[ RadSafe ] Psychological Impacts of Chernobyl

[Bill Prestwich]

I don't claim to be an expert but the following are my thoughts.
Bill

	The following are estimates of probabilities of double hits to cells
in the body from natural radiation. They are based upon the Poisson
distribution which gives the probability for two events as N^2 exp(-N)/2. It
must be emphasized that a "hit" to a cell is itself a complexity of events.
These include ionizations, the rupture of chemical bonds and the production
of highly reactive free radicals.
	K40 in the body emits 4000 beta particles a second with mean energy
of 0.6 MeV. The range of the average beta particle in soft tissue is 2 mm.
Taking a diameter of 20 micrometers for a cell, the beta particle will leave
energy depositions in about 100 cells. This results in 2E10 cells in which
interactions occur in 12 h. For 1E13 cells the expected number of hits per
cell is then 2E-3. The probability for double hits is 2E-6, so from K40
there would be 20 million cells receiving 2 hits in 12 hours. Note that the
energy deposited in a cell from a hit is 6 keV, sufficient to rupture one
thousand bonds.
	From the sea level average muon fluence rate it is estimated that 20
muons per second pass through the body. The average muon energy is 4 GeV and
the range in soft tissue is about 20 m. Hence the muon completely traverses
the body.  A rough estimate of the average chord length in the body is 40 cm
giving 2E4 cells traversed by the muon. This leads to about 2E10 cells
traversed in 12 h, so the hit probability from muons would also be 2E-3. The
probability of two hits in 12 hours would again be 2E-6.
	Of course these isolated examples fail to take into account a beta-
muon combination giving two hits. These could be included by using N=4E-3.
These two examples only represent a small fraction of the million radiation
energy depositions per second from natural radiation. To get a very rough
estimate assume 10 cells are traversed in each event. This leads to N=0.04
and a probability for 2 hits in 12 hours of 8E-4, corresponding to 8 billion
cells.
	The above only involves rough estimates it is true. It also ignores
the large number of DSBs which arise from other sources. For these cells,
only a single radiation interaction would be necessary to produce the same
effect 12 hours after the non-radiative DSB. Moreover for high LET radiation
such as alpha particles the damage is usually complex and very difficult to
repair. In this case only one hit would be necessary to produce irreparable
damage in a normal cell. 
	Based on these considerations together with the fact that misrepair
is at least as deleterious as no repair, I think the scenario of consecutive
decays is not significant.
	Finally, in the case of consecutive beta decays, as has been
mentioned, the chemical properties of the daughter differ from the parent.
It is hard to understand how the chemical bonding could accommodate the
daughter element at the incorporated site.


-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu
[mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Richard Gallego
Sent: Thursday, April 28, 2011 8:38 PM
To: 'The International Radiation Protection (Health Physics) MailingList';
'The International Radiation Protection (Health Physics) Mailing List'
Subject: Re: [ RadSafe ] Psychological Impacts of Chernobyl

Steve,

I believe it is a useful exercise to have Mr. Busby's claims debunked by
experts in the field. If not us, then who? I'm afraid that if we fail to
respond, the uninformed might believe what he has to say. If nothing else is
accomplished, most of us now know what his views are and the arguments
against them.



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