ML080160124

Summary of the Impact to License Renewal Application Severe Accident Mitigation Alternatives Analysis Due to Computer Program Errors

ML080160124
Person / Time
Site:	Wolf Creek
Issue date:	01/08/2008
From:	Garrett T Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ET 08-0001
Download: ML080160124 (8)

Text

W0LF CREEK rNUCLEAR OPERATING CORPORATION Terry J. Garrett January 8, 2008 Vice President, Engineering ET 08-0001 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Reference:

Letter ET 06-0038, dated September 27, 2006, from T.J. Garrett, WCNOC, to USNRC

Subject:

Docket No. 50-482: Summary of the Impact to Wolf Creek Generating Station License Renewal Application Severe Accident Mitigation Alternatives Analysis due to Computer Program Errors Gentlemen:

The reference provided Wolf Creek Nuclear Operating Corporation's (WCNOC) License Renewal Application (LRA) for the Wolf Creek Generating Station (WCGS). Three problems with a computer program used to generate some portions of the Severe Accident Mitigation Alternatives (SAMA) analysis have been discovered that have impacted the WCGS SAMA analysis report. The WCGS SAMA analysis is Attachment F, "Severe Accident Mitigation Alternatives Analysis," to LRA Appendix .E, "Applicant's Environmental Report Operating License Stage." The Wolf Creek severe accident baseline cost and dose risk were calculated using the MELCOR ACCIDENT CONSEQUENCE CODE SYSTEM (MACCS2) code. The Sector Population, Land Fraction, and Economic Estimation Program (SECPOP2000) code served as.an ancillary code for the analysis.

Three problems related to the use of the SECPOP2000 code have recently been identified and publicized throughout the industry.All three SECPOP2000 problems have been corrected and new MACCS2 results calculated.

The WCGS SAMA analysis was reanalyzed using the corrected SECPOP, input. The attachment to this letter provides an analysis and summary. of the impact of the re-analysis to conclusions reached in Attachment F of LRA Appendix E.P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HCNET ET 08-0001 Page 2 of 3 No commitments are identified in this submittal.

If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr. Richard Flannigan at (620) 364-4117.Terry J. Garrett TJG/rlt Attachment

-Revisions to WCGS SAMA Analysis cc: E. E. Collins (NRC), w/a V. G. Gaddy (NRC), w/a B. K. Singal (NRC), w/a T. Tran (NRC), w/a Senior Resident Inspector (NRC), w/a ET 08-0001 Page 3 of 3 STATE OF KANSAS)) s COUNTY OF COFFEY )Terry J. Garrett, of lawful age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the contents thereof; that he has executed the same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and'correct to the best of his knowledge, information and belief.By_TerryJ arrett Vice President Engineering SUBSCRIBED and sworn to before me this zday of j o. r ,2008.ý: A'ý4111 Notary qblic ALU::" ty"d GAYLE SHEPHEARD1 Notary Public -State of Kansas My Appt. Expires 7."/.o-j I Expiration Date'I]-ýq- I IA(b Attachment to ET 08-0001 Page 1 of 5 Attachment Summary to the Impact to Wolf Creek Generating Station (WCGS) Severe Accident Mitigation Alternatives (SAMA) Analysis Resulting from Corrections to the Sector Population, Land Fraction, and Economic Estimation (SECPOP) Code Attachment to ET 08-0001 Page 2 of 5 The Wolf Creek Generating Station (WCGS) severe accident baseline cost and dose risk were calculated using the MELCOR ACCIDENT CONSEQUENCE CODE SYSTEM (MACCS2) code.The Sector Population, Land Fraction, and Economic Estimation Program (SECPOP2000) code served as an ancillary code for the analysis; output from SECPOP2000 was used to specify year 2000 residential population distribution and agricultural (e.g., fraction of land used in farming, farm sales) and economic (e.g., farm land' roperty value, non-farm property value)parameters for the 50-mile area surrounding the site. Values for those parameters are used in the MACCS2 consequence calculations, which are combined with accident probabilities to produce the risks.Three problems related to the use of the SECPOP2000 code have recently been identified and publicized throughout the industry.

Problems identified are: (1) a formatting error in the regional economic data block text file generated by SECPOP2000 for input to MACCS2, which results in MACCS2 misreading the data, (2) an error associated with the formatting of the COUNTY97.DAT economic database file used by SECPOP2000, which results in SECPOP2000 processing incorrect economic and land use data (i.e., missing entries in the"Notes" column result in data being output for the wrong county), and (3) gaps in the numbered entries in the COUNTY97.DAT economic database file which result in any county beyond county number 955 being handled incorrectly in SECPOP2000.

All of these problems affect the agricultural and economic parameters input to MACCS2 for WCGS. None of these problems affect the population distribution specification.

All three SECPOP2000 problems have been corrected and new MACCS2 results calculated.

Table 1 shows the original and corrected total baseline dose and cost risk.Table 1. Baseline Risks for Wolf Creek SAMA as Affected by SECPOP2000 Errors Dose Risk Cost Risk (person-rem/Ryr)

($/Ryr)Results from the License Renewal 2.86 $1,974 Application Results from Corrected 3.27 $2,975 SECPOP2000 The corrections to the SECPOP2000 input to the MACCS analysis impacted the conditional dose and economic costs associated with each of the accident scenarios considered in the WCGS SAMA analysis.

Table 2 shows the baseline risks by release category.

U- B>Attachment to ET 08-0001 Page 3 of 5 Table 2. MACCS2 Revision 3 Results for Wolf Creek by Release Category Population Dose- Total Economic Cost-Release Annual Risk Risk Category Frequency 0-50 miles 0-50 miles (person-rem/yr)

($/yr)Leakage/No Cfail 2.80 x 10°" 0.232 2 Late Cfail 1.13 x 10-06 0.10 6 SGTR 1.65 x 10-07 0.05 98 ISLOCA 1.92 x 10-06 2.71 2,534 Cont Iso 3.42 x 10.09 0.0 2 Early Cfail 4.48 x 10-07 0.18 333 TOTAL 3.17 x 1005 3.27$2,975 The WCGS modified Maximum Averted Cost Risk (MACR), which accounts for external events, has been recalculated to determine the potential impact on the SAMA analysis.

The modified MACR based on the mean Probabilistic Risk Assessment (PRA) results increased from the Environmental Report (ER) submittal value of $1,852,000 to $1,908,000 (3.0 percent increase).

The 95th percentile PRA results sensitivity case was also recalculated and it was determined that the modified MACR increased from the ER submittal value of $3,518,800 to $3,625,200 (also a 3.0 percent increase).

The changes to the modified MACR estimates did not impact the analysis.In addition to the impact on the modified MACR, the SECPOP2000 errors also impacted the averted cost-risks that were calculated for each of the SAMAs. Table 3 provides a summary of the impact of using the corrected results in conjunction with the mean PRA results in the detailed cost-benefit calculations that were performed.

Attachment to ET 08-0001 Page 4 of 5 Table 3. Results Summary after Correction of SECPOP2000 Errors I Through 3 (Mean PRA Results)Averted Net Value Averted Change in Cost of Cost-Risk NEt Aoete Net Value Cost SAMA ID Implementation (ER (ER Cost- Risk (Corrected)

Effectiveness Submittal)

Submittal) (Corrected)?

SAMA 1 $800,000 $799,882 -$118 $808,634 $8,634 Yes SAMA 2 $400,000 $655,712 $255,712 $664,346 $264,346 No SAMA 3 $328,000 $293,252 -$34,748 $296,952 -$31,048 No SAMA 4 -$600,000 $243,368 -$356,632

$271,464 -$328,536 No Case 1 SAMA 4- $50,000 $173,050 $123,050 $193,114 $143,114 No Case 2 SAMA 5 $50,000 $54,576 $4,576 $56,502 $6,502 No SAMA 8 $565,000 $43,492 -$521,508

$44,094 -$520,906 No SAMA 13 $150,000 $111,168 -$38,832 $112,038 -$37,962 No SAMA 14 $1,200,000

$882,152 -$317,848

$892,196 -$307,804 No SAMA 15- .$3,250,000

$404,219 -$2,845,781

$416,442 -$2,833,558 No Case 1 SAMA 15 $1,000,000

$404,219 -$595,781

$416,442 -$583,558 No Case 2 SAMA 16 $565,000 $22,648 -$542,352

$23,372 -$541,628 No SAMA 17 $550,000 $65,328 -$484,672

$66,592 -$483,408 No Attachment to ET 08-0001 Page 5 of 5 As demonstrated in Table 3, the SECPOP2000 corrections had a minimal impact on the averted cost-risk estimates and only one SAMA (SAMA 1) that was originally classified as "not cost beneficial" was re-classified as "cost beneficial" based on the use of the corrected SECPOP2000 results. Given that SAMA 1 was identified as potentially cost beneficial in the original 95th percentile PRA results sensitivity analysis that was performed in the ER submittal, this change did not result in the identification of any new potentially cost beneficial SAMAs.In addition to the review of the mean PRA results quantifications, it was necessary to examine how the 95th percentile PRA results quantifications were impacted given that they were also used to identify potentially cost beneficial SAMAs. Table 4 provides a summary of the cost benefit calculations using the corrected SECPOP2000 results in conjunction with the 95th percentile PRA results. In this case, no SAMAs were identified as potentially cost beneficial that were not already identified in the ER submittal.

Table 4. Results Summary after Correction of SECPOP2000 Errors I Through 3 (95th Percentile PRA Results)Cost of Averted Net Value Averted Net Value Change in SAMA ID Costiof Cost-Risk (ER Cost- Risk (Corrected)

Cost Implementation (ER Submittal)

Submittal) (Corrected)

Effectiveness?

SAMA 1 $800,000 $1,519,776

$719,776 $1,536,405

$736,405 No SAMA 2 $400,000 $1,245,853

$845,853 $1,262,257

$862,257 No SAMA 3 $328,000 $557,179 $229,179 $564,209 $236,209 No SAMA 4 $600,000 No Case 1 $462,399 -$137,601

$515,782 -$84,218 SAMA4- $50,000 No Case 2 $328,795 $278,795 $366,917 $316,917 SAMA 5 $50,000 $103,694 $53,694 $107,354 $57,354 No SAMA 8 $565,000 $82,635 -$482,365

$83,779 -$481,221 No SAMA 13 $150,000 $211,219 $61,219 $212,872 $62,872 No SAMA 14 $1,200,000

$1,676,089

$476,089 $1,695,172

$495,172 No SAMA 15 $768,017 -$2,481,983

$791,240 -$2,458,760 No Case 1 $3,20,00 No SAMA 15- $1,000,000 No Case 2 $768,017 -$231,983

$791,240 -$208,760 SAMA 16 $565,000 $43,031 -$521,969

$44,407 -$520,593 No SAMA 17 $550,000 $124,123 -$425,877

$126,525 -$423,475 No