32

RADIOACTIVITY AND RADIATION PROTECTION

Unit of act ivi ty = Curie: t Ci = 3 ,7Xt0 t0 d i s i n t e g r a t i o n s / s e c

Unit of exposure dose for x and y radiation = Roentgen: I R = I esu/cm 3 = 87.8 erg/g (5.49×107 MeVyg ) of air

Unit of absorbed dose = rad: 1 rad = t00 e r g / g (6 .25Xt0 7 MeV/g) in any ma te r i a l

Unit of dose equivalent (for protection) = rem: reins (Roentgen equivalents for man) = rads X OF,

where QF (quality factor) depends upon the type of radiation and other factors. For ¥ rays and HE protons, QF = i; for thermal neutrons, QF = 3; for fast neutrons, QF ranges up to 10; and for a particles and heavy ions, QF ranges up to 20.

Maximum p e r m i s s i b l e occupational dose for the whole body: 5 r e m / y e a r (or ~ t00 mi l l i r em/week)

Fluxes (per cm2) to l ibera te iR in carbon: 3X i07 m i n i m u m ionizing singly charged pa r t i c l es 0.9X i09 protons of t MeV energy

(These fluxes are correct to within a factor of 2 for all materials. )

Natural background: i20 to t30 m i l l i r e m / y e a r ,,~ cosmic radiation (charged particles + neut .... ) ~25~ cosmic radia t ion (y rays) ~ 25 } radiation from rocks and air (y rays) ~ 73~

Cosmic ray background in counters: ~ I/min/cm2/ster

PERIODIC TABLE OF THE ELEMENTS

IA I I A

3 4 Li Be

6.94 9.0122

11 12 Na Mg

22.9898 24.305

19 20 K Ca

39.102 40.08

37 38 Rb Sr

85.47 87.62

55 56 Cs Ba

132.905 : 137.34

1 H

1.008

I I IB I V B V B V I B V I I B : - - VIII - - - - ~ IB l i B

22 Ti

47.90

40 Zr

91.22

72 Hf

178.49

21 Sc

44.956

39 Y

88.906

57-71 Rare

Earths

23 V

50.941

41 Nb

92.906

73 Ta

180.947

24 Cr

51.996

42 Me

95.94

74 W

183.85

25 Mn

54.9380

43 Tc

98.9062

75 Re

186.2

26 Fe

55.847

44 Ru

101.07 J

76 Os

i 90.2

27 Co

58.9332

45 Rh

102.905

77 Ir

192.2

28 Ni

58.71

46 Pd

106.4

78 Pt

195.09

29 Cu

63.55

47

79 Au

196.967

30 Zn

65.37

48 Cd

112.40

80 Hg

200.59

I l i A IVA VA VIA VIIA

5 B

10.81

26.981 .~

31 Ga

69.72

49 In

1 ! 4.82

81 Tl

204.37

6 C

12.011

14 Si

28.086

32 Ge

72.59

50 Sn

118.69

82 Pb

207.2

7 N

14.0067

15 P

30.9738

33 As

74.9216

51 Sb

1121.75

83 Bi

208.981

8 O

15.9994

16 S

32.06

34 Se

78.96

52 Te

127.60

84 Po

(209)

9 F

! 8 .9984

17 CI

35.453

35 Br

79.904

53 I

126.9045

85 At

(210)

2 He

4.0026

l0 Ne

20.17

18 A

39.948

36 Kr

83.80

54 Xe

131.30

86 Rn

(222)

I i ~ [ 58 ' 59 I N ~ 61 [ 62 I 63 I G6~ I 65 I 66 [16~7930 68 I 69 I 70 [ 71 [ Ce Pr Pm Sm Eu Tb Dy He Er Tm Yb Lu 150.4 158.925 162.50 167.26 168.934 173.04 174.97 138.91 140.12 140.9~ 144.24 (145) 151.96 157.25

Rare earths (Lanthanide

series)

I " 90 , ,2 ,, f 01021 [ Ac Tb Pa U I Np Pu Am Cm Bk Cf Es Fm Md No Actinide series (227) 232.038 231.036 238.03 1237.048 (244) (243) (247) (247) (251) (254) (257) (256) (254) (260)

Numbers in parentheses are mass numbers of most stable isotope of that element. Adapted from the Handbook o f Chemistry and Physics, 1973-74. (Particle Data Group update, April 1974.)