ML040980030
| ML040980030 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 03/30/2004 |
| From: | Hartz L Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 03-464B | |
| Download: ML040980030 (10) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RIcIIlMOND, VIRGINIA 23261 March 30, 2004 U.S. Nuclear Regulatory Commission Serial No. 03-464B Attention: Document Control Desk NL&OS/ETS R1 Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATION CHANGES IMPLEMENTATION OF ALTERNATE SOURCE TERM REQUEST FOR ADDITIONAL INFORMATION CONTAINMENT SPRAY SYSTEMS IODINE REMOVAL In a letter dated September 12, 2003 (Serial No.03-464), Virginia Electric and Power Company (Dominion) requested amendments, in the form of changes to the Technical Specifications to Facility Operating Licenses Numbers NPF-4 and NPF-7 for North Anna Power Station Units 1 and 2, respectively. The proposed changes were requested based on the radiological dose analysis margins obtained by using an alternate source term consistent with 10 CFR 50.67. In a February 25, 2004 facsimile, the NRC staff requested additional information regarding containment spray iodine removal coefficients used for loss of coolant accidents, emergency planning, and radiological training. The requested information regarding containment spray iodine removal coefficients during loss of coolant accidents is provided in the attachment to this letter.
The remaining information requested regarding emergency planning and radiological training will be submitted in a subsequent letter.
If you have any further questions or require additional information, please contact Mr.
Thomas Shaub at (804) 273-2763.
Very truly yours, Leslie N. Hartz Vice President - Nuclear Engineering Attachment Commitments made in this letter: None
.0
SN: 03-464B Docket Nos.: 50-338/339 Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. J. E. Reasor, Jr. (without attachment)
Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060 Commissioner (without attachment)
Bureau of Radiological Health 1500 East Main Street Suite 240 Richmond, Virginia 23218 Mr. M. T. Widmann (without attachment)
NRC Senior Resident Inspector North Anna Power Station Mr. S. R. Monarque NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8-H12 Rockville, Maryland 20852
SN: 03-464B Docket Nos.: 50-338/339
Subject:
RAI - Proposed TS Changes Implementation of AST Containment Spray Systems Iodine Removal COMMONWEALTH OF VIRGINIA )
COUNTY OF HENRICO )
The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Leslie N. Hartz, who is Vice President - Nuclear Engineering, of Virginia Electric and Power Company. She has affirmed before me that she is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of her knowledge and belief.
Acknowledged before me this 30t' day of March, 2004.
My Commission Expires: March 31, 2008.
/\Notary Public
_ . _ ,.v 4r - (;SEAL)
Attachment Virginia Electric and Power Company North Anna Power Station Units 1 and 2 Proposed Technical Specification Changes Implementation of Alternate Source Term Request for Additional Information Containment Sprays Iodine Removal North Anna Power Station Units 1 and 2 Virginia Electric and Power Company (Dominion)
SN: 03-464B Docket Nos.: 50-338/339 NORTH ANNA ALTERNATIVE SOURCE TERM In a letter dated September 12, 2003 (Serial No.03-464), Virginia Electric and Power Company (Dominion) requested amendments, in the form of changes to the Technical Specifications to Facility Operating Licenses Numbers NPF-4 and NPF-7 for North Anna Power Station Units 1 and 2, respectively. The proposed changes were requested based on the radiological dose analysis margins obtained by using an alternate source term consistent with 10 CFR 50.67. In a February 25, 2004 facsimile, the NRC staff requested additional information regarding containment spray iodine removal coefficients used for loss of coolant accidents, emergency planning, and radiological training. The requested information regarding containment spray iodine removal coefficients during loss of coolant accidents is provided below.
NRC Question 1 The NRC Staff review includes calculations of spray removal coefficients (x) using the methodology in Standard Review Plan (SRP) 6.5.2. These formulas are based on mass-mean diameter of the spray drops. The Updated Final Safety Analysis Report (Revision 38, page 6.2.82) provides volume-median diameter of the spray drops for each system. Please provide mass-mean diameter values for droplets from the quench and recirculation spray nozzles, or the methodology used to convert from the volume-median values.
Dominion Response:
There are three types of nozzles used in the North Anna quench spray (QS) and recirculation spray (RS) systems. The arrangement of the North Anna quench and recirculation spray headers is discussed in the response to Question No. 2. Based on the equations in SRP 6.5.2 a larger diameter droplet results in a lower spray lambda.
The largest mass-mean diameter values for droplets from the quench and recirculation spray nozzles that bound the combinations of nozzles and headers are 829 microns and 924 microns, respectively.
NRC Question 2 The license amendment proposal (page 27) states that containment spray removal rates for aerosol fission products were calculated using the methodology of NUREG/CE-5966.
One of the parameters in this methodology is water flux (Q). Please provide the water flux values used to calculate the aerosol iodine removal coefficients, and explain how these water flux values were determined.
Dominion Response:
The spray water flux is calculated by dividing the spray flow rate by the cross-sectional area of the sprayed portion of the containment. Since the removal rate is dependent on drop height and spray rate, the spray headers have different removal rates.
Each train of the Quench Spray System and each train of the Recirculation Spray System is redundant. One quench spray header is at the 392'10" elevation and the Page 1 of 6
SN: 03-464B Docket Nos.: 50-338/339 other is at the 393'2" elevation. Two semi-circular recirculation spray headers fed by the inside recirculation spray pumps are located at 377'10" elevation and another set of semi-circular recirculation spray headers fed by the outside recirculation spray pumps are located at the 376'10" elevation. For the LOCA analysis only one train of the containment spray and one train of the inside recirculation and one train of the outside recirculation were modeled as operating.
The start times of the spray flows and the flow rates vary with time for each of the spray systems. Table 2 below gives the start times and flow rates used as input for the LOCA dose analysis. The quench spray system stops flowing at 5610 seconds from the onset of the accident. Also included in Table 2 are the elevations of the headers.
Table 2 Spray System Characteristics Inside Recirculation Spray headers: Outside Recirculation Spray Headers:
Elevation - 377'-1 0" Elevation - 376'-1 0" 3100 gpm (288.5 sec - 30 days) 3450 gpm (478.5 sec - 30 days)
Quench Spray Dome headers:
Elevation - 391'-1 0" & 393'-2" For quench spray flows see Table 3 below.
The quench spray headers are modeled at the elevation of the lower quench spray header or 391'10". The 4 recirculation spray headers are modeled at the average elevation of recirculation spray headers or 377'4".
The drop height for each spray system is calculated relative to the elevation of the containment operations deck (291'10") as follows:
Has = (391 '10") - (291'10") = 100 ft HRS = (377'4") - (291'10") = 85.5 ft Page 2 of 6
SN: 03-464B Docket Nos.: 50-338/339 Table 3 contains the flow rates as a function of time for the quench spray headers.
Table 3 Quench Spray Flow Time QS Flow (sec.) (gP) 0 0 90 1531.7 210 1567.29 300 1573.62 390 1588.78 510 1607.57 600 1631.56 690 1651.22 810 1672.63 900 1685.61 990 1696.18 1110 1706.81 1200 1712.41 1290 1725.91 1410 1745.92 1500 1757.23 1590 1765.88 1710 1774.36 1800 1779.52 1890 1783.45 2010 1786.94 2100 1788.29 2190 1788.6 2310 1787 2400 1785.62 2490 1783.08 2610 1778.83 2700 1775.11 3000 1760.3 3300 1743.65 3600 1726.18 3900 1719.28 4200 1714.69 4500 1710.06 4800 1705.39 5100 1700.43 5400 1695.31 5610 1691.69 The inner radius of the containment is 63' and has a cross sectional area of 1.25E4 ft2.
Only 70% of the containment volume is being credited in this calculation as being covered by the combined quench and recirculation spray systems. Therefore, the water flux was based on 70% of the cross sectional area of the containment (8.73E3 ft2).
The water fluxes corresponding to these flows were calculated as follows:
Q = (water flow gal/min)(0.13368 ft3 /gal)/(8.73E3 ft2) = water flux in units ft/min The 10th percentile equations from NUREG/CR-5966 were evaluated using a fall height of 100 ft. to calculate the quench spray removal rates. The water flux values were computed using the equation above and are displayed in Table 4 under column heading "Q". The last two columns in Table 4 indicate the time period evaluated.
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SN: 03-464B Docket Nos.: 50-338/339 Table 4 - Quench Spray Aerosol Lambda's Aerosol Sprav Removal Constant (10th Percentile)
- H REMOVAL CONSTANT (hr') TIME hr)
Mt DF (cm/sec) (cm) Xmf=.g Xmf/Xmf=.9 Xmf From To 9.00E-01 1.11E+00 1.1917E-02 3048 3.73E+00 1.OOE+00 3.7267E+00 2.50E-02 5.83E-02 9.00-E01 1.11E+00 1.2194E-02 3048 3.80E+00 1.OOE+00 3.8014E+00 5.83E-02 8.33E-02 9.00-E01 1.11E+00 1.2243E-02 3048 3.81E+00 1.OOE+00 3.8147E+00 8.33E-02 1.08E-01 9.00-E01 1.11E+00 1.2361 E-02 3048 3.85E+00 1.OOE+00 3.8464E+00 1.08E-01 1.42E-01 9.00-E01 1.11E+00 1.2507E-02 3048 3.89E+00 1.OOE+00 3.8856E+00 1.42E-01 1.67E-01 9.00E-01 1.11 E+00 1.2694E-02 3048 3.94E+00 1.OOE+00 3.9355E+00 1.67E-01 1.92E-01 9.00E-01 1.11E+00 1.2847E-02 3048 3.98E+00 1.OOE+00 3.9763E+00 1.92E-01 2.25E-01 9.00E-01 1.11E+00 1.3013E-02 3048 4.02E+00 1.OOE+00 4.0206E+00 2.25E-01 2.50E-01 9.002E01 1.11 E+00 1.3114E-02 3048 4.05E+00 1.OOE+00 4.0474E+00 2.50E-01 2.75E-01 9.00E-01 1.11 E+00 1.3197E-02 3048 4.07E+00 1.OOE+00 4.0691 E+00 2.75E-01 3.08E-01 9.002E01 1.11E+00 1.3279E-02 3048 4.09E+00 1.OOE+00 4.091OE+00 3.08E-01 3.33E-01 9.00E-01 1.11E+00 1.3323E-02 3048 4.1 OE+00 1.OOE+00 4.1025E+00 3.33E-01 3.58E-01 9.00E-01 1.11E+00 1.3428E-02 3048 4.13E+00 1.OOE+00 4.1302E+00 3.58E-01 3.92E-01 9.00E-01 1.11 E+00 1.3584E-02 3048 4.17E+00 1.OOE+00 4.1711E+00 3.92E-01 4.17E-01 9.00-E01 1.11 E+00 1.3672E-02 3048 4.19E+00 1.OOE+00 4.1942E+00 4.17E-01 4.42E-01 9.OOE-01 1.11 E+00 1.3739E-02 3048 4.21 E+00 1.OOE+00 4.2119E+00 4.42E-01 4.75E-01 9.00E-01 1.11 E+00 1.3805E-02 3048 4.23E+00 1.OOE+00 4.2292E+00 4.75E-01 5.002E01 9.00E-01 1.11E+00 1.3845E-02 3048 4.24E+00 1.OOE+00 4.2397E+00 5.OOE-01 5.25E-01 9.OOE-01 1.11 E+00 1.3876E-02 3048 4.25E+00 1.OOE+00 4.2476E+00 5.25E-01 5.58E-01 9.00-E01 1.11E+00 1.3903E-02 3048 4.25E+00 1.OOE+00 4.2547E+00 5.58E-01 5.83E-01 9.00-E01 1.11E+00 1.3913E-02 3048 4.26E+00 1.OOE+00 4.2575E+00 5.83E-01 6.08E-01 9.00E-01 1.11E+00 1.3916E-02 3048 4.26E+00 1.OOE+00 4.2581E+00 6.08E-01 6.42E-01 9.OOE-01 1.11E+00 1.3903E-02 3048 4.25E+00 1.OOE+00 4.2549E+00 6.42E-01 6.67E-01 9.00-E01 1.11E+00 1.3893E-02 3048 4.25E+00 1.OOE+00 4.2521 E+00 6.67E-01 6.92E-01 9.00-E01 1.11E+00 1.3873E-02 3048 4.25E+00 1.OOE+00 4.2469E+00 6.92E-01 7.25E-01 9.00-E01 1.11E+00 1.3840E-02 3048 4.24E+00 1.OOE+00 4.2382E+00 7.25E-01 7.50E-01 9.00-E01 1.11 E+00 1.3811 E-02 3048 4.23E+00 1.OOE+00 4.2307E+00 7.50E-01 8.33E-01 9.00-E01 1.11E+00 1.3696E-02 3048 4.20E+00 1.OOE+00 4.2005E+00 8.33E-01 9.17E-01 9.00-E01 1.11E+00 1.3566E-02 3048 4.17E+00 1.OOE+00 4.1665E+00 9.17E-01 1.OOE+00 9.OOE-01 1.11 E+00 1.3430E-02 3048 4.13E+00 1.OOE+00 4.1307E+00 1.OOE+00 1.08E+00 9.OOE-01 1.11E+00 1.3376E-02 3048 4.12E+00 1.OOE+00 4.1166E+00 1.08E+00 1.17E+00 9.00-E01 1.11E+00 1.3341 E-02 3048 4.11E+00 1.OOE+00 4.1072E+00 1.17E+00 1.25E+00 9.00E-01 1.11 E+00 1.3305E-02 3048 4.1OE+00 1.OOE+00 4.0977E+00 1.25E+00 1.33E+00 9.00-E01 1.11 E+00 1.3268E-02 3048 4.09E+00 1.OOE+00 4.0881 E+00 1.33E+00 1.42E+00 9.00E-01 1.11 E+00 1.3230E-02 3048 4.08E+00 1.OOE+00 4.0779E+00 1.42E+00 1.50E+00 9.00E-01 1.11 E+00 1.3190E-02 3048 4.07E+00 1.OOE+00 4.0673E+00 1.50E+00 1.56E+00 9.00E-01 1.11E+00 O.OOE+00 3048 O.OOE+00 O.OOE+00 O.OOOOE+00 1.56E+00 7.20E+02 4.1 437E+00 Average for 1.42E-01 hr to 1.56E+00 hr Page 4 of 6
SN: 03-464B Docket Nos.: 50-338/339 Table 5 shows the recirculation spray lambda values calculated using NUREG/CR-5966 10th percentile equations. The flows and timing are given in Table 2. The water flows of the inside and outside recirculation sprays were summed after the first time step.
The water flux values were calculated for the recirculation sprays with the same technique used for the quench sprays.
Table 5 - Recirculation Spray Aerosol Lambda's Aerosol SprayRemoval Constant (10th Percentile) 0 H REMOVAL CONSTANT (hr 1 ) TIME (hr) mf DF (cm/sec) (cm) xmf=.g Xmft/Xmf=.9 Xmf From To 9.OOE-01 1.11E+00 2.412E-02 2.6061E+03 6.9844E+00 1.OOOOE+00 6.9844E+00 8.01E-02 1.33E-01 9.OOE-01 1.11E+00 5.096E-02 2.6061E+03 1.2528E+01 1.OOOOE+00 1.2528E+01 1.33E-01 1.80E+OO 5.00E-01 2.OOE+00 5.096E-02 2.6061E+03 1.2528E+01 6.3747E-01 7.9863E+00 1.80E+00 1.87E+OO 3.OOE-01 3.33E+00 5.096E-02 2.6061E+03 1.2528E+01 4.4525E-01 5.5782E+00 1.87E+00 1.97E+OO 1.OOE-01 1.OOE+01 5.096E-02 2.6061E+03 1.2528E+01 2.3761E-01 2.9768E+00 1.97E+00 2.33E+OO 1.OOE-02 1.OOE+02 5.096E-02 2.6061E+03 1.2528E+01 1.2923E-01 1.6191E+00 2.33E+00 3.76E+OO 1.OOE-03 1.OOE+03 5.096E-02 2.6061E+03 1.2528E+01 1.1542E-01 1.4460E+00 3.76E+oo 5.35E+OO 1.OOE-04 1.OOE+04 5.096E-02 2.6061E+03 1.2528E+01 1.1366E-01 1.4239E+00 5.35E+00 6.97E+OO 1.OOE-05 1.OOE+05 5.096E-02 2.6061E+03 1.2528E+01 1.1343E-01 1.4211E+00 6.97E+00 8.59E+OO 1.OOE-99 1.OOE+99 5.096E-02 2.6061E+03 1.2528E+01 1.1340E-01 1.4207E+00 8.59E+00 1.61E+02 NRC Question 3 Please explain the basis for the time intervals used in the determination of spray removal coefficients for particulate iodine (Table 3.1.5, page 28 of the submittal). Time is not an explicit variable in the NUREG/CR-5966 or SRP 6.5.2 methodologies for evaluation iodine spray removal.
Dominion Response:
The time intervals used in the determination of spray removal coefficients for particulate iodine were based on the start and stop times of spray header flows, the end of the early in-vessel release phase, and the RADTRAD limitation of ten user defined time intervals. Table 6 below is Table 3.1-5 in the submittal.
The first time steps were based on the start times of spray flows from the quench spray headers and the recirculation spray headers. For example, the first time interval from 0.025 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> to 0.0801 hours0.00927 days <br />0.223 hours <br />0.00132 weeks <br />3.047805e-4 months <br /> is the interval from the start of the quench spray flow to the start of the inside recirculation spray flow. The second time interval from 0.0801 hours0.00927 days <br />0.223 hours <br />0.00132 weeks <br />3.047805e-4 months <br /> to 0.133 hours0.00154 days <br />0.0369 hours <br />2.199074e-4 weeks <br />5.06065e-5 months <br /> is the time from the start of the inside recirculation spray flow to the start of the outside recirculation spray flow. The third time interval is from the start of the outside recirculation spray flow to the termination of the quench spray flow. The fourth time interval is from the termination of the quench spray flow to the end of the early in-vessel phase of the release from the core.
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. I . .
SN: 03-464B Docket Nos.: 50-338/339 Table 6 - Combined Quench and Recirculation Spray Aerosol Lambda's Aerosol S ray Removal Const ant (10th Percentile)
Time (hr) Xmf From To (hr-1) 2.50E-02 8.01 E-02 3.7267E+00 8.01 E-02 1.33E-01 1.0799E+01 1.33E-01 1.56E+00 1.6672E+01 1.56E+00 1.80E+00 1.2528E+01 1.80E+00 1.87E+00 7.9863E+00 1.87E+00 1.97E+00 5.5782E+00 1.97E+00 2.33E+00 2.9768E+00 2.33E+00 3.76E+00 1.6191 E+00 3.76E+00 5.35E+00 1.4460E+00 5.35E+00 6.97E+00 1.4239E+00 6.97E+00 8.59E+00 1.4211 E+00 8.59E+00 1.61 E+02 1.4207E+00 After the early in-vessel release phase, the removal rate is adjusted stepwise by varying the mass fraction. The duration of time, t, required to change from a mass fraction mfo to mfl is determined using the following formula:
rrh = mnoe-xt t = In(mMdnM 1)/A For example, it is seen in Table 5 that it takes 0.07 hr (1.80 to 1.87 hr) to reduce the iodine mass fraction from 0.9 to 0.5. During this time step, the removal rate is assumed to be constant at 7.9863 hW1 . This time step and the subsequent time steps were selected to optimize the modeling accuracy of the sprays with only ten time steps. The limit of ten time steps is imposed by RADTRAD which allows ten user defined spray lambda's and corresponding time steps.
The removal rates or lambda's for the quench sprays and recirculation sprays in Table 6 are combined from Tables 4 and 5 above to yield effective removal rates for all the sprays.
For the first time step which starts at 2.5E-2 hours and ends at 8.01 E-2 hours, there is no recirculation spray water flow. So the combined lambda for this time step is based only on the quench sprays. The average of the quench spray lambda's for the 2.50E-2 hours and 5.83E-2 hours quench spray time steps was used. For the second time step, which starts at 0.801 E-2 hours and ends at 1.33E-1 hours, the recirculation spray lambda value for the 8.01 E-2 hour time step was added to the quench spray lambda value that was the average of the 8.33E-2 and 1.08E-1 hours time steps. For the quench spray time steps from 1.42E-1 hours to the termination of quench spray flow at 1.56 hours6.481481e-4 days <br />0.0156 hours <br />9.259259e-5 weeks <br />2.1308e-5 months <br /> the average quench spray lambda was used. This average quench spray lambda for 1.42E-1 to 1.56 hours6.481481e-4 days <br />0.0156 hours <br />9.259259e-5 weeks <br />2.1308e-5 months <br /> was 4.1437 hr-1. This was added to the recirculation spray lambda for the recirculation time steps 1.33E-1 to 1.80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. All subsequent time steps used only the recirculation spray lambda values.
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