ML18191A236

Wppss Nuclear Project No. 2, Response to Request for Additional Information, Pipe Rupture Protection Inside Containment

ML18191A236
Person / Time
Site:	Columbia
Issue date:	03/26/1975
From:	Stein J Washington Public Power Supply System
To:	Giambusso A Office of Nuclear Reactor Regulation
References
G02-75-89
Download: ML18191A236 (39)

Text

fi!RC DISTRI 'ION FOR PART 50 DOCKET MAT IAL (TEMPORARY FORiVI)

CONTROL NO:

FILE:

F ROM. Washington Public Power DATE OF DOC DATE REC'D LTR TWX RPT OTHER Richland, Wash 3-26-75 4-1-75 Stein TO: ORIG CLASS Mr Giambusso.

UNCLASS PROP INFO none signed INPUT CC 1'EiUT OTHER No CYS REC'D AEC PDR

'SENT LOCAL PDR XX DOCKET NO:

50-397 DESCR IPTION: ENCLOSURES:

Ltr,re our 8-23-74 ltr....trans the followin Response to request for Addi info on 'pipe rupture protection inside containment...'.. ~

ACKNOW 0 8"-D (40 cys'nc'1 rec'd)

BO NOT REMOVE PLANT NAME: WPPSS $P2 FOR ACTIOiN/IiUFORMATIOiN 4-1-75 ehf

~yUTLER W/copies (L) SCHWENCER (I.) - Zl EII/IANN.(L)

W/ Copies W/ Copies REGAN (E)

W/ Copies CLARK (L) STOLZ (L) DICKER (E) LEAR (L)

W/ Copies W/ Copies W/ Copies W/ Copies PARR (L) . VASSAI I 0!I ) K) II(I-ivoiiiIE i SPri S W/ Copies W/ Copies W/ Copies W/ Copies KNIEL (L) PURPLE (L) YOUNGBLOOD (E)

W/ Copies W/ Copies W/ Copies W/ Copies INTER!'!AL DISTRIBUTION FIL TECH REVIEW DENTON LIC ASST A/T IND .

SCHROEDER G R liViES R. DIGGS (L) BRAI I iV>ANI OGC, ROOM P-506A MACCARY GAiViMI L I H. GEARIN (L) SA LTZIUlAN GOSS I CK/STAF F KNIGHT KASTNER MELTZ E. GOULBOURNE (L)

CASE PAWLICKI BALLARD p. KREUTZER (E)

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~BOYD STE LLO M. MAIGRET (L) MCDOi\ALD

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HOUSTON NOVAK ROSS ENVIRO ViULLER DICKER S. REED (E)

M. SERVICE (L)

S. SHEPPARD (L)

Cl-IAPMAN DUBE (Ltr)

E. COUPE GOLLER (L) (Ltr) IPPO L !TO KN IG HTON M. SLATER (E) PETE RSOiU P. COLLINS ~TE DESCO YOUNGBLOOD HARTFIELD (2)

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DENISE ~ONG REGAN S. TEETS (L) KLECKER REG OPR LAINAS PROJECT LDR G. WILLIAMS(E) EISENHUT FILE 5 REGION (2) BENAROYA V. WILSON (L) W I G G I N TON T.R. WILSON VOLLMER HAR LESS R. INGRAM! (L)

STEELE EXTERNAL DISTRIBUTION

~ LOCAL PDR ~+~~

~ T!C (ABERNATHY) (1)(2)(10)NATIONALLABS NSIC (BUCHANAN)

P D R-SAN/LA/NY Q ASLB 1 W. PEiNNINGTON, Rm E-201 GT 1 BROOKHAVEN iilAT LAB 1

1 CONSULTANTS 1 G. ULRIKSON, OR'iIL Newton Anderson AGMED (RUTH GUSS:"vlAN)

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NEWiVIARK/8 LUIIIIIE/AG GAB I AN 1 Rm B-127 GT

c. A. AA/GRE7. 1 J. D. RUiiUKLES, Rm E-201 II GT,i, . .' L

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Washington. Public Power Supply System A JOINT OPERATING AGENCY h

P. O. BOX 968 3000 GEO. WASHINGTON WAT RICHLAND. WASHINGTON 90352 PHONE (509) 946 968I

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.Docket No. '0-397 March 26, 1975 G02-75-,89 Mr. A. Giambusso, Director Division of Reactor Licensing Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

WPPSS NUGLEAR PROJECT NO. 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION PIPE RUPTURE PROTECTION INSIDE CONTAINMENT

Reference:

Letter-from W. R. Butler to J. J. Stein, Transmitting Request for Additional Information, Dated August 23, 1974 (GI2-74-25)

Dear Mr. Giambusso:

The attachment provides information requested in the referenced letter.

-This information has been incorporated into a revision of the original report with an appendix referencing the specific changes made in response to each of your questions.

Forty (40) copies of the attachment are being submitted-for your review.

Very truly yours,

. ~La J .. TEIN Managing Director ski 'JS:GLG

~

Attachment c'0CL'O<0 uSNRC cc: JJ Byrnes - Burns and Roe, Inc.

BW Kennedy - Bonneville Power Administration y)975 FA MacLean - General Electric Company

~pp RKuL JJ Verderber - Burns and Roe, Inc.

NUCLEAR 0 S cOIAIAISSIOh

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.iLetter, JJ Stein to A G usso, entit'led "Pipe Rupture P ection Inside Containment," da March 26, 1975, Letter No. GO -89.

STATE OF WASHINGTON )

) ss COUNTY OF BENTON )

J. J. STEIN, Being first duly sworn, deposes and says: That he is the Managing Director of the WASHINGTON PUBLIC POWER SUPPLY SYSTEM, the applicant herein; that he is authorized to submit the foregoing on behalf of said applicant; that he has read the foregoing and knows the contents thereof; and be'lieves the same to be true to the best of his knowledge.

DATED , 1975 J. J. E On this day personally appeared before me J. J. Stein to me known to be the individual who executed the foregoing instrument and acknowledged that he signed the same -as his free act and deed for the uses and purposes therein mentioned.

GIVEN unde~ my hand and seal this . SMday of 1975.

Notary Pu lic in ayd for he State o Washington > <w Residing at

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WPPSS NP No. 2 PROTECTION AGAINST PIPE BREAKS INSXDE CONTAINMENT REPORT NO. WPPSS-74-2-Rl Prepared by Burns and Roe, Xnc.

Hemps tead, N.Y. 11550 Prepared for WASHINGTON PUBLIC POWER SUPPLY SYSTEM Richland, Washington W. O. 2808 Prepared by:

K. Ronis Submitted by:

J. Clapp Revision 1, March, 1975

0 l WPPSS NP No. 2 Protection A ainst Pi e Breaks Inside Containment Report No. WPPSS-74-2-Rl Revision 1 March, 1975 Table of Contents Preface

1. Systems In Which Design Basis Piping Breaks are Postulated

2. Design Basis Postulated Piping Break Criteria 2.1 Locations 2.2 Sizes and Orientation

3. Pipe Whip Restraints 3.1 Definition of Function 3.2 Pipe Whip Restraint Features 3.3 Pipe Whip Restraint Loading 3.4 Material Properties

4. Dynamic Analysis for the Effects of Pipe Rupture 4.1 Criteria 4.2 Analytical Models 4.3 Simplified Dynamic Analysis Appendix A AEC Request For Additional Information and Responses Sht. 1 of 18

I I

WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975

~PREP AC This report describes the measures being taken to protect against pipe breaks inside containment on Washington Public Power Supply System Nuclear Project No. 2 (formerly Hanford No. 2).

This report is in response to the statement made in the Hanford No. 2 Safety Evaluation Report. in Supplement 1, page 3, paragraph 2.2. In addition, it presents the infor-mation discussed at thy Post-Construction Permit Meeting with the staff held on October 17-18, 1973 as described in Agenda Item No. 3 of the attachment to the letter from W. R. Butler to J. J. Stein dated November 20, 1973.

Criteria for protection against pipe breaks inside containment, as described in this report is in accordance with the intent of the following AEC documents, which were utilized as source material:

a~ USAEC Regulatory Guide 1.46 dated May, 1973 "Protection Against Pipe Whip Inside Containment".

b. Letter from the AEC dated tuly 12, 1973 and attached Appendix A entitled "Criteria for Determination of Postulated Break and,Leakage 'Location in High and Moderate Energy Fluid Piping Systems Outside of Containment Structures".

C ~ USAEC Regulatory Staff (Mechanical Engineering Branch)

Position Paper No. 2 entitled "Pipe Whip Analysis".

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 PROTECTION AGAINST PIPE BREAKS INSIDE CONTAINMENT

1. S stems In Which Desi n Basis Pi in Breaks Are Postulated 1.1 Design Basis Pipe Breaks are postulated for those pressurized systems or portions of systems that have a connected source of high-energy fluids during normal plant conditions, (Start-up, normal reactor operation and shutdown).

1.2 Portions of piping systems that are isolated from the source of the high-energy fluid during normal plant conditions are exempted from consideration of Design Basis Pipe Breaks. This would include portions of systems beyond a normally closed valve. Pump and'iping valve bodies are also exempted from consideration of pipe break because of their greater wall thickness and their location in the low stress portion of the piping systems.

1.3 High energy fluid is defined as fluid whose maximum operating temperature exceeds 200 F or whose maximum operating pressure exceeds 275 psig.

1.4 The piping systems or portions of piping systems for which. Design Basis"Pipe Breaks are postulated are shown on Table 1 below.

Sht. 3 of 18

1 0

V 1

TABLE 1

OPERAT ING PORTIONS CONSIDERED FOR SYSTEM TEMP. PRESSURE POSTULATED PIPE BREAK PQ

<<FM (psig) CO I

Low Pressure Core Spray 548 1015 HPV To First Check Valve High Pressure Core Spray 534 1000 RPV To First Check Valve I RHR/LPCI Mode (Loop A) 550 1025 'RPV To First Check Valve I RHR/LPCI Mode (Loop B) 550 1025 RPV To First Check Valve RHR/LPCI Mode (Loop C) .510 1025 RPV To First Check Valve RHR Shutdown Cooling Ret. (Loop A) 535 1242 Recirc.Pump Disch.To First Check Valve RHR Shutdown Cooling Ul Ret. (Loop B) 535 1242 Recirc.Pump Disch. Te First Check Valve a RHR Shutdown Cooling Supply 534 1015 Recirc. Pump Suet.To Closed Valve MoFOO 0 Reactor Feedwater Line A 420 1265 Entire Run Within Primary Containment Reactor Feedwater Line B 420 1265 Entire Run Within Primary Containment RHR Condensing Mode RCIC Turb.Stm. 553 1148 Entire Run Within Primary Containment 0 Main Steam Loop A 541 955 Entire Run Within Primary Containment Main Steam Loop B 541 955 Entire Run Within Primary Containment Main Steam Loop C . 541 . 955 Entire Run Within Primary Containment 18hin Steam Loop D 541 955 Entire Run Within Primary Containment Standby Liquid Control 100 1150 RPV To First Check Valve Reactor Water Clean up 533 1100 Entire Run Within Primary Containment CRD-Pump Discharge leO/40 1012 RPV To First Check Valve Recirc..Pump A Discharge 535-534 1261-1246 Entire Run Within Primary Containment Recirc.Pump B Discharge 535-534 1261-1246 Entire Run Within Primary Containment RRC Recirc.Pump A Suction 534 1015 Entire Run Within Primary Containment RRC Recirc.Pump B Suction 534 1015 Entire Run Within Primary Containment

TABLE 1 M Vl (Continued) I OPERATING PORTION CONSIDERED FOR j hD SYSTEM TEMP. 'PRESSURE POSTULATED PIPE BREAK I

( F) (psig) I RCC-Reactor Pressure Vessel Drain 533 =1100 RPV To Three (3) Closed Valves Main Stm.Valves Drainage 0 Piping 545 1010 Entire Run Within Primary Containment RPV Head Vent 545 1010 Entire Run Within Primary Containment

.RPV Head Spray 550 1025 RPV To First Check@ Valve

e l

MPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975

2. Desi n Basis Postulated Pi in Break Criteria 2.1 Locations 2.1.1 Postulated pipe break locations are as follows:

a. At terminal ends

b. Any intermediate location where the following stresses derived on an elastically calculated basis under loadings associated with QSSE; and start-up, normal 'reactor oper-ation, and shutdown conditions exceed the following specified limits:

1. For ASME Section III Code Class 1 piping, the primary plus secondary stress intensity range of 2S for ferritic steel and 2.4Sm for austenitic steel, as computed by application of Equation (10) in paragraph NB3653 ASME Section III, between any two load sets (including the zero load set) for upset plant conditions.

2. For ASME Section III Code Class 2 and 3, either the circumferential or longitudinal stresses of 0.8 (Sh + SA), where Sh and SA are as defined in NC 3600 and M3 3600 of the ASME Code Section III, Winter 1972 Addenda.

c. For ASME Section III Code Class 1, any intermediate location where the Cumulative Usage Factor (U), derived from piping fatigue analysis under loadings associated with 4SSE; and start-up, normal reactor operation, and shut-down conditions, exceeds 0.1.

d. Intermediate locations "of significant change in flexibil-ity(b) selected 'on a reasonable basis as necessary to provide protection. As a minimum, two such intermediate locations shall be chosen for each piping run or branch run, exceeding trent ipe diameters in length; a minimum (a) Terminal ends as used herein are circumferential pipe weld attachments to vessels, equipment nozzles, and pipe anchor locations, as well as piping branch connections.

(b) Locations of significant change in flexibility as used herein are elbows, tees, crosses, reducers and valve connections.

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 of one location in piping or branch runs twenty pipe-diameters or less in length; except that no intermediate locations need to be postulated in branch runs that are three pipe-diameters or less in length.

2.1.2 Alternate rules for determination of postulated pipe break locations are as follows:

a. At terminal ends (see footnote a, above).

b. All intermediate locations of significant change in flexibility (see footnote b, above).

2.2 Sizes and Orientations 2.2.1 At each of the postulated break locations, consider-ation will be given to the occurrence of either a longitudinal split or circumferential break. Both types of breaks will be considered, if the rules of 2.1.2 above are applied, or if the maximum stress ranges in the circumferential and axial directions are not significantly different. Only one type break will be considered as follows:

a. Xf the result of a detailed stress analysis, such as finite element analysis, indicates that the maximum stress range in the axial direction is at least 1.5 times that in the circumferential direction, only a circum-ferential break will be postulated.

b. Xf this type of analysis indicates that the maximum stress range in the circumferential direction is at least 1.5 times that in the axial direction, only a longi-tudinal split will be postulated.

2.2.2 The following types of breaks are postulated at the locations specified in 2.1 above.

a. Circumferential breaks in piping runs and branch runs exceeding 1-inch nominal pipe size.

b. Longitudinal splits in piping runs and branch runs 4-inch nominal pipe size and larger.

2.2.3 Longitudinal splits are parallel to the pipe axis and are oriented at any point around the circumference. The break area is assumed to be 100/o of the cross-sectional area of the pipe. The break blowdown thrust will be assumed to act perpendicular to the break opening.

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 2.2.4 For circumferential breaks, the free end of the moving pipe will be assumed to move within a plane determined]l by the free end segment and the pipe segment formed by the first change in direction (such as an elbow). The restraint )I reaction force will be assumed to be parallel to the axis of the free end segment:and in a direction compatible with the jet. reaction. The pipe segment. formed by the first change in direction will be constrained by appropriate restraints, necessary. This type of break event will not cause dynamic if instability (large amplitude oscillations) since analyses hav shown that, cxitical length xequired for this phenomenon is substantially greater than any major pipes in the drywell.

'3. Pi e Whi Restraints 3.1 Definition of Function Pipe whip restraints, as differentiated from piping supports, are designed to function and carry load for an extremely low probability gross failure in a piping system carrying high energy fluid.'he piping integrity does not depend on the pipe whip restraints for any loading combin-ation. If the piping integrity is compromised by a pipe break, the pipe whip restraint acts to limit the movement of the broken pipe to an acceptable distance. The pipe whip restraints (i.e., those devices which serve only to control the movement of a ruptured pipe following gross failure) will be subjected to once in a lifetime loading. For the pur-pose of design, the pipe break event is considered to be a faulted condition and the pipe',". its restraints, and structux'e to which the restraint is'attached, shall be analyzed accordingly. Plastic deformation in the pipe is considered as a potential energy absorber. Piping systems will be de signed so that plastic instability does not occur in the pipe undex design dynamic and static loads, if the consequences of such instability will result in loss of the primary containment integrity ox loss of required plant shutdown capability.4 3.2 Pipe Whip Restraint'Features 3.2.1 The restraints are close to the pipe to minimize the, kinetic energy of impact and yet are sufficiently re-moved from the pipe to permit unrestricted thermal pipe movement. Select critical locations inside primary contain-ment will be monitored during hot functional testing to pro-Sht. 8 of 18

WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 vide verification of adequate clearances prior to plant operation.

3.2.2 To facilitate in-service inspection of piping, the restraints are generally located a suitable distance away from all circumferential welds, and are easily removable.

3.2.3 Pipe whip restraint structures fall into one of the following two (2) categories:

a. Energy absorbing members These are modeled as elastic, elasto-plastic or plastic springs in a dynamic analysis. The required resistance of these structures is derived by application of the principles of structural dynamics.

b. Load transmitting members These are relatively stiff components and are modeled as rigid members in the dynamic analysis. Their function is to transmit loading from the source to foundation. The load due to the l postulated pipe rupture is in the form of an equivalent static load and is derived as a result of the dynamic analysis performed for the energy absorbing members.

3.2.4 Energy absorbing members are ductile structures such as simple beams, frames and ring girders, (including the, piping system itself), having the capability to deflect significantly in absorbing the energy imparted to them by a postulated broken pipe. They may also take the shape of U-Bar straps as shown in Figure 1, which act as non-linear, non-rebounding plastic springs. These members are designed to ASME Boiler and Pressure Vessel Code Section III Appendix F "Rules for Evaluation of Faulted Conditions" for componen and component supports. or, as for the U-Bar straps, are justified by dynamic tests.

3.2.5 Load transmitting members are rigid components such as clevises, brackets or pins, rigid pipe whip support linkages as shown in Figure 2, or similar linkages; as well as major structures such as Drywell diaphragm f] d'or, the primary containment vessel, reactor pedestal, reactor build-ing and foundation. These members are designed to ASME Boiler and Pressure'Vessel Code Section III Appendix F "Rules Sht 9 of 18

WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 for Evaluating Faulted Conditions" for components and component supports; except that'the members beyond those included in the dynamic analytical model (i.e. reactor pedestal, reactor building, as well as certain steel members assumed to be infinitely rigid) will be designed to AISC, ACI and other appropriate Civil and Structural Component criteria.

3.2.6 It is presently contemplated, that. the Recirculation Pump Discharge and Suction piping will utilize the U-Bar strap pipe whip supports, while all other systems listed in Table 1 will utilize the rigid type as shown in Figure 2 or similar configurations.

3.3 Pipe Whip Restraint Loading 3.3.1 For the purpose of predicting the pipe rupture forces associated with the reactor blowdown, the local line pressures are assumed to be those normally associated with the reactor operating at 105 percent of rated power and with a vessel dome pressure of 1040 psig.

3.3.2 In calculating pipe reaction, full credit will be taken for any line restriction and line friction between the break and the pressure reservoir. The following re-present typical restrictions to flow which are specifically considered:

a. Jet pump nozzles

b. Core spray nozzles (inside internals shroud)

c. Feedwater sparger

d. Steamline flow limiter 3.3.3 The hydraulic bases and calculational techniques for predicting unbalanced forces on a pipe associated with a postulated instantaneous pipe rupture are presented in Appendix B of G.E. Document NEDO10990 dated September, 1973.

3.3.4 The dynamic loading on, the pipe whip restraint commences at the effective time of impact of the pipe with the restraint. It includes the following:

a. Unbalanced force on the pipe, associated with a postulated instantaneous pipe rupture in the form of a suddenly applied force.

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975

b. Dynamic inertia load of the moving section of pipe, which is accelerated by the unbalanced force associated with the pipe rupture and collides with the restraint.

This load is in the form of a kinetic energy of impact.

3.4 Material Properties 3.4.1 To account for the rapid strain rate effects, dynamic yield strength is utilized. This phenomenon is documented in published texts. (1) (2) Material tests have shown a

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consistent increase in yield strength under rapid loading.

Under rapid strain rate carbon steel yield strength improves by more than 40/o. High strength alloy steel displays a somewhat smaller improvement. For this project, a conserva-.

tive dynamic yield strength of 3.10% of minimum yie3'd strength at the specific operating temperature is utilized unless higher values are justified by tests or other means.

3.4.2 Pure tension members, such as U-Bars shown on Figure 1, which constitute pipe whip limit stops, will be permitted to deform a maximum of 50/o of the maximum uniform strain during energy absorption, subject to verification by dynamic tes t ing of materials.

3.4.3 Deformation of energy absorbing flexura'1 support members will generally be limited to 50/o of that deformation which corresponds to structural collapse, except that de-formation of members in direct contact with the primary containment vessel will be limited to 5% of that deformation which corresponds to structural- collapse.

(1) Air Force Design Manual Principles and Practices for Design of Hardened Structures U.S. Department of Commerce, Office of Technical Services, Publication AD 295408 (AFSWC-TDR-62-138) December, 1962.

(2) "Design of Structures to Resist Nuclear Weapons Effect" ASCE Manual, of Engineering Practice No. 42, 1961.

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 3.4.4 The material and structural shapes for energy absorbing members will be in accordance with recommendations for dynamic member design as documented in published texts; or will have the adequacy verified by dynamic tests.

4. D namic Anal sis for the Effects of Pi e Ru ture 4.1 Criteria 4.1.1 Analysis will be performed for each postulated pipe break.

4.1.2 The analysis includes the dynamic response of all components of the system including the pipe in question, pipe whip restraints and all structures required to transmit loading to foundation. The structures are analyzed for a suddenly applied force, in conjunction with impact and re-bound effects due to gaps between piping and restraints.

4.1.3 The analytical model will adequately represent, the mass/inertia and stiffness properties of the system.

4.2 Analytical Models 4.2.1 Lumped-Parameter Analysis Model; Lumped mass points are interconnected by springs to take into account inertia and stiffness effects of the system, and time histories of responses are computed by numerical integration to account for gaps and inelastic effects.

4.2.2 Energy-Balance Analysis Model; Kinetic energy generated during the first quarter cycle movement of the ruptured pipe as imparted to the piping/restraint system through impact is converted into equivalent strain energy.

Deformations of the pipe and the restraint, are compatible with the level of absorbed energy.

4.3 Simplified Dynamic Analysis 4.3.1 In order to simplify dynamic analysis the following conservative assumptions may be utilized:

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C WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975

a. The entire structure including pipe, support linkage, support beams and major structure to foundations absorbs energy by elastic, elasto-plastic, or plastic deformation.

In order to provide a simplified dynamic mathematical model, certain components of the structure will be assumed as infinitely rigid. These will be classified as load transmitting members and designed accordingly.

b. Time history of unbalanced forces on the ruptured pipe may be simplified to a suddenly applied, constantly maintained force, such as to envelope the actual force at any particular time.

c. Dynamic loading on the pipe whip restraint may be simplified to a suddenly applied constantly maintained force described above, in conjunction with a kinetic energy of impact.

4.3.2 Simplified analytical models such as simple beams, structural frames and ring girders on assumed rigid supports can be modeled as single springs. For these, the required member resistance (Rr) can be determined by application of the formula derived by Burns and Roe, as shown in Figure 3.

This derivation is based on published texts (3)(4). The following is a description and discussion regarding the parameters utilized in this derivation:

a. The term (Rr) represents the required member resistance, when loaded by a suddenly applied, constantly maintained force (Fj), in conjunction with a kinetic energy of impact (K) due to .collision of a moving body (i.e.

ruptured pipe) with the member in question; (3) "Introduction to Structural Dynamics" by John M. Biggs, McGraw-Hill, 1964.

(4) "Structural Design for Dynamic Loads" by Norris, Hansen, Holley, Biggs, Namyet and Minami, McGraw-Hill, 1959.

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975

'b. The impluse (i) can be represented by the area under any load time history having a time of duration (td),

which is small, compared with the natural period of the impacted member.

c. The kinetic energy can be represented by i /2M, where (i) is the impulse and (M) is the mass of the moving body.

d. The kinetic energy of impact (K) can also be represented by the product of the Force (Fl), which accelerates the ruptured pipe, and a distance (d), being the total dis-tance travelled by the moving body from time zero to time of collision with the member in question. Note that when the resisting member is in direct contact with the ruptured pipe the distance (d) in zero and the 'kinetic energy (K) reduces to zero. Likewise, when no resisting member is required, the ruptured pipe does not collide with anything and therefore no kinetic energy of impact exists. In these events the equation shown in Figure 3 is applicable, with (K) equal to zero.

e. The resisting member is permitted to deform beyond elasticity. Thus the member resistance is bilinear.

(Ye) is the deflection of the member at the end of elasticity of the member. (Ym ) is the maximum deflection of the member.

The elastic spring constant (k) is the ratio of load on the member divided by the deflection due to this load, where the deflection is equal to or less than the value (Ye) and the load is compatible with this concept. Thus (k) can be expressed as (Rr/Ye)-

ge For inelastic response, the maximum deflection (Ym) is always larger than the elastic deflection (Ye). For this case, the ratio (Ym/Ye) is defined as the ductility ratio P) .

h. The maximum deformation of the restraint member can be controlled by limiting the ductility ratio p.). Pub-lished texts (1) provide the ductility ratio that corresponds to collapse pre). For structural steel members, these values vary, .with upper limits in the Sht. 14 o f 18

WPPSS NP No. 2 WPPSS-74-2-Rl Revision l March, 1975 order of 20 to 30 an'd up (for very ductile'tructures).

For this project, the maximum permissible ductility ratio is limited to 50/o of (pc), except that members

in direct contact with the primary containment vessel are limited to 5% of (pc). Qrily st@el members are utilized as energy absorbing members, as defined in Section 3.2.4.

The equation derived in Figure 3 accounts for a

,suddenly applied, constantly maintained force, in conjunction with a 'kinetic energy of impact on the resisting member. Total transfer of'energy is implied.

This is combined with the constantly maintained force (from ruptured piping blowdown) on the restraint structure. This assumption is consistent with a zero coefficient of restitution (full plasticity), and is a conservative assumption.

'ith regard to rebound, it should be noted that if a co-efficient of qestitution of unity were assumed (full rebound), there would be zero kinetic energy transfer to the restraint structure.

If a coefficient of restitution less than unity were assumed (partial rebound), .there would be a partial amount of, kinetic energy transfer to. the restraint structure.

The coefficient of restitution of zero, conservatively assumed in the application of the equation mentioned above, gives zero rebound together with 100/o of the kinetic energy transfer to the restraint, structure.

It should also be noted, that the assumption of a in the equation mentioned above, is conservative with respect to rebound, inasmuch as rebound implies a finite time of contact, with the restraint structure of short duration, in contrast with the infinite time assumed.

H 4.3.3 Actual structural resistance for the above structures is determined by methods of limit analysis using a dynamic yield strength as defined im paragraph 3.4.1 above.

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U-BAR STRAP PIPE WHIP SUPPORT Figure 1 Sht. 16 of 18

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WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 F ~

F (t) F t

+ Fl td Impulse (i) = F ~

(td)

Kinetic Energy 3.

(K) i = F x distance (d)

Note: px = ;Elastic Ym

,Ye 2M 1 Spring Constant k =

~e Ref. 3 (Biggs) Chapter 5 Paragraph 5.5b F] Ym + K

= Rr (Ym 4Ye)

Substituting I- u = Ym g Y + Rr 2

Rr. (P- 4) -PF1 Rr (K) ('k) = 0 Solving Quadradically R = ~F~

(2)m-1

+

u Fl (2jtx-1) 2

+ ~2K~

(2p-1)

REQUIRED RESISTANCE OF* STRUCTURES. (R )

Figure 3 Sheet 18 of 18

P WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 APPENDIX A AEC REQUEST FOR ADDITIONAL INFORMATXON FOR BURNS AND ROE REPORT NO. WPPSS-74-2-Rl "PROTECTION AGAINST PXPE BREAKS XNSIDE CONTAINMENT" FOR WASHINGTON PUBLIC POWER SUPPLY SYSTEM; NUCLEAR PROJECT NO. 2.

QUESTION 1:

Supplement Section 2.1.1 clarifying the procedures used to calculate the stress intensitites for ASME Class 1 piping by which the design basis break locations are determined. The acceptable approach is to compute the maximum stress range between any tw'o load sets (including the zero load set) by Eq. (10) in Par. NB-3653, ASME Code,Section IIX, for upset plant conditions including an OBE event.

RESPONSE

Section 2.1.1 has been revised to reflect the'EC acceptable approach stated above.

UESTION 2:

Supplement Section 2.2.1 by providing the criteria used to identify the most probable type of break based on examination of the state of stress in the vicinity of the postulated break location. The acceptable criteria are that if the re-sults of a detailed stress analysis (i.e. finite element analysis) indicates that the maximum stress range in the axial direction is at least twice that in the circumferential direction, only a circumferential break need'be postulated, and that if the maximum stress range in the circumferential direction is twice or more than the axial direction, only a longitudinal break need be postulated.

RESPONSE

Section 2.2.1 has been revised to reflect the AEC acceptable approach stated above, except that a minimum stress ratio of 1.5 is utilized, in lieu of the value of 2, shown above. This modification reflects the latest acceptable MEB position, as stated in their Request for Additional Xnformation for WPPSS-74-R3 "Protection Against Pipe Break Outside Containment".

A-1 of 3

PSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 UESTION 3:

Supplement Section 2.2.4 by clarifying your intention to constrain the piping systems such that for circumferential breaks, the free end will always move within a plane formed by the free-end segment and the segment at the first change in direction. In lieu of the above, justify that the possi-ble out-of-plane motion need not be considered.

RESPONSE

Section 2.2.4 has been revised to include justification that possible out-of-plane pipe motion need not be considered.

UESTION 4:

Supplement Section 3.2.3.b by describing the methods and procedures used to determine the equivalent static loadings for stiff load transmitting members.

RESPONSE

Section 3.2.3b'has been revised to include a description of derivation of equivalent static loads for lqad trans-mitting members.

QUESTION 5:

The criteria presented in Section 3.4.1 to account for the rapid strain rate effects are not acceptable. Only 10%%d increase in minimum yield strength at the specific operation temperature is acceptable. Revise your criteria of strain rate effects or provide justification.

RESPONSE

Section 3.4.1 has been revised to reflect the AEC acceptable approach stated above.

A-2 of 3

WPPSS NP No. 2 WPPSS-74-2-Rl Revision 1 March, 1975 UESTION 6:

Supplement Section 4.3 concerning simplified dynamic analysis by providing the following:

a. A description concerning the methods and procedures used to determine those parameters in the equation as shown in Figure 3 for calculating Rr, such as Ye, Y ,

p.) and k. m'or b.. A descriptiop concerning the procedures used to check whether the restraint design meets the specified strain or deformation limit.

c. A justification for neglecting the effects of piping rebound.

d. A justification for using the same F~ for impulse terms and steady state terms as shown in Figure 3.

RESPONSE

a. Section 4.3.2 has been revised to include discussion relatinq to the parameters shown in Figure 3. Additional discussion regarding the ductility ratio, is presented'n the response to AEC Structural Engineering Branch Question No. 2 for Report No. WPPSS-74-2-R3 "Protection Against, Pipe Break Outside Containment".

b. The above revision i.ncludes Section 4.3.2h discussing the limitations of deformatim .

c. The above revision includes Section 4.3.2j which discussed the effects of piping rebound.

d. The term Fl used for impulse terms in Figure 3 has been revised to F . ,The term Fl is still utilized for the suddenly applied, constantly maintained force.

A-3 of 3

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III il rT e I

1 1>

Cl