The Nucleus and Nuclear Chemistry

Z : atomic number = # of proton A : mass number = proton + neutron

,Z=Z',AA' isotope

nuclidep. n. :nucleons nucleus

XAZ

XX AZA

Z'':

Neutron-proton ratio

Neutron-proton ratio and Nuclear stability

n/p=1 n/p>1 ~5:3

Z>83,Z>83(radioactive element)

pn np

Stable Nuclide

Z A-Z Stable Nuclide Examples Even Even 168Even Odd 57Odd Even 50Odd Odd 4

Magic number (Z): 2, 8, 20, 28, 50, 82 ,126He O Ca

Doubly magic 10 isotopes

PbU

PbTh PbU

SnHe

20782

23592

20682

23220682

23892

50

42

N B Li H

Na F

Ti C

O C

147

105

63

21

2311

199

4722

136

168

126

cosmic abundance and nuclear stability

Light elements are more abundant than heavy elementsEven atomic number are more abundant than odd atomic number

(H),86%mass number

Magic number 2, 8, 20, 28, 50, 82(126 neutron)He O Ca Pb(114 protons)

Shell model of the nucleus :p, n exist in levels (shells)Analogous to the shell structure of electron

particle stable nuclei2 protons2 neutrons

82 protons208-82=126 neutrons RaHeTh

ThHeU22688

42

23090

23490

42

23892

+

+

He42 {

Pb20882

Radioactivity

Excited state

Emissi-on

ECelectron capture

Antine-utrino

neutrino

neutron

Too smallproton

Too Smallpositron

Too largebeta

alphaHeRaRa 4222286

22688 +

epn 0111

10 + eNC

01

147

146 +

nep 1001

11 + AreK

4018

01

4019 +

enp 0110

11 + eMoTc

01

9542

9543 +

242

42

+He 83>e01

01

ZN

e0101

+

H1111

nn 10

00

00

ZN

ZN

00;h

decay ray

1~ 0.001nm wavelength 10-12m

X-ray

Wavelength > 1nm (lifetime~10-9s)

hXX AZAZ +

* 009943

9943 + TcTcm

Excited

state

Ground

statem: metastable

XE AZ 1

2E

1

2

3 1

2

3

*42 X

Az

XAz42

E1-E2=1+2+3=2+3=3

Excitedstate

Groundstate

eXeI

PaTh

ePaTh

XX AZAZ

01

13154

13153

01

23191

23190

01

23491

23490

011

+

+

+

+

+

3Mev =>

- 0.5mmAl 0.015mmAl

(1)Electron emission

neutron proton +e-

Emitted along a continuous spectrum of energies

0max ( nucleide )

ray

, antineutrinoparticle()

neutral: massless particle

Antineutrino

Neutrino

0101

( )QE AZ1

E2

11 +

22 +

33 +

44 +

1

2

3

4

5

6

QAZ 1+

decay(electron emission,positron emission, electron capture)

Ray ,5~11cmAl 1~10MeVray100excited state lifetimensecnanosecisomeriosmeric transition

decay z > 83 A > 200 (nuclide)

that is too heavy

4 242

42 + XX

AZ

AZ

single energy or one of a few specific energy

existence of energy level within the

nucleus

,(1-10MeV )

10-3 mmAl

)(4222688

23090

42

22888

23290

HeRaTh

RaTh

+

+ particle -ray particle +2 change

D

8 1 g D 2500

T :Radioactive t1/2 =12.3 year

n+Li

MeVHeTslownLi

slownHeTfastnLi

8.4)(

)()(42

31

10

63

10

42

31

10

73

+++

+++

Shieldheat exchange

Magnet shieldblanket plasma

Li+ n + T

( )H21

( )H31

() ()60Co5.26222Rn()30.82

=A= N ) : N )

:1n (Nt /N0) = - t 1/2 = 0.693/

(C-14) C-14

14N 14C

14C/12C 1/101 2 14C

14C573014C15.3 disintegration/min . g

14

Counter

Resistance

high voltage

Argon gas

m

window

particle

HeLiBn

ArAr42

73

105

10

(g)particleenergyhigh

(g)

++

+ + e

Ar, gas

n BE3 added

Geiger counter

Geiger counter

HeLiBn

ArAr42

73

105

10

(g)particleenergyhigh

(g)

++

+ + e

Scintillation counter

photocathode photomultiplier tube

photocathode

photoelectric-sensitive surface

window

,, rays

Phosphor

NaIElectron Beam

ZnS

NaI + ThI

Nuclear Binding Energy

E = mc2

1.6x1014 g/cm3

(nucleus) 10-13 cm (atom)10-8 cm

Coulomb force = k (q1.q2) / r 2

nuclear force 30~40 x coulomb force() a distance of about 10-13 cm

Binding Energy per Nucleon

MeVCaMeVOMeVHe 55.8:00.8:14.7: 4020168

42

Nuclear Binding Energy

mass of atom 1 joule=1 kg m2/sec2

Difference in mass 1 amu=1.6605655 x 10-27 kg = 931.5017 MeV

39.96259 amu n: 1.008665 amup: 1.007825 amu.

++ + npe

Ca4020

Nuclear Binding Energy

m =39.96259 (20x1.008665) ( 20x1.007825)=0.36721 amu

E =0.36721 x1.6605655 x (2.9979 x108 m/sec)2x10-27

=5.4804 x 10-11 J = 342.06 MeV

1 MeV = 1.6021892 x 10-13 J

1 amu = 931.5017 Me VBinding Energy per nucleon:

40~100 (Fe ,Co ,Ni) -> Highest Binding E/ nucleon

nucleonMeV5515.84006.342

Nuclear Binding Energy

(8x1.67493 x 10-24 )+(8 x1.67262 x10-24 g) =2.67804x10-23 g

2.65535x10-23 g

m = -2.269x10-25 g or -0.1366 g/mol ( x 6.02 x1023 )

E= mc2 =(-1.366 x 10-4 kg/mol )(3.00 x108 m/s)2

= -1.23 x 1013 J/mol= -2.04 x10-11 J/nucleus (1Mev =1.60 x10-13 J)= -1.28x102 MeV

pnO 1110

168 88: +

nuleon8.00MeV

16101.28 2 =

:168O

Nuclear Fission

1938 Discovered by Otto HalmFritz Strassman UBa,

nKrBa

nZrTeUn103

9136

2142

56%3~2

10

9740

13752

23592

10

++

++ +

nSrXe

enCeZr

nKbCs

10

9038

14354

01

10

14058

9440

10

9037

14455

3

62

2

++

+++

++

83

OU

enrichment over 200 isotopes35 different elementsU2.4

nBaKr 1014156

9236 2++

Nuclear Fission

236U 14090

Subcritical , enough n are lost UChain reaction

Critical , maintain a count of fissions ,U 2.4,

mass large enough 1U 1 n (effective)

Super critical , n multiplies # of fission

nMoBaCf 10106

42142

56252

98 4++

430(17%) 100(20%)

20 metric tons

Light water reactors

Control rod

Fuel

Coolant (water)

H2O (neutron moderator)

Light water::H2O coolant and moderator350 150atm

D2O graphite

1.Fuel

U3O8 enriched 235U 2~3%

235U 0.7%

Zr coating

3.Moderator

H2Ographite

U

Light water H2Oheavy water D2OGraphite C

2.Control System

B (Boron) or Cd

4273

10

105 LinB ++

Breeder Reactor238

U 235

U232Th 374.1C

500C

fast breeder ( liq. metal Na ) (881 o c )neutron need not be moderated

(heat conducting better)

nucleonfastUnU 2399210

238 +

EnergynproductfissionnPu

PuNp

NpU

++ +

+

+

10

10

23994

01

23994

23993

01

23993

min2423992

3~2

0123391

min2223390

10

23290 + + PaThnTh

0123392 +U

)(239 fatalpoisonousPu

27

PuU

Pu

Pu

U

Nuclear Fusion

73%26%1%

eHeHHe

H2HeHeHe

HeHH

eHHH

01

42

11

32

11

42

32

32

32

21

11

01

21

11

11

++

++

+

++

nHHH 1042

13

21 ++

( )()H21

:

:13cm

Sun :

(plasma)

()

=>

H21 13cm7( 107 K)

++ 0142

1011 24

7

HeH k

Nuclear Fusion

Atomic Bomb

,

(ICRU)(SI)

:1.(activity)

() (Bq) :

1(Bq)=1/60Co ()

2.(Absorbed dose) D

() (GrayGy)

1(Gy)=1/ rad= 10-2 /

//(mGy/h/(Gy/h)

3.(dose equivalent) HT

( n)

(Q)2.1(Sv)

H()=D()XQ

(mSv)(Sv) Q 235226

/(mSv/y)/(Sv/h)

4.(effective dose equivalent)HE

()()(WT)(HT)(WT)(HE) HE(Sv)(HE)2(mSv)(2.4mSv)

rad. (radiation absorbed dose)

amt of radiation that deposits 1x10-2J of energy 1 kg of tissue.

(1rad) (1rad)

RBE Relative Biological effectiveness

measure the relative biological damage caused by radiation.

US system: curies (Ci) 1Ci=3.71010dps()

SI unit : becquerel (Bq) 1Bq=1decomposition per sec. (dps)

Amount of energy (damage) in the radiation absorbed by living tissue

US : 1Rads (Radiation absorbed dose)=0.01J/kg Tissue

SI : 1Gray (Gy)=1J/kg of tissue

Amount of biological damage /quality factor : (penetrating ability)

- -radiation =1

p- n- (low energy) =5

p- n- (high-energy) =20 or -particles

Relative Biological Effect (RBE)Relative effectiveness of the radiation in causing damage

Biological effect of radiation

US : rem (roentgen equivalent man) = rads quality factor

SI : Sv (sievert) = Gray quality factor

Background radioactivity : 200mrem/year

millirem (mrem)

20

10

1X

2.1

ICRP-26(1977)

RBE 1 for dose ratetotal dose type of tissue 10 for H fast neutron=51. x-ray -ray . (ions)2. 5 slow neutron 20 heavy aton.

relate various kind of radiation in

terms of biological destruction.

rems (roentgen equilivant for man)

rems = rad x RBE

0.1-0.2 rem

background radiation

()

0-25 rem

25-50

100-200

500 30

1000 30 100%

X- ~20-40 millirem

0.5 rem 500 millirem

5 rem

40K 21mrem

0.3mrem

Radioactive

Falloni 4 mrem

air 5

earth (47)

cosmic ray 52% 100 mrem (50)

X- 43% 80 mrem (61)

U 2% 4

??? 3% 6

0.14% 0.3 mrem

TV 0.02% 0.04 mrem

Building 3 mrem

waterial

ray + H2OH2O++e-

H2O++H2OH3O++OH

OHradical free radical

One or more unpaired electron

Somatic damage :affects the organism

During its own lifetime burn ,cancer

Genetic damage :genetic effect

Genes chromosones

Bone marrow ,blood forming tissue

Lymph nodes

leukemia

SI unit becquerel 1 nuclear/disintegration/sec

Old curie 1g Ra -226 3.71010 disintegration/sec

5.0 millicurie Co=5.010-33.71010

=1.8108 disintegration/sec

ray damaged not limited to the skin penetrating

stop by skin

penetrate 1cm