ML19319B781
| ML19319B781 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/15/1972 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19319B777 | List: |
| References | |
| NUDOCS 8001270249 | |
| Download: ML19319B781 (10) | |
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General Information Raquired for Consideration of the Ef fsets of a Piping System Break Outside Containment The following is a general list of information required for AEC review of the ef fects of a piping system break outside centsinment, 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 i te ms for inclusion in their submittals.
1.
The systems (or portions of systems) for which protection against pipe whip in required should be identified. Protection from pipe whip need not he prnvided 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 (h) The piping is physically separated (or isolated) from structures, s ys tem 1, or components import an t to safety by protective barriers, or res trained from whipping by plant design features, such as concrete encasement; or 1
(c) Following a single break, the unrestrained pipe movement of either end of the rupt'ared pipe in any possible direction about a plastic hinge formed at the nearest pipe whip restraint cannot impact any structure, system, or component inportant to safety; or 8001270J(f f
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. (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 unseceptable 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 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 restrictione (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).
A piping run interconnects components such as pressure vessels, pumps, and rigidly fixed valves that may act to restrain pipe movenent 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.
3-calculated basis under the loadings associated with one -
half safe shutdown earthquake and operational plant axeseds 2.0 S,5 for ferritic steel, and conditions 2.4 S, for austenitic steel; (3) any interaadiate 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) ASE 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;
' Operational 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 ASME Boiler and Pressure Vessel Code, " Nuclear Plant Components."
6U is the cumulative usage factor as specified in Section III of the ASE Boiler and Pressure Vessel Code, " Nuclear Power Plant Components."
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. (2) any intermediate locations between terminal ends where either the circumferential or longitudinal stressas derived on an elastically calculated basis under the loadings associated with seismic events and operational plant conditions exceed 0.9 (Sh* A)
. the expansion stresses exceed 0.8 S 3
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(3) intermediate locations in addition to these determined by (2) above, selected on reasonable Lasis 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 7S is the stress calculated by the rules of NC-3600 and ND-3600 for h
class 2 and 3 components, respectively, cf 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.
8Longitudinal breaks are parallel to the pipe axis and oriented at any point around the pipe circumference. The break area 12 equal to the effective cross-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.
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_3-(b) Circumferential breaks in piping runs and branch runs exceeding 1 inch nominal pipe size.
A summary should be provided of the dynamic analyses applicable to e 4.
design of Category I piping and associated supports which determine the resulting loadings as a result of a 30....ted pipe break including:
(a) The locations and number of design besis breaks on which the dynamic analyses are basad, (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, duratian and initial conditions that e.dequately represent the jet stream dynamics anc the system pressure difference.
(d) Diagrams of mathematical acdels used for the dynamic analysis.
(e) A summary of the analyses which demonstrates that unrestrained motion of rupture'd lines sill not damage to an unacceptable degree, structure, systems, or components important to safety, i
such as the control room.
l Circumferential breaks are perpendicular to the pipe axis, and the break 9
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) Protective provisions for structures, systems, and components required for safety against pipe whip and blowdown jet and i
reactive forces; (c) Separation of redundant features; (d) Provisions to separate physically piping and other components of redundant featursa; 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 ue.ed 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 t.he ultimate strength method that will be used; (b) The allowable design streeses and/or strains; and (c) The load factors and the load combinatior.o.
7.
The design loads, including the pressure and temperature transients, the dead, live and equipment loads; and t!.
pipe and equipment static, thermal, and dynamic reactions should be provided.
- 8.
Seismic Category I structural elements such as floors, interior salls, exterior walls, building penetrations and the buildings as a whole should be analyzed for eventual reversal of loads due to the postuisted 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-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 l
. (b) Loss of the ability to cope with accidents dua to ruptures of pipes other than a sesam line, such as the rupture of pipes causing a steam or water lesk too small to cause a reactor accident but large enough to causa 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 tese 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 enculd be selected from a conservative evaluation of accident conditions.
(c) The results of a study of steam systema 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 in the centrol 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 sesure that the onsite power distribution system and onsite sources (diesels and batteries) will remain ope rable throughout the event.
14.
Design diagrama 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 f ailure of a feedwater line or sny 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 bs provided of the amargency 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 naar 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 enapartments, 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.