ML22186A105
| ML22186A105 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 07/05/2022 |
| From: | Ameren Missouri, Union Electric Co |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22186A103 | List: |
| References | |
| LDCN 21-0015, ULNRC-06754 | |
| Download: ML22186A105 (25) | |
Text
Attachment to ULNRC-06754 July 5, 2022 Ameren Missouri Response to NRC RAIs 24 pages
Enclosure to U LNRC-06754 Page 1 of 24 Ameren Missouri Response to NRC RAIs On September 28, 2021 Union Electric Company, dba Ameren Missouri, submitted a license amendment request (LAR) for Callaway Plant, Unit No. 1 (Callaway) to the U.S. Nuclear Regulatory Commission (NRC). Pursuant to Title 10 of Code ofFederaiRegulations (10 CFR)
Section 50.90, Application for amendment of license, construction permit, or early site permit, and 10 CFR 50.67, Accident Source Term, the licensee requested, in part, to incorporate the alternative source term (AST) dose analysis methodology into the Callaway licensing basis. As the U.S. Nuclear Regulatory Commission (NRC) staff is continuing to review the application, it recently determined that additional information is required in order to complete the review of the subject LAR. The NRC staffs request for additional information (RAI), consisting of four individual requests, RAI No. 1 (with four parts), RAI No. 2 (with three parts), RAI No. 3, and RAI No. 4 (with three parts), was electronically transmitted on June 2, 2022.
RAI No. I (RAI-1):
Regulatory Requirement: The regulation at 10 CFR 50.67(b)(1) states that [t]he application shall contain an evaluation of the consequences of applicable design-basis accidents previously analyzed in the safety analysis report. In turn, the regulation at 10 CFR 50.67(b)(2) requires that the applicants analysis demonstrates with reasonable assurance that the dose limits at any point on the exclusion area boundary (EAB) and the outer boundary of the low population zone (LPZ), and at the control room, are met. Those dose analyses require, as direct inputs, dispersion parameters, which are based on using appropriate dispersion models that rely, in part, on the input of representative Meteorological data. The analyses above pertain to offsite impacts.
In addition, General Design Criterion 19, Control room, in Appendix A to 10 CFR Part 50 applies, in part, to the analysis of onsite impacts at the control room and access to it during radiological accident conditions. Further, radiological protection equivalent to that at the control room is called for at the technical support center (TSC) by: NUREG-0696, Functional Criteria for Emergency Response Facilities, Final Report, dated February 1981 (ML051390358) and by Supplement 1 to NUREG-0737, Clarification of TMI [Three Mile Island] Action Plan Requirements, Supplement No. 1, dated January 1983 and reprinted February 1989 (ML102560009), Section 8.2.1. Item (f).
Guidance on implementing the overall AST methodology is given in:
. Regulatory Guide (RG) 1.183, Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors, Revision 0, July 2000 (ML003716792).
Guidance on modeling offsite dispersion parameters is given by:
. RG 1.145, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants, Revision 1 (November 1 982), Reissued February 1 983 (ML003740205).
. NUREG/CR-2858, PAVAN An Atmospheric-Dispersion Program for Evaluating Design-Basis Accidental Releases of Radioactive Materials from Nuclear Power Stations, November 1 982 (MLI 2045A1 49).
Enclosure to U LNRC-06754 Page 2 of 24
. NUREG/CR-2260, Technical Basis for Regulatory Guide 1.145, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants, October 1981 (ML12045A197).
Guidance on modeling onsite dispersion modeling parameters is given by:
. RG I 1 94, Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants, Revision 0, June 2003 (ML031530505).
. NUREG/CR-6331 Atmospheric Relative Concentrations in Building Wakes, Revision I, May 1997 (ML17213A190).
Guidance on meteorological monitoring is given by:
RG I .23, Meteorological Monitoring Programs for Nuclear Power Plants, Revision 1 March 2007 (ML070350028).
Background:
The Licensees offsite dispersion modeling analysis was based on the PAVAN NAI code and used to estimate atmospheric dispersion factors (XIQs) at the EAB and outer boundary of the LPZ. PAVAN-NAI appears to be essentially the same as the NRC-approved PAVAN dispersion model. PAVAN implements RG 1.145, the associated users guidance in NUREG/CR-2858, and the technical basis document for the regulatory guide in NUREG-CR 2260. Enclosure 14 to the December 1, 2021, supplemental submittal discusses the differences between PAVAN-NAI and PAVAN. Slight differences between the input to and output of the two codes were determined and had to be accounted for in the NRC staffs initial review.
The Licensee chose to input Met data to PAVAN-NAI in the form ofjoint frequency distributions (JFDs) of wind speed, wind direction, and atmospheric stability. This is consistent with the NRCs PAVAN model. According to Enclosure 14, the other approach available in PAVAN-NAI is to input hourly Met data in the ARCON96 format, a provision not available in the PAVAN model. The period of record (POR) of onsite Met data covers four years from 2013 to 2016.
Enclosure I of the December 1 2021 supplemental submittal indicates that hourly atmospheric stability values were determined consistent with RG I .23 and that wind speed and direction values were determined by scalar (as opposed to vector) averaging.
The Licensee provided PAVAN-NAI input and output files that correspond to Enclosures 12 and I 3, respectively, of the supplemental submittal. These files were in response to Question 21 c from a June 14, 2018, pre-application meeting with the Licensee (ML18215A375). This question was reiterated during a second pre-application meeting on March 15, 2021 (ML2I 103A003).
The model runs evaluated accident releases from a variety of potential sources located close to the containment structure. The runs designated as RB and RWST model releases from the reactor building and refueling water storage tank, respectively. Distances to the EAB and LPZ are consistent with the distances from the midpoint between the Unit I reactor building and the cancelled Unit 2 reactor building to each offsite boundary as given in the UFSAR (i.e., I ,200 meters (m) and 4,023 m, respectively). PAVAN-NAI was configured to account for and to exclude enhanced building wake effects on plume dispersion, as available in the PAVAN model.
Enclosure to U LNRC-06754 Page 3 of 24 From these model runs, only the bounding XIQ values for the EAB and LPZ, as summarized in Table 3-23 (see Enclosure 1 of the supplemental submittal) and that account for building wake effects, appear to be directly input to the offsite dose analyses. Further, for the RB and RWST model runs, the respective 0- to 2-hour X/Qs in Table 3-23 are assigned to all averaging periods for the EAB distance.
Additional PAVAN-NAI input and output files were also provided in Enclosures 1 2 and I 3.
These files appear to be source- and distance-specific. Only one receptor distance is evaluated in these model runs, and the same distance is assigned, in a given model run, to all 16 direction sectors. The distances entered for these other runs presumably represent the distances to the EAB from a potential release point other than the RB or RWST and appear to correspond to sources modeled by the Licensee using the ARCON96-NAI code.
Request:
a) An input error was identified in each of the RB, RWST, and additional PAVAN-NAI model runs. Tables 3-8 through 3-14 (see Enclosure 1 ofthe supplemental submittal) list the frequencies of calm wind conditions for stability classes A thru G in term of hours with wind speeds less than or equal to 0.5 meters per second (m/sec). They are: 0, 0, 0, 1 5, 85, 1 36, and I 98, respectively. PAVAN-NAI appears to follow the format for Card Type 8 of the PAVAN code. Card Type 8 calls for these input entries to be right-justified every live (5) columns. Upon review, the first three entries for stability classes A, B, and C were determined to be 0, 0, 0, consistent with that format. Likewise, the last two entries for stability classes F and G were determined to be formatted correctly as 136 and 198, respectively.
However, the entry for stability class D (i.e., 15) was determined to be misaligned. The 1 digit was right-justified in the fourth input field but the 5 digit was placed in the first column of the fifth input field, followed by two blank spaces, and then the properly placed entry for stability class E (i.e., 85) right-justified in the fifth input field. The effect of this error was further complicated by what is believed to be differences between the compiler used for PAVAN-NAI and that for the NRC-approved PAVAN code. That is, read statements for the former appear to account for all entries within a given field even if the entries are not continuous. The value assigned by PAVAN-NAI to the fifth input field was 585. This was verified by inspecting each of the PAVAN-NAI output files which echoed the input for Card Type 8 as 0, 0, 0, 1 585, 1 36, 1 98. The PAVAN echo in the output and XIQ values were different.
After recognizing and addressing the apparent difference in read statements, the NRC staff was able to reproduce the Licensees XIQ results using the incorrect calm frequencies as input. The effect of this error on the offsite X/Qs was not immediately known because the discrepancies were associated with stability classes D and E.
Nevertheless, the increase for stability class E was almost seven-fold. As a result, the influence on the XIQ frequency distribution was investigated because dose calculations could be directly affected. The NRC staff then re-ran the RB, RWST, and additional offsite model runs using the calm frequencies from Tables 3-8 thru 3-14 as input (i.e., 0, 0, 0, 15, 85, 136,198). The corrected results show that the offsite XIQ5 at the EAB and LPZ in the LAR submittal are slight overestimates by about 3.5 percent or less depending on the release scenario, the receptor, and averaging time.
Enclosure to ULNRC-06754 Page 4of24 Therefore, the Licensee should either: (a) decide to let the PAVAN-NAI modeling results and related dose calculations stand unchanged from the September 28, 2021 LAR ,
submittal, but formally acknowledge this error since the PAVAN-NAI input and output files were provided on the docket as supplemental information pursuant to the LARs acceptance, or (b) revise the PAVAN-NAI offsite dispersion modeling, and any affected dose calculations, related text, tables, and figures.
b) Correctthe labeling in Tables 3-9 through 3-14 of Enclosure I to the December 1, 2021, supplemental submittal. In the upper left-hand portion of these table bodies, the labels incorrectly read Atmospheric Stability: Class A for all seven stability classes (A to G).
This discrepancy only affects the labeling, not the individual table contents or the table titles. The labels should be corrected to match stability classes B through G in the corresponding tables.
c) Clearly explain the purpose and use of the PAVAN-NAI model input and output files (i.e.,
other than for the RB and RWST model runs) provided in Enclosures 1 2 and 13, respectively, of the supplemental submittal. This includes verifying: (a) what the distances entered in the input files are relative to (e.g., the EAB), (b) what potential source each run corresponds to, and (c) their relationship, if any, to the model runs using ARCON96-NAI .
U) To avoid confusion, and ifthe PAVAN-NAI modeling analysis is re-run based on RAI-la, the NRC staff recommends that the second entry for Card Type 3 of the model input be changed from Delta-I from I 0-60m to read Delta-I from 60-1 Om. This would be consistent with how the vertical temperature difference (Delta I) is calculated for determining the hourly stability class. The NRC staff verified, in this case, that the hourly Delta-T values reported in Enclosure 7 of the supplemental submittal and as used in the offsite and onsite dispersion modeling analyses, was determined correctly (i.e., based on the difference between the temperatures at the upper (60 m) minus the lower (10 m) measurement heights).
Ameren Response:
a) RAI-1 a correctly identified an input format error in the alignment of the stability class D entry on Card Type 8 of the Reactor Building (RB) and Refueling Water Storage Tank (RWST) PAVAN-NAI models of Enclosure 1 2. The misalignment of the stability class D entry in the fourth input field resulted in a defined number of 1 calm hour for stability class D and 585 calm hours for stability class E rather than the intended values of I 5 and 85, respectively. Underprediction of the stability class D calm hours and overprediction of the stability class E calm hours was confirmed to have produced a set of conservatively high atmospheric dispersion factors (X/Qs). The extent of this X/Q conservatism ranges from 0.3% to as much as 8.3% larger than would have been calculated with the intended values. As this error conservatively overpredicts the X/Q values and subsequently increases the doses at the Exclusion Area Boundary (EAB) and Low Population Zone (LPZ), the PAVAN-NAI models and Alternate Source Term (AST) dose analyses supporting the License Amendment Request (LAR) will not be revised at this time.
Enclosure to U LNRC-06754 Page 5 of 24 b) The typographical error in the stability class labeling of Tables 3-9 through 3-1 4 of Enclosure 1 has been corrected to reflect the appropriate stability class in the first cell of each table. The updated tables are provided below (as pages 6 through I I of this enclosure)
Enclosure to ULNRC-06754 Page 6of24 Table 3-9 Joint Frequency Distribution (in number of total hours) for Stability Class B Atmospheric Stability: Class B Period of Record: January 1 201 3 to December 31 2016 (based on lower wind speed instrument)
Maximum Wind_Direction Wind Speed N NNE NE ENE E ESE SE SSE S 55W SW WSW W WNW NW NNW Total (mis) 0.22 0
0.50 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.75 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.25 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 1.50 2 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 6 2.00 2 1 2 2 1 1 2 4 4 2 1 1 1 0 1 0 25 3.00 10 13 16 11 4 13 36 49 46 26 26 18 19 16 17 10 330 4.00 21 15 21 16 9 11 39 51 32 51 45 18 25 37 42 47 480 5.00 17 7 5 10 8 7 14 24 28 44 26 17 25 22 32 39 325 6.00 15 8 2 2 0 2 2 12 37 22 16 3 9 15 9 11 165 8.00 1 4 0 1 1 0 1 8 13 11 10 6 5 5 5 13 84 10.00 0 0 0 0 0 0 0 0 5 0 1 0 0 0 0 0 6 26.00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Total 68 49 47 42 23 35 94 149 165 156 125 64 84 95 106 120 1422
Enclosure to ULNRC-06754 Page 7 of 24 Table 3-10 Joint Frequency Distribution (in number of total hours) for Stabili ty Class C Atmospheric Stability: Class C Period of Record: January 1 201 3 to December 31 2016 (based on lower wind speed instrument)
Maximum Wind_Direction Wind Speed N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW Total (mis) 0.22 0
0.50 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.75 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1.00 1 0 1 0 0 0 0 0 1 0 1 1 0 0 0 0 5 1.25 0 1 0 0 0 0 0 1 1 0 2 0 0 0 0 0 5 1.50 0 2 0 1 1 1 5 3 6 1 2 1 2 0 3 1 29 2.00 6 4 9 7 5 7 26 12 16 11 9 15 19 9 2 165 3.00 30 30 35 29 23 26 99 96 76 76 42 29 39 46 36 36 748 4.00 25 37 17 23 16 21 66 75 71 57 45 26 34 41 46 41 641 500 34 16 8 11 7 17 19 28 34 52 32 13 17 20 19 40 367 6.00 17 11 2 2 2 6 3 12 32 26 14 10 12 18 16 26 209 8.00 5 0 0 1 1 0 0 9 29 12 3 5 5 10 11 6 97 10.00 0 0 0 0 0 0 0 1 2 5 0 0 0 0 0 0 8 26.00 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 Total 118 101 72 74 58 76 199 251 264 245 152 94 126 154 140 152 2276
Enclosure to ULNRC-06754 Page 8 of 24 Table 3-1 1 Joint Frequency Distribution (in number of total hours) for Stabili ty Class D Atmospheric Stability: Class D Period of Record: January 1 201 3 to December 31 2016 (based on lower wind speed instrument)
Maximum Wind Direction Wind Speed N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW Total (mis) 0.22 0.50 4 0 1 0 j_ 2 1 0 2 0 0 0 0 3 0 1 11 0.75 3 4 5 2 3 1 0 3 2 3 3 2 7 3 3 48 1.00 19 6 8 13 8 8 20 11 15 11 11 15 12 8 15 4 184 1.25 11 9 6 7 12 20 13 7 8 12 8 7 12 13 8 171 I .50 26 33 42 43 50 68 40 41 23 32 20 34 40 40 29 597 2.00 73 87 81 70 105 170 146 86 60 72 48 104 108 92 81 1444 3.00 203 212 208 213 209 282 471 344 220 163 171 118 172 255 285 277 3803 4.00 291 201 155 135 139 175 254 249 220 196 159 86 128 234 236 338 3196 5.00 283 138 74 49 60 94 73 139 187 137 106 63 123 174 195 203 2098 6.00 156 55 17 16 11 62 133 2i 73 59 33 88 106 116 127 1095 8.00 66 20 22 9 4 4 1 31 183 48 35 29 71 61 49 79 712 10.00 5 0 7 0 0 0 0 16 4 3 4 7 1 1 9 57 26.00 0 0 0 0 0 0 0 0 0 0 1 2 1 0 0 1 5 Total 1136 766 617 570 562 751 1090 1035 1113 725 664 429 749 1009 1045 1160 13421
Enclosure to U LNRC-06754 Page 9o124 Table 3-12 Joint Frequency Distribution (in number of total hours) for Stability Class E Atmospheric Stability: Class E Period of Record: January 1 201 3 to December 31 2016 (based on lower wind speed instrument)
Maximum Wind_Direction Wind Speed N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW Total (mis) 0.22 26 0.50 3 3 3 2 9 4 10 4 2 3 0 2 4 5 2 3 59 0.75 6 2 8 6 9 8 10 6 8 9 6 7 8 12 12 7 124 1.00 23 22 17 20 25 22 39 33 22 18 22 17 26 36 31 13 386 1.25 12 15 16 15 12 18 43 18 19 11 17 26 17 37 33 21 330 I .50 28 45 40 41 39 59 1 49 53 33 22 35 42 41 61 48 42 778 2.00 92 68 80 81 94 127 327 180 77 57 70 79 61 94 125 87 1699 3.00 158 125 118 93 132 167 464 632 308 215 186 132 182 168 182 208 3470 400 72 34 24 27 47 65 136 330 41 1 229 151 85 151 71 68 94 1995 5.00 11 6 3 8 14 26 133 247 103 47 32 52 33 19 22 763 6.00 1 1 0 0 7 5 52 143 47 12 4 19 9 9 7 319 8.00 1 0 0 0 0 2 23 65 16 3 5 4 0 1 1 124 10.00 0 0 0 0 0 0 0 2 1 0 0 2 1 0 1 1 8 26.00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Total 407 321 319 288 375 491 1211 1466 1336 730 549 433 566 526 531 506 10055
Enclosure to U LNRC-06754 Page 10 of 24 Table 3-13 Joint Frequency Distribution (in number of total hours) for Stability Class F
Atmospheric Stability: Class F Period of Record: January 1 201 3 to December 31 2016 (based on lower wind speed instrument)
Maximum Wind_Direction Wind Speed N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW Total (mis) 0.22 40 0.50 10 4 3 6 9 12 12 7 5 2 3 3 7 3 6 4 96 0.75 7 6 9 13 10 16 23 16 15 7 7 4 14 7 6 9 169 too 22 27 31 23 29 37 68 37 22 12 17 22 26 38 26 29 466 1.25 24 17 22 22 24 24 72 35 14 13 16 18 13 23 22 4 363 1.50 24 31 48 48 39 53 140 89 34 39 28 28 19 61 66 21 768 2.00 58 39 37 40 28 46 147 229 93 66 74 30 34 65 86 49 1121 3.00 33 25 19 18 12 15 93 550 236 118 121 38 35 44 38 81 1476 4.00 2 I 0 0 1 0 1 96 123 63 28 6 6 0 0 5 332 5.00 0 0 _Q_ 0 0 0 2 2 15 6 0 2 1 0 0 0 28 6.00 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 8.00 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 10.00 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 26.00 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0 0 Total 180 150 169 170 152 203 558 1063 558 326 294 151 155 241 250 202 4822
Enclosure to U LNRC-06754 Page 11 of 24 Table 3-14 Joint Frequency Distribution (in number of total hours) for Stability Class G Atmospheric Stability: Class G Period of Record: January 1 201 3 to December 31 2016 (based on lower wind speed instrument)
Maximum Wind_Direction Wind Speed N NNE NE ENE E ESE SE SSE S 55W SW WSW W WNW NW NNW Total (mis) 0.22 66 0.50 7 16 12 6 8 5 15 14 13 4 4 2 8 6 5 7 132 0.75 11 15 9 11 10 13 20 18 19 10 7 9 6 5 4 10 177 1 .00 34 32 31 18 16 15 41 60 29 10 18 12 11 23 29 15 394 1.25 14 19 15 9 5 7 12 37 15 7 6 6 5 19 22 12 210 1.50 25 25 34 9 7 8 27 60 26 20 11 9 7 24 29 30 351 2.00 26 23 15 6 2 2 19 79 37 17 13 4 6 14 27 29 319 300 5 3 1 0 0 0 6 117 32 13 7 1 2 3 18 10 218 4.00 0 0 0 0 1 0 0 28 9 2 2 0 0 0 0 0 42 5.00 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 6.00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8.00 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 10.00 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 26.00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Total 122 133 117 59 49 50 140 415 181 83 68 43 45 94 134 113 1846
Enclosure to U LNRC-06754 Page 12 o124 c) The PAVAN-NAI input and output files of Enclosures I 2 and I 3 were used only for the purpose of calculating the atmospheric dispersion factors (X/Qs) for the Exclusion Area Boundary (EAB) and Low Population Zone (LPZ) for releases from the Reactor Building (RB) and Refueling Water Storage Tank (RWST).
The PAVAN-NAI input files intended to be submitted in Enclosure I 2 are as follows:
. clwAST_PAVAN_RB. inp
. clwAST_PAVAN_RWST.inp Likewise, the PAVAN-NAI output files intended to be submitted in Enclosure I 3 are as follows:
. clwAST_PAVAN_RB.out
. clwAST_PAVANRWST.out Any other PAVAN-NAI files were not intended to be transmitted and as such should not be considered as a part of the License Amendment Request or the December 1 2021 ,
supplemental submittal.
d) Callaway acknowledges the NRC staff recommendation to update the second entry of Card Type 3 of the PAVAN-NAI model input to be consistent with the implemented calculation of vertical temperature difference between the upper and lower measurement heights. Due to formal acknowledgement of the input read error identified in RAI-1 a, the PAVAN-NAI input files were not revised at this time.
RAI No. 2 (RAI-2):
Regulatory Requirement: see Regulatory Requirements for RAI No. 1
Background:
The Licensees onsite dispersion modeling analysis was based on the ARCON96-NAI code. This model was used to estimate XIQs at the normal and emergency air intakes of the control building, at various points along the path of ingress and egress to the control building, and at the air intake to the TSC. As with PAVAN-NAI, ARCON96-NAI appears to be essentially the same as the NRC-approved ARCON96 dispersion model. ARCON96 implements RG 1.194 and the associated users guidance in NUREGICR-6331. Enclosure 14 to the December 1, 2021, supplemental submittal discusses the differences between ARCON96-NAI and ARCON96. Only slight differences between the input to and output of the two codes were observed during the NRC staffs initial review. The staff notes that model appears to have been run at different times during 201 7 with the input I output files differing slightly after about July of that year although the same version number of the code (i.e. I I ) is designated for all runs.
According to Enclosure 14, Met data were input to ARCON96-NAI in the prescribed ARCON96 format. The 2013 to 2016 POR of onsite Met data is the same as that used for the PAVAN-NAI modeling analysis. However, the staff notes that the wind speed units of measure as input to ARCON96-NAI is in miles per hour (mph) whereas the hourly data reported in Enclosure 7 to the supplemental submittal is in units of m/sec consistent with Appendix A of RG 1.23.
Enclosure to ULNRC-06754 Pagel3of24 The Licensee provided ARCON96-NAI input and output files in Enclosures 9, 1 0, and I 1 of the supplemental submittal in response to Question 22c from the previously referenced June 14, 2018, and March 15, 2021, pre-application meetings with the Licensee. These enclosures included 78 model runs (one input and two output files per run) to evaluate potential accident releases from sources generally designated by Items 3 through 14 and Item 16 as shown on Figure 3.1 of Enclosure I to the December 1 2021 supplemental submittal. Modeled receptor locations were also generally identified on Figure 3.1 as Item 1 (consisting of emergency air intakes A and B and the midpoint between those two intakes), Item 2 (the normal air intake for the control room), and Item I 5 (the air intake for the TSC).
In response to Question 19 from the previously referenced June 14, 2018, and March 15, 2021, pre-application meetings with the Licensee, Table 3-25 of Enclosure I lists, in part, various characteristics of the release/receptor pairs input to the ARCON96-NAI model runs. These inputs identify the respective release and receptor points, the horizontal distance between these points, the release and intake heights (in meters) above plant grade, and the direction looking at a given source from a given receptor in degrees relative to True North.
Enclosures 9, 1 0, and I 1 also included 32 ARCON96-NAI model runs (again, one input and two output files per run) to evaluate various accident release scenarios from the reactor building vent and the RWST vent as potential sources. The control room operator access path was sketched on Figure 3.2 of Enclosure 1 Receptor locations are presumably at the turning points along this sketched path.
Figure 3.1 of Enclosure 1 indicates the offset between Plant North and True North (i.e., the former is oriented about I 33.56 degrees counterclockwise of the latter). Neither Figure 3. 1 nor Figure 3.2 of Enclosure I indicates a distance scale as called for by Question 1 7a from the previously referenced pre-application meetings with the Licensee.
Request:
a) The NRC staff tried to verify many of the distances between the numerous potential source and receptor pairs as well as the receptor-to-source directions of these pairs relative to True North using Table 3-25 and Figure 3.1 of Enclosure 1 to the supplementary submittal and other readily available information. In doing so, the staff exercised reasonable flexibility, given this information, by considering distances to be verified if they were within about +/- 5 meters and about +/- 5 degrees relative to True North of the values listed in Table 3-25.
The items listed in Figure 3.1 use phrases such as nearest point to receptor, closest
[source name], and closest [source name] nearest point to receptor. However, when evaluating a number of the same sources but impacting a different receptor, the distance and/or receptor-to-source direction would only meet the above acceptance criteria if the source and/or receptor were located in different positions (e.g., at some point on the item label itself, at the tip of the arrow associated with an item label, at some point on the edge of the building housing a potential source or receptor, or at some point within the perimeter of the building itself).
As a result, this portion of the ARCON96-NAI dispersion modeling review was not completed. Because these characteristics are direct inputs to the run files, Figure 3.1 in Enclosure 1 of the supplemental submittal should be clarified: (a) to include a distance
Enclosure to ULNRC-06754 Page 14 of 24 scale, and (b) show specific source and receptor locations that correspond to the various model runs. Due to the number of model-runs, more than one figure may be necessary to clearly illustrate all of these relationships. Any other figures, tables, and text affected by these clarifications should be revised as well.
b) Figure 3.2 in Enclosure I of the supplemental submittal should be: (a) clarified to include a distance scale, (b) ensure that its orientation, as reproduced in that submittal, is relative to Plant North, (c) identify the potential release points for the reactor building vent and RWST vent, and (d) indicate the receptor locations evaluated in the corresponding model runs (e.g., presumably at the turning points along the sketched path in Figure 3.2). As above, any other figures, tables, and text affected by these clarifications should be revised as well.
c) Clearly explain the purpose and use of the thirteen (1 3) ARCON96-NAI model runs provided in Enclosures 9, 1 0, and 1 1 of the supplemental submittal with receptor distances ranging between I 322.7 m and I 471 .7 m. This includes verifying: (a) what the distances entered in the input files are relative to (e.g., the EAB), (b) what directions relative to True North the respective distances correspond to understanding that the distances selected may not necessarily be associated with the directions having the most restrictive dispersion conditions (i.e., the highest X/Qs), (c) what potential source each run corresponds to (only a few appear to be missing), and (d) their relationship, if any, to the offsite model runs using PAVAN-NAI.
Ameren Response:
a) Excerpts of the plant area layout with the attached digital markup, drawing 8600-X-88100 are included below and the measured distances and angles between release and receptor locations. The drawing scale, highlighted in yellow, was used to determine all distances associated with the release/receptor pairings of the PAVAN and ARCON model runs. The release and receptor locations are indicated with color-coded alphanumeric values. Release points are given a strictly numerical value, while receptor locations are assigned one or more letters between a and c indicating the associated release point(s). Red alphanumeric values are applicable to the emergency Control Room intake receptor at minimum. Green alphanumeric values are applicable to the normal Control Room intake receptor only. Blue alphanumeric values are applicable to the Technical Support Center (TSC) receptor only.
Encfosure to U LNRC-06754 Page 15 of 24 1 E: 1 Th: 1 Fj :
!CLE 1 1O
- ScaIe applies to native digital drawing only.
LI 82 0
0
Enclosure to U LNRC-06754 Page 16 of 24
\ Red: apphcabte to ernetqeicy control room intake receptor, noted with a (or multiple recep rs
\
\
- reer: appIicabe to norma ccnttc room rt:ake teceDtor orty, noted wi:? b
\\
\\ Blue: applicable to technical support center receptor only, noted with c
\
[1] Emergency control room ntke 4, I [2] Nomial control room intake I [31 ent I [4] RWST ent I [5] Fuel handhncj building (nearest point to receptori I [6] Closest ADf I [71 Closest M5SV
[1 Closest Main Steam Line neate point to receptor) -
[9] CIoset feedwater Line inearest point to recepor
[10] Containment Maintenance Hatch
[1 1) Steam Jet Air Ejector nearet point to receptor
[12] Condenser fneare pointto receptor)
[13.] Turtne Driven AFW Exhaust Vents
[14] Reactor Building Waif (nearest point to ret or
[lSJTechnicaI SupportCenter
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Enclosure to ULNRC-06754 Page 17 of 24 b) Excerpts of the plant area layout, drawing 8600-X-881 00 are included below. The drawing scale, highlighted in yellow, and compass were used to determine all distances and angles associated with the release/receptor pairings of the ARCON96 model runs.
The path taken by the operator during CR ingress/egress is depicted with a red line from the parking lot to the Control Building. Turning points in the operators path (labeled with yellow boxes) were used to divide the trip into seven segments (labeled with blue boxes). The length of each segment was scaled from the drawing. The determined measurement of each segment is indicated with two straight blue lines, a set of blue arrows to indicate the direction of the measurement and the length in black text. The measured length of each segment was conservatively rounded up to the next nearest foot. In general, these distances closely matched the result from the root-mean-square of the plant N-S and plant E-W distances; however, to ensure conservatism, the horizontal distance was reduced by 5% for use in ARCON96. The location of analyzed Point 4 is actually at the closest point to containment along Segment 4 for conservatism, as indicated. This point is referred to as Access Point 4 in the License Amendment Request for simplicity.
Segment 1 of the defined path was excluded from the transit dose calculation as operators are expected to park as close to the site entry near Point 3 as possible; however, the segment was included for informational purposes. Segment 2 was retained in full length as a conservative adder to the access dose over and above the projected path operators are expected to take.
The release locations are indicated by green text boxes at the Unit Vent Stack and RWST Vent. A designated release location of the plant stack is applied for the expected diffuse containment leakage with respect to operators in transit at ground level. This release location is conservative as it predicts a higher concentration of radioactive isotopes along the operator path than a diffuse containment leakage model.
Enclosure to U LNRC-06754 Page 18 of 24 ii; Et; 1U:) 5:1 SC&LE: 1-. 1O
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Enclosure to U LNRC-06754 Page 19 of 24 c) The ARCON96 files intended to be submitted in Enclosures 9, 1 0, and 1 1 of the supplemental submitted are as follows.
Input Files Output Logs Output CFDs (Enclosure 9) (Enclosure 10) (Enclosure 11) clwA96_O1 .RSF clwA96_O1 Jog clwA96_O1 .CFD clwA96_02. RSF clwA96_02 log. clwA96_02. CFD clwA96_03. RSF clwA96_03. log clwA96_03. CFD clwA96_04. RSF clwA96_04. log clwA96_04. CFD clwA96_05.RSF clwA96_05.log clwA96_05.CFD clwA96_06. RSF clwA96_06. log clwA96_06. CFD clwA96_07. RSF clwA96_07. log clwA96_Of. CFD clwA96_08. RSF clwA96_08. log clwA96_08. CFD clwA96_09. RSF clwA96_09. log clwA96_09. CFD clwA96_1 0. RSF clwA96_1 0. log clwA96_1 0. CFD clwA96_1 1 .RSF clwA96_1 1 .log clwA96_1 1 .CFD clwA96_1 2. RSF clwA96_1 2. log clwA96_1 2.CFD clwA96_1 3. RSF clwA96_1 3. log clwA96_1 3. CFD clwA96_1 4. RSF clwA96_J 4. log clwA96_1 4. CFD clwA96_1 5. RSF clwA96_1 5.Iog clwA96_1 5.CFD clwA96_1 6. RSF clwA96_1 6. log clwA96_1 6 CFD.
clwA96_1 7.RSF clwA96_1 7.log clwA96_1 7.CFD clwA96_1 8. RSF clwA96_1 8. log clwA96_1 8.CFD clwA96_1 9. RSF clwA96_1 9.log clwA96_1 9.CFD clwA96_20. RSF clwA96_20. log clwA96_20. CFD clwA96_21 .RSF clwA96_21 .log clwA96_21 .CFD clwA96_22 RSF
. clwA96_22. log clwA96_22. CFD clwA96_23. RSF clwA96_23. log clwA96_23. CFD clwA96_24. RSF clwA96_24. log clwA96_24. CFD clwA96_25 RSF
. clwA96_25 log
. clwA96_25. CFD clwA96_26. RSF clwA96_26. log clwA96_26 CFD clwA96_27. RSF clwA96_27. log clwA96_27.CFD clwA9628. RSF clwA96_28. log clwA96_28. CFD clwA96_29. RSF clwA96_29. log clwA96_29. CFD clwA96_30. RSF clwA96_30 log
. clwA96_30. CFD clwA96_31 .RSF clwA96_31 .log clwA96_31 .CFD clwA96_32. RSF clwA96_32. log clwA96_32. CFD clwA96_33.RSF clwA96_33.log clwA96_33.CFD clwA96_34. RSF clwA96_34. log clwA96_34. CFD clwA9635. RSF clwA96_35. log clwA96_35. CFD clwA96_36. RSF clwA96_36. log clwA96_36. CFD clwA9637. RSF clwA96_37. log clwA96_37. CFD clwA96_39. RSF clwA96_39. log clwA96_39. CFD clwA96_40. RSF clwA96_40. log clwA96_40. CFD clwA96_42. RSF clwA96_42. log clwA96_42. CFD clwA96_44. RSF clwA96_44. log clwA96_44. CFD clwA9645. RSF clwA96_45. log clwA96_45. CFD clwA96_47. RSF clwA9647. log clwA96_47. CFD
Enclosure to ULNRC-06754 Page 20 of 24 Input Files Output Logs Output CFDs (Enclosure 9) (Enclosure 10) (Enclosure 11) clwA96_48. RSF clwA96_48. log clwA96_48. CFD clwA96_50. RSF clwA96_50. log clwA96_50. CFD clwA96_51 RSF clwA96_51 .log clwA96_51 .CFD clwA96_53. RSF clwA96_53. log clwA96_53. CFD clwA96_54. RSF clwA96_54. log clwA96_54. CFD clwA96_56 RSF . clwA96_56 log
. clwA96_56. CFD clwA96_57. RSF clwA96_57. log clwA965f. CFD clwA9659.RSF clwA96_59.log clwA96_59.CFD clwA96_60. RSF clwA96_60. log clwA96_60. CFD clwA96_62. RSF clwA96_62. log clwA96_62. CFD clwA96_63. RSF clwA96_63. log clwA96_63. CFD clwA96_65. RSF clwA96_65. log clwA96_65. CFD clwA96_66 RSF. clwA96_66. log clwA96_66. CFD clwA96_67. RSF clwA96_67. log clwA96_67. CFD clwA96_68. RSF clwA96_68. log clwA96_68. CFD clwA96_69.RSF clwA96_69.log clwA96_69.CFD clwA96_71 .RSF clwA96_71 Jog clwA96_71 .CFD clwA96_73. RSF clwA96_73. log clwA96_73. CFD clwA96_74. RSF clwA96_74. log clwA96_74. CFD clwA96_75. RSF clwA96_75. log clwA96_75. CFD clwA96_76 RSF
. clwA96_76. log clwA96_76 CFD clwA96_77. RSF clwA96_77. log clwA96fZ. CFD rwst_mpl.RSF rwst_mpl.log rwst_mpl.CFD rwst_mp2. RSF rwstmp2.log rwst_mp2.CFD rwst_mp3. RSF rwst_mp3.log rwst_mp3.CFD rwstmp4. RSF rwst_mp4.log rwst_mp4.CFD rwst_mp4p5. RSF rwst_mp4p5.log rwst_mp4p5. CFD rwst_mp5.RSF rwst_mp5.log rwst_mp5.CFD rwst_mp6. RSF rwst_mp6.log rwst_mp6. CFD rwst_mp7. RSF rwst_mp7.log rwst_mp7.CFD vent_mpl.RSF vent_mpl.log vent_mpl.CFD vent_mp 1 RSF vent_mpl_Oheight. log vent_mp 1 CFD vent_mp2.RSF vent_mp2.log vent_mp2.CFD vent_mp2_Oheight. RSF vent_mp2_Oheight.log vent_mp2_Oheight. CFD vent_rn p3. RSF vent_rnp3. log vent_mp3. CFD ventrn p3_Oheight. RSF vent_rnp3_Oheight.log vent_mp3_Oheight. CFD ventrnp4. RSF vent_rnp4. log vent_mp4. CFD vent_mp4_Oheight. RSF vent_rnp4_Oheightiog vent_mp4_Oheight. CFD vent_rnp4p5. RSF vent_rnp4p5.log vent_mp4p5. CFD vent_rnp4p5_Oheight. RSF vent_rnp4p5_Oheight. log vent_mp4p5_OheightCFD vent_rnp5.RSF vent_mp5iog vent_mp5CFD vent_mp5_Oheight. RSF vent_rnp5_Oheight. log vent_mp5_Oheight. CFD vent_rnp6.RSF vent_mp6.log vent_mp6.CFD vent_rnp6_Oheight. RSF vent_rnp6_Oheight. log vent_rnp6_Oheight. CFD vent_rnpf.RSF vent_mpf.log vent_rnp7.CFD vent_rnp7_Oheight. RSF vent_mpf_Oheight.log vent_mp7_Oheight. CFD
Enclosure to U LNRC-06754 Page2J of 24 Any other ARCON96 input, output log, or output CFD files were not intended to be transmitted and as such should not be considered as part of the License Amendment Request or the December 1 2021 supplemental submittal. None of the above referenced ARCON96 cases meet the criteria identified in RAI-2c.
Regulatory Requirement: 10 CFR Part 50.67(b) states, in part, that [a] licensee who seeks to revise its current accident source term in design basis radiological consequence analyses shall apply for a license amendment under § 50.90. The application shall contain an evaluation of the consequences of applicable design basis accidents previously analyzed in the safety analysis report.
NUREG-0800, Section 15.0.1, Radiological Consequence Analyses Using Alternative Source Terms, Rev. 0, assigns responsibility to the Operator Licensing and Human Factors Branch for the review issues related to emergency operating procedures and human factors engineering design. This section also states, in part, that an acceptable implementation of an alternative source term should demonstrate compliance with plant-specific licensing commitments made in response to the NUREG-0737, Clarification of TMI Action Plan Requirements. Specific provisions of interest within the context of this review plan section include lll.D.3.4, Control Room Habitability, as it relates to maintaining the control room in a safe, habitable condition under accident conditions by providing adequate protection against radiation and toxic gases.
Background:
In the license amendment request (LAR), Callaway does not appear to address the area of emergency operating procedures. In order to determine whether human factors considerations have been adequately accounted for, the NRC staff require a description of whether modifications to emergency operating procedures will occur as part of the LAR (for example: the incorporation of new or modified operator actions for maintaining control room habitability under accident conditions).
Request: Please describe whether Callaway will be modifying any emergency operating procedures as part of the LAR, and if so, describe the procedural changes, any changes in the time constraints associated with the performance of procedurally driven actions, and any operator training associated with those changes. If applicable, be sure to include a discussion of how the considerations like those in NUREG-0737 described above are addressed.
Ameren Response: Fuel Handling Accident in the reactor containment building Table 3-58 of ULNRC-06636 Enclosure I documents credit for operator action to initiate the Emergency Exhaust system within 1 0-minutes of accident initiation. Manual actuation of the Emergency Exhaust system is performed from the Control Room as directed by the current fuel handling accident response procedure, OTO-KE-00001 This action was previously implemented in the procedure although it has not been previously credited in Callaways radiological dose analysis of the Fuel Handling Accident. The I 0-minute requirement for completion of the action will be added to Callaways Significant Operator Response Timing program as a Time Critical Action (TCA) upon implementation of the AST License Amendment.
Inclusion as a TCA ensures that the action and action timing are trained on by the operators and periodically validated.
Enclosure to U LNRC-06754 Page 22 of 24 All other operator actions credited to mitigate a radiological dose event are consistent with the Analyses of Record for Callaway. No other changes to operator actions, timing requirements, or emergency operating procedures are required as part of AST implementation.
RAI No. 4 (EMIB-RAI-1):
Regulatory Requirement: RG I 1 83, Re-Analysis Guidance section identifies that the ability of the damper to close against increased containment pressure may need to be evaluated or the ability of ductwork downstream of the dampers to withstand increased stresses.
Background:
In Enclosure I Section 2.2.2 of the LAR, the licensee addresses Control Room Emergency Ventilation System (CREVS) Design and Operation. However, the following information was not discussed, and the licensee is requested to provide details.
Request: The licensee is requested to provide the following details:
a) Discuss whether the adoption of the Alternative Source Term (AST) affects any of the safety related piping.
b) Discuss whether any safety related Heating Ventilation and Air Conditioning (HVAC) system is credited in the AST adoption.
c) Discuss the seismic qualification of the control room safety related HVAC including ductwork, air handlers, damper systems, chillers, and supports.
Ameren Response:
a) Callaways adoption of the Alternative Source Term (AST) relies on the seismic qualification of the safety related piping connecting the containment recirculation sump to the Refueling Water Storage Tank (RWST) for consideration of RWST back-leakage in the event of a Loss of Coolant Accident (LOCA). In accordance with NRC Information Notice 2012-01, Seismic Considerations Principally Issues Involving Tanks, all flow paths above and below the normal water level of the RWST are:
. Designed, installed, maintained, and qualified to seismic Category I criteria in accordance with the ASME B&PV Code Section Ill Class 2 and
. Isolated from non-seismic category I piping by redundant automatic isolation valves which close on a safety injection signal and fail closed on loss of power, or
. Isolated from non-seismic category I piping by a locked closed isolation valve.
Therefore, reliance on this safety-related piping and isolation capability for AST adoption is acceptable based on the design.
Enclosure to U LNRC-06754 Page23 of 24 b) As part of adopting the AST at Callaway Energy Center, credit is taken for certain safety-related Heating Ventilation and Air Conditioning (HVAC) systems in two of the radiological dose analyses, in accordance with the guidance of Regulatory Guide 1.183.
During a Loss of Coolant Accident (LOCA), the Auxiliary Building (AB) emergency exhaust filtration is credited for the ECCS leakage case during recirculation.
Additionally, modeling for isolation of the Containment mini-purge system is built on the assumption of prompt isolation at I I seconds, which includes the valve stroke times, generation of safety injection signal, and signal delay time. While the mini-purge flow leaving containment is filtered, this filtration is not included in the Engineered Safety Feature portion of the system and so was not credited in the AST dose analysis.
During a Fuel Handling Accident (FHA) in the Fuel Handling Building (FHB), Emergency Exhaust from the FHB is credited without filtration. Technical Specification Table 3.3.7-1 shows that the radiation monitors at the control room air intakes are not required to be operable during movement of irradiated fuel assemblies in the fuel building. Instead, Technical Specification 3.3.7 and 3.3.8 show that High Gaseous Fuel Building Exhaust Radiation channels GG-RE-27 and GG-RE-28 actuate both the Emergency Exhaust System (EES) and control room isolation.
Although Regulatory Guide I I 83 does not provide guidance with regard to the Technical Support Center (TSC) HVAC, safety-grade filtration of outside makeup air and recirculated air is credited during emergency mode operation in the AST dose analyses.
As documented in Item 3 of the Conformance with RIS 2006-04 Table, Attachment D of Enclosure I of the LAR, for events where safety related HVAC is not credited:
Actuation of emergency control room HVAC mode is not credited for certain accidents. Therefore, events which do not result in a safety injection signal or do not reach a radiation monitor setpoint are assumed to stay in normal control room HVAC mode. The normal ventilation system does not credit filtration and has greater flow rate than the ESF ventilation. Therefore, the resulting doses to personnel within the control room will be greater if it is assumed that the ESF ventilation system is not actuated at the event initiation due to a loss of offsite power. Acceptable control room doses have been calculated with a maximum unfiltered inleakage of 6000 cfm to the control building, 60 cfm to the control room, and 300 cfm to the equipment room.
c) The Control Room Emergency Ventilation System (CREVS) is comprised of the following components, in addition to the supporting piping, electrical supply, instrumentation, ductwork and dampers. Each of these components is designed to seismic Category I criteria (Reg Guide I .29) and qualified either by test, analysis, or a combination thereof. All the power supplies and control functions necessary for safe functioning of the control room air-conditioning system are Class IE and designed, installed and qualified to Seismic Category I criteria.
Enclosure to ULNRC-06754 Page 24 of 24 Control Room Filter Adsorber Units (FGKOIAIB): The items procured under specification M-621 were qualified by analysis and test. Specifically, the filter adsorber units themselves were qualified by finite element analysis with discrete components qualified by test in accordance with IEEE 344-1975.
(Ref. Specification M-621)
Control Room Pressurization Filter Adsorber Units (FGKO2A1B): Like FG KOl NB, the items procured under specification M-621 were qualified by analysis and test.
Specifically, the filter adsorber units themselves were qualified by finite element analysis with discrete components qualified by test in accordance with IEEE 344-1975.
(Ref. Specification M-621)
Control Room Air Conditioning (A/C) Units (SGKO4AIB): These units were qualified by test in accordance with IEEE 344-1975.
(Ref. Specification M-622. I)
Control Room Filtration Fans (CGKO3AIB): These units were qualified by analysis, test and combinations. Specifically, the fans were qualified by analysis in accordance with IEEE 344-1975, and the motors were qualified separately by analysis/test in accordance with IEEE 323-1974/IEEE 344-1975.
(Ref. Specification M-622.1, E-013)
Control Room Pressurization Fans (CGKO4AIB): Like the Control Room Filtration Fans, these units were qualified by analysis, test and combinations. Specifically, the fans were qualified by analysis in accordance with IEEE 344-1975, and the motors were qualified separately by analysis/test in accordance with IEEE 323-1974/IEEE 344-1975.
(Ref. Specification M-622. I E-O1 3)
Isolation Dampers are categorized as safety related seismic Category I components and qualified in accordance with IEEE 344-1 975 by a combination of test and analysis.
(Ref. Specification M-627NB)
Aside from these components, pressure piping servicing these equipment items was designed, analyzed, and installed in accordance with the ASME B&PV Code,Section III, Subsection 3, including the pipe supports. Also, ductwork was designed, analyzed and installed as safety related, seismic Category I items and supported based on ASME/ANSI standards for HVAC systems following the guidance of USNRC Regulatory Guide 1.52.