2 Deposition Data Analysis
4.8 Worst-Case Collective Dose Commitments
4.8.2 Worst-Case Collective Dose Commitments for the VRS
The effective, maximum collective dose commitments corresponding to the total depositions for Cs-137, Sr-90, and I-131 in Table 86, Table 87, and Table 88, respectively, were computed for the VRS. For Cs-137, Figure 90 illustrates the frequency and cumulative percentages for the maximum collective dose commitments for the overall and transboundary region assuming no threshold. Table 111 and Table 112 provide the maximum collective dose commitment for the region as well as each country in the region as a function of the assumed threshold level. (The collective dose commitments are also broken down by pathway for information purposes.) Note that the maximum collective VRS dose commitments (for the no threshold hypothesis) are rank-ordered as follows:
VRS Cs-137: Regional > Japan > China > N. Korea > S. Korea > Russia > Taiwan > Hong Kong
> Alaska (U.S.) > Mongolia > Aleutians (U.S.) > Vietnam
Therefore, even though the maximum dose commitment was found in Russia, the maximum collective dose is found in Japan (which is not surprising based upon its high population density and relative proximity to both the VRS and the PRS). Furthermore, unlike the PRS results, other countries have collective dose commitments within an order of magnitude of that for Japan, and there are many more countries with non-zero collective dose commitments.
Frequency, Number of Days Frequency, Number of Days
0 Collective dose commitment (person-Sv)
Frequency Collective dose commitment (person-Sv)
Frequency
Figure 90. Frequency histogram and cumulative percentages for the VRS Cs-137 effective population dose commitments for the (a) Regional and (b) Transboundary areas for CY2000. No Threshold Basis. The corresponding population information is presented in Figure 46 and Figure 47.
The effects of the VRS releases are potentially much more profound than those from the PRS. For example, the maximum collective dose commitments in Table 111 (for the no threshold case)
correspond to up to an additional 9783 mortalities [19] over the entire region and 9771 additional over the transboundary region (using a factor of 5x10-5 mortality per mSv for all ages). The additional mortalities from the maximum collective dose commitments for Japan, China, N. Korea, S. Korea, Russia, and Taiwan are 9501, 8575, 2485, 2436, 1614, and 318, respectively. Therefore, even the impact on Taiwan, a country not proximate to the VRS, could be considered significant. The State of Alaska, the Aleutian Islands, and Hong Kong might have an additional two mortalities each from the adjusted releases and worst-case deposition-to-dose factors.
Also unlike the results for the PRS analysis, Table 111 and Table 112 indicate that there is much less of an impact on the magnitudes of the dose commitments in concert with large populations on the collective VRS dose estimates. That is, the collective dose commitments for the countries (e.g., Japan, China, N. Korea, S. Korea, and Russia) in the vicinity of the VRS are relatively insensitive to the introduction of thresholds into the collective dose commitment computation. For example, the results after imposing a threshold of 0.1 mSv (or 0.01 mrem) translate into over 9488 additional mortalities in Japan and significant numbers in other countries of interest. This is a result of much higher dose commitments in these countries from the VRS releases. Even the introduction of a relatively large threshold (e.g., 1.0 mSv) only reduces the impact of the Cs-137 depositions to 8423 additional mortalities.
Unlike the earlier UNSCEAR results, the additional mortalities described above do not appear to be significantly mitigated by being small fractions of very large, affected populations. Said additional mortalities are 1 in 13 105 (or 8 per 100 000) for Japan and 1 in 11 112 (or 9 per 100 000) persons affected by the maximum releases from the VRS.
For Sr-90, Figure 91 illustrates the frequency and cumulative percentages for the maximum collective dose commitments for the overall and transboundary region assuming no threshold. Table 113 and Table 114 provide the maximum collective dose commitment for the region as well as each country in the region as a function of the assumed threshold level. Note that the maximum collective VRS dose commitments (for the no threshold hypothesis) have the same ordering as those for the Cs-137. Again, even though the maximum dose commitment was found in Russia (as indicated in Table 113), the maximum collective dose is found in Japan. The number of additional mortalities can be as high as
Frequency, Number of Days Frequency, Number of Days
The results in Table 113 and Table 114 confirm the insensitivity of the collective dose estimates to the magnitudes of the dose commitments as indicated above for Cs-137.
0 20 40 60 80 100 120
4.66E+00 1.08E+03
2.15E+0 3 3.23E+
03 4.31E+0
3 5.38E+0
3 6.46E+03
7.53E+0 3 8.61E+03
More Collective dose commitment (person-Sv)
Frequency
0 20 40 60 80 100 120
Cumulative(%)
(a) Regional
0 20 40 60 80 100 120 140 160
1.68E+00 1.08E+03
2.15E+0 3 3.22E+
03 4.30E+0
3 5.37E+0
3 6.45E+03
7.52E+0 3 8.59E+03
More Collective dose commitment (person-Sv)
Frequency
0 20 40 60 80 100 120
Cumulative(%)
(b) Transboundary
Figure 91. Frequency histogram and cumulative percentages for the VRS Sr-90 effective population dose commitments for the (a) Regional and (b) Transboundary areas for CY2000. No Threshold Basis. The corresponding population information is presented in Figure 48 and Figure 49.
For I-131, Figure 92 illustrates the frequency and cumulative percentages for the maximum collective dose commitments for the overall and transboundary region, respectively, assuming no threshold.
Table 115 and Table 116 provide the maximum collective dose commitment for the region as well as each country in the region as a function of the assumed threshold level. Note that the maximum collective PRS dose commitments (for the no threshold hypothesis) are rank-ordered as follows:
PRS I-131: Regional > Japan > China > S. Korea > N. Korea > Russia > Aleutians (U.S.) > Mongolia > Alaska (U.S.)
Thus for I-131, the maximum collective VRS dose commitment is found in Japan (which is unlike the results found for the corresponding PRS releases). Unlike the Cs-137 and Sr-90 results, the I-131 releases translate into no additional mortalities. Also unlike the VRS results for Cs-137 and Sr-90, the collective doses are sensitive to the imposition of a threshold (because of the much smaller dose commitments for I-131 in countries other than Russia). Again, the results in Table 115 and Table 116 indicate that the I-131 from the VRS releases will have an insignificant impact on any country, including Russia.
Frequency, Number of Days Frequency, Number of Days
0 Collective dose commitment (person-Sv)
Frequency Collective dose commitment (person-Sv)
Frequency
Figure 92. Frequency histogram and cumulative percentages for the VRS I-131 effective population dose commitments for the (a) Regional and (b) Transboundary areas for CY2000. No Threshold Basis. The corresponding population information is presented in Figure 50 and Figure 51.
4.8.2.1 Specific Case Examples: Japan and U.S. Collective Dose Commitments from the VRS
Figure 93 illustrates the collective dose results for Japan from the VRS releases for CY2000. Using a mortality risk factor of 5x10-5 per mSv for all ages [19], the maximum collective dose commitment of 1.90x105 person-Sv (as shown in Table 111) would translate into more than 9500 additional
mortalities or 8 additional mortalities for every 100 000 persons. However, the information in Figure 93 indicates that this would be a low-probability event for CY2000. Over 60% of the maximum collective dose commitments are less than 3.17x104 person-Sv, which would translate into 1538 additional mortalities (or between 1 and 2 per 100 000 persons).
0 Collective dose commitment (person-Sv)
Frequency
Figure 93. Japan Results: Frequency histogram and cumulative percentages for the weighted VRS Cs-137 effective collective dose commitments for CY2000. No Threshold Basis. The corresponding populations are provided in Figure 52.
The results for the collective dose commitments from the PRS for the U.S. territories considered in this report are illustrated in Figure 94. Note that, when a mortality risk factor of 5x10-5 per mSv for all
Frequency, Number of Days Frequency, Number of Days
Frequency, Number of Days
VRS releases for CY2000. These can be considered negligible when compared to both background radiation doses and other causes of death.
0 Collective dose commitment (person-Sv)
Frequency Collective dose commitment (person-Sv)
Frequency
(b) Aleutian Islands (U.S.)
Figure 94. Alaska (U.S.) Results: Frequency histogram and cumulative percentages for the VRS Cs-137 effective collective dose commitments for (a) Alaska and (b) the Aleutian Islands for CY2000.
No Threshold Basis. The corresponding population information is found in Figure 53 and Figure 54.
4.8.3 Summary of the Effective Collective Worst-Case Dose Commitments