L-PI-09-060, Supplemental Information Closing License Renewal Commitment Number 36 Regarding Application for Renewed Operation Licenses
| ML091190418 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 04/28/2009 |
| From: | Sorensen J Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-PI-09-060 | |
| Download: ML091190418 (9) | |
Text
@ Xcel Energym April 28, 2009 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 License Nos. DPR-42 and DPR-60 Su~plemental Information Closinq License Renewal Commitment Number 36 Reaardinq Application for Renewed Operatinq Licenses By letter dated April 11, 2008, Northern States Power Company, a Minnesota Corporation, (NSPM) submitted an Application for Renewed Operating Licenses (LRA) for the Prairie Island Nuclear Generating Plant (PINGP) Units 1 and 2. In a letter dated December 10, 2008, the NRC transmitted Request for Additional lnforrriation (RAI) 4.3.1.1 -1 regarding that application. The NSPM response to that RAI, in a letter dated January 9, 2009, included License Renewal Commitment Number 36 to complete additional analyses and amend the LRA to incorporate the analysis results by April 30, 2009. Enclosure 1 of this letter transmits the LRA amendment with the updated analysis results.
If there are any questions or if additional information is needed, please contact Mr. Eugene Eckholt, License Renewal Project Manager.
Summaw of Commitments This letter contains no new commitments or changes to existing commitments. This letter completes the actions required by PINGP License Renewal Commitment Number
- 36.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on April 28, 2009.
w o e 1 P. Sorensen Director Site Operations, Prairie Island Nuclear Generating Plant Units 1 and 2 Northern States Power Company - Minnesota 171 7 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1 121
Document Control Desk Page 2 Enclosure (1) cc:
Administrator, Region Ill, USNRC License Renewal Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC Prairie Island Indian Community ATTN: Phil Mahowald Minnesota Department of Commerce Supplemental Information Closing License Renewal Commitment Number 36 In a letter dated January 9, 2009, NSPM provided License Renewal Commitment Number 36 to amend the LRA to replace the results of fatigue analyses for two Reactor Coolant System locations using Fatiguepro stress-based fatigue methodology with the results of fatigue analyses using ASME Code Section Ill methodology. The commitment reads as follows:
NSPM will complete fatigue calculations for the pressurizer surge line hot leg nozzle and the charging nozzle using the methodology of the ASME: Code (Subsection NB) and will report the revised CUFs and CUFs adjusted for environmental effects at these locations as an amendment to the PINGP LRA.
Conforming changes to LRA Section 4.3.3, "PINGP EAF Results," will also be included in that amendment to reflect analysis results and remove references to stress-based fatigue monitoring.
ASME Code Section Ill (Subsection NB) fatigue analyses have been completed for the pressurizer surge line hot leg nozzle and the charging nozzle. The results of those analyses are being incorporated into the LRA by the following chisnges. This LRA amendment completes the actions required by License Renewal C:ommitment Number 36.
LRA Section 4.3.3, Environmentally-Assisted Fatigue (GSI-1 go), on Pages 4.3-1 9 through 4.3-24, is revised in its entirety to read as follows:
4.3.3 Environmentally-Assisted Fatigue (GSI-190)
Test data indicate that certain environmental effects (such as temperature and dissolved oxygen content) in the primary systems of ligh,t water reactors could result in greater susceptibility to fatigue than would be predicted by fatigue analyses based on the ASME Code Section Ill design fatigue curves.
The ASME design fatigue curves were based on laboratory tests in air and at low temperatures. Although the failure curves derived from laboratory tests were adjusted to account for effects such as data scatter, size effect, and surface finish, these adjustments may not be sufficient to account for actual plant operating environments.
As reported in SECY-95-245, the NRC coricluded that no immediate staff or licensee action was necessary to deal with the environmenta.lly-assisted fatigue (EAF) issue. In addition, the staff c;oncluded that it could not justify requiring a backfit of the environmental fatigue data to operating plants.
However, the NRC also concluded that, because metal fatigue effects increase with service life, environmentally-assisted fatigue stiould be evaluated for any proposed extended period of operation for License Renewal.
NUREGICR-6260 applied the fatigue design curves that incolrporated environmental effects to several plants and identified locatioris of interest for consideration of environmental effects. Section 5.5 of NUREIGICR-6260 Supplemental Information Closing License Renewal Commitment Number 36 identified selected component locations to evaluate in older vintage Westinghouse plants, such as PINGP. The corresponding PHNGP locations are as follows:
- 1. Reactor vessel shell to lower head
- 2. Reactor vessel inlet and outlet nozzles
- 3. Pressurizer surge line hot leg nozzle
- 4. RCS piping charging system nozzle
- 5. RCS piping safety injection accumulator nozzle
- 6. RHR Class 1 piping tee Determination of Fatique Usaqe Unadiusted for Environmental Effects For the NUREGICR-6260 locations listed above, design basis cumulative usage factors (CUFs) are reported in Section 4.3.1.I for the reactor vessel shell to lower head and the reactor vessel inlet and outlet nozzles. The design basis CUFs for these locations are repeated in the Unadjusted CUF column of Table 4.3-8.
CUFs generated in response to NRC Bulletin 88-1 1 are repo~rted in Section 4.3.1.6 for the pressurizer surge line piping (including the hot leg surge nozzles). The limiting pressurizer surge line location reported in NUREGICR-6260 is at the safe end connected to the hot leg nozzle. As cfiscussed below, the CUF for the PINGP surge line hot leg riozzle has been recalculated for the License Renewal determination of environmental effects.
The PINGP primary Class 1 piping NURE(;/CR-6260 locations are designed in accordance with 831.I
.O, and explicit fatigue analyses were not required.
To support License Renewal, fatigue usage has been calculated in accordance with Section Ill of the ASME Code, Subsection NB, for the safety injection accumulator nozzle, RHR Class 1 piping tee, charging system nozzle, and the pressurizer surge line connection to the hot leg nozzle.
The CUFs for the safety injection accumulator nozzle and the RHR Class 1 piping tee were calculated using ASME Code Section 111, 1989 Edition with 1989 Addenda. Transients defined for these locations include inadvertent RCS depressurization, inadvertent accumulator blowdown, RHR operation during plant cooldown, RCS refueling, high head safety injection, and OBE.
The resulting CUFs for the safety injection accumulator nozzle and RHR Class 1 piping tee are reported in the Unadjusted CUF colurrm of Table 4.3-8.
The CUFs for the charging system nozzles for Units 1 and 2 were calculated using ASME Code Section 111, 2001 Edition with 2003 Addenda. Transients defined for this location are based on the selection of bounding NSSS design transients defined in Table 4.3-1, and also include inadvertent RCS depressurization, inadvertent auxiliary spray actuation, excessive feedwater Supplemental lnforniation Closing License Renewal Commitment Number 36 flow, RCS refueling, and OBE. The numbers of transient cycles were modified to reflect the expected number of occurrences at 60 years. In addition, charginglletdown system flow sh~~toff and flow change transients were defined based on a standard set of Westinghouse design transients for auxiliary syste~ms, as modified for the expected number of occurrences at 60 years. The resulting CUFs for the charging system nozzles for Units 1 and 2 are reported in the Unadjusted CUF column of Table 4.3-8.
The CUF for the pressurizer surge line hot leg nozzle for Unils 1 and 2 was calculated usirig ASME Code Section 111, 2001 Edition with 2003 Addenda.
Transients defined for this location are based on the selectio~'l of bounding NSSS design transients defined in Table 4.3-1, and also include inadvertent RCS depressurization, inadvertent auxiliary spray actuation, (control rod drop, excessive feetlwater flow, RCS refueling, and OBE. The numbers of transient cycles were modified to reflect the expected number of occurrences at 60 years. Pressurizer insurgeloutsurge transients before the implementation of modified operating procedures (MOP) are derived from WCAP-12839. The pressurizer insurgeloutsurge transients that represent the time after implementation of MOP are based on WCAP-14950. The resulting CUF for the pressurizer surge line hot leg nozzle for Units 1 and 2 is reported in the Unadjusted ClJF column of Table 4.3-8.
Determination of Environmentallv-Assisted Fatique Usaye PINGP evaluated the NUREGICR-6260 locations using the guidance provided in NLJREG-1801. NUREG-1 801 calls for using the guidance (formulas) provided in NUREGICR-5704 for austenitic stainless steel and NUREGICR-6583 for carbon steel and low-alloy steel to calculate environmentally-assisted fatigue correctiorl factors (Fen). The correction factors are applied to the unadjusted CUFs reported in Table 4.3-8 to obtain CUFs adjusted for environmental effects.
Carbon Steel For PINGP, none of the locations identified in NUREGICR-6260 are made of carbon steel, so calculation of the Fen for carbon steel is not required.
Low Alloy Sttsel The environmentally-assisted fatigue correction factor (Fen) for low alloy steel is calculated als follows:
Fen = exp(0.929 - 0.001 24T - 0.101 S*T*O*C*), where:
Fen = fat~igue life correction factor T
= fluid service temperature of transient, "C (Note: In 'I-0.00124T" expression only, T is taken as room temperature, 25°C)
Supplemental lnforniation Closing License Renewal Commitment Number 36 S*
= S for 0 c sulfur content, S 50.015 wt. O h
= 0.015 for S > 0.01 5 wt. %
T*
= 0 for T c 150°C
= (T-150) for 150 "C5T5350°C O*
= 0 for dissolved oxygen, DO c 0.05 parts per million (pprn)
= ln(D010.04) for 0.05 pprn 5 DO 5 0.5 pprn
= ln('12.5) for DO > 0.5 pprn C*
=Oforstrainrate,C>l%lsec
= In(ri) for 0.001 I C I 1 %/sec
= ln(O.OO1) for C c 0.001 %/sec It is assumed ithat when the DO levels exceed 0.05 pprn when the RPV head is removed and reinstalled, the RCS temperature will stay below 150°C. As such, the increased DO levels during that process will not affect the Fen calculations. F:or a PWR environment, the DO is assumed to be below 0.05 pprn above 1 5#0°C and 0*=0.
Therefore, the Fen for low alloy steel is 2.4!55.
Austenitic Stiainless Steel The environmlentally-assisted fatigue correction factor (Fen) fior Types 304 and 31 6 austenitic stainless steel is calculated as follows:
Fen = exp(0.935 - T*C*O*), where:
Fen = fatiigue life correction factor T
= fluid service temperature of transient, "C T*
= 0 for T c 200°C
= 1 for T 2 200°C E *
= 0 for strain rate, C > 0.4%lsec
= In(i 10.4) for 0.0004 5 & 5 0.4°/o/sec
= ln(~D.000410.4) for C < 0.0004%/'sec O*
= 0.260 for dissolved oxygen, DO c 0.05 parts per million (pprn)
= 0.1 72 for DO 2 0.05 pprn Therefore, the Fen for Stainless Steel is:
Fen = 2.55 (T <:
200°C, any &, any DO)
Fen = 2.55 (T 2: 200°C, & I 0.4%Isecl any DO)
Fen = 3.78 (T L 200°C, & = 0.04%/sec, DO L 0.05 ppm)
Fen = 4.64 (T 2: 200°C, C = 0.04%/sec1 DO c 0.05 ppm)
Supplemental lnforniation Closing License Renewal Commitment Number 36 Fen = 5.62 (T I:
200°C, C = 0.004°/o/sec, DO 1 0.05 ppm)
Fen = 8.45 (T 2 200°C, C = 0.004%/sec1 DO c 0.05 ppm)
Fen = 8.36 (T I: 200°C, & I 0.0004%/sec1 DO 10.05 ppm)
Fen = 15.35 (T 2 200°C, & 5 0.0004°/o/sec, DO c 0.05 ppm)
PINGP Environrn~entallv-Assisted Fatique Results There are three lolw alloy steel NUREGICR-6260 locations at PINGP: RPV outlet nozzle, RPV inlet nozzle, and RPV shell to lower head. When the design CUFs at these locations are multiplied by an Fen of 2.455, the environmentally-adjusted CUFs are all below 1.O. The resulting adjusted values of CUF are reported in Table 4.3-8. The environmentally-adjusted CUFs of the RPV outlet nozzle, RPV inlet nozzle and RlPV shell to lower head have been projected to the end of the period of extendeld operation in accordance with 10 CFR 54.21 (c)(l)(ii). The cumulative numbers of design transients experienced by the locations of interest will continue to be managed using cycle counting under the Metal Fatigue of Reactor Coolant Pressure Boundary Program in accordance with 10 CFR 54.21 (c)(l)(iii).
The remaining NlJREGICR-6260 locations are all stainless steel.
Environmentally-adjusted CUFs for the safety injection accumulator nozzle and RHR Class 1 pipi~ig tee are below 1.O. The safety injection nozzle and RHR tee environmentally-aldjusted CUFs are based on ASME Code Section Ill analyses multiplied by a bounding Fen. The resulting adjusted values of CUF are reported in Table 4.3-8. The environmentally-adjusted CUFs for the safety injection nozzle and RHR tee havle been projected to the end d the period of extended operation in accordance with 10 CFR 54.21 (c)(l)(ii). The transients used ffor the fatigue evaluation will be added to the Metal Fatigue of Reactor Coolant Pressure Boundary Program, and EAF at these locations will be managed using cycle-based fatigue monitoring in accordance with 10 CFR 54.21 (c)(l)l(iii).
Environmentally-adjusted CUFs for the charging system nozzles are projected to be below 1.0 at 60 years. PINGP has calculated an unadjusted CUF at the charging nozzles for Units 1 and 2 at 60 years using the methodology of ASME Code Section Ill, Subsection NB. The unadjusted value of CUF that bounds both Units is 0.1024 for Unit 2. This value is the total CUF determined by summing the partial usage values calculated for each load set pair. Temperatures and stress values from the Unit 2 analysis, as well as a conservatively-assumed value for dissolved oxygen (DO), are used to determine an environmental fatigue correction factor (Fen) value for each load set pair using the Integrated Strain Rate approach provided in MRP-47, "Guidelines for Addressing Fatigue Environmental Effects in a License Renewal Application," Revision 1 (page 4-14).
Detailed Fen calci~lations are performed only for those load set pairs with a reasonably significant air curve fatigue contribution, specifically usage value 20.001. For all other load set pairs, the Fen is taken to be 15.35, which is the maximum value for a stainless steel material. Fen is then multiplied by the air curve usage to yield EAF usage for each load set pair. These partial EAF usage Supplemental lnforn~ation Closing License Renewal Commitment Number 36 factors are summed over all load set pairs to yield the total environmentally-adjusted CUF of 0.7431. This value of the environmentally-adjusted CUF is listed in Table 4.3-8. The environmentally-adjusted CUF for the charging system nozzle has been projected to the end of the period of extended operation in accordance with 10 CFR 54.21 (c)(l)(ii). The additional transients and revised cycle limits used in the fatigue evaluation will be added to the Metal Fatigue of Reactor Coolant F3ressure Boundary Program in conjunction with License Renewal Commitrnent No. 33, and environmentally-assisted fatigue at the charging nozzle \\rill be managed during the period of extended operation using cycle counting in i3ccordance with 10 CFR 54.21 (c)(l)(iii).
The pressurizer slurge line hot leg nozzle environmentally-adjusted CUF, using CUFs calculated in response to NRC Bulletin 88-1 1 (Section 4.3.1.6), would be greater than 1.O. However, as discussed above, PlNGP has recalculated fatigue usage at the pressurizer surge line hot leg nozzle at 60 years using the methodology of ASME Code Section Ill, Subsection NB. The re:sulting unadjusted value of CUF that bounds both Units is 0.0759. This value is the total CUF determined by summing the partial usage values calculatetl for each load set pair. Temperatures and stress values from that analysis, as well as a conservatively-assumed value for dissolved oxygen (DO), are used to determine an environmental fatigue correction factor (F,,,)
value for each load set pair using the Integrated Strain Rate approach provided in MRP-47, Revision 1 (page 4-14).
Detailed Fen calc~~lations are performed only for those load set pairs with a reasonably significant air curve fatigue contribution, specifically usage values 20.0015. For all other load set pairs, the Fen is taken to be 15.35, which is the maximum value for a stainless steel material. Fen is then multiplied by the air curve usage to yield EAF usage for each load set pair. These p'artial EAF usage factors are summed over all load set pairs to yield the total environmentally-adjusted CUF of 0.9854. This value of the environmentally-adjusted CUF is listed in Table 4.3-8. The environmentally-adjusted CUF for the surge line hot leg nozzle has been projected to the end of the period of extended operation in accordance with 10 CFR 54.21 (c)(l)(ii). The additional transien,ts and revised cycle limits used iin the fatigue evaluation will be added to the Metal Fatigue of Reactor Coolant 13ressure Boundary Program in conjunction with License Renewal Commitment No. 33, and environmentally-assisted fatigue at the pressurizer surge line hot leg nozzle will be managed during the period of extended operation using cycle counting in accordance with 10 CFR 54.21 (c)(l)(iii).
Supplemental Information Closing License Renewal Commitment Number 36 Table 4.3-8: Summary of EAF Results - Prairie Island Units 1 and 2 11 I
I I
I 11 RPV Outlet 1
ILow
- 'lay (
0.035 1
2.455 1
0.086 Nozzle Steel Component RPV Inlet 1
Nozzle 1 'LOwA"oy 1 0.0165 1
2.455 1
Steel RPV Shell to Low Alloy O.OO1 Steel 2.455 0.0027 Lower Head Pressurizer Stainless Surge Line Hot Steel 0.0759 12.99' 01.9854 Leg Nozzle safety Injection Stainless 0.0377 (U1) 5.35 0.579 (U1)
Accumulator Nozzle Steel 0.031 8 (U2) 0.488 (U2)
Material
- 1. The analysis determined an individual Fen for each load set pair using the Integrated Strain Rate approach of MRP-47, and did not apply a single value of Fen. The value shown in the table is an "effective" overall Fen multiplier which was back-calculated by dividing the total environmentally-adjusted CUF sum of the adjusted usage factors from each load set pair) by the total unadjusted CUF (sum of the unadjusted usage factors from each load set pair).
- 2. The Unit 2 charging nozzle fatigue analysis is considered bounding for both PlNGP Units. Therefore, the EAF evaluation for the Unit 1 and Unit 2 charging nozzles is based on the bounding Unit 2 analysis case.
Unadjusted CUF Fen Multiplier CUF Adjusted for Environmental Effects