ML18191A274

WPPSS Nuclear Project No. 2. Clarification of Criteria, Pipe Rupture Protection Inside Containment

ML18191A274
Person / Time
Site:	Columbia
Issue date:	01/12/1976
From:	Strand N Washington Public Power Supply System
To:	Butler W Office of Nuclear Reactor Regulation
References
G02-76-09
Download: ML18191A274 (36)

Text

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Washington Public Power Supply System A JOINT OPERATING AGENCY P. O. BOX 968 3000 GEO, WASHINGTON WAY RICHI.AND, WASHINGTON SSSS2 PHONS (509) 946 9681 Docket 50-397 January 12, 1976 G02-76-09 Oi pe, PO+gS 0I Director of Nuclear Reactor Regulation Attention:

Dr,.

W.

D. Butler, Chief Light Water Reactors Project Branch 1-2 U. S. Nuclear Regulatory Commission Washington, D.C.

20555

Subject:

WPPSS NUCLEAR PROJECT NO.

2 CLARIFICATION OF CRITERIA PIPE RUPTURE PROTECTION INSIDE'ONTAINMENT

Reference:

Letter from J.

J. Stein to A. Giambusso, Transmitting

Response

to Request for Additional Information - Pipe Rupture Protection Inside Containment, dated March 26, 1975.

(G02-75-89)

Dear Dr. Butler:

We have found certain clarifications are necessary to the referenced trans-mittal with regard to distinguishing between the General Electric - supplied pipe whip restraints and the restraints used elsewhere within the plant.

In addition it has been recognized that Appendix F of ASME Section III is contro-versial within the industry and, therefore, a clarification with respect to the use of Appendix F is also necessary.

These clarifications are provided in paragraphs 3.2.4 and 3.2.5 of Revision 2 of the attached report (WPPSS-74 RI).

Finally, the design basis stress criteria for location of postulated pipe breaks given in paragraph

2. 1. lb has been revised to reflect issuance of the Nuclear Regulatory Commission s Branch Technical Position, MEB 3-1, published in March 1975.

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Hr. Olan D. Parr Page 2

January 12, 1976 G02-76-09 Forty (40) copies of the revised document are being submitted for your review.

Very truly yours, NOS:GLG:vws Enclosure

. 0.

STRAND Assistant Director Generation and Technology cc:

J. J.

Byrnes - Burns and Roe D.

Roe - Bonneville Power Administration F. A. HacLean - General Electric

4, Letter, Mr. N.

Strand to Dr.

W.

D. Butler, e

led "Clarification of Criteria Pipe Rupture Protection Inside Containment,

" dated January 8,

1976, Letter No.

G02-76-09 STATE OF WASHINGTON ss COUNTY OF BENTON N. 0.

STRAND, Being first duly sworn, deposes and says:

That he is the Assistant Director, Generation and Technology, for 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 believes the same to be true to the best of his knowledge.

)

DATED 1976 f

g/

N. 0.

STRAND On this day personally appeared before me N. 0.

STRAND 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 under my hand and seal this~~day of s 1976.

No ry Public in and for the State of Washington Residing at

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WPPSS NP No.

2 PROTECTION AGAINST PIPE BREAKS INSIDE CONTAINMENT REPORT NO.

WPPSS-74-2-Rl Prepared by Burns and

Roe, Inc.

Hempstead, N.Y.

11550 Prepared for WASHINGTON PUBLIC POWER SUPPLY SYSTEM

Richland, Washington W. 0.

2808 Prepared by:

K. Ronis Submitted by:

J. Clapp Revision 2

January 1976

WPPSS NP No.

2 Protection A ainst Pi e Breaks Inside Containment Report Ho. WPPSS-74-2-Rl Revision 2

January 1976 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.

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WPPSS NP No.

2 WPPSS-74-2-Rl PREFACE Revision 2 January, 1976 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 the Post-Construction Permit Meeting with the staff held on October 17-18, 1973 as describes 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 July.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".

d.

USNRC Branch Technical Position MEB 3-1 "Postulated Break and Leakage Locations in Fluid System Piping Outside Containment" as published with USNRC Standard Review Plan Section 3.6.2, dated March, 1975.

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WPPSS NP No.

2 WPPSS-74-2-Rl Revision 2

January, 1976 PROTECTION AGAINST PIPE BREAKS INSIDE CONTAINMENT 1.

S stems In Which Desi n Basis Pi in Breaks Are Postulated l.l 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

'iping systems beyond a normally closed valve.

Pump and 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.

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E 1

TABLE 1 SYSTEM OPERATING TEMP PRESSURE (psig) 1015 1000 1025 1025 1025 1242 1242 1015 1265 1265 1148 955 955 955 955 1150 1100 1012 1261-1246 1261-1246 1015 1015 Low Pressure Core Spray 548 High Pressure Core Spray 534 RHR/LPCI Mode (Loop A)

.550

RHR/LPCI Mode (Loop B) 550 RHR/LPCI Mode (Loop C)

.510

'HR Shutdown Cooling Ret.

(Loop A) 535 RHR Shutdown Cooling Ret.

(Loop B) 535 RHR Shutdown Cooling Supply 534 Reactor Feedwater Line A 420

, Reactor Feedwater Line B 420 RHR Condensing Mode RCIC-Turb.Stm.

553 Main Steam Loop A 541 Main Steam Loop B 541 Main Steam Loop C 541 l Shin Steam Loop D 541 Standby Liquid Control 100 Reactor Water Clean up 533 CRD-Pump Discharge 100/40 Recirc..Pump A Discharge 535-534 Recirc.Pump B Discharge

.535-534 RRC Recirc.Pump A Suction 534-RRC Recirc.Pump B Suction 534 PORTIONS CONSIDERED FOR POSTULATED PIPE BREAK RPV To First Check Valve RPV To First Check Valve RPV To First Check Valve RPV To First Check Valve RPV To First Check Valve N

CO I

I I

Valve MoF009 Recirc.Pump Suet. To Closed Entire Run Within Primary Entire Run Within. Primary Containment Containment Containment Containment Containment Containment Containment Containment Entire Entire Entire Entire Entire RPV To Entire RPV To Entire Entire Entire Entire 0p:

Run Within Primary Run Within Primary Run Within Primary Run Within Primary Run Within Primary First Check Valve Run Within Primary First Check Valve Run Within Primary Run Within Primary Run Within Primary Run Within Primary Contaznment Containment Containment Containment Recirc.Pump Disch.To First Check Valve Recirc.Pump Disch.Te First Check Valve

SYSTEM TABLE 1 (Continued)

OPERATING PORTION CONSIDERED FOR TEMP.

PRESSURE POSTULATED PIPE BREAK

( F)

(Psi9)

RCC-Reactor Pressure Vessel Drain Main Stm.Valves Drainage Piping RPV Head Vent RPV Head Spray 533 545 545 550 1100 1010 1010 1025 RPV To Three (3) Closed Valves Entire Run Within Primary Containment)

Entire Run Within Primary Containment~

RPV To First Check Valve 0

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WFPSS NP No.

2 WPPSS-74-2-Rl Revision 2 January, 1976 2.

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

(a) 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 range of 2.4Sm as computed by application of Equation (10) in paragraph NB3653 ASME Section III, between any two load sets (including the zero load set) for normal and upset plant conditions.

I

~ Iz 2.

For ASME Section III Code Class 2 and 3, stresses of 0.8(1.2 Sh + SA), as calculated by Equation (9) and (10) of Paragraph NC3652 of the ASME Code Section III.

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 flexi-bility(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 twenty pipe diameters in length; a minimum a

Terms.nal ends as used herexn are cz.rcumferentxal pape 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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2 WPPSS-74-2-Rl Revision 2

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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. If 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., If 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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NPPSS NP No.

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WPPSS-74-2-Rl Revision 2 january, 1976 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 readtion.

The pipe segment formed by the first change in direction will be constrained by appropriate restraints, if necessary.

This type of break event will not cause dynamic instability (large amplitude oscillations) since analyses hav shown that critical length required for this phenomenon is substantially greater than any major pipes in the drywell.

3.

Pi e %hi Restraints 3.1 Definition of Function Sr N

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.

The piping integrity does not depend on the pipe whip restraints for any loading combin-ation.

Xf 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 structure 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 under design dynamic and static loads, if the consequences of such instability will result in loss of the primary containment integrity or loss of required plant shutdown capability.

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.

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WPPSS NP NO.

2 WPPSS-74-2-Rl Revision 2 January, 1976 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 spri'ngs 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 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.

For loading conditions including the effects of postulated pipe rupture, these members are designed to limits for inelastic systems, as stated in Table F1322.2-1 of ASME Boiler and Pressure Vessel Code Section III Appendix F "Rules for Evaluation of Faulted Conditions"

)

adjusted to account for rapid strai'n rate effects as dis-cussed in paragraph 3.4.1.

They may also take the shape of U-Bar straps as shown in Figure 1, which act as non-linear, non-rebounding plastic springs.

The U-Bar straps, are justified by empirical data.

3.2e5 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 floor, the primary containment vessel, reactor pedestal, reactor build-ing and foundation.

For loading conditions including the effects of postulated pipe rupture, these members are de-signed to limits as stated in Table F1322.2-1 of ASME Boiler and pressure Vessel Code Section III Appendix F "Rules

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WPPSS-74-2-Rl Revision 2

Januaryi for Evaluating Faulted Condition" 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 in-finitely rigid) will be designed to AISC, ACI and other appropriate Civil and Structural Component criteria.

3.2.6't 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 Ship 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 ~

b.

c ~

d.

Jet pump nozzles Core spray nozzles (inside internals shroud)

Feedwater sparger 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 2

January i 1976 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

consistent incxease 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 3,1(@ 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 testing of materials.

3.4.3 Deformation of energy absorbing flexural 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.'ht.

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,NPPSS NP No.

2 WPPSS-74-2-Rl Revision 2 Januaryi 1976 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'ynamic 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 pi.pe 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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WPPSS NP No.

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WPPSS-74-2-Rl Revision 2

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1976 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'iscussion 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 (Fl), 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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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.

The kinetic energy can be represented'y i /2g, where (i) is the impulse and (H) is the mass of the moving body.

d.

e.

g, h.

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 requixed, 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.

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.

(Y ) is the maximum deflection m

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 c'ompatible with this concept.

Thus (k) can be expressed as (Rr/Ye).

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 Pl).

The maximum deformation of the restraint member can be controlled by limiting the ductility ratio P,).

Pub-lished texts

(

) provide the ductility ratio that corresponds to collapse pre).

For structural steel

members, these values vary,.with uppex limits in the Sht.

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NPPSS NP No.

2 WPPSS-74-2-Rl Revision 2

January, 1976 order of 20 to 30 and up (for very ductile structures).

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

in direct contact with the primary containment vessel are limited to '5% of Pc).

Cely'teel 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 zestitution (full plasticity),

and is a conservative assumption.

With regard to rebound, it should be noted that if a co-efficient of restitution 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 as@tuned (partial rebound),

there would be a partial amount of k~netic energy transfer to the restraint s txucture.

The coefficient of restitution of zero, conservatively assumed in the application of the equation mentioned

above, gives zero rebound together with 100% 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.

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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January, 1976 Cl,l'HER)/1-hozus7.IVZnrrS

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CFi

WPPSS NP No.

2 WPPSS-74-2-R1 Revision 2

January, 1976 F.

F(t)

F (t)

+

F Impulse (i) = F

~ (td).2i Kinetic Energy (K) 2M Ym Note: p = ;Elastic Ye Ref.

3 (Biggs) Chapter 5

Fl Ym + K = Rr (Ym 4Ye)

F x distance (d) 1 Spring Constant k = ~e Paragraph 5.5b Substituting p

Ym g

Y

+ Rr e

2 Ye Rr (p-4)

+F1 Rr (K) (k) = 0 Solving Quadradically:

2 R

= ~F

+

u Fl

+ ~2~Kc+

(2)u-1 (2]u-1)

(2p-1)

REQUIRED RESISTANCE OF STRUCTURES. (R

)

Figure 3

Sheet 18 of 18

WPPSS NP No.

2 WPPSS-74-2-Rl Revision 2

January,.

1976 APPENDIX A AEC REQUEST FOR ADDXTIONAL INFORMATION FOR BURNS AND ROE REPORT NO.

WPPSS-74-2-Rl "PROTECTION AGAXNST PIPE BREAKS INSIDE 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 two load sets (including the zero load set) by Eq.

(10) in Par.

NB-3653, ASME Code,Section III, for upset plant conditions including an OBE event.

RESPONSE

Section 2.1.1 has been revised to reflect the AEC 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 She 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 Information for WPPSS-74-R3 "Protection Against Pipe Steak Outside Containment".

A-1 of 3

4 0

0 WPPSS NP go.

2 WPPSS-74-2-Rl Revision 2

January,,

1976 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 load 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.

RES PONSE:

Section 3.4. 1 has been revised to reflect the AEC acceptable approach stated above.

A-2 of 3

I 7

a WPPSS NP No.

2 WPPSS-74-2-Rl Revision 2

January,.'976 QUESTION 6:

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

a 0 b.

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

(or p) and k.

A description 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 0 b.

Section 4.3.2 has been revised to include discussion relatincr to the parameters shown in Figure 3. Additional discussion regarding the ductility ratio.

is, presented in the response to AEC Structural Engineering Branch Question No.

2 for Report No. WPPSS-74-2-R3 "Protection Against Pipe Brea'k Outside Containment".

The above revision includes 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

J

v a l

J

Docket llo.

50>>397 ra I'ashingion Public Power Supply Systerl

)'iTTil: Nr. R.

U. ').iavidson, Training Coordinator

'P;O.

L'ox gGB 3060 Ceorge t!ashington I!ay-Ri chl and, l asllington 99332 Gentl eri.ien:

T)ris is irI replay to your letter, dated Decer,.Iber 15', 1."7~.

Yaur letter requested inforr!a1ion leqarging eligibility to sit for.cold exaflinations, particularly as it'-i>>volves.'co.cparabl e Taci1 ities.

Undev our pvesent interi)vetation of Section 55;25(b), ef 10 CFR Pavt 55, compavable reactor n ans that.anv large ligl)t, water reactor (P<'? Or O'Ii<)

is col'lI)a) I)le to any other 1 arge 1 ";gl)t watI v reictov

{Pi I? or B !.l).

4

However, as we'indicat d in ouv pl;one conversatio>>, it is higl ly desivQDlo tllat itldlviduals HI)o I)lan to operate a pa/rticulal" typ)e of reactor receive "or~~ training at a nearly identical facility ci. Si:",,ulat d contro'I'room.

Irl addition, training at a c<<niparable fpcility s'i)oauld be obtained within a reasonable peliod of'in (about 2 years) "rola the fuel loading date of the iiew facility.

I t;ope this inforrPation wi:ll be of use to you.

Sincerely,

~

~

I r'e

~ 'e

~a Paul F. Collins, Clli f Opevator Licensing Branch Uivisio>> of Reactor Licensing DISTRIBUTION:

~Si >> y 1

l 1 '" "i'9 OLB Reading File HRC PDR with incoming Local PDR with copy of incoming IE (3)

Central files with copy of incoming J IIIiillaiva oPPIccla RL:,,OLB---'~---

f)

I~~++ +f Vj>

Iat'ol/1 ins'Pib--

.g/xz/75.

dURkAMC+

1'OTIII AKC-3)8 (RCT. 9 53) hKC3K 0240 4 II. d, OOVC:IkMCkT PIIINTIHOOPPICCI 1074 Dcd 101

l'

Washington Public Power Supply System A JOINT OPERATING AGENCY P. 0. BOX 560 3000 GEO. WASHINGTON WAY RICHI.ANO. WASHINGTON SSSS2 PHONE (509) 946.968I December 15, 1975 Nr. Paul F. Collins, Chief Operator Licensing Branch Division of Reactor Licensing U. S. Nuclear Regulatory Commission

'Washington D. C. 20555

Dear Hr. Collins:

On November 4, 1975, I spoke with you concerning the training requirements expected for license candidates with various levels of experience.

In parti-

cular, ere discussed requirements for individuals vrho hold, or have held, f ~bf f llf Y

f df

~bf f ill y <<

ld include any large, light water reactor power plant, either BNR or PHR.

Since the MNP-2 training program requirements are dependent upon this interpretation, I am requesting written verification of your position.

Have a happy holiday season.

Sincerely,

'~z Q. Q~ t'~

R.

D.

DAVIDSON Training Coordinator RDD/jc

y l III

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