NUCLEAR DATA SHEET


I. Units of Radioactivity
II. Sources of Radiation
III. Acute Dose Effects
IV. Recommended Limits
V. Long Term Effects
VI. Neutron Cross Sections
VII. Comparative Energy Figures
VIII. Waste Products for 1,000 MW Electric Plant Per Year

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I. UNITS OF RADIOACTIVITY:

Activity: Curie (Ci) = 3.7 x 1010 dis/sec (activity of 1 gm of Ra226 )

MKS: Becquerel (Bq) = 1 dis/sec = 27 pCi

 

Exposure: Roentgen (R) = (1/3) x 10-9 Coul created per cc of air at STP

MKS: no name = 1 Coul/kg = 3876 R

 

Absorbed dose: Rad = .01 J/kg (generally, one R of exposure will give one rad)

MKS: Gray (Gy) = 100 rads of absorbed dose

 

Dose equivalent: Rem = rad * RBE where RBE depends on radiation:

MKS: Seivert (Sv) = 100 rems

TYPE

RBE

x-ray, gamma ray

1

Beta

1-2

Slow neutron

4-5

Fast neutron

10

Proton

10

Alpha

10-20

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II. SOURCES OF RADIATION:

Background: about 200 mrem/year, or about 2 mGy/year, but depends on location:

California (minimum) = 115 mrem/year

Colorado (maximum) = 250 mrem/year

due to: cosmic rays - higher elevation means higher dose rate

ground - depends on type of rocks and dirt

internal - from naturally occuring radioactive isotopes such as K40 ,C14 , and others [there are 260 grams of K, or 31 mg of K40 in a 75 kg person which gives an activity = 0.217 mCi = 8,000 Bq; 18% of body weight is carbon, or 1.7x10-14 gms of C14 in a 75 kg person which gives an activity =.078 mCi = 2,900 Bq.]

Other sources (in addition to background): in mrem

1 chest x-ray: 40

1 gastro-intestinal track x-ray 210

1 NY-LA flight at 35,000 ft: 2

one year living next to nuclear plant 1

living one year in median home (.9 pCi/l) 180

(mainly due to Rn gas trapped in home)

(Rn levels measured in pCi/liter or WL: 1 pCi/l = .005 WL = 200 mrem/yr)

(EPA rec. max = 4 pCi/l = 800 mrem/yr)

(1% of all houses have > 10 pCi/l = 2000 mrem/yr)

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III. ACUTE DOSE EFFECTS: (dose obtained within a few weeks)

20,000 mrems: measureable transient blood changes

150,000 mrems: acute radiation sickness

200,000 mrems: death in some people

350,000 mrems: death in 50% of people;

(LD 50/60 = lethal dose that kills 50% within 60 days is between 4-6 Gy)

localized (not whole-body doses) for cancer treatment: 10,000,000 mrems

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IV. RECOMMENDED LIMITS:
500 mrems/year for general population
5,000 mrems/year for special occupations

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V. LONG TERM EFFECTS - LINEAR HYPOTHESIS vs HORMESIS HYPOTHESIS:
(Neither has been proven at low doses, but recent research supports hormesis for levels several times the normal average background amount.)

At the cellular level, a dose of 1 mGy of ionizing radiation gives 1 "hit" on a cell. (So the background radiation gives about 2 hits per year to each cell.) A "hit" on a cell can cause DNA damage that leads to cancer later in life. There are other causes of DNA damage, a relatively large amount from normal chemical reactions in metabolism. There are four other responses by cells to "hits". 1. The body may be stimulated to produce de-toxifying agents, reducing the damage done by the chemical reactions of metabolism. 2. The body may be stimulated to initiate damage repair mechanisms. 3. The cells may kill themselves (and remove the cancer risk) by a process called apoptosis, or programmed cell death (a regular process that happens when the cell determines that things are not right). 4. The body may be stimulated to provide an immune response that entails actively searching for defective cells - whether the damage was done by the radiation or by other means.

linear: According to the latest BEIR report, there is a .79% chance of a latent cancer death for every 10,000 mrems of acute dose. (There is an 18.33% chance of contracting cancer for all other causes.) This is based on the idea that a single hit could cause a cell to become cancerous. It does not recognize the four protective responses referred to above.

hormesis: None is a little bad, a little is good, a lot is a lot bad; based on analogy with minerals (a little is necessary, a lot is toxic) and vaccines (a less dangerous infection builds up body defenses). This does include the above 4 protective responses.

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VI. NEUTRON CROSS SECTIONS:
in barns (1 barn = 10-28 m)

a) fissile materials

SLOW

SLOW

SLOW

FAST

FAST

Element

Absorption

Fission

Avg #/fission

Absorption

Fission

U233

47

531

2.487

.

.

U235

98

580

2.423

0

1.3

U238**

2.8

0.0005

.

2.0

0.5

Pu239

271

742

2.880

.

.

Pu241

368

1007

2.934

.

.

(** NOTE: U238 is NOT a fissile material; it is included only for reference.)

 

b) moderator and control rod materials:

Element

Absorption

Scatter

Avg # of collisions to thermalize

H

0.332

38

18

D

0.0005

7

25

He

0.0000

1

42

Li

71

1.4

62

Be

0.010

7

90

B

755

4

98

C

0.0037

4.8

114

N

1.9

10

132

O

0.0002

4.2

150

Cd

2450

7

.

 

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VII. COMPARATIVE ENERGY FIGURES:

Quantity

Joules

Amout to Power 1,000 MW Plant for one year = 9.5 x 1016 Joules

Radiation per 1,000 MW-year in person rems

1 gram of U235

8.2 x 1010

3.6 tons *

250

1 barrel of oil

6.3 x 109

15 million barrels

50

1 ton of coal

2.9 x 1010

3 million tons

400

1 ft3 natural gas

1.1 x 106

86 billion ft3

30

1 cord of white oak

3.1 x 1010

3 million cords **

?

Yearly U.S. sunlight

6 x 1022

40 square miles ***

?

Yearly U.S. wind

1 x 1020

.

?

Geothermal

.

.

200

1980 U.S. energy consumption (all forms) 1 x 1020 Joules = 100 quads

(1 x 1015 BTU's = 1 quad)

Notes:

* the 3.6 tons of U235 includes a factor of 1/3 due to incomplete use of fuel due to poisoning of rods. This much U235 demands 100 tons of enriched uranium which demands about 100,000 tons of uranium ore at .5% metal (a high but not the highest grade ore). If reprocessed, this much fuel will last roughly 5 times longer due in part to the creation of U235 by reactions inside the reactor.

** The 3 million cords would take 6 million acres of untended forests or 550,000 acres of tended forest. On a per-pound basis, all woods contain approximately the same energy. Untended hardwood forests generate 0.5 cords per acre per year, thus you would need 6 million acres to supply one power plant. Cultivated Southern forests generate 11 times more per acre per year, thus you would need about 550,000 acres for one power plant. [640 acres = 1 sq. mile, so need 860 sq. miles]

*** The 40 square miles comes from the yearly average of 200 Watts/m and assumes a 10% efficiency in converting sunlight into electricity & 50% spacing for maintenance.

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VIII. WASTE PRODUCTS FOR 1,000 MW ELECTRIC PLANT PER YEAR:

nuclear: 120 tons/year if not reprocessed (5 tons/year if reprocessed) + tailings

coal: 500,000 tons/year of solid wastes + tailings

+ 150,000 tons/year of sulfur dioxide

+ nitrogen oxides equivalent to 200,000 automobiles

+ chemical carcinogens released (e.g., arsenic, cadmium)

solar energy: to make solar collectors and the frames and all accompaning equipment requires 1,000 times the materials of an equivalent coal or nuclear plant.

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