vÁlaszd a tudÁst juniorfft.szie.hu/fizika/meroerz/1516/sensorphysics/dozimetry.pdffizika 14...

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Nuclear measurements

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Radioactivity

Dr. Seres István [email protected]

Helium nucleus:

2 proton + 2 neutron

neutrons protons of umerlntotanumber mass -A 4A

protons ofnumber number atomic - Z2ZHe

4

2He

Components of the nucleus:

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Radioactivity


Components of the nucleus:

Isotopes: same atomic number, dfferent mass number

Eg. hydrogen isotopes: - normal hydrogen isotope

- deuterium

- tricium 3

1

2

1

1

1

H

H

H

12

6CEg. carbon: stabil isotope, radioactive isotope14

6C

235

92UEg. uranium: , radioactive isotopes238

92U

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Radioactivity


Helium nucleus (a particle):

2 protons + 2 neutrons

Mass - defects:

ma = 6,6447·10-27 kg,

mp = 1,6727·10-27 kg,

mn = 1,6749·10-27 kg,

Nuclear binding energy

)m2m2(mm np a

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Radioactivity


Mass-defect:

)m2m2(mm np a

Einstein principle on matter and energy:

Binding energy:

e = mc2 = -5·10-29·(3·108)2

e = 4,5·10-12 J = 2,8·107 eV = 28 MeV·

(1 eV = 1,6·10-19 J)

The mass is converted to energy

= -5·10-29 kg

Nuclear binding energy

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Radioactivity


Nuclear physics

Nuclear binding energy:

2

npX

2 c)m)ZA(mZ(mcm e

A

ZX

Specific binding energy :A

e

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Radioactivity


Nuclear physics

A

e Radioactive decay, fissionfusio

n

Spe

cific

bin

din

g e

nerg

y (

MeV

)Mass number (A)

-1

-2

-3

-4

-5

-6

-7

-8

-9

0 20 40 60 80 100 120 140 160 180 200 220 240

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Radioactivity


Radioactive decay

N~dt

dN

T

t

0 2N)t(N

Law of radioactivityN

N0

N0/2

T 2T

N0/4T – half period

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Radioactivity


Radioactivity

•Radiocarbon dating

(C14)

Examination of metabolism of plants, animals

http://c14.arch.ox.ac.uk/calibration.php

Pharaos, Shroud of Turin

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Radioactivity


Activity

Number of radioactive decay per seconds.

SI Unit Bq (Becquerel).

s

decayBq

NT

2lnA

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Radioactivity


Dozimetry

Absorbed dose: (D)

(the absorbed radiative energy by a unit

mass)

SI unit Gray =J/kg

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Radioactivity


alfa radiation (helium nucleus)

beta radiation

(electron / pozitron)

gamma radiation

(elektromagnetic)

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Radioactivity


Dozimetry

Dose equivalent (biological dose)

H=D·RBE, where RBE= radiobiological equivalent

SI unit: Sievert

Type and Energy Range Radiation Weighting Factors

X and Gamma rays 1

Electrons 1

Neutrons (energy dependent) 5-20

Protons 5

Alpha Particles 20

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Radioactivity


Dozimetry Background radiation

The average natural background radiation:1.8 mSv/year

+ artificial effect – medical treatment, X-ray, etc. Are the

dominant: 0.4 mSv/year,

together maximum ~ 2,5 mSv/year.

The main components of the natural background radiation :

• radon (~ 0.5 mSv/year),

• radiation of the buildings (~ 0.4 mSv/year),

• cosmic radiation (~ 0.3 mSv/year),

• Kalium 40 isotopes of the body (~ 0.2 mSv/year)

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Radioactivity



Source: Nupex.eu

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Radioactivity



For the professionals (doctors, researchers, etc.) the limit

is e.g. 25 times higher (maximum 50 mSv/year). This is

the dose - limit.

For the population this limit is 2x the background, such

as max. 5 mSv/year

Lethal dose: LD 50/30 ~ 4,5 Sv

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Radioactivity


Dozimetry

Radiation from

radon

USA 37 Bq/m3

Finland 90 Bq/m3

France 62 Bq/m3

Indonesia 12 Bq/m3

Japan 29 Bq/m3

Hungary 55 Bq/m3

Germany 49 Bq/m3

Sveden 108 Bq/m3

Siria 20 Bq/m3

40 Bq/m3 ~ e.g. 1 mSv/year equvalent

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Radioactivity


Detecting the radioactivity

Cloud chamber

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Radioactivity



Cloud chamber:

visitor center, Nuclear power plant, Paks

http://www.tar.hu/fizfoto/fizfoto7.html

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Radioactivity


Filmdosimeter

(e.g. doctors)

www.sulinet.hu/.../Rab/0/11448/radioakt.htm

http://www.euronuclear.org/info/encyclopedia/f/filmdosimeter.htm


http://www.sulinet.hu/tart/ncikk/Rab/0/11448/radioakt.htm

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Radioactivity


Scintillation detektor

http://zope.reaktor.fh-furtwangen.de/portal/human_sciences/alchemie/portal/lectures/gesamttour/spektro/18.html


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Radioactivity


Geiger Müller counter

http://zope.reaktor.fh-furtwangen.de/portal/human_sciences/alchemie/portal/lectures/gesamttour/geiger/f3.html


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