ML19329D794

Forwards List of General Info Required for Consideration of Effects of Piping Sys Break Outside Containment,Aec 721213 Press Release Requesting Data on Pipe Breaks in Facilities & AEC Transmitting Rept on Densification

ML19329D794
Person / Time
Site:	Crystal River
Issue date:	12/15/1972
From:	Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC)
To:	Rodgers J FLORIDA POWER CORP.
Shared Package
ML19329D795	List: ML19329D794 ML19329D797
References
NUDOCS 8003170738
Download: ML19329D794 (14)

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m General Information Required for Consideration of the Effects of a Piping System Break Outside Containment

%e following in 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 systems, and for AEC review of any proposed design changes that may be found necessary. Since piping layouts are substantially different 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.

We systems (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 ruptured pipe in any possible direction about a plastic hinge formed at l

the nearest pipe whip restraint cannot impact any l

structure, system, or component important to safety; or l

l

. (d) The internal energy level associated with the whipping pipe can be demonstrated to be insufficient to impair the safety function of any structure, systes, 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 longitudinal) derived on an elastica 11y 1The internal fluid energy level associated with the pipe break reaction may take into account any line restrictions (e.g., flow limiter) between 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).

3 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 intersection, as a branch of the main pipe run.

. calculated basis under the loadings associated with one -

half safe shutdown earthquake and operational plant 4 exceeds 2.0 S,5 for ferritic steel, and conditions 2.4 S, for austenitic steel; (3) any intermediate locations between terminal ends where the cumulative usage factor (U) derived from the piping 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 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 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.

S, is the design stress intensity as specified in Section III of the (SME 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."

l

. (2) any intermediate locations between terminal ends where either the circumferential 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 g

(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 the 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.

S is the allowable stress range for expansion stress calculated by the A

rules of NC-3600 of the ASME Code,Section III, or the USA Standard Code for Pressure Piping, ANSI B31.1.0-1967.

Longitudinal breaks are parallel to the pipe axis and oriented at any point around the pipe circumference. The break area is equal to the effective cress-sectional flow area upstream of the break location.

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

s 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 which 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 stream dynamics and the system pressure difference.

(d) Diagrams of mathematical models used for the dynamic analysis.

(e) A sunmary 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.

'Circumferential breaks 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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'N 6-5.

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) Protective provisions for structures, systems, and components 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 restraints 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 stress 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.

1 i

1

- 8.

Seismic Category I structural elements such as floors, interior 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 redundancy in any portion of the protection system (as defined in IEEE-279), Class IE electric system (as defined in IEEE-303), engineered safety feature equipment, cable pene-trations, or their interconnecting cables required to mitigate l

the consequences of the steam line break accident and place the reactor (s) in a cold shutdown condition; or

. (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 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 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

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the systems will perform their intended function in the environ-l 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.

1 (c) The results of a study of steam systems identifying locations where

)

i 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 l

within the protected environment should be described.

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' (d)

An evaluation of the capability for safety related electrical equipment in the control room to function in the environment j

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 i

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 the location relative to the piping runs of safety related 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.

l

f

, 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 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 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 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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s Uf41TED STATES O

ATOMIC ENERGY COMMISSI,0N WASHb6GTON, D.C.

20545 i

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8

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No.

P-429 FOR IMMEDI ATE RELEASE l

Contact:

Frank Ingram (Wednesday, December 13, 1972)

Tel.

301/973-7771 i

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 1

steam from inside the reactor :ontainment building to the l

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.

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

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

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

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on the basis of data available it has concluded that design changes will be required 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 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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