ML13165A321
| ML13165A321 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 06/12/2013 |
| From: | Capps S Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC ME9716, TAC ME9717 | |
| Download: ML13165A321 (11) | |
Text
Steven D. Capps DUKE Vice President ENERGY° McGuire Nuclear Station Duke Energy MGO1VP 1 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4805 f: 980.875.4809 Steven.Ca pps@d uke-energy.com June 12, 2013 10 CFR 50.90 U.S. Nuclear Regulatory Commission Washington, DC 20555-001 ATTENTION: Document Control Desk
Subject:
Duke Energy Carolinas, LLC McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 License Amendment Request for Submittal of Atmospheric Relative Concentration Values for use in Control Room Envelope Radiological Dose Analysis dated September 25, 2012 (TAC Nos. ME9716 and ME9717)
Response to Request for Additional Information Related to the License Amendment Request (LAR)
This letter provides the responses to the request for additional information (RAI) regarding the referenced LAR dated September 25, 2012 (ADAMS No. ML1227A343). The request was conveyed by the NRC staff from James Kim by letter dated May 6, 2013. The NRC staff s questions and Duke Energy's responses are provided in Attachment 1.
The conclusions reached in the original determination that the LAR contains No Significant Hazards Considerations and the basis for the categorical exclusion from performing an Environmental/Impact Statement have not changed as a result of this request for additional information. This letter contains no regulatory commitments.
Please direct any questions you may have in this matter to Lee A. Hentz at (980) 875-4187.
Sincerely, Steven D. Capps Attachment www.duke-energy ccy
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US Nuclear Regulatory Commission June 12, 2013 Page 2 cc w/
Attachment:
V. M. McCree Regional Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 J. Zeiler NRC Senior Resident Inspector McGuire Nuclear Station J. S. Kim (addressee only)
Project Manager (McGuire)
U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 C2 Rockville, MD 20852-2738 W. L. Cox Ill, Section Chief North Carolina Department of Environment and Natural Resources Division of Environmental Health Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1645
US Nuclear Regulatory Commission June 12, 2013 Page 3 Steven D. Capps affirms that he is the person who subscribed his name to the foregoing statement, and that all the matters and facts set forth herein are true and correct to the best of his knowledge.
Steven D.Capps, ice President, McGuire Nuclear Station Subscribed and sworn to me:
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Date CNotary Public My commission expires: (Th]/, //i/1Q I Date
ATTACHMENT I REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING LICENSE AMENDMENT REQUEST RELATED TO ATMOSPHERIC RELATIVE CONCENTRATION VALUES FOR USE IN CONTROL ROOM ENVELOPE RADIOLOGICAL DOSE ANALYSIS MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 By application dated September 25, 2012 (Agency wide Documents Access and Management System (ADAMS) Accession Number ML12272A343), Duke Energy submitted a license amendment request (LAR) for the McGuire Nuclear Station, Units 1 and 2 (McGuire). The proposed LAR provides selected atmospheric relative concentration (x/Q) values for use in control room radiological dose analysis. These proposed x/Q values would replace those that were withdrawn during McGuire's request for full scope implementation of the alternate source term. The following request for additional information concerns information provided in Attachments 1 and 2 of the September 25,2012, LAR.
- 1. Table 1 of Attachment 1 provides inputs for 12 sets of control room x/Q values generated using the ARCON96 computer code. Tables 2 and 3 selectively list three sets of x/Q values each. Text adjacent to each table notes that the reported x/Q values reflect the maximum values from either Unit 1 or Unit 2, but does not explicitly name the unit associated with each set of x/Q values. U. S. Nuclear Regulatory Commission (NRC) staff has experienced some difficulty in understanding several of the x/Q sets provided in Tables 2 and 3 using the inputs in Table 1.
Therefore, please provide the following information:
a) For each set of x/Q values in Tables 2 and 3, please identify the unit from which the release is assumed to occur.
Duke Energy Response As noted in the LAR of September 25, 2012 (Sections 3.1.3 & 3.2), "The dispersion factors reported in these tables [Tables 2 & 3] reflect the maximum values from either Unit 1 or Unit 2."
The release location and transport path for each set of control room x/Q values listed in Tables 2 and 3 are given as follows:
The set of control room x/Q values in the second column in Table 2 (Same Unit Inboard x/Q) corresponds to release from a Unit 1 inboard main steam line and transport to the Unit 1 control room intake.
The control room x/Q values in the third column in Table 2 (Cross Unit Inboard x/Q) corresponds to release from a Unit 1 inboard main steam line and transport to the Unit 2 control room intake.
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The control room x/Q values in the fourth column in Table 2 (Same Unit Outboard x/Q) corresponds to release from a Unit 1 outboard main steam line and transport to the Unit 1 control room intake.
The set of control room x/Q values in the second column in Table 3 (Same Unit Inboard Doghouse x/Q) corresponds to release from the Unit 1 inboard Doghouse and transport to the Unit 1 control room intake.
The control room x/Q values in the third column in Table 3 (Same Unit Outboard Doghouse x/Q) corresponds to a release from the Unit 2 outboard Doghouse and transport to the Unit 2 control room intake.
The control room x/Q values in the fourth column in Table 3 (Cross Unit Outboard Doghouse x/Q) corresponds to a release from the Unit 1 outboard Doghouse and transport to the Unit 2 control room intake. Here, it is noted that for the calculations of the Cross Unit Outboard Doghouse x/Q, the Doghouse openings were modeled as points, (see the response to Question 1.b).
b) Verify that the input values provided in Table 1 are those used to generate each set of x/Q values in Tables 2 and 3.
Duke Energy Response The inputs used to calculate each of the control room x/Q values listed in Tables 2 and 3 are as follows:
The input for the control room x/Q values listed in the second column of Table 2 (Same Unit Inboard x/Q) and third column of Table 2 (Cross Unit Inboard x/Q) are taken from the second column of Table 1 (MSLBy). Additional input were as follows: The source radius was set to 0 m, the release flow rate to 0 m3/sec, and the release vertical velocity to 0 m/sec.
The input for the control room x/Q values listed in the fourth column of Table 2 (Same Unit Outboard x/Q) are not listed in Table 1. The input is presented in the following Table:
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Table I.b-1: Inputs for the Calculation of the Control Room X/Q ("Same Unit Outboard x/Q")
Value Input Unit I Release to Unit1 Intake Unit 2 Release to Unit 2 Intake Release Height 5.8 m 5.8 m Sigma-Y 0 m 0 m Sigma-Z 0 m 0 m Horizontal Distance from Source to Receptor 9.5 m 9.5 m Receptor to Source Angle 2820 1020 Building Cross Section Area 0.01 m2 0.01 m 2 Source Radius 0 m 0 m Release Flow Rate 0 ms/sec 0 m3/sec Release Vertical Velocity 0 m/sec 0 m/sec The input for the control room X/Q values listed in the second column of Table 3 (Same Unit Inboard Doghouse x/Q) are taken from the third column of Table 1 (DOGi"). In the calculation of these control room x/Qs, the source radius was set to 0 m, the release flow rate to 0 m3/sec, and the release vertical velocity to 0 m/sec.
The input for the control room X/Q values listed in the third column of Table 3 (Same Unit Outboard Doghouse x/Q) and the fourth column of Table 3 (Cross Unit Outboard Doghouse x/Q) are taken from the fourth column of Table 1 (DOGout). In the calculation of the Same Unit Outboard Doghouse x/Q, the "Sigma-y" was set to 1.48 m as shown in Table 1, as the openings are considered to be line sources. But for the calculation of the Cross Unit Outboard Doghouse x/Q, the "Sigma-y" was set to 0 m also as listed in Table 1; the Doghouse louvers are modeled as point sources only (see the response to Question 1.a). In the calculation of both of these control room x/Qs, the source radius was set to 0 m, the release flow rate to 0 m 3/sec, and the release vertical velocity to 0 m/sec.
c) In addition to Tables 2 and 3, the September 25, 2012, LAR provided two graphs of additional x/Q values derived from sensitivity studies performed by Duke Energy. Please confirm that the LAR is seeking approval of all six sets and only the six sets of x/Q values listed in Tables 2 and 3.
Duke Energy Response Duke Energy confirms that in its LAR of September 25, 2012 (Ref. 1), it seeks approval from the NRC for all six sets and only the six sets of the control room x/Q values listed in Table 2 and 3.
The additional control room x/Q values shown in the graphs of Figures 1 and 2 in this LAR were calculated in a sensitivity study completed only to justify the values presented in Table 2 for the control room x/Qs "MSLB Same Unit Inboard x/Q" and MSLB Same Unit Outboard x/Q."
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d) Identify the inputs in Table 1 that apply to the main steam line break (MSLB) outboard x/Q values provided in Table 2.
Duke Energy Response As stated in the response to Question 1.b, the inputs taken for the calculation of the MSLB outboard x/Q values provided in Table 2 were not listed in Table 1. They have been provided in new Table 1.b-1 (see the response to Question 1.b).
e) Based on the inputs provided in Table 1, initial NRC estimates suggest that the inboard Doghouse x/Q values are larger than the outboard Doghouse x/Q values. Provide the basis for providing the cross unit outboard Doghouse x/Q values in Table 3.
Duke Energy Response Duke Energy understands the NRC to be asking about the cross unit x/Qs for releases in the Doghouses. A cross unit x/Q for a release from the inboard Doghouse would bound that of a release from the outboard Doghouse; however, this inboard cross unit X/Q may be excluded from the submittal for the following reasons.
The calculation of these x/Qs includes a "wind direction window" evaluation. A wind direction evaluation is completed for each post accident release point pursuant to Regulatory Guide 1.194 (Section 3.3.2). If two control room intakes are in the same 900 wind direction window, then the cross unit x/Q is used along with the same unit control room x/Q to calculate a composite x/Q pursuant to the guidelines of Regulatory Guide 1.194 (Equation 5c) to simulate transport of contaminated effluent with dispersion to both intakes. If only one control room intake is in a 900 wind direction window, then the cross unit x/Q is not used.
As described in the submittal dated March 20, 2008 requesting approval for full scope implementation of the method of Alternative Source Terms (Ref. 3), McGuire Nuclear Station is equipped with four control room intakes. These intakes are in pairs with the two intakes in each pair close to the point that in the calculation of composite x/Qs, McGuire is considered to be a dual intake plant. In particular, the wind direction evaluation was completed with this assumption.
The wind direction window evaluation demonstrates that for a break inside an outboard Doghouse, both control room intakes are in the 900 window. For a break inside an inboard Doghouse, only the same unit intake is in the 900 window. The cross unit x/Q for a main steam line break inside an outboard Doghouse only will be used to calculate a composite control room X/Q as discussed above. It is for this reason that Table 3 lists values for the cross unit outboard Doghouse X/Q but not values for the inboard Doghouse x/Q.
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f)
Please confirm that the horizontal length of the louvers on the south walls of the Doghouses is at least 8.88 meters long, as implied by the initial ory input of 1.48 meters provided in Table 1. Further, confirm that it is reasonable to assume that the release rate from the building interior is essentially equally dispersed over the entire length of the louver because release characteristics, mixing, transport, and the arrangement of internal components within the Doghouses facilitate such an assumption.
Duke Energy Response The louver openings on the south wall of each outboard Doghouse span at least 8.90 meters.
This yields the value of 1.48 taken pursuant to the NRC guidelines (Ref. 2) for cry for releases from the louvers on the Doghouse south wall, the wall closest to the control room intake pairs.
In sizing the line source, it was assumed that effluent would be released from the Doghouse only through the louver openings on its south wall. Louver openings also span the outer wall (away from the reactor building) and the north wall. It was assumed that no effluent would be released through any of these openings, but only those on the south wall. From this it is seen that taking the south wall openings only as the line source incorporates some conservative margin into the calculation of 1.48 meters for ay.
Several considerations confirm the appropriateness and conservatism of taking a line source for the louvers on the Doghouse south wall and support taking a uniform distribution of the releases across the Doghouse louvers. Identified in a review of general arrangement drawings and a walkdown of an outboard Doghouse, the considerations are as follows:
Each Doghouse contains two main steam line segments, routed from the Doghouse to the yard through penetrations in the south wall of the Doghouse. The steam line exiting the Doghouse closest to the control room intakes exits the Doghouse a little more than midway - by 2.6 feet -
from the reactor building to the Doghouse outer wall. In the calculation, the center of the line source was placed at the midline of the south wall. This places it on the side of the limiting main steam line in the direction of the reactor building and control room intakes. These aspects indicate that the centering of the line source of the LAR is conservative.
The control room x/Q values which were presented in Table 3 of the LAR of September 25, 2012 will be used to calculate the control room radiation dose for a MSLB inside a Doghouse and upstream of the Main Steam Isolation Valve (MSIV) for the faulted steam generator (SG).
The limiting break for this MSLB scenario is immediately behind the MSIV for the faulted SG.
This places the limiting location of the MSLB inside the Doghouse approximately 10.4 ft from the outside edges of the louver openings. On the other hand, the centerline of each main steam line segment behind its MSIV is 19 feet below the bottom edges of the louvers. It also is noted that the centerlines of each MSIV is 28 feet above the grade level. This provides a large space for mixing of the effluent released from the MSLB and ensures uniform distribution of effluent across the louvers on the Doghouse south wall.
Very few internal structures and components are inside each Doghouse between grade level and its ceiling. The only obstructions observed in the interior of the Doghouses up to the ceiling are:
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two main steam line segments segments of the two main feedwater lines routed in each Doghouse two SG Power Operated Relief Valves and exhaust vents ten Main Steam Safety valves and exhaust vents
" three support columns six longitudinal support beams seven support cross beams support hangars ladders and guard rails.
grating platforms instrument air tubes, instrument and power cables, struts, hangers.
Nearly all of these structures and equipment are at least 10 feet behind the MSIVs. It was observed that interior of the Doghouse from grade level to the ceiling is mostly free of obstructions. In particular, the obstructions in the space between the main steam lines near the MSIVs and the south wall openings are relatively small: ladders, guard rails, instrument air tubes, instrument and power cables, hangers, struts. These will not discernibly block flow from a broken main steam line behind a MSIV. The only larger obstructions in this space are segments of two longitudinal support beams also serving as walkways. Their location will not skew MSLB break flow towards the reactor building and control room intakes.
From these observations, it is reasonable to assume a uniform distribution of effluent across the south wall louvers of the Doghouses.
The general arrangement and layout inside the Doghouses have been assessed as discussed above. It has been noted that a large space between the limiting MSLB location (immediately behind a MSIV) and the louvers on the south wall is available for effluent released from a MSLB to mix so as to validate the assumption of uniform distribution across the louvers. This space has been found to be mostly free of obstructions. Finally, the louvers on the outer and north walls are not represented in the 8.9 meter line source on the south wall. This confirms the appropriateness and conservatism in setting ry to a value of 1.48 meters for a MSLB inside a Doghouse.
g) With regard to the louvers on the south walls of the Doghouses, Section 2.2 of states that "the release is assumed to originate from a line projected perpendicular to the line of sight between the receptor and the building surface closest to the control room intake." Attachment 2 provides a simplified drawing showing plant structures and the control room intakes. Please highlight the assumed release locations on Attachment 2 and discuss if the direction, distance, and height inputs are based upon straight line or "taut string" estimates, as discussed in Regulatory Guide 1.194, Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants.
Duke Energy Response In the calculation of the control room x/Q for a MSLB inside a outboard Doghouse, the release location was taken to be the louver openings on the Doghouse south wall. The Doghouse release locations are drawn on a copy of Attachment 2 of the LAR (Ref. 1), labeled here as Figure 1.g-1 and provided here as the last page of this attachment. The outboard Doghouse 6
release lines are shown as "double arrow" lines. Distances and directions were obtained based upon taking the transport of the effluent on a straight line, the "straight line" estimate.
- 2. Figure 2 of Attachment 1 is a graph of the Unit 1 inboard MSLB variable receptor to source angle sensitivity. Please confirm that the plotted values are distances from the closest release point along the main steam line and do not represent numeric distances of each point from the control room intake.
Duke Energy Response Figure 2 is a plot of "0-2 hr" values of a control room x/Q for a break of an inboard main steam line closer to a control room intake." The submittal of September 25, 2012 states that "Figure 2 shows the x/Q results [over the interval of 0-2 hr] for release points along the Unit 1 inboard main steam line with distance [+/-] along the steam line being relative to the point of minimum distance to the intake" (Ref. 1, Attachment 1 and Page 4-5). The LAR effectively defines the "point of minimum distance" (shown as 0.00 on the abscissa of Figure 2) as 7.5 meters from the nearer control room intake pair (Ref. 1, Section 2.1.1). Any other "distance" on this axis corresponds to a horizontal distance from the control room intake of 156.25 + d2 where d is the distance (in meters) along the main steam line relative to the point on it closest to the nearer control room intake pair.
References
- 1. Steven D. Capps to U.S. Nuclear Regulatory Commission, "Duke Energy Carolinas, LLC McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 Submittal of Atmospheric Relative Concentration Values for use in Control Room Envelope Radiological Dose Analysis," September 25, 2012, ADAMS ML1227A343.
- 2. Regulatory Guide 1.194, June 2003, "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants."
- 3. Bruce H. Hamilton to U. S. Nuclear Regulatory Commission, "Duke Power Company LLC d/b/a Duke Energy Carolinas, LLC McGuire Nuclear Station, Units 1 and 2 Docket Numbers 50-369 and 50-370 License Amendment Request for Full Scope Implementation of the Alternative Source Term," March 20, 2008, ADAMS ML08093050.
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- 4. 1Q MWST UNT.I Figure 1.g-1