222Rn, daughters

Jonassen, N., Tlie Effect of Electric Fields on 222Rn Daughter Products in Indoor Air, Health Phys., 45, (2), pp. 487-491,... 

Fig. 1.5. Mobility distribution of 222Rn daughters. I, in open air (Wilkening et al., 1966) II, in laboratory (Jonassen Hayes, 1972).

Jacobi W. 1972. Relations between the inhaled potential alpha-energy of 222Rn- and 222Rn-daughters and the absorbed alpha-energy in the bronchial and pulmonary region. Health Phys 23 3-11. 

Nero, A.V., Indoor Radiation Exposures from 222Rn and its Daughters A view of the Issue, Health Physics, 45 273-288 (1983). 

Let us consider an atmosphere where the (activity) concentrations of radon, 222Rn, and its three short-lived daughters, 218Po, 21ifPb and 21I+Bi, are CQ, Ci, C2 and C3, the decay constants and unattached fractions of the daughter products, X, X2, X3, fi, f2 and f3 respectively, and E and E" the energies of the alpha particles from 2 8Po and 21I+Po (the fourth short(est)-lived radon daughter). 

Chakravatti, J.L., Control of 222Rn-WL in New Construction at Elliot Lake, presented at Workshop on Radon and Radon Daughters in Urban Communities Associated with Uranium Mining and Processing, Bancroft, Ontario, Atomic Energy Control Board of Canada, AECB-1164 (1979). 

The concentration of radon in air was computed from the a-count by assuming that 3.8-day 222Rn and its short-lived daughters—2.0 min. 

Monthly average 222Rn concentrations in air during 1959-1966, measured daily at 8 30 a.m. by counting a-particles emitted by the short lived 214Po daughter in 24-hour samples of airborne particles, showed an annual maximum in August-October and minimum in February-April. 

At long times, the ratio of daughter to parent activity becomes constant, and both species disappear with the effective half-life of the parent. The classic examples of this decay equilibrium are the decay of 140Ba (ti/2 = 12.8 d) to 140La (ti/2 = 40 h) or the equilibrium between 222Rn Of/2 = 3.8 d) and its short-lived decay products. 

Example Problem Consider the decay of a 1 p,Ci sample of pure 222Rn (t /2 = 3.82 d). Use the Bateman equations to estimate the activity of its daughters (218Po, 214Pb, 214Bi, and 214Po) after a decay time of 4 h. 

The uranium series contains two radionuclides of special interest, 226Ra (ti/2 = 1600 y) and its daughter, 38 d 222Rn. 226Ra (and its daughters) are responsible for a major fraction of the radiation dose received from internal radioactivity. Radium is present in rocks and soils, and as a consequence in water, food, and human tissue. The high specific activity and gaseous decay products of radium also make it difficult to handle in the laboratory. 

If 222Rn is initially purified from its daughters, how long does it take for them to grow back to 50% of their values at secular equilibrium ... 

Airborne contamination is another possible contribution to the blank correction. Here one is chiefly concerned with sample contamination with the daughters of 222Rn, which have half-lives in the 30- to 40-min range. Steps that can be taken to avoid this problem include eschewing the use of suction filtration in chemical procedures, prefiltering of room air, and use of radon traps. 

The gases radon (222Rn) and thoron (220Rn) are formed as progeny of uranium and thorium in rocks and soil. They are emitted from the ground into the atmosphere, where they decay and form daughter products, isotopes of polonium, bismuth and lead, which either remain airborne till they decay, or are deposited in rain and by diffusion to the ground. 

In filtered air, N is zero, n = (qla) and the mean life before neutralisation is (aq)K Using (1.14), and taking a = 1.6 x 10-12 m3 s 1, the mean life before neutralisation by ions formed by 222Rn and daughters, is about 1400 Xos. This provides a test of whether the decay products... 

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