ML20028B910

Forwards Nonproprietary Version of Revisions to FSAR Re Protection Against Possible Turbine Missiles

ML20028B910
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	08/18/1982
From:	Tramm T COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20028B902	List: ML20028B901 ML20028B905 ML20028B906 ML20028B910
References
4787N, NUDOCS 8212070207
Download: ML20028B910 (70)

Text

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O eEt Na5o*nal Pa a C po, Enois NON-PROPRIETARY VERSION

, Address Reply to: Post Office Box 767 Submitted 11-29-82 Chicago, lihnois 60690 Augus't '18, 1982 Mr. Harold R. Denton, Director Of fice of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Turbine Missile Study NRC Docke t No s . 50-454, 50-455, 50-456, and 50-457 Reference (a): May 4, 1982, letter from T. R. Tramm to H. R. Den t o n .

Dear Mr. Denton:

This is to provide advance copies of revised FSAR information regarding protection against possible turbine missiles at Byron and Braidwood Stations. NRC review of this information should close Outstanding Item 2 of the Byron SER.

Enclosed and Appendix C of thewith Byron this letter areFSAR.

/Braidwood revisions to Section 3.5.1.3 This documents the turoine missile analysis study which was undertaken as described in reference (a). The analysis shows that if the low pressure disk inspection interval is less than 43 months in terms of turbine running time, the probability of damage will be less than lx10-6 per turbine unit per year. This analysis reviewed by our consultant at this time. has not been completely The NRC will be informed l

1 of any changes emanating from this review by September 1,1982.

These changes will be incorporated into the FSAR at the l next opportunity. Please address any questions regarding this matter to this office.

One signed original and fif teen copies of this letter and the enclosures are provided for your review.

j Very truly yours, f.h f -. v -

Ib ! .yR. -

jd yT Tramm 1m -

Nuclear Licensing Administrator x

8212070207 821129 PDR ADOCK 05000454 N

4787N PDR

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. , D/2-FSAR The missile characteristics of the bonnets of the valves in the region where the pressurizer extends above the operating deck are given in Table 3.5-2a.

The missile characteristics of the piping temperature sensor assemblies are given in Table 3.5-2b. A 10 degree expansion half angle water jet has been assumed. The missile characteristics of the piping pressure element assemblies are less severe than those of Table 3.5-2b.

The missile characteristics of the reactor coolant pump temperature sensor, the instrumentation well of the pres-surizer, and the pressurizer heaters are given in Table 3.5-2c. A 10 degree expansion half angle water jet has I

been assumed.

3.5.1.3 Turbine Missiles The turbine-generators at the Byron /Braidwood Stations are manufactured by the Westinghouse Electric Corporation. Each unit consists of four double-flow turbine cylinders: one high pressure, and three low pressure. The turbine-generator type is a 40-inch last row blades and has a rated speed of 1800 rpm.

An analysis was performed to evaluate the probability of damage from postulated turbine missiles to safety-related components at the Byron /Braidwood Stations. This analysis shows that if the inspection time of low pressure discs is kept below 43 months in terms of turbine running time, the corresponding conservative estimate of probability of damage will be less than 1 x 10-6 per turbine unit por year. Based on th'is low probabi.1.ity, the turbine missile hazard is not

considered a design-basis event for these stations. The details of this probability analysis are provided in Appendix C. -

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• APPENDIX C TURBINE MISSILE STUDY i

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s/n-rsam APPENDIX C "..

TURBINE MISSILE STUDY i

TABLE OF CONTENTS ,. I, PAGE - c C.1 INTRODUCTION C.1-1 C.1.1 General C.1-1 C.1.2 Organization of the Report C.1-2

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C.2 FORMULATION C.2-1

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C.2.1 General C.2-1 C.2.2 Turbine Missile Generation C.2-1 ~

C.2.3 Missile Characteristics C.2-3 C.2.4 Frequency of a Plant Damage State C.2-4 C.2.5 Sim.ulation of Condi.tional Frequency of Damage States C.2-6 c.2.6 References C.2-9 C.3 UANT MODEL FOR THE SIMULATION C.3-1 C.3.1 General C.3-1 C.3.2 Targets C.3-1 C.3.3 Barriers C.3-2 C.3.4 Turbine Model C.3-3 C 3.5 References C.3-3 C.4 ,

FAULT TREE FOR PLANT DAMAGE STATES C.4-1 C.4.1 General C.4-1 )

C.4.2 Damage States C and M C.4-1 C.4.3 Damage State R C.4-3 C.4.4 References C.4-3 C.5 PRESENTATION AND DISCUSSION OF RESULTS C.5-1 C.5.1 General C.5-2 C.S.2 Conditional Frequencies of Damage States C.5-1 C.5.3 Frequency of Plant Damage States per Year C.5-2 C.6

SUMMARY

AND CONCLUSIONS C.6-1

.I C-1 I

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B/B-FSAR APPENDIX C TURBINE MISSILE STUDY LIST OF TABLES NUMBERS TITLE PAGE C.2-1 Frequency of Missile Generation Per Year for Byron Unit 1 Turbine C.2-10 C.2-2 Contribution of Discs Types 2 and 3 to Total F:cquency of Missile Generation, f due to Stress Corrosion C.2-ll C.2-3 Mks,sileCharacteristicsforByron/

Braidwood Stations

' C.2-12 l ,C.3-1 List of Targets Used in Simulation Model C.3-4 C.4-1 Definition of Damage States and Their i

Relation to NRC Regulatory Guide 1.115 Criteria C.4 4 C.4-2 Frequency of Component Unavailability C.4-5 C.4-3 Minimal Cut Sets for Damage State M C.4-6 C.5-1 Conditional Frequency of the Three Damage States for Three Speed Conditions C.5-4 C.5-2 Frequency per Year of Damage States C.5-5 1

ee V

C-li

B/B-FSAR APPENDIX C TURBINE MISSILE STUDY LIST OF FIGURES NUN 3ER TITLE C.2-1 Arrangement of Discs on LP Turbines of Byron Unit 1 C.2-2 Vertical Ejection Angles for LP Discs and Fragments C.2-3 Horizontal Deflection Angles for Disc and Fragments C.3-1 Elevation View of Simulation Model Showing Some Barriers and Targets C.3-2 Targets and Barriers on Floor El. 346'0" C.3-3 Targets and Barriers on Floor El. 364'0" C.3-4 Targets and Barriers on Floor El. 383'0" C.3-5 Targets and Barriers on Grade Floor El. 401'0" C.3-6 Targets and Barriers on Mezzanine Floor El. 426'0" C.3-7 Targets and Barriers at Main Floor El. 451'0" C.3-8 Targets and Barriers on the Floor El. 439'0" C.3-9 Targets and Barriers on the Floor El. 463'4 "

C.3-10 Targets and Barriers Outside the Main Plant C.4-1 Turbine Missile Fault Tree C.4-2 LOCA Resulting from Breach of Containment C.4-3 Loss of Cold shutdown Capability C.4-4 Loss of Syctems to Achieve Cold Shutdown C.4-5 Loss of AFW Pumping C.4-6 Loss of Charging C.4-7 Loss of Safety Injection C.4-8 Loss of Service Water C.4-9 Loss of Division 11 AC Power C.4-10 Loss of Division 12 AC Power C.4-ll Loss of Component Cooling System C.4-12 Loss of RHR C.4-13 Loss of Letdown Systems C.4-14 Loss of Boric Acid Transfer Pump Control or Power C.5-1 Frequency per Year of the Various Damage States in Terms of Turbine Inspection Time I

1 l

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, B/B-FSAR APPENDIX C TURBINE MISSILE STUDY c.1 INTRODUCTION C.1.1 General Previous probabilistic analysis of turbine missile hazard at Byron /Braidwood Stations was made in 1978 and it is presented in Reference 1. Based on the values of missile generation probability then avaigable, the plant damage probability was reported as 4.3 x 10- per year. Westinghouse Electric Corpo-ration has subsequently revised the probabilities of missile generation due to evidence of stress corrosion cracking in some nuclear turbines. This revision affects missile generation at rated speed and at design overspeed conditions but leaves the missile generation probability at destructive overspeed unchanged from the previously used values. The revised prob-abilities of missile generation depend on turbine operating ,

time since the last inspection for stress corrosion cracking.

Generally, these probabilities are several orders of magnitude greater than the value used in Reference 1.

The purpose of this report' is to evaluate the probability of turbine missile hazard at the Byron /Braidwood Stations considering the revised values for the probability of missile generation. A number of modifications have also been introduced into the analysis in order to take advantage of current infor-mation and for the purpose of making a more realistic assessment.

These are as follows:

a. The present analysis considers plant logic and redundancy of components through a fault tree analysis.

b. Perforation velocity of reinforced concrete barriers is predicted using CEA-EDF formula.

c. Possibility of missile ricochet is considered in the analysis.

d. The current vender information on turbine missile characteristics is used.

Items a through c above make it necessary to adopt a simulation model for predicting conditional probabilities of damaae given that a missile is generated. The basic information and assump-tions used in the simulation procedure are also described in the report.

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B/B-FSAR Results show that the probability of damage from turbine missile depends on the turbine operating time since last inspection.

If the inspection time of low pressure discs remains below 43 months in terms of turbine running time, the corresponding conserygtive estimate of damage probability will be less than 1 x 10- per turbine per year. This result is obtained using the available missile generation probabilities of Byron Unit 1 turbine. This conclusion will be applicable to the turbines of Byron Unit 1 and Braidwood Units 1 and 2 if the missile generation probabilities for those units are less than or equal to those of Byron Unit 1.

c.1.2 Organization of the Reoort The report contains six sections. Section C.2 presents the infor-

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mation for modeling turbine missile generation and describes formulation of probabilistic analysis for determining probabil-itien of various plant damages. Section C.3 describes the olant structural model used for simulation of missile trajectories.

Section C.4 describes the fault tree analysis of the plant damage l

i states. Section C.5 presents and discusses the probability resulta of the specific damage states due to turbine missile l hazards. Section C.6 summarizes the study and its conclusions.

REFERENCE:

1. Byron /Braidwood Stations, Final Safety Analysis Report, Volume 14, Amendment 14, Commonwealth Edison Company, November 1981.

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B/B-FSAR C.2 FORMULATION C.2.1 General ,

This section summarizes the available information which is used as input in the probabilistic analysis of turbine missile hazard and presents a formulation for processing this infor-mation to obtain the probability of a specified damage state of the plant. A simulation model, which permits the damage probabilities to be estimated by using a realistic and detailed model of the plant and the missile transport phenomenon, is described.

C.2.2 Turbine Missile Generation The information used to determine the likely sources of turbine missiles and their probabilities of generation is derived from reports prepared by the turbine manufacturer. Each unit of the Byron /Braidwood Stations is equipped with one high-pressure (HP) and three low-pressure (LP) turbine units manufactured

• by Westinghouse Electric Corporation (herein called Westinghouse) .

Each LP unit has 12 discs, which are shrunk-fit onto the LP rotor. The HP unit, on the other hand, has a forged single-piece rotor (Reference 2). As will be shown, this construction provides a basis for ruling out the HP unit as a potential source of missiles. Missile generation, therefore, refeto to a process in which a single LP disc ruptures, and pieces of the ruptured disc perforate the turbine casing and become missiles. The perforation of the turbine casing gives rise to other missiles called associated fragments.

According to the turbine manufacturer (Reference 2), the rupture of LP discs or a HP cylinder may occur at one of three speed conditions: rated speedt design overspeed; or, destructive overspeed. The rated speed for nuclear turbines is 1800 rpm.

The design overspeed is 120% of the rated speed; the destructive overspeed is 185% of the rated speed. When a disc fails under any of these speed conditions, it is assumed that the damage to the turbine as a result of the rupture of a single disc will prevent any further acceleration of the turbine or sub-sequent rupture of other discs.

The design overspeed condition can occur if, at the maximum generator load, the generator separates from the system and the speed governing mechanism fails simultaneously. In such an event, the turbine reaches about 120% of the rated speed, and is then stopped by the overspeed trip mechanism. Turbine rotors are designed for this overspeed condition.

The destructive overspeed condition can occur if, upon loss of the maximum generator load, the speed governing and trip C.2-1

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. e B/B-FSAR l

mechanisms fail in succession and steam continues to be fed l to the turbine. Under this accelerating turbine condition, the tangential stress in one of the rotating parts eventually reaches its in-place rupture strength, causing the element l

to fail as a result of ductile burst. This occurs only in

the case of the LP discs; it is shown in References 2 and 3 that the RP unit is strong enou'gh to prevent it from failing due to ductile burst before LP disc failure occurs. Therefore, missile generation from a HP cylinder at destructive overspeed is not postulated.

- The two recognized rupture mechanisms under the rated and the design overspeed conditions are stress corrosion and fatigue (Reference 4). Stress corrosion has been observed in some keyways and bores of the LP discs. Because of its forged single-piece construction, the HP rotor is not expected to rupture due to stress corrosion. Thus, the LP units are the only potential sources of missiles under stress corrosion failure. o Fatigue crack growth resulting from speed cycling can occur in both LP and HP units. However, comparisons have indicated that the probability per year of missile generation due to stress corrosion could be several orders of magnitude greater than that due to fatigue. Therefore, under the rated speed and the design overspeed conditions, stress corrosion is the probable cause of disc rupture. Since the potential for failure due to fatigue is so small, and rupture of a HP unit due to stress corrosion has been ruled out, the LP discs are the only potential sources of missile generation under the rated speed and the design overspeed conditions.

l The estimates of the probability of missile generation per year for the LP units at Byron Unit 1 were obtained from References 5 and 6. The values of the frequency of missile generation f (w are given in Table C.2-1. The symbol w , i = 1,2,3 rhfer b,atot)the , rated speed, design overspeed, and dektructive overspeed conditions, respectively. The symbol at identifies a preselected turbine inspection time in terms of turbine ,

operation time since the last inspection. It should be noted

, in Table C.2-1 that f 1 is dependent on the turbine inspection l

• time for the rated speed and the design overspeed conditions, l but is independent of at for the destructive overspeed condition.

i l

As indicated above, the discs of the LP units are the only i credible sources of missiles. It is assumed that all discs i are equally likely to rupture under the destructive overspeed condition, and the value of f 1 (w 3,a t) equals the frequency of one of the 36 discs becoming a missile source.

C.2-2

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t B/B-FSAR Examinations of the rupture frequencies of individual discs at the rated speed and design overspeed conditions show that not all discs are equally likely to generate missiles. Type 2 discs are most likely to rupture at the rated ' speed condition, while Type 2 and Type 3 discs are likely to rupture at design overspeed. Table C.2-2 con. pares the values of f 3 00 3, A t) of six Type 3 discs with the f go values of 36 discs of Unit 1 at rated speed. Aslmilke,At) comparison is made with the design overspeed condition. The missile characteristics of six Type 3 discs were used in the simulation model for rated speed, and the characteristics of 12 Type 2 and Type 3 discs were used for design overspeed, since these types are the major contributors to the total frequency of missile generation (Table C.2-2) . For conservatism, however, the corresponding values of f y for all 36 discs were used in the calculations.

C.2.3 Missile Characteristies -

Based on the potential for distributed bore cracks and on field experience, an LP disc rupture may result in major seg- -

ments (hub-to-rim fractures) varying in size from 30' to approx-imately 200* (Reference 2). This implies that 90', 120',

and 180' segments are likely to result from a disc failure.

Westinghouse's assessment indicates that the 90' and the 120' disc segments are reasonable approximations because these missiles will have the greatest exit energy. The missile characteristics used in this report are based on 90' disc segments (Figure C.2-2) .

When a disc ruptures into quarters, the impact with stationary parts of the turbine results in several other fragments with varying exit velocities and shapes. The fractured segments of the disc and the associated fragments become missiles upon exiting the turbine housing.

Each 90* disc segment of a given disc type is assumed to produce the same number of fragments, each of which will have similar characteristics. Table C.2-3 shows the characteristics of discs and fragments used in the simulation model for each disc type at the rated speed, design overspeed, and destructive overspeed conditions. The values given for these parameters are provided by Westinghouse in Reference 2.

In probabilistic evaluations, exit velocity is treated as a random variable. A uniform distribution is used for missile velocities ranging from -10% to +10% of the tabulated best estimate.

C.2-3

.. . - ~ -

l B/B-FSAR After a missile exits the t'urbine, it may impact various floors and walls of the plant. The impact area of each missile at each impact is' assumed to be uniformly distributed between the miniummt and maximum impact areas, as shown in the table.

The assumption of an independent random v.'.ciable at each impact also accounts for the rotational motion of the missile within the plant. It can be seen in Table C.2-3 that the minimum and maximum impact areas at the rated speed and the design i overspeed differ from those at the destructive overspeed.

The initial direction of the missile at the time of ejection is defined by two random angles, O and 0 O is the vertical angle measured from the vertical aIis in tNe. plXne of the disc and S h is the deflection angle measured from the plans

, of the disc. For toe disc in the firnt quadrant,O is assumed l to be a random variable with a range of C to 90'. yFcr' discs is established by adding 90' l in the O to.the remaining for thequadrants,0 disc in the, preceding quadrant. This implies that on1 one random variable is required to define O for l all disc segments. The vertical angles for all the fYagments are selected randomly within the respective quadrants. Figure -

, C.2-2 gives a schematic representation of the vertical angles for.the discs and the fragments.

l l The range of deflection angles for the disce and the fragments was obtained from Reference 2. For each LP unit, the O h s for the inner discs and fragments vary from -5' to +5'r for outer fragments, O (or from -25' to l -5', as applicableI. varies These from angles 5' are to 25' shown schematically

[ in rigure C.2-3. Within the specified range, all valves of i the random variable under discussion are considered equally j likely; therefore, a uniform density function is used to define

, the probability law of exit angles.

C.2.4 Frequency of a Plant Damage State Let c denote a plant dame.ge state such as the loss of cold

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shutdown capability or a radiological release of a certain level. Precise expressions for q in terms of various equipment failures are defined from the plant logic. On the assumption that turbine missile generation can occur at any of the tnree l speed conditions w i 1 2,3, and using the theorem of total l

• probability,thefhe,quen=cy,ofthisdamagemaybeexpressed as:

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f (C ,At) =

}] f2 (CIWg) ft (wi,At) (C.2-1) i=1 C.2-4

+'~t- -- - - - c+- -- , - . , , --

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, B/B-FSAR in which ,

f (C, At) = frequency of damage state c per year for a selected inspection time At.

fg (wg,at) = frequency of missile generation per year at speed condition w g and inspection time ht.

= conditional frequency of damage state f2 (Clwi) C, given missile generation at speed con-dition w g.

For purposes of this report, At measures accumulated turbine operating time since last inspection.

Using ' plant logic, C may be expressed as l m C

l

= uG (C.2-2) l j=1 where -

q$ = minimal cut sets of the q-fault tree l

E

= operation of union on events Cg.

j=1 l From Equation C.2-2, the following expression can be established:

a f2 (C !"i) # f 2 ICj!"i) (C.2-3) y The conditional frequencies f, ( c4 lwi) are estimated by a simulation process in which missiles are generated and traced through the plant spaces as described in Subsection C.2.5.

With these conditional frequencies available, f, (gje is calculated using Equation C.2-3. This information peh.m) its the evaluation of the frequency of the damage state using Equation C.2-1 and the data given in Table C.2-1. Because Equation C.2-3 presents the upper bound of f 2 (CIWI), it follows that the estimate of damage state frequencies is conservative.

C.2-5

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, B/B-FSAR C.2.5 Simulation of Conditional Frequency of Damage States The simulation model for determining the conditional frequencies f2 (Cj !Wi) inv lves the following items.

a. Targets representing plant spaces in this safety -

related equipment, i.7cluding cabling and piping, '

are located. These targets are considered prisms; '

for conservatism, it is assumed that they offer no resistance to a missile strike.

b. Barriers representing reinforced concrete walls and slabs, and in a few cases steel components, are modeled as planes at appropriate locations.

The CEA-EDF formula (Reference 7),.which provides better correlation to data for reinforced concrete perforation by solid missiles (Reference 8), is used in the analysis. It is expressed as V

p = 1.43t fy 1/2(d/w)2/3 (C.2-4)

The BRL formula (Reference 8) is used for steel barrier, i .e.,

V = 1058.56kl/2(dt)3/4,-1/2 (C.2-5)

P where V

p = perforation velocity, fps t = concrete barrier thickness, inches ff = concrete compressive strength, psi d = missile diameter, inches w = missile weight, lbs k = constant (usually equal to 1) for Equation C.2-5.

c. Missile sources, i.e., the LP discs, are generated depending on the speed condition wg selected.

Missile weights are treated as deterministic quan-tities; exit speeds and angles are treated as random variables, as described in subsection C.2.2.

C.2-6 9

2 + - - .= =:.-.= = - 1: _ _. _. _ -

B/B-FSAR More details on the physical modeling.of targets, barriers, and missile sources used for the Byron /Braidwood Stations are given in Section C.3. Using plant logic, a fault tree is constructed for the damage state under consideration.

The basic events of this tree are the targets of the physical plant model. The minimal cut sets of the g-fault tree indicate which specific combination of plant spaces must be damaged in order to induce a certain undesirable event as defined in NRC Regulatory Guide 1.115, for instance, excessive offsite releases. Section C.4 provides details on the fault trees constructed for the Byron /Braidwood Stations.

To complete the description of the simulation model, the steps followed for one simulation trial.at a particular speed condition are listed below. These steps are executed by the SEL program SIMULATE (Reference 9).

1. From the missile sources applicable to the selected speed condition to break in mko, four a disc pieces. is selected The at random and associated is assumed fragments partinent to the selected disc type are determined from Table C.2-3. Exit speeds and directions of the missiles are then sampled from the applicable distributions of .,

V,0,, and Oh described in Subsection C.2.3.

2. The possible missiles generated from the disc are then ejected, and their trajectories are traced. The governing equations of the trajectories depend on whether they are high or low. A high trajectory missile is one which enters the plant complex on its downward flight. A low-trajectory missile is one which enters the plant directly after exiting the turbine housing. For low-trajectory missiles, gravity and air resistance are ignored, which implies that such missiles follow a straight line trajectory. For high trajectory missiles, the effect of gravity is considered, but air resistance is igno'ted. l After the type of trajectory is determined, the path of the missile from the selected disc is traced to determine what it hits first. If a barrier is hit, its capability to resist perforation is examined against missile impact i in terms of velocities. If the missile is able'to perforate the barrier, its residual velocity is calculated and the trajectory is traced further. If the missile'is unable to perforate the barrier, two possibilities are considered:

a. embedment of the missile in the barrier, and

b. missile rebound (ricochet) .

l C.2-7

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w-4 g--w=-w_e -wmm- e, +,g . , , , , _ , , , ,

B/B-FSAR The angle of incidence is the most.significant parameter in determining the route the missile will take. If the angle of incidence (angle between the line of the missile trajectory and the normal to the barrier plane) is greater than about 45', it is highly probable that the missile will be reflected (Reference 10). Since there are virtually no data on the embedment behavior of irregularly shaped missiles at various angles of incidence to the concrete, an angle of 15' is selected for the purpose of determining the possibility of ricochet. If the angle of incidence is less than 15', it is assumed that the missile embeds <

1 l

in the concrete; the path of such a missile is not traced further. If the angle of incidence is greater than 15',

ricochet is considered; the missile is assumed to continue its flight with reduced velocity and a new initial angle.

If the missile hits a target, information such as the target name, the weight of the missile, and the energy t

l

with which the target is hit is stored in a data file for future processing. It is assumed that a missile which hits a target continues.its flight with the same speed and direciton, i.e., the loss of energy during impact is ignored.

3. Steps 1 and 2 are repeated a predetermined number of times (N=1000) and information regarding the hit targets is stored.

4. The information about the hit targets created for N trials in Item 3 is condensed by eliminating those targets which are hit repeatedly in a single trial. Repeated hits of a target during a trial can occur either because of ricochet of the same missile or because different fragment missiles ,

may hit the same target during the trial. The condensation l 1

process considers all of these as a single hit.

5. stand for the number of times at soeed condition LetnkkthetargethitsdefiningC.arerealizedinthe wg th j

condensed list. Then the conditio3al frequency is expressed as: .

= "il, i + 1,2,3; j + 1,2,...,m (C.2-6) f 2 IGj !"i) N .

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C.2.6 References  !

l. Byron /Braidwood Stations, Final Safety Analysis Report, ]

Volume 14, Amendment 34, commonwealth Edison Company, I November 1981.

2. Westinghouse Electric Corporation, " Turbine Missile Report (EP296-LP380-LP380-LP380) ," Report No. CT-24889, Rev. O, April 1981.

3. Westinghouse Electric Corporation, " Report Covering the Ef fects of a Turbine Accelerating to Destructive Overspeed," l l

Preliminary Report No. 296/380A, 1974.

l 4. Westinghouse Electric Corporation, " Methodology for Calculating the Probability of a Missile' Generation from Rupture of )

i a Low-Prssure Turbine Disc." Report No. CT-24076, Rev. O, May 1980. I l 5. Westinghouse Electric Corporation, " Turbine Missile Report -

Results of Probability Analysis of Disc Rupture and Missile Generation," Report No. CT24890, Rev. 3, March 1982.

6. Westinghouse Electric Corporation, " Analysis of the Probability of the Generation and Strike of Missiles from a Nuclear Turbine," March 1974.

7. C. Berriand, et al, " Local Behavior of Reinforced Concrete Walls Under Missile Impact," Paper J 7/9, 4th SMiRT Conference, t

August 1977; also, Nuclear Engineering & Design, Vol. 45, l 1978.

8. Civil Engineering & Nuclear Power, Vol. V: Report of the ASCE Committee on Impactive and Impulsive Loads, September 1980.

9. Sargent & Lundy Engineers, " SIMULATE - A Monte Carlo Analysis of Turbine Missile Hazard," User's Manual No. 09.7.186-2.0, l

Rev. O, May 1982.

10. S. H. Bush, " Probability of Damage to Nuclear Components Due to Turbine Failure," Nuclear Safety, Vol. 14, No. 3, May-June 1973.

l l

C.2-9 4

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TABLE C.2-1 ,

l I FREQUENCY OF MISSILE GENERATION PER YEAR ,

i FOR BYRON UNIT 1 TURBINE .

INSPECTION INTERVAL IN TERMS OF TURBINE OPERATING TIME '

SPEED (At = YEARS) -

"i 1 2 3 4 5 10 o

"1 j. ___ __.

Rated

. Speed w

n

)'

~

b "2 Design $

Overspeed W

3 .

Destructive

-6 1.70x10 -6 1.70x10 -6 1.70x10 -0 1.70x10 -0 Overspeed 1.70x10 1.70x10-0 NOTE: The values contained in this table are Westinghouse proprietary information..

Values for w 3 and w, are taken from Reference 5, and the value for m3 is taken from Referenc6 6.

TABLE C.2-2 -

CONTRIBUTION OF DISC TYPES 2 AND 3 TO TOTAL FREQUENCY .

. OF MISSILE GENERATION, fy, DUE TO STRESS CORROSION RATED SPEED DESIGN OVERSPEED

• 7gggygg

. INSPECTION f f f f INTERVAL (6 DkSCS (36 DkSCS/ DISC 3 (12 DIbCS OF (36DkSCS/ DISCS 263 x100

( At = YEARS) OF TYPE 3) UNIT 1) UNIT 1 xWO TYPES 2 & 3) UNIT 1) UNIT 1

, 1 w

N O W 2 g 9

E 3

4 5

10 b

I TABLE C.2-3 -

)

MISSILE CHARACTERISTICS FOR BYRON /BRAIDWOOD STATIONS  !

i-RATED SPEED DESIGN OVERSPEED DESTRUCTIVE OVERSPEED

,7 mn A A A DISC AND WEIGHT Vel max y,y -

min max y,y min max f; FRAGMENTS lbs ft/sec ft ft ft/sec ft ft ft/sec. ft ft- -

!l

\

l 3095 NA NA NA NA NA NA 75 1.49 5.65 1.1 5400 '

75 1.47 12.99 (

l.2 3740 75 0.80 9.66 1.3 380

• 0.09 2.66 1.4 270

• 0.05 11.04 4 P

Y 2 3500 NA NA NA 120 1.62 5.26 417 1.62 5.26 i 2.1 2555 120 h  :

0.74 7.20 417 '0.74 7.20 i-2.2 350

• 0.09 2.46 417 0.09 1

2.46 '

2.3 3235 120 0.94 417 8.51 0.94 8.51 2.4 1640 120 0.39 417 0.39 t

7.32 7.32 2.5 250

• 0.05 10.24 417 0.05 10.24 1

t' 3 4225 195 1.87 6.57 278 1.87 1.87 6.57 533 '6.57 3.1 2395 161 0.71 8.16 226 0.71 8.16 427 0.71 8.16  !

3.2 1010 161 0.26 4.50 226 0.26 427 0.26 3435 195 4.50 4.50 ij 3.3 0.96 11.86 278 0.96 11.86 533 0.96 11.86 3.4 1540 195 0.37 6.87 278 0.37 6.87 533 0.37 6.87 l .

i, l l 1

i 1

l . .!

I.

. t; TABLE C.2-3 (Cont'd) ll' RATED SPEED DESIGN OVERSPEED DESTRU IVE OVERSPEED '

A A A DISC AND WEIGHT Vel 8I" 2

Y'1 A* Y'1 A

A* '

2 2 2 FRAGMENTS lhe ft/sec ft ft ft/seo ft _ f.t ft/890 L 2 ft 2

q h

4 3380 NA NA NA NA NA 852 1.46 3.39

.NA p

,,i 4.1 770 825 0.23 4.11 ij 4.2 640 , 558 0.36 2.85 F 3

't.

4 5 3465 NA NA NA NA NA NA 578 1.49 3.64 ,

5.1 1255 578 0.39 5.59 m 8

.n 5.2 1465 578 0.43 6.31 Y  !

Y 5.3 200 w

610 0.05 7.05 5  !"

5.4 340 578 0.09 6.94 8

l:

II 6 3720 NA NA NA NA NA NA 707 1.89 4.35 - ,, j; 6.1 780 707 0.28 4.91 - !l 6.2 50 707 0.02 0.91 l'

. ,i. t

'U t!

NOTE:

NA = Not applicable for negligible f y f'

values (Subsection C.2.2) . l,

= According to Reference 2 (Section C.1), missile energy less than 10 5 ft-lb  !!'

is not reported. I; 4

4 ji.

I!i

I i

. t D, -

s'3" i

',1'e= 38'3" _

38'3" _

3 i Il .

. .. a ...e.,

j j i,i l .,,g, l p'

s End_. > i ',i i 8.'

l 1 I l l3 'l , -

l .

g' f.P Turbine IC '

LP Turbine IB LP Turbine 1A

, 13,,,,. , r . , d . c . b r.a, 6.c .d , . r ; it . . d ,c 6 ,ar, b .e d , ,e i . r 4= , d .= .6 f 6 ,= .d ,* ,r

. l' b 14.384*

c 15.900* 6 54 3 2 l '1 2 3 4 5 6 6 5 4 3 2 1 l1 2 3 4 5 6 d 6 5 4 3 2 1 1 2 3 4 5 6 G3 '

111111111111 1ll111111111 lll 111111111  %!

DISCS USED FOR DESTRUCTIVE OVERSPE2D k'

i i;

" l' 3 2 2 3 3 2 2 3 3 2 2 3 a 11 11 1I II ll 1I -

DISCS USED FOR DES 1CN OVERSPEED

• .l

[

- - l 3 3 3 3 3 l l i- 1 I i i  ! ,

DISCS USED FOR RATED SPEED j t

FICURE (,2-l ARRANGEMENT OF DISCS ON LP TURBINES OF BYRON UNIT 1 r i LI OIiYU i

\  !

fk 1

w_ __ __ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

. gygon -pys. ,

5 .

~

Direction of'the disc segment in 1st quadrant 0v Direction of fragments; random in'4 5 quadrant Direction of fragments; Direction of tha disc segment .

random in 1st quadrant in 4th quadr r.t .

Disc -

?

Disc .

d D sc '

Di c Direction . Direction of the fragrents; : n:!om disc sega.ent in in 3rd quadr' . 2 n d q u a d r r..a.t

( -

0' -

Directica of fragments;

. Direction of the disc random in 2nd quadrant

. segment in 3rd quadrant l

l

~

I j 4

1 1

l Figure C.2-2 vertical Ejection Angles for M Discs & Fragments

(

g s

j

- ep-Fparc-" -

- ' I go $ a So y

=

,20-q\t

\\N -

\ , '

Line passing -

1 through the plane of the I

Range of disc A deflection N5%

NN angic -

pace for

\\

I disc and

- fragments

h. '

l l .

A typical _

l inner di'sc PJ l A typical .

outer disc Rotor /

.-- /

W% {

.- k_ - / _

Rotor

[__ Centerline l______ -q/\)

\ se i

\ is e,

i e'

\ / \ /

48 /

0 g

l p. -

.f Il L=*

i

)

l Lg . l r

l l -

I Figure C.2-3 Hoci.zontal Deflection Angles for LP Disc & Fragfr.ents e

e em .

l - -. _- ._ _

I 8/B-FSAR.

C.3 PLANT MODEL FOR THE SIMULATION C.3.1 General -

l l

The physical model of the entire plant complex is described in this section. The plant model.is.used for simulating turbine l.

missile trajectories through the plant. The physical plant model includes a detailed description of targets and barriers.

The targets represent the safe shutdown equipment or reactor coolant system components, and the barriers represent the varior.s structural elements such as concrete walls and slabs that offer resistance to missile penetration.

C.3.2 Targets Targets are usually those safety-related structures, equipment, I and components whose destruction or malfunction is detrimental to the safe (cold) shutdown or results in a LOCA of the plant. l The detailed modeling of each and every target in the plant is not practical because it involves enormous amounts of physical .

effort and computer time. To simplify the modeling effort, large cubicles are used to define the targets. The boundaries of these cubicles are mainly based on the zones defined for the isolation of fire hazard. These zones usually extend from the floor to the ceiling and are bounded by the reinforced concrete walls and slabs. A target is thus assumed to be the volume occupied by the zone. A zone may actually house one or more safety-related components or equipment. With this definition of target it is assumed that once a missile perforates the boundary of a zone, the equipment or componentn ,

located inside are damaged. This is a conservative assumption and it also addresses efficiently the problem of secondary missiles that might be ejected as a result of impact of the primary missile on reinforced concrete walls. The system fault tree constructed for plant damage states (Section C.4) is in agreement with this definition of targets.

The fire zones used in this report are taken from the Fire Protection Report for Byron /Braidwood Stations, Reference 1.

Table C.3-1 lists only those fire zones which are pertinent to the turbine missile hazard analysis. All the targets listed herain are not necessarily taken from Reference 1; the excep-tions are those within the containment identified in Table C.3-1 as targets 1.1 through 1.4.3. This addition of targets was necessary because of the refinement required by plant logic. The target sizes used, however, are conservative and allow for physical sizes of actual missiles. The analysis of the crane damage due to the turbine missile strike shows that there is a potential for the crane girder to collapse C.3-1 e

. . _ - . , . . . . . - . , - _.y . , . , _

- ~. - -- . .. . . - . .

• - - - . - = = - , . . . ~ . . - . . . . . ..

i .*

B/B-FSAR on to reactor coolant system components. For this reason, the crane girder is listed as target 1.4.3 in Table C.3-1.

In modeling the crane girder, it was assumed that the crane is parked in the north-south direction.

A number of targets outside of th'e plant structures were also considered in the study because of plant logic consideration.

These are identified in Table C.3-1 as targets 0-1 through 0-4. Figures C.3-1 through C.3-10 show the location of the targets within the plant structures.

C.3.3 Barriers Barriers are those objects in the plant complex which offer resistance to turbine missile penetration. For the purpose of conservatism and ease in modeling, only reinforced concrete walls and slabs having thicknesses greater than or equal to 6 inches are considered in the plant model. Other objects, lik'e piping, valves, tanks, etc. , have been assumed to offer no resistance to missiles, and to be unable to alter the missile path. The moisture separators and part of the steam generators, however, are modeled as steel barriers. These idealizations are shown in Figure C.3-1. Precast concrete roof slabs, sidings, gratings and all the blockwalls are neglected. Being closer to the source of the missiles, the turbine pedestal concrete girders are idealized as two barriers. These girders run parallel to the run of the turbine shaft. Most of the missiles ejected in the second quadrant are intercepted by these massive girders and thus reduce the chances of missiles hitting the targets in the auxiliary building.

The moisture separators are located on the main floor (elevation 451 feet 0 inch) of the turbine buliding on either side of the turbine. They are modeled as 1-1/2 thick steel barriers.

These barriers help stop some of the missiles from entering the auxiliary building.

Since a missile strike damage to the upper portion of the steam generators (above elevation 426 feet 0 inch) would not cause a LOCA, the steam generators are, therefore, models as targets l up to elevation 426 feet 0 inch and as steel barriers for their upper portions.

For reinforced concrete barriers the values of concrete com-pressive strength, ff, used in the analysis are 5000 psi in the containment building and 3500 psi elsewhere. Since these values are design values and are less than that for aged-in-place concrete, the values are conservative.

C.3-2

_- . = _

~

^ ' _;n_nn;n- 7 _ -

. B/B-FSAR C.3.4 Turbine Model The locations of three low-pressure turbines in the model are shown in Figure C.3-1. These units are identical and symmetrical about the axial center point. The number of discs and their relative locations along the shaft are modeled and shown in Figure C.2-1. These locations then serve as the initial points of ejection of the niasiles. The turbine shaft is 4 feet 6 inches above the turbine main floor (elevation 451 feet 0 inch). For destructive overspeed, all 36 discs are modeled as missile sources. For the design overspeed, Types 2 and 3 discs (total of 12 discs) are used as missile sources. For the rated speed condition, only Type 3 discs (total of six discs) are modeled. The reason for this choice is given in Subsection C.2.2, and Table C.2-1.

C.3.5 Reference

1. Byron /Braidwood Stations Fire Protection Report, Vol. 1, Commonwealth Edison Company, October 1977.

~

C.3-3

+

9 B/B-FSAR

- TABLE C.3-1 LIST OF TARGETS USED IN SIMULATION MODEL TARGET IDENTIFICATION DESCRIPTION 0-1 Bus Ducts 0-2 Essential Service Water Piping and Condensate Storage Piping l

0-3 Essential Service Water Piping and Condensate l Storage Piping 0-4 Condensate Storage Piping I

i 1.1 Reactor Pressure Vessel l

l .

1.2.1X Containment Spray Main Riser ,

1.2.1Y containment spray Main Riser l

l.2.2 Fan Coolers l 1.2.3 Fan Coolers 1.2.4 Fan Coolers 1.2.5 Fan Coolers 1.2.6 Accumulator

1. 2. i Accumulator 1.2.8 Accumulator 1.2.9 Accumulator 1.3.1 Steam Generator

. 1.3.1A Main Steam and Feedwater Piping Housing 1.3.2 Steam Generator i

l 1.3.2A Main Steam and Feedwater Piping Housing 1.3.3 Steam Generator 1.3.4 Steam Generator i

1 1 C.3-4 11

- - , - 7 - - , - ,. - , , - - - - - , - - -y-vr9---- -w - - - - - - -- - -- - - -

... . _ . . . . . _ . . . - _ _ _ - _ . . . . . . _ . . _ _ _ _. .~ . . . _ . _ _ _ _ . _ - . . _ ._ _. _

. 5/B-FSAR

• TABLE C.3-1 (Cont'd)

TARGET IDENTIFICATION DESCRIPTION.

1.4.1 Control Rod Drive Mechanism Bousing

'l.4.2 Pressurizer 1.4.3 Polar Crane 2.1-0 Control Room 3.1-1 Cable Tunnel 3.2A-1 Nonsegregated But Duct Area 3.2B-1 Lower Cable Sprea51ng Room, Zone B-1 3.2C-1 Lower Cable Spreading Room, Zone C-1 3.2D-1 Lower Cable Spreading Room, Zone D-1 3.2E-1 Division 12 Cable Riser, Lower Spreading Room 3.3A-1 Upper Cable Spreading Room, Zone A-1 3.3B-1 Upper Cable Spreading Room, Zone B-1 3.3C-1 Upper Cable Spreading Room, Zone C-1 3.3D-1 Upper Cable Spreading Room, Zone D-1 3.4A-1 Division 12 Cable Riser Area  !

(Elevation 451 feet 0 inches) 4.4-1 Computer Room 5.1-1 ESF Switchgear Room, Division 12 5.2-1 ESF Switchgear Room, Division 11

. 5.4-1 Miscellaneous Electrical Equipment and Battery Room, Division 12 5.5-1 Auxiliary Electrical Equipment Room 5.6-1 Miscellaneous Electrical Equipment and

' Battery Room, Division 11 9.1-1 Diesel-Generator Room, 1B C.3-5

l- - . .- -

n/n-rsAR  ;

l

, TABLE C.3-1 (Cont'd)

TARGET IDENTIFICATION DESCRIPTION.

9.2-1 Diesel-Generator Room 1A 9.3-1 Diesel-Generator Day Tank Room lA 9.4-1 Diesel-Generator Day Tank Room IB 10.1-1 Diesel Fuel Oil Storage Room 1B 10.2-1 Diesel Fuel Oil Storage Room lA 11.1-1 Auxiliary Building, Basement (Elevation 330 feet 0 inches) 11.1-2 Auxiliary Building, Basement, Unit 2 (Elevation 330 feet 0 inches) 11.2-0 Auxiliary Building General Area (Elevation 346 feet 0 inches) 11.2A-1 Residual Heat Removal Pump 1A Room 11.28-1 Containment Spray Pump 1A Room 11.2C-1 Containment Spray Pump 1B Room ll.2D-1 Residual Heat Removal Pump 1B Room 11.3-0 Auxiliary Building General Area (Elevation 364 feet 0 inches) ll.3A-1 Safety Injection Pump 1A Room ll.3B-1 Residual Heat Removal Heat Excha'nger lA Room

..l . 3 C-1 Positive Displacement Charging Pump Room 1

ll.3D-1 Centrifugal Charging Pump 1A Room

- ll.3E-1 Residual Heat Removal Heat Exchanger 1B Room l

ll.3F-1 Safety Injection Pump 1B Room i

! C.3-6 l

+ - *, ,,

---

s- - - ,

l B/B-FSAR TABLE C.3-1 (Cont'd)

TARGET IDENTIFICATION DESCRIPTION" ll.3G-1 Centrifugal Charging Pump 1B Room 11.3-1 Auxiliary Building, Unit 1 Area (Elevation 364 feet 0 inches) ll.4-E Auxiliary Building General Area (Elevation 383 feet 0 inches) 11.4A-1 Auxiliary Feedwater Pump Diesel Room 11.4C-0 Radwaste and Remote Shutdown Control Room 11.5-0 Auxiliary Building Ventilation System, Boric Acid Tank, Filters, Transfer Sumps, etc.

(Elevation 401 feet 0 inches) .

ll.5A-1 . Containment Electrical Penetration Area, Division 11 (Elevation 414 feet 0 inches) 11.6-0 Auxiliary Building Ventilation System, Boron Injection Recirculation Pumps, Surge Tanks, Cable and Panels, etc.

(Elevation 426 feet 0 inches) ll.6A-1 Boron Injection Piping 11.6-1 Electrical Penetrations Area, Division 12 11.7-0 Auxiliary Building HVAC Exhaust Complex 17.2-1 Essential Service Water Cooling Tower, .

Unit 1 17.2-2 Essential Service Water Cooling Tower, Unit 2 18.1-1 Diesel-Generator 1B and Switchgear Room Air Shaft 18.2-1 Diesel-Generator 1A and Switchgear Room Air Shaft 18.3-1 Main Steam and Auxiliary Feedwater Pipe Tunnel C.3-7

l. . - - . - . - - - . . . . . . .. . . .

l .

, B/B-FSAR

- TABIJE C.3-1 (Cont'd)

TARGET IDEWrIFICATION DESCRIPTION l

i 18.10E-1 System Auxillary Transformers l 18.23-0 Condenisate Storage tank, Deepwell, and

- Construction Fire Pump Area 18.25-1 Primary Water Storage Tank No. 1 l

l l

1 9

l G8 O

C.3-8

. ._ . _ . . _ _ _ _ . . - . . . . _ _._ _ . _ ._. . i; b

k . d 9- Idealised '

1:

Done j -

i

,- - g

• r, Cont. Main  ;

p I i id=*1t**4 e'

( .2.1y) - ls i !i i

S$rayRisers l's .

I

. . . Molature I -

Separatore

[ Turbine l} Polar l , \ Cont. Main .

Nealized Upper l Cra T' "

SPray Riserer

, Part of Steap Ceu.. - ,,l(1.4.3)

I [ i Shaft I. .

. g,t s (1.2.1x) ,'

y e

g

). 4l (1.4.1) l Pressuriser l!

N a **

s  !

-j  ; )4l 451' 1 /

N,, '-

8

'LI l

• Cable Pan il I i  !:

t

, N- Ares ,s l i A e e, - - -- - .wS itch

• j

,8 1 fc

.p

• Fadestal Clrdars . ~h 42

' [-.NGy_-

cear am. I i e H_j i 1.2.s:1.2. 0 m s

Idea 11 ed as two , , ., g- j

's p

-Diesel \/ k

'. .gu j ll barriers, each \ / 'ff s- /

401 '2 s, s s,

Cenuator

,'g

s. ,

',/

s

(-

\g gf f .,

,4

• y,,c,,g,,, ..

{l 7','

'd\, '

<# A 'D (1.2.2 ;1.2. 3 3 ' -  !

,/

A / , , ',v,M 1.2.431.2.5) b, -_.._- __...- ,

7 O/ \ P ', /[\\ / '-

I.

, _ , (, , _ ,

]  !,

l 1 Turb. Bldg. Auu. Bldg. React. Bldg. Stese Cenerato a c 1 RPV (1.3.1 31.3.2 31!3.331.3.4)  :

• . (1.1) and L Main Steam & Feed Water t Housing (1.3.lA & 1.3.2A) '

I FICURE C.}l ELEVAf!ON VIEW OF SIMUI.ATION HOllEL SHOWING SOME BARRIERS AND TARGETS '

r L

(s) -

Unit

=

1 Unit 2

i

= . I '

i i*

Reactor Containment -

Unit 1 . .  !

3 o. .. - l, 9- ..

11.20- T< -

. . . ... _-- ---- - / ij{. i /

i,

,- 3 i i / [. ]; s . .;

..\ \. 11.2c.1 s 1

3_.

I / '

.s;

' .iN.,,T /

. . _ = . -

--;.p. 7

'.ll- \,

l  !

\. ,

11.28-lh '

1

......<,'i

.sg  !

l

. 11.2A-1 l \

m a

170' T' L _.1 s .I 7-. iI l

N ,. i.

l N -

i yeo= _

s T l

l AUX.Bt ILDING

- i k i I

11.2-0 -

I i I  !

3 1

__ a I

i kof LP Turbinesg gg.g 133'0" f ,

'i I

I Figure C2-2 Targets and Barriers on Floor El. 346'0" j 4

l j

pnit 1 Unit t -

11.3F yy,3g,3

~

y__

y. r J

. l( /m, t ',y,-g5l, 11.31 l O 3 )I

. r \ll , 7 1

\

11.7 lll .

11.3(

-4 -

I, i

11.31

-1

-JF .

h 4

I 11.3-1

\[l l!

_ i e

]_1 \l -

l 18.3-1 11.3-0

• l ,_ _ _ j ~

I I

g j Aux. Bldg. .

g '

~~~

Turbine Bldg 65' 0- E  !

L_ i , ,

i . .= . . - - (. Centerline of LP Turbines -

71 i l gj I'___________a I

_._ ._ _1 h j

I t 342'0" (NORTH i

' I l1-Figure C.3-3 Targets & Darriers on Floor E1. 364'0" i

lj ii

- I!

5

. 1 , i' j

!li i'

+t' l .; !l 4tli.

,lIl g j

.! i;!

l: , , ,i  !

mah1h*f '

s

~

n o

s t

c*

i0 T r' r3 j I i l l j R a8 B3 l

g Iil lN O s. .

}l '

N l

.. \ sE

[ \

Il

( t er g i _

go ro al Q d - ,

L- V TF

- 3 0

' 3

- c C N 4 e r

/ N _ 1 ug I g -

] 1 i Ig. _ .

F L- i l hL' -

t 1-r,. L i_ s e

i s l}

- I l n .ll .

i _

b 1

U . l ' ll , i r _

1.' - . u

' 0 g T

t t

- d i g 4 l 1 P n n B - -

U_ , ti 1 ^

4 L_

f nd 1 .

o 6"

el x

• mi o 1 e

nu A 1 n

6 0

iB i a l 2

. t r

- n e o t C n N$ e 1

3 d

g ~

8 _

1_

' (

~ - . .

-e _ _.

- 6 _

o

- 7 s o

7 g

I 1I!flII 1( .I lf  ;

l.

, tmit 1

• tmit 2 ,

1 I (kintaltunent e ~

Building I #-% N %

/

' I

._ y/ ki .. , .

j s \g / -

) t j ..

L i

N~ .

f o

@ - - - . n i s i T- 7 i g,4 1 Aux. Bldg. L__j  !

6" 9.3 '

_ 29.2-1 p __ q l '

1 9 1-1 __

- - - - -- -- } _ - - - ,

, g

.- -- - a N

65' 0' o }

l t t i a 3._,

05' 0"

. __l

\

3[

n .

Centerline of LP ' turbines .

F ' -

- -i g-- ,

~ ,

j 50' 0" IIeater Bay Building  !

p)

L

-- . 1- .- -- - - -. - - - >! .

I:

i,

.i (NORT  !,

342'0" - ,

s Figure C.3.S Targets & Barriers on Grade Floor El. 401'0" h t

UnL+ 1 Unit',2

~

Containment Building }

18.10E-1 .

' ""' N '

il1 [ \

t i l'  ;

/ \

g,_ _

\

i ___ . - -

'_7_, \

9296* i!/ -

1-s j -

i 8 s /

.63  :-

_] g .,

, Oo -- _

11.6-1 l (,1_a ,

' , _ _ _ T _ T-(- -i 5.J -1 Aux. Bldg.

5.2- 1 l

[

I 11.6-0 g g_

_____ __ l __.l_ _ l '

_._ __ _ _ _ _ _. q g l -<

55' I N

g .

C.enterl.ine of .LP Turbines _. ..

o i

65' -

I W .!

y t.

l p

- }

_ _ d 50 ' -

7_  ;{

I 3_ Heuter. Bay Building f!

g , _ , _

__ ___j ij 342'o.  !- ;l (NOR.TH -

o C o i i

Figure C 3'6 Targets & Barriers on Mezzanine Floor 81. 426'0" I

i

--- - - - - - - - - - - i Udt1 ' Unit 2 t

~

l l .

l ,.

Contalmeent Bldg.

i; N

N .,

/ \

I ' "

p __[ g h g _ . . __. ._- . . . _ .

_.4 i

g L

92'-6* f 11."-0 [' N ll s

/

I I l

3.4n- .

l <

& 18.2-1 t- a _1

. 2- p, 18 .1-h. . . i ,, _ _ 1 .

l 4.1- L l- - -

5.4-1 5.5-1 l 77'-6" Auxi11,ary B16 l.

2.1-0 s.6-1 _,__1_,._____,_ 1

) ___ ,,,,,_ _,,_ _ _ ,

Moisture separatorsJ m ....;........ - . .-s

,,, .. . -v..--.---.- .

z.

I M i __.. . _

%M ' '

/

(of LP furbi.7es/. I i Turbine Bidg. .

J D

s (_.__._

__. __ _ _. _ ._. _._ m _. __

f

__. __ _._ _a ll 50' 0" ~. lleater Bay l

5 ,'

6

' i n

., _/

!; i I'

342'-0" ,,_ -

1 L

NORTH l j.

Q Q . I FIGURE (,3'7 TARCETS AND BARR1F.HS AT MAIN FLOOR l E1. 451'-0"

_ ... _ . . ...~. ..._ - . . - . - . - - _ . -

T~ -.

~~

. i h'

• 3.3D-1 .

---

3 8

..)

• s t ,

1 3.3B-1 --..__-4 1 3.3C-1 F.--- 4 6 3.3A-1 8 8 l 1

---

...L ...

l 108'-0" *

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. . . B/B-FSAR C.4 FAULT TREE FOR PLANT DAMAGE STATES I e l C.4.1 General In previous sections, the turbine missile generation mechanisms

, and frequencies, and the structural plant model through which simulated missile trajectories and structural penetrations occur were discussed. In the following, the consequences of turbine missiles impacting various plant equipment and

, initiating an accident is examined.

In this analysis, fault trees are developed to determine the sequence of failure of plant components from turbine missile impact that could lead to accidents beyond the current design basis as defined in NRC Regulatory Guide 1.115. These accidents

, referred to as damage states in this report are summarized in Table C.4-1. The relationship of our definitions to the

specific criteria given by Regulatory Guide 1.115 is also presented in this table. Fault trees also include the failure of various components required to mitigate accidents to start on demand. Minimal cut sets of the developed trees are used

! in Section C.5 to quantify the probability of the plant damage states.

C.4.2 Damage States'C and M A turbine missile could initiate many plant events. While the exact sequence of events can become quite involved, only a limited number of key functions must be examined to ask the questions necessary for determining if the consequences would be beyond the results considered in the plant design basis. When the disc ruptures tc form the missile, the turbine will trip. After the turbine trip, two accident scenarios can be identified which would be more severe than the design basis. The first scenario, designated as C, involves missiles penetrating containment and striking components and/or subsystems within containment. This is assumed to result in a LOCA.

The additional element in C involves the opening left in the containment wall created by the turbine missile. This would prevent complete containment of the LOCA which is beyond design basis. For purposes of analysis in this report, a LOCA will be assumed when any single component or system within the containment is struck by a missile. This is a very conservative assumption, as a single component failure inside the, containment (such as a RCFC or main steamline) does not necessarily result in a LOCA.

The second scenario involves missiles striking clant components outside of containment resulting in loss-of-hot-shutdown capa-bility, but in response to the requirements of Regulatory C.4-1

n...-_ ... . . . . . ~ ~ . - - . - . - - . - .- --.- ~ .-

l B/B-FSAR Guide 1.115, this scenario will also address loss-of-cold-shutdown capability and is designated as M. Thus, for th'e purposes of this analysis, an accident beyond design basis is assumed if M or C occurs.

The plant logic for M and C is presented by means of a fault tree. The master fault tree is given in Figure C.4-1. Further branch expansions for M are shown in Figures C.4-2 through C.4-14. The branch for C is shown in Figure C.4-2, and it simply consists of the 20 components / equipment listed as con-tainment targets 1.1 through 1.4.3 in Table C.3-1. Each event in the fault tree represents an important plant component or components, the failure of which is assumed to result in failure to achieve cold shutdown or LOCA.

The circle below each event in the fault trees reoresents the space designtaion in which one or more of those components are located or through which cabling or piping are routed.

Turbine missile entry into a space is assumed to result in failure of all components in that space. The symbol Q represents an OR condition whereby the failure of any event in the branch would result in failure of the branch. The symbol O indicates an AND condition such that all events immediately below the branch must fail in order for the branch to have failed.

In this way, the fault tree can be interpreted as indicating the space combinations which, if penetrated by a turbine missile, will lead to M or C. This assumption is conservative because, in most cases, the components of interest do not consume the entire space in which they are located, and a missile entering the space may not necessarily impact the component. In addition, failure of the components may not.necessarily result in the assumed accident.

l I

It is noted that operator interdiction is not included in

( the fault tree. This is a conservative assumotion as including l recovery actions would result in lower failure frequencies.

It has been shown in Reference 1, that for certain components,

( failure to start on demand is significant, thus, this is included in the fault tree where appropriate. Table C.4-2 lists the median frequency and assessed range of these special conditions.

Before proceeding, it is important to note some points in the fault tree logic. It is assumed that for the.1 tree pumps, failure of the control room or DC power does not mean failure to start or stop the pumps. The switchgears for these pumps can be operated mechanically. Also, it is again pointe 1 out that conservatism is involved when the containment is breached.

C.4-2

l

. . . . . . . . . . . . . . . . . _ ~ . . . _ . . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ l l

B/B-PSAR l l

To realistically create a situation leading to M or C, primary I and secondary (backup) systems within the containment would need to be damaged simultaneously. In this analysis, it is  !

assumed that any single component or system damaged inside containment constitutes an accident beyond the design basis. , i It is necessary to use the fault tree as a basis for identifying ,

the space combinations which, if penetrated, will lead to M or C. The computer program SLRAS (Reference 2) was used for this purpose. From the fault tree and all of its branches, the minimal cut sets, or minimum failure event paths which ,

lead to the undesirable event were identified. Each of these l minimal cut sets is identified as C3 in Subsection C.2.4.

From the analysis of Figures'C.4-3 through C.4-14, Table C.4-3 is obtained. This table lists the minimal cut sets leading to i the damage state defined as loss-of-cold-shutdown capability (M).

1 Table C.4-3 includes all the cut sets with two or less space hits; cut sets with more than two events have not been included because the event of one missile penetrating three zones is not realized according to discussion in Section C.5.

For C, each of the components represents a minimal cut set, and a computer analysis of the C-fault tree is not necesary.

C.4.3 Damage State R It is conservatively assumed that any breach of containment or loss-of-cold-shutdown capability could also result in a radiological release. The Boolean expression for the occurrence of this damage state can be written as:

)

R= CUM (C.4-1)

Thus for this analysis, there is only one offsite release and it is assuemd to be the worst case scenario. l C.4.4 References l l

1. N. J. McCormick, " Reliability and Risk Analysis - Methods )

and Nuclear Power Applications," Academic Press, New York, 1981.

2. Sargent & Lundy Computer Program, Program No. 09.7.203.  !

C.4-3

TABLE C.4-1 f DEFINITION OF DAMAGE STATES AND THEIR RELATION TO ' .  !-

NRC REGULATORY GUIDE 1.115 CRITERIA '.

I DAMAGE STATE NRC REGULATORY GUIDE -

(C) DEFINITION 1.115 CRITERION  !

.c It C Damage of reactor coolant a Damage of the integrity of the reactor system components coolant pressure boundary l l

to n

M Loss of cold shutdown Loss of the capability to shut down the N h

. Capability reactor and maintain it in a cold shut-i down condition R Excessive offsite releases Loss of the capability to prevent acci-(R = M dents that could result in potential ,6 offsite exposures that are a significant ,1 f raction of the guideline exposures of 10 CFR Part 100, " Reactor Site Criteria." ll

.l 4

L e

G

-__.--- - - -- ~- ---. -

TABLE C.4-2 -

l i

e t.

FREQUENCY OF COMPONENT UNAVAILABILITY ,

l.

ASSESSED ERROR -

MEDIAN

• RANGE

• FACTOR

• EVENT f'

-2 -2 -1 3 FSDAFW2 - Failure of diesel-driven auxiliary 3x10 lx10 to 1x10 feedwater pump to start on demandt i

-2 -2 -1 ,I FSDDIEl -

Failure of Vivision 11 diesel 3x10 1x10 to 1x10 3 generator to start on demand. W ,l

=8 i;.

I:

n. 4 6+

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a f55 l -2 -2 -1 '

FSDDIE2 Failure of Division 12 diesel 3x10 lx10 to lx10 3 $

f,:

generator to start on demand.  !

l l

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• See Reference.1 (Section C.4) . ,,

r-i . -  !

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B/B-FSAR TABLE C.4-3 MINIMAL CUT SETS FOR DAMAGE STATE M CUT SET 1 BASIC EVENT

~

l 11.6-0 2 11.5-0 3 11.4-0 4 11.2-0 5 11.3-0 6 11.3-1 7 11.2B-1 8 ll.3F-1 9 0-2 10 0-3 11 18.25-1 12 5.S-1 i, -

l CUT SET 2 BASIC EVENTS

1 5.4-1 11.SA-1 2 2.1-0 11.5A-1 3 2.1-0 ll.4C-0 l 4 2.1-0 5.2-1 5 2.1-0 ll.6A-1 6 11.6-1 11.SA-1 7 11.6-1 5.2-1 0

C.4-6

. . . . . . . -.. - - - - - - - s-- -- - --- - --

• e

• B/B-FSAR TABLE ' C. 4-3 (Cont ' d)

CUT SET 2 BASIC EVENTS 8 3.2A-1 ll.5A-1 9 3.2A-1 5.2-1 10 3.2B-1 ll.5A-1 11 3.2C-1 '1.5A-1 12 11.5A-1 5.2-1 13 3.1-1 5.2-1 14 3.1-1 11.1-1 l 15 3.1-1 17.2-1 l 16 5.1-1 5.2-1 17 5.1-1 11.1-1 18 5.1-1 ll.3B-1 19 5.1-1 ll.2A-1 20 5.1-1 17.2-1 21 11.2C-1 5.2-1 22 ll.2C-1 ll.3B-1 23 ll.2C-1 li.2A-1 24 ll.2D-1 5.2-1 25 ll.2D-1 ll.3B-1 26 ll.2D-1 ll.2A-1 27 5.2-1 11.1-2 28 5.2-1 ll.3E-1 29 5.2-1 17.2-2 30 11.1-2 11.1-1 C.4-7

_---- -=_ .- .;-. _.2 ; _ _ _ _ _ _ __

. B/B-FSAR

,, TABL3 C.4-3 (Cont'd)

CUT SET 2 BASIC EVENTS ,

31. 11.1-2 17.2-1

32. 11.1-1 18.10E-1 33 11.1-1 0-1 34 11.1-1 17.2-2 3K 9.2-1 18.10E .?

l 36i 9.2-1 0-1 i

37 11.3E-1 11.3B-1 l 38' 11.3E-1 11.2A-1 39 17.2-2 17.2-1

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l 9

C.4-8 l

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l ACCIDENT BEYOND DESIGN BASIS 7%

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. FIGURE C.4-1: TURBINE MISSILE FAULT TREE i

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FIGURE C.4-2 LOCA RESULTIMG FPOM BP.EACil OF CONTAINMENT l

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FIGURE C.4-8: LOSS OF SERVICE WATNR - '

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9.3-1 } l 1.2-1

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FSDDIEL f I

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CENEPATOR IlX. SW PUMP SWITCIICEAR I, CO:.7ROLS OPEPATIO:4S O. (h \(..s-t () \

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SATTERY OR FAILURE OF + TAILURE Or gg,g.g DC E PANEL FAILURE CA2LOS FOR DAY TANK FUE L O ! L T *.'.t .

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. 3/B-FSAR C.5 PRESENTATION AND DISCUSSION OF RESULTS

! C.5.1 General .

l This section discusses the manner in which formulations were used in Section C.2, plant model in Section C.3, and plant logic in Section C.4 to identify' contributors to turbine missile risk in the Byron /Braidwood Stations. Conservative evaluations have been made throughout the analysis. Results indicate that a practical turbine inspection time can be determined with an acceptably small risk due to turbine missile hazard.

)

C.5.2 conditional Frequencies of Damage States It is shown in Equation C.2-3 that the conditional f requency of a certain damage state q at speed condition wg is less than the frequency given by the expresion 2 ICj!"i

• f I 3-1 The quantities f, (C 4lw;) at speed condition w are estimated by the simulation process for the specific min, mal cut sets I c4 of each damage state due to turbine missile hazards as ddfined in Table C.4-1. *

~

l , results from 1000 simulation For each speed trials were sorted to calc condition wblate the required conditional frequencies. Table C.5-1 shows the calculated conditional and frequencies f2 (C4lWa) forThe thecontributing three speed targets conditions to wg,h eac the three damage states.

frequency and their percent contributions are also identified in this table.

The main contributors to damage state C are failures of the steam generator (target 1.3.3), the containment spray main riser (target 1.2.lY), and the main steam and feedwater piping (target 1.2.lA) . Damage to the spray riser and main steam and feedwater piping would not actually result in either a LOCA or failure to attain cold shutdown conditions but were included because of their safety functions. It is expected that a more detailed analysis could significantly reduce the contribution of these targets. ,

It is noted that damage state C is realized only under the l design overspeed and the destructive oversoeed conditions.

This result indicates that no missile would be able to damage l any of the specified containment targets at the rated speed condition.

Damage state M is realized under all the three speed conditions.

The main contributors to this damage state are:

a. failure of essential service water and condensate i

storage pipings (target 0-2) .

I C.5-1

\

. . . . . . ., __=__=,_-..

, . ..~._

• B/B-FSAR

b. failure of electrical panets and NVAC equipment  ;

(target 5.5.1). This target contributes only i

at the destructive overspeed condition. ,

It follows from Equation C.4-1 that the major contributors i for damage states C and M are also major contributors to the '

damage state R. It is also noted from Table C.5-1 that the minimal cut sets with two basic events make minor contribution to the calculated frequencies. Minimal cut sets with three or more basic events did not provide any contribution in the 1000 trials for all the speed conditions.

C.5.3 Frequency of Plant Damage States per Year To assess the significance of turbine missile risk, values of the frequency of damage states per year have been examined

' for various turbine operating times. By using from the values Table C.2-1 from Table C.5-1, and the values of f i of f,he for f Byron Station Unit 1 turbine, This and applying table presents Equation frequencies C.2-1, Table C.5-2 was prepared. -

per year of three damage states for values of continuous turbine i

operating time since last inspection equal to 1, 2, 3, 4, 5 and 10 years. The percent contribution from each of the three turbine failure speed conditions are also given in the table. Thene results are also plotted in Figure C.5-1. It is noted frcm this information that the frequencies of the three damage states depend on the turbine inspectionThe interval increaseAt.

These frequencies increase with the Increase of At.

in frequency of damage state M (or R) is greater than that of damge state C this is because damage state M (or R) occurs at any of the three speed conditions while damage state C occurs only at the design overspeed and destructive overspeed conditions (see Table C.5-2) .

It is emphasized that a number of conservative assumptions have been used to obtain the results shown in Figure C.5-1.

! These sources of conservatism are listed below:

a. Targets are modeled as cubicles larger than the actual size of the safety-related equipment, thus increasing the changes of the targets being hit by missiles.

b. After a missile enters a cubicle, all the safety- l related equipment inside the cubicle is considered damaged. No credit is taken for the possibility

- j of partially damaged equipment. l

c. Reinforced concrete walls and slabs with thicknessen

.less than 6 inches are ignored in the plant mode ling.

C.5-2 i.

+ - =

n .2.- ., , . , , , , ,

a . B/B-FSAR

d. The entire blockwalls, sidings, and gratings are

' assumed to offer no resistance to the motion of the missile.

e. All equipment devices (safety-related or non-safety-related) except moisture separators and steam generators are assumed to offer no resistance -

to the motion of the missile.

f.

The design values of concrete strength are used in the analysis; the increase in strength for aged concrete is not taken into consideration.

g. It is assumed that any one of the containment targets listed in Table C.3-1 being damaged will Actually, result in a loss-of-coolant accident.

only six of the twenty targets (reactor pressure vessel, prassurizer, and four steam generators) contain reactor coolant and, if severely damaged, The could be considered the source of a LOCA.

remaining fourteen targets are included because of the potentia'l of subsequent damage to the reactor coolant system or the potential loss of redundant elements of the safety systems.

Inviewoftheagoveconservatismintheanalysis,adamage frequency of 10 per turbine unit per year is consideredUsing this as acceptably small.

has the highest frequency of the three damages studied, Figure C.5-1 Therefore, yields an inspection time of 3.6 years (43 months) .t will be in conformance with Regulatory Guide 1.115 if the low pressure turbine discs are inspected using an inspection interval not exceeding 43 months and measured in terms ofFor turbine running time. if wood Station Units 1 and 2, the same conclusion should values, when available, are found to apply their corresponding fl be less than or equal to that of the Byron Unit i values.

C.5-3

.__: =-

y ii

. rt

):

. . :t n

TABLE C.5-1 U

. 'f CONDITIONAL FREQUENCY OF ' HIE THREE DAMAGE STATES '

FOR THREE SPEED CONDITIONS :i f 2I C I"lI <

1 l g g RATED SPEED DESIGN CVERSPEED DESTRUCTIVE OVERSPEED +i (C} f 2IC/"1) CO m IB m RS COMIBmM l :; , "

1 f 2I5!"2) f 2IE /*'3) CONTRIBUTORS -

Damage of Reactor 0.00 None

! Coolant System 2.0x10~3 1.3.3 (1004) 17.5x10~3 1.2.lY (52.4%) h i Components 1.3.lA (34.3%) -

n C 1.4.3 (7.6%) ( ,

m 1.2.5 (5.7%) m S  !

1.0x10 -3 -3 Loss of Cold 0-2 (1004) 8.0x10 0-2 (1004) 20.0x10~3 0-2 (50%) l

Shutdown Capability 5.5-1 (304)  :'

0-3 (104)

.' M

18.25-1 (54) .

~~]'

17.2-1 and t,'

l' , 17.2-2 (54) ~~[,

9c .

l- Excessive Offsite 1.0x10~3 Same as that 10.0x10 ~3 Sum of the 37.5x10~3 Sum of the Releases of the second above two R row above two -- '

rows rows '

(R = CUM) f;!

l-

,F NOTE:

Numbers in the parentheses indicate the percent contribution of the target (s) to the conditional frequency at the specified speed condition.

f, F

a s e

. N -

- s

\ . $

~

e.

, t.

. ~_

s.

^

.T .

s g

s TABLE C.5-2 13 x

'z '

FREQUENCY PER YEAR Or nkMAGE _ t!*tATES *

, =~..'

3 s . w..

f (C, At) f 2(C/e glf g(Wg,At)

N = ,

N .

DNE ' ' N SUN OF ALL SPUD _ CONDITIONS STATE ~

At = 1 yr at = 2 yr at = 3 yr at = 4 yr at = 5 yr at = 10 yr J,

~ s

' m

,n C i

g l

?

' 4~

w x .

4 g

M t

, I s

. i

.== . . . l i -

,, r

.w

~ '

NOTE: Numbers in the parentheses indicate percent contttbution from rated speed, design overspeed, and destructive overspeed respectively.

'~ .

~ . . . -

P

. w b

s a

~ . . . . . . . . . . . . . . . _ . . . . . .. . . _ . . _

o , w iv - r ><iis

- a -

,3".

A E

>9 ,

N .

x u

K V

'5 V

98 A

u_.

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.3, R 3ure C. 5-1 I~"i~ y b" Y" r

. of dh4 Vo c ; ass Dwv3e

'% ies L .h.: t of' L bia4 Ivu:pedion Time

.- _= =  : - w --. - - --. .

_ 7 33 _ .

l B/B-FSAR i

C.6

SUMMARY

AND CONCLUSIONS A probabilistic analysis of turbine missile hazard for the Byron /Braidwood Stations has been made using plant logic through a fault tree analysis and a three-dimensional plant model for missile trajectories. In the simulation model, numerous .

reinforced concrete barriers based on plant layout were used

• and their perforation velocity was calculated using CEA-EDF '

formula. The model also included a few steel barriers whose perforation velocity was obtained using BRL formula. Possibility of missile ri.cochet was also considered in the simulation model.

The most recent information for values of missile generation probabilities which are available for the Byron. Unit 1 turbine from Westinghouse Electric Corporation (" Turbine Missile Report,"

Report No. CT-24890, Rev. 3, March 1982) is used in the analysis.

1 The study considered missile generation at rated speed, design overspeed, and destructive overspeed conditions. The major findings of this analysis are as follows:

)

a. .The values of probability of damage to the reactor coolant pressure boundary, loss of safe shutdown capability, and significant radiological release l

all depend on the turbine inspection time as shown in Figure C.5-1.

b. The results in item a above have been obtained using conservative assumptions enumerated in Sub-section C.5.3. Therefore, it is consider a proba'ility o of 1 x 10-geasonable to per turbine unit per year as an acceptably small limit for turbine missile damage.

'c. It follows from item b above that operation of the turbine at Byron Unit 1 will be in conformance I with Regulatory Guide 1.115 if the low pressure turbine discs are inspected at intervals no longer than 43 months in turbine running. time since previous inspection. This criterion make per year to be less than 1 x 10~g damage probability j

d. The conclusion in item c also will apply to turbines of Byron Unit 2 and of Braidwood Units 1 and 2 l if the probabilities of missile generation for these units are demonstrated to be less than or equal to probabilities used in this report for the Byron Unit 1 turbine.

c.6-1

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