ML19329D711
| ML19329D711 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 02/11/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19329D710 | List: |
| References | |
| NUDOCS 8003160327 | |
| Download: ML19329D711 (26) | |
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ENCLOSURE l
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I INTERIM SAFETY EVALUATION REPORT ON EFFECTS OF FUEL ROD B3 WING ON THERMAL MARGIN CALCULATIONS FOR LIGHT WATER REACTORS j
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CONTENTS 1.0 Introduction 2.0 DNBR Reduction Due to Rod Bow 3.0 Application To Plants In The Ccnstruction Penmit And Operating License Review Stage 4.0 Application To Operating Reactors 5.0 References O
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1.5 Introduction Data have recently been presantec to tne staf f wnicn sr.ow that previously developed methods for iccounting for the effect of fuel rod bowing on departure from nscleate boiling in a pressurized water reactor (PWR) may not contain acequate thermal margin when unheated rods are present (such as instrument tubes).
Further experimental verification of these cata is in progress. However an interim measure is required pending a final decision on the validity of these new data.
The staff has evaluated the impact of these data on the performance of all operating pressurized water reactors, tiodels for treating the effects of fuel rod bowing on thermal-hydraulic performance have been derived for all operating PWRs.
These models are based on the propensity of the individual fuel designs tc bow and on the thermal analysis methods used to predict the coolant conditions for both normal operation and anticipated transients. As a result of these evaluations the staff has concluded that in some cases sufficient thermal margin does not now exist.
In these cases, additional thermal margin will be required to assure, with hiph confidence, that departure from nucleste boiling (DNB) does not occur during anticipated transients. This report discusses how these conclusions were reached and identifies the amount of additional margin required.
The models and the requirec DNBR reductions whicn result from these models are meant to be only an interim measure until more data are available. Because the data base is rather sparse, an attempt was made to treat this problem in a conservative way.
The required DNBR reductions will be revised as more data become available.
The staff review of the amount and consequences of fuel rod bowing in a boiling water reactor is now underway. At present no.
conclusions have been reached. When this review reaches a stage where either an interim or final conclusion can be reached, the results of this review will be published in a separate safety evaluation report.
It should be noted that throughout the remainder of this
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report, all discussion and conclusions apply only to pressurized water reactors.
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2.0 DNBR Reduction Due To Rod Bow
2.1 Background
in 1973 Westinghouse Electric presented to the staff the results of experiments in which a 4x4 bundle of electrically heated fuel rods was tested to determine the effect of fuel rod Dowing to contact on the thermal margin (DNBR reduction) (Reference 1). The tests were, done at conditions representative of PhR coolant conditions, The results of these experiments showed tn6t, for the highest power density at the highest coolant pressure expected in a Westingnouse reactor,the DN3R reduction due to neated rods oowed to contact was approximately 8%.
Fuel bundle coolant mixing and heat transfer computer programs such as COBRA IIIC and THINC-IV were able to predict the results of these expariments.
Because tne end point could be predicted, i.e., the DNBR reduction at contact,there was confidence that the DNBR reduction due to partial bow, that is, bow to less than contact could also be correctly predicted.
On August 9, 1976 Westinghouse met with the staff to discuss e
further experiments with the same configuration of fuel bundle (4x4) using electrically heated rcds. However, for this set of experiments one of the center 4 fuel rods was replaced by an unheated tute df the same size as a Westinghouse thimble tube.
This new test configuration was tested over the same range of power, flow and pressure as the earlier tests. However, with the unheated, larger diameter rod the reduction in DNBR was much larger-than in the earlier (1973) tests.
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The data consisted of points corresponding to no intentional.
bowing (that is, a certain amount of bowing due to tolerances cannot be prevented) and to contact. No data were taken at partial clearance reductions between rods.
On August 19, 1976 CE presented rasults of similar experiments to the staff. These tests were performed using a 21 rod bundle of '
electrically heated rods and an unheated guide tube.
Results were presented for not only the case of full contact, but also the case of partial bowing.
The staff attempted to calculate the Westingnouse resuits with the COBRA IIIC computer code but could not obtain agreement with the new data. Westinghouse was also unable to obtain agreement between their experimental results and the THINCIV computer code.
Both sets of data (Westinghouse and CE) showed similar effects due to variations in coolant conditions.
For both cases, the DNBR reduction became greater as the coolant pressure and the rod power increased.
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Because both sets of data showe. hat plant thermal margins might be less than those intendec, tne staff derived an interim model*to conservatively predict the DNBR reduction.
Since tne data with unheated rods could not be predicted by existing analytical methods, empirical models were derived. These models give the reduction in DNBR as a function of the clearance reduction between adjacent fuel rods. Two such models were derived, one based on
'the Westinghouse data and one based on the CE data.
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- Model Based on Westinghouse Data Data were presented by Westinghouse for the DNBR reduction at full contact and with no bow. No data at partial gap closure were presented. Westinghouse proposec, and the staff accepted, a straight line interpolation between these two points as shown in Figure 2.1.
This approach is conservative since one would expect the actual behav-ior to more nearly follow a curved line as shown in the sar.e figure.
The DNBR reduction would increase slowly in magnituce as the fuel rods bowed to contact. As the rods become close enouch so that tnere would be an interaction between the two rods, the DNBR reduction would then f
increase more rapidly. No physical mechanism has been postulated 1
which would lead to sudden large decreases in the DNBR for small or moderate gap closures. Thus, the straight line approximation is believed to be an overestimate of the expected behavior.
All manufacturers of reactor cores, including Westinghouse, include a factor in their initial core design to account for the reduction in DNBR that may result fron pitch reduction from fabrication tolerances and initial rod bow. The amount of this pitch reduction factor varies with the fuel design and the analysis methods which are used.
For any particular core this factor is not varied as a function of burnup.
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In developing the interim rod bow penalties described in this report, it became apparent that the penalty should be a function of burnup since the magnitude of rod bow is a function of burnup.
However, to maintain existing thermal margins early in core life when only a small amount of fuel rod bow is anticipated, the initial pitch reduction factor was included until such time as the rod bow DNBR reduction became greater. This is represented as the straight horizontal line on Figure 2.1.
2.3 Combastion Engineering.Model Combustion Engineering performed experiments to determine the effect of rod bowing on DNBR which included some cases in which the effect of partial bowing as well as bowing to contact e
was determined. Again, a straicnt line interpolation is used.
However, the point of zero DNBR reduction is not at zero clearance reduction but rather, at an intermediate value of clearance reduction. This is shown schematically in Figure 2.2.
The horizontal straight line, representing the initial pitch reduction factor is included as explained previously (5ection 2.2).
7 2.4 Models for Babcock and Wilcox and Exxon On Auaust 17, 1975 representatives of Rabcock and '.filcox met with the staff to discuss this problem.
Babcock and Wilcox did not present any data on the effects of rod bowing on DNBR. They had previously presented data to the staff on the amount of bowing to be expected in Babccck and Wilcox 15x15 fuel assemblies.
Because Babcock and Wilcox had no data on the effect of rod bow on DNBR, the staff applied the Westinghouse model to calculate the effect of rod bowing on DNBR for Babcock ana Wilcox fuel. The amount of fuel rod bowinq was calculated using the Babcock and Wilcox 15x15 fuel bundle data.
Representatives of the Exxon Nuclear Corporation discussed the effects of fuel rod bowing in the presence of an unheated rod on DNBR with.the staff on August 19, 1976. Exxon'has no data pertinent to this problem. Exxon has not performed DNB tests with bowed rods.,.
The first cycle of Exxon fuel has just been removed from H. B.
Robinson and the results of measurements on tne magnitude of rod The effects -
bowing have not yet been presen ed to the staff.
of fuel rod bowing for Exxon fuel were evaluated on a plant by plant basis as discussed in Section d.0.
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.8-2.5 Application of the Rod Bow /DNBR Model Using these empirical models, the staff deriveo DNBR reductions to be applied to both operating reactors and plants in the Construction Permit and Operating License review stage.
The procedure in applying these empirl 3.1 models is as follows:
Step 1.
Predict the clearance reduction due to rod bow as a function of burnup. An expression of the form AC=a+b1[BJ o
is used where AC
= fractional clearance recuction due to rod bowing Co a,b = empirical constants obtained for a given fuel design BU = burnup (region average or bundle average, depending on the fuel designer).
Step 2.
Apply the previously discussed empirical models of DNBR reduction as a function of clearance reduction using the value of AC/C calculated from step 1.
o Step 3.
The staff has permittea the reduction in DNBR calculated in step 2 to be offset by certain available. thermal marains.
These may be either generic to a given fuel design or plan: dependent.
An example of a generic thermal margin which would be useo to offset the DNBR reduction due to rod bow is the fact tnat the DNBR limit of 1.3 is usually greater than the value of DNBR above which 95% of the data lie with a 95% confidence.
The difference between 1.3 and'this number may be used to offset the DN8R reduction.
.c 9-An example of a plant specific thermal-margin would be core flow greater than the value given in the plant Technical Specifications.
A discussion of.the application of this method to Construction Permit and Operating License reviews is given in Section 3.0.
A discussion of the application and the results of this method to operating reactors is given in Section 4.0.
Th; application to reactors using Exxon fuel is also discussed in Ses. tion 4.0.
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10 3.0 Application to Plants In Construction Permit And Ocerating License Review Stage 3.1 CP Applications No interim rod bow DNB penalties should be applied to CP applications. The rod bow data upon which the interim limits have been based should be considered preliminary. There is sufficient time available to review the data and assess a penalty, if any, prior to -
We will advise each CP applicant of the nature of the OL stage.
interim penalties being applied to OL reviews and operating reactors. Since it appears that power derating is not necessary, there is no need to require design commitments at the CP stage; however, since limitations on operating flexibility may be required, we will need commitments from the applicant to (1) fully define the gap closure rate for prototypical bundles, (2) determine by experiments the DNB effect that bounds the gap closure from part (1), and (3) apply any calculated loss of thermal margin from steps (1) and (2) to reactor transient analyses. Such connitments should be part of our CP review effort.
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3.2 OL Applications Plants which are in the operating license review stage should consider a rod bow penalty. This penalty should be as described in Section 2.2 for Westinghouse or Section 2.3 for Combustion Engineering. Babcock and Wilcox plants should use the rod bow vs.
burnup curve appropriate to their fuel and the Westinghouse. curve of DNBR reduction as a function of rod bow.
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All applicants may propose appropriate thermal cargins (as discussed in Section 2.4) to help offset the calculated DNBR reduction. DNBR reductions could be greater for plants in the OL. review stage than for a similar operating plant because plant specific thermal margins cannot be.used to help offset the DNBR reduction resulting from appii. cation of the model.
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4.0 Application To Operating Reactors The section divides the operating plants into distinct categories and lists them according to the fuel manufacturer or reactor type. Operating plants which cannot be so categorized (such as plants with fuel supplied by more tnan one vendor) are placed in a separate category. The plants assigned to each category are listed in the appropriate subsection.
The conclusions reached in this section are in some cases dependent on conditions or analyst wnich are valid only for the present fuel cycle. Hence, the FAH or DNBR reductions wnich are given (or the fact that no such reduction is concluded to be required) is valid only for the present operating cycle.
4.1 Westinghouse LOPAR Fuel The designation LOPAR stands for low parasitic and refers to the fact that the guide tubes in the fuel bundle are made of Zircaloy.
Table 4.1 gives a list of the operating plants which fall into this classification.
TABLE 4.1: PLANTS WHICH CURRENTLY USE THE WESTINGHOUSE LOPAR FUEL
. ASSEMBLY 15x15 '
17x17 D. C. Cook Cycle 1 Trojan Cycle i Zion l~ Cycle 2 Beaver Valley Cycle 1 Zion 2 Cycle 1 Indian Point 3 Cycle 1
Turkey Point 3 Cycle 4 Prairie Island 2 Cycle 2 Indian Point
- Cycle 1 1
T TABLE 4.1 (cont.)
15x15 Turkey Point 4 Cycle 3 Surry 1 Cycle 4 Surry 2 Cycle 3 Kewaunee Cycle 2 Point Beacn 1 Cycle 5 Point Beach 2 Cycle 3 Prairie Island 1 Cycle 2 The reduction in DNBR due to fuei rod bowing is assumed no vary linearly with the reduction in clearance' between the fuel rod. (or fuel rod and thimole rod) according tc the model dis: ssed in Section 2.2.
The maximun value of DNBR reduction (at contact), obtain!d from the experimental data was used to calculate the DNBR reduction vs. bow for the 15x15 LOPAR fuel.
This DNBR contact reductio,n was adjusted for the lower heat flux in the 17x17 LOPAR ruel.
The clearance recuction is conservatively assumed to be given by the following equation for tne 15x15 (and 14x14) fuel, h =
a + b7Bu where is ti.e % reduction in clearance Bu is the region average burnup and a,b are empirical constrants fittec to' Westinghouse 15x15 rod bow data-l i
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For the 17x17 LOPAR fuel, tne clear ance reduction was calculated from the equation:
.I (AC) 15x15X ( T )15x15 t[)
L y(
AC/Co =
CU
' 7xl /
where L = the distance between grids I = moment of inertia of fuel roc On December 2,1976, Westinghouse informally showed the staff new data pertaining to the magnitude of roc bow as a function of region-average burnup in 17x17 fuel assemblies.
This data show that the above correction is probably conservative and that the magnitude of fuel rod bowing in 17x17 fuel rods can cetter be represented by an empirical function. This review is now underway.
The calculated DNBR reduction is partially offset by existino thermal margins in the core design.
For the Westinghouse LOPAR fuel design some or all of the following items were used in calculatino the tearmal nargin for the operating plants:
. cesign pitch reduction
. conservatively chosen TDC used in design *
. Critical heat flux correlation statistics (assumed in thermal analysis safety calculations) are mcre conservative tnan required.
. Densification power spike factor included *although no lo,nger required After taking these factors into accourt, the reductions in FaH shown in Table 4.2 were found necessary. All ooerating plants listed in Table 4.1 will be required to incorporate these reductions in FaH into their present operatina linits.
- TDC (thermal diffusion coefficient) is a measure of the amount of mixing between adjacent subchannels.
TABLE 4.2:
FaH REDUCTION FOR WESTINGHOUSE LOPAR FUEL CYCLE RED'JCTICN IN FAH (%)
15x15 17x17 ZION 182 1st Cycle (0-15 Gwd*/MTU) 0-2 ramp 1-13 ramp 0-6 ramp 2nd Cycle a
15 8
(15-24 Gwd*/MTU) 3rd Cycle (24-33 Gwd*/MTU) 6 15 10 These reductions in FaH may be treated on a region by region basis.
If the licensee chooses, credit may be taken for the margin between the actual reactor coolant flow rate and the flow rate used in safety calculations. Credit may also be taken for a difference between the actual core coolant inlet temperature and that assumed in. safety,
analyses.
In taking credit for ccolant flow or inlet temperature margin, the associated uncertainties in these quantities must be taken into account.
4.2 Westinghouse HIPAR and Stainless Steel Clad Fuel The designation HIPAR stands for high parasitic and refers to the fact that the guide tubes in the fuel bundle are made of stainless steel.
These two fuel types, HIPAR and Stainless Steel clad, are grouped together because the amount of bowing expected (and observed) is significantly less than that in the observed Westinghouse LOPAR fuel.
The plants which fall under this classification are listed in Table 4.3.
- Gwd Mwd
= 1000 MTU MTU
'% TABLE 4.3: HIPAR AND STAINLESS STEEL PLANTS Ginna Indian Point 2 San Onofre Connecticut Yankee The model f or the reduction in DNBR due to fuel rod bowing is assumed to be identical to that used for the LOPAR fuel.
For reactors in this category, the peak reduction in DNBR (corresponding to 100%
closure) was adjusted to correspond to the peak overpower heat flux of that particular reactor.
The amount of rod bowing for the plants listed in Table 4.3 which use HIPAR and stainless steel 'uel, was calculated by means of an f
adjustment to the 15x15 LOPAR formula. This adjustment took the form of the ratio amount of bow for assembly type
= (L/IE[ assy type amount of bow for LOPAR fuel (L/IE) LOPAR where L is the span length between grids I is the moment of inertia of the fuel rod E is the modulus of elasticity of the fuel rod cladding Ginna Cycle 6 The Ginna plant is fueled with 121 fuel assemblies.
Two of these are Exxon assemblies, and two are B&W assemblies.
The remainder are Westinghouse HIPAR fuel assemblies.
The e,xperimental value of DNBR 1
reduction was adjusted for heat flux and pressure from peak j
experimental to actual plant conditions.
Ginna took credit for the thermal margins due to pitch reduction, design vs. analysis
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values of TDC and fuel densification power spike.
These thermal margins offset the calculated DNBR reduction so that no reduction in FaH is required.
San Onofre Cycle 5 San Onofre is fueled with-157 bundles of 15x15 stainless steel ciad fuel. The experimental value of DNBR reduction was adjusted for heat flux and pressure from experimental to actual plant conditions.
San Onofre took credit for the thermal margins due to pitch reduction and the fact that a value of 1.75 was used for FaH in the safety analysis while a value of 1,55 was used in the Tecr.nical Specifications.
Because of adequate thermal margin, no reduction in FaH is required for San Onofre.
Indian Point 2 Cycle 2 Indian Point 2 is fueled witn HIPAR fuel buncles. Tne experimental value of DNBR reduction was adjusted for heat flux and
' pressure to actua' plant conditions.
Indian Point Unit 2 had thermal margin to offset this DNBR reduction in pitch reduction, design vs. analysis values of TDC, fuel densification power spike and a value of FaH of 1.65 useo in the design (vs.1.55 in the Tech Spec). Therefore, no reduction of FAH is required for Indian Point Unit 2.
Connecticut Yankee Cycle 7 Connecticut Yankee is fueled with 157 stainless steel clad fuel assemblies. The DNBR reduction at contact was assumed to be that used for the Westinghouse LOPAR 15x15 fuel.
No adjustment was made for heat flux. The value of pressure was adjusted to the overpressure trip set point value of 2300 psi.
Full closure will not occur in stainless steel fuel-out to the design burnup.
Connecticut Yankee has sufficient thermal margin in variable overpressure and overpower trip set points to accommodate the calculated DNBR reduction. Therefore no penalty is required; 4.3 Babcock and Wilcox 15x15 The reactors listed in Table 4.4 are fueled with B&W fuel.
TABLE 4.4: REACTOR USING B&W FUEL Oconee 1 Cycle 3 Oconee 2 Cycle 2 Oconee 3 Cycle 1 Rancho Seco Cycle 1 Three Mile Island :
Cycla 2 Arkansas 1 Cycle 1
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v The staff has reviewed the exten; of rod bowing which occurs wi th B&W fuel. Based on this review, the following equation was derived for the clearance reduction between fuel rods due to fuel rod bowing as a function of burnup:
=a+b'h[Bu Co where AC is tne fractional amount of closure Co Bu is the bundle average burnup and c,b are empirical constants fitted to B&W data The reduction in DNBR cue to fuel rod bowing is assumed to vary.
linearly with the reduction in clearance between the fuel rods (or fuel rod and thimble rod) but can never be lower than that cue to the pitch reduction factor used in thermal analysis, as explained in Section 2.2.
Babcock and Wilcox claimed and the staff approved credit for the fo'llowing thermal margins:
. Flow Area (Pitch) reduction 4
. Available Vent Valve credit
. Densification Power Spike removal
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. Excess Flow over that used in safety analyses
. Higher than licensed power used for plant safety analyses Based on this review and the th. mal margins presented by B&W to offset the new Westinghouse cata, Rancho Seco is the only plant for which a reduction in DNBR is required. Table 5 gives the values for the reduction of DNBR required at tnis time.
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TABLE 5:
DNBR REDUCTIONS FOR B&W PLANTS Burnup DNBR Reduction Rancho Seco Gwd.
Cycic 1 (0-15 MTli )
0 Gwd Cycle 2 (15-24 MTU )
1.6%
Cycle 3 (24-33 Gwd )
3%
MTU Plans must be submitted to. the staff to estab.sn how these reduction in DNBR will be accommodatec.
4.4 Combustion Engineerina 14x14 Combustion Engineering has presented data to the staff on the amount of rod bowing as a function of burnup. The staff used this data to derive the following model for CE 14x14 fuel.
h
=a.+
b V Bu,'
AC/Co = fraction of closure for CE fuel Bu is the bundle average burnup and a,b are empirical constants fitted to CE data
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CE has given credit for thermal margin due to a multiplier of 1.065 on the hot channel enthalpy rise usec to account for pitch reduction due to manufacturing tolerances. Table 4.6 presents the required reduction in DNBR using the model described above, after accounting for this thermal margin. Table 4.7 is a list of the reactors to which it applies.
A licensee planning to operate at a burnup greater than 24000 Mwd /MTU should present to the staff an acceptable method of
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?;commodating the thermal margin reduction show1 in Table 4.6.
.This may be done as part of the reload submittal if this burnup will not be obtained during the current cycle.
TABLE 4.6: EFFECT OF R00 BOWING ON DNBR IN REACTORS WITH COMBUSTION ENGINEERING 14x14 FUEL BURNUP REDUCTION IN DNBR Cycle 1(0-15%)
0 Cycle 2(15-24hyh) 0 Cycle 3 (24-33 lWh) 3%
TABLE 4.7: PLANTS FUELED BY CE FUEL TO WHICH VALUES OF TABLE 4.6 APPLY St. Lucie 1 Cycle 1 Ft. Calhoun Cycle 3 Millstone 2 Cycle 2 Maine Yankee Cycle 2 Calvert Cliffs 1 Cycle 1 4.5 Plants Fueled Partially With Exxon Fuel Palisades, H. B. Robinson, Yankee Rowe and O. C. Cook are. partially fueled with Exxon fuel. A discussion of these reactors follows:
Palisades Cycle 2 The Palisades reactor for Cycle 2 is fueled with 136 Exxon fuel assemblies and 68 Combustion Engineering fuel assemblies.
The Combustion Engineering Fuel was treated accordina to the Combustion. Engineering model for both extent of rod bow as a function of burnup and DN8R reduction due to clearance reduction.
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The Exxon fuel was assumed to sow to the same extent as the Combustion Engineering fuel, This issumption is acceptable since the Exxon fuel has a thicker cladding and other design features which should render the amount of bowing no greater than in the Combustion Engineering fuel, The DNBR reductitin was assumed to be linear with clearance reduction according to the Westinghouse type curve of Figure 2,1, The DNBR reduction at contact was based on the Westinghouse experimental data adjusted for the peak rod average heat flux in Palisades and for the coolant pressure in Paltsaces, The overpressure trip set point in Palisades is set at 1950 psi', At this pressure the magnitude of the required DNBR reduction is greatly reduced, The limiting anticipated transicat in the Palisades reactor results in a DNBR of 1.36. -The thermal margin between this value and the DNBR limit of 1.3 results in adequate thermal margin to offset the rod bow penalty, Yankee Rowe Cycle 12 Yankee Rowe is fueled with 40 Exxon fuel assemblies and 36 Gulf United Nuclear Corporation fuel assemblies, The fuel assembltes consist of 16x16 Zircaloy clac fuel rods.
The reduction-in DNBR due to fJel rod bcwing was assumed to Vary linearly with the reduction in clearance between fuel rods, The peak experimental conditicns used in the Westinghouse test were used to fix the penalty at full-closure, The calculated reduction in DNBR is still less than that which would procuce a DNBR less than 13 for 1
the most limiting anticipated transient (two pump out of four pump loss-of-flow). Thus, no penalty is required, H. 8, Robinson Cycle 5 H. B. Robinson is fueled with 105 Westinghouse fuel assemblies and 52 Exxon Nuclear Corporation fuel assemblies. The Westingnouse 15x15 DNBR penalty model was applied to the Westinghouse fuel with a correction for the actual heat flux rather than the peak expc.imental_
values. The Exxon fuel was considered to bow to the same extent as the Westinghouse 15x15 fuel so that the Westinghouse bow vs. burnup equation was also applied to the Exxon fuel. This assumption is conservative since the Exxon fuel has a thicker cladding and other design features which should render the amount of bowing no greater than in the Westinghouse fuel.
The DNBR reduction calculated by this method was offset by the fact that the worst anticipated transient for H. B. Robinson results in a ONBR of 1.68.
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l 5.0 References 5.1 Hill, K. W., at. al, "Effect of a Bowed Rod on DNB", Westinghouse Electric Corporation, WCAP 8176.
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FIGURE 2.1 WESTINGHOUSE MODEL 0 DNBR.
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W CURVE E
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bo Cw C
EXPECTED BEHAVIOR
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THERMAL DESIGN PENALTY
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INCLUDED IN ORIGIN AL DESIGN j
0 100%
A.E Co
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o FIGURE 2.2 l
l COMBUSTION ENGINEERING MODEL 0DNBR a:
O CE CURVEg 9
Oo 8
a:
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THERMAL DESIGN PENALTY I A'CLUDED IN INiTI AL DESIGN
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0 10_0%
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