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Activation of cobalt by neutrons from the Hiroshima bomb

TL;DR: In this paper, a study has been completed of cobalt activation in samples from two new locations in Hiroshima, consisting of a piece of steel from a bridge located at a distance of about 1300 m from the hypocenter and pieces of both steel and concrete from a building located at approximately 700 m.
Abstract: A study has been completed of cobalt activation in samples from two new locations in Hiroshima. The samples consisted of a piece of steel from a bridge located at a distance of about 1300 m from the hypocenter and pieces of both steel and concrete from a building located at approximately 700 m. The concrete was analyzed to obtain information needed to calculate the cobalt activation in the two steel samples. Close agreement was found between calculated and measured values for cobalt activation of the steel sample from the building at 700 m. It was found, however, that the measured values for the bridge sample at 1300 m were approximately twice the calculated values. Thus, the new results confirm the existence of a systematic error in the transport calculations for neutrons from the Hiroshima bomb. 52 refs., 32 figs., 16 tabs.

Summary (1 min read)

INTRODUCTION

  • Telephone cables carried on the east side of bridge (Fujita, 1988) .
  • Measured after dissection of the sample and cleaning of the parts by sandblasting.
  • The mass of the sample before dissection and cleaning was approximately 26 kg (57 pounds).
  • In addition to the steel samples from Hiroshima, four other steel samples were included in the study (Table 5 ).

Concrete staple:

  • The stucco layer was separated fror the noraal layer and treated as a separate sample.
  • Portions of the samples also were dissolved by nitric acid-hydrofluoric acid digestion and a lithium-borate fusion.
  • Because the concrete sample was stored indoors in a dry environment for several years, it was necessary to make an estimate of the free water content of the concrete under more normal conditions.
  • Table 8 compares the resulting composition to other data on a concrete sample from the Joyarea Primary School in Nagasaki (Maruyama, 1987) .
  • A problem with the previous calculations for cobalt activation of steel rebars in Hiroshima has been a lack of data on trace elements in concrete, particularly boron (Loeve et al, 1987) .

Background radiation

  • Counted for 400000 8 starting on 2/18/88 are well suited to counting of *°Co which emits two gamma rays that can be detected simultaneously in the two Nal(Tl) detectors .
  • Two of the places from the bridge and the bottom plate from the handrail were counted using two such detector systems at PNL (Systems 8 and 9).
  • This Count of sample after surfaces were dressed by machining.
  • E Counts of this sample were used as the background rates for the two detector systems, 9 ).
  • The Homestake Hine sample was helpful in establishing the fact that neutrons produced by cosmic rays did not contribute significantly to the cobalt activation of the bridge sample (Brodzinski, 1988) . 9 ).

COBALT-60 CALCULATIONS

  • The effect of a sample's environment on cobalt activation within the sample was determined by the use of adjoint neutron-transport calculations (Cramer, 1985) .
  • The specific features of each sample and its immediate surroundings were modeled within a large parallelepiped as follows.

Chugoku Electric Company:

  • To properly orient the model with respect to the hypocenter, the x-axis was rotated 24 degrees in a clockwise direction from a line connecting the origin of the coordinate system and the hypocenter .
  • Only the shell of the building was modeled .

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OBHL—6590
DB90 008018
Health
and
Safety Research Division
ACTIVATION
OF
COBALT
BT
NEUTRONS FROM
THE
HIROSHIMA BOMB
G.
D.
Kerr,
F. F.
Dyer,
J. F.
Emery,
J. V.
Pace
III,
R.
L.
Urodzinski,
and J.
Marcum
Manuscript completed: September
26. 1989
Date published: February
1990
NOTICE: This document contains information
of a
preliminary
nature.
It is
subject
to
revision
or
correction
and
therefore does
not
represent
a
final report.
Prepared
for the
U.S.
DEFENSE NUCLEAR AGENCY
Washington,
D.C.
20305
Under Contract
No. DNA
88-853
and
Interagency Agreement
No. DOE
0046-A130-A1
Prepared
by th«
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831
operated
by
MARTIK MAE
T
.?TTA ENERGY SYSTEMS,
INC.
for
the
U.S.
DEPARTMENT
OF
ENERGY
Under Contract
No.
DE-AC05-84OR21400
MAS
i
tit
DISTRIBUTION OF THiS DOCUMENT
16
UNLIMITED

TABLE OP CONTENTS
Page
LIST OF FIGURES v
LIST OF TABLES %
ABSTRACT 1
INTRODUCTION 2
DOSE REASSESSMENT STUDIES 3
CURRENT STUDY SAMPLES 15
ELEMENTAL ANALYSES 33
COBALT-60 MEASUREMENTS 43
COBALT-60 CALCULATIONS 59
DISCUSSION 69
ACKNOWLEDGEMENTS 74
LIST OF REFERENCES : 75

LIST OF FIGURES
Figure Page
1. Comparison of DS86 and T65D values for the radiation fields
in the open in Hiroshima 4
2.
Comparison of DS86 calculations and IT. measurements of the
gamma-ray kerma in the open in Hiroshima 5
3. Comparison of DS86 calculations (Kerr et al, 1987) using the
discrete ordinates code,
DOT-4,
with other calculations using
the TART Monte Carlo code (Mendelsohn 1987) 6
4.
Schematic of the decay scheme for "Co 8
5. Schematic shoving location of steel samples in Hiroshima.. .. 9
6. Picture shoving the iron rings on roof of the Kodokan
Building after the atomic bombing in 1945 10
7.
Data from *°Co measurements made during the 1960's by the
Japanese national Institute of Radiological Sciences 11
8. Data on cobalt activation of iron rings from studies at
the Japanese National Institute of Radiological Sciences
(NIRS) and Lawrence Live wore National Laboratory (LLNL) 12
9. Data on cobalt activation of steel rebars from studies at
the Japanese National Institute of Radiological Sciences
(NIRS) and Lawrence Livermore National Laboratory (LLNL) 13
10.
Calculated to measured ratios for cobalt activation in
Hiroshima, using data from studies at Lawrence Mvermore
National Laboratory
(LLNL),
Japanese National Institute
of Radiological Sciences
(NIRS).
and Science Applications
International Corporation (SAIC) 14
11.
Picture showing the main entrance on vest side of the
Chugoku Electric Company after the bombing in 1945 17
12.
Picture showing the west elevation of the Yokoga«ra Bridge
after the bombing In 1945 18
13.
Schematic showing the construction of the Chugoku Electric
Company and its dimensions in feet and inches (1' equals
30.48 cm and 1" equals 2 54 cm) 20
14.
Picture of concrete sample from a wall section between
first-floor windows on the north side of Chugoku Electric
Company , 21

Page
15.
Picture of the handrail saaple from the stand at the top
of thi saokestack of the Chugoku Electric Coapany 22
16.
Picture showing the north wall and the saokestack of the
Chugoku Electric Coapany as viewed froa the hypocenter of
the boab (see building in the foreground on the right-hand
side of the photograph) 25
17.
Picture showing a stand idencical to the one Mounted on the
»kestack of the Chugoku Electric Coapany 26
18.
Picture showing the Yokogawa Bridge after its construction
in 1922 27
19.
Picture showing the Yokogawa Bridge before its demolition
in 1983 28
20.
Schematic showing Che construction of the Yokogawa Bridge
and its dimensions in ieet and inches (1' equals 30.48 cm
and 1" equals 2.54 cm) 29
21.
Picture of saaple cut from top of arch on the east side of
the Yokogawa Bridge 31
22.
Picture of the bridge sample after dissection and cleaning
by sandblasting 32
23.
Effect of boron content of concrete on cobalt activation of
steel rebar at a ground i.ange of 1180 a in Hiroshima 44
24.
Gamma-ray spectrum from preliminary ORNL measurements of
•°Co in handrail sample froa Hiroshima (Detector 5) 45
25.
Gamma ray spectrum from preliminary ORNL measurements of
•°Co in bridge sample froa Hiroshima (Detector 5) 46
26.
Detector background for preliminary ORNL measurements of
•°Co in bridge sample from Hiroshima (Detector 5) 47
27.
Schematic of detector systems used in PNL measurements of
60
Co in steel samples from Hiroshima (Systems 8 and 9) 49
28.
Schematic of bottom rail plate with shading to indicate
portions of dissected sample used in PNL measurements 51
29.
Scheintic of D-plate from bridge with shading to indicate
portions of dissected sample used in PNL measurements 53
30.
Schematic of the Chugoku Electric Company showing coordinate
system used in MORSE Monte Carlo calculations 63
vi

Citations
More filters
Journal ArticleDOI
TL;DR: In this article, inconsistencies between low-energy neutrons and DS86 calculations for Hiroshima are examined using all available measurement data, including new measurements for 36Cl which extend the measurement range to more than 1.7 km from the epicenter, and Monte Carlo modeling calculations for each sample measured.
Abstract: More than a decade has passed since a complete revision was initiated of the radiation doses received by survivors of the Hiroshima and Nagasaki atomic bombings. The new dosimetry system (DS86) was completed in 1986 and adopted shortly thereafter. Overall, DS86 was noted to be a clear improvement over the old dosimetry system. However, based on limited validation measurements, troublesome inconsistencies were suggested for neutrons. Since 1986, a substantial number of additional neutron activation measurements have been made in mineral and metal samples from Hiroshima. Importantly, a large number of measurements have now been made at distances beyond 1 km. Here, inconsistencies between neutron activation measurements and DS86 calculations for Hiroshima are examined using all available measurement data, including new measurements for 36Cl which extend the measurement range to more than 1.7 km from the epicenter, and Monte Carlo modeling calculations for each sample measured. Results show that thermal neutron activation measured beyond approximately 1 km in Hiroshima (at distances most relevant for radiation-risk evaluation) is two to 10, or more, times higher than that calculated based on DS86. Similar trends observed when comparing results by several independent measurement laboratories, using different analytical methods, suggest that the DS86 calculations for low-energy neutrons are in error. Because of the importance of the Hiroshima data in radiation risk evaluation, this large discrepancy is in need of resolution.

124 citations


Cites methods from "Activation of cobalt by neutrons fr..."

  • ...However, because the water content was measured several decades later-after the samples had been collected, transported, and stored in a dry place in preparation for analysis-a nominal free-water value of 5% was adopted from available data on similar concretes (Kerr et al. 1990)....

    [...]

  • ...Measurement results for I5'Eu (H), 1 5 4 E ~ (U), and 6oCo (0) were obtained from previously published reports and papers (Hashizume et al. 1967; Hashizume 1983; Nakanishi et al. 1983, 1987; Hasai et al. 1987; Maruyama and Kawamura 1987; RERF 1987a,b; Sakanoue et al. 1987; Hoshi et al. 1989; Kerr et al. 1990; Kimura et al. 1990)....

    [...]

Journal ArticleDOI
TL;DR: Residual radionuclides induced by neutrons from the Hiroshima atomic bomb have been measured at Kanazawa University for 14 years and close agreement was found between measured and calculated values for the specific radioactivity of 152Eu in the samples exposed at ground ranges between 320 m and 720 m.
Abstract: Residual radionuclides induced by neutrons from the Hiroshima atomic bomb have been measured at Kanazawa University for 14 years. The results of 152Eu, 154Eu and 60Co are reviewed in this paper. Where appropriate, an attempt is made to provide our new data with the aim of reinterpreting our published data. From the comparison of the measured values with the calculated values by DS86 methodology, we may point out here: (1) that close agreement was found between measured and calculated values for the specific radioactivity of 152Eu in the samples exposed at ground ranges between 320 m and 720 m; (2) that the calculated/measured ratios for the specific radioactivity of 152Eu were, however, larger than unity in the vicinity of ground zero and smaller than unity at locations more than 1000 m apart from ground zero; (3) that, in the vicinity of ground zero, epithermal neutron fluence evaluated from a set of measured specific radioactivities of 152Eu, 154Eu and 60Co showed a close agreement with the calculated result, whereas thermal neutron fluence evaluated in the same way was different from the calculated result; and (4) that the depth distribution of the specific radioactivity of 152Eu in a wall sample which was exposed at the location 320m from ground zero approximately agreed with the calculated result.

33 citations

Journal ArticleDOI
TL;DR: Good agreement was observed between measurements of neutron activation and DS86 calculations for Nagasaki, as well as for the reactor experiment, suggesting the large discrepancy observed in Hiroshima appears to be due to uncertainties associated with the Hiroshima bomb itself.
Abstract: Recent reports have clearly demonstrated that large discrepancies exist between neutron activation measured in Hiroshima and activation calculated using the current dosimetry system DS86. The reports confirmed previous results for cobalt activation in Hiroshoma that suggested problems, and this has spurred a joint U.S.-Japan effort to identify the source(s) of this discrepancy. Here, new results are presented that appear to eliminate both the measurements of neutron activation and the DS86 air-transport calculations are potential sources of the discrepancy in Hiroshima. Computer transport of DS86 fission neutrons through large distances of air was validated using concrete samples from Nagasaki and chloride detectors placed at selected distances from a bare uranium reactor. In both cases accelerator mass spectrometry was used to measure thermal neutron activation via the reaction. {sup 35}Cl(n, {gamma}){sup 36}Cl (half-life, 301,000 years). Good agreement was observed between measurements of neutron activation and DS86 calculations for Nagasaki, as well as for the reactor experiment. Thus the large discrepancy observed in Hiroshima appears not to be due to uncertainties in air-transport calculations or in the activation measurements; rather, the discrepancy appears to be due to uncertainties associated with the Hiroshima bomb itself. 15 refs., 3 figs., 8 tabs.

31 citations

Journal ArticleDOI
TL;DR: Biological measurements of exchange-type chromosomal aberrations in survivors at Hiroshima strongly imply that the survivors received a significant neutron dose, and there is a possibility of deriving from the A-bomb data, with reasonable confidence limits, the relative biological effectiveness (RBE) for carcinogenesis by neutrons.
Abstract: Brenner, D. J., Direct Biological Evidence for a Significant Neutron Dose to Survivors of the Hiroshima Atomic Bomb. Radiat. Res. 145,501-507 (1996). In the past few years much physical evidence has accumulated that the A-bomb survivors at Hiroshima were exposed to significant doses of neutrons, in contrast to the predictions of the current DS86 dosimetry. We discuss some biological measurements of exchange-type chromosomal aberrations in survivors at Hiroshima, which also strongly imply that the survivors received a significant neutron dose. Specifically, the ratio of translocations (an interchromosomal aberration) to pericentric inversions (intrachromosomal interarm aberration), the F value, was significantly smaller than would be expected from a y-ray exposure, and was consistent with the majority of the effective dose coming from neutrons. If this biological evidence and the previous physical evidence are correct, the effective neutron dose at relevant locations at Hiroshima dominated the total effective dose, from which it may be concluded that (1) the risk coefficient for y rays may have been considerably overestimated, and (2) there is a possibility of deriving from the A-bomb data, with reasonable confidence limits, the relative biological effectiveness (RBE) for carcinogenesis by neutrons. o 1996 by Radiation Research Society

27 citations


Additional excerpts

  • ...RADIATION RESEARCH 145,501-507 (1996) 0033-7587196 $5....

    [...]