A Critical Assessment of Folklore

Bruce Heinmiller Dosimetry Services Chalk River Laboratories

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It ain’t so much the things we don’t know that get us into trouble. It’s the things we know that just ain’t so.

Artemus Ward (according to Thomas Gilovich in How We Know What Isn’t So) Variations in quote and attribution exist. There’s a take-home message here. What Folklore?

• K-40 dose mis-information widely propagated by nuclear energy proponents; putative doses compared to public doses from nuclear energy production • Mis-information widely propagated about source of, and shielding of, cosmic rays • And a few others Folklore-contaminated Items:

• Nuclear association “information” materials • University “information” websites • News articles/magazines; BBC, CBC, other TV • Journals; conference reports • Testimony at public hearings • Presentations/speeches • Reports from utilities and other corporations • List servers/blogs; posters; books … Why Give “Anti-nukes” a Pass?

• Too easy • Not very interesting • No accountability

• Quantitative claims are typically versions of the “Texas Sharpshooter” technique. A Few Quantities and Units Absorbed Dose, D = dε / dm J/kg (Gy)

Effective Dose = W T W R D T , R J/kg (Sv) T R

For this talk, Gy = Sv is good enough (except where I think it needs to be noted otherwise)

Activity = The expectation value of the number of nuclear transformations in a given quantity of material per unit time s-1 (Bq) (N λ in the case of N of a single ) NCRP Report No. 160: “ Exposure of the Population of the United States” (data 2006) Total = 6.2 mSv/y per capita (average)

Adult K-40 Activity

BNL study: K mass (g) =

= (5.52 – 0.014 A)

A = age (y); W = mass (kg); H = height (m)

ICRP-89: Men: 1.76 m; 73 kg Women: 1.63 m; 60 kg

For A = 40: (and using 31.7 Bq K-40 / g K) Men: 4160 Bq Women: 2730 Bq

Average: 3445 Bq Folklore from Distortion of Fact -- Fact Becomes Factoid Factoid: “Average adult *or even “person”+ contains 140 g *4440 Bq+ of .” Fact: Quoted datum is for Reference Man who is: young and male -- both attributes that are predictive of higher potassium content. Result: Factoid is in error by 29% (1000 Bq). Comparative Veracity of Two Popular Statements: Correct Not Correct The claim that an average adult [or person] contains 140 g of potassium Widely Propagated Folklore • Sleeping with someone results in a dose of 20 µSv/y [2 mrem/y] (from gamma rays emitted by the potassium in their body). • Stated explicitly or implicitly by comparison • Variations: 10, 30 and 40 µSv/y • Nuc. Reg. Com. : 1 µSv/y Spousal Irradiation – Debunking the Folklore Source/Target Geometry for Monte Carlo Modelling Reference Adult Whole-body Nominal Radionuclide Inventories (Bq)

Nuclide Male Female Average K-40 4160 2730 3445 C-14 a 3400 3320 3360 Rb-87 b 550 360 455 Others c 200 200 200 Total 8310 6610 7460

a Based on cosmogenic 200 Bq/kg C. Equilibrium largely restored from atmospheric weapons testing. Fossil fuel contribution to decreased C-14 isotopic abundance.

b Discrepancy in references. Probably correct.

c H-3, Be-7, U-series, Th-series, and others. Activities highly variable. Simplified K-40 Decay Scheme

89.3% β- to Ca-40 (stable) 10.7% e.c. to Ar-40 (stable)

585 keV average β energy 1.461 MeV γ ray Decay is to ground state. Few c.e.; γ yield 10.7% per n.t.

Bremsstrahlung Annihillation photons from β+ << 1% of β energy <0.2%. Folded into the 10.7%.

No other significant No other significant radiations

Reference Man K-40 Self Dose Rate

# n.t./y = (4440 /s) (3.156E7 s/y) = 1.4E11 /y β self dose /y assuming uniform activity: (1.4E11 /y)(0.893)(0.585 MeV)(1.6E-13 J/MeV) / 70 kg = 0.17 mGy/y (NCRP 94 gives 0.16 mGy/y) γ self dose /y: (1.4E11 /y)(0.107)(1.461 MeV)(A.F.)(1.6E-13 J/MeV) / 70 kg = (0.05)(A.F.) mGy/y (A.F. ≈ 0.5 using MIRD) = 0.025 mGy/y (NCRP 94 gives 0.02 mGy/y) = 20 µGy/y = 20 µSv/y Max. Dose Rate to Spouse from Ref. Man:

Rate of Photon Energy Escaping into 4π sr: (0.05 mGy/y)(1 – A.F.=0.5)(70 kg) = 1.75 mJ/y Quick Estimate of Maximum Dose Rate to Spouse: [Closest-packing co-ordination number of a circle is 6.] (1/6)(1.75 mJ/y)(A.F.)(8 h / 24 h) / 60 kg

= (1.6)(A.F.) µGy/y = 1 µGy/y for A.F. = 0.6 [?] Overestimate: contact; 4π/6 sr too large; M irr. F

(Most widely propagated folklore: 20 µGy/y) Monte Carlo Results (all results in µGy/y)

24 h/d Dose 8 h/d Dose Male (M) Photon Self Dose 16 Female (F) Photon Self Dose 12

M  F Touching Geometry 3 1 F  M Touching Geometry 2 0.7 M  F 10-cm Separation 2 0.7 F  M 10-cm Separation 1 0.3 M  F 30-cm Separation 1 0.3 F  M 30-cm Separation 0.6 0.2 20 µSv/y debunked …

• … and easily, too! • So how does it survive/propagate?  examine at end of talk

• Defensible dose rate estimate appears to be 0.2 or 0.3 µSv/y. But wait!  The body is a source, but it’s also a shield (and a scatter medium).

Terrestrial Photon Dose to Cylinder With vs. Without Another Present – MCNP Results

• Touching Geometry: -9% (lower dose with two present) • 25-cm Separation: -4% (lower dose with two present) • UNSCEAR Indoor Terrestrial Doses (but assuming 8 h / d) World average: 170 µSv/y U.S.A. (very low): 80 µSv/y Let’s use 100 µSv/y as a reference. Touching Geometry: -9 µSv/y vs. nominally +0.9 µSv/y from K-40 25-cm Separation: -4 µSv/y vs. nominally +0.3 µSv/y from K-40 So, you’re 10 times a greater shield than a source! (assuming no recent nuclear medicine administration) Radiation Dose From Ingestion of Potassium-rich Foods Radiation Folklore Goes

Putative doses calculated for ingestion of potassium-rich foods, using ICRP adult ingestion DCF for K-40. New unit conceived: “ ” Sample cal’n: (6.2 nSv/Bq) (31.7 Bq/g) (0.422 g) = 83 nSv Rounded to 0.1 µSv Propagated Folklore: Eating a banana = 0.1 µSv ICRP DCF = 6.2E-9 Sv/Bq (K-40 adult ing.) Let’s figure out what this assumes. Crude calculation (uniform activity) using ICRP data:

1 / λbio ≈ 43 d # n.t./Bq ≈ (43 d) (8.64E4 s/d) (1 /s) = 3.7E6

3.7E6 [(0.893)(0.585 MeV) + (0.107)(1.461 MeV)(0.5)] x (1.6E-13 J/MeV) / 70 kg = 5.1E-9 Gy ( /Bq )

 Evidently, ICRP DCF assumes a long retention time for K in the body. [for the atoms ingested] Proposed Simplified(!) Potassium Metabolic Model • Mean intake is 3.3 g/day in Reference Man • 85% excreted in urine at, say, 4 hours • 11% excreted in feces at, say, 24 hours

• 4% excreted in sweat et al. at, say, 24 hours [?] • Equivalent single retention time (=# n.t./Bq): 0.85(4 h) + 0.15(24 h) = 7 hours • (Unusual heavy sweating before ingestion may result in K deficit and subsequent longer retention) [?] Here’s the thing …

• If action A is claimed to deliver dose D, then one should feel justified in assuming that dose D is that dose that is above the baseline dose that would have been delivered had action A not occurred. • K is under homeostatic control via kidney function, implying that ingestion of X Bq of K results in excretion of 0.85 X Bq of K a few hours later, and 0.15 X Bq (generously) a day later if, in both cases, the K has the natural isotopic composition (0.0117% K-40).

Consider Three Scenarios: Case 1: Ingestion of carrier-free (isotopically pure) K-40. ICRP DCF applies. Case 2: Ingestion of natural K before or in the absence of Case 1. Derive dose from, say … ICRP DCF x 7 h / [(43 d)(24 h/d)] = 0.7% DCF. Case 3: Ingestion of natural K after Case 1. Net dose will be negative if previous Case-1 ingestion was significant and recent enough that the body is still isotopically rich in K-40. Banana Summary:

The K atoms from the banana when ingested have a mean retention time of 43 days. But, ingesting them triggers the excretion of K atoms (most from the inventory present in the body before the banana was eaten). We assumed mean excretion occurs 7 hours after ingestion. If so, the dose would be 0.7% of the widely propagated folklore dose.

Widely Propagated Folklore about Cosmic Radiation

• Cosmic ray dose being attributed to the sun

• Earth’s magnetic field being critical in protection of life on earth from cosmic rays

Let’s see. (But with a few distractions) Prelude to Discovery of Cosmic Radiation

• 1895 discovery of x-rays • 1896 discovery of radioactivity (in U) • 1897 discovery of the electron • 1898 discovery of Po, Ra •  the Earth is radioactive • c. 1900 discovery of Rn (“emanation”) •  the atmosphere is radioactive Museum Early 20th Century Radiation Folklore Did these (and other) great scientists’ work delay the discovery of cosmic rays? (an aside: Radiological Protection Practices c. 1900) Evidence that Random Events Cluster ( They do, but … Alert!: selective post-hoc observation here ) Observations 1900 - 1911

• Spontaneous electroscope discharge noted; But not entirely unexpected (charge-leakage aside). Some suspicion part of radiation of ET origin. • c. 1910: Theodore Wulf: bottom vs. top of Eiffel Tower • c. 1910: Dominico Pacini: off-shore 3-m depth vs. surface • Others: balloon flights (but with instrument problems) • Results not unambiguously attributed to source of ET origin • Victor Hess: series of balloon flights 1912

• A year of tragedy – the Titanic hits an iceberg and sinks [hold that thought] • Victor Hess balloon flights continue; one ascending to 5000 metres • Unambiguously attributes high-altitude dose increases to ET source of extreme energies • (Notes no day/night difference) • (Notes no decrease during solar eclipse) Victor Hess 1912 Resulted in Nobel Prize in 1936 for discovery of cosmic rays. Cosray -- 120 Deep River Road Former cosmic ray counting lab SNO drift to Sudbury Neutrino Observatory

Where you go to get away from (most) cosmic rays. Two Categorizations of Cosmic Rays

According to Origin: “Galactic” (and Extragalactic) vs. “Solar” (not included in Galactic) and Primaries (incident on or beyond the upper atmosphere *one def’n+) vs. Secondaries (produced directly or indirectly from primaries) Primary Cosmic Ray Spectra

10 MeV to 100 GeV 100 MeV to 108 TeV + Upper Atmosphere CR Doses Secondary Particle Doses (%) by Particle Type as a Function of Altitude Biography of the Muon (µ)

• Created from charged pion decay 2 • m0 = 106 MeV/c 1/λ = 2.2 µs • Began nominative life as the “mu meson” • Discovered in CR when looking for mesons ( now quark/anti-quark hadrons) • But it behaved like, and is, a lepton 2 • φ ≈ 1 /cm /minute at sea level; Eavg ≈ 4 GeV • A nuisance (difficult-to-shield background) • But also useful (e.g., muon tomography)

Cosmic ray dose anti-correlated with solar activity (Solar output deflects incoming GCRs)

Aircraft altitude CR dose vs. solar activity Ground-level CRs vs. sunspot number Evidence that CR doses (both ground-level and high- altitude) are almost exclusively not of solar origin

• No significant day/night differences • Diurnal and seasonal directional symmetry • No decrease during solar eclipses • Measured solar and galactic spectra vs. cut-off rigidities and atmospheric attenuation • Inverse relationship with solar activity • Forbush decreases with solar particle events • Rarity of ground-level solar particle events Earth’s Magnetic Field and Resulting Cosmic Ray Cut-off Rigidities Effect that disappearance of Earth’s magnetic field would have on CR doses Existing geomagnetic field already offers almost no shielding at higher latitudes (>50°); nevertheless, dose rates are: • at Sea Level: >50° vs. 0° : +15% ± • at Flight Altitudes: >50° vs. 0° : x 3 ±

• Compared to this  x 1000 if no atmosphere Or even this  x 100 flight vs. sea level Components of Cosmic Ray Extensive Air Shower CORSIKA Simulation of Air Shower from a 100-GeV Primary CORSIKA Simulation of Extensive Air Shower from a 100-TeV Primary CERN CERN and Cosmic Ray Connections

• Information on discovery of cosmic rays • Simulating UHE cosmic-ray basic interactions to refine cosmic-ray transport codes • Investigating cosmic-ray involvement in atmospheric cloud formation (CLOUD) • Explain non-threat of LHC black-hole creation • Higgs Boson nickname (“the God Particle”) Huh? 1991 October 15; Fly’s Eye Detector, Utah The “Oh-My-God!” Particle: Estimated Energy: 3.2 x 1020 eV ! “Cosmic rays sank the Titanic” [at least, according to Nigel Calder] “A lazy Sun launches iceberg armadas.” Cosmic ray intensity varies (Svensmark and Calder) inversely with solar activity. “Cosmoclimatology” – the Theory

• (Henrik Svensmark et al.) • Low-level clouds cool via sunlight albedo • GCR muon secondaries cause low-level cloud formation [?] (CLOUD experiments at CERN) • More GCRs  cooler climate • e.g., galactic arm traversals & cold-climate proxies • e.g., Be-10 vs. temperature proxies in ice cores • More active Sun  fewer GCRs [!]  warmer [?] • Less active Sun  more GCRs [!]  cooler [?]

Mount Everest One of the Questions We Won’t Answer: Under what circumstances can one be considered to have climbed it? Who First Summited Mt. Everest?

Edmund Hillary and Tenzing Norgay in 1953? OR George Mallory and/or Andrew Irvine in 1924?

Two other questions: Does one-way count? Have cosmic rays destroyed evidence?

Some Clues to the Summit Question

Found Not Yet Found • Mallory’s body (1999) • Irvine’s body • Documents on his body  • Photo of Mallory’s wife [?] • Snow goggles in his pocket • Camera

Nominal Estimate of 90-year Cosmic-ray Doses at 8200 metres and 28° latitude

• 400 mGy low-LET (electrons, muons) • Reciprocity failure prevents image degradation [?]

• 200 mGy high-LET (protons, neutrons)* • No reciprocity failure for high-LET radiations • * Very-high-energy protons have lower LET • Dose likely fatal to latent images on film [?] And… some radiation folklore

In instructions for handling recovered camera: • Film “damage by hand-carry-on x-ray” units • “film completely wiped out by checked- baggage x-ray” • and Kodak gets the relevant radiation type wrong It’s the X-ray units that have the bad image! • Hand-carry-on x-ray units give negligible dose • Checked baggage may get CT scanned, which can deliver doses on the order of 1 to 2 mGy • 1 to 2 mGy is not likely image-destructive, unless image is already highly compromised Anti-Folklore Summary

• Average adult confused with young and male • Spousal irradiation wrong in quantity and sign • K-40 food dose overstated by a factor of 100 • CR dose is from sources other than the sun • The atmosphere is the chief CR shield • Airport x-rays don’t ruin vacation pictures Folklore Origin/Propagation Theory What we observe is not nature itself, but nature exposed to our method of questioning.

Werner Heisenberg

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