What is the total activity of thorium 232 in the display with the nsn 1240 01 063 1351 Quizlet

The radioactive nuclei, or radionuclides, found naturally on Earth can be grouped into three series–headed by uranium-238, uranium-235, and thorium-232–plus several isolated beta-particle emitting nuclei, most prominently potassium-40 and rubidium-87. Average abundances of these nuclides are listed in Table 15-1.

Table 15-1. Half-lives and average abundances of natural radionuclides.

	40K	87Rb	232Th	238U
Half-life (billion years)	1.277	47.5	14.05	4.468

Upper continental crust
Elemental abundance (ppm)	28000	112	10.7	2.8
Activity (Bq/kg)	870	102	43	35
Activity (nCi/kg)	23	2.7	1.2	0.9
Activity (kCi/km3 )	66	8	3.3	2.6
Oceans
Elemental concentration (mg/liter)	399	0.12	1x10-7	0.0032
Activity (Bq/liter)	12	0.11	4x10-7	0.040
Activity (nCi/liter)	0.33	0.003	1x10-8	0.0011
Ocean sediments
Elemental abundance (ppm)	17000		5.0	1.0
Activity (Bq/kg)	500		20	12
Activity (nCi/kg)	14		0.5	0.3
Human body
Total activity (Bq)	4000	600	0.08	0.4*
Total activity (nCi)	100	16	0.002	0.01

* In the human body the activity of 210Pb and 210Po, both progeny of 238U, is much greater than that of 238U itself.

The most interesting of the series is the uranium-238 series which decays via a chain containing 8 alpha decays and 6 beta decays to lead-206. This chain includes the longest-lived isotopes of radium and radon: radium-226 and radon-222, respectively. In each of the three chains the parent nucleus has a much greater lifetime than does any of the progeny. Therefore, a steady-state is established in which, for a given sample of material, each member of the series has the same activity–aside from deviations due to differences in chemical properties, which cause different elements to be transferred at different rates into or out of a given sample of material.

Including all the succeeding decays, the total activity in the thorium-232 and uranium-238 series is, very roughly, ten times the activity indicated for thorium-232 and uranium-238 alone. Thus, for each of the series, the total activity in the Earth's crust averages roughly 30,000 Ci/km3. For both series together and including the contributions of potassium-40 and rubidium-87, the total activity in the crust averages about 100,000 Ci/km3. There is also a considerable amount of radioactivity in the oceans, with potassium-40 dominant in the ocean itself and thorium-232 relatively more important in the ocean sediments. For the oceans as a whole (1.4x1021 liters), the total activity is about 4x1011 Ci for potassium-40 and 1x109 Ci for uranium-238. Potassium-40 is also present in significant amounts in the human body, especially in muscle tissue.

In addition to these ancient radionuclides and their progeny, some radionuclides are being continually produced by cosmic rays. The most prominent of these is carbon-14, produced in the interaction of cosmic ray neutrons with nitrogen in the atmosphere.

Table 15-2. Average radiation doses in the United States, 1980-1982 (effective dose per year).*

		Effective dose
Radiation source	Comments	mSv/yr	mrem/yr
Natural sources
indoor radon	due to seepage of 222Rn from ground	2.0	200
radionuclides in body	primarily 40K and 238U progeny	0.39	39
terrestrial radiation	due to gamma-ray emitters in ground	0.28	28
cosmic rays	roughly doubles for 2000 m gain in elevation	0.27	27
cosmogenic	especially 14C	0.01	1
total (rounded)		3.0	300

Medical sources
Diagnostic x-rays	excludes dental examinations	0.39	39
Medical treatments	radionuclides used in diagnosis (only)	0.14	14
total		0.53	53

Other
consumer products	primarily drinking water, building materials	0.1	10
occupational	averaged over entire US population	0.01	1
nuclear fuel cycle	does not include potential reactor accidents	0.0005	0.05

TOTAL (rounded)		3.6	360

*From Ionizing Radiation Exposure of the Population of the United States, NCRP Report No. 93 (National Council on Radiation Protection and Measurements, Washington DC, 1987).

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Many forms of "radiation" are encountered in the natural environment and are produced by modern technology. Most of them have the potential for both beneficial and harmful effects. Even sunlight, the most essential radiation of all, can be harmful in excessive amounts. Most public attention is given to the category of radiation known as "ionizing radiation." This radiation can disrupt atoms, creating positive ions and negative electrons, and cause biological harm. Ionizing radiation includes x-rays, gamma rays, alpha particles, beta particles, neutrons, and the varieties of cosmic rays.