ST-HL-AE-1802, Requests Deletion of Tech Spec Surveillance Requirements for Turbine Overspeed Protection,Per SER (NUREG-0781) Requirement to Implement Inservice Insp Program for Stated Valves.Encls Include Justification & Proposed Tech Specs
| ML20212A246 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 02/24/1987 |
| From: | Wisenburg M HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-0781, RTR-NUREG-781 ST-HL-AE-1802, NUDOCS 8703030313 | |
| Download: ML20212A246 (22) | |
Text
-
The Light NE U
1fouston Lighting & I ower itO. Box 1700 llouston, Texas 77001 (713) 228-9211 x
February 24, 1987 ST-HL-AE-1802 File No.: G9.06 10CFR50.36 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Deletion of Technical Specification Surveillance Reonirements for Turbine Oversneed Protection The South Texas Project Electric Generating Station (STPEGS) Safe!.y Evaluation Report (SER), NUREC-0781, Section 10.2, requires HL&P to implement an inservice inspection program for the main steam throttle, governor, reheat stop and interceptor valves. This program will include (1) the dismantling and inspection of one of each type of turbine steam valves at approximately 3-1/3 year intervals during refueling or maintenance shutdowns coinciding with the inserrice inspection schedule, and (2) exercising and observing at least once a weenc, the main steam stop, reheat stop, and interceptor valves.
Additionally, SER Section 10.2 requires that this commitment be included in the plant Technical Specifications.
NRC Proof and Review South Texas Unit 1 Technical Specification 3/4.3.4 requires periodic surveillance testing and inspection of turbine valves to demonstrate the operability of the turbine overspeed protection system. These surveillance requirements are intended to provide protection from excessive turbine overspeed conditions and thereby minimize the potential for the generation of missiles.
Turbine valve testing typically requires a reduction in power, resulting in lost electrical generation and thermal cycling on piping and equipment.
Minimizing the frequency of turbine valve testing, as allowed by applicable criteria, reduces these effects and results in an improvement in plant availab ility.
0703030313 870224 Q2)H ADOCK 05000498 m
l'DR L3/NRC/bbi
liouston Lighting & Power Company ST-BL-AE-1802 File No.: G9.06 Page 2 Based upon~ the subjection of the nuclear steam supply system to unnecessary cyclical power transiests, the cost to perform the surveillance test without concomitant safety benefits, and the potential for turbine missile generation being below that for which Technical Specification surveillauce is required HI4P respectfully requests that the requirement for inclusion of turbine valve test frequency into the Technical Specifications be deleted.
In 1982, Alabama Power Company (APCo) submitted a similar proposal to change the Farley Nuclear Plant Unit 2 Technical Specifications such that.
turbine valve testing requirements would be deleted. The basis for this request was the results contained in WCAP-10161, where the reliability of the turbine overspeed protection system and the potential for turbine missile e
generation was evaluated. The evaluation considered three cases of. turbine overspeed where each overspeed case was-compared with the potential for missile generation. The results of the evaluation showed that the probability for missile generation was below that requiring technical specification surveillance based on annual testing of the turbine valves and an inspection of the low-pressure turbine discs every five years. The NBC agreed to approve deletion of specific prescriptive requirements in the Unit 2 turbine overspeed protection Technical Specification provided APCo submit a Technical Specification change to reference the Farley Nuclear Plant " Turbine Overspeed Reliability Assurance Program" (TORAP).
One question raised by the NRC with regard to the APCo submittal was whether the possibility existed for a turbine overspeed incident resulting from backflow from a feedwater heater via a steam extraction line.
HI4P addresses this issue in FSAR Section 10.2.2.8.3; it is not appilcable to the South Texas design.
STPEGS is committed to implementing a turbine system maintenance program which will be submitted to the NRC within three years of obtaining an Operating License. This program will specify the frequency of turbine valve testing. Attachment 1 to this letter expands upon each of the above bases and provides a detal_ led justification for deleting turbine valve testing from the Technical Specifications. Attachment 2 delineates the South Texas Turbine Overspeed Reliability Program (TORP) requirements which will ensure operability of the Turbine Overspeed Protection System. Attachment 3 is the proposed deletion of the turbine valve test frequency surveillance with the resulting reference to the South Texas TORP as part of Technical Specification 3/4.3.4 Surveillance Requirements. Attachment 4 is the annotated pages from FSAR Section 3.5.1 reflecting the revised turbine missile risk analysis.
Additionally, FSAR Section 10.2.4 will be revised to delete the commitment for weekly functional testing of the turbine valves in a future amendment.
L3/NRC/bbi
,. _ ~ _.,, _ _,.,,,.. _ _., _. _. - _,, _ _ _ _ _
,_.,,,__.__..,,,_,,,_,m.-,..,..,,._m_.._,,,.
.,.,,,_ym,_
Ilou. ton Lighting & Power Company ST-HL-AE-1802 File No.: G9.06 Page 3 If you should have any questions on this matter, please contact Ms.
F. A. White at (512) 972-7985.
(
V L w-M. R. Wis aburg Deputy Pro *ect ager FAW/1ja S
Attachments:
(1) Justification for Deletion of Turbine Valve Testbg at STP (2) STPEGS Turbine Overspeed Reliability Program (3) Proposed Proof and Review Technical Specification 3/4.3.4 (4) Annotated Revisions to FSAR Section 3.5.1 L3/NRC/ bbl
Houston Lighting & Power Company ST-HL-AE-1802 File No.
G9.06 Page 4 CCI Regional Administrator, Region IV M.B. Lee /J.E. Malaski Nuclear Regulatory Commission City of Austin 611 Ryan Plaza Dr(ve, Suite 1000 P.O. Box 1088 Arlington, TX 76011 Austin, TX 78767-8814 N. Prasad Kadambi, Project Manager M.T. Hardt/A. von Rosenberg U.S. Nuclear Regulatory Commission City Public Service Board 7920 Norfolk Avenue P.O. Box 1771 Bethesda, MD 20814 San Antonio, TI 78296 Robert L. Perch, Project Manager Advisory Committee on Reactor Safeguards U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commaission 7920 Norfolk Avenue 1717 H Street Bethesda, MD 20814 Washington, DC 20555 Dan R. Carpenter Senior Resident Inspector / Operations c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TI 77414 Claude E. Johnson Senior Resident Inspector /STP c/o U.S. Nuclear Regulatory Commission l
P.O. Box 910 i
Bay City, TX 77414 M.D. Schwarz, Jr., Esquire Baker & Botts One Shell Flaza Houston, TI 77002 J.R. Newman, Esquire Newman & Holtzinger, P.C.
1615 L Street, N.W.
Washington, DC 20036 T.V. Shockley/R.L. Range Central Power & Light Company P. O. Box 2121 Corpus Christi, TI 78403 L3/NRC/bb1 Revised 2/3/87
Attachmext 1 ST-BL-AE-1802
[
'Pags 1 of 2
.fBSTIFICATION FOR DELETION OF TURBINE VAIXE TESTING AT STP Law Parentini for Miamila consention
- As stated in the STPEGS FSAR Section 3.5.1.3.6 the results of the South Texas turbine missile risk analysis demonstrate that.the arrangement of South Texas ~is acceptable against postulated turbine missiles that may be generated under a design or a destructive overspeed condition. The analysis has been revised to clarify the assumptions regarding the blocking of missiles by the turbine pedestal; to update the P2/P3 values for the DGB and ECW intake structure and reflect the commitment to a turbine maintenance program. The-attached annotated pages from FSAR Section 3.5.1 are provided for your review.
These changes will be submitted as part of a future FSAR amendment. Four analyses were performed to determine the worst total probability of an -
unacceptable turbine missile event'(P4). The worst. total probability (P4) is 0.9283 x 10E-7 which is obtained by multiplying 6 x 10E-5 (P1) by 1.5472 x 10E-3 (P2/P3) where P1 is the probability of the generation and ejection of high-energy missiles, P2 is the probability that a missile from the turbine generator-(TG) strikes a Category I target, and P3 is the probability that the missile scabs or perforates the seismic Category I barrier. This is below the allowable limit of 10E-7.
The above conclusion shows that the worst-case probability for turbine missile generation is well below the missile generation prebstility guidelines of 10E-4 incidents per year established in Regulatory Guide 1.115 and is less than the acceptance criteria of 10E-7.
Thus, the turbine system reliability is shown to meet the intent of the Technical Specification turbine valve test frequency requirement.
Ef fse tivenmaa of Turbine Valve Testine Historically, Westinghouse has recommended that turbine valves be tested periodically. A weekly test frequency originated in the mid-1950s primarily as a result of fossil plant experience and in recognition of the importance of reliable turbine-generator operation as it related to personnel and equipment protec tion. The rignificance of this testing relative to nuclear safety was never clearly estaclished. Feverthelcas, the periodic valve testing recommendation evolved into a license requirement for certain nuclear power plants by virtue of its inclusion as part of plant Technical Specifications.
For some plants the Technical Specifications require weekly testing, for others, monthly testing, and for some plants there le no Technical Specification requirement for turbine valve tests.
Turbine valve testing typically requires a power reduction during the test, resulting in lost electrical generation and thermal cycles on piping and equipment. Minimizing the frequency of turbine valve testing, as allowed by applicablu criteria, reduces these effects and results in an improver.ent in overall plant svailability. Valve testing does not preclude degradation leading to a valve failure mode and has little recognized value in detecting an incipient condition leading to failure. The primary benefit of valve testing /obsetvation is the potential for detection of failed valves.
t.
L3/NRC/ bbl
~
.~..
ST-BL-AE-1802 Pags 2 cf 2 As specified in South Texas FSAR Section 3.5.1.3.6 and SER Section 10.2, Westinghouse, the South Texas Turbine supplier, is committed to perform an evaluation in order to establish appropriate inspection intervals which will justify the lower P1 values. The inspection interval will be detailed in a turbine system maintenance program which will be submitted to the NRC for approval within three years of obtaining an Operating License (OL).
Based on the lack of a demonstrated safety need for frequent turbine valve testing and the inconsistency with which the requirement to test turbine valves has been applied, the deletion of the requirement to include turbine valve testing / observation surveillance requirements in the Technical Specifications would have no adverse impact on the reliability of turbine operations nor reduce overall plant safety.
No Coat / Safety Banafits The performance of valve testing represents unjustified loss of electric generation and unnecessarily subjects the nuclear steam supply system to cycilcal power transients. - The performance of the weekly Technical Specification valve test requires power reduction to approximately 85%. The estimated cost of replacement power to perform this weekly turbine valve test is $42,000 per month or $550,000 per year per unit. The relative ineffectiveness of the valve testing / observation to provide increased assurance of the operability of the turbine, coupled with the unnecessary cyclical power transients and the economic loss associated with its performance, justify the deletion of valve testing / observation from inclusion in the Technical Specifications.
4 Conclusion Based upon the low potential for turbine missile generation, the ineffectiveness of turbine valve testing, the lack of a demonstrated safety need for frequent turbine valve testing, the inconsistency with which the requirement to test turbine valves has been applied, and the Westinghouse Owners Group turbine valve test evaluation, the requirement to include turbine valve testing in the South Texas Technical Specifications may be deleted without adverse impact on turbine reliability and without a reduction in overall plant safety.
w 1
L3/NRC/bbi t
ST-HL-AE-1802 Page 1 of 5 South Texas Project Electric Generating Station Turbine Overspeed Reliability Program (TORP) 1.0 Introduction and 9 mmary Houston Lighting & Power has contracted the Westinghouse Electric Corporation to perform warranty inspections on the turbine and generator systems during the initial three scheduled refueling outages. The work scope outlined for these inspections ensures the availability and reliability of the turbine-generator unit, and meets the requirements of the Alabama Power Company TORAP program. Upon completion of the contractual period, HL&P will implement a turbine maintenance and inspection program at STP which meets or exceeds the program developed by Westinghouse. The HL&P program will be implemented within 3 years of receipt of obtaining the STP Unit 1 Operating License, and will reference Westinghouse recommendations.
The scopa of work for the first three outages has been outlined in the Westinghouse contract with details of the program summarized in the following pages. The program developed by HL&P will be subject to on-going reviews and evaluations, and the scope of the performed maintenance, calibration, and testing will be subject to revision based upon actual operating experience or changes to the manufacturer's recommendations. The program work will be performed in accordance with either approved procedures or maintenance work requests. The program and any subsequent changes will be reviewed and approved as specified in existing plant administrative procedures. All deviations from the program and deficiencies identified through the specified activities will be evaluated by Houston Lighting & Power to determine appropriate action to be taken such as correcting the deviation or deficiency, performing compensatory action, or removing the turbine from service.
The maintenance program is discussed in Section 2.0 and includes inspection and maintenance of the throttle, governor, reheat stop and intercept valves.
The calibration program is discussed in Section 3.0 and includes calibration of the turbine overspeed protection system. Calibration is performed during each refueling outage or following major maintenance on the turbine generator or the overspeed protection system.
Attrchment 2 ST-HL-AE-1802 Page 2 of 5 The testing program is discussed in Section 4.0 and includes testing of the turbine valves and the turbine overspeed protection system. Testing is performed during each turbine startup, unless tested within the previous seven (7) days, including startup after each refueling outage.
The testing program shall include a complete test of all turbine valves on an interval established by Westinghouse.
2.0 Maintenance Program The maintenance program includes inspection and maintenance of the governor, throttle, intercept and reheat stop valves. As stated in STPEGS FSAR Chapter 10, the turbine assembly, including inaccessible parts, will be disassembled and inspected in sections such that at the end of a 10 year period, the entire turbine has been inspected.
Additionally, one of each type of turbine valves will be dismantled and inspected at approximately 36-to 39-month intervals.
The maintenance program to be followed during the contractual period includes the schedule and work scope outlined below:
1.
First Outage Inspection a.
Complete generator and exciter inspection.
b.
Inspect all throttle and reheat stop valves.
c.
Visual inspection through three low pressure turbine manways.
2.
Second Outage Inspection a.
Complete inspection of high pressure and one low pressure turbine element.
b.
Inspect all reheat stop and interceptor valves.
c.
Visual inspection through two low pressure turbine manways.
d.
Generator crawl through inspection.
3.
Third Outage Inspection Complete inspection of two low pressure turbine elements.
a.
b.
Inspect all throttle and governor valves.
c.
Visual inspection through one low pressure turbine manway.
d.
Generator crawl through inspection.
2.1 Throttle Valve Inspections Includes disassembly of the valve by removing the linkage, springs, and bonnet assemblies; hand cleaning valve stem bushings and checking for proper bore diameter; hand cleaning and performing NDE on valve stems,
a ST-HL-AE-1802 Page 3 of 5 valve nuts, valves, bonnet studs, and spring housing studs; checking all pins and bushings for proper clearances and recording clearances; dust blesting and performing NDE on the bonnet and spring housing nuts and washers, and reassembly of the above.
2.2 Governor Valve Inspections Includes disassembly of the valve by removing the linkage, spring housing, and bearing supports; hand cleaning valve stem bushings and checking for proper bore diameter; hand cleaning and performing NDE on valve stems, valve nuts, valves, bonnet studs and spring housing studs; checking all pins and bushings for proper clearances and recurding clearances; dust blasting and performing NDE on the bonnet and spring housing nuts and washers, and reassembly of the valve.
2.3 Interceptor and Reheat Stop Valve Inspections Includes disassembly of the valve by removing the linkage, spring housing, bearing supports, seal assemblies and valve shaft; dust blasting the valve shaft and seal housing; performing NDE on the valve shaft, main valve, and seal assemblies; checking and recording assembly clearances for valve shaft, bearings, seals and linkage, and reassembly of the valve.
2.4 Actuators of Inspected Valves Includes disassembly, as necessary, to inspect one actuator; visually inspect piston, cylinder wall, and piston rod bushings; check piston rings for freedom in grooves; install a new seal kit, end reassemble the actuatcr.
2.5 Valve Linkage Visually inspect all pins and bushings for proper clearance and freedom of movement.
3.0 Calibration Program The turbine electrical and mechanical overspeed trip calibration tests will be performed at refueling outage intervals in conjunction with the turbine overspeed and protection device testing.
3.1 Electrical Overspeed Trip Calibration The electrical overspeed trip test will be designed to verify the calibration of the digital speed indicator, the trip value (103%) of the turbine overspeed trip channel, and the gap clearance on the speed pickup device. As-found values will be recorded and compared to expected values, and if as-found values are out of tolerance, the equipment will be adjusted and the testing repeated. This testing assures proper calibration of the electrical overspeed trip device.
[
ST-HL-AE-1802 L
Page 4 of 5 s
3.2 Mechanical Overspeed Trip Calibration The mechanical overspeed trip test will be designed to verify the calibration.of the trip system by observing an actual overspeed trip (111%) and recording the value at which the trip occurs.
If the as-found trip value is out of tolerance, the trip setpoint will be adjusted and the test will then be repeated. This testing assures proper calibration of the mechanical overspeed trip device.
4.0 Testina Program The testing program includes testing the turbine valves and the turbine overspeed protection system. Testing is performed during each turbine startup, unless tested within the previous seven (7) days, including startup after each refueling outage.
4.1 Turbine Startup Testing 1
The turbine startup testing is performed during each startup unless performed within the previous seven (7) days. This testing includes:
4.1.1 Manual Trip Test The turbine will be manually trip dfromratedspeedusingthb Turbine trip pushbutton on the Vain Control Board. Proper operation of the trip system and the turbine valves will be verified.
4.1.2 Mechanical Overspeed Oil Pressure Trip' Test Oil pressure will be opplied to the turbine's mechanical overspeed oil, trip device with the turbine at rated speed in' order to verify proper operation. The trip signal causes the interface valve to open, but the trip oil is blocked such that the turbine dces not actually trip. This test will also be performed monthly during normal operations.
OverspeedProtectior[fontrol(OPC) Test 4.1.3 The OPC (103% turbine overspeed protection feature) will be tested in order to verify that the turbine governor and interceptor valves close as expected.'
I
\\
b
E' ST-HL-AE-1802 Page 5 of 5 4.1.4 Remote Trip The turbine will be manually tripped from rated speed using the remote trip lever at the turbine governor pedestal. Proper operation of the trip system and the turbine valves will be verified.
4.2 Refueling Outage Testing The turbine electrical and mechanical overspeed trips (111% turbine overspeed protection feature) will be tested each refueling outage or when major maintenance is performed on the turbine.
4.3 Shutdown Turbine Trip Verification The shutdown turbine trip verification will be performed during each planned shutdown of the unit. This test will require an operator to verify by observation that the turbine valves actually close during each planned shutdown. This test will also require the operator to verify that the turbine valve positions are properly indicated on appropriate panels.
4.4 Turbine Valve Test The turbine valve test will be performed on all turbine valves on an approximate four month interval. This test will require each turbine valve to be cycled to demonstrate free operation as the valves close and reopen. This test will be run from the Main Control Room with an operator verifying valve operation by direct observation.
L
i ST-HL-AE-1802 l
Page 1 of 1 PROOF & REVIEW COPY INSTRUMENTATION 3/4.3.4 TURBINE OVERSPEED PROTECTION LIMITING CONDITION FOR OPERATION 3.3.4 At least one Turbine Overspeed Protection System shall be OPERABLE.
APPICABILITY: MODES 1, 2, and 3.
ACTION:
a.
With one stop valve or one governor valve per high pressure turbine steam line inoperable and/or with one reheat stop valve or one reheat intercept valve per low pressure turbine steam line inoperable, restore the inoperable valve (s) to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or close at least one valve in the affected steam line(s) or isolate the turbine from the steam supply within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
b.
With the above required Turbine Overspeed Protection 5' stem otherwisa y
inoperable, within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> isolate the turbine from the steam supply.
SURVEILLANCE REOUIREMENTS 4.3.4.1 The provisions of Specification 4.0.4 are not applicable.
- The turbine overspeed protection system will be maintained in accordance with the South Texas Project Tu1bine Overspeed Reliability Program.
Th7 program will be performed in accordance with procedures, maintenance.
work m ests and/or outage work schedules as appropriate. All deviatio..s from the program or deficiencies identified through the specified maintenance, calibration or testing activities will be evaluated by Houston Lighting & Power to determine if operability of the system has been affected and appropriate action taken such as correcting the deviation or deficiency, performing compensatory action or removing the turbine from service.
The Turbine Overspeed Reliability Program is the subject of on-going review and evaluation by Houston Lighting & Power such that changes in scope and/or schedule may be made as appropriate; however, the objective of maintaining the high reliability of the turbine overspeed protection system will be met. The program and any subsequent changes will be reviewed and approved as specified in existing plant administrative procedures.
- Specification not applicable with all main steam isolation valves and associated bypass valves in the closed position ano all other steam flow paths I
to the turbine isolated.
I i
THIS PAGE OPEN PENDING RECEIPT INFORMATION FROM THE APPUCANT I
SOUTH TEXAS - UNIT 1 3/4 3-83
ATTACHMENT 4 ST-HL-AE-1802 STP FSAR PAGE 1 o' 10 P = total probability of an unacceptable turbine missile event 4
The probabilities of P2 and P were calculated for each Seismic Category I 3
target (see Tables 3.5-7 and 3.5-8).
The values of P were evaluated based cr. RC 1.115, March 1976 (see Section y
3.5.1.3.3).
The values of P2 were evaluated for the plant layout (see Section 36 3.5.1.3.4).
Probability values for P3 were computed based on either scabbing or perforation of barriers (see Section 3.5.1.3.5).
3.5.1.3.3 Turbine Failure Probability, P References 3.5-2 and 3.5-24 discusstheeffectsofaturbineacceleratingko: de,.ign and destructive overspeed and the effects of a HP turbine rotor fracture and LP turbine disc fractures at design overspeed.
Th3 probabilities of missile generation by ductilo failure at destructive overspeed or by brittle failure at design overspeed were calculated. Inputs to these calculations were prepared from known records of Westinghouse expe-rience with the components of the turbine control and protection systems.
Reference 3.5-1 explains the method and provides the supporting data used by Westinghouse to obtain the probabilities as follows:
-6 P = 1.7 x 10 / unit / year at destructive overspeed y
-10 P = 1.6 x 10
/ unit / year at design overspeed.
y However, the total probability (P ) calculations were based o ctEn fell 36 g
P value/ = ; _/. C- : i '- J...
r.C.
1.11=== EE ^ T.1.2 p
-f/ turbine unit / year-=co4me A dehruchve overspee;\\ $1J3 rerreMe)Q
(,. D P = M x 10
.x:x::ive e =,
t>~
1 d ess y w e,9 el Q a o pe.n e 4 3 '
.Vg.Mr~p-10b= d ia; " /y- =: M i;;r ;.cupud (lE r b.
bued y W. commibeW% ertSltd deb mibnacct fmgram, wOu 3.5.1.3.4 Strike Probability, P :
2 3.5.1.3.4.1 General - The TGs are oriented iu relation to other plant structures (peninsular orientation) so that the danger of low-trajectory tur-bine missiles affecting reactor safety is minimized. Plant layout plan view and the RG 1.115 strike zones are shown on Figure 3.5-1, and a section view is shown on Figure 3.5-2.
36 i
The detailed methods of calculating strike probabilities, assumptions, and input data are presented in the remainder of this section.
3.5.1.3.4.2 Strike Probabilities - For each turbine missile ejection, three parameters are used to describe the ballistic trajectory. These three parameters are two missile ejection angles and the missile velocity. The
,6 3
first angle, designated by 4, is the vertical angle measured from the horizontal line of the '.ntersection of turbine dise; and horizontal plane passing through the turbine axis; the second angle, designated by @, is the l
angle between the missile ejection line and the turbine disc, and the missile velocity is designated by V.
When a missile ejects, 6 can be any angle within 360*, @ can be any value within predetermined f and f range, and V can g
i I
3.5-9 Amendrsent 36
ATTACHMENT 4 STP FSAR ST-HL-AE-1802 PAGE 2 of 10 be any value within a predetermined velocity range (See Tables 3.5-5 and I
3.5-6).
The probability density functions of these three random variables for
/
the situation where no barrier exists between the turbine generator and the target are defined as follows:
y (f) = (2r)~1 if OS&$2r f
.fp (f) = 0 otherwise 4
is (Y) " ( max ~ fain)
AL fmin $ I I faax f (f) = 0 otherwise is (V) = (V Y
~
max min min max is (V) = 0 otherwise These are considered to be statistically independent.
36 The strike probability is then the product of the probability density func-tiens integrated over the ranges of f, f, and V correrponding to missile strike trajectories:
+2
- (#)
Y C # 'Y )
2 2
f F
F P
- I (Y)f (I)f (V) dfdfdV 2
1 2
3 f
f (f) # V(ff) b y
y y
Where f, and # are the minimum and the ms.ximum d's for which the missile may 4
strike the target, f (f) and f (f) are the minimum and tha maximum of f at a y
given 4 for which the missile may strike the target, and V7 ($, p ) and V (d f ) are the minimum and the maximum of V at given angles f and Y for 2
which the missile may strike the target.
In the case of barricts existing between the turbine-generator and the target, the ' equation for P is modified as follows y
Y I
YC
)
2 2
2 P
- f ( )I ( )
I(V)d/d7dV 2
1 2
3 M
)
1(
}
1 1
Where f (V) is the probability density function of missile velocity following g
the perforation of the barrier.
Since the expression for P isnotreadilyintegrabicover4,f,andV,a numerical integration process is used to complete the evaluation of the strike probability Pa.
The integral is evaluated by the computer code "TUREIS" (Turbine Missiles).
)
3.5-10 Amendment 36 J
3_
ATTACHMENT 4 f
ST-HL-AE-1802 STP FSAR PAGE 3 of 10 3.5.1.3.4.3 Assumptions Used in Turbine Missile Strike Analysis -
)
1.
The target surface is the outer surface of walls or roofs.
2.
Only surfaces which are exposed are included. Surfaces which.are covered by another directly abutting safety class structure are not included.
- ~3.
Only missiles striking from outside are included.
4.
Torget gecmetrisce are sections of flat, cylindrical, or spherical cur-faces.
5.
Each turbine disc is analyzed separately. The total strike probability is the sum over all the contributions of the individual discs.
6.
All discs are analyzed at the casing center because of symmetry. In h6 calculating the strike probability cn the target, it is assumed that the missile trajectories originate at the center axis point of the turbine.
{35 7.
For blocking of missiles by the turbine pedestal, a direction line from W,rtrid: :d; of the disc above the turbine ar.is to the edge of the
-wj pedestal is assumed. m i f e -^-- :::: ~-
- 4== ^:n : lin: f: = th; c--ter ef -- r :f r lhe f. 7 = er f: = th-fr m d;: s' - diec Sec;.:rt. 5::2r:: it gics ; ;;up:: di; m' 5:ler h::1,.m.a1 L f.;e
,my sim,.e4.
. a... r s -,..
-se. 4 siciti 7;;_-__:n;ec,gfi.--*4anj
- f li u m asion un_n~^
=! "^ ~~*=: J-jQ p3_g5o !(SE, e'$ Won 3.5~.l.5
~ -~ -
7 O
Gwasfent wetVtAs. prehbiMy den.si14 SeneGn cit.se<*be In the present case, the blocking anglels --.1,aepm Delow horizontalv-V v
= [j
...,.... __ ;;;; g pl%c,
_a 17
.-_._-t e__.
._a.
A nsthe_sm_ ans le on */S.A80JE
/
77+6 MM'MUTM. f enE 15 tUD Fat nt. hta-iIure, sseles (ggp 3.5-32)it is assumed that rotor disc failure will result weedoN me me 8.
In a turbine in four segments, but it is further assumed that the exit angles of the four segments t.re separated sufficiently such that only one is a viable threat to any or.e target area.
l 9.
It is assumed that the missile velocity and angular directions of ejec-36 tion from the torbine casf.ng have constant, coni.inu'ous probability dis-tributions within the limits determined from Westinghcase data, summa-rized in Section 3.5.1.3.4.4.
- 10. Where Westinghouse specified several dif ferent-sized missiles with the 36 stae velocity from the sane disc quadrant the heaviest missile is selected.
11.
Effects of air resistance are neiglected in the bellistic flight of thc.
l36 misrile.
3.5.1.3.4.4 Turbine Missile Generation Data Values and Results - In the I
strike probability calculation, the following values tha.t describe the turbine 36 missile characteristics at the source were determined: Distribution among mibsfle sizes, directions, and valoc.ities as determined frc,m References 3.5-1, 3.5-2, and 3.5-24.
These values were used as the input data fcr the turbine 36
., )
missile program calculations and are summarized in Tables 3.5-5 and 3.5-6.
l l
l 3.5-11 Amendment 36
ATTACHMENT 4 ST-HL-AE-1802 SIP FSAR PAGE 4 of 10 No postulsted missiles will escape from the HP casing (Ref. 3.5-2).
Thus, the failare will be in one of the LP turbine casings. The postulation is made j
that one disc bursts during aach failure occurrence and that any dise which can fail has the ease probabili:y of failure as any other.
There are 12 discs per caring, three LP casings per unit, and two turbine units _in the two-unit site. These discs are of six different sizes,, each with
~
its own characteristic missile size and velocity. Each of the 72 discs is in 3
a different location along its tespective turbine axis.
l 1.
Number of Missiles per Failure The number of missiles per failure is based on data in Tables 3.5-5 and 3.5-6.
- iable 3.5-5 contains missile characteristics for shear failure of the turbine and Table 3.5-6 for shear and rotational f ailure. It 4.s assumed that all 36 discs in a LP casing have equal chance of failure and each LP turbine has the sams probability of failure.
2.
Range of Missile Directions and Velocities It is assumed that the missile velocity and angular directions of ejection from the turbine casing have uniform probability distributions within the 36 l
limits determined fzom the Westinghouse data.
a.
Angics 1)
Dise nos 1 through 5: angu?.ar limits of 25 degrees from the dise plane, and a full 360 degrees around the disc perimeter.
2)
Disc no. 6: angular limits from 0 to 25 degrees on one side of 36 the dic : plane only, the side away from the casing center and toward the adjacent coupling and a full 360 degrees around the disc perimeter, b.
Velocity - A constant distribution within lin'its of 10 percent above l
ans. below the velocity value specified by the Westinghouse data for j
each disc.
l c.
Independence of Velocities and Angles - It is assumed that the velocity and angle values for a particular missile cre each within the specified ranges, but otherwise uncorrelated statistically with each other.
3.5.1.3.5 Barrier Scabbirg er Perforating Probability P : When a tur-3 bine missile strikes a concrete barrier, the missile can either scab, perfor-t ate, or penetrate the barrier. The scabbing thickr. ass of a concrete barrier, which is defined as the barrier thickness that is just enough to prevent 36 l
peeling off of the back face of the barrier opposite to the face of impact, is l
predicted by the Chang semi-analytical formula (SAF) (Ref. 3.5-25 and 26)
O.13 0.4 S = 1.24 l
0 t0.4 3.f
}
Cep at Y l
3.5-12 Amendment 36
i ATTACHMENT 4 ST-HL-AE-1802 STP FSAR PAGE 5 of 10 where: u = 200 f t/sec or 6096 cm/sec. depending upon whether the English or i
metric unit system is used; V = missile velocity; m = missile mass; d = equiv-alent missile diameter; f' = concrete strength, and s = scabbing thickness in consistent units.
The perforation thickness of a concrete barrier, which is defined as the bar-
. -rier thickness that is just enough to allow a missile to pass through the bar-rier without exit velocity, it. predicted by the CEA-EDF perforation formula (Ref. 3.5-25 and 3.5-27) 0.5 0.75 W
V e = 0.765 d. g/.375 0
where: e = perforation thickness in inches, W = missile weight in pounds, V =
missile velocity in ft/sec, d = equivalent missile diameter in inches, and f'c
= concrete strength in psi.
calculation, the criteria of scabbing (no secondary missile genera-In the P3 tion) or perforation (secondary missile generation) is selected depending on whether secondary missile generation (of concrete particles) is allowable or 36 not.
For example, perforation criteria is chosen for the Containment building because the interior liner plate will preclude secondary concrete missiles.
q For convenience of computation, the product of P2 and Ps is calculated first, is found as the ratio of this product and P.
/
and P3 2
Amissileorientation@determinesamissileimpactareawhichinturndeter-l mines a barrier damage initiation velocity V by the equation of scabbing or d
l perforation thickness. A functional relationEhip between @ and V can be g
constructed and expressed as I
6 = F(Vg)
Note that 6 = 0 corresponds to minimum V,, and 6=0 corresponds to maximum V WhenamissilewithastrikIngvelocity, which has a normal d.
component 9, within the range of damage initiation velocity from the minimum to the maximum of Vdn, strikes a target, the conditional probability of bar-rier damage is 6 (V )
P (D/V ) = e3 n
can be colculated by considering the following Therefore, the probability P P3 2
three cases:
Case 1: maximum V.T. minimum Vdn, then PP
=0 2 3
- )
Case 2: maximum V > minimum V then, for the case in which there are no barriersbetweentEeturbine-geNEratorandthetarget:
3.5-13 Amendment 36
m i
ATTACHMENT 4 ST-HL-AE-1802 STP FSAR PAGE 6 of 10
[2 (2(@'W) 0(V,)
W 0)
U
)
2 d* didy 2 3 " f D)f N)f IY)
J' ($,W)
P#
Os 1
2 3
J
$1 yt@
U1 W O) V(Q'W) 2 2
2 f
I f
d+d(dV
+fW 2(V) i 2
J@l J
J Y
2(
)
1 in which U and U are the lower and upper limits of the intersection of these 2
1 two valocity ranges.
's In th? case of barriers existing between the turbine-generator and the target, f'(V) should be used for f (V) and the term brought inside the integrals.
3 Ccca 3: minimum V,2 maximum Vdn ' * *"
36 P Ps = P2 2
In view of the complexity of the equation for case 2, a numerical integration pr:cces is used for the probability computation.
3.5.1.3.6 Summary and conclusions: The results of this turbine missile rick cualysis demonstrated that the arrangement of STP is acceptable against tha p:stulated turbine missiles that may be generated under a design or a d:ctructive overspeed condition.
Four cualyses have been performed to determine the worst total probability P4:
1.
missiles generated from the shear failure of turbine generator Unit No. 1 2.
missiles generated from the shear failure of turbine generator Unit No. 2 3.
missiles generated from the shear and rotational failure of turbine gen-erator Unit No. 1 4.
missiles generated from the shear and rotational failure of turbine gen-erator Unit No. 2.
Th3 results for analyses 1 and 2 are shown in Table 3.5-7 and the results for analyses 3a9d 4 are shown in Table 3.5-8.
ThewosttotalprobabilityJ4is
- which is obtained by multiplying
_f(P)byeve999?'x10 f91999]9x10 (P P,) and is less than the allowable limit of 10.lhhereforeturbine) 2
-6 f,57Q cissiles need not be considered as a design basis.
)6
- o.9283 W 3.5.1.4 Missiles Generated by Natural Phenomena. Flooding, hurricanes, ffcnd tornadoes are the only three types of natural phenomena which could gen-( crcto missiles at STP.
Da b* 'N' N'O Af*f"U 1he +vtbErst 5off rke s5lli7 efonet en endoty me n ahe<. ne mspes>, w
/
l h,n a.ci, ar sc wa,, sc w,c anue,a ropa sc ss,aen nc W'Nhi N
)
Amendment 38 35-
.--...--...n
ATTACHMENT 4 ST-HL-AE-1802 STP FSAR PAGE 7 of 10 REFERENCES (Continued)
Section 3.5:
~
3.5-23 Manual, S. A., "Impactive Dynamic Analysis," ASCE National Structural Engineering Meeting, Baltimore, Maryland, (April 19-23, 1971).
3.5-24 Westinghouse Electric Corporation, Steam Turbine Information, Section 17 CT-23999. August 1978, Revision 1.
3.5-25 Wolde-Tinsae, A.M., et al., "NRC Review of Impact Damage",
Seminar on Turbine Missile Effects in Nuclear Power Plants, published by EPR1, October 1982.
3.5-26 Chang, Wen S., " Impact 'of Solid Missiles on Concrete Bar-riera " Journal of the Structural Division, ASCE, Vol.
107, No. ST2, Proc. Paper 16031, February 1981.
3.5-27 Romander, C.M., " Scale Model Tests of Turbine Missile Con-tainment by Reinforced Concrete," Seminar on Turbine Missile Effects in Nuclear Power Plants, published by EPRI, October 1982.
36 3.5-28 Rotz, J.V., "Results of Missile Impact Tests on Reinforced Concrete Panels," Vol. lA, pp 720-738, Second Specialty i
Confererce on Structural Design of Nuclear Power Plant Facilities, New Orleans, LA, December 1975.
3.5-29 Cwaltney, R.C., " Missile Generation and Protection on Light-Water-Cooled Power Reactor Plants," ORNL NSIC-72. Oak Ridge National Laboratory, Oak Ridge, TN, for the USAEC, September 1968.
3.5-30 Price, Arnold E., Houston Air Traffic Control Center, Federal l
Aviation Administration to Rick Donahue, Bechtel, j
February 2, 1983.
3.5-31 Federal Aviation Administration. FAA Statistical Handbook of Aviation, DOT /FAA-SNA-1981, 1981.
Iwisdale;4 4 >o m;ak msec.b Amym I
M 'Ifgg s.6-32 w,ae ou Toesine ghiale Ee
'M ikee Pbmis, poblahed %
- l
. )
3.5-23 Amendment 36
mU v
v 1
TABLE 3.5-7 t
PROSABILITIES Ps AND F, OF TARCETS DUE TO UN11S 1 AND 2 TURBINE MISSILES (SHEAR Ft.ILURE)
TURSINE CENERATOR TARCET Unit i UNIT 2 23(10N 2 (10' )
2 3 (10' )
F2 (10~ )
F No.
HAME*
F F
3 4
1 RCB 1 1.4303
.0118
.C169 2
RCB 2
.3450 9.0 0.0 9t74
'2 f/p9
.7sfy
.3273
,+47y vW54./
3 DCB 1 w'MT+ -
-:16t9-rP99t>-
rttetr-4 DCB 2 wS406 -
M &aa-4 m 4 M 6--
.1M:
-,0603 i.sssa
.m i.om
.mv un
..isa i
FHB 2 36 u
'n u.
7 MEAR 1
.2155
.1206
.0260 Y
i 1
g 8
MEAR 2
.0190 0
0 g
9 AFW TAME 1
.2018
.8332
.16El 10 AFW TANK 2 11 Ivc 1
.4072
.8178
.3330 12 Ivc 2
.'0377
.1709
.0064 7M>
NYM 13 ECW mI>
1NTexE
- 190 0 814Y
/SS/
wTQ y
b ST2UCTURE
-v4956-1r6089-et999-om%
g v
'L5 a
-w S
TOTAL
- 1. MM r$949=
4,4609-O o Ai 2.2823
/A'/72
- 5. 3G//
/-
7f=
u*
TME P (F aP xF) ree99 x 10~
ve994-x 10"I g
2 3
o.9285 0.90YC Note: Blanks are for those targets either located outside the low trajectory missile strike zone or shaded by other targets.
- RCB 1 designates Reactor Containment Building Unit 1 IVC 1 designates Isolation Value Cubicle Unit 1 etc.
1
i-t s
U L'
4 TABLE 3.5-8 PROSABILTTIES Ps AND P. OF TARCETS DOE TO UNITS 1 AND 2 TURBINE MISSILES (SNEAR AND ROTATION FAILURE) l l
tuRatNE cENERATOR TARCET Unit I tfMIT 2 F '3 (10-3)
F 2 (10~ )
23(10N No.
NAME F
2 2 (10' )
F F
F 3
3 1
RC5 1 1.5660 0
0 2
RCB 2
.3779 0
0 e625
.D8A 5)(Y 3
MB 1 9544e-
+
v 0
0 0
4 DGB 2
.4444
.NG
,4006 m
-e-
--e-l.3967 455.2 9EGl
.523Y 4 82
. f2W 3
w 6
NB2 in 7
NEAR 1
.2534
.0073
.0019 36 3
8 NEAR 2
.0234 0
0 E
9 AFW TANK 1
.2066
.7869
.1622 10 AFW TANK 2 11 IVC 1
.4502
.8207
.3695 nm3
>$Sq 12 IVC 2
.0457
.1438
.0066 3
ra WB 3-l
[$ Axe
,;tcQS 70W
.Iif34 oMM STRUCTURE deft-M T99f9-b$
w co 08" al TOTAL 4 3440-e4069-
-9,46pe-ar6 M S-Q.341O
/aWQ 3.202(
/,iffG e
w TOTAL F (F xF xF) r9e4F x 10'
,6MS x 10~
1 2
3 d.8645 c.'l l18 Notes Blanks are for those targets either located outside the low trajectory missile strike sone or shaded by other targets.
I
ATTACHMENT 4 STP FSAR ST-HL-AE-1802 PAGE 10 of 10 At approximately 36-to 39-month intervals, at least one throttle valve, one governor valve, one reheat stop valve, and one interceptor valve shall be din-mantled. Visuni and surface examinations shall be conducted on valve stems, seate, and discs.
In the event that excessive corrosion or flaws are found in a valve, all other turbine valves of that type will be dismantled and exam-ined. Valve bushings shall be inspected and cleaned, and bore diameters shall 39 be checked for proper clearance.
All throttle, governor, reheat stop, and interceptor valves will be function-ally tested at least once a week to ensure that each valve is capable of moving smoothly and freely to a fully closed position.
These tests shall be made by direct visual observation of the valves.
The functional testing of throttle, reheat and interceptor valves may be carried out with the turbine at 39 any load. The governor valves may be functionally tested at any load up to 92 percent of rated load.
J 10.2.5 Evaluation The TG and its auxiliary systems are Non-Nuclear Safety (NNS) Class with the exception as noted in Section 10.2.2.8.
Under normal operating conditions, 39 there are no significant radioactive contaminants present in the secondary system.
In the event of an SG tube leak radioactivity can be present in the secondary system.
An estimate of the activity level in the secondary system due to SG tube leak is given in Section 11.1.
During normal operating conditions, no radiation shielding or controlled access is required for the 39 Turbine Generator system.
The safety evaluation with respect to radioactivity in the secondary system is discussed in Section 10.4.1.3.
The most severe operational transients caused by operation of TG or distri-bution system protection equipment are analyzed in Chapter 15.
Any number of component or system operational abnormalities can be postulated to produce a TG load transient. However, since the effects of such abnormal-ities can be no worse than a turbine or generator trip, these occurrences are not analyzed. Operating conditions which will result in a turbine trip are discussed in Sections 10.2.2.8 and 10.2.2.9.
The effects of a turbine trip on the reactor are discussed in Section 15.2.3.
10.2-12 Amendment 39 w