NL-12-2273, Request to Revise the Plant Service Water Pump Well Minimum Water Level - Response to Request for Additional Information Regarding Support of Post-Accident Cooling Requirements for 30 Days
| ML12338A029 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 11/30/2012 |
| From: | Ajluni M Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-12-2273 | |
| Download: ML12338A029 (11) | |
Text
Mark J. Ajluni. P.E. Southern Nuclear Nuclear Licensing Director Operating Company. Inc.
40 Inverness Center Parkway Post Office Box 1295 Birm ingham. Alabama 35201 Tel 205.992.7673 Fax 205.992.7885 SOUTHERN'\'
COMPANY November 30, 2012 Docket Nos.: 50-321 NL-12-2273 50-366 U. S. Nuclear Regulatory Commission ATrN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Request to Revise the Plant Service Water Pump Well Minimum Water Level Response to Request for Additional Information Regarding Support of Post-Accident Cooling Requirements for 30 Days Ladies and Gentlemen:
On July 5, 2012, Southern Nuclear Operating Company (SNC) requested amendments to the Edwin I. Hatch Nuclear Plant (HNP) Units 1 and 2 Technical Specifications (TS) . The proposed amendments would revise the minimum water level referenced in the Units 1 and 2 TS Surveillance Requirement (SR) associated with the Limiting Condition for Operation (LCO) for the plant service water (PSW) system and ultimate heat sink (UHS) (LCO 3.7 .2) .
By letter dated October 31, 2012, the NRC requested additional information regarding the demonstration that the proposed PSW pump well minimum water level of 60.5 feet mean sea level will ensure sufficient water over a 30 day period post-accident to support cooling requirements . Enclosure 1 provides the response to the NRC request for additional information (RAI) .
This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at (205) 992-7369.
Edwin I. Hatch Nuclear Plant Request to Revise the Plant Water Pump Well Minimum Water Level Response to for Additional Information Regarding Support of Post-Accident Cooling Requirements for 30 Enclosure 1 Response to Request for Additional Information Regarding Support of Post-Accident Cooling Requirements for 30
U. S. Nuclear Regulatory Commission NL-12-2273 Page 2 Mr. M. J. Ajluni states he is Nuclear Licensing Director of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and , to the best of his knowledge and belief, the facts set forth in this letter are true.
Sworn to and subscribed before me this !J 0-+1\ day of Nov ~ fI1 ) e. r ,2012.
~F# 1-JujL;~
otary Public My commission expires: M~rrh :2-3,, Z,b! If Respectfully submitted ,
M. J. Ajluni Nuclear Licensing Director MJAlCLT/lac Enclosure : 1. Response to Request for Additional Information Regarding Support of Post-Accident Cooling Requirements for 30 Days cc: Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman , President & CEO Mr. D. G. Bost, Executive Vice President & Chief Nuclear Officer Mr. D. R. Madison , Vice President - Hatch Mr. B. L. Ivey, Vice President - Regulatory Affairs Mr. B. J. Adams , Vice President - Fleet Operations RType : CHA02.004 U. S. Nuclear Regulatory Commission Mr. V . M. McCree, Regional Administrator Mr. R. E. Martin, NRR Senior Project Manager - Fleet Mr. E. D. Morris , Senior Resident Inspector - Hatch State of Georgia Mr. J . H. Turner, Environmental Director Protection Division to I\JL-12-2273 RAI Response - Support of Post-Accident Cooling Requirements for 30 Days NRC Question 1 As stated in the license amendment request (LAR), Edwin I. Hatch Nuclear Plant, Units 1 and 2 (HNP 1 and 2), uses a recession formula equation to compute the projected time (in days) for the plant service water (PSW) pump well level to reach 60.0 ft mean sea level (MSL), which is the minimum level required for post loss-of-coolant-accident cooling requirements as limited by the Standby Service Water Pump. This formula contains a recession constant represented by the letter uk" (also known as depletion factor) which represents the type of flow (surface runoff, interflow, or base flow) that dominates the area being studied.
Furthermore, the LAR states that it uses a value of 0.995 (base flow in stream flow is dominant) for the recession constant when using the equation.
However, reference 3 of the LAR states that the overlapping ranges for the selection of "k" values represent the inherent difficulties in identifying a particular recession as being surface runoff, interflow, or base flow. Furthermore, Reference 3 also lists the range for baseflow as being between 0.93 - 0.995 and the LAR states that its baseflow uk" range goes from 0.995 - 0.997.
a) Please provide additional information on the general process, criteria and analysis that has been used by the licensee in order to determine the recession constant uk" value of 0.995 for the site, with special emphasis on how the aforementioned limitations of Reference 3 were resolved, if applicable. These limitations include, but are not limited to, establishing distinctions between interflow and baseflow, seasonally variable components of baseflow analyzed over a specified period of time, etc.
b) Please provide an explanation on what effect or consequences, if any, is presented by the licensee selecting a baseflow range (0.995 -0.997) for uk" that is higher than that stated by the source reference listed in the LAR (0.93 - 0.995). The explanation should also have a special emphasis on the acceptability of the licensee selecting values higher than those stated in the reference paper (Reference 3 of the LAR). Additionally, the LAR states that the recession formula has been used for a number of years. Therefore past precedence and/or references should be included as part of the response, if available.
c) Please clarify if the recession formula was used using the same "k" value (0.995) for each river level in the discharge rating table or if different uk" values, as permitted by the HI\JP 1 and 2 range (0.995 - 0.997), were used when determining the projected time to reach 60.0 ft MSL. If a range of values were used, additional information that justifies this method and demonstrates added conservatisms should be included. In addition, past precedence and/or references should be included as part of the response, if available.
E1-2
OSl-A(~clljerlt Cooling Requirements for 30 SNC Response a) The following is in the LAR which is referenced in NRC question 1:
"The formula (References 2 and 3) is expressed as Q1 = Qoe- 01
, O( is the stream flow at time t, 0 0 is initial stream flow. The term in this equation is replaced by 'k', called the constant or factor, which is commonly used as an indicator extent The typical ranges of recession constants for streamflow components are 0.2 - 0.8 for runoff (hi water), 0.7 interflow for groundwater flow (baseflow) and they overlap. (e.g., > 0.9) tend to dominance in streamflow (Reference 3). The 'k' typically at HNP is range for the 'k' value from 0.997."
a recession formula, also to as a curve, to determine the number of days it will water level to decrease from the 1 minimum level of ft MSL to the minimum water level at which post-accident requirements can be met which is 60.0 ft MSL The 'k' value range for HNP is on applicable river flow data, also rOT£,rrCI,.,
to as river at HNP intake.
A review of river flow for the last 12 years supports a value of 0.995 for
'k' as demonstrated by the following Figure 1. For each day on the timeline the maximum flow, median flow, and minimum flow is selected from river flow since the year 2000. Figure 1 data graphically with the maximum "flow line showing the highest of the high flows each and the minimum flow line showing the lowest of the low flows for 2000 through 2011.
minimum flow line over a selected period one can of solving for 'k' are provided following (method) for solving for 'k' solving for 'k' using two points line on 1. Example 3 flows interpolated from the 1 2 for PSW pump well water levels of specifically 718 cfs and 517 cfs (see the SNC for the basis for these water levels and flows).
3 show that using 0.995 for 'k' is supported by the
-3 to NL-12-2273 RAI Response - Support of Post-Accident Cooling Requirements for 30 Days Figure 1 Altamaha River Flow Data at Hatch since the Year 2000 100000 1==___ '\ ~--Ji!.. 4~-.....-+ -...----..----.,.--------------...
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-M~ x - M in -1v1f'rli~n R1? - ?nn 7 - ?nnR - ?n1n -?n11 - RAI E1-4 to I\JL-12-2273 RAI Response - Support of Post-Accident Cooling Requirements for 30 Days Examples of Solving for 'k':
- 1) 0 1 == 0 0 X kt 0;0 0 ::::: kt Log(O/Oo) == t x Log k Log(O/OoVt = Log k 1OL09(OtlOO)/t = 1OLog k 1OLo9(OtlQO)/t == k
- 2) Solving for 'k' using two points 30 days apart from the minimum flow line on Figure 1:
0 0 ::::: 1650 cfs June 4 point from minimum flow line 0,::::: 1400 cfs July 4 point from minimum flow line t::::: 30 days 1400 = 1650 x k30 1400/1650 ::::: k 30 Log(1400/1650) ::::: -0.071356 == 30 x Log k Log(1400/1650)/30 == -0.00238 == Log k 1oLog(1400/1650)/30 = 10.000238= k 0.99454::: k
- 3) Solving for ok' using the river flows interpolated from SNC July 5, 2012 LAR Enclosure 1 Table 2 for 60.5 ft MSL and 60.0 ft MSL, specifically 718 cfs and 517 cfs. Please reference the line labeled RAI on Figure 1.
0 0 ::::: 718 cfs 0 1 ::::: 517 cfs t = 66 days 517 == 718 x k66 517/718 = k 66 Log(517/718) = -0.1426 :::: 66 x Log k Log(517/718)/66:::: -0.00216:::: Log k 1OLog(5171718)/66 :::: 10.0 ,00216 :::: k 0.995036:::: k Based on the historical data continuing to support use of 0.995 for ok', the recession formula, using 0.995, is currently used for the annual updating, per SNC procedure, of the time (in days) for the PSW pump well level to reach 60.0 ft MSL when starting from the TS SR 3.7.2.1 minimum level. HI\JP low river level procedural actions, which start at a river level of 62.5 ft MSL, include required more frequent river level projections as river level gets closer to the SR 3.7.2.1 minimum level. Again those projections use the recession E1-5 to RAI Cooling Requirements for formula with a 'k' and also consider the trend of current flow data.
The distinction interflow and baseflow is determined by a review of the historical river flow data in Figure 1, specifically looking for a change in of minimum flow line. Based on the graphical review, "flows above 2000 are generally considered interflow and flows below 2000 cfs are baseflow. However, the distinction of interflow vs.
baseflow is not to a conservative demonstration of being to support cooling requirements for 30 days. of a 'k' appropriately flow data is technically justified.
3 serve as sources for the recession curve of the terms runoff, interflow, constants from Reference 3 was to 1'10,,,I"Y't"'\o the flow at interflow and baseflow b) As covered in to NRC question 1a, the 'k' value used by HNP is based on historical river flow data at the HNP intake and appropriate consideration of trend of current river flow data when operating under HNP low river actions. The HNP low river procedural of ft MSL and include more frequent river level projections as gets closer to the SR 3.7.2.1 minimum level. A lk' value of is typically used at the beginning of the dry season generally is not to a higher value because 0.995 has a drop than 0.997, thus providing a decay rate. Again the LAR Reference 3 baseflow of which was only referenced in the LAR as typical, is not to HNP since SNC is basing 'k' on both river flow at the HNP intake and, when appropriate, the trend of current river flow the number of days it will to not'YO!:!':::O from the proposed ft MSL to the minimum water level at can be met which is 60.0 ft MSL.
Finally, as in July 2 LAR Enclosure 1 section 3.2, SNC requested review of application of this recession formula by the USGS.
The USGS letter documenting review was provided in the LAR Enclosure 4. following:
"The stated objective of analysis is to 'verify sufficient water supply at river intake for low The normal groundwater-depletion curve method that you predicts decreased streamflow during ovtont'1ol'1 dry review indicates that your methods are conservative and ",,,,tl,,,t"'.f't,, for your stated objective."
to Response Requirements for Days c) As covered in the response to questions1 a and 1b, the 'k' value of 0.995 is by HNP, based on river flow data at HNP intake.
A change of that 'k' value would only necessitated by a flow data or, appropriate, the trend of current river flow the 'k' value is the same whether we are projecting the in for the water to drop from the current TS SR 3.7.2.1 minimum level of 60.7 ft ft MSL or the water the 60.5 ft MSL to 60.0 ft It is noted that referenced 'k' value is not in the development of the HNP intake structure discharge rating specifically the SNC July 5,2012 LAR Enclosure 1 2. The following from LAR Enclosure 1 3.2 describes how 2 was developed:
"For development of an HNP intake structure discharge the Baxley discharge data on August 22, the most data for extended dry conditions. The river intake structure is updated on at an annual basis per procedure. When updating the HNP intake structure discharge rating table, the Baxley gage discharge is adjusted to:
It Reflect an estimated static drop of intake structure, intake structure traveling water screens.
It Reflect reference elevation at Baxley gage of 61.08 The elevation is used a datum elevation is not provided current Baxley gage by "
NRC Question 2 h/O'fon=>nr'O 3 states that any is a that varies from recessions on several factors.
longer period it is necessary to individual base flow, ..."'..........
in order to provide an average characterization of base flow, called a master recession curve (MRC). Furthermore, it states that the MRC represents the most frequent depletion simulation since recession rates are influenced by antecedent recharge conditions.
a) Please provide a detailed explanation that clarifies the threshold of what constitutes a event versus a event in terms to a or a curve. should emphasize why option selected to characterize baseflow at HNP 1 and 2 is acceptable in comparison to the versus average demonstrate that the most frequent depletion simulation has been obtained based on the method selected and, used to determine
-7
I\lL-12-2273 Support of Cooling Requirements Days to reach 60.0 ft In past and/or rOr,"'YOnl'l::' should be included as part of the response, if available.
SNC Response a) in the SNC response to NRC question 1, the 'k' used by on historical river flow at the HNP intake from 2000 11 and appropriate consideration of the trend of current river flow operating under HNP low river level procedural This methodology appears to use of a MRC curve as in NRC 2a.
SNC use of river flow data from 2000 through 2011 supports development of a 'k' value based on long-term trends vs. potential short-term As stated previously, when operating under HI\lP low river level procedural actions as river closer to the 1 minimum level, appropriate of the trend of current short-term river flow may result in a to the 'k' value. on past use of a 'k' value different than 0.995 is rare.
The states that, based on 2 LAR and the use recession equation, the time (in days) for the water level to drop to 60.0 ft MSL would be 66 days. However, it is not clear from 2 how this value was a) provide a summary of the calculations performed in order to obtain the of from Table 2 of a to of Figure 3 in the LAR, which visually shows the "River Level versus Time" plot using obtained results from equation and table.
This figure should clearly demonstrate the availability of water for days before reaching river level 60.0 ft MSL, as required by the limiting Standby Water Pump.
a) The formula, as covered is expressed as is stream flow at is initial stream flow. term in this equation is replaced by 'k'. 'k' value used is 0.995. flow of = 718 cfs and Or =517 are obtained by interpolation the July 5, 2012 submittal 1 Table 2's third and fourth columns as in Enclosure 1 3.2 as follows:
.......,.,.;v"'" on consideration of river flow and the limiting minimum of 60.0 it MSL on minimum submergence of ft for the standby service water pump), safe shutdown can be met at a well water level of ft MSL.
of Post-Accident Cooling pump well water of to assure that the UHS would remain available for interpolated from Table 2, the river at 60.5 ft MSL and 517 cfs at 60.0 ft MSL, with both flows to support safe shutdown cooling requirements.
flows from the HNP intake structure discharge rating 2, are as input to demonstrate that the proposed PSW pump well minimum water level of 60.5 ft MSL provides margin to assure the would remain available for 30 days post-LOCA."
By solving for time t as shown below the duration of 66 days is obtained.
t x Log(0.995)
== -0.143/-0.002177 b) formula is expressed in terms of river flows, RAI on Figure 1 for the requested graphical from the recession formula and Table E1-9