ML20106B040

Requests Approval to Eliminate Arbitrary Intermediate Breaks in All High Energy Piping Sys by 850315.Evaluations Required Prior to Granting of Break Criteria Revs Encl

ML20106B040
Person / Time
Site:	Seabrook
Issue date:	02/07/1985
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	Knighton G Office of Nuclear Reactor Regulation
References
SBN-761, NUDOCS 8502110442
Download: ML20106B040 (39)

Text

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tr-SEABROOK STATION Engineering Office February 7, 1985 Pub 5c Service of New Hampshko SBN- 761 New Hampshire Yankee Division T.F. B7.1.2 United States Nuclear Regulatory Commission Washington, D. c. 20555 Attention: Mr. George W. Knighton, Chief Licensing Branch No. 3 Division of Licensing

References:

(a) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444

Subject:

Elimination of Arbitrary Intermedicte Pipe Breaks

Dear Sir:

The New Hampshire Yankee Division of Public Service Company of New Hampshire has noted that the Nuclear Regulatory Commission (NRC) has approved industry proposals to modify certain aspects of current pipe break criteria.

These approvals include the elimination f rom design consideration the postulation of those pipe breaks commonly referred to as Arbitrary Intermediate Breaks ( AIBs).

Currently, AIBs are postulated to provide the minimum of two pipe breaks at the two highest stress locations between piping terminal ends, even though analyses have shown stresses and/or cumulative usage factors do not exceed current Staff criteria. Consequently, AIBs are frequently postulated at locations where calculated stresses and/or cumulative usage factors are significantly below allowables. AIB postulation necessitates the design, fabrication, installation, and maintenance of complicated mitigating devices

to afford protection from dynamic effects, such as pipe whip and/or jet impingement. In cases where these selected break locations have stress levels slightly greater than the remainder of the system, the installation of mitigating devices not only lends little to overall plant safety, but also provides the potential for inadvertent thermal bind-up.

By way of this letter, we request that the Staff appreve the elimination of arbitrary intermediate breaks in all high energy piping systems (excluding the Feedwater System, which will be the subject of a separate request) at Seabrook Station, Units 1 and 2. The AIBs we are seeking to eliminate are delineated in Enclosure E. This request includes the exclusion of all dynamic effects associated with AIBs, (i.e., pipe whip, jet impingement, and compartment pressurization loads).

8502110442 8:H)207 PDR ADOCK 05000443 A PDR P.O. Box 300 + Seabrook.NH03874 Telephone (603)474-9521

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-United States Nuclear Regulatory Commission Attention: Mr. George W. Knighton, Chief Page 2 We currently utilize break selection criteria derived from NRC Branch Technical: Position MEB 3-1 as delineated in Section 3.6(B) of the Seabrook Station Final Safety Analysis Report (FSAR). Our proposed break criteria

! revision is incorporated in an annotated version of the Seabrook Station FSAR l

..  ; ~~ Section 3.6(B) which is provided as Enclosure F to this letter.

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In support of.the Staff's review of our proposed elimination of AIBs from the Seabrook Station design bases, na have included six enclosures to this

. : ,. ; j , ' letter which address the evaluations required by the Staff prior to the M4 , Jgranting of. break criteria revisions:

Enclosure Subject

> A Benefit Summary B Technical Justification C Transient Forces and Vibrational Effects D Potential ~ for Stress Cracking in PWR Piping E Breaks to be Eliminated F Proposed FSAR Revision

, - ' In; summary, it is-apparent that the elimination of AIBs on the noted high

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energy piping systems will~not in any way compromise overall plant safety'or structural-design. Staff acceptance .of our request would result in .

substantial benefits in terms of reduced occupational radiation exposure and cost savings over the forty year plant life. EDue to the advanced stage of design _and construction of Unit 1, the realization of these potential benefits

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.will-be severely tempered if our request is not granted in a timely manner.

<We therefore.irequest a decision on this proposal by March 15, 1985.

If. I~ can37 e of further assistance, or if a meeting with. the Staff is deemed beneficial, do not hesitate to contact me.

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-Very truly.yo rs,.

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. DeVincentis, Director

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Engineering and Licensing:

IAttachments.

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cc:1 - At'omic Safety and Licensing Board Service. List ~

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' William S. Jordan, III Dians Curran Harmon, Weiss & Jordan 20001 S Street N.W. Brentwood Board of Selectmen Suite 430 RED Dalton Road

. Washington, D.C. 20009 Brentwood, New Hampshire 03833 Robert G. Perlis -

Office of the Executive Legal Director Edward F. Meany 4

.U.S. Nuclear Regulatory Commission Designated Representative of Washington, DC 20555 the Town of Rye 155 Washington Road Robert A. Backus, Esquire Rye, NH 03870 116 Lowell Street l P.O. Box 516 Calvin A. Canney Mancehster, NH 03105 City Manager City Hall Philip-Ahrens Esquire 126 Daniel Street Assistant Attorney General Portsmouth, NH 03801

Department of the Attorney General Augusta, ME 04333 Dana Bisbee, Esquire Assistant Attorney General Mr. John B. Tanzer Office of the Attorney General Designated Representative of 208 State House Annex the Town of Hampton Concord, NH 03301

! 5 Morningside Drive i Hampton, NH 03842 Anne Verge, Chairperson Board of Selectmen j Roberta C. Pevear Town Hall Designated Representative of South Hampton, NH 03642 l

the Town of Hampton Falls

'Drinkwater Road ratrick J. McKeon

[ Hampton Falls, NH 03844 Selectmen's Office 10 Central Road

-Mrs. Sandra Gavutis Rye, NH 03870 Designated Representative of the Town of Kensington Carole F. Kagan, Esq.

RFD 1 Atomic Safety and Licensing Board Panel East Kingston, NH 03827 U.S. Nuclear Regulatory Commission

'Jo Ann Shotwell, Esquire Assistant Attorney General Mr. Angie Machiros e

Environmental Protection Bureau Chairman of the Board of Selectmen Department of the Attorney General Town of Newbury One Ashburton Place, 19th Floor Newbury, MA 01950 Boston, MA 02108 i Town Manager's Office Senator Gordon.J. Humphrey Town Hall - Friend Street U.S. Senate .

Amesbury, Ma. 01913

, Washington, DC 20510 (Atta: Tom Burack) Senator Gordon J. Humphrey ,

1 Pillsbury Street Diana P. Randall Concord, NH 03301 70 Collins Street -(Attn: Herb Boynton)

SEabrook, NH 03874 Richard E. Sullivan, Mayor Donald E.' Chick City Hall Town Manager Newburyport, MA 01950 Town of Exeter f -10 Front Street Exeter, NH 03833 i

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ENCLOSURE A SEABROOK STATION i

BENEFIT

SUMMARY

ELIMINATION OF ARBITRARY INTERMEDIATE PIPE BREAKS i <

k 1. Improved access for inspection, Improve quality of inservice inspec-i . maintenance and operation. tion. Reduce radiation exposure

, during ISI. Reduce plant down-time i during ISI outages. A savings of f 80-100 man-rea/ unit is estimated over the 40 year plant life.

2. Engineering, f abrication and Estimate $1.2 million/ unit (1984 j installation of 22 pipe rupture dollars).

restraints and jet shields.

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3. Reduction of heat loss and Relatively minor,- but real savings.

elimination of expensive Min-K Delicate Min-K insulation may be re-insulation of pipe restraint placed by durable sections, designed i~ locations. . to be removable for ISI.

4 Improvement in overall plant Eliminate potential for uninten-safety (NUREG-CR-2136). tional restricted piping movement.

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ENCLOSURE B 1 *

SEABROOK STATION JUSTIFICATION FOR THE ELIMINATION OF ARBITRARY INTERMEDIATE PIPE BREAKS We feel that sufficient technical justification exists for the elimination of I the arbitrary intermediate pipe breaks req'uired to be postulated in High Energy, ASME Code Section III Piping to comply with Standard Review Plan 3.6.2. Our

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. justification is as follows

1) Operating Experience Does Not Support the Need for the Criteria 1he combined operating history of commercial nuclear plants, both domestic and foreign, has not shown the need to provide protection from the dynamic ef fects of arbitrary intermediate breaks.

2) System Piping Stresses Are Well Below ASME Code Allowables Branch Technical Position MEB 3-1 requires the postulation of intermediate breaks in Class 2 and 3 piping where the stresses exceed 0.8 (1.2 Sh + SA )*

This is only 80% of the ASME Code allowable stresses.

Intermediate breaks for Seabrook Station were postulated in Class 2 and 3 piping where stresses exceeded 0.8 (Sh + SA), which provides additional con-servatism.

i Welded attachments are generally not located near (approx. 5 pipe diameters) arbitrary intermediate breaks. Any arbitrary intermediate break located near welded attachments, such as shear lugs, will not be deleted. Therefore, local

- bending stresses from these attachments will not affect the stress levels at the arbitrary break locations being deleted.

i. Deletion of pipe rupture restraints associated with the arbitrary inter-mediate breaks will reduce possible unanticipated thermal restraint of.

piping.

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3) Arbitrary Intermediate Breaks Complicate the Design Process Since the design of piping systems is generally an iterative process, the location of the highest stress points usually change several times as the design evolves. The alternate criteria of SRP 3.6.2 (NUREG 0800) provides little relief from moving arbitrary break locations as the revised break locations must still be evaluated as to their effects on essential equip-

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4) Substantial Cost Savings The elimination of pipe whip restraints and jet shields is the primary cost benefit realized by the elimination of the arbitrary intermediate breaks.

Plant operation costs will also be reduced, as reduced manhours for in-service inspection and maintenance will result. The cost benefit for Seabrook Station is provided in Attachment A.

5) Improved Inservice Inspection Pipe whip restraints are normally located adjacent to or surrounding the welds at changes in pipe direction. The dismantling and reinstallation of portions of the restraint structures associated with arbitrary breaks to gain proper access for the pe rformance of inservice inspection would be eliminated.

Also, the absence of s tructural framing will allow for better inspection technique and quality.

6) Reduction in Radiation Exposure The elimination of pipe whip restraints and jet shields associated with ar-bitrary breaks, and the large structures necessary to support them, will result in more ef ficient maintenance, inspection and decontamination operations. In-proved access for firefighting will also be gained. A reduction in the time required to perform all of these activities will result in a significant reduc-tion in personnel exposure to radiation over the 40 year plant life. Attach-ment A provides an estimate of the man-ren benefit to be realized if the ar-bitrary breaks are eliminated.

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7) Improved Operational Efficiency The elimination of pipe whip restraints associated with arbitrary breaks will preclude the requirement for cut back insulation or special insulat.ing assen-

- blies near the close fitting restraints and will reduce the heat load in plant buildings, especially inside containment.

8) Proper System Design and Operating Procedures The Mechanical Engineering Branch, in Branch Technical Position MEB 3-1, re-cognizes that "... pipe rupture is a rare event which may occur only under unanticipated conditions such as those which might be caused by possible design, construction, or operation errors; unanticipated loads or unantici-pated corrosive environments." For Seabrook Station, there are many ways in which those unanticipated conditions may be detected. The system transient (water-hammer) and vibrational stress testing portions of the preoperational and startup test programs, as discussed in Attachment C, minimize unanticipated conditions arising from design, construction or operation errors and also from unarticipated loads, while control of water chemistry and materials used during f abrication, installation, startup testing and operation minimir.e exposure to potentially corrosive environments, as discussed in Attachment D.' Once Seabrook station begins operation, an extensive In-Service Inspection (ISI)

Program will continue to provide that assurance and will detect any system degradation before unsafe conditions develop.-

9)_ Adequacy of Equipment -Qualification L

The elimination of arbitrary intermediate breaks will not downgrade the. environ-mental qualification levels of Class IE equipment. The break postulation for

[ . environmental ef fects is performed independently of break postulation for

. pipe whip and jet impingement.

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ENCLOSURE C SEABROOK STATION TRANSIENT FORCES AND VIBRATIONAL EFFECTS ASSOCIATED WITH ARBITRARY INTERMEDIATE BREAXS Seabrook Station piping systems ware designed in accordance with good engineering practice. The steam systems were sloped and will be provided with adequate drainage where necessary to prevent unacceptable condensate build-up. Water systems were routed to minimize void formation. In addition, the possibility of large transient (water-hamer) forces due to normal and abnormal plant conditions in piping 4* stems with postulated arbitrary intermediate breaks has been thoro c ly analyzed for Seabrook. A limited set of transients was originally addres.;4d for Seabrook Station design, however, the INPO design audit of 1983 highlighted the need to increase the scope of the evaluation and to have the basis and results fully documented.

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A systematic review was performed for all systems designed under the ASME .

Section III Code and a Transi'ent Analysis Program instituted to determine the themal and hydraulic transients forces generated in response co an extensive matrix of initiating events. The forces thus generated wilJ be included in the piping stress analysis and considered in the design of the pipe support systems. This program is still in progress and is scheduled to be completed' so as to permit incorporation into the stress reconciliation program.

Systems within the Westinghouse scope of supply are not, in general, susceptible to water hamer. The Reactor Coolant, Chemical and Volume Control, and Residual Heat Removal Systems have been designed to preclude water hamer. Preoperati' ial testing and operating experience have verifled that the Westinghouse der n is not susceptible and furthemore, have indicated that significt . <ater hamer events have usually been initiated within the Balance of Pl. + (BOP) scope of supply. As previously discussed, hydraulic transients postulated for BOP systems are incorporated in the design loads and system design features to preclude water hanner effects.

Concurrently Westinghouse has conducted a number of investigations into the causes and consequences of water hanner. The results of these investigations have been reflected in the BOP design interface requirements to assure that water hamer events that may be initiated in' the BOP secondary systems do not compromise the performance of the Westinghouse supplied safety-related systems and co.nponents.

The lines for which arbitrary intermediate break elimination is being requested and that have any potential for water hamer/ steam hammer effects are being designed to minimize or preclude such effects. Water hamer j mitigation efforts for each system involved in the elimination of arbitrary breaks are discussed below. Also, each system description is supplemented.-

4 with the list of significant transients that have been postulated.

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1. Reactor Coolant System (RC)

a. Unanticipated Transients There is a low potential for water hamer in the Reactor Coolant System because it is designed to preclude steam void formation.

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a However, excessive cooling of the Reactor Coolant System, which initiates safety injection, could potentially result in water hanumer. If any problems are experienced during preoperational testing, they will be eliminated by modifying operating procedures.

$ b. Postulated Transients for RC System - (Non-NSSS Portion) o opening of Pressuriser PORV(s) .

o Opening of Pressurizer Safety Vsives(s) o Opening of RHR Suction Line Relief Valves e

o closure of Containment Isolation Valves

2. Safety Iniection System (SI)

s. Unanticiosted Transients f

The safety injection lines are all water solid and at ambient temperature. Therefore, there is a low probability of water hanumer

problems in this system.

b. Postulated Transients for SI' System .

o SI Pump Trip .

i o Spurious Closure of SI Pump Suction Valves

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o Spurious Closure of SI Pulp Discharge Valves o- Opening of System Relief Valves X

3. Chemical and Volume control Sysiem (CVCS) l

a. Unanticipated Transients 9.

Normally, the CVCS System is water solid. In the low temperature

~ lines water hammer would not be expected because of the small probability of steam void formation. In the high temperature lines, X the piping has been designed to maintain water solid conditions c-during normal operation, thus minimizing the possibility of water l 'J hananer effects.

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hD. Postulated Transients for the CS System - (Letdown /Charaina Portion) l:{ .

q4 o Charging Pump Trip (Positive Dispircement or Centrifugal) t o Closure of Containment. Isolation Valves-

..]r o - Opening',ofI System Relief Valves r, f,ij.

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.o q-Spurious operation of Letdown Flow Control Valves s .

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4. Main Steam (MS) l

. a. Unanticipated Transients As a result of the four-inch warm-up lines being designed to be normally filled with steam and the steam drain lines being designed for water flow with no water accumulation, water hammer due to improper condensate drainage is not expected.

b. Portulated Transients for MS System o Turbine Trip o Wolature Separator / Reheater Trip o Safety Valve Actuation o Load Change > 10%

o Main Steam Isolation Valve closure (Including Spurious) o Reactor Trip

5. Steam Generator Blowdown System

a. Unanticipated Transients Blowdown flow from the steam generators is normally two-phase and of 0-10 percent quality. The normal flow regime between the steam generator and the blowdown control valvo is slug flow. This section of pipe is run in horizontal and descending vertical-less to the piping low point drain. The normal flow regime downstream of the containment isolation and blowdown control valv(s to the flash tank-lies in the dispersed flow regime. Operating procedures calling for gradually increasing flow into the normal operating range minimize the potential for water hammer downstream of the blowdown control valve while establishing flow during startup and during re-initiation after containment isolation.

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b. Postulated Transients for SB System ,

o Change in Blowdown Rate o Containment Isolation Valve Closure (Including Spurious)

Note,.many of the above transients will be investigated during the preoperational test and initial'startup programs as discussed in FSAR Subsection 3.9(B).2.1.c.

The preoperational vibration testing program at Seabrook will help minimize-the potential for vibration fatigue. During the testing, both transient and steady-state-vibration of high energy critical piping will be moni~ cored and evaluated.

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A lioting of th3 cystems which will b3 monitercd fcr vibecticn during preoperational and startup testing is contained in FSAR Table 3.9(B)-1 and is

. included herein. I For the vibration tests, selected lines will be visually inspected and I l

sections to be investigated will be identified, with special attention paid to piping between supports, instrument connections, vent and drain connections, and valve operators. Displacement, frequency, and acceleration will be '

measured as applicable.

If measured parameters exceed acceptable tolerances, the effect of the vibration on the system design will be evaluated by analysis. The analysis will consider piping stresses based on vibration amplitude and combined stresses due to other applicable loads including vibration. The evaluation will determine fatigue life based upon stress level, frequency, and endurance limit. In addition, the evaluation will take into account the operability of any in-line components based on the measured accelerations compared to the component qualification and also the operability and accuracy of instruments connected to the piping.

Acceptance criteria for st'eady-state vibration will limit peak vibratory stress to a conservative limit based upon material type; that limit is selected well below the material fatigue endurance limits defined in the ASME Code. .

In conclusion, we expect that Seabrook Station will not experience problems due to transient forces or vibrational fatigue in the piping systems containing arbitrary breaks.

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TABLE 3.9(B)-1 *

(Sheet 1 of 3) ,

SYSTEMS REQUIRING MONITORING OF THERMAL EXPANSION, VIBRATION AND DYNAMIC EFFECTS DURING START-UP FUNCTIONAL TESTING System Line No. ,

Parameter Measured Location / Comments Reactor Coolant I thru 12 See Comments See 3.9(N).2.1 74-2 ' Vibration, thermal disp 1. Immediately downstream of pressurizer 75-2 76-2 80-5 Residual Heat 155-2 Vibration Immediately downstream of the connecting Removal RRR HX Bypass and Discharge IJnes 158-2 Immediately downstream of the connecting RCR HX Bypass and Discharge Lines Safety Injection 250-15 Vibration Immediately downstream of the SI pumps 251-19 Immediately downstream of the SI pumps os en ~

Chemical and 355-1 Vibration At suction and discharge of charging pump. $ e.

At suction and discharge of charging pump. p Volume Control' 357-1 362-1 Immediately downstream of charging pumps.

364-1 Immediately downstream of charging pumps.

437-3 chiller inlet and outlet lines downstream of PCV-131.

439-1 Chiller inlet and outlet lines downstream of PCV-131.

441-3 Downstream of connection between letdown chiller HX bypass and outlet lines.

Primary Componenc 752-1 Vibration Downstream of the connection between CCHX Cooling bypass and outlet lines.,

798-1 Downstream of the connection between CCHX bypass and outlet lines.

816-1 Downstream of TV-130

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(Sheet 2 of 3)

System- Line No. Parameter Measured Jpeation/ Comments

. Spent Fuel 1704-2 Vibration Downstream of the connection with line

- Pool Cooling 1704-7.

i Service Water Vibration Immediately downstream of valves SW-V15, V16, V18, V19, V20 V26, V55.

Waste Gas 562-l' Vibration immediately downstream of compressor.

567-1 Immediately downstream of compressor.

Steam Generator '1301-2 Vibration, ther. expansion Downsteam of valves SB-V189, V191, V193 Blowdown 1304-2 and V195.

1307-2 Downstream of valves SB-V21, V22, V23

- 1309-2 and V24 in lines to the flash tank.

m Condensate 4046-1, 4047-1, 4048-1 Vibration, ther. expansion Condensate pump discharge. y W

Sta. packing exhauster condensate outlet. m-4053 4068-3, 4068-5 Sta. generator feedpump suction. 5e p 4600-1, 4001-1 Sta. generator pump discharge. N Feedwater 4606-1, 4607-1, 4608-1, 4609-1 Vibration, ther. expansion Feedwater regulator inlet.

4606-2,-4607-2, 4608-2, 4609-2 Feedwater regulator outlet.

4606-3, 4607-3, 4608-3, 4609-3 Thermal expansion Feedwater upstream of flow nozzle.

i Vibration 18" check valve Downstream of 18" check valve.

f Thermal expansion Downstream of IS" shut-off valve.

Vibration, ther. expansion Start-Up feedpump discharge.

i Emergency 4081-1, 4082 Vibration Emergency feedpump suction.

Feedwater 4610-1,.4612-1 Emergency feedpump discharge.

Downstream of flov :ontrol valve.

4614-1, 4615-1, 4616-1, 4617-1 i

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, TABLE 3.9(B)-1 (Sheet 3 of 3) i System Line No. Parameter Measured Iocation/ Comments Main . Steam 4000-2, 4001-2, 4002-2, 4003-2 Vibration Containment penetration 4000-3, 4001-3,:4002-3, 4003-3 Thermal expansion Restraint upstream of MSIV 4000-11,4001-11,4002-9,'4003-9 Vibration Upstream of power operated relief valve 4004-11,4001-11,4002-9, 4003-9 Dynaanic '(transients) Power operated relief valve.

4000-12,4001-12,4002-10,4003-10 Vibration- Downstream of power operated relief valve 4000.-3, 4001-3, 4002-3, 4003-13 Thermal expansion Restraint downstream of main steam 1

isolation valve 4000-9 Vibration, ther. expansion Emergency feedpump turbine supply.

Diesel 4366-1, 4367-1, 4368-1, 4369-1 Vibration St'arting air

. Generator .4379-1, 4380-1 Fuel oil supply from day tank 4405-3, 4408-1 Vibration, ther. expansion Jacket cooling water to and from cooler i

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. ENCLOSURE D SEABROOK STATION POTENTIAL FOR STRESS CORROSION CRACKING IN PWR PIPING SYSTEMS The following review, encompassing a literature survey, service experier.ce, and fab,rication/ installation and operational requirements, provides convincing proof that stress corrosion cracking of stainless steel and carbon steel in primary and 1 ' - secondary pressure boundary piping systems is an unlikely event for the Seabrook Station. This review focused primarily on austentic stainless steel (types 304 and 316.

Carbon steel piping materials dre considered imune to stress corrosion cracking

basically because their overall corrosion rate in aqueous environments typical of PWR system service is high compared to the stainless steels and copper base alloys. A metal or alloy will be subject to the highly localized form of attack known as stress corrosion cracking only if the overall corrosion rate in the .

subject environment is low.

e In order for stress corrosion cracking to occur, three conditions involving stress, temperature and corrosive environment must occur simultaneously. Of these three, the corrosive environment is considered to be the key parameter since it is the most difficult to control. Stress and temperature are relatively fixed parameters although residual stresses from welding or operation may produce undesirable stress levels. Thus , to prevent stress corrosion cracking of stainless steel such as chlorides . fluorides, various frons of sulphur, caustics, 'and oxygen; and (2).

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' rigid control of water chemistry.

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Numerous measures are taken to prevent the introduction of contaminants into the system such as (1) assuring that asterials coming in contact with stainless during fabrication or operation do aot contain harmful levels of impurities such as in crayons, insulation, gaskets, and lubricants, (2) cleaning prior to heat treat-ment and welding, (3) final cleaning and capping prior to shipment to site, (4) use of high quality water (low chloride, fluorides, and controlled pH) for pre-operational flushing and testing, and (5) final cleaning of 0.D. surfaces followed by chloride and fluoride checks prior to preoperational testing.

In ' addition to the above, other requirements are imposed on asterial suppliers and component manufacturers to assure the use of optinua practices to control car-bide precipitation (sensitization) and cold work which are known to promote stress corrosion cracking. Precise heat treatment practices are required to be used'to promote optinua metallurginal structures for resisting strass corrosion cracking.

Procedures are reviewed to assure the use of effective but safe cleaning solutions.

Cold working (bending) after solution annealing is prohibited except for small diameter pipe. Heavy sensitization is avoided by prohibiting stress relieving af ter welding and control of heat input during veldi'1g. During plant operation, primary and secondary water chemistry is carefully monitored to assure compliance

.with specification requirements shown in Table 1. Note in porticular that oxygen levels are maintained for the primary side by a combination of hydrogen and hy-drazine an'd for the secondary side by hydrazine additions.

,i Except for incidents involving inadvertent chloride intrusions, no known stress l

corrosion failures have been reported in PWR operating plants.

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References:

1. Pacific Northwest Laboratories Report - Stress Corrosion in Nuclear Systems - March,1973 l

2. WPPSS - WNP-1/4 Intergranular Stress Corrosion Task Force r

Report - June 1980

3. Pacific Northwest Laboratories - Stress Corrosion in Nuclear Systems September 1975

4. NUREG - 0791 - Investigating and Evaluating Cracking Incidents in Pressurized Water Reactor - September 1980

5. Private telephone conversations with }i per sonnel.

6. Corrosion Engineering - Fontana & Green,1967.

7. NACE Corrosion Data Survey,1974.

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SEABROOK STATION WATER CHEMISTRY SPECIFICATIONS FOR LINES CONTAINInG ARBITRARY BREAKS OPER- MAX.

NO. OF ATING. H11ROGEN MAX. CHLORIDES &

ARBITRARY ASME PIPE TEMP. CollCEN. OKYGEN FLUORIDES pH pH CONTROL 02 CONTROL SYSTEM BREAKS CLASS MAT'L (Of) (cc/kg H,0) (ppa) (ppa) (@ 250C) AGENT AGENT REACTOR COOLANT 8 1 SS 557 25-50 0.005 0.15 4.2-10 Lith. Hydrox. H2 + Hydr.

SAFETY INJECTION 9 1 SS 557 25-50 0.005 0.15 4.2-10 Lith. Hydrox. H2 + Hydr.

CHEM. & VOLUME 8 1&2 SS 557 25-50 0.10 0.10 6.0-8.0 Lith. Hydrox. H2 + Hydr.

. C0!rrROL CHEM. & VOLUME 8 2 SS 490 -

0.10 0.10 6.0-8.0 Lith. Hydrox. H2 + Hydr.

CONTROL CHEM. & VOLUME 38 2 SS 120 25-50 0.10 0.10 6.0-8.0 Lith. Hydrox. H2 + Hydr.

CONTROL STEAM CENERATOR 35 2 CS 557 - - -

8.5-9.2 Morpholine Hydrazine BIDWDOWN MAIN STEAM 8 2 CS 557 -

0.005 -

8.8-9.2 Morpholine Hydrazine (PRIMARY LINES)

MAIN STEAM TO 2 2 CS 557 -

0.005 -

8.8-9.2 Morpholine Hydrazine l AUK. EQUIP.

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ENCLOSURE E SEABROOK STATION INTERMEDIATE BREAKS TO BE ELIMINATED EST. NO. OF DEVICES 1 ELIMINATED I NWtBER OF l BREAKS WHIP JET SYSTEM LOCATION

• PIPE SIZE EL M ED RESYEINTS SHIELDS REACr0tiCOOLANT IC (Ctat. Interior) 2" 4 0 0 l 3" 2 0 0 4" 2 0 0 SAFETY INJECTION IC (Ctat. Interior) 1-1/2" 7 0 0 6" 2 0 0 CHEM. & VOLUME IC (Ctat. Inte rior) 2" 8 0 0 CONTROL 3" 4 0 0 IC (Ctat. Annulus) 2" 9 0 0 3" 3 0 0 4" 2 0 O OC (Prim. Aux. Bldg.) 2" 11 0 0 3" 14 0 0 4 4" . 3 0 0 MAIN STEAM OC (MS&PW Pipe Chase) 6" 8 1 0 IC (Ctat. Interior) 32" 4 4 0 IC (Ctat. Annulus) 30" 4 10 4 STEAM CENERATOR OC (MS&PW Pipe Chase) 2" 2 0 ,

O BLOWDOWN 3" 5 0 0-i IC (Ctat. Interior) 2" 8 0 0

. 3" 11 0 1 IC (Ctat. Annulus) 3" 9 2 0 i

i TOTALS 122 17 5-

-* IC Inside Containment OC - Outside Containment

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ENCLOSURE F Proposed FSAR Changes - Section 3.6(B)

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SB 1 & 2 l FSAR 1

i . I i

l 3.6(B) PROTECTION AGAINST DYNAMIC EFFECTS ASSOCIATED WITH THE POSTULATED RUPTURE OF PIPING

a. Introduction

- General Design Criterion 4 of Appendix A to 10CFR50 requires th.at structuras, systems and components important to safety be protected against the dynamic of facts of piping failures. This section dis-cusses the design base.s and design measures employed to ensure that all essential structures, systems and components located inside and outside the reactor containment, including the cougnonent's of the reactor coolant pressure boundary, have been adequately protected against the effects of possible blowdown jet end reactive forces and pipe whips resulting from postulated rupture of piping located both inside and outside of containment.

The required information is furnished in two sections:

1. Sections 3.6(B).1 and 3.6(B).2 and respective subsections address all piping systems inside and outside containment, exclusive of the reactor coolant loop piping.

2. Section 3.6(N).2 and subsections, which have been furnished by the NSSS supplier, address only the reactor coolanc loop piping inside the reactor containment and ther loops' support

( system.

The criteria used in postulating pipe rupture and leakage locations in high and moderate energy piping systems located outside containment correspond with the guidance set forth in the NRC's Branch Technical Position APCSB 3-1. -

The criteria employed for identifying high energy fluid piping, and for postulating pipe break locations, break orientations and break flow areas inside cont.inment are consistent with the criteria.

. established in Regulatory Guide- 1.46, " Protection Against Pipe Whip Inside Containment".- The Westinghouse Topical Baport, WCA?-8082,

" Pipe Break for the LOCA Analysis of the Westinghouse Primary Coolant Loop", is referenced as the basis concluding that the reactor coolant piping system will provide an equivalent level of protection, as recomended in Regulatory Guide 1.46. The Seabrook Station coolant system piping is consi. stent with the design considered in WCAP-8082,

. which has been approved by the NRC Staff.

b. Definitions Hish Energy Fluid Systems or Lines - Fluid systems or lines which, during normal plant conditions, are either in operation or main-1:ained pressurised under conditions where either or both of the following conditions are met 3.6(B)-1

---..-..--_-___.n-

~ .

.. s SB 1 & 2 FSAR

- Maximum operating temperature exceeds 2000F, 3

- Maximum operating pressure exceeds 275 pois.

Moderate ".nergy Fluid Systems or Lines - Fluid systems or lines

. which dutsag normal plant conditions, are either in operation or maintained pressurised above atmospheric pressure under conditions where both the following conditions are met

- Maximum operating temperature is 200'F or less, and

- Maximum operating pressure is 275 peig or less.

1 Normal Plant Conditions - Plant operating conditions during reactor I start-up, operation at power, hot standby or reactor cooldown to cold shutdown conditions.

! Upset Plant Conditions - Plant operating conditions during s;.tes transient conditions that may occur with moderate frequency during plant service life and are anticipated, operational occurrences, but not during system testing. -

t Essential Systems and Components - Systems and components required to shutdown the reactor and mitigate the consequences of a postulated ,

• - piping failure without offsite power. .

Postulated Piping Failure - Longitudinal and circumferential breaks 1- in high-energy fluid system piping and through-wall leakage cracks I in moderate energy fluid system piping posultated according to the provisions of Subsection 3.6(S).2 below. .

! SA - Allowable stress range for thermal expansion as defined in subarticle Nc3600 of the ASME Code,Section III, 1971 Edition,

> with Addenda up to and including Winter, 1972.

i

, Sg - Allowable stress at maximum temperature.

i Sg - Design stress intensity defined in subarticle NB-3600 of the ASME Code.

Single Active Component Failure - Malfunction or loss of function

• of a component of an electrical or fluid system. A failure of

, ~

an active component of a fluid system is not considered to include loss of. component structural integrity. 1he direct consequences of a single active component failure are considered to be part of the single failure.

Terminal Ends - gueremities of piping runs that connect to struc-

~tures, components.(vessels, tumps, valves) or pipe anchors that act as rigid constraints to. thermal expansion. A branch connection to a main piping run is a terminal stad_of_the. branch run.

3.6(3)-2 3 o

h j P.

h,- ,

SB 1 & 1 Amendment 47 FSAR September 1982 Intersections of runs of comparable size and fixity need not be considered terminal ends when so justified by the analysis. Terminal ends, for the purpose of postulating breaks, should be selected at points located 1 5.ediately outside or beyond the required pipe whip

. restraints located inside and outside containment at penetration areas. In piping runs that are maintained pressurized during normal plant conditions for only a portion of the run (up to the first normally closed valve), a terminal end of such runs is the piping' connection to this first valve.

Five Degree Restraint - A device which restrains the pipe in such a way that only axial loads can be transmitted past the restraint.

3!6(B).1 Postulated Piping Failures in Fluid Systems Outside of Containment 3.6(B).1.1 Design Bases

a. Equipment Potentially Susceptible to Effects of Piping Failure Systems. and components important to plant safety or shutt' m (herein referred to as essential systems and components), located pr nimate to high or moderate energy piping systems, and which are potentially susceptible to the consequences of piping systems breaks and cracks,

, are listed'in Table 3.6(B)-1. The identification of this equipment i 'is related to predetermined piping failure locations, determined in accordance with the methodology discussed in Section 3.6(B)'.2.

Figures 3.6(B)-1, 3.6(B)-2-and 3.6(B)-5 through 3.6(B)-38b show the locations of the postulated pipe ruptures, locations of pipe whip restraints, and relative locations of potentially affected essential componects.

The limiting acceptat % conditions for, and the measures taken to- U protect the essential systems and components, are listed in the.

. pipe rupture analysis summary sheets in Appendix 3A.

b. Design Crit;eria for Protection Against Piping Failures The following criteria were utilised as gui lines during the station design 'to ' assure the protection of essential equipment t .from potential failure of nearby piping systems:

m

1. Piping Systems Containing High Energy Fluids Piping s'ystems'are to be isolated by adequate physical

a. .

separation,.and remotely located from essential systems and components required to shut down the reactor safely

.and maintain the station in a cold' shutdown condition.' j 3.6(B)-3.

SB 1 & 2 FSAR 4

b. Where isolation by remote location is considered imprac-tical, piping systems, or portioes of the systems, are enclosed within structures suitably designed to protect adjoining essential systems and components from postulated piping failures within the enclosure.

c. Where both isolation by remote location and enclosure in protective structures are considered impractical, the piping systems or portions of the systems are provided with restraints and protective measures such that the operability and integrity of the structures, safety systems and components would not be impaired.

i' d. Protective enclosures for the piping systems are designed as seismic Category I structures capable of withstanding the combined ef fects of a postulated pipe break, the dynamic ef fects of pipe whipping, the jet impingement forces and the compartment pressurization resulting from discharging fluids in combination with the specified seismic event of the Safe Shutdown Earthquake and normal. operating load.

e. - Piping systems containing high-energy fluids are designed so that the ef fects of a single postulated pipe break will not initiate unacceptable failures of other pipes or compon-ents. In addition, any systems, or portions of systems, that are designed to mitigate the consequences of a postula-ted pipe failure and place the reactor in the cold shutdown condition, are provided with design features that will

. ensure the performance of their pafety function, assuming a single active component failure. .

f. For a postulated pipe failure, an escape of steam, water F and heat from structures enclosing the piping shall not preclude: 1) the accessibility to surrounding areas

important to the safe control of reactor operations, 2) the habitability of the control room, 3) the ability of instrumentation, electric power supplies, and components and controls to initiate, actuate and complete a safety

,. action. In this regard, a loss of redundancy is considered

[> permissible, but not the loss of function.

' g. The design measures employed for the protection of struc-tures, systems, and components important to safety will not prevent inservice examinations of ASME. Class 2 and 3  !

pressure-retaining components, as required by the rulsa ~ '

of ASME B&PV Code,.Section XI, " Inservice Inspection of Nuclear Power Plant Components".

i 3.6(5)-4

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.- +

SB 1 & 2 Amen Lent 44 FSAR February 1982

2. Piping Systems Containing Moderate-Energy Fluids

a. Piping systems containing moderate-energy fluids are designed to cosply with the criteria applied to high-energy fluid piping systems, as . stated above, except that the piping is postulated to develop a limited-size through-wall leakage crack instead of a pipe break.

b. For each postulated leakage condition, design measures are provided that will provide protection from the ef fects of the resulting water spray and flooding.

3. Exceptions Measures for protection against pipe whipping or jet impingement resulting from.the breaks pcstulated in Subst: tion 3.6(B).2 are not provided for piping where any of the following applies

a. piping is physically separated or isolated' from any essential system or component necessary for plant safety or shutdown by means'of barriers, or is' restrained from-whipping by plant design features such as encaseneSt.

b. The broken pipe cannot cause unacceptable. damage to

~L any essential system or component.

c. The energy associated with the whipping, pipe'can be-L demonstrated to be insufficient to impair to an unacceptable

! level the safety function of an essential system 'or component. For example,'a whipping pipe is considered .

unable to rupture an impacted pipe of equal or larger -

nominal pipe size and equal or heavier wall thickness.

l 3.6(B).1.2 Description l

L High energy lines are listed in Table 3.6(B)-2; moderate energy. lines include a11'other lines- not listed in this table. For a complete listing of

all high 'and moderate energy lines, see the Seabrook line designation -

tabulation, Appendix 35.

Relative 'to possible dynamic effects of pipe failure ivi the -Seabrook plant '

layout, essential systems and components are protected 'from the dynamic ~

l' effects of rupture of high' energy piping primarily by separation and i

redundancy. Routing of high energy lines has been arranged to provide the maxiums amount of protection by utilising plant structural ' elements, such as -

,, walls or columns, and routing the high energy lines'as far as practicable

! from essential components. - In cases where separation is not possible, pipe whip restraints are used to prevent uncontrolled whipping of the high energy

.; piping. Compartments-of primary interest are the containment' structure,-the

. main' steam.and feedwater pipe tunnels, and the containment enclosure building and its' attached cospartments.

44' 3.6(B)-5

• v *-c--'_ e w-w-*= -+m v-,rr ei,m-og..,y-g =,,co, , , . , , , i..,.,,. , , , ,,,,_.g __ ,., , ,. .

9,,

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SB 1 & 2 Amendment 44 FSAR February 1982 In the case of the control room, there are no high energy lines in the area

' which could affect habitability as a result of pipe whip. 'Ihe main steam

and feedwater. lines on the pipe bridge are separated from the control roon

. by the seismic Category I control building wall, which has been reinforced to proteict the control room environment from postulated breaks in, or whip loads from, the main steam and feedwater lines. Control room habitability systems are discussed in Section L4.

'the high energy lines outside containment whose breaks or cracks could have the greatest effect on 'envircoment within the structures housing components essential for safe plant shutdown are listed below:

1. Primary Auxiliary Building

a. Steam generator blowdown lines

b. Auxiliary steam and condensate lines

c. Chemical and volume control system letdown line

d. Hot wat.er heating lines

2. Puel Storage Building

- a. Bot water heating lines

3. - Containment saclosure and Connected Buildings

, s. Bot. water heating lines

4. Main Steam and Feedwater Pipe Chase

a. Main steam lines

! b. Feedwater lines i 5. Diesel Generator Building

! -s. Bot water heating line ,

f

6. Control Building 1

a. . Hot water heating line

.7. Emergency Feedwater Pumphouse I

a. . Hoc water heating line

.8. Service Water Pumphouse l

a. Bot water heating lines Table 3.6(5)-1 lists the essential components located outside containment

. which are potentially susceptible to the effects of high and moderate energy piping ruptures.

44 3.6(R)

• l

4, ' .

ji SB 1 & 2 Amendment 45

FSAR June 1982 s.

i Table 3.9(B)-23 tabulates all active valves, including those in zones outside containment, whose function must be unimpaired in the event of a pipe rupture accident.

3.6(B).1.3 Safety Evaluation l Appendix 31 summarizes the environments in each of the structures housing essential components which result from postulated supture of the high energy lines. .

An analysis of the potential effects of missiles is discussed in Section 3.5.

Pressare rise analyses of structures and compartments due to piping breaks are discussed in Sections 3.7 and 6.2.

! A summary of the results of failure or leakage from high energy or moderate

' energy lines on nearby safety systems (failure modes and effects analysis),

oresented in Appendix 3A, verifies that the consequences of failures o'f high and moderate energy lines will not affect the ability of the plant to be shutdown safely. The analyses considered the effects of single active component failures occurring in required systems concurrent with the -

postulated event.

44 3.6(B).2 Determination of Break Locations and Dynamic Effects Associated with the Postulated Rupture of Piping

-J This section describes the design bases for locating postulated breaks and cracks in piping situated both inside and outside of containment, the-proce-dures used . to define the jet thrust reaction at the break or cr.ack location, and the jet impingement loading on adjacent safety-related structures, equip-ment, systems and components.

• 3.6(B).2.1 Criteria Used to Define Break and Crack Location and Configuration The criteria employed for defining break and crack locations and configurations in primary loop' piping inside containment is discussed in Subsection 3.6(N).2.1.

• This section discusses all other piping.

1 The criteria -are provided for those high and moderate energy piping systems for ;Sich separation or ' enclosure cannot -be achieved.

! a. 'High Energy Piping

1. ASME Section III Code Class I Pipi g Breaks were postulated to occur at the following locations in each piping run or branch run

/

(a) Terminal ends.

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FSAR June 1982 (b) At all intermediate locations where the maximum stress range as calculated by Eq(10) and. either (12) or 13) exceeded 2.4 Sm; based upon Subsection NB-3600 of '

Section III of the ASME B&PV Code,1977 Edition, up to and including the Summer,1979 Addenda. The load-ings considered were all Level A and B loads including .

an operating basis earthquake.

(c) At all intermediate locations where the cumulative j usage factor derived from the piping fatigue analysis nder the loads described above exceeded 0.1.

A A

, 2. ASME Section III Code Class 2 and'3 Piping Breaks were postulated to occur at the following locations for each piping run or branch run which does not penetrate the containment:

(a) Terminal ends.

(b) Any intermediate locations between terminal ends where - -

{

either circumferential, or longitudinal stresses derived by -

elastic methods _ under the . loadings associated with opera- .

tional plant condicio s and an operating basis earthquake w:

excee_d 0.8 (S +S) A p.~

= =_

See below.for piping penetrating the containment. .

3. Non-Nuclear Piping

' Breaks in non-nuclear piping were postulated at the following locations in each piping run or branch runt D.) - Terminal ends.-

(b) 'Each structural. discontinuity (elbows,-tees, reducers,

• valves). _

4.. Piping Penetrating Containment' n

.. All piping penetrating the contaissent. is ASME Section III, Code Class 2. All high energy, high tenperature lines pene-

. trating containment make use.of integrally forged -flued heads.

A 4.etailed discussion of the design'of these flued heads it '

given in Reference 1.,

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SB 1 & 2 Amendment 49 FSAR May 1983 For main steam and feedwater piping penet rating containment, no breaks were postulated between the first whip restraint inside the containment and the five-degree restraint outside ,

containment, since the following conditions are met: -J (a) The maximum stresses, as calculated by the sum of equa- ~

tions (9) and (10) in paragraph NC-3652 of Section III*

of the Code, considering normal and upset conditions and an OBE event, do not exceed 0.8 (1.2 Sh + SA)*

(b) The maximum stress, as calculated by equation 9 of paragraph N NC-3652 under the loadings resulting from a postulated piping failure of fluid system piping beyond these portions of thu piping, does not exceed 1.8 Sh .

(c) The number of circumferential and longitudinal weld points in piping have been minimized.

Al (d) The length of those. portions of piping have been reduced ,

to the minimum practical.

(e) The design of pipe restraints and anchors have not generally j required welding directly to the outer surface of the pipe. -

Where anchors or restraints were needed, forgings were used to avoid welding to the surface of the pipe. Where lugs .  ;

were used for riser clamps, a detailed analysis was made ,

to assure compliance with stress limits stated above. j 3

Lug attachments welded to Class 2 and 3 pipes are a qualified by a procedure whose methodology is equivalent to, but more conservative than, that preser.ted in Code (5 Case N-318. -

Local stress levels in the pipe resulting from applied 3 lug loads are obtained by multiplying the nominal stress 3 in the lug at the lug / pipe interface by the appropriate f B or C index (as defined in Code Case N-318) for each 3 individual loading condition. The local stresses are . Ji superimposed upon the general pipe stress as determined- ('

from program ADLPIPE to establish the total stress level l

in the pipe for that loading condition. .

Loading conditions required to be considered for Plant Normal, Plant Upset, Plant Emergency, and Plant Faulted Operating Condition are defined (per appropriate FSAR ]

section), and total stress in the pipe is obtained from j summing the stresses for each individuel loading condition that must be considered.

4 a

Local stress levels determined using B indices are added 8 to the general stress levels from ADLPIPE and this sua is

'E 4T

• For piping design, the applicable Code edition is the 1971 Cod'e, with j addenda up to and in:1uding Winter 1972.

• i e

3.6(B)-8

p.

s SB 1 & 2 Amendment 49 FSAR May 1983 compared against allowable limits to demonstrate struc-tural integrity. For the pipe wall, local stress levels determined using C indices are added to the general stress levels from ADLPIPE, and this sua is compared against the allowable range of stress (S +Sa)*

h Finally, weld stress is evaluated considering the absolute sua from all loads, independent of the operating condition, and compared against allowable stress from Table NF329.1-1, Subsection NF, ASME III.

(F The terminal ends of these portions of piping are considered to originate at a point adjacent to the restraints located inside and outside containment which are:

(a) Located reasonably cloce to the isolation valve.

(b) Capable of withstanding the loadings resulting from a postulated pipe rupture beyond this portion of the piping, such that neither valve operability nor the leaktight integrity of the containment is impaired.

Details of typical containment piping penetrations showing location of process pipe welds, anchorage and points of dis-continuity are shown in Figures 3.6(B)-3 and 3.6(B)-4.

Inservice inspection of Code Class 2 components, including penetrations, is discussed in Section 6.6.

3.6(B)-8a

. . - - -. w

3t .

4 .

SB 1 & 2 FSAR

b. Moderate Energy Piping Through-wall leakage cracks are postulated to occur in seismic Category I and non-nuclear fluid system piping located within or outside and adjacent to protective structures, with the following exceptions:

't

1. Fluid system piping between isolation valves, provided they meet the requirements of ASME Section III, subarticle NE-1120, and are designed such that the maximum stress range does not exceed 0.4 (1.2 Sh + SA) for ASME Class 2 piping.

2. Fluid system piping located in an area in which a break in a high energy system is postulated, provided a break in a moder-ate energy fluid system does not result in a more limiting condition than the break in the high-energy system.

3. Seismic category I fluid systems in which the maximum stress range in Class 2 or Class 3 or non-nuclear piping is less than 0.4 (1.2 Sh + 8A)*

The. cracks were postulated to occur in those locations that result in the maximum effects from flood ' spraying or flooding.

( Through-wall leakage cracks were postulated instead of breaks  ;

in the piping of those systems that qualify as high energy fluid systems for only short operational periods, but qualify as moderate energy fluid systems for the' major operational period. These systems include containment apray, safety infection and residual--

heat removal.

An operational period is considered short if the fraction of time that the system operates within the pressure-temperature limits specified for a high-energy system is 2 percent' or less of the time that it operates as a moderate energy fluid ' system.

c. - Type of Breaks The following types of breaks and cracks were postulated to occur in high-energy and moderate energy piping as described below:

1.. High Energy Piping'

-(a) Circumferential breaks were postulated to occur in high-energy piping larger than one inch nominal pipe size.

Circumferential breaks are presumed to occur at.right angles to the axis of the pipe, to completely sever-the pipe within one millisecond and to separate the

'3.6(B)-9 L __: _ s _ __

8 s

SB 1 & 2 FSAR ends of the pipe to permit a flow area equal to the 1 flow area of the pipe. See Subsection 3.6(N).2.1 for exception for RCS' piping. ,

(b) Longitudinal splits were postulated to occur in high-energy piping four inches or larger nominal pipe size.

The area of the longitudinal split was assumed to be equal to the flow area of t'he pipe, and the split was assumed to be parallel to the axis of the pipe. Crack orientation was selected on the basis of the most serious effects.

(c) Certain longitudinal break orientations were excluded on the basis of the state of stress at the location considered. Specifically, where the maximum stress range in the axial direction is at least one and a half times that in the circumferential direction considering upset plant conditions, then only a circumferential break was postulated.

(d) Longitudinal breaks were not postulated to occur in piping at terminal ends where the piping contains no longitudinal welds or at intermediate locations where the criteria for a minimum number of break locations were satisfied. ,

2. Moderate Enerav Pipina  ;

Through-wall leakage cracks were postulated to occur in moderate energy piping larger than gne inch nominal _, pipe diameter, and to have openings up to half the pipe wall thic,one-half, kness. pipe diameter by up'to one-

d. " Jet Lapinsement Force-Criteria r The criteria used to evaluate jet impingement forces are described in ~ Appendix 3C, Procedure for Evaluation of' Jet Impinsement Loads -

from Himh Eneray Pipina Failures. After-jet forces imposed on structures or equipment have been determined, the' capacity-of the structures or equipment to support these loads without desage '

~

-is' investigated using conservative methods. . Jet impingement loads are considered to be faulted condition loads'and are so evaluated.

! 3.6(5).2.'2 ~ Analytical Methods to Define Forcina Functions and Response Models This 'section presents a description of the methods used- to define forcing

functions.and response models for pipe whip saalysis. For RC Loop piping, sea subsection 3.6(N).2.2.

4

-3.6(B)-10 LA . -

+

c, .

=

SB 1 & 2 FSAR 1 i

i l

a. Forcing Functions

{

1. Time Dependence The normal steady-state operating conditions of the plant were assumed prior to postulating a pipe rupture.

When circumferential ruptures were postulated, the through-wall crack was assumed to develop across the circumference of the pipe instantaneously, and the ruptured pipe was assumed to separate to the full flow area (e.g., double ended rupture) in one millisecond.

When longitudinal ruptures were postulated, the time for a longitudinal rupture to open to its maximum length was assumed to be one millisecond.

2. System Friction Loss Dependence In calculating forces acting on the piping system, full credit may be taken for any restrictions or line losses between the break and the pressure reservoir (s). For Seabrook, however, the simplified conservative analyses did not consider friction losses.

~

3. Closed-Ended Lines For the closed end of a line (dead end or normally-closed valves) when it was obviour that the fluid dynamic forces could not be sustair.ed, pipe whip response was not considered.

4. Discharge Coefficient For flashing or nonflashing flow through circumferential and longitudinal breaks, a Jischarge coef ficient, Cd , of 1.0 was used to determine the flow rate through the break,

=

Q Cd AV where: Q = flow rate through break A = break flow area V = velocity

. Cd= discharge coefficient

5. Options The jet thrust reaction, forcing function at the break , locations may be generated from a dynamic fluid system model. However,

- a simplified approach was used, applying a maximum thrust value defined for discharge of non-flashing liquid or for discharge of saturated or superheated vapor ass 3.6(B)-11

r

• E

. f SB 1 & 2 FSAR T =

Kg (K2 Po - Pa) A Where T represents the thrust force Po represents vessel pressure (psig) J A. represents break flow area Kg,K2 Y8 presents thrust coefficients P o pressure of ambient outside system (psis)

Representative values of K reported by Moody (2) ares (a) Saturated and superheated vapor, Kg = 1, K2 = 1.26 (b) Subcooled liquid - non flashing, Kg = 2, K2"1 Other values may be used when substantiated; however, the Moody coefficients have been used for pipe rupture analysis on this project.

For circumferential breaks, direction of thrust was assumed to be along the centerline of the pipe in a direction opposite the jet flow.

For longitudinal breaks,' thrust was assumed in a direction opposite jet flow.

For all breaks, maximum thrust was assumed to occur within 1 millisecond and to be a steady state condition thereaf ter.

3.6(B).2.3 Dynamic Analysis Methods to Verify Intearity and Operability

a. Dynamic Analysis Methods The analysis of a, piping system and its restraints under pipe rup-ture conditions requires consideration of the ' interaction effects of both piping and restraints. The magnitus; and distribution of loadings depends upon such parameters as the restraint los'd-deflec-tion gaps between piping and restraint, piping flexibility, break location, etc.

1. Eneray-Balance Analysis In this method, kinetic energy generated during the first

• quarter cycle movement of the ruptured pipe is -imparted to the piping / restraint system through impact and is converted into equivalent strain energy. Deformations of 'the pipe and the restraint are compatible with the level of absorbed energy. .

For applications where. pipe rebound may occur upon impact of the rgstraint, an additional amplification factor 1.5 was used to establish the magnitude of the forcing function in order to '

determine the maximum reactor force'of the restraint after the first quarter cycle of response. Amplification factors other 3.6(B)-12 l l

1

c' O .

+ .

3+ .

SB 1 & 2 Amendment 45 FSAR June 1982 than 1.5 may be used if justified by more detailed dynamic analysis. Appendix 3D presents the procedure used for calcula-ting piping / restraint system loads by the energy balance method.

2. Quasi-Static Analysis In order to satisfy the system capability requirements, a dynamic analysis is the preferred method. In the event a dynamic analysis is not possible or feasible for a piping and restraint system, a quasi-static analysis may be possible if it is shown to give more conservative results.

'1%ro design considerations are. required as in the dynamic analysis. The system must be capable of supporting both the dynamic and the steady-state blowdown loads.

If a constant, conservative blowdown force is assumed, the system is independent of the dynamic event occurrence time.

Since the dynamic inertia ef fects are therefore unknown, the load-sharing relationship between the pipe and the restraints, etc., cannot be determined.

The jet force can be represented by a conservatively. amplified static loading, and the ruptured system is analysad statically.

The amplification factor that is used to establish the magnitude of the forcing function is a conservative value obtained by com-parison with the factors derived from detailed dynamic analysis performed on comparable systems. Appendix 3E presents the procedure used for calculating piping / restraint system loads by the equivalent static analysis method.

b. Desian Considerations Pipe rupture locations and orientation were determined as. stated

. in Subsections 3.6(5).2 and 3.6(N).2. Effects of each rupture were evaluated and, if necessary, whip restraints were located to protect the essential systems or components.

Pipe whip restraints for the reactor coolant system piping were designed to limit the motion of the ruptured piping and' to restrict the flow area of the breaks in order to limit jet thrust forces..

For other Code Class 1, 2 or 3 piping, the whip . restraints were' designed to prevent unrestrained whipping of the piping, but at the same time permit unrestrained thermal movement of the piping.

In some cases, such as on the main steen and feedwater lines in the penetrations and piping tunnel areas, it was appropriate to use pipe whip restraint steel as intervening elements or as supplementary steel for the attachment of seismic' restraints.

Wherever this was done, the boundary between PWR stool and ASME ~

Class.2-seismic restraints was defined by showing the.1Mnl steel and'the seismic restraints on' separate fabrication'and-installation Ldrawings. A11. Code Class supports and restraints are identified on the drawings as N-steep Items.

49 3.6(B)-13

• e

. A*

SB 1 & 2 Amendment 45 FSAR June 1982 After the whip restraints were located, the following information was developed (a) Jet thrust force (b) Pipe seismic displacement *

(c) Pipe thermal displacement (d) Maximum allowable pipe travel (e) Insulation thickness Minimum gap between pipe and restraint is determined from consider-ation of (b), (c) and (e) above. Restraint stiffness is determined from (a) and (d). Where the whip restraint is also a seismic restraint, the following values for stiffness were used:

(a) For piping larger than 8" nominal diameter 106 or 107 lb/ inch.

(b) For piping from 24" to 6" nominal diameter: 105 , 106 or 107 lb/ inch.

(c) For piping up to 2" nowinal' diameter: 104 , 105 or 106 lb/ineh.

Analyses of representative piping configurations show that a change in stiffness of one order of magnitude in either direction will not change pipe stresses significantly, so that the designers generally used the lowest values for stiffness in the ranges given, unless pipe deflection is the critical parameter.

In the design of the' whip restraints, the energy absorption capacity of the pipe was not considered. For structural steel whip restraint-members, when elasto-plastic design methods were used, the stress l.

Ibsit for design is 90% of the yield stress value showa in the 44 AISC Steel Construction Manual. When elastic design machods were used, the stress 1 Lait for design is 63% of yield.

In general, for pipe whip restraints, elastic design criteria were used.. In cases where elasto-plastic design criteria were used, and the pipe whip restraint was also used as an intervening element i for attachment of pipe supports or restraints,- it was first designed as s' whip restraint using elasto plastic criteria, and was then checked to verify its ability to support the pipe support / restraint loads using elasto plastic criteria.

45 In order to determine the adequacy of a system, including pipes and restraints, following postulated-' pipe rupture accident, two design considerations must be evaluated:

1. Dynamic Response Upon the occurrence of the postulated pipe rupture, the system of pipe restraints structure, etc., will respond dynamically to the suddenly applied blowdown thrust, Fg (t). This thrust 3.6(B)-14 L

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SB 1 & 2 FSAR will move the pipe so that it impacts against the restraint with an impulse equal to the pipe mass times the impact velocity.

8 The product of blowdown thrust, Fg, and the time after this impact until motion ceases, t, will be an additional impulse on the system.

2. Static Equilibrium Following the occurrences of the dynamic event (when motion ceases), the system must be able to support the active applied i forces (the blowdown thrust). Therefore, the system must satisfy the requirements of a static analysis.

i- For a conservative static analysis, each component (i.e.,

pipe, restraint) is capable of supporting the total load (or it is shown which component (s) support the load). When this is done and the componente will have the load capacity to support the steady-state blowdown, the system design is cocsidered to be conservative.

5

c. Design Loading Combinations Pipes which have been identified in accordance with Subsection

,- 3.6(B).1 as those which could cause adverse-effects due.to pipe i movement were provided with means of controlling their motion, if barriers, separation, or some other- acceptable method was not used for ' protection.

>a

'~ .

1. Piping

i. The pipe will be subjected to dynamic forces following a ~

J? . postulated pipe _ break event. An evaluation was made to insure.

that the load carrying capability of the pipe is not exceeded.

(a) Adequacy Requirements In order for the motion of. pipes to be controlled, it is necessary that the load on the pipe during the dynamic event be less than the load capacity .of _ the pipe. The

' dynamic _ load capacity of the pipe can'be determined by test or by a suitable analytical model.

Without testing, the load capacity'for analysis xis limited to the bending associated with .a maximum fiber strain of.

50 percent of the ultimate. strain of the pipe material.

Ultimate strain is defined as the value of _ strain whichi corresponds to the maximum stress on the engineering stress-strain diagram. 'For a given material where there

[

is a range of values due to statistical variation,' the l guaranteed minimum value of ultimate strain.is used.

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.e SB 1 & 2 Amendment 49 FSAR May 1983 o-f The second requirement, to insure that the motion of pipes is controlled, is for the moment-carrying capacity of the pipe to be greater than the applied moment af ter the occurrence of the dynamic event. An ultimate moment, Mu, is defined as the maximum moment that the pipe cross section can support. If the applied moment, M , defined as a force times lever are is numerically smaller than Mu , uncontrolled rotation of the pipe will not occur.

(b) Material Properties Careful consideration was given to the piping material properties used. The rapid loading conditions due to pipe rupture may require the consideration of high strain-rate effects on material behavior, in addition to strain-hardening considerations.Section III of the ASME Code

-provides tabulations of material properties which may be used for some evaluations. The values of yield strength at temperature, for example, are minimum values for static loadings. . In calculating the allowable span distance -

between restraints, use of minimum values is conservative.

In calculating the maximum moment which could be exerted on an anchor point, the use of minimum values would be unconservative. The applied moments, Ma, during the steady state blowdown will be no greater than 90 percent of the moment capacity of the pipe based on minimum pipe material properties determined from test, applicable

! specifications, or~ codes.

V

2. Restraints For BOP piping, pipe whip restraints are provided to maintain the motion of the typtured pipe within controlled limits..

The limit of pipe motion is the area within which no' essential

. component would be affected.by impact or jet impingement.

49

. The primary function of a restraint-is to control pipe motion upon the occurrence of a pipe rupture. - As used in this context, a restraint is considered to be different from a support. In certain instances, a restraint may also function as a support, and is designed according to the. faulted conditions-rules of

-Subsection NF of ASME Code,Section III.

Typical whip restraints consist of heavy structural members extending from the building structure to the pipe, and a structural box or a series of U-bol,ts which surround the

. pipe to-restrain lateral motion. Unless the restraint acts also as a thermal or seismic restraint, contact between the pipe and the whip restraint is prevented by means of a suitable air gap. Where it is necessary to reduce pipe impact loads on critical stractures, energy-absorbing devices are used between the pipe and the structure.

3.6(B)-16

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SB 1 & 2 Amendment 49 FSAR May 1983 (a) Design Limits Pipe restraints' are designed for one-time usage, and as

such may be allowed to have greater distortion, plastic F

' deformation, etc., than normally permitted for support design.

f -

l i For elasto plastic system analysis, wherein the effects of I i

, strain-rate, strain-hardening, etc. , are included, the 41 permanent strain in metallic ductile materials is limited i'

to 50 percent of the uniform strain. When a crushable energy-absorbing material is used, the deformatioe is limited to that corresponding to 50 percent of the total j- energy absorption capacity of the crushable material.

(b) Material Properties Materials selected for restraints designed to significant strain levels must have well-known dynamic mechanical' properties. Assurance was provided by material inspection.

3.6(B,).2.4 Guard Pipe Assembly Design Criteria Guard pipes are employed in the following locations: a) on the main steam and feedwater lines to prevent pressurization of the annulus in the event of

, a pipe rupture; b) on the main steam lines just north of the main steam and j

.feedwater pipe chase to protect the main steam isolation valves from missile damage due to jee Lapingement of the pipe _ chase ' north wall; and c). on the

' main steam line in the pipe bridge area.to protect the control building wall from jet Lapingement. The guard pipes in the containment enclosure were designed as a part of the flued head penetrations for the main steam and .

~ feedwater lines.

4T Adiscbestonofthedesigncriteriaandanalysisofthehighenergycontain-ment penetrations is given in Reference 1. The Lpurpose of the penetration.

assemblies is to permit penetration of the containment by process pipes with -

out -jeopardizing containment integrity. >Where they are _used as guard pipes, they also serve to prevent overpressurization of the containment enclosure and annulus. No other lines in this area require guard pipes.

In general, .all process pipes penetrating containment are seadless. 'Penetra-tion assemblies for large high temperature lines are integrally forged flued head design. Penetration assemblies for cold lines or small lines (under

-1" nominal diameter) are seamless pipe welded to. flat plate heads which.

are in turn'velded to sleeves anchored in the containment structure. All penetration sleeves are' seal' welded to the steel containment _ liner, and' leak test channels are provided for periodic testing of containment leak-tightness.

'There are no process pipe welds located within the protective asceablies,. ~~

with the exception of the 2" diameter steam generator blowdown lines. The process pipe welds for.these lines do not require inservice inspection (Ref. 1WC-1220d of ASME XI).

Moment-limiting restraints have been provided for all penetrations carrying

~

. chigh energy piping in order!to maintain process pipe stress levels below the limits defined in Equation 8 of NC3652 for maximum stress range considering all . upset design transients in ' combination with OBE.

3.6(B)-17 e _ _. _ . _ _ _ _- . . ~ - --- - - i

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. 'a f SB 1 & 2 FSAR 3.6(B).2.5 Material to be Submitted for the Operating License Review The results of the analyses performed on high and moderate energy piping systems and their supports to determine the loadings from postulated pipe breaks and cracks, as well as the procedures used, are presented in the followi.ng appendices:

s.

Appendix 3A Pipe Break Analysis Summary Sheets Appendix 35 Line Designation Tabulation (Seabrook Line List)

Appendix 3C Procedure for Evaluating Jet Impingement Ioads from High Energy Piping Failures t

Procedure for Calculating Elasto-Plastica 11y Designed i

Appendix 3D Pipe Whip Restraint Loads by the Energy Balance Method Appendix 3E Procedure for Calculating Elastica 11y-Designed Pipe Whip Restraint Loads by Equivalent Static Analysis Method 3.6(B).3 -References

1. " Stress Report for High Energy Piping Penetrations for PSNH-Seabrook Station Units 1 and 2", Stress Report No. 9763-325-1, dated' September,

~

g.

-1976, United Engineers & Constructors Inc.

2. Moody, F.J. , " Prediction 'of Blowdown Thrust and Jet. Forces",

Paper Nc. 69-HT-31, presented at the ASME-AICHE Heat Transfer Conference, Minneapolis, Minnesota, August 3-6, 1969 l

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