ML20235E940

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Requests Analyses & Other Relevant Info Needed to Determine Consequences of Postulated Pipe Failure Outside Containment Structures,Including Rupture of Main Steam or Feedwater Line
ML20235E940
Person / Time
Site: Quad Cities, 05000000
Issue date: 12/18/1972
From: Giambusso A
US ATOMIC ENERGY COMMISSION (AEC)
To: Brian Lee
COMMONWEALTH EDISON CO.
Shared Package
ML20235B311 List: ... further results
References
FOIA-87-111 NUDOCS 8709280337
Download: ML20235E940 (14)
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DE.C 181972, i

Beskat Nos.30-165 I

li esamenwealth satsen eenpent ATDis Ier. W rea Lee, Jr.

I desistaat to the President Poes Offias Sea 747 ekisage, 1111meds 40690 l Seatlement' I

The Regulatory staff's seatinuias reMew of reester power plant safety h indiestes that the eensequeness of postulated pipe failures entside of the oestaiassat structuso, saaleding the ruptues of a main steam er feedwater lins, need to be adeguately desumented and smalysed W 11eensees and applianats, and evaluated by the staff as seen as j

possible. Criterian No. 4 of the Commisstem's Senieral Design Crtteria, j listed La Appendia A of 10 CFR part 50, requires that

' " Structures, systems, and campeaants tapertant to safety shall be designed as aseammedsta the offsets of and to j be esapatible with the environmental esadittoms eseesisted with normal operaties, asistanasse, testing and pastulated accidents, including lese-of-eeslaat sealdents. These streetares, systems, and eenpesants shall be appropriataar protected assinst dyncate effects, including the effects

" of missiles, pipe whippias, and diamharging fluies, that may rossit from equipment failures and fresa events and sensittens outside the asalmer power unit."

The prerises verstem of the Osamission's General Design criteria alas ref1 sets the above requirements.

  • Thus, a analent plant abould be designed se that aba resster saa be ebut dews and maintatsad La a safe akutdown esaditten ta the arent of a postulated rupture, outside aestaAnnont, of a pipe esataining a high eenrgy f3dd, Ameluding the demblended rupture of the largest pipe in the mata steam and femerater systems. plant strustases, systems, and eenpements deportant to safety should be designed and leested la the facility- to seeemmedate the effects of such a petulated pipe failure to the extent mesessary to assers that a sde shutdown sendittee of the resster can be assemplished and maintataed.

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na.a en infomaues .e . .semur - avat.61e to us - oma-ciaes o,M '

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_ps 1 and I, we{ understand that the RFCK pipe linas ruq threagh the evoya s .,- 11g>y S7 '*M .

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.  ! commeomealth Edimos campegr D E.C 1 8 1972 I

the asia steen lies temmels and that a rapture of any steen lies sa this eres will met taslate and agr desses the WCI lines. itse, from I

the plant arramp====* drarings, it appears thes a eteen line asytere As the turbine buildies eseld result in ===d-*h en vital elastrieal l eq=ip===*. Fram this, it eypears that problems have been identified

and additiema1 arm 1maties will be seguired and same endifiassima of the faattities may be m .

We sequest that yes peevida es with ematyees and other selevant inf====* h needed to determans the enesequemens,of eesh events, usins the ==ea provided in the ens 1msed gn====1 internation regnest. The ===1==ess represemes sur hesia $mfeemstion negoirements for plants msw baias sometreated er operatias. You should 4an===i==

the appliemhilier, for the gend-cities familities, of the items listed in the -1====w.

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If the resmits of year amatyees indiesse that ehemses in the desism of structures, systems, er eserements are meseseary to ensure safe remeter ekstdoom in the event this pestmisted assident sit =ath l ehemia seeer, please provide safemmation en year plans se revise the desism of F*er famility to assommodate the postulated failures described above. day desism modifientimes proposed ehenad ses1.de appserziate eensideratiam of the psidelines and regemets for infeenetian in the j ===1amere.

We will also need, as seen as possible, estimates of the schedule for

. design, fabrienties, and insta11stiam of any modificatimes foemd to i

be messesary. Flesse inform as withis seven days after reesipt of this letter whom we may espoet to assolve en amendeamt with your analysis of this pestulated seeident eituattom for the quad-Cities facilities, a descriptism of any proposed modifications, and the

, sehedule estimates descriksi above. Einty espies of the ht oboedd be puweided.

lL l A espy of the comedasimm's prese ---* em this matter is alae

, emelesed for yeter informaties.

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a.;i.9 s: ped by:

Regu S. E:yd

i. si , p.t, treet.r for Roseter Psejects Directorate of Licensist l maelaeures mad es See samt page

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Form AECa318 (Rev. 9-83) AECW 0240 12/$f72 .12

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~. . j General Information Required for Consideration of the Effects of a Piping System Break Outside Containment j

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N, following is ~ a ' generai list of. information required for AEC review. .

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of th., effects of a piping system break outside containment . including J

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7 the double ended rupture of the largest pipe in the main ' steam and' feed-water systems, and for AEC review of any proposed ' design changes I that may be found. necessary. Since piping layouts are substantially I

different from plant to plant, applicants and licensees should determine

- . on an individual plant basis the applicability of each of the following i tems for inclusion in their submittals.

l. 1he systems (or portions of systems) for which protection against pipe whip is required should be identified. Protection from ofpe whip need I

not he provided if any of the following conditions will exist:

(n) Isoth of the following piping system conditions are met:

(1) the service temperature in less than 200* F; and (2) the design pressure is 275 psig or less; or (b) The piping is physically separated (or isolated) from structures.

l nystems, or components important to safety by protective barriers, or restrained from whipping by plant design features, such as concrete encasement; or (c) Following a single break, the unrestrained pipe movement of either end of the ruptured pipe in any possible direction about a plastic hinge formed at the nearest pipe whip restraint cannot impact any structure, system, or component important to safety; or

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(d) The internal energy level associated with the whipping pipe can be demonstrated to be insufficient to ispair the safety function of any structure, system, or component to an unacceptable level.

2. The criteria used to determine the design basis piping break locations in the piping systems should be equivalent to the following:

(a) ASME Section III Code Claqs I piping breaks should be postulated to occur at the following locations in each piping run or branch run:

(1) the terminal ends; (2) any intermediate locations between terminal ends where the primary plus secondary stress intensities S, (circum-ferential or longitudins1) derived on an elastica 11y

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The internal fluid energy level associated with the pipe break reaction may take into account any line restrictions (e.g. , flow limiter) between q the pressure source and break location, and the effects of either single-ended or double-ended flow conditions, as appifcable. The energy level in a whipping pipe may be considered as insufficient to rupture an impacted pipe of equal or greater nominal pipe size and equal or heavier wall thickness, .

Piping is a pressure retaining component consisting of straight or curved pipe and pipe fittings (e.g., elbows, tees, and reducers).

A piping run interconnects components such as pressure vessels, pumps, and rigidly fixed valves that may act to restrain pipe movement beyond that required for design thermal displacement. A branch run differs from a piping run only in that it originates at a piping ir.cersection, as a g j branch of the main pipe run. '

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  • calculated basis under the loadings associated with one -

i half safe shutdown earthquake and operational' plant 4

l conditions exceeda 2.0 S,5 for ferritic steel, and 2.4 5, for austenitic steel; (3) _ any intermediate locations between terminal ends where the cumulative usage factor (U) derived from the piping l fatigue analysis and based on all normal, upset, and i testing plant conditions exceeds 0.1; and j

(4) at' intermediate locations in addition to those determined I by (1) and (2) above, selected on a reasonable basis as necessary to provide protection. As a minimum, there l I should be two intermediate locations for each piping run .

or branch run.

(b) ASME Section III Code Class 2 and 3 piping breaks should be postuisted to occur at the following locations in each piping 3 run or branch runt I (1) the terminal ends;

' Operational plant conditions include normal reactor operation, upset conditions (e.g. , anticipated operational occurrences) and testing conditions.

5 3, is the design stress intensity as specified in Section III of the ASME Boiler and Pressure Vessel Code, " Nuclear Plant Components."

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U is the cumulative usage factor as specified in Section III of the ASME Boiler and Pressure Vessel Code, " Nuclear Power Plant Components."

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(2) any intermediate locations between terminal ends where 1

either the circumferential or leagitudinal stresses derived

.j on an elastica 11y calculated basis under the loadings associated with seismic events and operational plant-

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conditions exceed 0.9 (Sh*8) A or the expansion stresses' -1 exceed 0.8 SA ; and (3) ' intermediate locatione in addition to these determined by I i

(2) above,' selected on reasonable basis as 'necessary to  !

provide protection. . As a minimum, there should be two

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4 intermediate locations for each piping run or branch run.

' 3. I The. criteria used to determine the pipe break orientation at the break: 4 4

locations as specified under 2 above should be equivalent to the f

following: l 1

(a) -Longitudinal breaks in piping runs and branch runs, 4. inches -

nominal pipe size and larger, and/or

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h is the stress calculated by the rules of NC-3600 sad ND-3600 for Class 2 and 3 components, respectively, of the ASME Code Section III -]

Winter 1972 Addenda.

S i A is the allowable stress range for expansion stress calculated by the i rules of NC-3600 of the ASME Code,Section III, or the USA Standard Code for Pressure Piping, ANSI B31.1.0-1967. i 8 I Longitudinal breaks are parallel to the pipe axis and oriented at ar.y point around the pipe circumference. The break area is equal to the effective cross-sectional flow' area upstream of the break location. {

Dynamic forces resulting from such breaks are asemed to cause lateral 1' pipe movements in the direction normal to the pipe. axis.

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i (b) Circumferential' breaka in piping runs and branch runs exceeding 1 inch nominal pipe size.

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' 4. A summary should be provided of the dynamic analyses applicable to the design of Category I piping and associated supports which determine the resulting loadings as a result of a postulated pipe break includings (a) The locations and number of design basis breaks on which the dynamic analyses are based.

(b) The postulated rupture orientation, such as a circumferential and/or longitudinal break (s), for each postulated design basis break location.

(c) A description of the forcing functions used for the pApe whip dynamic analyses including the direction, rise time, magnitude, duration and initial conditions that adequately represent the jet stream dynamics and the system pressure difference, (d) Diagrams of mathematical models used for the dynamic analysis.

(e) A summary of the analyses which demonstrates that unrestrained motion of ruptured lines will not damage to an unacceptable degree, structure, systems, or components important to safety, such as the control room.

9 Circumferential breake are perpendicular to the pipe axis, and the break area is equivalent to the internal cross-sectional area of the ruptured pipe. Dynamic forces resulting from such breaks are assumed to separate the piping axially, and cause whipping in any direction normal to the pipe axis.

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5. A description should be provided of the measures, as applicable, to protect against pipe whip, blowdown jet and reactive forces including:

(a) Pipe restraint design to prevent pipe whip impact; (b) Protectivs provisions for structures, systems, and components required for safety against pipe whip and blowdown jet and reactive forces; (c) Separation of redundant features; j (d) Provisions to separate physically piping and other components of redundant features; and 1

(e) A description of the typical pipe whip restraints and a summary 1 of number and location of all restraints in each system.

6. The procedures that will be used to evaluate the structural adequacy  ;

1 of Category I structures and to design new seismic Category I structures should be provided including (a) The method of evaluating stresses, e.g., the working stress method and/or the ultimate strength method that will be used; 4

(b) The allowable design stresses and/or strains; and (c) The load factors and the load combinations.

7. The design loads, including the pressure and temperature transients, the dead, live and equipment loads; and the pipe and equipment static, thermal, and dynamic reactions should be provided.

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8. . Seismic Category I structural elements such as floors, interior j i

walls, exterior walls, building penetrations and the buildings.

as a whole should be analysed for eventual reversal of loads due

, to the postulated accident.

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9. If new openings are to be provided in existing structures, the. f I

capabilities of the modified structures to carry the design loads i should be demonstrated.

10. Verification that failure of any structure, including nonseismic Category I structures, caused by the accident, will not cause i failure of any other structure in a manner to adversely affects (a) Mitigation of the consequences of the accidents; and (b) Capability to bring the unit (s) to a cold shutdown condition.
11. Verification that rupture of a pipe carrying high energy fluid will not directly or indirectly result in:

(a) Loss of redundancy in any portion of the protection system (as defined in IEEE-279), Class IE electric system (as defined in IEEE-308), engineered safety feature equipment, cable pene- '

trations, or their interconnecting cables required to mitigate the consequences of the steam line break accident and place the reactor (s) in a cold shutdown condition; or

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(b) Loss.of the ability to cope with accidents due to ruptures of pipes other than a steam line, such as the rupture of pipes e

causing a steam or water leak too small to cause a reactor accident but large enough to cause electrical failure.

12. Assurance should be provided that the control room will be habitable t

, and its equipment functional after a steam line or feedwater line break or that the capability for shutdown and cooldown of the unit (s) will be available in another habitable area.

13. Environmental qualification should be demonstrated by test for that electrical equipment required to function in the steam-air environ-ment resulting from a steam line or feedwater line break. The in-formation required for our review should include the following:

(a) Identification of all electrical equipment necessary to meet requirements of 11 above. The time after the accident in which they are required to operate should be given.

(b) The test conditions and the results of test data showing that the systems will perform their intended function in the environ-ment resulting from the postulated accident and time interval of

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the accident. Environmental conditions used for the teste should be selected from a conservative evaluation of accident conditions. r (c) The results of a study of steam systems identifying locations where l l

barriers will be required to prevent steam' jet impingnent from dis-abling a protection system. The design criteria for the barriers  !

should be stated and the capability of the equipment to survive within the protected environment should be described. '

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, r (d) An evaluation of the capability for safety related electrical equipaent in the control room- to function in the environment

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that may exist following a pipe break accident should be provided. ' Environmental conditions used for the evaluation should be selected from conservative calculations of accident conditions.  !

(e) An evaluation to assure that the onsite power distribution system and onsite sources (diesels and batteries) will remain operable throughout the event.

14. Design diagrams and drawings of the steam and feedwater lines including branch lines showing the routing from containment to the o

turbine building should be provided. The drawings should show elevations ,and include the location relative to the piping runs of asfety related equipment including ventilation equipment, intakes, and ducts.

15. A discussion should be provided of the potential for flooding of safety 1

related equipment in the event of f ailure of a feedwater line or any other line carrying high energy fluid.

16. A description should be provided of the quality control and inspection l

programs that will be required or have been utilized for piping systems outside containment.

17. If leak detection equipment is to be used in the proposed modifications, a discussion of its capabilities should be provided.

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18. A summary should be provided of the emergency procedures that would be followed after a pipe break accident, including the automatic and manual operations required to place the reactor unit (s) in a
cold shutdown condition. The estimated times following the accident

'l for all equipment and personnel operational actions should be included in the procedure summary.

19. A description should be provided of the seismic and quality classi-fication of the high anergy fluid piping systems including the steam and feedwater piping that run near structures, systems, or components 4

important to safety.

20. A description should be provided of the assumptions, methods, and results of analyses, including steam generator' blowdown, used to calculate the pressure and temperature transients in compartments, pipe tunnels, intermediate buildings, and the turbine building following a pipe rupture in these areas. The equipment assumed to function in the analyses should be identified and the capability of systems required to function to meet a single active component failure should be described.
21. A description should be provided of the methods or analyses performed to demonstrate that there will be no adverse effects on the primary and/or secondary containment structures due to a pipe rupture outside these structures.

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1 UNITED STATES

  • h ATOMIC ENERGY COMMISSION WASHINGTON, D.C. <10545

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No.

l P-429

Contact:

Frank Ingram FOR IMMEDI ATE RELEASE f Tel. 301/973-7771 (Wednesday, December 13, 1972).

AEC REGULATORY STAFF REQUESTS DATA ON PIPE BREAKS IN NUCLEAR PLANTS The Atomic Energy Commission's Regulatory Staff'is asking all utilities that operate nuclear power plants or have applied for operating licenses to assess the effects on essential auxiliary systems of a major break of the largest main steam or feedwater line. These lines carry steam from inside the reactor . containment building to the main turbine in the turbine building, and hot feedwater back from the turbine condenser. The utility assessments will be evaluated by the AEC's Regulatory Staff.

The probability of a steam-line rupture is low.

Nonetheless it will have to be considered in the AEC's safety evaluation.

1 The review for several weeks. of the pipe break problem has been under way

  • It was started after the Advisory Com-mittee on Reactor questions about Safeguards received a letter raising the location of pipes in the two-unit Prairie Island plant in Minnesota.

The Regulatory Staff has reviewed the Northern States Power Company application to operate Prairic Island, and on the basis changes of data will be available required it has concluded that design at Prairie Island.

Based on the new information--to be submitted by utili-ties as soon as possible--the Staff will determine what corrective action, if any, is necessary in each case. The changes couldofinclude viding venting such steps as relocating piping, pro-compartments the addition of piping restraints, and, in some cases,, structural strengthening.

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