SAIC.com © SAIC. All rights reserved. 1 Fallout Deposition In Hiroshima Where Gamma-Ray Thermoluminescence Measurements Exceed the Dosimetry System (DS02) Doses Stephen D. Egbert Science Applications International Corporation Presentation at Health Physics Meeting – Sacramento, Calif. - July 24, 2012 Department of Energy Special Session on Atomic Bomb Survivor Dosimetry – Residual Radiation Exposure

SAIC.com © SAIC. All rights reserved. 2 Since 1945, we believed Hiroshima residual radiation Hypocenter neutron ground activation (out to 0.5 km) Koi-Takasu area fission products (WSW 3-4 km) Possibly in “black rain” area fission products (NW 1-10 km) Shizuma (1996) finds a pattern of 137 Cs, but very little Imanaka (2011) finds original MED survey readings Pattern like 137 Cs; But higher dose especially NNE at ~2 km Slow drop off in south until ~1 km where measurements end Egbert and Kerr (2012) finds four high TLD dose areas Nishitera temples (NNW 1 km)~ mGy Hiroshima University area (south 1.5 km)~200 mGy Miyosen Temple (east 1.9 km)~100 mGy Hiramoto House (west 2.1 km)~100 mGy TLD pattern is similar to survey and 137 Cs, but one and two orders-of-magnitude higher, respectively MED – Manhattan Engineering District TLD – Thermoluminescence Dosimetry Residual Radiation at Hiroshima

SAIC.com © SAIC. All rights reserved. 3 Measured γ doses were obtained in ceramic tiles by thermoluminescence dosimetry (TLD) and compared with discrete ordinate and Monte Carlo calculations In DS02 Report Executive Summary for γ dose For Hiroshima “there remain some indications of measured values exceeding calculated values at longer distances” For Nagasaki “the measured values tend to be somewhat less than calculated values, at least out to about 800 meters from the hypocenter” Average weighted γ dose M/C ratio was 1.06 at Hiroshima and 0.80 at Nagasaki DS02 – Dosimetry System 2002 M/C – Measurement to Calculation DS02 γ Dose Summary

SAIC.com © SAIC. All rights reserved. 4 Click for animation TLD – Thermoluminescence Dosimetry Nagasaki TLD Measurements to Calculation Ratio (After adjustment for unaccounted shielding) Hiroshima TLD Measurements to Calculation Ratio

SAIC.com © SAIC. All rights reserved. 5 Excess TLD Doses in 20 Nagasaki Neighborhoods Used in the DS02 Report TLD – Thermoluminescence Dosimetry DS02 – Dosimetry System 2002

SAIC.com © SAIC. All rights reserved. 6 TLD – Thermoluminescence Dosimetry DS02 – Dosimetry System 2002 Excess TLD Doses in 29 Hiroshima Neighborhoods Used in the DS02 Report

SAIC.com © SAIC. All rights reserved. 7 MED Survey Map Over Hiroshima Excess TLD Measurements Survey contours from measurements made during October 3-7, 1945 (in milliroentgen per hour) TLD locations identified Excess TLD dose locations labeled in italic red (>0.04 Gy) and underlined (>0.4 Gy) or blue (not observed) Shading indicates confidence TLD samples, with small black labels, are too close to hypocenter MED – Manhattan Engineering District TLD – Thermoluminescence Dosimetry

SAIC.com © SAIC. All rights reserved. 8 Map of 137 Cs and Rain Amount Over Hiroshima Excess TLD Measurements Shizuma 137 Cs measurements indicated by relative radius of circles. Red circle is scaled down by a factor of 20 in order to fit on page (~0.04 Gy) TLD locations identified Excess TLD dose locations labeled in italic red (>0.04 Gy) and underlined (>0.4 Gy) or blue (not observed) Shading indicates confidence TLD samples, too close to hypocenter, are not shown TLD – Thermoluminescence Dosimetry

SAIC.com © SAIC. All rights reserved. 9 MED Survey Map Over Nagasaki TLD Measurements Survey contours from measurements made during September 21 to October 4, 1945 (in milliroentgen per hour) TLD locations identified Excess TLD dose locations labeled in italic red (>0.04 Gy) and underlined (>0.4 Gy) or blue (not observed) Shading indicates confidence TLD samples, with small black labels, are too close to hypocenter Nishiyama Reservoir MED – Manhattan Engineering District TLD – Thermoluminescence Dosimetry

SAIC.com © SAIC. All rights reserved. 10 Discussion About Excess TLD Dose Method Advantages of Excess TLD Dose Method Excess TLD dose and residual dose to survivors may be from same isotope(s), absorbed in same period (first days) Location TLD dose received is stationary and known Few TLD weathering effects - No rain following weeks TLD may allow proxy measurements of both skin and deep dose using ceramic as surrogate Disadvantages Cannot discern excess TLD dose closer than 1 km from hypocenter, where initial radiation gamma-ray dose is high Uncertainty of ceramic TLD background may cause significant uncertainty in estimate of excess TLD dose TLD – Thermoluminescence Dosimetry

SAIC.com © SAIC. All rights reserved. 11 Conclusions TLD – Thermoluminescence Dosimetry DS02 – Dosimetry System 2002 TLD measurements and DS02 calculations are consistent, except in certain Hiroshima neighborhoods beyond 1 km TLD measurements in excess of DS02 calculations may be from fallout deposited on or near a measured ceramic sample It may be possible to make TLD measurements using different layers of the same sample to obtain data on the β, γ and bremsstrahlung doses from fallout Obtaining a more complete set of TLD measurements (beyond 1 km) is a method to distinguish which suburbs and neighborhoods did and did not receive fallout It may be possible to use excess TLD dose to estimate fallout deposition to provide a basis for calculating fallout doses to distal as well as proximal Japanese survivors Other physical dosimetry and biological effects for survivors, such as epilation, should be reexamined to see if similar patterns are observed as indicated by the excess TLD doses