ML18153D164
| ML18153D164 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 12/31/1991 |
| From: | Witt F WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML18153D163 | List: |
| References | |
| WCAP-13127, NUDOCS 9211040198 | |
| Download: ML18153D164 (17) | |
Text
A DEMONS1RATION OF COMPLIANCE OF THE PRIMARY LOOP PUMP CASINGS OF THE SURRY UNITS 1 AND 2 TO ASME CODE CASE N-481 DECEMBER 1991
TABLE OF CONTENTS Section Title Page List of Tables 11 List of Figures iii
1.0 BACKGROUND
AND INTRODUCTION 1-1 1.1 Background 1-1 1.2 Introduction 1-2
2.0 DESCRIPTION
OF THE PRIMARY LOOP PUMP 2-1 CASINGS OF SURRY UNITS 1 AND 2 3.0 FRACTURE TOUGHNESS CRITERIA FOR THE PUMP 3-1 CASINGS 4.0 LOADS ON THE PUMP CASING NOZZLES 4-1 5.0 STABILITY EVALUATIONS 5-1 6.0 DISCUSSION AND CONCLUSIONS 6-1
7.0 REFERENCES
7-1 APPENDIX A A-1
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LIST OF TABLES Table Title Page 4-1 Comparison of the Faulted Loads for the Pump Casing Nozzles of Surry Units 1 and 2 with the Level A Faulted Screening Loads 4-3 4-2 Comparison of the Normal Loads for the Pump Casing Nozzles of Surry Units 1 and 2 with the Screening Level C Normal Loads 4-3 WPF0938J /120591:10 11
- Figure Title LIST OF FIGURES Page 2-1 Dimensional Sketches of the Model 93A Pump Casing with the Weld Seam Identified 2-2 2-2 A Model 93A Pump Casing Ready for Shipment 2-3 I
WPF0938J /120591:10 111
I
1.1 BACKGROUND
1.0 BACKGROUND
AND INTRODUCTION Periodic volumetric inspections of the welds of the primary loop pump casings of commercial nuclear power plants are required by Section XI of the ASME Boiler and Pressure Vessel Code (see Table IWB-2500-1, Examination Categories). These inspections are quite costly in terms of both dollars and radiation exposure (man-rem).
To perform a volumetric inspection, complete disassembly of the pump is required. A lowering of the primary coolant water level most likely would be necessary which would, in turn, necessitate a complete core unload. Even then the volu~etric inspection is very difficult. Since the pump casings are rigidly inspected prior to placing in service and no significant mechanisms exist for crack initiation and propagation, in-service volumetric inspection may be counter-productive. In recognition of this the ASME Code body approved a code case which provides an alternative to the volumetric inspection requirement (Reference la). The ASME Code Case is N-481: Alternate Examination Requirements for Cast Austenitic Pump Casings. It allows the replacement of volumetric examinations of primary loop pump casings with fracture mechanics based integrity evaluations (Item (d) of the code case) supplemented by specific visual inspections. It also requires that a ~eport of the evaluation be submitted to the regulatory and enforcement authorities having jurisdiction at the plant site for review (Item (e) of the code case). A copy of the code case is given in Appendix A Following approval of Case N-481 by the ASME the Westinghouse Owners Group sponsored the required analyses which are applicable to the various primary loop pump casing models found in Westinghouse design nuclear steam supply systems. Specifically, stress analyses using enveloping loads were performed for Westinghouse design primary
- loop pump casings as were fracture mechanics analyses for postulated flaws. Compliance to Item (d) of ASME Code Case N-481 was demonstrated on a generic basis. This work
- is documented in WCAP-13045 (Reference 2).
a See Section 7.0 for a listing of references.
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Since there is a variety of pump casing models, loads and materials as discussed in WCAP-13045, it was not feasible to qualify each plant of Westinghouse design specifically. Rather, enveloping or bounding criteria were set up whereby a specific utility, in most cases, needs only to show that the pump casings of interest fall under the umbrella established by the analyses. It is anticipated that most pump casings, perhaps all, can be easily qualified by showing they meet the required criteria.
WCAP-13045 was submitted to the Nuclear Regulatory Commission for review and approval as a reference topical report in October 1991. Approval has not been obtained as of the date of this report.
1.2 INTRODUCTION
It is the objective of this report to qualify the primary loop pump casings of the Surry Units 1 and 2 nuclear power plants to Item (d) of ASME Code Case N-481 (Reference 1). When this report is supplemented by the visual inspections specified in the code case and approved by the regulatory authority, compliance will be accomplished.
The pump casings of the Surry Units 1 and 2 nuclear power plant are described and the associated fracture toughness criteria, taking into account thermal aging, are discussed.
Loads on the pump casing nozzles are identified. Finally, compliance with Item (d) of ASME Code Case N-481 is verified by direct con:iparison with information presented in WCAP-13045.
The contents of this report are non-proprietary. To accomplish this, information is discussed and conclusions are drawn by examining WCAP-13045 without compromising proprietary etiquette.
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FIGURE 2-1 DIMENSIONAL SKETCHES OF TIIE MODEL 93A PUMP
- CASING WITH THE WELD SEAM IDENTIFIED WPF'()C)37J /120591:10 2-2
2.0 DESCRIPTION
OF THE PRIMARY LOOP PUMP CASINGS OF SURRY UNITS 1 AND 2 The primary loop pump casings of Surry Units 1 and 2 are of the Westinghouse Model 93A design. The pump casings are fabricated from SA351 CFS cast stainless steel. Each pump casing consists of two castings welded together as shown in Figure 2-1.
Dimensions are given and the weld location is indicated. A picture of a Model 93A pump casing ready for shipment is shown in Figure 2-2.
The chemistry and fracture toughnesses of the pump casing parts are given in Table A-2, pages A-51 (Surry Unit 2) and A-52 (Surry Unit 1) of WCAP-13045 .
I I
- I I
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FIGURE 2-2 A MODEL 93A PUMP CASING READY FOR SHIPMENT
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3.0 FRACTURE TOUGHNESS CRITERIA FOR THE PUMP CASINGS Lower bound end-of-service life fracture toughness criteria for Model 93A pump casings are found in Table 5-1 of WCAP-13045 (page 5-4). The Model 93A pump casings fall under the "All Remaining Pump Casings" grouping. Bounding values for J1c, Tmat, and Jmax are given. As noted in Section 11.3 of WCAP-13045 a value of 3000 in-lb/in2 is also acceptable as the bounding criterion for Jmax*
~*
WPF0938J /120591:10 3-1 t,'.\
~ = = = ~ ~ = = ~ ~ - - - - - - - - - - - - - - -- - -- - - - - ~ - -
- 4.0 LOADS ON THE PUMP CASING NOZZLES In WCAP-13045 enveloping axial force and moment loadings on the inlet and outlet pump casing nozzles were applied in the three-dimensional finite element analyses of the Model 93A pump casing. In this section the faulted nozzles loads (i.e., the normal plus safe shutdown earthquake nozzle loads) for the Surry Units 1 and 2 pump casings are compared with the enveloping faulted loads. The normal loads are compared with screening normal loads for evaluating the loss-of-load upset condition.
For faulted conditions the axial force, F, is taken as the absolute sum of the axial forces of the individual loading components. For the purpose at hand, the x-direction is taken as the axial direction of the piping welded to the nozzle with y and z designating the remaining orthogonal coordinates. The bending moment at the nozzle of interest is calculated by:
M = (M/ + M/)°5 where My is the absolute sum of the bending moments in the y-direction for the various individual loading compo~ents. Similarly ~ is the absolute sum for the Z"-direction. The individual loading components are pressure, deadweight, normal thermal expansion, safe shutdown earthquake with inertial forces and safe shutdown earthquake with anchor motion. The absolute sum method is also applied in determining normal loads.
The faulted loads determined as above are compared in Table 4-1 to the Level A screening loads as defined in WCAP-13045 (see Table 6-2). The slight difference in temperature is of no consequence considering the load margins. The Surry Units 1 and 2 nozzle loads are seen to be bounded by Level A loads.
lG Table 4-2 the normal operating loads obtained as above for Surry Units 1 and 2 are compared with the Level C screening nozzle loads (see Table 6-2 of WCAP-13045)
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which were used for evaluating the loss-of-load upset condition. The Surry Units 1 and 2 normal loads are bounded by the Level C loads.
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TABLE 4-1 COMPARISON OF THE FAULTED LOADS FOR THE PUMP CASING NOZZLES OF SURRY UNITS 1 AND 2 WITH THE LEVEL A FAULTED SCREENING LOADS Inlet Nozzle Outlet Nozzle Load Pressure Ten1)erature Force 8 Moment Force8 Moment (psig) (Of) (kips) Cin-kips) (kips) (in-kips)
Surry Units 1 and 2 2235 557 1894 17259 1409 7692 Level A 2300 550 2000 40000 1800 20000 4
Includes force due to normal operating pressure.
TABLE 4-2 COMPARISON OF THE NORMAL LOADS FOR THE PUMP CASING NOZZLES OF SURRY UNITS 1 AND 2 WITH THE SCREENING LEVEL C NORMAL LOADS Load Inlet Nozzle Outlet Nozzle Force 8 Moment Force8 Moment (kips) (in-kips) (kips) (in-kips)
Surry Units 1 and 2 1852 13577 1373 3992 Level C 1900 23000 1400 8000 e: Stresses were determined for a pressure of 2635 psig for the loss-of load transient with the Level C 0
moment loading unchanged. Stresses were also determined for a pressure of 2485 psig which is the reactor trip high pressure limitation.
4 Includes force due to normal operating pressure
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~-------~-
5.0 STABILITY EVALUATIONS In Section 4.0 it is seen that the faulted loads of the pump casing nozzles of Surry Units 1 and 2 are bounded by the Level A screening load of WCAP-13045. Thus the Japp (applied value of the J-integral)" and Tapp (applied value of the tearing resistance) values for the Level A loads given in Table 11-7 of WCAP-13045 are conservative estimates for the corresponding Japp and Tapp values for the faulted loads of the Surry Units 1 and 2 pump casings. It is concluded that the flaws postulated in the Surry Units 1 and 2 pump casings are stable when subjected to faulted loads.
It is also seen in Section 4.0 that the normal operating loads of the pump casing nozzles of Surry Units 1 and 2 are bounded by the Level C screening loads of WCAP-13045.
Thus the Japp and Tapp values for the Level C loads given in Table 11-7 of WCAP-13045 are conservative estimates for the corresponding Japp and Tapp values for the loss-of-load condition of the Surry Units 1 and 2 pump casings. It is concluded that the flaws postulated in Surry Units 1 and 2 pump casings are stable when subjected to loss-of-load conditions.
It is thus concluded that for the primary loop pump casings of Surry Units 1 and 2 all of the postulated flaws under the governing stress conditions are stable.
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1- -- -- - -- -- -- -
6.0 DISCUSSION AND CONCLUSIONS This report provides an assessment of the primary loop pump casings of Surry Units 1 and 2 to the conditions of Item (d) of ASME Code Case N-481 (see Appendix A).
ASME Code properties are used in the reference analyses of WCAP-13045. Fracture toughness values specific to the Surry Units 1 and 2 pump casings are also given in WCAP-13045. Thus Item (d) (1) is satisfied.
Three-dimensio:p.al stress analyses of the Model 93A primary loop pump casing used in Surry Units 1 and 2 are presented in WCAP-13045. This satisfies Item (d) (2).
The operating history of Westinghouse design primary loop pumps is reviewed in Section 2.0 of WCAP-13045. This satisfies Item (d) (3). Flaws are postulated in the Model 93A pump casings in Section 9.0 of WCAP-13045 satisfying Item (d) (4). One- quarter thickness reference flaws with a six-to-one aspect ratio are postulated in WCAP-13045 consistent with Item (d) (5).
By comparing the loads of the Surry Units 1 and 2 pump casings with the screening loads of WCAP-13045, as presented in this report, and evaluating the resulting Japp and Tapp against the fracture toughness values noted in the discussion of Item (d) (1) above as discussed in Section 5.0, the stability of the flaws postulated in the Surry Units 1 and 2 primary loop pump casings are established. This satisfies Item (d) (6).
Thermal aging embrittlement of the Surry Units 1 and 2 pump casings was considered in establishing the appropriate fracture toughness values given in Tables A-2, pages A-51 and A-52 of WCAP-13045. No other mechanism is known to degrade the properties of
., the pump casings during service. Item (d) (7) is so satisfied.
It is concluded that the primary loop pump casings of Surry Units 1 and 2 are in compliance with Item (d) of ASME Code Case N-481.
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7.0 REFERENCES
- 1. Case N-481: "Alternate Examination Requirements for Cast Austenitic Pump Casings,"Section XI, Division 1, Cases of ASME Boiler and Pressure Vessel Code, Approval Date: March 5, 1990.
- 2. F. J. Witt and J. F. Petsche, Compliance to ASME Code Case N-481 of the Primary Loop Pump Casings of Westinghouse Type Nuclear Steam Supply Systems, WCAP-13045, September 1991 (Westinghouse Proprietary Class 2) .
- WPF0938J /120591:10 7-1
ATTACHMENT A CASES OF ASME BOILER AND PRESSURE VESSEL CODE Approval Date: March 5, 1990 See Numerical Index for expiration and any reaffirmation dates.
case N-481 Alternate Examination Requirements for cast Austenltlc Pump CasingsSection XI, Division 1 Inquiry: When conducting examination of cast austenitic pump casings in accordance with Section XI, Division 1, what examinations may be performed in lieu of the volumetric examinations specified in Table IWB-2500-1, Examination Category B-L-1, Item B12.10?
Reply: It is the opinion of the Committee that the following requirements shall be met in lieu of performing the volumetric examination specified in Table IWB-2500-1, Examination Category B-L-1, Item B12.10:
(a) Perform a VT-2 visual examination of the exterior of all pumps during the hydrostatic .
pressure test required by Table IWB-2500-1, Category B-P, (b) . Perform a VT-1 visual examination of the external surfaces of the weld of one pump casing.
(c) Perform a VT-3 visual examination of the internal surfaces whenever a pump is disassembled for maintenance.
(d) Perform an evaluation to demonstrate the safety and serviceability of the pump casing. The evaluation shall include the following:
(1) evaluating material properties, including fracture toughness values:
(2) performing a stress analysis of the pump casing; (3) reviewing the operating history of the pump; (4) selecting locations for postulating flaws; (5) postulating one-quarter thickness reference flaw with a length six times its depth; (6) establishing the stability of the selected flaw under the governing stress conditions; (7) considering thermal aging embrittlement and any other processes that may degrade the properties of the pump casing during service.
(e) A report of this evaluation shall be submitted to the regulatory and enforcement authorities
' having jurisdiction at the plant site for review.
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