## External Dose Estimates from NTS Fallout

External Radiation Exposure to the Population of the Continental U.S.
from Nevada Weapons Tests and Estimates of Deposition Density of
Radionuclides That Could Significantly Contribute to Internal Radiation
Exposure via Ingestion

Harold L. Beck

Report to the National Cancer Institute in fulfillment of

P.O. #263-MQ-909853

June 30, 1999 (revised Nov. 1, 1999)

**Abstract**

This report provides estimates of the external radiation exposure and
whole-body effective dose received by residents of the continental U.S.
during the period 1951-1962 from weapons tests carried out at the Nevada
Test Site (NTS). Estimates are given on a county- by-county basis for
each test and for each year of testing. The average committed population
dose from all NTS tests was about 0.5 mSv, about equivalent to 1-2 years
of external radiation exposure from natural background. Residents of the
counties immediately downwind from the NTS incurred much higher doses,
in excess of 3 mSv, while the residents of the Far West, Pacific
Northwest and Southeast received lower than average exposures. The tests
and radionuclides that contributed the most exposure are discussed, as
well as the dependence on fallout time of arrival. The most exposed
individuals were outdoor workers; the least exposed were persons who
spent most of their time indoors in heavily constructed buildings.

The deposition of radionuclides that contribute to internal radiation
exposure via the ingestion pathway was also calculated on a
county-by-county and test-by-test basis. The general pattern of
deposition, tests contributing the most to the deposition, deposition
density versus distance from the NTS, and the differences in deposition
between radionuclides are discussed. In general the deposition of
long-lived radionuclides such as Sr-90 and Cs-137 was about a factor of
20 less than that from "global fallout" from high- yield weapons tests
carried out in the Pacific and Soviet Union. However, the deposition of
short-lived isotopes such as I-131 was greater than from "global
fallout."

**Introduction**

In response to a request by Congress to the CDC and NCI to investigate
the impact on the U.S. population from weapons tests, the NCI contracted
with the author of this report to:

"Prepare crude estimates of the doses *[from external
irradiation]{.underline}* received by the American people as a result of
the above-ground tests carried out *[at the Nevada Test
Site.]{.underline}* These dose estimates would be:

-   based on a review of the readily available open literature and
    information; it is not expected that sophisticated computer models
    should be developed or used for this purpose. For the purposes of
    this assessment, the extensive database of Iodine-131 that was
    prepared by NCI in the framework of the nationwide NTS fallout study
    could be used;

-   averaged over large regions of the continental U.S., with
    indications on how the high-risk populations would be identified.
    However, if feasible, primary calculations should be carried out on
    a county-by-county basis, and averaged only for presentation
    purposes;

-   calculated separately for the most important radionuclides produced
    in nuclear weapons tests. Those would include, but would not be
    limited to Te-I-132, Ba-La-140, Zr-Nb-95, Cs-137, and Np-239;

-   provided in terms of average whole-body dose for gamma irradiation
    and of dose to the skin for beta irradiation.

-   calculated by year and summed over all NTS tests, with a comparison
    to the published UNSCEAR latitudinal averages for all tests.

2\. Provide a list of references regarding: (1) the history of nuclear
weapons testing at the NTS; (2) the production of important
radionuclides during those tests; (3) the networks of fallout
measurements; (4) the assessment of the activities deposited on the
ground; (5) the vertical migration of fallout radionuclides into deeper
layers of soil; and (6) the assessment of the doses from external
irradiation.

3.  Identify reports that could be declassified. Examples of such
    reports are those that would provide the fission and total yields,
    and those that would greatly facilitate the estimation of doses due
    to the plutonium isotopes."

This report, along with an associated electronic database, is presented
in fulfillment of the above scope of work.

As per the scope of work, this report relies heavily on previous studies
of NTS fallout, e.g., NCI (1997); Hicks (1982, 1990); Church et al.
(1990); Beck et al. (1990, 1996). Exposure rates and deposition
densities were calculated for about 60 of the approximately 100
atmospheric tests conducted at the NTS. These 60 tests accounted for
over 95% of the total I-131 produced (NCI, 1997) and corresponded to the
majority of tests for which total I-131 deposition was estimated by the
NCI (1997) in their study of I-131 exposure to the American people from
NTS fallout. A few tests considered in the NTS study for which only
local fallout estimates were estimated were not treated in this study.
The tests considered in this report are listed in Table 1. Table 1 also
gives some specific information about each test that was used in the
calculations described later in this report.

The basic starting point for the estimates in this report were the daily
I-131 deposition density estimates and associated uncertainty estimates
from NCI (1997). All calculations for this report were carried out
separately for each county (and sub-county as defined in NCI (1997),
Appendix 2, and then summed to provide estimates on a test-by-test,
annual, and total NTS basis. The total exposure and deposition density
for other nuclides was calculated from the NTS I-131 deposition
densities by using the relationships calculated by Hicks (1981) for each
NTS shot. Besides the total free-in-air exposure rate from gamma
emitters, provided by the Hicks data, estimates were also made of the
annual whole body effective dose, the beta-ray dose to the skin from
radionuclides in the surface soil, and the 50y committed effective dose.
The radionuclides that contributed most to both gamma and beta-ray
exposure were identified.

Deposition densities were estimated on a county-by-county basis for each
test for the radionuclides listed in Table 2. These radionuclides were
determined by Ng et al. (1990) to account for over 90% of the potential
dose from ingestion in the ORERP (Church et al., 1990) study. A database
(in Excel) containing the estimated deposition density of each
radionuclide listed for each test on a county-by-county basis was
provided to NCI earlier in partial fulfillment of this contract. The
database containing these deposition density estimates and associated
uncertainty estimates will be used by the NCI to estimate internal
radiation doses due to ingestion of contaminated food. The patterns of
total deposition for some of the longer-lived nuclides are discussed in
this report and the total deposition of various radionuclides is
compared to that from the \"global" fallout resulting from the
high-yield tests carried out in the Pacific and in the USSR.

In addition to the references provided in the text of this report, an
additional reading list is provided in fulfillment of item 2 of the
scope of work. A list of data that is presently classified but if
unclassified would be useful in improving the estimates made in this
report and allowing similar estimates to be made for weapons tests
conducted outside the U.S. is also included in fulfillment of item 3.

The next section of this report describes in detail the methodology used
to calculate exposure and deposition densities.

[Table 1: Tests considered in this study]{.underline}

+----------+-----+------+------+-----+-------+------+------+-----+
| **[Tes   | *   | **[y | **   | *   | **[%  | *    | *    | *   |
| t]{.unde | *[T | ield | [Typ | *[C | C     | *[Pu | *[Pu | *[C |
| rline}** | est | (kT  | e]{. | s-1 | s-137 | -240 | -241 | s-1 |
|          | D   | )]{. | unde | 37/ | from  | /]{. | /]{. | 37/ |
|          | ate | unde | rlin | ]{. | Pu\*  | unde | unde | ]{. |
|          | ]{. | rlin | e}** | und | ]{.un | rlin | rlin | und |
|          | und | e}** |      | erl | derli | e}** | e}** | erl |
|          | erl |      |      | ine | ne}** |      |      | ine |
|          | ine |      |      | }** |       | **[P | **[P | }** |
|          | }** |      |      |     |       | u-23 | u-23 |     |
|          |     |      |      | **  |       | 9]{. | 9]{. | *   |
|          |     |      |      | [Sr |       | unde | unde | *[P |
|          |     |      |      | -90 |       | rlin | rlin | u\* |
|          |     |      |      | ]{. |       | e}** | e}** | ]{. |
|          |     |      |      | und |       |      |      | und |
|          |     |      |      | erl |       |      |      | erl |
|          |     |      |      | ine |       |      |      | ine |
|          |     |      |      | }** |       |      |      | }** |
+----------+-----+------+------+-----+-------+------+------+-----+
| BAKER-1  | 1   | 8    | air  | 1   | 72%   | 0    | 0.   | 5   |
|          | /28 |      |      | .79 |       | .027 | 0006 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| Baker-2  | 2/2 | 8    | air  | 1   | 72%   | 0    | 0.   | 5   |
|          | /51 |      |      | .79 |       | .026 | 0005 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| BAKER    | 10  | 4    | air  | 2   | 100%  | 0    | 0.   | 4   |
|          | /28 |      |      | .50 |       | .033 | 0011 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| CHARLIE  | 10  | 14   | air  | 1   | 18%   | 0    | 0.   | 20  |
|          | /30 |      |      | .16 |       | .028 | 0010 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| DOG      | 1   | 21   | air  | 1   | 31%   | 0    | 0.   | 12  |
|          | 1/1 |      |      | .27 |       | .028 | 0010 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| EASY     | 1   | 31   | air  | 1   | 28%   | 0    | 0.   | 13  |
|          | 1/5 |      |      | .24 |       | .036 | 0011 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| SUGAR    | 11  | 1    | sur  | 1   | 3%    | 0    | 0.   | 316 |
|          | /19 |      | face | .06 |       | .001 | 0000 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| UNCLE    | 11  | 1    | cr   | 1   | 3%    | 0    | 0.   | 299 |
|          | /29 |      | ater | .06 |       | .001 | 0000 |     |
|          | /51 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| ABLE     | 4/1 | 1    | air  | 1   | 3%    | 0    |      | 142 |
|          | /52 |      |      | .06 |       | .001 |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| BAKER    | 4   | 1    | air  | 1   | 3%    | 0    |      | 144 |
|          | /15 |      |      | .06 |       | .001 |      |     |
|          | /52 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| CHARLIE  | 4   | 31   | air  | 1   | 31%   | 0    | 0.   | 11  |
|          | /22 |      |      | .27 |       | .051 | 0028 |     |
|          | /52 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| DOG      | 5/1 | 19   | air  | 1   | 32%   | 0    | 0.   | 11  |
|          | /52 |      |      | .28 |       | .035 | 0012 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| EASY     | 5/7 | 12   | t    | 1   | 31%   | 0    | 0.   | 24  |
|          | /52 |      | ower | .27 |       | .024 | 0005 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| FOX      | 5   | 11   | t    | 1   | 31%   | 0    | 0.   | 24  |
|          | /25 |      | ower | .27 |       | .024 | 0006 |     |
|          | /52 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| GEORGE   | 6/1 | 15   | t    | 1   | 31%   | 0    | 0.   | 24  |
|          | /52 |      | ower | .27 |       | .026 | 0015 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| HOW      | 6/5 | 14   | t    | 1   | 30%   | 0    | 0.   | 24  |
|          | /52 |      | ower | .26 |       | .027 | 0005 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| ANNIE    | 3   | 16   | t    | 1   | 32%   | 0    | 0.   | 23  |
|          | /17 |      | ower | .28 |       | .025 | 0010 |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| NANCY    | 3   | 24   | t    | 1   | 31%   | 0    | 0.   | 23  |
|          | /24 |      | ower | .27 |       | .028 | 0012 |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| RUTH     | 3   | 0    | t    | 1   | 3%    | 0    |      | 306 |
|          | /31 |      | ower | .06 |       | .000 |      |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| DIXIE    | 4/6 | 11   | air  | 1   | 31%   | 0    | 0.   | 12  |
|          | /53 |      |      | .27 |       | .022 | 0006 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| RAY      | 4   | 0    | t    | 1   | 3%    | 0    |      | 292 |
|          | /11 |      | ower | .06 |       | .000 |      |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| BADGER   | 4   | 23   | t    | 1   | 38%   | 0    | 0.   | 19  |
|          | /18 |      | ower | .34 |       | .034 | 0011 |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| SIMON    | 4   | 43   | t    | 1   | 12%   | 0    | 0.   | 60  |
|          | /25 |      | ower | .12 |       | .027 | 0006 |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| ENCORE   | 5/8 | 27   | air  | 1   | 17%   | 0    | 0.   | 20  |
|          | /53 |      |      | .16 |       | .052 | 0028 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| HARRY    | 5   | 32   | t    | 1   | 24%   | 0    | 0.   | 29  |
|          | /19 |      | ower | .21 |       | .038 | 0018 |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| GRABLE   | 5   | 15   | air  | 1   | 0%    | 0    |      | 833 |
|          | /25 |      |      | .04 |       | .001 |      |     |
|          | /53 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| CLIMAX   | 6/4 | 61   | air  | 1   | 11%   | 0    | 0.   | 33  |
|          | /53 |      |      | .11 |       | .034 | 0009 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| WASP     | 2   | 1    | air  | 1   | 71%   | 0    | 0.   | 5   |
|          | /18 |      |      | .77 |       | .055 | 0036 |     |
|          | /55 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| MOTH     | 2   | 2    | t    | 1   | 70%   | 0    | 0.   | 9   |
|          | /22 |      | ower | .77 |       | .078 | 0065 |     |
|          | /55 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| **[Tes   | *   | **[y | **   | **  | **[%  | **[P | **[P | *   |
| t]{.unde | *[T | ield | [Typ | [Cs | C     | u-24 | u-24 | *[C |
| rline}** | est | (kT  | e]{. | /Sr | s-137 | 0/23 | 1/23 | s/P |
|          | D   | )]{. | unde | ]{. | fro   | 9]{. | 9]{. | u\* |
|          | ate | unde | rlin | und | mPu\* | unde | unde | ]{. |
|          | ]{. | rlin | e}** | erl | ]{.un | rlin | rlin | und |
|          | und | e}** |      | ine | derli | e}** | e}** | erl |
|          | erl |      |      | }** | ne}** |      |      | ine |
|          | ine |      |      |     |       |      |      | }** |
|          | }** |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| TESLA    | 3/1 | 7    | t    | 2   | 98%   | 0    | 0.   | 8   |
|          | /55 |      | ower | .42 |       | .019 | 0003 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| TURK     | 3/7 | 43   | t    | 1   | 23%   | 0    | 0.   | 32  |
|          | /55 |      | ower | .20 |       | .033 | 0008 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| HORNET   | 3   | 4    | t    | 1   | 43%   | 0    | 0.   | 16  |
|          | /12 |      | ower | .38 |       | .058 | 0036 |     |
|          | /55 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| BEE/ESS  | 3   | 9    | towe | 1   | 46%   | 0    | 0.   | 13  |
|          | /22 |      | r/cr | .42 |       | .085 | 0071 |     |
|          | /55 |      | ater |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| APPL     | 3   | 17   | t    | 1   | 18%   | 0    | 0.   | 40  |
| E/WASP\' | /29 |      | ower | .16 |       | .025 | 0006 |     |
|          | /55 |      | /air |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| POST     | 4/9 | 2    | t    | 2   | 99%   | 0    | 0.   | 8   |
|          | /55 |      | ower | .47 |       | .019 | 0005 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| MET      | 4   | 22   | t    | 1   | -1%   | 0    | 0.   | 10  |
|          | /15 |      | ower | .03 |       | .007 | 0001 | 000 |
|          | /55 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| APPLE2   | 5/5 | 29   | t    | 1   | 4%    | 0    | 0.   | 186 |
|          | /55 |      | ower | .06 |       | .031 | 0008 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| ZUCCHINI | 5   | 28   | t    | 1   | 10%   | 0    | 0.   | 69  |
|          | /15 |      | ower | .11 |       | .032 | 0008 |     |
|          | /55 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| B        | 5   | 12   | t    | 1   | 53%   | 0    | 0.   | 12  |
| OLTZMANN | /28 |      | ower | .51 |       | .079 | 0060 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| WILSON   | 6   | 10   | bal  | 1   | 33%   | 0    | 0.   | 9   |
|          | /18 |      | loon | .29 |       | .082 | 0065 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| P        | 6   | 37   | bal  | 1   | 5%    | 0    |      | 74  |
| RISCILLA | /24 |      | loon | .07 |       | .011 |      |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| HOOD     | 7/5 | 74   | bal  | 1   | 12%   | 0    |      | 27  |
|          | /57 |      | loon | .12 |       | .067 |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| DIABLO   | 7   | 17   | t    | 1   | 26%   | 0    |      | 26  |
|          | /15 |      | ower | .22 |       | .062 |      |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| KEPLER   | 7   | 10   | t    | 2   | 96%   | 0    | 0.   | 7   |
|          | /24 |      | ower | .37 |       | .072 | 0054 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| OWENS    | 7   | 10   | bal  | 2   | 98%   | 0    | 0.   | 3   |
|          | /25 |      | loon | .44 |       | .070 | 0047 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| SHASTA   | 8   | 17   | t    | 1   | 22%   | 0    |      | 30  |
|          | /18 |      | ower | .19 |       | .057 |      |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| DOPPLER  | 8   | 11   | bal  | 1   | 30%   | 0    | 0.   | 11  |
|          | /23 |      | loon | .26 |       | .070 | 0046 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| SMOKY    | 8   | 44   | t    | 1   | 6%    | 0    |      | 136 |
|          | /31 |      | ower | .08 |       | .006 |      |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| GALILEO  | 9/2 | 11   | t    | 2   | 90%   | 0    | 0.   | 7   |
|          | /57 |      | ower | .19 |       | .075 | 0050 |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| WHEELER/ | 9/6 | 1    | ball | 1   | 0%    | 0    |      | 785 |
|          | /57 |      | oon/ | .04 |       | .038 |      |     |
| (+       |     |      |      |     |       |      |      |     |
| COULOMB) |     |      | sur  |     |       |      |      |     |
|          |     |      | face |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| LAPLACE  | 9/8 | 1    | bal  | 1   | 6%    | 0    |      | 72  |
|          | /57 |      | loon | .07 |       | .000 |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| FIZEAU   | 9   | 11   | t    | 1   | 47%   | 0    | 0.   | 14  |
|          | /14 |      | ower | .43 |       | .063 | 0040 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| NEWTON   | 9   | 12   | bal  | 2   | 99%   | 0    | 0.   | 3   |
|          | /15 |      | loon | .46 |       | .072 | 0058 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| WHITNEY  | 9   | 19   | t    | 1   | 45%   | 0    |      | 14  |
|          | /23 |      | ower | .41 |       | .073 |      |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| CH       | 9   | 12   | bal  | 1   | 33%   | 0    |      | 10  |
| ARLESTON | /28 |      | loon | .29 |       | .074 |      |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| MORGAN   | 1   | 8    | bal  | 1   | 26%   | 0    | 0.   | 12  |
|          | 0/7 |      | loon | .23 |       | .077 | 0063 |     |
|          | /57 |      |      |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| SEDAN    | 7/6 | 104  | cr   | 2   | 98%   | 0    |      | 8   |
|          | /62 |      | ater | .44 |       | .063 |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+
| SMALLBOY | 7   | 20   | surf | 2   | 100%  | 0    | 0.   | 8   |
|          | /14 |      | t    | .51 |       | .065 | 0056 |     |
|          | /62 |      | ower |     |       |      |      |     |
+----------+-----+------+------+-----+-------+------+------+-----+

*\*Estimated-see text*

[Table 2: Radionuclides for which deposition densities were
calculated]{.underline}

Nuclide Half life (parent), d

Sr-89 52

Sr-90,Y-90\* 10400

Sr-91 0.4

Y-91m (=0.65 \* Sr-91) \*

Y-91 59

Y-93 0.4

Zr-97, Nb-97\* 0.7

Zr-95, Nb-95\* 64

Nb-97m (=0.96 \* Zr-97) \*

Mo-99 2.8

Tc-99m (=0.96 \* Mo-99) \*

Tc-99 7.8E7

Ru-103, Rh103m\* 39

Ru-105, Rh-105m\* 0.2

Rh-105 1.5

Ru-106, Rh-106\* 368

I-131 (from NCI, 1997) 8

Te-132 3.3

I-132 (=1.03 \* Te-132) \*

I-133 0.9

I-135 0.3

Cs-136 13

Cs-137 11000

Ba-140 13

La-140 1.7

Ce-141\` 32.5

Ce-143 1.4

Pr-143 14

Ce-144, Pr-144\* 284

Nd-147 11

Pm-147 956

Np-239 2.36

Pu-239 24131 y

Pu-240 6569 y

Pu-241 14.4 y

Am-241 430 y

*\* in equilibrium with parent*

**Methodology**

**Deposition Densities**

The deposition densities of the nuclides listed in Table 2 were
calculated from the corresponding NCI estimates of I-131 deposition
density. The daily geometric mean (GM) I-131 deposition densities and
corresponding geometric standard deviations (GSD) were decay corrected
back to H+12 hours. The ratio of the H+12 h I-131 value, which includes
the I-131 that grew in from precursors (NCI, 1997), to the ratio of each
of the radionuclides in Table 2, as a function of fallout arrival time,
was calculated using Hicks (1981). The H+12 h I-131 value for each day
of fallout was then multiplied by the appropriate ratio for a time of
arrival corresponding to that day to obtain the respective deposition
density.

Because the fallout estimates based on gummed-film data were decay
corrected to the midpoint of the day of sampling and the test
detonations were generally near the beginning of the sampling period
(Beck, 1984), fallout arriving on the same day as sampling was assumed
to have a time of arrival of 0.5 d, on the second day 1.5 d, etc.
Generally, only about 10 days of data had to be considered for a given
shot, although a few shots produced significant fallout for periods of
up to two weeks. Daily deposition densities were calculated only for
short-lived nuclides (half lives less than 30 d). For longer-lived
nuclides, the ratio to H+12 h I-131 did not vary significantly over the
first several weeks of fallout and thus their total test deposition
could be calculated directly from the sum of the daily I-131
depositions.

The daily deposition densities were then summed to obtain a total test
deposition density. Since the I-131 deposition densities were given as
geometric means with a GSD, it was necessary to first transform the GM
to a mean and the GSD to a variance before summing, using standard
transformations as discussed in NCI (1997). After the means and
variances were summed, the results were transformed back to geometric
means and GSDs, assuming the sum of lognormally-distributed
distributions is itself approximately lognormally-distributed (see NCI,
1997). The Excel spreadsheet database which accompanies this report
contains both the mean values and the GM values. For the long-lived
radionuclides, the deposition densities were calculated by multiplying
the summed I-131 deposition density by the appropriate ratio for that
test from Hicks' data. No additional uncertainty was assumed due to use
of the Hick's calculated isotope ratios. Because of the large GSDs
associated with the I-131 deposition data, any small additional error in
Hicks' data would have a negligible effect on the error in the
deposition densities.

Besides, the individual test values, the deposition densities for each
test series (year of testing) and for all NTS tests were obtained by
summing the individual test results in a similar manner. The short-lived
nuclide deposition densities for radionuclides that did not contribute
significantly to external dose were not summed to obtain annual or total
values. It was assumed that for these short-lived nuclides, the exact
week of deposition would be required to make reasonable estimates of
ingestion dose. If annual sums are desired for these radionuclides, it
is a fairly simple task to obtain them since the GM to mean transformed
values are provided in the accompanying database.

A detailed example of the calculation of the deposition density of
Cs-137 and Ba-140 for a representative county for a representative test
is given in Appendix 1.

Plutonium isotopes were also contained in the fallout from Nevada
weapons tests. Pu isotopes do not contribute to external exposure and
contribute in only a minor way to ingestion exposure. The main hazard
from Pu is generally via the inhalation pathway. However, the inhalation
pathway has been shown to not have been a significant contributor to
population exposure from NTS testing (Church et al., 1990). Because of
the generally high degree of interest by the public in Pu contamination,
deposition densities of Pu-239, 240 and 241, and of Am-241 which is a
decay product of Pu-241 are also estimated in this report. However, only
crude estimates can be made for individual tests since Hicks does not
provide any estimates of relative Pu deposition. The ratios of Pu to
Cs-137, Sr-90, etc. are still classified (see Appendix 3). The reason
for the classification still being in place is that knowledge of such
ratios would allow one to estimate the fission efficiency of individual
tests. However, one can still roughly estimate Pu deposition densities
for individual tests by assuming an average ratio of Pu/Cs-137
deposition density from Pu fission based on observed environmental
measurements, if one can estimate the relative amounts of fission due to
Pu-239 versus U-235 for each test.

In Table 1, we list the ratio of Cs-137/Sr-90 activity (Hicks, 1981) and
the Pu-240/239 and Pu-241/239 atom ratios for each test (Hicks and Barr,
1984). Table 3 presents the fission yields for Pu and U-235 for a
fission neutron spectrum and for a thermal neutron spectrum.

[Table 3: Fission yields for Cs-137 and Sr-90 (England and Ryder,
1994)]{.underline}

[Nuclide U-235~f~ U-235~th~ Pu-239~f~ Pu-239~th~]{.underline}

Cs-137 6.22 6.19 6.58 5.50

Sr-90 5.46 5.78 2.05 2.10

Cs/Sr (atom) 1.14 1.07 3.21 2.62

Cs/Sr (activity) 1.06 1.00 3.00 2.44

Observed ratio 1.04 2.5

Note that the Cs/Sr ratios in Table 1 range from a value of 1.04 to 2.5.
Based on the fission yields in Table 3, one can infer that the Cs/Sr
ratio of 1.04 represents shots where the fission was entirely from
U-235, while the ratio of 2.5 represents fission entirely from Pu-239.
It is assumed that for these low-yield tests essentially none of the
fission was from high-energy neutrons and that for at least most of the
tests, no other fissionable material was used. As can be seen, both
U-235 and Pu-239 fueled most of the tests[^1]. Based on Hick's
calculations, the tests inferred to be all U-235 also correspond to
those that produced no Am-241 (Hicks, 1981) and exhibited very low
Pu-240/239 atom ratios and little Pu-241 (Table 1), consistent with a
pure U-235 weapon. (A small amount of Pu will be produced from Np-239
decay even in a pure uranium device since Np-239 is produced by the
activation of U-238). Assuming only a mixture of Pu and U-235 as fuel,
one can then derive equation 1) for the fraction f of Cs-137 activity
that resulted from Pu-239 fission for each shot:

f = 1.71 \* (x -- 1.04) / x where x is the Cs/Sr activity ratio from
Table 1. (1)

Using the Cs/Sr activity ratios from Hicks, given in Table 1, one can
then estimate the fraction of the Cs-137 produced that was from Pu-239
fission for each shot from Equation 1, above. This fraction is given in
the fifth column of Table 1.

Since these were tests, it is expected that the fission efficiency, and
thus the ratio of Cs-137 to Pu-239 from Pu fission probably varied
considerably from shot to shot. However, if we choose a reasonable
estimate for the mean for all tests and assign a conservative error
estimate, we can make rough estimates of Pu deposition which, while
possibly significantly in error for a given shot, should provide
reasonable total deposition values when summed over all shots. A Cs/Pu
ratio of 4 was thus adopted for tests where all the fission was from Pu.
Using this ratio then results in the crude estimates of total Cs/Pu for
each test shown in the last column of Table 1. The choice of this
particular ratio is somewhat arbitrary but seems to provide estimates of
Cs/Pu reasonably consistent with measurements of Cs-137/Pu-239+240 in
NTS fallout (Krey and Beck, 1981).

An uncertainty corresponding to a GSD of 1.5 was assigned to reflect the
large uncertainty in this mean efficiency estimate and the likely large
variability from test to test. Using this formulation, Pu-239+240 and
Pu-241 deposition densities in fallout were estimated for each test,
test series, and for all NTS fallout. (Note that for tower and surface
shots, since Pu is a refractory material, according to Hicks (1982,
1990) only ½ of the Pu from tower and surface shots would be deposited
outside the immediate vicinity of the NTS. Thus the Pu deposition
estimates for these shots were multiplied by ½). Because of the large
uncertainty, the Pu deposition estimated for a particular county for any
particular test has a large uncertainty (GSD ≅ 2- 4), resulting both
from the large uncertainty in the NCI I-131 deposition density estimates
as well as the large uncertainty in fission efficiency. However, the
sums over all tests have smaller uncertainty (GSD ≅ 1.5-2.0) and are
believed to present a reasonable exposition of the total Pu deposition

across the U.S. from NTS testing.[^2] Accurate estimates of Pu
deposition from particular tests will only be possible if additional
information on the Cs/Pu ratios for particular tests is eventually
unclassified and thus the Pu results presented in this report should be
treated as only preliminary crude estimates.

Some additional Pu-239 is generated from the decay of Np-239. Np-239 is
formed by the activation of U-238, present in all U fueled weapons and
possibly also in Pu-fueled devices as a tamper. Hicks (1981) provides
estimates of Np-239 for each shot and these were used to estimate the
Pu-239 that would remain after the Np-239 had decayed. This Pu-239
contribution is included in the estimates of Pu-239 in this report. For
devices partially or totally fueled by Pu, this contribution is small.
However, for U fueled devices it is the only source of Pu in the
fallout. Np-239 is also a significant contributor to external radiation
exposure rates during the first few days after detonation.

Pu-241 was also estimated from the Pu-239+240 estimate and the reported
241/239 atom ratios. At this time most of the Pu-241 deposited has
decayed into Am-241 with a resultant Am-241 activity equal to the ratio
of Pu-241/Am-241 half-lives (see Table 2).

#### External Radiation Exposure {#external-radiation-exposure .unnumbered}

Hicks (1981) calculated the relative exposure rate versus time for each
NTS test using deposition to exposure rate conversion factors published
by Beck (1980). The conversion factors used by Hicks assume the
radioactivity was distributed in the soil with a relaxation length of
about 0.1 cm for all times (the relaxation length is defined as the
depth at which an exponentially decreasing activity falls to 1/e of the
value at the surface). This value was chosen since even fresh fallout is
attenuated somewhat as a result of surface roughness (Jacob et al.,
1986; Eckerman and Ryman,1993). However, it is well established
(UNSCEAR, 1993, NCRP, 1999, Miller et al., 1990; Gale et al., 1964) that
radionuclides penetrate deeper into the soil with time. Data from the
Chernobyl accident indicates that that even after a few weeks, a
relaxation length of 1 cm is not uncommon (Likhtariov et al., 1996;
UNSCEAR, 1993), particularly in areas with typical rainfall levels.
After a few months, measurements have generally shown that the
distribution reaches about a 3-cm relaxation length before the
penetration begins to slow and asymptote (Beck, 1966; UNSCEAR, 1988;
Miller and Helfer, 1985). However, for heavily watered areas, relaxation
lengths of up to 6-7 cm have been observed (Miller et al., 1990; Beck
and Krey. 1980).

Because, as will be shown later, most of the radiation exposure occurred
during the first few weeks, the use of a 0.1-cm relaxation length by
Hicks (1981) for all time intervals had only a small impact on the total
integral exposure. However, in this report, an attempt was made to use a
somewhat more realistic model. The 0.1 cm relaxation length used by
Hicks was maintained for the first 20 d after detonation, but from 20 d
to 200 d, a relaxation length of 1 cm was used, while for times greater
than 200 days, a relaxation length of 3 cm was used. The corresponding
deposition-density to exposure conversion factors for each of these
relaxation lengths are from Beck (1980). Although a gradually increasing
relaxation length would be more physically realistic, the fact that most
of the exposure occurs in the first 20 d, did not warrant the
considerable effort that would be entailed in calculating dose rates
using a continuously-variable relaxation length.

Since the penetration into the soil would be slower in more arid
regions, maintaining the 0.1 cm relaxation length for the first 20 d
provides a slightly conservative estimate of the exposure for sites with
greater precipitation and early fallout arrival times. Table 4
illustrates the dependence of the exposure rate in air on the various
relaxation lengths. Note that the exposure rate is reduced by about 1/3
as the activity penetrates to a relaxation length of 1 cm and about ½ as
the activity penetrates to a relaxation length of 3 cm from 0.1 cm. This
accentuates the importance of the first few weeks after a test with
respect to total external radiation exposure to an even greater degree
than previous calculations based only on radionuclide decay.

[Table 4: Exposure rate (R/h per mCi/km^2^) versus relaxation length
for selected fission products (Beck, 1980)]{.underline}

[Nuclide]{.underline} [Relaxation length (cm)]{.underline}

[0.1]{.underline} [1]{.underline} [3]{.underline}

Zr-95 1.20E-02 7.94E-03 5.63E-03

Ru-103 7.85E-03 5.25E-03 3.58E-03

Rh-106 3.37E-03 2.25E-03 1.56E-03

Te-132 3.38E-03 2.29E-03 1.54E-03

Cs-137 9.29E-03 6.15E-03 4.32E-03

Ce-141 1.09E-03 7.25E-04 4.92E-04

Ce-144 2.53E-04 1.70E-04 1.16E-04

Np-239 2.56E-03 1.75E-03 1.17E-03

Since Hicks already calculated exposure rate versus time for the first
0-20 days using a relaxation length of 0.1 cm, his results for 0.5-20 d
were adopted directly and fit to a function of the form at^-x^. This
function was then integrated to obtain the total exposure from TOA to 20
d, where TOA is the time of arrival in days. In all cases the
correlation coefficient for the fit over the period 0.5-20 d was greater
than 0.99. The variation in the exponent from shot to shot also turned
out to be quite low (x = 1.109  0.022). To obtain the integral from 20
d to the end of the year, the subsequent year, and to 50y, the Hicks'
data for nuclides that contribute to the exposure at those times were
entered into a spreadsheet. The variation with time from 20 d on was
calculated directly from the appropriate Bateman equations that account
for ingrowth of precursors and radioactive decay. By using the
appropriate analytical formulae normalized to Hicks' data at 20 d, it
was possible to integrate analytically over the various intervals of
interest. Note that due to the change in depth profile at 200 d,
integration had to be done by first integrating from 20 d to 200 d (or
to the end of the first year if less than 200 d) and then from 200 d to
the end of the year.

Thus for each test, the total exposure was obtained for the year of the
test, the next year, and finally for a total period from fallout
time-of-arrival to 50 y. Hicks' calculations were normalized to unit
exposure rate at H+12 h, which corresponds to a particular value of
effective I-131 deposition density at H+12 h. Thus the ratio of the
effective I-131 deposition for each day calculated by the NCI (1997) was
multiplied by the appropriate normalized exposure integral to obtain the
actual exposure for that interval and time-of-arrival. The individual
daily estimates were then summed to obtain annual and 50y committed
exposure estimates for each test, test series, and for all NTS tests.
Again, no additional uncertainty was assigned for the exposure estimates
since the error in the deposition density estimate dwarfs the estimated
error in exposure rate estimates. The uncertainty in normalized integral
exposure for a particular day is estimated to be at most 10-20%, due
primarily to variations in the depth profile from site to site. The
errors in the conversion factors themselves are thought to be less than
5% (Beck, 1980).

A detailed example of the calculation of total exposure for a
representative county for a representative test is given in Appendix 1.

Because the NCI deposition data are given for a particular day, the
exposure estimates for sites where the fallout arrived very early (less
than 12 h) are underestimated in this report. The exposure rate falls
very rapidly during the first few hours (see Table 5) and thus the
integral is very sensitive to arrival time for short arrival times. For
this report it was assumed that the fallout that occurred on the day of
the test occurred at H+12 h (H + 0.25 h for the 1952 tests due to a
different gummed-film sample interval). Thus, for those sites where
significant fallout occurred prior to H+12 h, the data presented here
may be significantly in error (up to 50% too low). This is illustrated
by Table 5, which gives the exposure rate and integral exposure versus
time for a typical test. However, the exposure rates and external doses
for close-in sites have been calculated in great detail for each
community (Anspaugh and Church, 1990; Henderson and Smale, 1990;
Thompson et al., 1990) and these dose estimates should be used in lieu
of those in this report.

Table 5 also gives the fraction of the exposure occurring in various
time intervals. One can see that that the exposure rate falls off
rapidly with time and that over 80% of the exposure occurs in the first
20 d for an arrival time of 12 h. Thus only a small fraction of the
total exposure (about 1% as shown later) is incurred in the year(s)
after the test occurred unless the tests were very late in the year,
particularly for locations where the fallout arrived within a day or
two. The drop-off in exposure rate was of course accentuated by the
penetration of the activity into the soil with time. Previous
calculations that did not take this penetration into consideration
overestimated the total exposure. Note that the common assumption of a
t^-1,2^ decay rate and no penetration would imply only about 50% of the
dose being incurred in the first 20 d!. The difference results not as
much from the greater penetration with time but more to the fact that
the exposure rate drops off much more rapidly than t^-1.2^ after 20 d
(Hicks, 1981).

[Table 5: Relative Exposure rate and total exposure versus time of
arrival (TOA)\*]{.underline}

[TOA, d]{.underline} [Exposure rate, mR/h]{.underline} [Total Exposure
(50 y), mR]{.underline}

0.25 2.1 53

0.5 1.0 45

1.5 0.30 33

2.5 0.17 27

3.5 0.12 24

5.5 0.071 20

10.5 0.035 14

20 0.015 6

\*values are for shot HARRY but are similar for all tests.

The exposures calculated in this report are generally based on estimates
or measurements of radionuclide deposition densities and conversion
factors from deposition density to exposure rate. Very few actual
measurements of exposure were made outside the immediate vicinity of the
NTS. However, for states immediately downwind from the NTS, all
available data was used to estimate deposition densities including
actual exposure rate measurements if any (Beck and Anspaugh, 1991; Beck,
1996). The conversion factors relating deposition density to exposure
rate in air have been validated in many studies and as mentioned
previously are believed to be accurate to better than 5% for a given
depth distribution (NCRP, 1999).

#### Whole Body Effective Dose {#whole-body-effective-dose .unnumbered}

In order to calculate the whole-body dose from the free-in-air exposure
data, one must first convert exposure to dose in air by multiplying by a
factor of 0.875 rad/R. Then, to convert to dose in tissue and account
for shielding by the body, one must convert from rads in air to rem (or
in S.I. units, Gy to Sv). In this report we chose to follow the ICRP
guidelines (ICRP, 1991) and estimate the effective whole body dose that
weights the effects on various organs in a proscribed manner. The
UNSCEAR (1993) recommends a factor of 0.75 ± 0.05 to convert from Gy to
Sv for adults. This is similar to average values recommended by the ICRP
and others (NCRP, 1999). This factor of course varies with the energy of
the radiation and the orientation with respect to radiation incidence
(NCRP, 1999, Eckerman and Ryman, 1993). However, a value of 0.75 is a
reasonable average for fission products (NCRP, 1999). The net conversion
from exposure in air to effective dose is thus about 0.875 \* 0.75 =
0.66 for adults. Calculations using computer phantoms have indicated
that the effective dose to young children is about 30% higher (NCRP,
1999).

Thus the dose to adults exposed outdoors is about 2/3 of the outdoor
exposure. However, most people spend most of their time indoors and thus
their exposure is reduced greatly due to attenuation of the radiation by
building materials. The amount of shielding (i.e. the shielding factor)
will depend on the type of structure. In general, based on a review of
the available literature, it is estimated that heavily constructed
buildings made of brick or concrete will provide a shielding factor of
about 0.2 ± 20% (1 s,d,) while lightly constructed buildings will
provide a shielding factor of about 0.4. ± 20% (NCRP, 1999). These
estimates are fairly conservative and allow for a small amount of
radioactivity that may be tracked into the home from contamination of
shoes, etc. Assuming that on average most persons spend about 80% of
their time indoors (UNSCEAR, 1993; NCRP, 1999) with an average shielding
factor of 0.3, their whole body effective dose would be 0.66 \* (0.2 +
0.8 \* 0.3) = 0.29 x Outdoor exposure. However, the UNSCEAR estimated
that persons who work outdoor spend on average only 40% of their time
indoors and the most exposed outdoor worker spends only about 30% of
his/her time indoors. The NRC (1977) made a similar estimate of 40% of
time spent indoors for the maximum exposed individual. Assuming only 30%
indoors in a lightly shielded structure for the maximum exposed outdoor
worker, the dose to the most exposed individuals would be

0.66 \* (0.7 + 0.3 \* 0.4) = 0.54 x Outdoor exposure or almost twice
that of the average exposure. Conversely, the UNSCEAR (1993) estimated
indoor workers spend only about 10% of their time outdoors while other
estimates indicate some individuals spend even less time outdoors.
Assuming 5% as a reasonable estimate for the least exposed individual
living in a well shielded house and/or working in a well shielded
building, the minimum exposed individual would receive a dose of about
0.66 \* (0.05 + 0.95 \* 0.2) = 0.16 x outdoor exposure, or about ½ that
of the average dose.

Thus the actual dose to any individual can range by about a factor of
four depending on the amount of time spent outdoors and the type of
structure the individual lives and works in. The dose to children could
be about 30% higher than that for adults for the same fraction of time
outdoors. In this report, all calculations of dose are based on the
average exposure given above and estimates for any individual should be
adjusted up or down based on the above discussion.

Note that no additional uncertainty has been incorporated in the dose
estimates in this report above that for the uncertainty in the
underlying deposition density estimates that were used to estimate
exposure. However, using a S.D of ± 20% for the shielding factors, ±
0.05 for the conversion from rad to rem, and 0.8 ± 0.05 for the fraction
of time spent indoors by an average individual implies that the
uncertainty (one S.D.) in the average conversion from exposure to dose
of 0.3 is about 0.04, or about 10%. Even for the sum over all tests, the
uncertainty (GSD) in the outdoor exposure in a given county averages
about 1.3 (GSD). Thus, this additional uncertainty in converting to dose
can be ignored provided one adjusts their individual dose estimate for
time spent outdoors on average, particularly during the first few weeks
after each test.

**Beta Skin Dose**

All of the exposures and doses discussed above refer to exposure to
gamma radiation from the fission products deposited onto the ground.
However almost all of the gamma emitting radionuclides also emit beta
rays and a number of fission products emit beta rays but no gamma rays.
Because of their low penetrating power, beta rays are attenuated rapidly
in soil and even in air and thus contribute little to whole-body
radiation exposure (Eckerman and Ryman, 1993; NCRP, 1999). However beta
rays can contribute to the dose to skin, particularly in the days
immediately following fallout before the activity has penetrated more
deeply into the soil. Because the beta radiation is so sensitive to the
actual depth distribution in the soil, only a very crude estimate can be
made of the dose. Thus the beta skin dose has been estimated only for a
single test, HARRY. The variation in beta dose from test to test is
expected to be negligible compared to the variation due to variations in
depth distribution (penetration rate) in the soil.

Besides the beta radiation itself, the beta rays produce a small amount
of gamma radiation via bremsstrahlung (Eckerman and Ryman, 1993). This
gamma radiation, although only a small fraction of the energy of the
beta ray itself, can produce a small whole-body exposure and add to skin
dose. Furthermore, it is generally the only way a beta emitter can
irradiate body organs other than the skin. In order to account for both
beta radiation itself as well as the accompanying bremsstrahlung, we
have used the dose factors calculated by Eckerman and Ryman (1993) to
estimate doses to skin for the deposition densities of the various
fission products reported in Hicks (1991). Unfortunately, however,
Eckerman and Ryman (1993) do not separate out beta and gamma dose
contributions in their tabulated results and also did not calculate
values for exponentially decreasing concentrations in soil. Thus the
beta dose for beta-gamma emitters for a 1 cm slab source was inferred by
plotting their doses for pure beta emitters versus their total energy of
emitted betas and using this curve to estimate the beta doses from
beta-gamma emitters. The dose for a source with a 0.1-cm relaxation
length, corresponding to the distribution used for gamma rays for the
first 20 days, was then estimated. For this estimate, it was assumed
that all the activity is contained in a 0.144 cm thick slab,
corresponding to the mean depth of a 0.1 cm relaxation length
exponential distribution and that any activity from depths greater than
that would not contribute significantly due to attenuation. Thus the
skin dose values from Eckerman and Ryman (1993) for a 1-cm slab with 1
Bq/cm^3^ were multiplied by a factor of 5.3 to correspond to the
concentration in a 0.144-cm slab for a deposition density of 1 nCi/m^2^
with a 0.1 cm relaxation length.

The beta skin dose from fallout distributed with a 0.1-cm relaxation
length was then calculated to be about 25-50% of that from a plane
source on the soil surface, depending on the age of the fallout. The
early fallout contains a greater fraction of higher energy beta rays and
thus the attenuation in soil is lower. The results of these calculations
are presented in the next section and compared to the gamma ray exposure
results.

**Results**

##### Fallout Deposition {#fallout-deposition .unnumbered}

The total deposition density of Cs-137 from all NTS tests examined
through 1962 is shown in Figure 1. The pattern of deposition is similar
to that for I-131, shown in Figure 2 (from NCI, 1997) although, due to
its long half life, the drop-off in activity in the eastern U.S. is less
than that for I-131. Deposition densities range from less than 5
mCI/km^2^ in the western and northwestern states to over 20 near the
NTS. As for the I-131 deposition, the regional and local variations are
due to variations in precipitation, which is the main fallout mechanism
at distances remote from the test site. The well documented elevated
region in northern New York State was due to heavy thunderstorm activity
during passage of the cloud from shot SIMON in April, 1953 (NCI, 1997;
Beck et al., 1990). The deposition density patterns for most of the
other radionuclides covered in this report were in general intermediate
to the patterns for Cs and I, with any differences reflected by the
differences in respective half lives.

The deposition density data for each test for all covered nuclides is
contained in the database accompanying this report. However, the
patterns for Sr-90 and Pu-239+240 vary somewhat from those for Cs-137
and I-131due to the differences in Sr and Pu production as a function of
the device fuel. Figure 3 shows the ratio of total Cs-137 to total
Sr-90..Figure 4 is for the ratio of Cs-137 to Pu-239+240. Note that the
Cs to Sr ratio varies from about 0.8 to 1.9 with relatively low Sr
deposition in Idaho, western Montana, western Nevada and the S.E. states
and relatively higher Sr deposition relative to Cs in areas of the
Midwest. The differences, of course, reflect the fact that the fallout
in different regions resulted from different test(s). The Cs/Pu ratios,
shown in Figure 3 vary from 3 to over 50. The highest relative Pu
deposition was in counties near the NTS. However, areas in the mountain
states, eastern NM and the Midwest exhibited generally low relative Pu
deposition. For most of the country, the Cs to Pu activity ratio was
about 10-20. As discussed previously, the Pu estimates in this report
for any particular county are very uncertain and should be viewed only
as illustrative of the variations across the country due to the varying
tracks of Pu-fueled tests versus U-235-fueled tests. The number of
counties within each range is shown in parenthesis in the figure
captions.

Figure 5 shows the fraction of the total Cs-137 deposition in the
continental U.S. resulting from each test series. The 1957 Plumbbob
series deposited 35% of the total Cs followed by the 1953 Upshot
Knothole series (23%). Of course the fraction of the total deposition in
a particular year for any particular county will differ from this
distribution due to the varying fallout tracks during different years.
(The maps shown later of external exposure versus year reflect the
relative annual depositions of fission products in each area). The ten
tests depositing the most Cs in the continental U.S. are shown in Figure
6, while Figure 7 shows comparable data for the population-weighted
deposition density.

Two tests from the 1953 UPSHOT-KNOTHOLE series deposited the most Cs-137
(SIMON and HARRY). HARRY also deposited the most I-131 (NCI, 1997). The
comparable plot for the tests resulting in the highest
population-weighted deposition density differs somewhat from the total
deposition. Foe example, HARRY's impact on a population-weighted basis
was much less than for total deposition, reflecting the fact that the
fallout tracks and deposition patterns for each test differed, sometimes
significantly (NCI, 1997; Beck et al., 1990).

The total amount of Cs-137 deposited in the continental U.S. from all
tests was 62500 Ci. The total deposition for a number of other selected
radionuclides is shown in Table 6.

The total deposition density was calculated for several radionuclides in
order to compare with the deposition from "global" fallout as reported
by UNSCEAR (1993). For this purpose, the calculated values for each
county were weighted by population and then summed. Because of the sharp
gradations in deposition from west to east, and the higher populations
in the eastern U.S., these population-weighted values are slightly less
than the mean unweighted deposition obtained by dividing the total
deposition by the total area of the continental U.S. However, they are a
fairer indicator of the impact the deposition had with respect to both
external and internal population doses. The resulting
population-weighted deposition densities for the U.S. are given in Table
6 and compared with corresponding estimates by UNSCEAR for the 40-50
degree latitude band of the northern hemisphere

[Table 6: Total deposition and population-weighted mean deposition
density of selected]{.underline} [radionuclides for NTS fallout and
"global" fallout.]{.underline}

Nuclide Total Deposition Population weighted Deposition density (kCi)
(nCi m^2^)

[NTS NTS "global fallout"\*\*]{.underline}

Cs-137 62.5 6.9 140

Sr-90 49.2 5.3 87

Zr-95 5900 680 1030

Ru-103 11500 1240 760

Ba-140 37600 3900 620

Ce-141 13500 1460 570

Ce-144 1070 123 1300

Ru-106 635 71 650

Sr-89 9000 980 540

I-131 40100 5200 513

Pu-239+240 3.6# \~0.42 1.6

Pu-241 14.6 \~1.6 20

\*\*f*or 40-50 degree latitude band, \# About 5% of total is from the
decay of Np-239.*

Thus for the long-lived radionuclides, NTS fallout contributed only
about 5% of the total deposition. The deposition of short-lived
radionuclides such as Sr-89, Ba-140 and I-131 was several times that of
"global" fallout. These results are consistent with the fact that
although the total fission yield of NTS tests was only about 1 MT,
compared to about 150 MT for tests outside the U.S., most of the debris
from the large thermonuclear tests outside the U.S. was injected into
the stratosphere. According to the UNSCEAR (1993), the average residence
time for this stratospheric debris before re-entering the troposphere
and depositing is about 1 y. This delay in fallout coupled with a more
uniform deposition over the entire globe accounts for the reduced impact
of global fallout and in particular the very much-reduced short-lived
activity relative to the amounts produced.

Another factor contributing to the greater deposition per unit yield in
the continental U.S. of NTS tests is the fact that tests detonated near
the ground, either on the surface or from relatively low towers, deposit
a large fraction of their debris locally and regionally compared to
tests detonated higher in the atmosphere. Figure 8 compares the
cumulative Cs-137 deposition versus distance from the NTS as a fraction
of that produced for various types of tests. Figure 9 compares the
deposition as a fraction of the total deposited in the U.S. From Figure
8, one sees that less than 10% of the activity produced in an air burst
deposits within 4,400 km (or within the continental U.S.) compared to
about 45% for tower and surface shots. Balloon-borne devices deposited
30% in the U.S., less than tower shots but much more than air bursts.
(The height of detonation for balloon shots was generally on the order
of 500 m compared to \~100-200 m for tower shots (Beck, 1984)). For all
NTS tests, 34% of the Cs-137 produced deposited in the continental U.S.
In terms of the total deposited in the U.S., all types of tests
deposited the same approximate fraction of their total U.S. deposition
at distances greater than 2,000 km. However, tower shots, as expected,
deposited a greater fraction very close to the NTS, while air bursts
seemed to deposit a greater fraction from 1,500-2,500 km.

Overall, air bursts deposited only about 8% of the total activity
produced within the continental U.S., consistent with the UNSCEAR
estimate of an average tropospheric residence time of 30 d. assuming a
cross-country transit time of about 4 d on average.

The estimates of total deposition and fractional deposition discussed
above of course rely upon the accuracy of the underlying I-131
deposition densities calculated by interpolating a relatively small
number of gummed film measurements and weighting interpolated values by
measured precipitation (NCI, 1997). However, most of the random
uncertainty in total deposition is averaged out when summing over a
large number of tests, days per test, and counties. The calculated
propagated uncertainty in total deposition is less than 5% (GSD \<
1.05). This assumes of course that there is no large systematic error
and that the daily deposition estimates are not correlated. The values
for a particular day are correlated with values for nearby counties
since that is the basis of the kriging method used (see NCI, 1997),
however, results from one day to another and one test to another should
not be correlated.

**Exposure and Dose**

The geographical distribution of total whole-body effective dose from
all NTS tests for a typically exposed individual (80% indoors, 0.3
shielding factor) is shown in Figure 10. The specific mean and GM
free-in-air exposures for each county for each test, year, and total NTS
are included in the database that accompanies this report. The
interested reader can estimate his/her exposure and dose by multiplying
by the appropriate indoor/outdoor and shielding factor correction factor
as discussed in the previous section. As expected, the dose pattern is
similar to the I-131 deposition pattern presented in NCI (1997) since
the exposure rate is closely related to the deposition of short-lived
radionuclides. The most exposed were individuals who lived in states
immediately downwind from the NTS. However, pockets of higher and lower
exposures occurred throughout the U.S. as a result of the uneven
deposition of fallout and the variation in tracks of the many tests that
contributed. The geographical distribution of doses varied significantly
from year to year as shown in Figures 11-16. As can be seen, the 1952
TUMBLER-SNAPPER series impacted areas to the north of the NTS more than
did the tests in other years, while the fallout from the 1955 TEAPOT
series was concentrated in the center of the U.S. The 1957 Plumbbob
series accounted for much of the exposure to residents of ND, MN and
surrounding areas.

The relative impact of various test series was investigated by
calculating the population exposure, i.e. the product of the exposure
for a given county multiplied by its population, and then summing over
all counties. The population exposure versus year of exposure is given
in Table 7.

[Table 7: Population exposure and per capita exposure versus year of
exposure.]{.underline}

####### Year Annual 50 y Committed per capita {#year-annual-50-y-committed-per-capita .unnumbered}

\-\-\-\-\-\--10^6^ person-R\-\-\-\-\-\-\-\-\-- mR

1951 2180 2250 13

1952 5040 5310 31

1953 6320 6630 39

1954\* 56 0.34

1955 3930 4170 24

1956\* 37 0.23

1957 6730 7530 41

1958\* 275 1.7

1962 1570 1640 9.7

Total NTS 26400 27900 162 (49 mrem), 171 committed

*\*From previous years fallout.*

The uncertainty in the above calculated population exposures was less
than 1.1 (GSD) for all years except 1951 and 1962. The GSD for 1951 was
1.2 due to the large uncertainty in the I-131 deposition density
estimates for some of the early Ranger series tests. The GSD for the
1962 fallout, which was due mainly to the SEDAN cratering shot, is very
large, 1.8, again due to very uncertain estimates of I-131 deposition.
The population exposure for each year includes that from fallout in that
year plus from fallout in the previous year, if any. The per capita
exposure of 162 mR corresponds to an average whole body effective dose
of about 0.5 mSv (50 mrem), for the years of testing, about what an
average person would receive from natural background radiation in 1-2
years depending on the area of the country. Residents of some counties
near the NTS received doses in excess of 3 mSv (300 mrem) while
residents of the extreme Western and Northwestern states and some
Midwestern counties received average doses less than 0.25 mSv (25 mrem).
The committed (50 y) dose from all NTS tests is about 5 % higher than
the dose received during the testing years. In contrast, the UNSCEAR,
1993, has estimated the population-weighted per capita dose from
external radiation from "global" fallout in the latitude band 40-50
degrees to be about 1 mSv. Twenty-five tests accounted for over 80% of
the population exposure but no single test accounted for greater than
7%. The ten top contributors that account for about 50% of the
population exposure are shown in Figure 17. Again, the impact of the
SEDAN shot is very uncertain (GSD = 1.8) while the GSD of the population
exposures for the other 9 tests are all in the range 1.1-1.3.

A large number of fission products are produced in a nuclear explosion.
However, only a relatively few account for most of the external
exposure. Different radionuclides contribute significantly to the
exposure rate at different times and thus determination of the most
important radionuclides with respect to total exposure depends on the
time of arrival of the fallout. Table 8 shows the largest contributors
to total integrated exposure (% of total integrated exposure from
nuclide and decay products) for several different times of fallout
arrival. The data are for shot HARRY but vary only slightly from shot to
shot with volatile nuclide contribution being greater for tower and
surface shots as opposed to air bursts. However, as shown earlier, the
surface and tower shots account for most of the radiation exposure to
the population of the continental U.S. As can be seen, at early arrival
times the short-lived iodine isotopes contribute relatively more to the
exposure while after a few days, I-132, Ba-140, Zr-Nb-95 and Ru-103
dominate. I-132 is a major contributor even for later arrival times.
Note that by contrast, most of the external dose from "global" fallout
was due to the longer-lived nuclides, with Cs-137 accounting for about
50% of the exposure and Ru-103, Ru-106, Ce-Pr-144 and Zr-Nb-95 most of
the remainder (UNSCEAR, 1993). In contrast, these nuclides contribute
only small amounts to the integral dose from NTS fallout.

Figures 18 through 22 show the fraction of the total dose from all NTS
tests that resulted from Te-I-132, Ba-La-140, Zr-Nb-95, Np-239, and
Ru-103, respectively. Note that as expected from the dependence on
arrival time shown in Table 8, the shorter-lived nuclides such as Np-239
(2.4 d) have a larger impact close to the NTS while the relative
contribution of nuclides with relatively long half lives such as Zr-95
(64 d) is much greater at large distances from the NTS. Because of this
strong dependence on time of fallout arrival, the radionuclide
composition accounting for the total exposure varies significantly with
distance from the NTS.

[Table 8: Percentage of total integral exposure contributed by various
fission products as a function of fallout arrival time]{.underline}

TOA= [0.5 d]{.underline} [2.5d]{.underline} [5d]{.underline}

######## Nuclide (%) (%) (%) {#nuclide .unnumbered}

Te-I-132 23 27 20

Ba-La-140 21 35 43

I-133 13 3 \<1

Np-239 6 6 4

Zr-Nb-95 6 10 14

Zr-Nb-97, 97m 6 1 \<1

I-135 5 \<1 \<1

Ru-103 3 6 7

I-131 3 4 4

The doses discussed above are from gamma irradiation. Table 9 presents
the estimates of the ratio of beta skin dose to whole body gamma dose
outdoors for shot HARRY as a function of time of arrival of fallout.
This ratio is about 2 for fallout shortly after the test but falls to
about 1.0 after a few days. The ratio of dose rates is about 5 at early
times and falls to about 1 at about 5d. Note that it has been assumed
that the beta dose can be neglected after 20 days. The activity is then
assumed to be distributed with a relaxation length of 1 cm, deep enough
to reduce the beta-ray flux to a negligible level. The beta dose
estimates determined here are in reasonable agreement with previous
results. For example the ICRU (1977) estimated the beta skin dose rate
from a plane source of fission products to be about 8-16 times the total
effective dose. The ratio of dose rates for a 0.1 cm relaxation length
for early arrival times is about 3-5 from Table 9. Dose rate ratios
calculated for a plane source for the same beta spectrum (HARRY) ranged
from about 7-11 over the first 2-3 days, with the higher value, that
likely corresponds better to the beta ray spectrum assumed by the ICRU,
corresponding to earlier arrival times. Only a relatively few nuclides
emitting higher energy beta rays contribute significantly to the dose:
Rb-88, Sr-91, Y-92, Y-93, Sb-128, Te-129, I-132. I-133, I-135, Ce-143,
and Pr-145. The relative contributions of each to the total dose
depended on fallout time-of -arrival.

The actual impact of beta exposure is of course even less than the
ratios in Table 9. The average individual would be exposed to beta
radiation only for the 20% of time spent outdoors, resulting in an
actual beta skin dose to gamma whole body dose ratio of about 0.2-0.4.
Furthermore, since the radio-sensitivity of the skin is generally
accepted to be much lower than for other organs, even the beta dose to
the most exposed individuals who spend up to 70% of their time outdoors
can be considered insignificant compared to their whole-body gamma
exposure.

Two sources of beta radiation exposure might be significant in some
cases. One is the direct deposition of radioactivity onto the skin
during cloud passage. The second is contamination to the skin from
children playing in contaminated soil, both from soil adhering to the
skin as well as due to a closer proximity to the source. The former case
is only of significance to individuals living close to the test site and
was considered by Henderson and Smale (1990), in the ORERP study.
Neglecting the dose from soil adhering to the skin, the dose to a child
playing on the ground would probably be about a factor of two higher
than that to a standing adult due to the closer proximity to the source
plane. However, this would still probably not constitute a significant
exposure. A more significant exposure route would likely be direct
ingestion of soil (NCRP, 1999).

[Table 9: Beta ray skin dose divided by whole body gamma dose as a
function of fallout time of arrival-shot HARRY]{.underline}

[Time of arrival, d dose rate ratio integrated dose ratio\*]{.underline}

0.5 4.8 1.9

1.5 3.0 1.3

2.5 1.5 1.1

5.5 1.1 0.8

10.0 0.7 0.4

*\*100% outdoors*

**Summary and Conclusions**

Fallout from atmospheric tests at the NTS resulted in an average
external radiation exposure of about 0.5 mSv to the population of the
U.S., about half of that incurred from "global" fallout from the
large-scale testing outside the U.S. However, residents in the states
immediately downwind from the NTS received much higher exposures while
the exposures in the Western and Northwestern U.S. and some areas of the
Midwest and Southeast were much less than the average. Most of this
exposure occurred with the first 3 weeks of each test and was due to
relatively short-lived radionuclides. In contrast, the exposure from
"global" fallout occurred over a much greater span of time (1952-62) and
primarily from a few long-lived radionuclides. Thus the dose rate was
more uniform with time. Almost the entire whole-body effective dose to
the population was from gamma rays emitted by fission products deposited
on the ground. The actual dose received by any individual depended on
the fraction of time he/she spent outdoors during the first few weeks
after fallout and the degree of shielding provided by his/her dwelling.
The most exposed individuals at any particular location would have been
outdoor workers or others who spent most of their day outdoors. Beta
radiation from fission products in the surface soil did result in
additional dose to the skin when outdoors. However, this contribution
was not large enough to be considered an important component of total
fallout radiation exposure except perhaps for children who played in the
soil for significant intervals of time.

The deposition of fission products contributed to internal radiation
exposure via ingestion as well as external exposure. The deposition
densities of all nuclides that could contribute significantly to
ingestion doses were calculated for this study although the internal
doses via ingestion will be treated in a separate report. It is
noteworthy that the deposition of long-lived nuclides was much less than
from global fallout, while the deposition of short-lived radionuclides
was generally higher. About 1/3 of the fission products produced by the
roughly 1 MT of NTS explosions was deposited within the continental U.S.
Surface shots and shots conducted on towers produced much more fallout
in the U.S. per unit yield than air bursts.

The annex to this report, in the form of Excel spreadsheet files, gives
the calculated deposition densities of all the radionuclides considered
for each test for each county of the U.S. The free-in-air exposure
resulting from each test and test series is also tabulated for each
county. By accessing the data for their particular county of residence
for any given year(s) and applying the appropriate correction factor to
convert from exposure to dose by adjusting for the actual fraction of
time spent outdoors, the interested reader can estimate his/her whole
body dose from NTS fallout.

Three appendices follow. Appendix 1 provides a detailed example of the
calculation of deposition density and exposure for a representative
county to illustrate the calculational procedure. The other two
appendices are included to satisfy the scope of work given in the
introduction of this report. The first is a bibliography of additional
references on weapons testing in Nevada and assessments thereof. The
second discusses the need for declassification of documents that might
improve our ability to assess the impact of fallout from weapons
testing, both within the U.S. and outside the U.S., on the American
population.

**References**

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exposure and collective external gamma exposure from testing at the
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Physics **51**:35-51; 1986.

Beck, H.L., Environmental gamma radiation from deposited fission
products, 1960-1964. Health Physics **12**:313-322, 1966.

Beck, H.L. Exposure rate conversion factors for radionuclides deposited
on the ground. US Dept. of Energy report EML-378. NTIS, Springfield, VA,
1980.

Beck, H.L. Estimates of fallout from Nevada weapons testing in the
western United States based on gummed-film monitoring data. U.S.
Department of Energy report EML-433. Environmental Measurements
Laboratory, New York, October 1984.

Beck, H.L. and Krey, P.W. Cesium-137 inventories in undisturbed Utah
soils-interim report on radionuclides in soils of populated areas. .
U.S. Department of Energy report EML-375. . Environmental Measurements
Laboratory, New York, June 1980.

Beck, H.L., I.K. Helfer, A. Bouville, and M. Dreicer. Estimates of
fallout in the western U.S. from Nevada weapons testing based on
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Beck, H.L. Reconstructing source terms from environmental data.
Proceedings of the Thirty-First Annual Meeting of the National Council
on Radiation Protection and Measurements. Proceedings No. 17, pp. 79-91.
NCRP, Bethesda, MD, 1996.

Beck, H.L. and L.R. Anspaugh. Development of the County Data Base:
Estimates of exposure rates and times of arrival of fallout in the ORERP
Phase-II area. Comparison with cumulative deposition-density estimates
based on analyses of retrospective and historical soil samples. U.S.
Department of Energy report DOE/NV-320; 1991.

Church, B.W.; Wheeler, D.L.; Campbell, C.M.; Nutley, R.V.; Anspaugh,
L.R. Overview of the Department of Energy\'s Off-Site Radiation Exposure
Review Project (ORERP). Health Phys. **59**:503-510; 1990.

Eckerman, K. and Ryman, J.C. Dose Coefficients for external exposure to
radionuclides distributed in air, water and soil, Federal Guidance
report 12. USEPA, Washington; 1993.

England, T.R. and Ryder, B.F., Evaluation and Compilation of Fission
Product Yields, 1993. Las Alamos National Laboratory report
LA-UR-94-3106 (ENDF-349); 1994.

Gale, H.J., Humphrey's, D.L.O., and Fisher, E.M.R. The weathering of
caesium 137 in Soil. Nature **201**, 257.;1964.

Henderson, R.W.; Smale, R.F. External exposure estimates for individuals
near the Nevada Test Site. Health Phys. **59**(5):715-721; 1990.

Hicks, H.G. Results of calculations of external radiation exposure rates
from fallout and the related radionuclide composition. Livermore, CA:
Lawrence Livermore National Laboratory; UCRL-53152, parts 1-8; 1981.

Hicks, H.G. Calculation of the concentration of any radionuclide
deposited on the ground by off-site fallout from a nuclear detonation.
Health Phys. 42:585-600; 1982.

Hicks, H.G., Report on Plutonium Isotopic Ratios, Reporters transcript
of ninth dose assessment Advisory group Meeting, Feb. 17, 1984, Vol II,
USDOE Nevada Operations Office, 1984 (CIC #41989); 1984.

Hicks, H.G. Additional calculations of radionuclide production following
nuclear explosions and Pu isotopic ratios for Nevada Test Site events.
Health Phys. **59**(5):515-523; 1990.

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ICRU. Dosimetry of External Beta Rays for Radiation Protection. Report
of the International Commission on Radiation Units and Measurements,
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Jacob,P., Paretzke, H.G., Rosenbaum, H. and Zankl, M. "Effective dose
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Radiat. Prot. Dos. **14** (4), 299-310; 1986.

Krey, P.W. and Beck, H.L. The distribution throughout Utah of 137Cs and
239+240Pu from Nevada Test Site detonations. USDOE report EML-400. NTIS;
1981.

Likhtariov, I, Kovgan, L.,Novak, D., Vavilov. S, Jacob, P, and Paretzke,
H.G.. Effective doses due to external radiation from the Chernobyl
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Miller, K.M., Kuiper, J.L. and Helfer, I.K. Cs-137 fallout depth
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for individuals. Health Phys. **59**:693-713; 1990.

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**Appendix 1: Example of Calculation Procedure**

In this appendix, the calculation of the deposition density of Ba-140
and of Cs-137 for a particular arbitrarily chosen county, St. Louis
(FIPS=29189), from shot HARRY, 5/19/53, is shown in detail. The
calculation of the total external exposure for St. Louis County
resulting from shot HARRY is also illustrated.

DEPOSITION DENSITY

All calculations start with the measured effective I-131 reported by the
NCI (1997). These measured I-131 values (mCi/km^2^) for St. Louis County
for various days after the detonation (TOA) are shown in the second
column of Table A1. As discussed in the text a TOA of 1.5 d refers to
fallout on the second day after the detonation or in this case on
5/20/53, etc. The corresponding GSD reported in NCI (1997) is given in
column 3. The effective I-131, denoted as I-131\*, is just the measured
value decayed back to H+12 h (column 5). The effective I-131 includes
the contributions of I-131 that will subsequently grow in from Te-131
and Te-131m since these contributions are included in the reported
measured I-131 (NCI, 1997).

In order to calculate the corresponding Ba-140 and Cs-137 for each day
with I-131 deposition it is necessary to know the ratios of
Ba-140/I-131\* for each of these days. These values, from Hicks (1981)
are given in columns 5 and 6, respectively. Note that the values in the
Hicks Tables (Ci/km^2^) for all nuclides are normalized to a unit
exposure rate of 1 mR/h at H+12 h. In each case the value of Ba-140 or
Cs-137 for the particular TOA was obtained from the Hicks (1981) Table
for test HARRY and divided by the corresponding I-131\* H+12 h value
from Hicks for test HARRY, .819 mCi/km^2^. The latter value was obtained
from the tabulated values for test HARRY for I-131, Te-131, Te-131m at
H+12 h (I-131\* =\[ I-131 \*193 h + Te-131m \* 30 h + Te-131 \* 0.417
h\] / 193h ) and represents the total I-131 at H+12h plus the I-131 that
will subsequently grow in from Te-131 and Te-131m.

[Table A1: Measured I-131 deposition density (mCi/km^2^), ratios of
Ba-140 and Cs-137 to I-131\*, and calculated Ba-140 and Cs-137
deposition densities (mCi/km^2^]{.underline}).

  ---------------- --------------------- ------------------- ----------------------- -------------------------- ---------------------- -------------------------- ----------------------
                                                                                                                                                                  

  [TOA,            [I-131]{.underline}   [GSD]{.underline}   [I-131\*]{.underline}   [Ba-140/I\*]{.underline}   [Ba-140]{.underline}   [Cs-137/I\*]{.underline}   [Cs-137]{.underline}
  d]{.underline}                                                                                                                                                  

  0.25             0                                                                 0.85                                              0.00121                    

  0.5              0                                                                 0.83                                              0.00121                    

  1.5              20                    2                   21.8                    0.78                       17.0                   0.00121                    0.026

  2.5              16                    2                   19.0                    0.74                       14.1                   0.00121                    0.023

  3.5              50                    2.5                 64.8                    0.70                       45.3                   0.00121                    0.078

  4.5              8                     2                   11.3                    0.66                       7.5                    0.00121                    0.014

  5.5              16                    1.5                 24.6                    0.63                       15.5                   0.00121                    0.030

  6.5              16                    1.5                 26.8                    0.59                       15.8                   0.00121                    0.032

  7.5              0                                                                 0.57                                              0.00121                    

  8.5              0                                                                 0.54                                              0.00121                    

  9.5              0                                                                 0.51                                              0.00121                    

  10.5             0                                                                 0.48                                              0.00121                    
  ---------------- --------------------- ------------------- ----------------------- -------------------------- ---------------------- -------------------------- ----------------------

Multiplying the Ba-140/I-131\* and Cs-137/I-131\* by the measured
I-131\* provides the estimated GM deposition densities of Ba-140 and
Cs-137 for each day of fallout. Since the uncertainty in the Hicks
(1981) ratios of deposition densities is assumed to be minor compared to
the larger uncertainty in the measured deposition densities, the GSD for
Ba-140 and Cs-137 are assumed to be the same as that for the
corresponding measured I-131.

In order to calculate the total Ba-140 and Cs-137 deposition densities
for this county from shot HARRY, one must sum the daily values. However,
one cannot sum GM values so one must first convert each daily GM to the
corresponding mean. As discussed in NCI (1997), the conversion is given
by mean, m = GM \* exp (0.5 \* s^2)^ where s^2^ = ln (GSD). The
corresponding variance, var = m^2^ = \[exp (s^2^ ) --1\]. Table A2 gives
the calculated means and variances for the days with fallout.

[Table A2: mean and total deposition densities (mCi/km^2^).]{.underline}

  ------------------- ------------------ -------------------- -------------------- ------------------ ---------------------- ------------------------
                      Ba-140                                                       Cs-137                                    

  [TOA]{.underline}   [GM]{.underline}   [mean]{.underline}   [var]{.underline}    [GM]{.underline}   [mean]{.underline}     [var]{.underline}

  1.5                 17.0               21.6                 288.4                0.0264             0.0335                 0.000694

  2.5                 14.1               17.9                 197.4                0.0230             0.0292                 0.000528

  3.5                 45.3               69.0                 6258                 0.0784             0.119                  0.0187

  4.5                 7.45               9.48                 55.4                 0.0137             0.0174                 0.000186

  5.5                 15.5               16.8                 50.7                 0.0298             0.0323                 0.000187

  6.5                 15.8               [17.2]{.underline}   [52.8]{.underline}   0.0325             [0.0353]{.underline}   [0.000222]{.underline}

  SUM:                                   152                  6903                                    0.267                  0.0205

  GM =                                   134                                                          0.235                  

  GSD =                                  1.7                                                          1.7                    
  ------------------- ------------------ -------------------- -------------------- ------------------ ---------------------- ------------------------

The mean of the total deposition density of Ba-140 is thus 152 mCi/km^2^
with a variance of 6003. As discussed in NCI (1997), the sum of
lognormally-distributed distributions can themselves be assumed to be
approximately lognormally distributed with a GM given by GM = m / SQRT
\[1 + var / m^2^ \] and a GSD given by GSD = exp \[SQRT (ln {1 + var /
m^2^ )}. Using these equations, the GM Ba-140 deposition density for
this county for shot HARRY is thus 134 mCi/km^2^ with a GSD of 1.7. The
corresponding Cs-137 deposition density is 0.235 with a GSD of also 1.7.

In a similar manner, the deposition densities resulting from all other
tests conducted in 1953 were calculated and the total Ba-140 and Cs-137
deposition densities from all 1953 (UPSHOT-KNOTHOLE) tests obtained by
summing the **means and variances** of the individual test results. To
obtain the total deposition density from all NTS tests, the means and
variances calculated for each test series were summed. These sums are
provided in the database that accompanies this report along with the
calculated conversions to GM and GSD for each test, test series, and NTS
totals.

**Exposure**

The calculation of free-in-air exposure again starts with the measured
I-131\* values and the I-131\* value per mR/h at H+12 h (= 819
mCi/km^2^) for HARRY given in Hicks (1981). The exposure rate at any
time t is given by the deposition density at time t in mCi/km^2^
multiplied by a dose rate conversion factor R / h per mCi /km^2^ taken
from Beck (1980). As discussed in the text, these conversion factors are
a function of the assumed depth distribution. For t \< 20 d, a depth
distribution with a relaxation length of 0.1 cm was assumed. This was
the value used in Hicks (1981) for all times. For t \> 20 d \< 200 d, a
relaxation length of 1 cm was assumed in this report, and for \> 200 d,
a relaxation length of 3 cm. The conversion factors for Ba-140, La-140
and Cs-137 for each relaxation length are given below:

[Table A3: Conversion factors from deposition density to exposure rate,
R / h per mCi /km^2^]{.underline}

[Nuclide RL =0.1 cm RL- 1 cm RL = 3 cm]{.underline}

Ba-140 2.41E-03 1.62E-03 1.10E-03

La-140 3.33E-02 2.28E-02 1.60E-02

Cs-137 9.28E-03 6.15E-03 4.32E-03

In order to calculate the total exposure rate as a function of time from
TOA to the end of the year, and to 50 y after detonation for a
particular test, it is necessary to sum the exposure rates per unit
I-131\* from each of a large number of radionuclides contributing to the
total exposure rate at any particular time, multiply this total by the
measured I-131\* deposition density, and then integrate the total from
all nuclides over the period of interest. For the first 20 d after
detonation, a very large number of nuclides contribute to the exposure
rate (\>100). Since Hicks already calculated the total exposure rate per
unit I-131\* for this period for a range of t, it was not necessary to
attempt to recalculate and tabulate the individual radionuclide exposure
rates for this period. They can be obtained directly from the Hicks
(1981) tables if desired. The exposure rates versus time per unit
I-131\* for the first 20 d as reported in Hicks (1981) for shot Harry
are given below (The reported exposure rates have been normalized to
unit deposition density of I-131\* by dividing by 819.

[Table A4: Exposure rate versus time of arrival for test HARRY per mCi
/km^2^ I-131\*]{.underline}

  ----------------------------------- -----------------------------------
  [TOA (h)]{.underline}               [mR/h]{.underline}

  18                                  7.84E-04

  21                                  6.57E-04

  24                                  5.54E-04

  48                                  2.50E-04

  120                                 9.83E-05

  240                                 4.54E-05

  480                                 1.81E-05
  ----------------------------------- -----------------------------------

In order to calculate the total exposure from any particular time of
arrival (TOA) to 20 d after detonation, the exposure rates in Table A4
were fit to a function of the form a t^-b^ for the period 12 h to 20 d
(480 h). The results of this fit for test HARRY was a = 5.62E-04;
b=-1.0958 with a correlation coefficient r^2^ of 0.9995. The integral
from any time TOA to 20 d is then a t ^--b^ dt = \[0.4602/ (0.0958)\]
\[TOA^-0.0958^ --20^-0.0958^\]. The resultant total integral exposures
from TOA to 20 d for various TOA are given in the second column of Table
A5 below. Note that this formulation actually assumes a 0.1-cm
relaxation length for times TOA to 20 d rather than for a period
totaling 20 d after deposition. This is reasonable, however. As the time
of arrival of fallout increases due to increasing distance of the
fallout cloud from the NTS, a greater fraction of the deposition is due
to washout from precipitation (NCI, 1997). This wet deposition resulted
in greater penetration into the soil than that from the dry deposition
that occurred near the NTS at early arrival times.

The exposure rate from 20 d post detonation to 200 d could not be taken
from the Hicks (1981) tables directly since we use an exposure rate
conversion factor that assumes a 1- cm relaxation length. However, the
number of radionuclides contributing significantly to the total exposure
during this period is much smaller (about 24). It was thus possible to
use the actual time variation of the deposition density for each of
these radionuclides multiplied by the appropriate dose rate factor from
Beck (1980) to calculate the integral exposure for each for the desired
interval. For example: the exposure rate for Cs-137 for the period 20 d
to 200 d is given by:

I (t) R/d = Cs(20 d) mCi /km^2^ \* 6.15E-03 R / h per mCi /km^2^ \* 24
h/d \* exp(- \* (t-20 d) ),

where Cs(20 d) is the deposition density of Cs-137 (per unit I-131\*) at
20 d after detonation, from Hicks (1981) and  = ln (2) / T~1/2~.

The integral from 20 d to 200 d is thus:

I (mR) = Cs (20 d) \* 6.15E-03 \* 24 \* 1/ \* \[1 --exp (-180 \* )\]/
1000.

The half life of Cs-137 is 11000 d (Table 2). The exposure rates of the
other radionuclides contributing to the exposure rate during this period
were calculated in a similar manner. Note that for a few radionuclides
that grow in from precursors (e.g. Nb-95 from Zr-95), the activity
versus time is a function of the parent activity and the analytical
relationship is sometimes more complicated than that for a single
radionuclide. The daughter to parent activity for these nuclides is
given by D/P =  (T~1/2\ p~)/(T~1/2p~ - T~1/2\ d~) \* \[1 -- exp (-~d~
-- ~p~) t\], where  is the number of daughter atoms produced per
parent decay and the subscripts p and d stand for parent and daughter,
respectively. This equation is easily integrated to provide the integral
exposure of the daughter activity in a manner similar to that for the
parent as described above. (If the daughter half life is short compared
to that of the parent the activity of the daughter is approximately
equal to that of the parent at all times, and the exposure rate is just
the parent activity multiplied by the exposure rate conversion factor
for the daughter).

Since HARRY was detonated on the 139^th^ day of the year (May 23), there
were 226 d remaining in the year 1953. The total exposure for the year
from a deposit on day TOA was thus the sum of the exposures from TOA-20
d, 20-200d and 200-226 d. For the last 26 days, the calculation was
similar to that for 20-200 d except that the integration was from 200 d
to 226 d and the deposition densities from 200-226 d were multiplied by
the exposure rate conversion factors for a 3 cm relaxation length,
rather than for a 1-cm relaxation length. For the year 1954, and for the
remainder of the 50 y period for which the exposure was calculated, only
a few radionuclides contributed to the exposure. Again, the integrated
doses were calculated individually for each as shown above for Cs-137,
integrating over the appropriate time interval.

Table A5 gives the final integrated exposure for each of the time
intervals of interest, TOA-20 d, 20-200 d, the entire year (1953), 1954,
1955 -- 50 Y, and the total = TOA - 50 Y. By multiplying each of these
normalized exposure values by the corresponding measured I-131\* for
each day with fallout (from Table A1), one obtains the mean and GM
exposures for St. Louis County for test HARRY shown in Table A6, along
with the corresponding variances and GSDs. Again, the means are
calculated from the measured GM, as described previously for the
deposition density calculations, and then summed to obtain the total
exposure resulting from all days of fallout. The total exposure from all
tests in the year 1953, and from all NTS tests, was calculated in a
similar manner by summing the mean exposures from each test.

Table A5: Integral exposure from time of arrival to 20 d, 20 d to end of
year, 1953, 1954, TOA-50 y, per unit I-131\* deposition density (mR per
mCi/km2)

  ---------- ---------- ----------- --------- ---------- ---------- ----------
                                                                    

                                                                    

  TOA        TOA-20 d   20 d- 226 d 1953      1954       1955-50Y   TOA-50 Y

                                                                    

  0.25       0.0551     0.008108    0.0632    0.000404   0.001255   0.0649

  0.5        0.0448     0.008108    0.0529    0.000404   0.001255   0.0545

  1.5        0.0297     0.008108    0.0379    0.000404   0.001255   0.0395

  2.5        0.0233     0.008108    0.0314    0.000404   0.001255   0.0330

  3.5        0.0192     0.008108    0.0273    0.000404   0.001255   0.0290

  4.5        0.0162     0.008108    0.0243    0.000404   0.001255   0.0260

  5.5        0.0139     0.008108    0.0220    0.000404   0.001255   0.0237

  6.5        0.0120     0.008108    0.0201    0.000404   0.001255   0.0218

  7.5        0.0104     0.008108    0.0185    0.000404   0.001255   0.0202

  8.5        0.0090     0.008108    0.0171    0.000404   0.001255   0.0188

  9.5        0.0078     0.008108    0.0159    0.000404   0.001255   0.0176

  10.5       0.0067     0.008108    0.0148    0.000404   0.001255   0.0165
  ---------- ---------- ----------- --------- ---------- ---------- ----------

[Table A6: Total exposure from HARRY for St. Louis County,
mR]{.underline}

  ---------- --------------------------------- -------------------- -------------------- ------------------------------- -------------------- --------------------
             \-\-\-\-\-\-\-\-\-\-\-\-- For                                               \-\-\-\-\-\-\-\-- -TOA - 50 Y                        
             1953\-\-\-\-\-\-\-\-\-\-\-\-\--                                             \-\-\-\-\-\-\-\-\-\-\-\-\-\--                        

  TOA        GM                                mean                 var                  GM                              mean                 var

  1.5        0.83                              1.05                 0.68                 0.86                            1.10                 0.74

  2.5        0.60                              0.76                 0.36                 0.63                            0.80                 0.39

  3.5        1.77                              2.69                 9.52                 1.88                            2.85                 10.71

  4.5        0.27                              0.35                 0.08                 0.29                            0.37                 0.09

  5.5        0.54                              0.59                 0.06                 0.58                            0.63                 0.07

  6.5        0.54                              [0.59]{.underline}   [0.06]{.underline}   0.58                            [0.63]{.underline}   [0.07]{.underline}

  SUM:                                         6.02                 10.75                                                6.39                 12.07

  GM =                                         5.28                                                                      5.68                 

  GSD =                                        1.7                                                                       1.7                  
  ---------- --------------------------------- -------------------- -------------------- ------------------------------- -------------------- --------------------

Although the exposure contribution from each radionuclide was not
estimated separately in the database accompanying this report, the
exposure from all tests for a few specific radionuclides was calculated
from the corresponding deposition densities and used to prepare the data
shown in Figures 18 through 22. These figures illustrate the fraction of
the total exposure from these particular radionuclides. The mean
deposition densities of each radionuclide for each test and test series
is provided in the database and can be used to estimate exposures for a
particular year from any particular radionuclide by multiplying by an
appropriate dose rate conversion factor from Beck (1980).

**Appendix 2: Additional Reading**

(1) **The history of nuclear weapons testing at the NTS:**

Anders R.M., Holl, J.M., Buck, A.L. and Dean, P.C., The United States
nuclear weapons program. A summary history. US Dept. of Energy report.
DOE/E5-0005 (draft), March, 1983.

Frieson, H.N. A perspective on atmospheric nuclear tests in Nevada.
Nevada Operations Office report. NVO-296; Aug. 1985.

Joint Committee on Atomic Energy. The nature of radioactive fallout and
its effects on man, Congressional hearings transcript; 1997.

Joint Committee on Atomic Energy. Fallout from nuclear weapons tests,
Congressional Hearings transcript; May, 1959)

U.S. Dept. of Energy. Announced United States Nuclear Tests, July 1945
through December, 1987. Nevada Operations Office report. NVO-209, Rev.
8; 1988.

**(2) The production of important radionuclides during those tests:**

Environmental Contamination from Weapons Tests. USAEC report. HASL-42;
1958.

Hicks, H.G. Radiochemical data collected on events from which
radioactivity escaped beyond the borders of the Nevada test range
complex. Lawrence Livermore National Laboratory report. UCRL-52934; Feb.
1981.

Radiological Health Data. U.S. Dept of Health, Education and Welfare,
Public Health Service. Monthly reports, 1958+

Public Health Service. "Tabulation of findings, radiation surveillance
network," available from CIC, Las Vegas.

Schoengold, C.R., DeMarre, M.E., McDowell, E.M., Radiological effluents
released from announced U.S. continental tests: 1961 through 1988. U.S.
Dept. of Energy Nevada Operations Office report. DOE/NV-317; May, 1990.

USAEC, Health and Safety Laboratory Fallout Quarterly Reports, 1958-.

(3) **The networks of fallout measurements:**

Bouville, A. and Beck, H.L. The HASL gummed-film network and its use in
the reconstruction of doses resulting from nuclear weapons tests.
Environ. Intl; in press.

Eisenbud, M. An Environmental Odyssey. People, Pollution, and Politics
in the Life of a Practical Scientist, University of Washington Press,
Seattle and Washington, 1990.

Harley, John H., A Brief History of Long-Range Fallout, in Health and
Safety Laboratory report HASL-306, Environmental Quarterly, July 1,
1976, pp I-3 to I-1.

(4) **The assessment of the activities deposited on the ground:**

Bouville, A., M. Dreicer, H.L. Beck, W.H. Hoecker, and B.W. Wachholz.
Models of radioiodine transport to populations within the continental
U.S. Health Phys. **59**(5): 659-668; 1990.

Bouville, A. Reconstructing doses to downwinders from fallout.
Proceedings of the Thirty-First Annual Meeting of the National Council
on Radiation Protection and Measurements. Proceedings No. 17, pp.
171-189. NCRP, Bethesda, MD, 1996.

Whicker, F.W. Environmental pathway analysis in dose reconstruction.
Proceedings of the Thirty-First Annual Meeting of the National Council
on Radiation Protection and Measurements. Proceedings No. 17, pp.
93-106,. NCRP, Bethesda, MD, 1996.

(5) **The vertical migration of fallout radionuclides into deeper layers
    of soil:**

> See references in text.

(6) **The assessment of the doses from external irradiation:**

Beck, H.L.; Krey, P.W. Radiation exposure in Utah from Nevada nuclear
tests. Science **220**:18-24; 1983.

Lloyd, R.D.; Gren, D.C.; Simon, S.L.; Wrenn, M.E.; Hawthorne, H.A.;
Lotz, T.M.; Stevens, W.; Till, J.E. Individual external exposures from
Nevada Test Site fallout for Utah leukemia cases and controls. Health
Phys. **59**(5):723-737; 1990.

Simon, S.L.; Till, J.E.; Lloyd, R.D.; Kerber, R.L.; Thomas, D.C.;
Preston-Martin, S.; Lyon, J.L.; Stevens, W. The Utah leukemia
case-control study: dosimetry methodology and results. Health Phys.
**68**(4):460-471; 1995.

Haskell, E.H., I.K. Balliff, G.H. Kenner, P.L. Kaipa, and M.E. Wrenn.
Thermoluminescent measurements of gamma-ray doses attributable to
fallout from the Nevada Test Site using building bricks as natural
dosimeters. Health Physics **66**, 380-391; 1994.

**Appendix 3: Classified Data That Could be of Use in Assessing Fallout
Impact on U.S. Population**

The ability to estimate fallout deposition from NTS shots was made
possible by the calculations of Hick based on cloud measurements of the
relative production of the various fission products from each test. The
composition of debris is very dependent on the spectrum of neutrons
produced in the device and the composition of the fuel. Similar data for
tests carried out by the U.S. and U.K. in the Pacific as well as for
tests carried out in the Soviet Union will be required to allow
comparable estimates of fallout deposition to be made for tests carried
out outside the U.S. Such data, if available, is classified.

Also classified is the fraction of the total yield of individual shots
that resulted from fission versus fusion. Again, this information will
be needed to make reasonable estimates of deposition and resultant doses
from tests held outside the U.S. In some cases, even the exact value of
the total yield is classified. Since tritium is a byproduct of fusion,
any information on the amount of tritium released from a particular test
is probably also classified.

For the NTS tests, the efficiencies of fission are classified as well as
any information that would allow one to infer those efficiencies, such
as ratios of Cs-137/Pu activity. Thus the amounts of residual
(unfissioned) Pu in the fallout had to be inferred as discussed in this
report. The resultant crude estimates of Pu deposition thus have
relatively large uncertainty compared to the deposition of fission
products.

![](media/image1.png){width="8.1in"
height="5.6in"}![](media/image2.png){width="2.1in"
height="1.4251968503937007in"}

Figure 1. Cs-137 deposition density due to all NTS tests.

![](media/image3.png){width="6.440972222222222in"
height="4.541666666666667in"}

Figure 2. I-131 deposition density due to all NTS tests.

![](media/image4.png){width="7.875196850393701in"
height="5.406299212598425in"}![](media/image5.png){width="2.3625984251968504in"
height="1.5543307086614173in"}

Figure 3. Ratio of Cs-137 to Sr-90 deposition density from all tests.
Number of counties in each group shown in parenthesis.

![](media/image6.png){width="7.9in"
height="5.461811023622047in"}![](media/image7.png){width="1.7in"
height="1.1964566929133857in"} Figure 4. Estimated ratio of Cs-137 to
Pu-239+249 deposition density. Number of counties in each group shown in
parenthesis.

![](media/image8.wmf){width="5.901388888888889in"
height="5.611805555555556in"}

Figure 5. Fraction of total Cs-137 deposition from each test series.

![](media/image9.wmf){width="5.998611111111111in"
height="3.707638888888889in"}

Figure 6. Ten tests depositing the greatest amounts of Cs-137 in the
continental U.S.

![](media/image10.wmf){width="5.902083333333334in"
height="3.6381944444444443in"}

Figure 7. Ten tests producing the greatest population-weighted Cs-137
deposition density.

![](media/image11.wmf){width="6.094444444444444in" height="3.625in"}

Figure 8. Cumulative Cs-137 deposition relative to total produced versus
distance from the NTS.

![](media/image12.wmf){width="5.997916666666667in"
height="3.564583333333333in"}

Figure 9: Cumulative Cs-137 deposition relative to total deposited in
the U.S. versus distance from the NTS.

![](media/image13.png){width="8.699212598425197in"
height="5.699212598425197in"}![](media/image14.png){width="3.1535433070866143in"
height="1.6070866141732283in"}Figure 10: Total dose to average exposed
individual from all tests. Number of counties in each group shown in
parenthesis.

![](media/image15.png){width="8.0in"
height="5.531102362204725in"}![](media/image16.png){width="2.8in"
height="1.7381889763779528in"}Figure 11. Dose to average exposed
individual from tests in 1951. Number of counties in each group shown in
parenthesis.

![](media/image17.png){width="8.0in"
height="5.531102362204725in"}![](media/image18.png){width="2.3in"
height="1.441732283464567in"}Figure 12. Dose to average exposed
individual from tests in 1952. Number of counties in each group shown in
parenthesis.

![](media/image19.png){width="8.0in"
height="5.531102362204725in"}![](media/image20.png){width="2.8in"
height="1.7716535433070866in"}Figure 13. Dose to average exposed
individual from tests in 1953. Number of counties in each group shown in
parenthesis.

![](media/image21.png){width="7.9in"
height="5.4in"}![](media/image22.png){width="3.061023622047244in"
height="1.611023622047244in"}Figure 14. Dose to average exposed
individual from tests in 1955. Number of counties in each group shown in
parenthesis.

![](media/image23.png){width="8.0in"
height="5.531102362204725in"}![](media/image24.png){width="2.7in"
height="1.7090551181102362in"}Figure 15. Dose to average exposed
individual from tests in 1957. Number of counties in each group shown in
parenthesis.

![](media/image25.png){width="8.699212598425197in"
height="5.599212598425197in"}![](media/image26.png){width="3.083464566929134in"
height="1.4700787401574804in"} Figure 16. Dose to average exposed
individual from SEDAN and Smallboy. Number of counties in each group
shown in parenthesis.

![](media/image27.wmf){width="7.097916666666666in"
height="4.375694444444444in"}

Figure 17. Ten tests with the greatest contributions to total population
exposure. The value for SEDAN is much more uncertain than that for the
other tests.

![](media/image28.png){width="8.5in"
height="5.8771653543307085in"}![](media/image29.png){width="2.8in"
height="1.1137795275590552in"} Figure 18. Fraction of total dose from
Te-I-132. The number of counties in each group is shown in parenthesis.

![](media/image30.png){width="8.6in"
height="5.946456692913386in"}![](media/image31.png){width="2.8in"
height="1.50748031496063in"} Figure 19. Fraction of total dose from
Ba-La-140. The number of counties in each group is shown in parenthesis.

![](media/image32.png){width="8.7in"
height="6.016141732283464in"}![](media/image33.png){width="2.7in"
height="1.405511811023622in"} Figure 20. Fraction of total dose from
Zr-Nb-95. The number of counties in each group is shown in parenthesis.

![](media/image34.png){width="8.8in"
height="6.0854330708661415in"}![](media/image35.png){width="2.7in"
height="1.4755905511811023in"} Figure 21. Fraction of total dose from
Np-239. The number of counties in each group is shown in parenthesis.

![](media/image36.png){width="8.991732283464566in"
height="6.217322834645669in"}![](media/image37.png){width="2.4in"
height="1.4807086614173228in"}Figure 22. Fraction of total dose from
Ru-103. The number of counties in each group is shown in parenthesis.

[^1]: (The very low Np-239 values given by Hicks for some shots that
    apparently used very little Pu, suggests that U-233 may have been
    used in a few tests.)

[^2]: Note that the county Pu deposition-density estimates for a
    particular are correlated since the uncertainty in Cs/Pu (or
    I-131/Pu) is the same for all counties for a given test. Thus the
    uncertainty in the Pu deposited in the U.S. from a given test will
    have minimum uncertainty of GSD=1.5. This correlation was accounted
    for in calculating the total Pu deposition for the U.S. discussed
    later in this report.