In his most recent video, Arnie Gundersen calmly, but inaccurately, explains why people should remain fearful of extremely low levels of radiation and radioactive materials. He sounds so knowledgeable and is so often quoted by people who are adamantly opposed to the use of nuclear energy that it is worth a little time to point out the flaws in his logic, math and knowledge level and to demonstrate why his overall conclusions are thus completely wrong.
The first point to make is one that might be explained by Mr. Gundersen as simply a verbal “typo” in which he really knows the answer but misspoke. When describing his theory about how radioactive sulfur found on the US west coast was produced in Japan, he said that it came from neutron activation of the sodium found in salt water (minute 1:56).
It is not possible to form radioactive sulfur, which has an atomic number of 16, by hitting the nucleus of sodium, which has an atomic number of 11, with neutrons. It is possible to form radioactive sulfur through neutron bombardment and proton emission from chlorine, which has an atomic number of 17. The reaction is commonly referred to as an n, p activation.
Since salt is NaCl, it can be the source of radioactive sulfur if hit with neutrons. Nuclear alchemy works, but conservation of atomic particles prevents leaping up from one location on the periodic table to another some distance away.
Aside: I know I am occasionally guilty of making similar verbal errors in casual conversation and perhaps even on my recorded podcasts, so I am generally grateful when someone points them out. Just last night I said James Island, the name of a place where I lived a long time ago, when I was talking about spending some time on the James River which runs through my new hometown. End Aside.
Gundersen also asserts that the formation of radioactive sulfur supports his contention that there were occasions long after the initial plant shutdowns when the cores experienced continuing chain reactions and ongoing criticalities (minue 3:10). In his best Dr. Evil imitation voice, Gundersen says that researchers have calculated that the amount formed would have required 400 BILLION (minute 2:10) neutrons per square meter. He tells his viewers that is an enormous number of neutrons (minute 2:20). Here is a different view that a nuclear professional posted on a private email list to which I subscribe:
Four hundred billion neutrons per square meter? That’s trivial!
The peak thermal neutron flux in a CANDU reactor at full power is 1.0 E14 neutrons per square centimeter per second. The current of thermal neutrons flowing out of the core to the reflector is (crudely) one percent of this, or 1.0 E12 neutrons per square centimeter per second.
This flow amounts to 1.0E16 neutrons per square meter per second. But don’t worry – they are all absorbed or they decay (free neutron mean lifetime is 885 seconds).
Four hundred billion neutrons? This number is less than one billionth the number of neutrons that leak out of an operating power reactor every day.
When they are absorbed, these neutrons can, of course, activate other materials. But I don’t judge this as an earth-shattering revelation.
If there had been any criticality events, the number of neutrons would have been far higher. What Gundersen apparently has forgotten from his nuclear engineering training is that there are several actinides formed in nuclear reactors that undergo spontaneous fissions and other nuclear decays. Those natural nuclear events provide a “source” level of neutrons long after chain reactions have been stopped. It is those source neutrons, by the way, that help make start-ups of formerly operated reactors much simpler than the initial start-up of a brand new core.
Gundersen also claims that the Nuclear Regulatory Commission implied that plutonium that was reported to have been detected in minute quantities about a kilometer from the plant came from inside the reactor cores, not from damage to spent fuel in the spent fuel pools. The reality is that the plutonium measurements were consistent with fallout from nuclear weapons detonations both at Hiroshima and Nagasaki and from the extensive atmospheric weapons testing programs carried out by the five nuclear weapons states during the 1940s, 50s, 60s and into the 1970s.
I just noticed the time. My comments cover just the inaccuracies made in the first three minutes of an eleven minute video, so I am going to have to turn the rest of the analysis and error detection over to the critical readers and viewers here on Atomic Insights. Have fun.
Note: Some people misspell Mr. Gundersen’s name as Gunderson.