L-2010-226, Summary of NRC Public Meeting Discussion on Meteorological Data for Alternative Source Term and Conforming License Amendment Request 196

Summary of NRC Public Meeting Discussion on Meteorological Data for Alternative Source Term and Conforming License Amendment Request 196

ML102880046
Person / Time
Site:	Turkey Point
Issue date:	10/13/2010
From:	Kiley M Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2010-226
Download: ML102880046 (7)

Text

0OCT 13 2010 FPL. L-2010-226 POWERING TODAY. 10 CFR 50.90 EMPOWERING TOMORROW."

U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555-0001 Re: Turkey Point Units 3 and 4 Docket Nos. 50-250 and 50-251 Summary of NRC Public Meeting Discussion on Meteorological Data for Alternative Source Term and Conforming License Amendment Request 196

References:

(1) W. Jefferson (FPL) to U.S. Nuclear Regulatory Commission (L-2009-133),

"License Amendment Request 196: Alternative Source Term and Conforming Amendment," Accession No. ML092050277, June 25, 2009.

(2) W. Jefferson (FPL) to U.S. Nuclear Regulatory Commission (L-2009-163),

"Transmittal of Meteorological Data CD Supporting Alternative Source Term and Conforming License Amendment Request 196 - Supplemental Information,"

Accession No. ML100680718, July 21, 2009.

(3) J. Paige (NRC) to M. Nazar (FPL), "Turkey Point Units 3 and 4 - Request for Additional Information Regarding Request to Adopt the Alternate Source Term (TAC Nos. ME1624 and ME1625)," Accession No. ML100700446, March 24, 2010.

(4) Email from J. Paige (NRC) to S. Franzone (FPL), Follow-up Requests for Additional Information RE Turkey Point, Unit 3 and 4 AST LAR, Accession No. ML101480750, May 28, 2010.

(5) M. Kiley (FPL) to U.S. Nuclear Regulatory Commission (L-2010-121), "Revised Meteorological Data for 2005-2009 Supporting Alternative Source Term and Conforming License Amendment Request 196," Accession No. ML101650648, June 11, 2010.

(6) M. Kiley (FPL) to U.S. Nuclear Regulatory Commission (L-2010-13 1), "Response to 5/28/2010 Request for Additional Information (RAI) Regarding Alternative Source Term (AST) License Amendment Request (LAR) 196 (TAC Nos. ME1624 and ME1625)," Accession No. ML101760019, June 23, 2010.

(7) M. Kiley (FPL) to U.S. Nuclear Regulatory Commission (L-2010-137), "Revised Radiological Dose Consequences for Alternative Source Term and Conforming License Amendment Request 196," Accession No. ML101800222, June 25, 2010.

(8) M. Kiley (FPL) to U.S. Nuclear Regulatory Commission (L-2010-136), "Revised Meteorological Data for 2005-2009 with AT Bias Supporting Alternative Source Term and Conforming License Amendment Request 196," Accession No. ML102510127, September 2, 2010.

an FPL Group company

Turkey Point Units 3 and 4 L-2010-226 Docket Nos. 50-250 and 50-251 Page 2 of 3 By letter L-2009-133 dated June 25, 2009 [Reference 1], Florida Power and Light (FPL) requested to amend Facility Operating Licenses DPR-3 1 and DPR-41 and revise the Turkey Point Units 3 and 4 Technical Specifications (TS). The proposed amendments revise the TS to adopt the Alternative Source Term (AST) as allowed in 10 CFR 50.67.

The meteorological data for 2003-2007 originally used to support the AST License Amendment Request (LAR) was transmitted to the NRC staff by letter dated July 21, 2009 [Reference 2]. Subsequent NRC review of this meteorological data resulted in questions regarding the quality of the data as submitted for this period [References 3, 4].

Based on further evaluation of this data, FPL decided to revise the meteorological data set to include more recent meteorological data from years 2008-2009 that was not previously available. On June 11, 2010, FPL submitted revised meteorological data for years 2005-2009 [Reference 5]. Resolution of the quality issues that were raised regarding the calibration of the meteorological tower temperature sensors resulted in a conservative decision to bias vertical temperature differentials (AT) with the average (mean) calculated value for each channel over each calibration interval for the hourly meteorological data. On June 23, 2010, FPL provided its RAI response by letter L-2010-131 in which the basis for using the temperature biased meteorological data was discussed in detail [Reference 6]. On June 25, 2010, FPL provided the revised AST radiological dose consequences by letter L-2010-137 [Reference 7]. On September 2, 2010, FPL submitted the revised meteorological data for years 2005-2009 with the AT bias corrections [Reference 8] to facilitate the NRC review.

On October 1, 2010, a public meeting was held on AST meteorological data issues between the NRC and FPL representatives. A summary of the technical issues discussed in the meeting is provided in the Attachment to this letter.

In accordance with 10 CFR 50.91 (b)(1), a copy of this letter is being forwarded to the State Designee of Florida.

This letter does not alter the significant hazards consideration or the environmental assessment previously submitted by FPL letter L-2009-133 [Reference 1].

This letter contains no new commitments and no revisions to existing commitments.

Should you have any questions regarding this submittal, please contact Mr. Robert J.

Tomonto, Licensing Manager, at (305) 246-7327.

Turkey Point Units 3 and 4 L-2010-226 Docket Nos. 50-250 and 50-251 Page 3 of 3 I declare under penalty of perjury that the foregoing is true and correct.

Executed on October /3, 2010.

Very truly yours, Michael Kiley Site Vice President Turkey Point Nuclear Plant

Attachment:

. Summary of NRC Public Meeting on AST Meteorological Data cc: USNRC Regional Administrator, Region II USNRC Project Manager, Turkey Point Nuclear Plant USNRC Resident Inspector, Turkey Point Nuclear Plant Mr. W. A. Passetti, Florida Department of Health

Turkey Point Units 3 and 4 L-2010-226 Docket Nos. 50-250 and 50-251 Attachment Page 1 of 4 NRC PUBLIC MEETING TECHNICAL ISSUES

SUMMARY

APPROACH TO METEOROLOGICAL DATA USAGE

SUMMARY

The meteorological data for years 2005-2009 was selected to support the Turkey Point AST submittal and included selected substitution of missing or bad data under strict rules.

The quality checked meteorological data was found to be in compliance with applicable Regulatory Guide (RG) 1.23 guidelines with the exception of the measured, temperature differentials for some of the calibration periods. Rejection of the meteorological data for these periods was not required since the errors could be quantified and corrected. The process chosen to correct the errors was determined to be reasonable, although alternative methods were considered, and the resulting values were found to be representative of the meteorological conditions present at the site. The result of the process was a "corrected" temperature biased data set with which a "corrected" set of atmospheric dispersion factors (x/Qs) was produced. A comparison of the results of the radiological dose consequence analyses for the unbiased and biased data input yielded only a 0.02 rem TEDE increase in the limiting LOCA dose consequence.

Whereas correction of the 2005-2009 meteorological data was intended to provide for a "representative" data set, the use of that data set was intended to ensure a "conservative" result for each of the radiological dose consequence analyses. This latter objective was achieved by conservatively choosing a composite of the "worst case" 7x/Qs between the unbiased and biased y/Q results and reducing the allowable control room in-leakage from 115 to 100 cfm. The resulting dose consequences were therefore conservative relative to both the meteorological data used and the margin to the regulatory acceptance limits.

DETAILED DISCUSSION Appropriateness of Selected Meteorological Data The meteorological data for years 2005-2009 was selected to support the Turkey Point AST submittal. The meteorological data included wind speeds, wind directions, and dual channel ambient air temperatures at both 10 meter and 60 meter elevations. All data was quality checked. Substitution for missing or bad data was allowed (when alternative data sources were available), but these substitutions were subject to strict rules. The Channel A temperatures were considered the primary source and the Channel B temperatures were considered the secondary source.

The meteorological data for years 2005-2009 was collected with temperature sensors that met the Turkey Point procedural requirements for instrument accuracy but did not meet all of the guidance specified in RG 1.23. The calibration procedures assured that the temperature instruments met the ambient temperature detection accuracy (+/- 0.97F) specified in RG 1.23 but did not necessarily assure that these temperature instruments met the specified accuracy for vertical .temperature difference detection (+/-0.1 8'F).

Note that despite this procedural shortcoming, roughly half of the vertical temperature difference (AT) measurements fell within the specified instrument tolerance. In addition, sufficient data was recorded to allow for determination of as-left (post-installation) and as-found (prior to replacement after six months of service) differences between the indicated and actual ATs that existed at these discrete points in time.

Turkey Point Units 3 and 4 L-2010-226 Docket Nos. 50-250 and 50-251 Attachment Page 2 of 4 Applying the RG 1.23 guidance to the Turkey Point meteorological data from 2005-2009 would have eliminated a large number of AT readings, yielding a stability class data recovery percentages significantly below the target 90% recovery rate identified in the Regulatory Guides covering X/Q evaluation. The Turkey Point meteorological data, however, is not unacceptable since the "error" between indicated and actual AT is neither random nor unknown. Rather, the "error" is systematic and can be evaluated at periodic time points based on M&TE accuracy records. The accuracy of each of the temperature indicators was evaluated both at the time of its installation and at the time of its replacement, giving a time-based trend in their performance. These time interval specific "calibration correction factors" can be used to compensate for the known bias at the start of an instrument's life, and can also be used to address the change in that bias as the instrument ages. Therefore, Turkey Point has proposed that there is, in fact, sufficient information contained in the combination of the database hourly readings and as-left and as-found data records to permit suitably accurate determination of AT readings that are used to determine stability class on an hourly basis.

Appropriateness of Application of Measurement Corrections Once it was determined that sufficient information existed in the recorded data and in the time of installation accuracy measurements, Turkey Point considered several alternative means to apply the measurement bias/calibration information. Sensitivity studies were run to apply a large constant offset (for all five years of data) in a positive AT direction, and separately, in a negative AT direction. The result of this simple process was that the X/Q results and consequently the dose results were inappropriately skewed. This result occurred since the constant five-year bias process moved a very large number of hourly readings into "worse" stability classes than were indicated by either the unbiased data, or by the results of more reasonable biasing schemes discussed below. For example, the six month time period as-left A-Channel bias for December 2007 was negative (-0.74 0 F) while the as-found June 2008 A-Channel bias was slightly positive (0.04'F). The sensitivity study's application of the statistically bounding constant positive offset generated stability classes that are clearly not supported by this time period's measured data. Similarly, the six month time period as-left/as-found A-Channel biases for December 2008 to June 2009 were both positive, but the sensitivity study's application of the constant negative offset also clearly generates stability classes that are not supported by measured data. See Table 4-3 of Reference 1.

Another biasing option considered was to choose the "worst" offset between the as-left and as-found points and apply this offset for a whole six month time period. "Worst" would have to be defined by trial and error processing of biased results through x/Q codes but could be done. The outcome of this approach would again be skewed and not representative of actual conditions. Any given offset selected would be reasonably accurate for only the very beginning or the very end of a given six month time period.

Thus, it would be clearly inappropriate for the other end of the time period. Again, for example, the A-Channel positive offset of 0.30'F observed at the end of the December 2006 time period, when applied to the beginning of the time period (June 2006) where a negative offset of -0.1 8°F was documented, would be inappropriate.

Turkey Point Units 3 and 4 L-2010-226 Docket Nos. 50-250 and 50-251 Attachment Page 3 of 4 Yet another biasing option would have been to determine and apply a linearly interpolated bias, which would vary in magnitude from the as-left observed bias, to the observed as-found bias six months later. Given the lack of any benchmark calibration information between the two end points, the linear assumption is reasonable, and simplifies the data processing. The experience base for the performance of these instruments qualitatively supports this "linear drift" assumption, but no numerical or other quantitative validation for this assumption is available. Turkey Point considers this option to be the one that would yield the "most accurate" representation of the true meteorological conditions. In practice, however, the generation and application of this hour by hour change in the applied AT correction would require a significant amount of additional resources but would not provide significantly different results than the "variable, six month average bias" method described in the next paragraph.

A simplified approximation of the linearly interpolated bias method of correcting the Turkey Point meteorological data was used in the AST submittal. For each six month time interval where as-left and as-found AT information was available (for A- and B-Channels, separately), an average AT bias was computed, and applied for the entire six month interval. For example, if the A-Channel as-left bias was negative at the beginning of a time period (i.e. -0.1 8°F in June 2006), and the as-found bias was positive at the end of the time period (+0.30'F in December 2006), then a small positive bias (0.0607F),

applied as a constant, would be somewhat overly corrective for the first half of the period, and correspondingly under-corrective for the second half. Over the course of five years of data, with the bias changing as appropriate at each six month interval, the combination of under-correction and over-correction would average out to yield a set of AT and resulting stability class values that were appropriate for use in determining X/Qs using ARCON96 and PAVAN.

Appropriateness of Met Data Screening, Processing, and Conservative Application Turkey Point has provided documentation that the 2005-2009 meteorological data set used in the dose analyses was adequately acquired and initially screened by appropriate means to ensure that any invalid measurements were rejected. Further, any substitutions (either from the Land Utilization 10 meter tower or from one South Dade 60 meter tower instrument channel to one another) were allowed only under consistently applied sets of conditions, throughout the five year period. Once the data set was finally assembled, numerical screening (using the METD suite of programs, originally developed by the NRC for this use) was applied, and any anomalies were investigated and appropriately resolved. Finally, trend plots of the meteorological data were qualitatively examined to identify any trend related anomalies that might have been missed by numerical screening.

See Reference 1 for further details.

This unbiased meteorological data set ATs were then subjected to a "variable bias" which changed approximately every six months, to reflect the as-left/as-found performance of the individual temperature sensor readings. Differential air temperatures between the 10 meter and 60 meter indicated values for each channel were appropriately biased to compensate for the observed temperature sensor instrument drift over each six month instrument calibration interval. Both sets of meteorological data (unbiased and variable biased) were independently processed through the z/Q codes ARCON96 and PAVAN.

Turkey Point Units 3 and 4 L-2010-226 Docket Nos. 50-250 and 50-251 Attachment Page 4 of 4 A conservative, composite set of highest y/Q results was created by comparing the unbiased and variable biased result for each X/Q value. See Reference 2 for a detailed table of the conservatively selected composite set of x/Qs, with Footnote 5 denoting the individual cases where the more conservative variable biased X/Qs were selected in lieu of the X/Qs determined from the unbiased meteorological data.

While discussing at length the process used to identify, select, and apply the appropriate corrections to the meteorological data, an NRC reviewer asked what the overall impact on dose consequences were (unbiased meteorological data versus biased meteorological data). Sensitivity studies were run which showed that the radiological dose consequence analyses for LOCA yielded a maximum difference between the variable biased and unbiased cases of only 0.02 rem TEDE. This comparison confirms that the overall dose consequence impact due to "errors" or flaws in the meteorological data is small.

In summary, the unbiased Turkey Point meteorological data set used for dose analysis z/Q determination is acknowledged to contain imperfect data but can be made to be satisfactory for this application. The flaws are known and have been documented by as-left/as-found recorded data to be larger than RG 1.23 would normally permit without correction. Turkey Point has considered a number of means that could be used to correct the data and has carefully selected an appropriate means to do so. To eliminate the potential that the "correction" process might have introduced any amount of non-conservatism, the submitted AST dose analyses have used a conservatively selected composite set of unbiased and variable biased z/Q inputs and a reduced allowable control room in-leakage (115 to 100 cfm) and thus have conservatively determined the dose consequences for the proposed new AST based analysis of record.

Conservatisms in Meteorological Data Development:

" Full AT biases were applied for all intervals, even those within RG 1.23 allowable tolerances (correction of all data to zero error, instead of correction of only non-conforming data to be "just within" RG 1.23 allowable tolerance).

• Only AT values supported by valid individual temperature instrument readings were retained for use in determining stability class.

0 Consistent rules were applied in the selection of A- or B- Channel AT for stability class determination.

Conservatisms in Dose Analyses:

• Only biased X/Qs that were greater than the corresponding unbiased X/Qs were used in revised dose analyses.

• Allowable unfiltered inleakage was reduced to increase the margin to limit.

REFERENCES (1) M. Kiley (FPL) to U.S. Nuclear Regulatory Commission (L-2010-13 1), "Response to 5/28/2010 Request for Additional Information (RAI) Regarding Alternative Source Term (AST) License Amendment Request (LAR) 196 (TAC Nos. ME1624 and ME1625)," Accession No. ML101760019, June 23, 2010.

(2) M. Kiley (FPL) to U.S. Nuclear Regulatory Commission (L-2010-137), "Revised Radiological Dose Consequences for Alternative Source Term and Conforming License Amendment Request 196," Accession No. ML101800222, June 25, 2010.