L-MT-10-015, 10 CFR 50.55a Request No. 16: Alternative to Nozzle-to-Vessel Weld and Inner Radius Examinations
| ML100750660 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/12/2010 |
| From: | O'Connor T Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-MT-10-015 | |
| Download: ML100750660 (16) | |
Text
Monticello Nuclear Generating Plant Xcel~nergy 2807 W County Road 75 Monticello, MN 55362 March 12, 2010 L-MT-10-015 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22
Subject:
10 CFR 50.55a Request No. 16: Alternative to Nozzle-to-Vessel Weld and Inner Radius Examinations Pursuant to 10 CFR 50.55a, "Codes and standards," paragraph (a)(3)(i), Northern States Power Company - Minnesota (NSPM) requests U.S. Nuclear Regulatory Commission (NRC) authorization of an alternative to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components," (ASME Section Xl).
Specifically, NSPM requests NRC authorization to implement an alternative to ASME Section XI, Table IWB-2500-1, "Examination Category B-D, Full Penetration Welded Nozzles in Vessels - Inspection Program B," to allow reduced percentage requirements for nozzle-to-vessel weld and inner radius examinations at the Monticello Nuclear Generating Plant (MNGP). The requested alternative is consistent with ASME Code Case N-702, "Alternative Requirements for Boiling Water Reactor (BWR) Nozzle Inner Radius and Nozzle-to-Shell Welds." This request is in accordance with the technical basis provided in the Boiling Water Reactor Vessel and Internals Project (BWRVIP) report, BWRVIP-1 08: "BWR Vessel and Internals Project Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Blend Radii," which was approved by the NRC in a Safety Evaluation dated December 19, 2007.
As indicated within Section 7.0 of Enclosure 1, the NRC has authorized similar 10 CFR 50.55a requests for the Duane Arnold Energy Center; the Perry Nuclear Power Plant, Unit 1; Dresden Nuclear Power Station, Units 2 and 3; and the Clinton Power Station, Unit No.1.
NSPM is requesting this alternative for the remainder of the MNGP Fourth Ten-Year Inservice Inspection Interval scheduled to end on May 31, 2012.
The 10 CFR 50.55a request is described in Enclosure 1 to this letter.
Document Control Desk L-MT-10-015 Page 2 If you have any questions or require additional information, please contact Mr. Richard Loeffler at (763) 295-1247.
NSPM requests approval of this alternative by October 29, 2010, to support the determination of the inservice inspection resource requirements needed to support the March 2011 refueling outage.
Summary of Commitments This lettery poses no ne ommitments and does not revise any existing com m ary ofCo m im e t Ti othy J on nor Site Vice sident, Monticello Nuclear Generating Plant Northern S tes Power Company - Minnesota Enclosures (3) cc:
Administrator, Region III, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC Minnesota Department of Commerce
ENCLOSURE 1 MONTICELLO NUCLEAR GENERATING PLANT 10 CFR 50.55a REQUEST NO. 16 PROPOSED ALTERNATIVE IN ACCORDANCE WITH 10 CFR 50.55a(a)(3)(i)
WHICH PROVIDES AN ACCEPTABLE LEVEL OF QUALITY OR SAFETY ALTERNATIVE TO NOZZLE-TO-VESSEL WELD AND INNER RADIUS EXAMINATIONS
L-MT-10-015 Page 1 of 6 10 CFR 50.55a Request No. 16 Proposed Alternative In Accordance With 10 CFR 50.55a(a)(3)(i)
Which Provides an Acceptable Level of Quality or Safety Alternative to Nozzle-to-Vessel Weld and Inner Radius Examinations 1.0 ASME Code Component(s) Affected Code Class:
1 Component Numbers:
N2, N3, N5, N6 and N8 Nozzles (See Enclosure 2 for complete list of nozzle identifications.)
Examination Category:
B-D (Inspection Program B)
Item Number:
B3.90 and B3.100
==
Description:==
Alternative to ASME Section Xl, Table IWB-2500-1 (for the components described above) 2.0 Applicable ASME Code Edition and Addenda The Monticello Nuclear Generating Plant (MNGP) is currently in the fourth 10-year Inservice Inspection (ISI) Program interval and is committed to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," (ASME Section Xl), 1995 Edition through 1996 Addenda.
Additionally, for ultrasonic examinations, ASME Section Xl, Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems," of the 1995 Edition through 1996 Addenda is implemented, as required and modified by 10 CFR 50.55a.
3.0
Applicable Code Requirement
Table IWB-2500-1, "Examination Category B-D, Full Penetration Welded Nozzles in Vessels - Inspection Program B" Class 1 nozzle-to-vessel weld and nozzle inner radii examination requirements are delineated in Item Number B3.90, "Nozzle-to-Vessel Welds," and B3.100, "Nozzle Inside Radius Section." The required method of examination is
L-MT-10-015 Page 2 of 6 volumetric. All nozzles with full penetration welds to the vessel shell (or head) and integrally cast nozzles require examination each interval.
All of the nozzle assemblies identified in Enclosure 2 are full penetration welds to the vessel shell or head.
4.0 Reason for Request provides a complete listing of the applicable Reactor Pressure Vessel (RPV) nozzles.
The proposed alternative provides an acceptable level of quality and safety, and the reduction in inspection scope could result in a dose savings of as much as 10 Person-Rem for the unit over the remainder of the interval.
5.0 Proposed Alternative and Basis for Use In accordance with 10 CFR 50.55a(a)(3)(i), relief is requested from performing the required examinations on 100 percent of the nozzle assemblies identified in Table 5-1 below (see Enclosure 2 for complete list of RPV Nozzles). As an alternative for all welds and inner radii identified in Table 5-1, the NSPM proposes to examine a minimum of 25 percent of the MNGP nozzle-to-vessel welds and inner radius sections, including at least one nozzle from each system and nominal pipe size, in accordance with ASME Code Case N-702. For the nozzle assemblies identified in Enclosure 2, this would mean that examinations would be required for three of the Recirculation Inlet (N2) nozzles and one from each of the other nozzle groups, as identified below.
Table 5-1 MNGP Summary Nozzles Minimum Number Year(s)
Nozzle Group per Group Number to be Examined Examined Examined to Date Recirculation Inlet 10 3
6 Three in 2005 (N2)
Two in 2007 One in 2009 Main Steam 4
1 2
One in 2005 (N3)
One in 2009 Core Spray 2
1 1
One in 2005 (N5)
Closure Head 2
1 2
One in 2007 Spare (N6)
One in 2009 Jet Pump 2
1 2
One in 2005 Instrumentation (N8)
One in 2009
L-MT-10-015 Page 3 of 6 Therefore, upon authorization, no further nozzles in the applicable groups would remain to be inspected for the remainder of the interval.
ASME Code Case N-702 stipulates that a VT-1 examination may be used in lieu of the volumetric examination for the inner radii (i.e., Item No. B3.100, "Nozzle Inside Radius Section"). NSPM is only requesting to perform volumetric examinations of the applicable nozzle inner radius sections. NSPM is not requesting use of the VT-1 examination provisions included in the code case in lieu of performing volumetric examinations. The NSPM is not currently using ASME Code Case N-648-1 at the MNGP for the identified components for enhanced magnification visual examination and has no plans of using ASME Code Case N-648-1 on those components in the future.
Electric Power Research Institute (EPRI) Technical Report 1003557, "BWRVIP-108: Boiling Water Reactor Vessel and Internals Project Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Blend Radii," (Reference 1) provides the basis for ASME Code Case N-702. The evaluation found that failure probabilities at the nozzle blend radius region and nozzle-to-vessel shell weld due to a Low Temperature Overpressure event are very low (i.e., <1 x 10-6 for 40 years) with or without inservice inspection. The report concludes that inspection of 25 percent of each nozzle type is technically justified.
This EPRI report was approved by the NRC in a safety evaluation (SE) dated December 19, 2007 (Reference 2). Section 5.0, "Plant Specific Applicability," of the SE indicates that each licensee who plans to request relief from ASME Code, Section Xl requirements for RPV nozzle-to-vessel shell welds and nozzle inner radius sections may reference the BWRVIP-108 report as the technical basis for the use of ASME Code Case N-702 as an alternative. The NRC SE further states that each licensee should demonstrate the plant specific applicability criteria from the BWRVIP-108 report to its units in the relief request by showing that all the general and nozzle-specific criteria addressed below are satisfied (i.e., as described in Enclosure 3).
(1)
The maximum RPV heatup/cooldown rate is limited to less than 11 50F per hour.
MNGP Technical Specification (TS) 3.4.9,"RCS Pressure and Temperature (P/T) Limits," provides a limiting condition for operation (LCO). The heatup/cooldown rate is referenced in the MNGP operating procedures where applicable such as scrams and start-ups. The maximum heatup / cooldown rate of 100°F per hour is specified within the MNGP Updated Safety Analysis Report in Table 4.1-1, "Reactor Coolant System Data."
L-MT-10-015 Page 4 of 6 For the Recirculation Inlet Nozzles:
(2)
(pr/t) / CRPV < 1.15, where:
p = RPV normal operating pressure, r = RPV inner radius, t = RPV wall thickness, and CRPV = 19332 (i.e., 1000 psi x 110 inch / 5.69 inch, based on the BWRVIP-108 recirculation inlet nozzle / RPV finite element method (FEM) model);
(3)
[p(r0 2 + r, 2) / (r0 2 -
r, 2)] / CNOZZLE < 1.15, where:
p = RPV normal operating pressure, ro= nozzle outer radius, r= nozzle inner radius, and CNOZZLE = 1637 [i.e., 1000 psi x (13.988 2 + 6.875 2)/(13.988 2 6.875 2)1, based on the BWRVIP-108 recirculation inlet nozzle RPV FEM model];
For the Recirculation Outlet Nozzles:
(4)
(pr/t) / CRPV < 1.15, where:
p = RPV normal operating pressure, r = RPV inner radius, t = RPV wall thickness, and CRPV = 16171 (i.e., 1000 psi x 113.2 inch /7.0 inch, based on the BWRVIP-108 recirculation outlet nozzle / RPV FEM model);
(5)
[p(r0 2 + r, 2) / (r0 2 - r, 2)] / CNOZZLE < 1.15, where:
p = RPV normal operating pressure, ro= nozzle outer radius, ri= nozzle inner radius, and CNOZZLE = 1977 [i.e., 1000 psi x (22.31 2 + 12.78 2) / (22.31 2 -12.78 2)],
based on the BWRVIP-108 recirculation outlet nozzle / RPV FEM model].
Note that as stated in the NRC SE, only the recirculation inlet and outlet nozzles need to be checked because the conditional probabilities of failure, P(FIE)s, for the other nozzles are an order of magnitude lower.
L-MT-10-015 Page 5 of 6 Based upon the above information, all requested MNGP RPV nozzle-to-vessel shell full penetration welds and nozzle inner radii sections, with the exception of the Recirculation Outlet Nozzles, meet the general and nozzle-specific criteria in BWRVI P-108.
Therefore, ASME Code Case N-702 is applicable. Use of ASME Code Case N-702 provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i) for all requested RPV nozzle-to-vessel shell full penetration welds and nozzle inner radii sections, with the exception of the recirculation outlet nozzles.
6.0 Duration of Proposed Alternative The proposed alternative will be applied for the remainder of the fourth 10-year interval of the MNGP ISI Program.
7.0 Precedent The NRC has approved similar requests to adopt an alternative to the ASME Section XI, Table IWB-2500-1 criteria to allow reduced percentage requirements for nozzle-to-vessel weld and inner radius examinations for the Duane Arnold Energy Center (Reference 3), Perry Nuclear Power Plant, Unit 1 (Reference 4);
the Dresden Nuclear Power Station, Units 2 and 3 (Reference 5), and the Clinton Power Station, Unit No.1 (Reference 6).
L-MT-10-015 Page 6 of 6 8.0 References
- 1.
BWRVIP to NRC letter submitting EPRI report, "BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radius (BWRVIP-1 08)," dated November 25, 2002, as supplemented by letters dated July 25, 2006, September 13, 2007, and November 21, 2007.
- 2.
NRC letter to BWRVIP Chairman (R. Libra), "BWRVIP Safety Evaluation of Proprietary EPRI Report, "BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radius (BWRVIP-1 08)," dated December 19, 2007. (ADAMS Accession No. ML073600374)
- 3.
NRC letter, "Duane Arnold Energy Center - Safety Evaluation for Request for Alternative to Reactor Pressure Vessel Nozzle to Vessel Weld and Inner Radius Examinations (TAC No. MD8193)," dated August 29, 2008. (ADAMS Accession No. ML082040046)
- 4.
NRC letter, "Perry Nuclear Power Plant, Unit No.1 -Request for Relief Related to Inservice Inspection Relief Request IR-054 (TAC No. MD8458)," dated December 29, 2008. (ADAMS Accession No. ML082960729)
- 5.
NRC letter, "Dresden Nuclear Power Station, Units 2 and 3 - Alternative to Nozzle-to-Vessel Weld and Inner Radius Examinations (TAC Nos. ME0882 and ME0883)," dated November 3, 2009. (ADAMS Package Accession No. ML092940436)
- 6.
NRC letter, "Clinton Power Station, Unit No.1 -
Proposed Alternative to 10 CFR 50.55a Examination Requirements for Reactor Pressure Vessel Weld Inspections (TAC No. ME0218)," dated August 24, 2009. (ADAMS Accession No. ML092300394)
ENCLOSURE 2 MONTICELLO NUCLEAR GENERATING PLANT 10 CFR 50.55a REQUEST NO. 16 PROPOSED ALTERNATIVE IN ACCORDANCE WITH 10 CFR 50.55a(a)(3)(i)
WHICH PROVIDES AN ACCEPTABLE LEVEL OF QUALITY OR SAFETY ALTERNATIVE TO NOZZLE-TO-VESSEL WELD AND INNER RADIUS EXAMINATIONS TABLE OF ASME COMPONENTS AFFECTED
L-MT-10-015 Page 1 of 3 Table of ASME Components Affected Nominal Nozzle IDNoia Cate-gory Item Pipe Exam Year Nozzle-to-Vessel (NV)
Number Number System Size Inner Radius (IR)
(Inches)
(PDI)
N-2A (NV)
B-D B3.90 Recirculation 12 2009 (inlet)
N-2A (IR)
B-D B3.100 Recirculation 12 2009 (Inlet)
N-2B (NV)
B-D B3.90 Recirculation 12 2007 (inlet)
N-2B (IR)
B-D B3.100 Recirculation 12 2007 (inlet)
N-2C (NV)
B-D B3.90 Recirculation 12 (Inlet)
N-2C (IR)
B-D B3.1 00 Recirculation 12 (Inlet)
N-21D (NV)
B-D B3.90 Recirculation 12 2005 (Inlet)
N-21D (IR)
B-D B3.1 00 Recirculation 12 2005 (Inlet)
N-2E (NV)
B-D B3.90 Recirculation 12 2005 (Inlet)
N-2E (IR)
B-D B3.1 00 Recirculation 12 2005 (Inlet)
Recirculation N-2F (NV)
B-D B3.90 (Inlet) 12 N-2F (IR)
B-D B3.1 00 Recirculation 12 (Inlet)
N-2G (NV)
B-D B3.90 Recirculation 12 2007 (Inlet)
N-2G (IR)
B-D B3.1 00 Recirculation 12 2007 (Inlet)
L-MT-10-015 Page 2 of 3 Table of ASME Components Affected Nozzle ID Nominal Cateqory Item Pipe Exam Year Nozzle-to-Vessel (NV)
Number Number System Size Inner Radius (IR)
(Inches)
(PDI)
N-2H-1 (NV)
B-D B3.90 Recirculation 12 (Inlet)
N-2H (IR)
B-D B3. 100 Recirculation 12 (Inlet)
N-2J1 (NV)
B-D B3.90 Recirculation 12 2005 (Inlet)
N-2J1 (IR)
B-D B3.1 00 Recirculation 12 2005 (Inlet)
N-21K (NV)
B-D B3.90 Recirculation 12 (Inlet)
N-2K (IR)
B-D B3.1 00 Recirculation 12 (Inlet)
N-3A (NV)
B-D B3.90 Main Steam 18 2005 N-3A (IR)
B-D B3.100 Main Steam 18 2005 N-3B (NV)
B-D B3.90 Main Steam 18 N-3B (IR)
B-D B3.100 Main Steam 18 N-3C (NV)
B-D B3.90 Main Steam 18 2009 N-3C (IR)
B-D B3.100 Main Steam 18 2009 N-3D (NV)
B-D B3.90 Main Steam 18 N-3D (IR)
B-D B3.100 Main Steam 18 N-5A (NV)
B-D B3.90 Core Spray 8
N-5A (IR)
B-D B3.100 Core Spray 8
N-5B (NV)
B-D B3.90 Core Spray 8
2005 N-5B (IR)
B-D B3.100 Core Spray 6
.2005
L-MT-10-015 Page 3 of 3 Table of ASME Components Affected Nozzle ID Nominal Cate.gory Item Pipe Exam Year Nozzle-to-Vessel (NV)
Number Number System Size Inner Radius (IR)
(Inches)
P-I N-6A (NV)
B-D B3.90 Closure Head 6
2007 Spare N-6A (IR)
B-D B3.1 00 Closure Head 6
2007 Spare N-6B3 (NV)
B-D B3.90 Closure Head 6
2009 Spare N-6B3 (IR)
B-D B3.1 00 Closure Head 6
2009 Spare Jet Pump N-8A (NV)
B-D B3.90 Instrumentation 4
2005 Jet Pump N-8A (IR)
B-D B3.100 Instrumentation 4
2005 Jet Pump N-81 (NV)
B-D B3.90 Instrumentation 4
2009 Jet Pump N-8B (IR)
B-D B3.100 Instrumentation 4
2009
ENCLOSURE 3 MONTICELLO NUCLEAR GENERATING PLANT 10 CFR 50.55a REQUEST NO. 16 PROPOSED ALTERNATIVE IN ACCORDANCE WITH 10 CFR 50.55a(a)(3)(i)
WHICH PROVIDES AN ACCEPTABLE LEVEL OF QUALITY OR SAFETY ALTERNATIVE TO NOZZLE-TO-VESSEL WELD AND INNER RADIUS EXAMINATIONS VERIFICATION OF PLANT SPECIFIC NOZZLE APPLICABILITY TO APPLY CODE CASE N-702 IN ACCORDANCE WITH BWRVIP-108
L-MT-10-015 Verification of Plant Specific Nozzle Applicability to Apply Code Case N-702 to the MNGP in Accordance With BWRVIP-108 (Criteria 1)
Maximum RPV heatup/cooldown rate limited to less than 1 150F per hour.
The Monticello Updated Safety Analysis Report indicates a maximum heatup/cooldown rate of 100°F per hour. This heatup/cooldown rate is referenced in the MNGP operating procedures, where applicable, such as scrams and start-ups.
MNGP Technical Specification 3.4.9,"RCS Pressure and Temperature (P/T)
Limits," provides a limiting condition for operation (LCO).
Values for Monticello Recirculation Inlet and Outlet Nozzles:
Monticello specific values:
p = RPV normal operating pressure = 1025 psig r
RPV inner radius = 102.5 inches t = RPV wall thickness = 5.0625 inches ro = Recirculation inlet nozzle outer radius = 14.1875 inches ri= Recirculation inlet nozzle inner radius = 7.0625 inches r= Recirculation outlet nozzle outer radius = 24.375 inches r= Recirculation outlet nozzle inner radius = 13.0625 inches BWRVIP-108 Constants:
CRPV (Recirculation Inlet Nozzles) = 19332 CNOZZLE (Recirculation Inlet Nozzles) = 1637 CRPV (Recirculation Outlet Nozzles) = 16171 CNOZZLE (Recirculation Outlet Nozzles) = 1977 For the Recirculation Inlet Nozzles:
(Criteria 2)
(pr/t) / CRPV < 1.15
[(1025 x 102.5) / 5.0625] / 19332 =1.07351 < 1.15 (Criteria 3)
[p(r0 2 + r, 2) / (ro 2 _ ri 2)] / CNOZZLE < 1.15
[1025 (14.1875 2 +7.0625 2) / (14.1875 2 -7.0625 2)]
1637 =1.03870 < 1.15 For the Recirculation Outlet Nozzles:
(Criteria 4)
(pr/t) / CRPV < 1.15
[(1025 x 102.5) / 5.0625] / 16171 = 1.28335 > 1.15 (does not pass)
(Criteria 5)
[p(r0 2 + ri 2) / (r0 2 -
ri 2)] I CNOZZLE < 1.15
[1025 (24.375 2 + 13.0625 2) /(24.375 2 - 13.0625 2)] / 1977 = 0.93623 < 1.15
QF-0212, Revision 4 (FP-SC-RSI-04)
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