ML20147J282
| ML20147J282 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 03/10/1997 |
| From: | Branam T, Katers P WISCONSIN ELECTRIC POWER CO. |
| To: | |
| Shared Package | |
| ML20147J279 | List: |
| References | |
| CR-96-385, CR-96-385-R02, CR-96-385-R2, NUDOCS 9704250034 | |
| Download: ML20147J282 (13) | |
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OPERABILITY DETERMINATION UPDATE (Rev. 2)
CR 96-385 ,
POTENTIAL FAILURE OF REDUNDANT SAFETY RELATED CIRCUlTS, WITHIN THE MAIN CONTROL BOARD
- 1. Degraded or potentially non-conforming equipment:
There are instances where Train A and Train B circuits (wires) or circuits from more than one instrument channel run in the same wireways or risers within main control boards, thus making possible a potential failure of redundant safety-related (SR) functions due to a single failure.
- 11. Safety Fw. tion (s) performed:
The pagose of physical separation of train A and train B circuits or circuits of more than one instrument channel is to maintain independence of safety-related circuits. Give such separation, no credible potential source of damage (other than a fire) would result in damage to redundant Class IE circuits beyond an acceptable level. In the event of a fault within one train or channel circuit the integrity of the other train or channel circuits would not be damaged to the point of not b eing capable of performing their safety function. Thus the functionality of one train of safety-related Equipment and the minimum required number ofinstmment channels would be maintained at all times.
!!!. Circumstances of potential non-conformance, including possible failure mechanisms:-
A fault on an inadequately protected circuit in the main control board could damage that circuit and any adjacent safety-related circuits, potentially affecting the functionality of both trains or multiple channels of redundant safety- related equipment. This would occur if circuits required for redundant components from both A and B trains or multiple instrument channels are run together in the same wireway in the main control boards.
Based on this, there is a ;iotential for single failure ofinternal control board wiring to disable selected safety related functions on redundant trains or channels.
Note: The ability to achieve and maintain plant shutdown in the event of a control room .' ire as required by 10CFR50 Appendix R is not affected by the above described situation.
IV. Requirement established for the equipment, and why it may not be met:
The main control boards contain the control circuitry for proper manipulation of safety-related and Non-
. safety related equipmem ud displays of safety-related and non-safety related equipment status.
Westinghouse Engineerik Change Notice, ECN-WEP-70083, states that," wires requiring separation shall use separate routing of wireways between devices. In no case shall wiring requiring separation be bundled together." The draft of the PBNP Design Basis Document (DBD) position paper on electrical separation indicates that the design basis for PBNP includes requirements for physical separation of electrical wiring.
As discussed in this determination, review ofinternal design documentation clearly indicates Wisconsin Electric's intent to maintain separation. A review of design and licensing basis requirements in the Final Safety Analysis Report Chapters 7, " Instrumentation and Control." and Chapter 8, "Fiectrical Systems,"
was performed. The following statements conceming separation of redundant safety related circuits were identified.
9704250034 970416 'I PDR ADOCK 05000266 S PDR ,
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i CR 96-395 2 3/10/97 ,
1 Section 8.2.2, " Station Distribution," evaluates layout and load distribution and discusses the routing of '
l control, instrumentation and power cables. The following statement is made: " Wire and cables related to l l engineered safeguard and reactor protective systems are routed and installed to maintain the integrity of )
their respective redundant channels and protect them from physical damage. Later dixassions in Chapter j 8 discuss the verification of physical separation of emergency power cables. The wirig that is the subject j of this operability determination is not emergency power cable. Therefore, the means of providing l integrity to redundant channels within the control board is not limited to physical separation. Other means !
can be employed to protect the main control board circuits of redundant trains and channels. .
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Chapter 7 was reviewed for discussions of separation. Analog instrumentation and associated wiring l requires separation from the process sensor to the instrumentation racks. This does not require the wiring in question to be physically separated. j
.Also included in Section 7.5.2 of the FSAR is the following statement,"The same channel isolation and separation criteria as described for the reactor protection circuits are applied to the engineered safety features actuation circuits." l 1
The following question and answer were included in our response to AEC questions concerning the FFDSAR dated 1/16DO.
" Ouestion 7.6 l
Submit your cable installation design criteria for preserving the independence of redundant reactor protection system and engineered safety feature circuits (instrumentation, control, and power). For the purpose of cable installation, the protection system's circuits should be interpreted in their broadest sense to include sensors, instrument cables, control cables, power cables, (both a.c. and d.c.), and the actuated devices (e.g., breakers, valves, and pumps): -
- a. Cable separation should be considered in tenns of space and/or physical barrier between redundant cables. Please address (1) the separation of power cables from those used for control and instrumentation, (2) the intennixing of control and instrument cables within a tray, conduit , or ladder, (3) the intermixing within a tray, conduit, or ladder, of cables for different protection channels, and (4) the intermixing of non-vital cabling with protection system cabling."
(Parts b, c, and d of the question not provide here since they are not relevant to this issue.}
" Answer A. (3) Separation is maintained such that redundant protection channels are not intermixed within the same wireway."
[ Remaining portions of the answer to question part (a) and the repossess to parts b, c, and d are not i
provided here since they are not relevant to this issue.]
1 in conclusion, separation of wiring associated with redundant safety related functions is required within the
! main control board.
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CR 96-395 3 3/10/97 V. How and when the potentially non-conforming equipment was first discovered:
While performing evaluations for the walkdowns to resolve LER 301/91-001-01 Action #23, it was determined from the DBD position paper that the design basis for Point Beach Nuclear Plant includes l
requirements for separation of redundant wiring in the Main Control Board. This was noted during an I update to the LER on 3/4/96. I A detailed review of all safety related (SR) wire routing in the main control board was initiated on 6/17/96 ,
to identify routing of wires which support redundant functions in the same raceway. The approach taken I was to first identify the raceways that would have the highest potential for containing wires which support redundant safety-related functions. This was done based on knowledge of what was identified during as- l builting of the Main Control Boards, knowledge of basic control board routing, panel layout and 1 engineeringjudgment. Of 68 raceways to review 4 were picked for the initial review. The approach was i to first determine if the raceway included wires which support safety-related functions. If wires which ,
support redundant safety-related functions were identified, the existence of adequate fault protection for all j wiring in the rr.ceway as described later in this evaluation would be verified. This process assured that conditions were within those defined as necessary for operability as define in this evaluation. Any design deviations would require a specific operability evaluation and appropriate compensatory and corrective actions.
During the review process on 8/14/96 it was discoverea that Lo-Lo : team generator automatic start circuitry for both P38A and P38B (motor-driven auxiliary fe edwater pumps) were routed through a ;
common raceway. Fault protection for these wires was determined to be adequate, however, a wire associated with I P-29 (Unit I turbine-driven auxiliary feedwater pump) mini-recire valve and trip indication was determined to not be adequately protected. Immediate action was to enter the applicable Technical Specification (TS) Limiting Condition For Operation (LCO) for P38A and P38B out of service.
The LCO was exited when the supply breaker to the inadequately protected circuit was opened. IP-29 would remain out of service until adequate fault protection was installed. Modifications were subsequently completed to resolve this specific problem.
On 8/15/96 it was discovered that cabling in the main control board associated with IMS-2019 and 1MS-2020,1 AF-4000 and 1 AF-4001 (turbine-driven auxiliary feedwater pump supply and discharge valves) also did not have adequate fault protection, Cabling for IMS-2019 and I AF-4001 are routed through the same riser as the automatic start circuitry for P38A and P38B. Immediate action was to enter the applicable TS LCO for P38A and P38B out of service. The LCO was exited when the supply breakers to the inadequately protected circuits were opened. Modifications were subsequently completed to resolve this specific problem.
Based on these findings, the original operability determination (Revision 0)for this was questioned and the MSS (Manager's Supervisory Staff) was convened on the morning of 8/16/96 to review:
- The origint.1 operability evaluation
- The conditions being identified
- The corrective actions
- And to make an operability call on the main control board
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CR 96-395 4 3/10/97 i
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Summary of MSS Meeting -
! The approach being taken for evaluation / resolution of the redundant function potential lack of adequate )
j wire separation issue:
- 1. Initially identified 4 of 68 wireways that had the highest potential for the problem to exist. :
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- 2. Initially focused resources on evaluation of the wireways identified in 1. above.
- a. During the initial wireway evaluations low voltage de control circuitry associated with de valves was i . the only circuitry in which fault protection problems were identified. ,
- 3. A specific operability call for the equipment affected was made and prompt short term corrective j actions have been taken for the identified instances ofinadequately protected low voltage de control circuitry.
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) ai Unit I turbine-driven auxiliary feedwater pump applicable circuitry was deenergized to eliminate the ;
- potential fault ,ource and the pump declared out of service. ]'
- 4. Immediate follow-up actions are currently in progress to install lower rated breakers and fuses, where i
- applicable, to provice adequate protection to prevent an ide .tified fault firom adversely affecting the wiring.
- a. Installation of adequate wire protection associated with the Unit 1 turbine-driven auxiliary feedwater !'
- pump is cunently in progress and is expected to be completed today (8/16/96). Upon completion of this modification, the pump will be properly retumed to service and the LCO exited. ;
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- j. b. Installation of adequate wire protection on the Unit 2 turbine-driven auxiliary feedwater pump will i
- commence upon return to service of the Unit I turbine-driven feedwater pump and will be completed
[i by 8/17/96. ,
i 5. A review of all similar de valve applications that could impact the wireways under review was )
!- completed with no other concems identified. .
. 6. The focus of the review and evaluation process is being shifted to evaluate all de cabling within the main control board for adequate fault protection.- This evaluation will be completed by 8/23/96. A similar re+v of all ac wiring will be completed by 9/30/96.( Note: both of these reviews were subsequenti, nmpleted as described below.) l 1
- 7. 'Ihe completion of the full evaluation of the initial 4 wireways will be completed by 8/30/96 and the evaluation of the balance of the wireways will be completed by 12/31/96. (Note: It was subsequently ;
determined that this review was not required. It was instead assumed that each of these raceways did contain wires which supported redundant functions) j
- 8. Long term correction of wire separation deviations will be implemented during the next respective refueling outage. (Note
- A limited number of circuits were rerouted during the Fall 96 Unit 2 outage to attain adequate separation. Remaining circuits will be rerouted during future outages. A schedule for such work is presently being developed.)
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CR 96-395 5 3/10/97
. The staficoncluded in this meeting'that the main control board remains operable based on the following:
A. Wire separation within the main control board is a design basis but not a licensing basis commitment.
Thus, for operability considerations demonstrating adequate protection of redundant safety function wires from the potential of being affected by a common mode failure in place of physical wire j separation, is acceptable. ( Note: It has subsequently been determined by the NRC that lack of winng i separation within the main control board is contrary to the PBNP licensing basis. This does not however l change the basis for considering the main control board operable. ) l B. The original operability basis in Section VI remains valid with the exception of the fact that a specific family of outliers have been identified. Continued operability while the review progresses with this 4 known fact is consideredjustified because of the following:
- 1. Specific deviations are addressed when identified including an operability determination, immediate compensatory action and follow-up deviation resolution.
< 2. A focused review to evaluate all de cabling within the main control board for adequate fault !
3 protection is being performed and will be completed by 8/23/96. )
1 l j 3. All known cases are in the process of being corrected or scheduled to be corrected within the i
next day. l l 4 Many conservarisms were/are built into the evaluation of wire protection.
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- a. Used a short circuit temperature rating of 250*C when the actual short circuit temperature rating for damage to the wire insulation is 350*C
- b. Only considered insulation breakdown in the faulted wire. Did not consider the \
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. insulation of any potentially affected wire's ability to protect that wire.
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- c. Assumed that the faulted wire and the potentially affected wire were bundled and in direct contact with each other. l
- Low probability by engineeringjudgment due to the large number of cables in each wireway
- Low probability of being " bundled"(tie wrapped tightly together) because tie wraps were severed to eliminate bundling during the main control board wiring evaluations j for the design basis document development project. I
, d. Wire heatup dampening due to increase in wire resistance was not included. {
C. Short term corrections are being implemented to maintain operability when deviations are identified. )
Long term correction to meet design basis wire separation in the main control board will be I implemented during the next respective unit refueling outage.
Based on the above analysis, summary of findings and actions to date, summary of ongoing evaluations and corrective actions, and assurance of safety summary, the main control board was considered to be operable.
The operability determination of the main control boards by the MSS at this meeting was based on the understanding that the review process included all safety related wiring in the main control boards.
However detailed routing information was not available for panel CO2.
CR 96-395 6 3/10/97
- A review of DC control circuits for diesel generators G-01 and G-02 revealed that circuits entering the '
main control may have inadequate protection. These circuits consist of #14 AWG SIS wiring in CO2 and i are protected by 30A or 40A breakers with no fuses. Inspection of breaker time-current characteristic curves and the conductor thermal damage curve indicates that conductor damage could occur prior to
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breaker operation fot some short circuit faults. Since the possibility exists that the underprotected A Train G01 circuits are not physically separated from non-EDG B train ciret:its within main control board C02, a single fault in a G-01 control circuit has the possibility of affecting A train and non-EDG B train circuits m l C02. l Although the possibility exists for A train and non-EDG B train circuits to be affected by a single fault, l safety related control circuits in CO2 are considered operable. Safety related wiring in panel CO2 primarily l consists of control circuits for diesel generators G-01, G-02, G-03, G-04 and safety related 4160V and )
i 480V switchgear. Recent modifications involved rewiring main control board internal wiring for diesel generators G-02, G-03 and G-04. Separation of main control board wiring was part of the design process ;
for these modifications and this wiring is expected not to contribute to the risk of faulting irdundant safety ;
related circuits. j l
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VI. Basis for declaring affected equipment operable I 1
ne following analysis demonstrates why redundant safety-related circuits would not be degraded by a single source of damage, and, why in the event of a failure within one train or channel the circuits of the other train or channel routed in the same wireway or riser within control room panels, would not bc l degraded below an acceptable level. Thus the functionality of one train or the required minimum number of channels of redundant equipment would be maintained at all times. He analysis considers the effect of ,
circuit isolation by protective devices, maximum temperature of faulted conductors, wire insulation and the l potential for hazards in the specific area involved.
ANALYSIS
- 1. Wire Terminations -
For all cases where potential failures of safety related functions are identified, all train or channel wires are terminated on a terminal block separate from those of redundant train or channel wire Terminations.
1 Wire Insulation The wires are rated 600 volts,90*C, with the short circuit temperature rating of 250*C, utilize heat resistant rubber insulation, and are applied in a control circuit with a system voltage of 125 V de or 120 V ac, thus providing a conservative design margin between rated and applied voltage.
L Potential for Mechanical Damage of Wiring within the Main Control Board All of the wiring within the Main Control Board is located in a non-hazard area having the following characteristics:
- a. The area does not contain high energy equipment such as switchgear transformers, rotating equipment, or potential sources of missiles or pipe failure hazards.
- b. Most circuits in the ares are limited to control and instrumer.t functions.
I CR 96-395 7 3/10/97 1.
'c. With the exception of a few isolated cases of power feed cables sized #6 AWG, there are no power J
circuit cables larger than #8 AWG in this area, and all cables providing control power feed are protected meeting NEC requirements.
- d. Administrative control of operations and maintenance activities exist in this area that limit introduction of potential hazards into the area.
Thus, there exists no potential source for causing mechanical damage to a wiring within the main control l board which would result in physically damage to redundant trains or channels.
- 4. Effect of Short Circuits A revi,ew of all AC and DC circuits routed through the Main Control Board has been completed. This review concluded that no single failure would result in the loss of redundant safety-related wiring . I The following demonstrates why redundant safety-related circuits inside the Main Control Board will not ,
be degraded by a conductor fault. In every case in which redundant safety related circuits are routed within l the same wireway, all conductors within the wireway have fault protection that is adequate to prevent I damage to adjacent conductors. Therefore the potential does not exist for a faulted conductor to I simultaneously damage redundant circuits, thus ensuring the functionality of one train or three channels of equipment at all times.
The following conservative assumptions were made in predicting te maximum wire insulation i temperature: l
- a. All potentil affected safety-related wiring is in physical contact with the faulted conductor,
- b. All energy due to fault induced Joule resistive heating is contained within the faulted conductor.
No credit is taken for energy dissipation to other adjacent cortductors, or to surrounding air or wireway.
- c. Insulation temperature of the faulted conductor will increase to a value equal to the peak conductor temperature. No credit is taken for the thermal mass of the insulation of the faulted conductor or adjacent conductors.
- d. No decrease in the fault current due to the increase in conductor temperature occurs.
- e. Most conductors will not experience a temperature greater than the short circuit rating of 250 degrees C. At this temperature, the insulation on the faulted conductor will not be degraded.
Conductor temperatures were predicted in accordance with Attachment #1.
Tests were conducted to verify the survivability of the insulation used on wiring in the Main Control Board. The purpose of these tests was to support the above conclusions that if two conductors were in physical contact, and if one of the conductors was faulted , the second conductor would not be damaged as the peak temperature the second conductor would experience would be less than its rated temperature. An implicit assumption of this conclusion is that there is no gross mechanical failure mechanism associated with the faulted conductor that would introduce nonlinear heat transfer trcnsients.
These tests indicate that the insulation will not experience gror; mechanical failure or ignition for a period of at least one minute when exposed to a temperature of 410 oegrees C. The tests also demonstrate that the faulted wire will not fail in a fashion that would cause an adjacent wire to be damaged.
s CR 96-395 8 3/10/97 .
A. DC Control Circuits A review was performed of all 125 VDC circuits to determine if a single faulted cable could damage control board wiring required for the operation of redundant safety-related equipment. Circuits were determined to be acceptable if they satisfied at least one of the following criteria:
- 1. The circuit does not ir.clude any wires inside the Main Control Board
- 2. The maximum calculated conductor temperature reached during short circuit conditions of any wires in the main control board was determined to be less than the wire short circuit temperature rating of 250 degrees C. This was done by companng the rise in conductor temperature at th maximum available fault current to the time current characteristics of the
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protective device for the conductor. This criterion is bounded by criteria #3. It is included as a separate category to illusrate the fact that the majority of conductors have fault protection I that is adequate to ensure that peak conductor temperatures will not exceed this more conservative c6tehon.
- 3. The maximum calculated conductor temperature reached during short circuit conditions of any wires in the main control board was detenninc . e be less than the insulation Ignition temperature, thus ensuring that insufficient energy is a vailable for ignition of the conductor I insulation his was done by comparing the rise in conductor temperature at the maximum j available fault current to the time current characteristics of the protective device for the l conductor. j l
his analysis demonstrates the survivability of conductors adjacent to a faulted conductor. His analysis demonstrates that a wire in the Main Control Board adjacent to and in contact with a faulted conductor will not be degraded below an acceptable level. All wires adjacent to the faulted conductor will remain fully functional if the faulted conductor temperature reaches the maximum conductor temperature predicted for a worst case fault. Therefore no fault on a DC system conductor in the Main Control Panel !
will result in the loss of wires required for the perfot'. hance of redundant safety functions. His analysis is !
conservative due to the fact that it assumes that a worst case fault occurs and redundant conductors are in !
direct contact with the faulted conductor. .
A total of 281 DC circuits were analyzed. The results of this analysis is summarized below:
73 Circuits: No MCB Wiring: The circuit does not contain any wiring which enters the Main Control Board 61 Circuits: - Spare Circuits 88 Circuits: Fused < 250 degrees C: The circuit has adequate fuse protection to ensure that faulted wires in the main control board will not attain a temperature greater than its rated temperatug (250 degrees C.)
29 Circuits Breaker < 250 degrees C: The circuit has adequate breaker protection to ensure that faulted wires in the main control board will not attain a temperature greater than its rated temperature. (250 degrees C.)
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, . ,. CR 96 395 ' 9 A
20 Circuits . Separated: It has been determined by physical i inspection that wiring associated with this ;
circuit is adequately separated from that of redundant safety-related circuits.
' 10 Circuits Breaker < Damage Temperature: The circuit has :
adequate protection to ensure that faulted wires in the main control board will not attain a i temperature that could damage a adjacent j conductor, j The above reflects the effect of several modiCcations to replace circuit breakers or add in line fuses. I l
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B. 120 VAC Circuits A review was completed of all 120 VAC circuits. This review determined if there is a potential t
for damaging redundant safety related wiring in the main control boad due to a fault on a 120 VAC circuit.
The review included all circuits listed in Master Data Book Section 3.2.11. A total of 888 breaker positions were analyzed, in addition, the control circuits for 25 motor control centers were reviewed for .
adequate overcurrent protection. For all of the MCC control circuits reviewed ,15 amp or smaller fuse protection was provide for the control circuits. Circuits were determined to be acceptable if they satisfied l at least one of the followmg criteria: l l
- 1. The' circuit does not include any wires inside the Main Control Board
- 2. The circuit is protected per the requirements of the National Electrical Code. Table 310-121 l of the 1965 NEC states that insulated copper, #14 SIS wire has an ampacity of 25 amperes.
There is a 50% departing factor for installations where 42 or more conductors are installed in j the same raceway (exception #8 from the notes to table 310-12). This would create a final ;
ampacity of 12.5 amperes. Exception #10 from the notes to table 310-12 states,"Where the ,
standard ratings and settings of overcurrent devices do not correspond with the ratings and l settings allowed for conductors, the next higher setting may be used." This allows installation !
of a 15 ampere overcurrent protective device to protect #14 SIS wire. Therefore, a circuit j protected by a 15 ampere or smaller fuse or breaker is deemed acceptable. ;
- 3. A number of circuits have wires which only enter the IC-20 and 2C-20 control boards. l Adegate separation of redundant circuits in these boards has been maintained during design ;
and installation of these panels. .
The results of this analysis is summarized below:
174 Circuits: . No MCB Wiring: The circuit does not contain ;
any wiring which enters the Main Control Board -
, 470 Circuits: Spare Circuits ,
30 Circuits: Circuit is protected by a fuse rated 15 amoeres or less a
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i CR 96-395 10 3/10/97 i -
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- 204 Circuits Circuit is protected by a circuit breaker rated 15 * -
amperes or less. (Note: 14 breakers were I
, replaced per modifications 96 069 and 96-070 j; to replace larger breakers.) l i )
10 Circuits Circuits have wires which only enter the IC-20 j and 2C-20 panels. j 1
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j Vll. Additional actions necessary to demonstrate operability: )
The information included in section VI above adequately demonstrates that the potential for failure of. wiring in the Main Control Boards which would affect redundant safety-related functions is i
] essentially non-existent. Additional actions are not required to demonstrate operability of the control boards and the wiring therein. The above, however, does not demonstrate confonnance to the licensing or l
- design basis for separation in the main control boards Rerouting of wiring in the main control boards to ;
,' ' obtain such separation needs to be completed. !
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l Prepared By: P, T. Leu s osie: rad 99 Reviewed By: 78, Or o ,4o m Date: ~8//C[9 7 -
Reviewed By: \ ~
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' Active SRO Approved By: /Da 7 ty and CalISuperintendent V e
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2 SHORT CIRCUIT CURRENT VALUES FOR - i l
AWG SIZE CONDUCTORS (COPPER)
BASED ON MAX 1MrJM CONDUCTOR TD4PE.h7UFE OF 250* C
's ne attached tables and curvus show the allowable short cir:uit currents vs.
a condue:mr :smperzture of 25C'. C from a star 5ng point of 20*, 60', or 90' C.
The assumpt!cna used in the :alculations ars: *
- 1) The current is =enstant with f:me.
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- 2) The conductor resistanca inenrases as the temperattra Increases.
- 3) The spee!!!c heat of the ::nductor is constant over the istnperatura range of interest -
- 4) The process is adiabatic . that is; the pr::sss is se rapid that no heat is dissipated to the surround!ng envir:nmant (insulation or air). The risults are thersfors valid for single or mu!*J* conduct;r Cables wY.h any insulation conflguration. j R. J. Gehm 9/T/94 9
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FOR #14 AWG CONDUCTCMS j
5/ CIRCUIT ALLOWAELE S/C CURRENT FOR INTTIAL cCND, TyypERATURE OF:
DURATION 20 DEG C 50 DEG C 50DEGC SECONCS.
0.0083(1) 4115 356U 3172 0.0090 3959 3425 3052 0.0100 3755 3248 2355 0.0167 (2) 290s 2517 2242 '
O.0200 . 2555 2296 2047 0.0300 2155 1876 i$72 ;
0.0333 (3) 2053 1751 1557 0.0400 1875 1525 !
1448' l 0.0500 1650 1453 1295 0.0600..
- 1533 1327 1182 0.0700 1420 1228 1054 0.0800 1323 1149 1024 l
,0.0900 1252. - 1083 565 ..
0.1000 1i55 ;025 !
, 916 l 0.1600 935 !
812 724l 0.2000- 540 ,2/ 647 0.3000 655 5E3 529 0.4000 554 514 458 0.5000 531 450 40s j 0.5000 445 420 374 i 0.7000 445 386 348 0.5000 420 353 ~
324 0.9000 355 343 305 .l 1.0000 375 325 250 -
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