ML19319E199

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Forwards General Design Criteria Requirements for Consideration of Effects of Piping Sys Break Outside Containment.Aec 721213 Press Release Encl
ML19319E199
Person / Time
Site: Rancho Seco
Issue date: 12/14/1972
From: Anthony Giambusso
US ATOMIC ENERGY COMMISSION (AEC)
To: Davis E
SACRAMENTO MUNICIPAL UTILITY DISTRICT
References
NUDOCS 8003310712
Download: ML19319E199 (14)
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- General Information - Required for Consideration of the Effects of a Piping System Break Outside Containment

'The following is a general list of information required for AEC review of. the effects of a piping system break outside containment, including

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

dif ferent from plant to plant, applicants and licensees should determine on an individual plant basis the applicability-of each of the following items for. inclusion in their submittals.

1.

The systens -(or portions of systems) for which protection against pipe whip is required should be identified. Protection from pipe whip need not he provided if any of the following conditions will exist:

(a) Both of the following piping system conditions are met:

(1) the service. temperature is 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, sys tems, 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 ruptuied pipe in any possible direction about a plastic hinge ' formed. at the nearest pipe' whip res traint cannot impact any structure,~ system, or component important to safety; or 3

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-. (d), The internal energy level associated with the whipping pipe

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'can be demonstrated to be insufficient to impair 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 Clags I piping breaks should be postulated to occur at the following locations in each 3

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-

-farential or longitudinsi) derived on an elastica 11y The internal fluid energy level associated with the pipe break reaction may take into account any-line restrictions (e.g.,' flow limiter) between t

the pressure source and break location, and the effects of either single-ended _or double-ended flow conditions,.as' applicable. 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 l'nterconnects 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 intersection, as a

. branch of the main pipe run.

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calculated basis under the loadings associated with one -

-half safe shutdown earthquake and operational plant 4 exceeds 2.0 S,5 conditions for ferritic steel, and 2.4 S, for austenitic steel; (3)~ any intermediate' locations between terminal ends where

~i the cumulative usage factor (U)6 derived from the piping I

i fatigue analysis and based on all normal, upset, and testing plant conditions exceeds 0.1; and (4) at intermediate locations in addition to those determined

- by (1) and (2) above, selected on a reasonable basis as necessary to provide protection. As a minimum, there 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 postulated to occur at the-following locations in each piping

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run or branch run:

(1) the terminal ends;

'4Operational' plant conditions include normal reactor operation, upset conditions -(e.g., anticipated operational occurrences) and testing conditions.

5 i

S, is the design stress intensity as specified in Section III of the l

ASME Boiler and. Pressure'. Vessel. Code, " Nuclear Plant Components."

(

'6U'is the cumulative usage factor as specified in Section III of the

.'ASME Boiler and Pressure Vessel Code, " Nuclear Power Plant Components."

1.

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. (2) any intermediate locations between terminal ends where either the circunferential or longitudinal stresses derived on an elastica 11y calculated basis under the loadings associated with seismic events and operational plant conditions exceed 0.9 (Sh+8) r the expansion stresses A

exceed 0.8 S ; and A

(3) intermediate locations in addition to these determined by (2) above, selected on reasonable basis as necessary to provide protection. As a minimum, there should be two intermediate locations for each piping run or' branch run.

3.

The criteria used to determine the pipe break orientation at the break locations as specified under 2 above should be equivalent to the following:

~

(a) Longitudinal breaks in piping runs and branch runs, 4 inches nominal pipe size and larger, and/or S is t a stress calculated by the rules of NC-3600 and ND-3600 for h

Class 2 and 3 components, respectively, of the ASME Code Section III Winter 1972 Addenda.

SA' is the allowable stress range for expansion stress calculated by the rules of NC-3600 of the ASME Code,Section III, or the USA Standard Code for Pressure Piping, ANSI B31.1.0-1967.

8Longitudinal breaks are parallel to the pipe axis and oriented at any point around the' pipe circumference. The break area is equal to the effective cross-sectional flow area upstream of the break 1ccation.

' Dynamic forces resulting from such breaks are assumed to cause lateral pipe-movements-in the diraction-normal to the pipe axis.

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5-(b) Circumferential' breaks in piping runs and branch runs exceeding 1 inch nominal pipe size.

= 4.

A summary should be provided of the dynamic analyses applicable to the design of Category I piping and associated supports ithich determine the resulting loadings as a result of a postulated pipe break including:

(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 pipe whip dynamic analyses including the direction, rise time, magnitude, duration and initial conditions that adequately represent the jet s'tream 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 4

-degree, structure, systems, or components important to safety, such as the control room.

'Circumferential breaks are perpendicular to the pipe axis, and the break area:is equivalent to the internal cross-sectional. area of-the ruptured pipe. 'Dynsaic forces resulting from such breaks are assumed to separate

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the piping axially, and causa whipping in any direction normal to the pipe axis..

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6-5.

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

i (a) Pipe restraint design to prevent pipe whip impact; j

(b) Protective provisions for structures, systems, and components j

required for safety against pipe whip and blowdown jet and reactive forces; (c) Separation of redundant features; (d) Provisions to separate physically piping and other components of redundant features; and (e) A description of the typical pipe whip raatraints and a summary of number and location of all restraints in each system.

6.

The procedures that will be used to evaluate the structural adequacy 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 strees method and/or the ultimate strength method that will be used; (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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-7 8.

Seismic Category I structural elements such as floors, intsrior walls, exterior walls, building penetrations and the buildings as a whole should be analyzed for eventual reversal of loads due to the postulated accident.

9.

If new openings are to be provided in existing structures, the capabilities of the modified structures to carry the design loads should be demonstrated.

10. Verification that failure of any structure, including nonseismic Category I structures, caused by the accident, will not cause failure of any other structure in a manner to adversely affect:

(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 redundracy 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 l

reactor (s) in'a cold shutdown condition; or I

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. (b) Loss of the ability to cope with accidents due to ruptures of pipes other than a steam line, auch as the rupture of pipes 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 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 availtble in another habitable area.

13.

Environmental qualification should be demonstrated by test for that electrical equipment required to function in the steam-sir 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 the accident. Environmental conditions used for the tests should be selected from a conservative evaluation of accident conditions.

(c) The results of a study of steam s, stems identifying locations where barriers will be required to prevent steam jet impingment 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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. (d)

An evaluation of-the capability for safety related electrical

- equipment.; the control room to function in the environment 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 turbine building should be provided. The drawings should show elevations and include 3e location relative to the piping runs of nafety relateu equipment including ventilation equipment, intakes, and ducts.

15.

A discussion should be provided of the potential for flooding of safety

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

16.

A description should be provided of the quality control and inspection 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 pr' ided 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 for all equipment and personne1' 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 energy fluid piping systems including the steam and feedwater piping that run near structures, systems, or components 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 sheuld 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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No.

P-429 FOR IMMEDI ATE RELEASE

Contact:

Frank Ingram (Wednesday, December 13, 1972)

Tel.

301/973-7771 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.

Nonethc1 css it will have to be considered in the AEC's safety evaluation.

i The review of the pipe break problem has been under way fot several weeks.

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

The Regulatory Staff has reviewed the horthern States Power Company application to operate Prairie Island, and i

on the basis of data availabic it has concluded that design changes will be required at Prairic Island.

Based on the new information--to be submitted by utili-ties as soon as possibic--the Staff will determine what corrective action, if any,, is necessary in each case.

The changes could include such steps as relocating piping, pro-viding venting of compartments, the addition of piping restraints, and, in some cases, structural strengthening.

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