ML11192A302
| ML11192A302 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 10/28/2010 |
| From: | Office of Nuclear Regulatory Research, Sandia |
| To: | |
| References | |
| FOIA/PA-2011-0083 NUREG-1935 R3 DRFT | |
| Download: ML11192A302 (28) | |
Text
pllp-P J. , .,o Revision 3 - 10/28/2010 8:18:00 AM 7.0 OFF-SITE CONSEQUENCES 7.1 Introduction The MACCS2 consequence model (Version 2.4.0.5) was used to calculate offsite doses and their effect on members of the public. MACCS2 was developed at Sandia National Laboratories for the NRC for use in probabilistic risk assessments for commercial nuclear reactors to simulate the impact of accidental atmospheric releases of radiological materials on humans and on the surrounding environment. The principal phenomena considered in MACCS2 are atmospheric transport using a straight-line Gaussian plume model of, short-term and long-term dose accumulation through several pathways including cloudshine, groundshine, inhalation, deposition onto the skin, and food and water ingestion. The ingestion pathway was not treated in the analyses reported here because uncontaminated food and water supplies are abundant within the U.S. and it is unlikely that the public would eat radioactively contaminated food. The doses that are included in the reported risk metrics are as follows:
" Cloudshine during plume passage
- Groundshine during the emergency and long-term phases from deposited aerosols
- Inhalation during plume passage and following plume passage from resuspension of deposited aerosols. Resuspension is treated during both the emergency and long-term phases.
Additional enhancements were made to MACCS2 [24] as an element of the SOARCA project.
In general, these enhancements reflect recommendations obtained during the SOARCA external review and also reflect needs identified by the broader consequence analysis community. The code enhancements done for SOARCA are primarily to improve fidelity, improve code performance, and enhance existing functionality. Nevertheless, these enhancements are anticipated to have a significant effect on the fidelity of the analyses performed under the SOARCA project.
MACCS2 previously allowed up to three emergency-phase cohorts. Each emergency-phase cohort represents a fraction of the population who behave in a similar manner, although response times can be a function of radius. For example, a cohort might represent a fraction of the population who rapidly evacuate after officials instruct them to do so. To create a high-fidelity model for SOARCA, the number of emergency-phase cohorts was increased as described in the previous chapter on emergency response. This allowed significantly more variations in emergency response (e.g., variations in preparation time prior to evacuation to more accurately reflect the movement of the public during an emergency). In a similar way, modeling evacuation routes using the network-evacuation model adds a greater degree of realism than in previous analyses that used the simpler, radial-evacuation model.
7.2 Peach Bottom Source Terms Brief descriptions of the source terms for the Peach Bottom accident scenarios are provided in Table 20. For comparison, the largest source term from the Sandia Siting Study (SST1) [25] is also shown. Of the Peach Bottom source terms shown in the table, the unmitigated STSBO is the 132
leie erod ei aRevision 3- 10/28/2010 8:L18:00 AM largest in terms of release fractions and the release begins at the earliest time; the LTSBO is the smallest in terms of release fractions and the release begins at the latest time; the mitigated STSBO (with RCIC blackstart) is intermediate both in terms of release magnitude and timing, except that the Ce release fraction is the largest of the three SOARCA source terms.
The fission product inventory used in these analyses are presented in Appendix A. 1. The inventory data were evaluated specifically for the SOARCA work and reflect realistic fuel cycle data from Peach Bottom.
By comparison, the SST1 source term is significantly larger in magnitude, especially for the cesium group, than any of the Peach Bottom source terms. Moreover, it begins only 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after accident, initiation. Thus, the current understanding of accident progression has clearly led to a very different characterization of release signatures than was current at the time of the Sandia Siting Study.
Table 20 Brief Source-Term Description for Unmitigated Peach Bottom Accident Sequences and the SST1 Source Term from the Sandia Siting Study Integral Release Fractions by Chemical Group Release Timing CDF Xe Cs Ba I Te Ru Mo Ce La Start End Scenario I I I (hr) (hr)
PB LTSBO 3x1-0 0.833 0.017 0.014 0.036 0.023 0.000 0.004 0.001 0.000 19.5 48.0 PB STSBO w/ BS 3x10 0.962 0.021 0.058 0.074 0.033 0.000 0.004 0.006 0.000 13.3 48.0 PB STSBO 3xT 0.985 0.023 0.083 0.103 0.117 0.000 0.006 0.005 0.000 8.1 48.0 SSTI Wx10 1.000 0.670 0.070 0.450 0.640 0.050 0.050 0.009 0.009 1.5 3.5 For comparison, a consequence analysis using the old SST1 source term is presented in this chapter. This allows a direct comparison, using the same modeling options and result metrics, between the SST1 source term and the current, best-estimate source terms.
7.3 Consequence Analyses The results of the consequence analyses are presented in terms of to the public for each of the three accident scenarios identified for Peach Bottom. Both unconditional and conditional risks are tabulated. The conditional risks assume that the accident occurs and show the risks to individuals as a result of the accident. The unconditional risks are the product of the core damage frequency and the conditional risks. The unconditional risks are the likelihood of receiving a fatal cancer or early fatality to an average individual living within a specified radius of the plant per year of plant operation.
The risk metrics are latent-cancer-fatality and early-fatality risks to residents in circular regions surrounding the plant. They are also averaged over the entire residential population within the circular region. The risk values represent the predicted number of fatalities divided by the population for three choices of dose-truncation level. These risk metrics account for the distribution of the population within the circular region and for the interplay between the population distribution and the wind rose probabilities.
133
Revision 3 - 10/28/2010 8:18:00 AM In addition to the base case mitigated and unmitigated accident scenarios, three additional analyses are reported in this chapter. A sensitivity analysis for the unmitigated STSBO scenario shows the influence of the size of the evacuation zone on predicted risk. Another sensitivity analysis considers the effect of seismic activity on emergency response. A separate analysis of the SSTl source term [25] (summarized in Table 20) allows the older source-term assumptions to be compared with the current state-of-the-art methods for source-term evaluation using otherwise equivalent assumptions and models. This analysis does not try to reproduce the Sandia Siting Study results; it merely overlays the older source term onto what are otherwise SOARCA assumptions for dose-response modeling, emergency response, etc.
7.3.1 Unmitigated Long-Term Station Blackout Scenario Table 21 displays the conditional, mean, latent-cancer-fatality risks to residents within a set of concentric circular areas centered at the Peach Bottom site for the unmitigated long-term station blackout (LTSBO) scenario. Four values of dose-truncation level are shown in the table: linear, no threshold (LNT); 10 mrem/yr; the average, annual, US-background radiation (including average medical radiation) of 620 mrem/yr; and the Health Physics Society (HPS) recommended dose truncation of 5 rem/yr, with a lifetime limit of 10 rem.
The HPS dose-truncation level is more complex that the others because it involves both annual and lifetime limits. According to the recommendation, annual doses below the 5-rem truncation level do not need to be counted toward health effects; however, if the lifetime dose exceeds 10 rem, all annual doses, no matter how small, count toward health effects.
Table 22 is analogous to Table 21, but displays the unconditional rather than the conditional risks. In the case of the Peach Bottom long-term station blackout, the mean core damage frequency of 3.10 6/yr is used, a frequency that is based in the pessimistic assumption that B.5.b mitigation does not succeed (cf., Section 3.1.4). The unconditional risk is the product of the conditional risk and this core damage frequency.
Table 21 Conditional, i.e., assuming accident occurs, Mean, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities are for the Unmitigated LTSBO Scenario, which has a Mean Core Damage Frequency of 3xl0 6/yr.
Radius of 5 rem/yr; Circular Area (mi) LNT 10 mrem/yr 620 mrem/yr 10 rem lifetime 10 1.9'10"4 1.7-10" 1.8'10-0 1.6'10"'
20 1.9.10-4 1.6"10"4 5.9"10-5 3.4.1"W' 30 1.3'10-4 1.1.10-4 3.7'10"W 1.6-10V 40 8.5"10-5 6.8'10-5 2.0"10-5 6.9'10-6 50 7.0"10- 5.4"10"' 1.4.10 4.5"10' 134
P49o 10 Revision 3 - 10/28/2010 8:18:00 AM Table 22 Unconditional, Mean, Latent-Cancer-Fatality Risks (1/reactor year) for Residents within the Specified Radii of the Peach Bottom Site. Risks Are for the unmitigated LTSBO Scenario, which has a mean core damage frequency of 3.10-6/yr.
Radius of 5 rem/yr; Circular Area (mi) LNT 10 mrem/yr 620 mrem/yr 10 rem lifetime 10 5.8' 1I0"'° 5.0' 10'l 5.5' 10-"1 4.7"10"'-'
20 56 10 4.9 10t° 1.8"10"-o 1.0'10l1 30 4.0" 10lu 3T3' --I0-w 1.1I'10"10 4.9' 10-"
40 2.5'10l° 2.0'10' 6.0-011 2.1'10"-'
50 2.1'10l°_ 1.6'10l' 4.3-10l" 1.3'10l" The values in Table 21 are shown in Figure 77. The figure shows that for LNT and for a truncation dose of 10 mrem/year, the risk is greatest for those closest to the plant and diminishes monotonically as distance increases. On the other hand, for a large value of the truncation dose, the risk reaches a maximum outside the 10-mile evacuation zone. The explanation for this counterintuitive trend is provided in the following discussion of the risks incurred during the emergency versus the long-term phases.
2.OE.4 0
4)E .0E-4 0.
5.OE-5 0
0.0E+O 10 20 30 40 50 Radius of Circular Area (mi)
Figure 77 Conditional, i.e., assuming accident occurs, mean, latent-cancer-fatality probabilities from the Peach Bottom unmitigated LTSBO sequence for residents within a circular area of specified radius from the plant. The plot shows four values of dose-truncation level.
Figure 78 shows the conditional LNT risks for the Peach Bottom unmitigated LTSBO for the emergency (EARLY) and long-term (CHRONC) phases. The entire height of each column shows the combined (Total) risk for the two phases. The emergency response is very effective within the evacuation zone (10 mi) during the early phase, so those risks are very small and entirely represent the 0.5% of the population that does not evacuate. The peak in the EARLY risk curve is at 20 miles, which is the first location in the plot outside of the evacuation zone.
135
945" 194I L Revision 3 - 10/28/2010 8:18:00 AM 2.5E-4 T 2.0E-4 U) _OCHRONC N EARLY 1.5E-4 cEZ1.2 - -
E E
.0 CL 1.0E-4 o
.2 o 5.OE-5 0
0.OE+0 ---
10 20 30 40 50 Radius of Circular Area (ml)
Figure 78 Conditional, i.e., assuming accident occurs, mean, LNT, latent-cancer-fatality probabilities from the Peach Bottom unmitigated LTSBO scenario for residents within a circular area of specified radius from the plant. The plot shows the probabilities from the emergency phase (EARLY), long-term phase (CHRONC), and the two phases combined.
The CHRONC risks dominate the total risks for the accident scenario when the LNT dose-response assumption is made. These long-term risks are controlled by the habitability (return) criterion, which is the dose level at which residents are allowed to return to their homes following the emergency phase. For Peach Bottom, the habitability criterion is an annual dose limit of 500 mrem. However, this dose rate is below the truncation levels for the background (620 mrem/yr) and HPS dose-truncation criteria; therefore, most of the doses received during the long-term phase are not counted toward health effects when using these criteria. Thus, most of the risks associated with the 620 mrem/yr and HPS dose truncation criteria are from doses received during the first year. Doses received during the first year include all of the EARLY doses plus a fraction of the CHRONC doses. Due to the habitability criterion, doses received after the first year generally fall below these truncation levels and so do not contribute to risk.
This explains why the risk profiles for these dose-truncation criteria in Figure 77 are similar to the EARLY profile in Figure 78.
The prompt-fatality risks are identically zero for this accident scenario. This is because the release fractions (shown in Table 20) are too low to produce doses large enough to exceed the dose thresholds for early fatalities, even for the 0.5% of the population that does not evacuate.
The largest value of the mean, accute dose for the closest resident (0.5 to 1.2 km from the plant) for this scenario is about 0.1 Gy to the red bone marrow, which is usually the most sensitive 136
WI, . Revision 3 - 10/28/2010 8:18:00 AM organ for prompt fatalities; whereas, the minimum acute dose that can cause an early fatality is about 2.3 Gy to the red bone marrow. Calculated doses are all well below this threshold.
7.3.2 Short-Term Station Blackout with RCIC Blackstart Table 23 displays the conditional, mean, latent-cancer-fatality risks to residents within a set of concentric circular areas centered at the Peach Bottom site for the short-term station blackout (STSBO) scenario with successful RCIC blackstart shown graphically in Figure 79. The RCIC blackstart delays the beginning of release and provides more time for evacuation prior to release than in the subsequent scenario, in which RCIC blackstart is not attempted or fails.
Table 24 is analogous to Table 23, but shows unconditional rather than conditional risks. In the case of the Peach Bottom short-term station blackout with RCIC blackstart, the mean core damage frequency of 3" 10- 7/yr is used, a frequency that is based on the pessimistic assumption that B.5.b mitigation does not succeed (cf., Section 3.2.4).
Table 23 Conditional, i.e., assuming accident occurs, Mean, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities are for the STSBO Scenario with RCIC blackstart, which has a mean core damage frequency of 3.10 7/yr.
Table 24 Unconditional, Mean, Latent-Cancer-Fatality Risks (1/reactor year) for Residents within the Specified Radii of the Peach Bottom Site. Risks are for the STSBO Scenario with RCIC blackstart, which has a mean core damage frequency of 3.10-7/yr.
137
P : CeJ* IRevision O(L* 3- 10/28/2010 8:18:00 AM 6.E-4
- -,5.E-4 5.E4 ..
LNT
- i10 mrem/yr l
0 .2 0620 mrem/yr r-. 4.E-4 m05 rem/yr, lOrem lifetimel
.10 3.E-4 .
a.2- 02.E .= 1.E-4 0
0.E+0 10 20 30 40 50 Radius of Circular Area (mi)
Figure 79 Conditional, i.e., assuming accident occurs, mean, latent-cancer-fatality probabilities from the Peach Bottom STSBO scenario with RCIC blackstart for residents within a circular area of specified radius from the plant. The plot shows four choices of dose-truncation level.
Figure 80 shows the LNT latent-cancer-fatality risks for the Peach Bottom short-term station blackout with RCIC blackstart for the emergency (EARLY) and long-term (CHRONC) phases.
The height of each column indicates the combined (Total) risk for the two phases. The emergency response is very effective within the evacuation zone (10 mi) during the early phase, so those risks are very small and entirely represent the 0.5% of the population that does not evacuate. The peak in the EARLY risk curve is at 20 miles, which is the first location in the plot outside of the evacuation zone.
138
- EARLY Z1.2 0C 4E 4.E-4 E 3.E-4 2.E-Q.2-Cu 0 I.E-4 0
0.E+0 10 20 30 40 50 Radius of Circular Area (mi)
Figure 80 Conditional, i.e., assuming accident occurs, mean, LNT, latent-cancer-fatality probabilities from the Peach Bottom STSBO sequence with RCIC blackstart for residents within a circular area of specified radius from the plant. The plot shows the risks from the emergency phase (EARLY), long-term phase (CHRONC), and the two phases combined.
Unlike the unmitigated LTSBO scenario described in the previous subsection, the long-term-phase risks for this scenario are significantly lower than the emergency-phase risks except within the evacuation zone (10 mi) where the emergency-phase risks are small. The long-term risks are controlled by the habitability or return criterion, which is an annual dose limit of 500 mrem.
Since the overall risks are controlled by the emergency-phase risks, the overall risk profile has a peak at 20 miles, reflecting the low risks to those who evacuate.
Since the annual dose limit of the habitability criterion (500 mrem/yr) is lower than the dose truncation levels for the 620 mrem/yr and HPS criteria, those two risk profiles (shown in Figure
- 79) are similar to the emergency-phase profile shown in Figure 80. In other words, the long-term doses are largely excluded by the 620 mrem/yr and HPS criteria, so the health effects are dominated by doses received during the emergency phase. As a result, those risk profiles are bounded above by the emergency-phase profile in Figure 80.
It is somewhat counterintuitive that some of the risks shown in Figure 79 for the HPS truncation criteria are greater than those for the 620 mrem (background) dose truncation level. This trend can occur in some cases because of the lifetime limit of 10 rem that is part of the HPS criteria.
When annual doses are less than 5 rem, but the total lifetime dose exceeds 10 rem, all annual doses, no matter how small, are used to estimate risk using the HPS criteria. On the other hand, only the annual doses that exceed 620 mrem are used with background dose truncation. Since doses diminish in time, this truncation criterion generally excludes at least a portion of the LNT dose. Thus, it is not difficult to see how dose truncation using the HPS criteria can sometimes produce greater risks than using the background radiation level.
139
Revision 3- 10/28/2010 8:18:00 AM The prompt-fatality risks are identically zero for this accident scenario. This is because the release fractions are too low to produce doses large enough to exceed the dose thresholds for early fatalities, even for the 0.5% of the population that does not evacuate.
7.3.3 Unmitigated Short-Term Station Blackout Table 25 displays the conditional, mean, latent-cancer-fatality risks to residents within a set of concentric circular areas centered at the Peach Bottom site for the unmitigated short-term station blackout (STSBO) scenario (i.e., without RCIC blackstart). The releases for this scenario are very similar to those for the previous one, except they are slightly larger and occur earlier.
Comparing Table 23 and Table 25, it can be seen that the risks are nearly the same for the two STSBO. Table 266 is analogous to Table 25, but shows unconditional rather than conditional risks. in the case of the Peach Bottom short-term station blackout without RCIC blackstart, the mean core damage frequency of 3.10-7/yr is used, a frequency that is based on the pessimistic assumption that B.5.b mitigation does not succeed (cf., Section 3.2.4).
The values in Table 25 are plotted in Figure 81. The plot shows that predicted risks reach a maximum beyond the EPZ (10 mi) for all choices of dose truncation level. The LCF probabilities shown in Tables 26 and 27 for the HPS threshold model (5 REM/yr, 10 REM lifetime) are greater than the background threshold model (620mREM/yr) for distances of 10 and 20 miles.
The explanation for this trend is provided above in Section 7.3.2 Table 25 Conditional, i.e., assuming accident occurs, Mean, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities are for the unmitigated STSBO Scenario, which has a mean core damage frequency of 3.10 7 /yr.
Radius of 10 620 5 rem/yr; Circular Area (mi) LNT mrem/yr mrem/vr 10 rem lifetime 10 2.3.10-4 2.0.10' 9.9.10.6 1.0 -10 20 4.9. 10-4 44.6.100-7 i.9.-10.4 3.0. 10-4 30 3 .3 "10- 3 .1. '10 1 0 1.7 '10 -4 40 2.1"0 1.9.104 4.8710.7 8.4'10" 50 1.6'0 1.' . 7. 0 5.71.055 Table 26 Unconditional, Mean, Latent-Cancer-Fatality Risks (1/reactor year) for Residents within the Specified Radii of the Peach Bottom Site. Risks are for the unmitigated STSBO Scenario, which has a mean core damage frequency of 3.10- 7/yr.
Radius of 10 620 5 rem/yr; Circular Area (mi) LNT mrem/yr mrem/zr 10 rem lifetime 10 7.0'10-"' 6.0' 10"'1 3.0.101" 3.1"10t2-20 1.5" 857"10 8.9'10l1 30 1.0"101' 9.3_101' 5.4.'10- 5.2'10' 1 40 6.2.10l' 5.6'1011 2.9"10l' 2.5'101" 50 4.9_10" 4.4"10-11 2.1'10l 1.7'10" 140
Pl~l Revision 3 - 10/28/2010 8:18:00 AM 5.E-4 W
0
-'i 3~.E-4
~0- V CL 2.E-4 0
O.E+0 20 30 4C Radius of Circular Area (ml)
Figure 81 Conditional, i.e., assuming accident occurs, mean, latent-cancer-fatality probabilities from the Peach Bottom unmitigated STSBO scenario for residents within a circular area of specified radius from the plant. The plot shows four choices of dose-truncation level.
Figure 82 shows the LNT latent-cancer fatality risks for the Peach Bottom unmitigated STSBO scenario for the emergency and long-term phases. The height of each of the columns shows the combined (Total) risk for the two phases. The emergency response is very effective within the evacuation zone (10 mi) during the early phase, so those risks are very small and mostly represent the 0.5% of the population that does not evacuate. The peak in the EARLY risk profile is at 20 miles, which is the first location in the plot outside of the evacuation zone.
141
Revision 3 - 10/28/2010 8:18:00 AM 5.E-4 S , CHRONC
" 4.E-4 I M EARLY 0-3.E-4
.E
&0-
. 2.E-4 U 1.E-4 0
0O.E+O 10 20 30 40 50 Radius of Circular Area (mi)
Figure 82 Conditional, i.e., assuming accident occurs, mean, LNT, latent-cancer-fatality probabilities from the Peach Bottom unmitigated STSBO scenario for residents within a circular area of specified radius from the plant. The plot shows the probabilities from the emergency phase (EARLY), long-term phase (CHRONC), and the two phases combined.
Similar to the STSBO scenario with RCIC blackstart described in the previous subsection, the long-term-phase risks for this scenario are significantly smaller than the emergency-phase risks except within the evacuation zone (10 mi), where emergency-phase risks are very small. The long-term risks are controlled by the habitability or return criterion, which is an annual dose limit of 500 mrem. Since the overall risks are dominated by the emergency-phase risks, the overall risk profile has a peak at 20 miles.
Because the annual dose limit of the habitability criterion is lower than the dose truncation levels of the 620 mrem/yr and HPS criteria, those two risk profiles (shown in Figure 8 1) are mainly influenced by risks during the emergency-phase, shown in Figure 82.
The risk trends displayed in Figure 82are similar to those in Figure 80 in terms of the relative importance of the emergency phase. The contribution of the emergency phase to the overall risk is much less for the Peach Bottom unmitigated LTSBO scenario discussed above and for all of the Surry scenarios presented in Chapter 7 of Appendix B of this report. Like the Peach Bottom STSBO scenario with RCIC blackstart, the uniqueness of this scenario appears to be related to the unusually small release fraction for Cs compared with those for the other chemical groups (cf., Table 20).
The prompt-fatality risks are identically zero for this accident scenario. This is because the release fractions are too low to produce doses large enough to exceed the dose thresholds for early fatalities, even for the 0.5% of the population that does not evacuate.
142
,K r LRevision 3- 10/28/2010 8:18:00 AM 7.3.3.1 Sensitivity Analyses of the Size of the Evacuation Zone and the Evacuation Start Time.
The base case analysis included evacuation of the 10-mile EPZ and a shadow evacuation cohort between 10 and 20 miles. For the unmitigated STSBO scenario, three additional calculations were performed to assess variations in the protective actions.
Sensitivity #1 - Evacuation of a 16-Mile Circular Area In this calculation, the evacuation zone is expanded to 16 miles. Shadow evacuation occurs from within the 16- to 20-mile area.
Sensitivity #2 - Evacuation of a 20-Mile Circular Area In this calculation, the evacuation zone is expanded to 20 miles. No shadow evacuation is considered.
Sensitivity #3 - Delayed Evacuation of a 10-Mile Circular Area This calculation is identical to the base case case described above, with the exception that implementation of protective action is delayed by 30 minutes.
The results of all three sensitivity analyses are presented in Table 27 and are also shown in Figure 83.
Table 27 Effect of Size of Evacuation Zone on Conditional, Mean, LNT, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities are for the Unmitigated Short-Term Station Blackout Scenario.
Radius of Base case Sensitivity #1 Sensitivity #2 Sensitivity #3 Circular Area (mi) 10-Mile 16-Mile 20-Mile 10-Mile Delayed Evacuation Evacuation Evacuation Protective Action 10 2.3 '10-4 5.4 '10-. 5.5 '10-4 2.3 "10-4 20 4.9 10-4
' 3.8 4 2.6 "10-4 4.9, 10-4 30 3.3 '10-4 3.0 '10-4 2.6' i0-4 3.3- 10-4 40 2.1104 1.9.10-4 1.710-4 2.110.4 50 1.6 '10-4 1.5 '10"4 1.4 '10 .4 1.6 "10-4 143
Revision 3- 10/28/2010 8:18:00 AM 6.E-4 ---------
to 5.E-4 . . Baseline (a 116-mile 0ii Evacuation' S-4.E-4 020-mile Evacuation:
E 3.E-4 0 2.E-4 U
.2 1.E-4 "
0 O.E+O 10 20 30 40 50 Radius of Circular Area (mi)
Figure 83 Conditional, i.e., assuming accident occurs, mean, LNT, latent-cancer-fatality probabilities from the Peach Bottom unmitigated STSBO scenario for residents within a circular area of specified radius from the plant. The plot shows the dependence of probabilities on the size of the evacuation zone.
Although expanding the size of the evacuation zone decreases the latent cancer fatality risk beyond the 10 mile radius for the unmitigated SBO, there is an increase in the risk within 10 miles associated with this change. Beyond a 20 mile radius, the risk reduction associated with increasing the size of the evacuation zone is nominal. Prompt-fatality risk remains zero for these sensitivity cases.
The results show that an ad-hoc increase in the size of the evacuation zone, from 10 mi to either 16 or 20 mi, approximately doubles the risk within the 10-mi EPZ, but decreases the risk to the population within a 20-mi radius for the STSBO scenariod examined here. For the entire population within a 50-mi radius, the advantage of a larger evacuation zone is slight.
7.3.4 Evaluation of the Effect of the Seismic Activity on Emergency Response Earlier sections in Chapter 7 provide offsite health consequence estimates for unmitigated sensitivity cases that reflect the effects of the seismic event on emergency response involving mitigation of the accident. However, these earlier sections do not reflect the effects of the seismic event on public evacuation. This subsection provides consequence estimates that also include the effects of the seismic event on public evacuation. The consequence estimates below were developed for the STSBO without RCIC blackstart. Although this is the lowest frequency and lowest risk scenario, this scenario was chosen for this analysis because it was believed to be the most likely to show an increase in risk. Seismic effects of EP are site-specific but with no substantial effect on health consequences. Although sirens fail, alternative notification is adequate and a larger shadow evacuation is expected although bridges fail, they are not key to evacuation; and adequate road network remains and evacuation speeds are unchanged. In 144
ERevision 3 - 10/28/2010 8:18:00 AM addition, accident progression timing predicted by realistic analysis is delayed so that there is some margin for EP activation and execution.
Table 28 Conditional, i.e., assuming a'ccident occurs, Mean, LNT, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities Are for the Unmitigated STSBO Scenario and Compare the Unmodified Emergency Response (ER) and ER Adjusted to Account for the Effect of Seismic Activity on Evacuation Routes and Human Response.
Radius of Unmodified ER ER Adjusted for Circular Area (mi) Seismic Effects 10 2.3'10-4 2.3'10-4 20 4.9- 10-4 4.5. 10.4 30 3 .3 "10-4 3 .2 '10-4 40 2.1. 10-4 2.0 10-4 50 1.6- 10-4 1.6'10-4 7.3.5 Evaluation of SST1 Source Term An objective of SOARCA is to update quantification of consequences in earlier studies such as the 1982 Siting Study. However, because the 1982 Siting Study estimated latent cancer fatalities out to 500 miles whereas SOARCA estimates are limited to 50 miles, analysis are performed in this sectionto better understand the change in LCF risk associated with use of current state-of-the-art analysis. The approach used in this analysis was to substitute the SST1 source term into a MACCS input file for a SOARCA scenario. The MACCS inplut file chosen was the one developed for the LSTBO without B.5.b mitigation. The assumptions in this imput file are identical with the ones for the STSBO without RCIC blackstart with the exception that 4 of the 5 cohorts begin evacuating 30 minutes earlier in the STSBO without RCIC blackstart.
The SST1 source term is described in the Sandia Siting Study report as follows:
" Severe core damage
- Essentially involves loss of all installed safety features
- Severe direct breach of containment An exact scenario and containment failure mechanism (e.g., hydrogen detonation, direct containment heating, or alpha-mode failure) are not specified.
Notification time (i.e., sounding a siren to notify the public that a general emergency has been declared) for the Peach Bottom unmitigated LTSBO occurs at 1.5 hr. Declaration of a general emergency occurs at 45 min. and it takes an additional 45 min. to notify the public. Notification of the public is thus coincident with the beginning of release for the SST1 source term (cf.,
Table 20), which occurs 1.5 hr after accident initiation. The general public begins to evacuate 60 minutes later, which is 2.5 hrs after accident initiation. The start of evacuation for the general public for this scenario occurs 30 minutes later than the start of evacuation for the first cohort in the Sandia Siting Study. The largest segment of the population in the Sandia Siting Study began 145
lop Revision 3 - 10/28/2010 8:18:00 AM to evacuate 1.5 hrs later, 4 hr after accident initiation. Thus, the evacuation used in this sensitivity study is earlier, on the whole, than that used at the time of the Sandia Siting Study.
The purpose of this sensitivity study is simply to show the impact of the improvements made in the source term analysis methods and practices on the consequence results.
While the Sandia Siting Study treated emergency response very simplistically, a major emphasis of the SOARCA project is to treat all aspects of the consequence analysis as realistically as possibleThus, in the end it was decided to keep the emergency response parameters the same as in the unmitigated LTSBO scenario.
Table 29 shows the latent-cancer-fatality risks for a release corresponding to the SSTI source term occurring at Peach Bottom. Error! Reference source not found. compares the LNT risks for the SST 1 source term with those for the largest source term calculated for Peach Bottom in this study, the unmitigated STSBO. The LNT risk within 10 miles for the SSTl source term is about a factor of 25 higher than for the unmitigated STSBO; the 10-mile risk using a 620 mrem/yr dose-truncation criterion is a factor of 500 higher. At larger distances, the risks are less disparate. The ratio is a factor of 3 within 50 miles. The ratio is about 7 for the risk within 50 miles when the 620 mrem/yr dose-truncation criterion is applied.
Table 29 Conditional, i.e., assuming accident occurs, Mean, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities are based on the SST1 Source Term from the Sandia Siting Study.
Radius of T NT 620 5 rem/yr; Circular Area (mi) LNT mrem/yr 10 rem lifetime 10 6.0."10- 5.8"10-3 5.9'10-'
20 T 2.0107 T1.h810. 1.9'10-3 50 Z.7"1- 31.7 10-' 3.8.10"4 Table 30 Conditional, i.e., assuming accident occurs, Mean, LNT, Latent-Cancer-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities Are Based on the SST1 Source Term from the Sandia Siting Study and the unmitigated STSBO scenario.
Radius of Unmitigated Circular Area (mi) SSTI STSBO 10 6 .0 '10-' 2 .3 '10-4 20 "-3 2 .0 10 ' -4 4 .0 10 50 4 .7 "10-4 1.6 '10-4 The maximum risk is within 10 miles for the SST1 source term, which is partially because emergency response is not rapid enough to prevent exposures within the EPZ during the emergency phase. This is expected since release begins at the same time as notification of the public and, therefore, before evacuation begins.
146
ý O//A C LRevision 3 - 10/28/2010 8:18:00 AM A notable feature of the risks presented in Table 29 is that the choice of dose truncation criterion has a minor influence on risk. This is very different than the SOARCA accident scenarios discussed in preceding subsections. Figure 84 provides some insights into this behavior. For the SSTl source term, nearly all of the risk, especially at short distances from the plant, is from exposures that occur during the emergency phase. Because a significant fraction of this dose is received over a short period of time, and the dose is large due to the large source term, the values for the dose truncation criterion have little influence on predicted risks. Again, this is a very different trend than is observed for the current, state-of-the-art source terms.
6.E-3 aEARLY]_
5.E-3 4.E-3 S3.E,3 2.E-3
.J 1.E-3 0.E+O 10 20 50 Radius of Circular Area (ml)
Figure 84 Conditional, i.e., assuming accident occurs, mean, LNT, latent-cancer-fatality probabilities (dimensionless) from the SST1 source term for residents within a circular area of specified radius from the Peach Bottom plant. The plot shows the probabilities from the emergency phase (EARLY), long-term phase (CHRONC), and the two phases combined.
Table 31 shows the risk of prompt fatalities for several circular areas of specified radii centered at the plant. Unlike the source terms presented above, the predicted prompt-fatality risks are greater than zero. The SST1 release fractions are more than large and early enough to induce prompt fatalities for members of the public who live close to the plant.
The NRC quantitative health object (QHO) for prompt fatalities is generally interpreted as the unconditional risk within I mile of the exclusion area boundary. For Peach Bottom, the exclusion area boundary is 0.5 mile from the reactor building from which release occurs, so the outer boundary of this 1-mile zone is at 1.5 miles. The closest MACCS2 grid boundary to 1.5 miles used in this set of calculations is at 1.3 miles. Using the risk within 1.3 miles should reasonably approximate the risk within 1 mile of the exclusion area boundary. The frequency stated for the 147
Revision 3 - 10/28/2010 8:18:00 AM SST1 source term in the Sandia Siting Study [25] is 10-5/year, so the unconditional risk of a prompt fatality for this source term is approximately 5.8" 10 8/year. Even for this very large source term, this risk is well below the QHO (5x10-7/year).
Table 31 Conditional, i.e., assuming accident occurs, Mean, Prompt-Fatality Probabilities (dimensionless) for Residents within the Specified Radii of the Peach Bottom Site. Probabilities are for the SST1 Source Term from the Sandia Siting Study.
Radius of Probability of a Circular Area (mi) Prompt Fatality (dimensionless) 1.0 5.7.10-'
1.3 5 .8 "10-3 2.0 2.8 10.3 2.5 1.9"10-1 3.0 1.3'10-'
3.5 7.1"10-4 5.0 2.0'10-4 7.0 9.0'10-1 10.0 3.9"10.5 148
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XE *1 (0ý L Revision 3- 10/28/2010 8:18:00 AM
8.0 REFERENCES
[1] Kolaczkowski, A.M., et al. NUREG/CR-4550, Vol. 4, Rev. 1, Part 1, SAND86-2084.
"Analysis of Core Damage Frequency: Peach Bottom, Unit 2, Internal Events." Sandia National Laboratories: Albuquerque, NM. August 1989.
[2] Leonard, M.T., Nause, R.C., and Gauntt, R.O.. SAND2008-xxxx. "A General Purpose MELCOR Model of a BWR/4 Mark I Nuclear Power Plant." Sandia National Laboratories: Albuquerque, NM. 2008.
[3] Carbajo, J.J. NUREG/CR-5942, ORNL/TM-12229. "Severe Accident Source Term Characteristics for Selected Peach Bottom Sequences Predicted by the MELCOR Code."
Oak Ridge National Laboratory: Oak Ridge, Tennessee. July 1993.
[4] Peach Bottom Atomic Power Station, Special Event Procedure - SE-11.
[5] Peach Bottom Atomic Power Station, Trip Procedure T-101.
[6] Soffer, L, et al., NUREG-1465, "Accident Source Terms for Light-Water Nuclear Power Plants," U.S. Nuclear Regulatory Commission, Washington, DC, February, 1995
[7] Gauntt, R.O., et al., NUREG/CR 6119, Vol. 1, Rev. 3. "MELCOR Computer Code Manuals, Vol. 1: Primer and User's Guide, Version 1.8.6." NRC: Washington, DC. 2005.
[8] Laur, M.N., "Meeting with Sandia National Laboratories and an Expert Panel on MELCOR/MACCS Codes in Support of the State of the Art Reactor Consequence Analysis Project," Memo to J.T. Yerokun, Agency Document Access and Management System Accession Number ML062500078, U.S. Nuclear Regulatory Agency, Washington, DC, September, 2006.
[9] Nuclear Regulatory Commission. NUREG 1150. "Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants." U.S. Nuclear Regulatory Agency:
Washington, DC. 1990.
[10] Harper, F. T., et al. NUREG-CR-4551, SAND86-1309, Vol. 2, Rev. 1, Part 2.
"Evaluation of Severe Accident Risks: Quantification of Major Input Parameters, Experts' Determination of Containment Loads and Molten Core Containment Interaction Issues," Sandia National Laboratories: Albuquerque, NM. April 1991.
[11] Theofanous, T.G., et al. NUREG/CR-5423. "The Probability of Liner Failure in a Mark I Containment." NRC: Washington D.C. 1989.
[12] Theofanous, T.G., et al. NUREG/CR-6025. "The Probability of Mark I Failure by Melt -
Attack of the Liner." NRC: Washington D.C. November 1993.
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[13] ORNL/TM-2005/39, Version 5.1, Vols. I-11. "SCALE: A Modular Code System for Performing Standardized Computer Analyses for Licensing Evaluations." ORNL: Oak Ridge, Tennessee. November 2006.
[14] American Institute of Steel Construction, Inc., "Manual of Steel Construction," Ninth Edition.
[15] Philadelphia Electric Company, "Individual Plant Examination, Peach Bottom Atomic Power Station, Units 2 and 3," August 1992.
[16] Peach Bottom Atomic Power Station Procedure, "ReactorPressure Vessel Reassembly."
[17] Personal communication from Thomas R. Loomis of Exelon Corporation to Abdul Sheikh of NRC about torque value for the 2 '/2" diameter reactor head flange bolts, dated October 31, 2006.
[18] Nuclear Regulatory Commission (NRC). NUREG-0654/FEMA-REP-1, Rev. 1. "Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in Support of Nuclear Power Plants." November 1980.
[19] Nuclear Regulatory Commission (U.S.) (NRC). NUREG/CR - 6864, SAND2004-5901.
"Identification and Analysis of Factors Affecting Emergency Evacuations." Washington D.C.:
NRC. January 2005.
[20] Nuclear Regulatory Commission (U.S.) (NRC). NUREG/CR-6953, Vol. 1. SAND2007-5448P.
"Review of NUREG-0654, Supplement 3, "Criteria for Protective Action Recommendations for Severe Accidents." Washington D.C.: NRC. December 2007.
[21] Nuclear Regulatory Commission (U.S.) (NRC). NUREG/CR-6863, SAND2004-5900.
"Development of Evacuation Time Estimate Studies for Nuclear Power Plants." Washington D.C.: NRC. January 2005.
[22] Oak Ridge National Laboratory. "Oak Ridge Evacuation Modeling System (OREMS)." Oak Ridge National Laboratory: Oak Ridge, Tennessee. July 2003.
[23] Rogers, G.O., et al. "Evaluating Protective Actions for Chemical Agent Emergencies."
ORNL-6615. ORNL: Oak Ridge, Tennessee. April 1990.
[24] Chanin, D.I., Young, M.L. NUREG/CR-6613, SAND97-0594. "Code Manual for MACCS2: Volume 1, User's Guide." NRC: Washington D.C. 1998.
[25] Aldrich, D.C., et al., NUREG/CR-2239, SAND81-1549. "Technical Guidance for Siting Criteria Development." NRC: Washington D.C. 1992.
[26] Haskin, F. E., et al., "Probabilistic Accident Consequence Uncertainty Analysis, Early Health Effects Uncertainty Assessment," NUREG/CR-6545, 1997.
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[27] Harper, F. T., et al., "Probabilistic Accident Consequence Uncertainty Analysis, Dispersion and Deposition Uncertainty Analysis," NUREG/CR-6244, 1994.
[28] "Evacuation Time Estimates for the Peach Bottom Station Plume Exposure Pathway Emergency Planning Zone." Exelon Nuclear. August, 2003.
[29] Transportation Research Board (TRB). "Highway Capacity Manual." National Research Council. Washington D.C. 2000.
[30] Nuclear Regulatory Commission (NRC). NUREG-6953, Volume 2. "Review of NUREG-0654, Supplement 3, 'Criteria for Protective Action Recommendations for Severe Accidents' - Focus Group an'd Telephone Survey." October 2008.
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PDA Revision 3 - 10/28/2010 8:18:00 AM APPENDIX A.1 PEACH BOTTOM RADIONUCLIDE INVENTORY 154
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leyl Revision 3 - 10/28/2010 8:18:00 AM The following tables summarize the radionuclide core inventory for the Peach Bottom plant at the time of shutdown for each of the accident progression scenarios considered in this report.
Non-fuel activation products, such as Co-58 and Co-60, were not included in the inventory analysis. While these isotopes are important in terms of worker dose during routine maintenance, their activities are several orders of magnitude lower than most of the isotopes listed below and do not contribute much to offsite doses. Thus, the omission of these isotopes has a minor effect on the SOARCA results.
Table A. 1-1 Peach Bottom radionuclide core inventory and class definition.
Radionuclide Class Representative Name Element Member Elements Total Mass (kg)
Noble Gas Xe He, Ne, Ar, Kr, Xe, 531.7 Rn, H, N Alkali Metals Cs Li, Na, K, Rb, Cs, 323.0 Fr, Cu
- Alkaline Earths Ba Be, Mg, Ca, Sr, Ba, 235.6 Ra, Es, Fm Halogens I F, Cl, Br, I, At 19.9 Chalcogens Te 0, S, Se, Te, Po 49.1 Platinoids Ru Ru, Rh, Pd, Re, Os, 342.8 Ir, Pt, Au, Ni Early Transition Mo V, Cr, Fe, Co, Mn, 400.2 Elements Nb, Mo, Tc, Ta, W Tetravalent Ce Ti, Zr, Hf, Ce, Th, 1555.5 Pa, Np, Pu, C Trivalents La Gd, Tb, Dy, Ho, Er, 1793.7 Tm, Yb, Lu, Am, Cm, Bk, Cf Uranium U U 132794.0 More Volatile Main Cd Cd, Hg, Zn, As, Sb, 6.6 Group Pb, TI, Bi Less Volatile Main Sn Ga, Ge, In, Sn, Ag 9.6 Group Table A. 1-2 Peach Bottom noble gas radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Kr-85 3.79E+16 Kr-85m 1.03E+18 Kr-87 2.05E+18 Kr-88 2.77E+18 156
Revision 3 - 10/28/2010 8:18:00 AM Xe-1 33 7.02E+18 Xe-135 2.58E+18 Xe-135m 1.43E+18 Table A. 1-3 Peach Bottom alkali metals radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Cs-134 3.61E+17 Cs-136 1.43E+17 Cs-1 37 3.74E+17 Rb-86 4.38E+15 Rb-88 2.80E+18 Table A. 1-4 Peach Bottom alkali earths radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Ba-139 6.48E+18 Ba-140 6.27E+18 Sr-89 3.79E+18 Sr-90 2.98E+17 Sr-91 4.77E+18 Sr-92 5.02E+18 Ba-137m 3.55E+17 Table A. 1-5 Peach Bottom halogen radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq) 1-131 3.38E+18 1-132 4.99E+18 1-133 7.15E+18 1-134 8.14E+18 1-135 6.80E+18 157
Opof 6R(pelL Revision 3 - 10/28/2010 8:18:00 AM Table A.1-6 Peach Bottom chalcogen radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Te-127 2.71E+17 Te-127m 4.33E+16 Te-129 8.17E+17 Te-129m 1.55E+17 Te-131m 6.03E+17 Te-132 4.85E+18 Te-131 2.89E+18 Table A. 1-7 Peach Bottom platinoid radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Rh-1 05 2.77E+18 Ru-1 03 4.83E+18 Ru-1 05 3.03E+18 Ru-106 1.31E+18 Rh-103m 4.82E+18 Rh-106 1.44E+18 Table A. 1-8 Peach Bottom early transition element radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Nb-95 6.07E+18 Co-58 0.OOE+00 Co-60 0.OOE+00 Mo-99 6.52E÷18 Tc-99m 5.83E+18 Nb-97 6.11E+18 Nb-97m 5.77E+18 Table A. 1-9 Peach Bottom tetravalent radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Ce-141 5.89E+18 Ce-143 5.64E+18 Ce-144 4.19E+18 Np-239 5.61E+19 Pu-238 6.78E+15 Pu-239 1.37E+15 158
P11ie AL Revision 3 - 10/28/2010 8:18:00 AM Pu-240 1.13E+15 Pu-241 3.87E+17 Zr-95 6.11E+18 Zr-97 6.08E+18 Table A. 1-10 Peach Bottom trivalent radionuclide class specific isotopic activity at the time of reactor shutdown Isotope Activity (Bq)
Am-241 5.23E+14 Cm-242 9.57E+16 Cm-244 4.70E+15 La-140 6.48E+18 La-141 5.86E+18 La-142 5.70E+18 Nd-147 2.32E+18 Pr-143 5.55E+18 Y-90 3.03E+17 Y-91 4.82E+18 Y-92 5.05E+18 Y-93 5.58E+18 Y-91m 2.75E+18 Pr-144 4.20E+18 Pr-144m 5.85E+16 159