpha decay

Beta decay

214 Po

210 Pb

210 Bi

210 Po

206 Pb

222 Rn – radon (3,8d) –– 238 U

220 Rn – thoron (55s) –– 232 Th

219 Rn – akton (4s) –– 235 U

Isótope Half-life

238 U 4,5 x 10 9 a

234 Th 24,1 d

234 Pa 1,2 m

234 U 2,5 x 10 5 a

230 Th 7,7 x 10 3 a

226 Ra 1600 a

222 Rn 3,82 d

218 Po 3 m

214 Pb 27 m

214 Bi 20 m

214 Po 164 µs

210 Pb 22 a

210 Bi 5 d

210 Po 138 d

206 Pb estável


Schists

and

graywackes

Granite

Zircon

Thin section

Biotite

U content

(ppm)

Apatite

U distribution

Fission track analysis

226

Ra

238

U


238

U

222

Rn

226

Ra

222

Rn

218

Po

214

Pb

Mineral

222

Rn

222 Rn

226 Ra

Water

Main geological factors: U content, mineralogical support and permeability

226

Ra

Air

214

Bi

214

Po

206

Pb

Permeability


Pipe

Cracks

Pipe


Water Soils

Air

(Indoor)

Open air

37

370

3700

37000

370000

3700000

37000000

Radon (Bq.m -3 )

Source: USGS


Cracks

85 - 90%

Water

< 1%

Ra-226 in soil

Emanation

2 - 5%

Diffusion

1 - 4%


Radon

Radon


4 days

3 min

27 min

20 min

0.2 msec

5 days

138 days

Stable

218 Po e 214 Po expose

the lungs to a high

dose of radiation

Radon

progeny


What happens when radon

progeny reach the lungs?


Negative effect

Dose-Response model

Non-threshold theory

Dose (mSv)


Epidemiological studies

New Jersey, Missouri I, Canada, Iowa,

Missouri II, a combined study from

Connecticut, Utah and S. Idaho

Shenyang, China, Stockholm, Sweden,

Swedish nationwide, Winnipeg, Canada,

S. Finland, Finnish nationwide, SW

England, W. Germany, Sweden, Czech

Republic, Italy-Trento, Spain, Austria,

France, China - Gansu Province, E.

Germany


Odds Ratio

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

Risk estimation

(different models)

WLM20

1st Story

BR

BR/LR

LR

Basement

20-39% 40-59% 60-79% 80+%


Cancer deths (USA-2005)

20000

18000

16000

14000

12000

10000

8000

6000

4000

2000

0

Lung (radon)

Liver

Brain

Stomach

Skin

Mouth

Leukemia

Bones


Lung

cancer

Inhalation

Radon gas

Radon progeny

Recent studies show that radon in homes is responsible for about 20 000 lung

cancer deaths in the European Union each year and a similar number in the

United States (Darby et al., 2005; Field et al., 2006). This is about 9% of the total

lung cancer deaths and about 2% of cancer deaths overall.

So, since the Chernobyl accident about 800 000 europeans and americans could

have died because of radon.


a) Indoor radon in dwellings.

País

Old houses New

houses

United States, Luxembourg 150 150

United Kingdom, Ireland,

Denmark, Belgium; Canada

Finland, Norway, Sweden,

Czech Republic, Slovenia,

Greece, Austria, (E.U.)

200 200

400 200

Switzerland 400/1000 400/1000

Germany 250/1000 250

Values em Bq.m -3 (Akerblom, 1999).

Legislation

b) Radon in water

Recomendation 2001/928/Euratom: 1000 Bq.l -1

c) Total dose

Directive 96/29/Euratom (workplaces with

manipulation of radioactive substances):

Workers - 20 mSv/year;

Members of the public - 1 mSv/year.

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