ML18191A203

Response to NRC Request for Additional Information (Round 3 Questions)

ML18191A203
Person / Time
Site:	Columbia
Issue date:	06/30/1978
From:	Sobon L General Electric Co
To:	Stolz J Office of Nuclear Reactor Regulation
References
Download: ML18191A203 (33)

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SUBJECT:

LTR I Eh!CL i0 FORWARDING RE -PGhISES TQ LTR "NARK I I '"TP INi-G REQUEST" WIT!I ATTi REQUEST FGR ADDL INI=Q" MARI< I I CGNTAINhtENT POOL DYNAI! IC LOADS". DTD 04/i./7- ~ .

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PRO J ECTS DIVISION GENERAL ELECTRIC COMPANY, 175 CURTNER AVE., SAN JOSE, CALIFORNIA 95125 MFN-275-78 MC 681, (408) 925"3495 June 30, 1978 U. S. Nuclear Regulatory Commission Division of Project Management Office of Nuclear Reactor Regulation Washington, DC 20555 Attention: Mr. John F. Stol z, Chief Light Water Reactors Branch No. 1 Gentlemen:

SUBJECT:

RESPONSES TO NRC RE/VEST FOR ADDITIONAL INFORMATION (ROUND 3 QUESTIONS)

Reference:

Letter "Hark II STP Information Request" with attachment, "Request for Additional Information"-

Mark II Containment Pool Dynamic Loads" to I. Peltier (NRC -DPM) from C. Anderson (NRC DSS),

dated April 18, 1978 Ten copies of the subject responses are being provided by General Electric Company on behalf of the Mark II Owners Group for your review as part of the Mark II Containment Program. This question series, designated "Round 3", deals primarily with the DFFR.

Although this particular submittal is independent of other document-ation, these questions and responses will be given an "M" series number and consolidated with the Round 1 and Round 2 question sets currently comprising Appendix A to the DFFR and scheduled for submittal in July, 1978.

The information in the responses will be incorporated into the corre-sponding sections of the DFFR text in the next DFFR revision.

7A1860033

GER EII AL 9 ELECTRIC J. F. Stol z Page 2 June 30, 1978 Any questions regarding this submittal should be directed to L. H. Frauenholz, the Mark II Containment Licensing Engineer, telephone

,(408) 925-2623.

Very truly yours, L. J. Sobon, Manager BWR Containment Licensing Containment Improvement Programs LJS: 1 w/1406-1407 cc: C. Anderson (NRC H. Brinkmann (Mark II Owners Group)

H. Chau (Mark II Owners Group)

L. Gifford (GE, Bethesda)

I. Peltier (NRC)

R. Tedesco (NRC)

Fi le: 3.2.7c

QUESTION 020. 64 The data'base from which chugging loads on downcomers was developed indicates that lateral loads were also observed at vent clearing. These loads were as high as 3.5 kips (See Table 3-3 of NEDE 21078-P).

Therefore, it is our positior. that a design load not less than 3.5 kips be specified for downcomers during vent clearing. This static equivalent load should be used for each plant with a vent natural frequency less than 7 Hz. For a vent natural frequency greater than 7 Hz a higher vent clearing static equivalent load should be specified and )ustified.

RESPONSE

As indicated in the Application Memorandum for Phases I, II, and III of the 4T test series (NEDE 23678P), no significant lateral loads were observed between the start of the tests and the onset of chugging. However, in the referenced tests (data Table 3-3 of NEDE 21078), static equivalent measurements of lateral loads up to 3.5 kips were observed. These loads are unique to the test setup (Figures 3-1, 3-1A, 3-2 and 3-3 of NEDE 21078) and are not applicable to either the 4T facility or the Mark II containment.

In the test facility where the 3.5 Rip static eouivalent loads were measured, no drywell volume existed except for the air occupying the vent line prior to valve opening. In contrast to the 4T facility or a Mark II containment the referenced facility vented a very small quantity of non-condensable gas to the pool followed by immediate steam condensation. In these tests without a drywell, the vent pressure typically increased by approximately 1 to 1.5 ATM while the small air volume cleared, then dropped approximately 2 ATM as condensation of the following steam commenced. This loss in vent pressure is eviB'ence of the loss of the bubble at the vent exit and an attendant reentry of water into the vent.

The bubble collapse in the referenced facility (similar to a chugging event) caused'he lateral load (during vent clearing) which would not have occurred if a drywell were present. The 4T or Mark II drywell would continue air flow to the bubble at the vent exit which would be gradually diluted with a larger flow of steam which in itself is capable of maintaining a positive bubble at the vent exit. In the absence of a collapsing vent exit bubble, lateral loads. would

QUESTION 020.64 - contirued not be expected to occur during the 4T or mark II vent clearing transients; this vas confirmed in the 4T tests. The DFFR methodologv is consistent vith these results.

The downcomer vents are designed to accomodate the lateral loads occuring during chugging; these loads bound the vent clearing lateral load design consideration for the downcomer vents.

QUESTION 020.6 The data Th dats, base (NZDE-21078-F) from vhich the chugging load specification for dovncomers vas developed vas obtained vith a vent configuration unencumbered by flanges or other protuberances located in the vicinity of the vent exit. It is our position that these load specifications are not apnlicable to any Mark II plants vith vents vhich are flanged at the vent exit. Either the vent exit flanges should be removed or additional steam tests should be conducted vith a vent exit flange.

RESPONSE

have been removed from all plants covered by the Mk

'tII Flanges or other protuberances located in the vicin y of the vent program.

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UESTION 020.66 The static equivalent load for a downcomer depends on the natural frequency of the downcomer. The current load specification o f 8.8 kips was obtained in a test facility with a downcomer natural frequency of about 7 Hz. This load has not been demonstrated to be conservative for downcomers with a higher natural frequency. For a vent natural frequency greater than 7 Hz, a higher lateral load should be specified and )ustified. Additional information is needed to establish a static eauivalent load for downcomers with a natural frequency greater than 7 Hz.

In addition, we require that each Mark II plant provide an evaluation of the downcomers utilizing the dynamic forcing function in Task A.13 in the Mark II supporting program an confirmation of the static equivalent load evaluation. The static equivalent and the dynamic loads for the downcomers described above are based on tests with downcomer diameters of 24 in. or less. Additional information will have to be provided to establish lateral loads for downcomer with a larger diameter. 1

RESPONSE

Certain plants covered by the MKII supporting program employ vent systems with natural frequencies greater than 7 Hz. To confirm that the 8.8 kip static equivalent load is adequate for design assessment, all MKII vent

'systems will be analyzed for the dynamic forcing function defined, in Task A.13 of the MKII program. Results will be presented for NRC review by applicants on an individual basis.

.6 ' '.. 6 6 - .

a. It is noted that the force magnitude distribution employed for the probabilistic analysis of multiple dovncomer loading is taken from Table 3-6 of NZ)E-21078-P. These data were obtained during steam blowdovn with significant air admixture (Tests 5 and 7) Thus, they do not correspond to the "worst" loading case (O~o air 'admixture) vhich yields the 8.8 kip maximum lateral load specification. We require that the multiple downcomer loading be modified so as to be consistent vith this vorst case distribution.

RESPONSE

The force magnitude distribution data for the 0~~ air admixture tests is not available for the tests reported in NEDE-21078-P. To conservatively incorporate the effects of 0/o air admixture into multiple dovncomer analysis, the force per dovncomer from Figure 4>>10 of the DFFR (NED0-21061-P, Rev. 2) =vill be multiplied by the factor 8.8/7 .0 = 1.26 for design assessment vith a maximum of 8.8 kips per vent. The basis for this factor is that the force magnitude distributions from Table 3-6 of NEDE-21078-P (for vhich the maximum load is approximately 7 kips) are related to the expected distribution for Of air admixture tests (for vhich the maximum load, is 8.8 kips according to the ratio 8.8/7.0 = 1.26).

This assumes that the force magnitude distribution shifts by the factor 1.26 for the Og air admixture tests, thereby conservatively incorporating the effects of OC air on the current DFFR methodology for multiple downcomer loadings.

QUESTION 020.67b (Refering to Section 4.3.2 of DFFR (NED-NED0-21061-P, Rev. 2)

b. f Since the directxon o th e combined loads from multiple dovncomers s ar bitrary rary, assumption 2 of the analysis is un)ustified. Me

=require that th e magn itu d e of the resultant of all forces be emp looyeed to define multiple dovncomer loads. The analy al sis and results (Figures 4-10 and 4-10a) should be modified accordingly.

RESPONSE

'al The methodology underlying assumption 2 ccan bee sholem to be correct, so that no changes in Figures 4-10a are required.

The assumption and its context are as follovs:

4 ~ 3~2~4 ~ i 1 Analys s "A probabilistic A pro a x s c analysis of simultaneous lateral loading on groups of devncomer vents has been performed in the manner of Appen The analysis used these assumptions:

"1 0 The angle of the chugging force on a single dewncomer is random and, is uniformly distributed around the horizontal plane.

"2. Since the component of the chugging force r in a p articular direction t t f is of interest, th e orce r e magnitude distribution is multiplied by the distribution ofthe cosine of the angle of the force.

The question is interprete d t o b e on the assumption that the dovncomer group lateral chugging force of interest is the onee inn a p articular direction, not the resultant force.

A static equivalent lateral force is to be calculated at exits of various sized groups of dovncomers, due to chugging. u in . The value for each group is to have a predetermined exceedance probabili ty, and is calculated under specific technical assumptions listed in NEDE-210661-P. - . The structural designer li app es th e force in each of several directionss in n the horizontal plane for appropriate dovncomer group sizes. iz s. The quesuestion is whether the probabili ty ues

QUESTION 020.67b- continued distribution of group lateral force shouldd be that of the magnitude of the resultant lateral force over many pool chugs ('.e. (x.e., simultaneous chugs at all dovncomers in the group), as advocated in the HRC question, or that the distribution should be that of the lateral force along any one chosen orientation, as defined in the DFFR.

To illustrate why the di s t r ibu tion in only one orientation should be used, i

consider any one ana 1 ys s vhi c h the structural designer ~ill perform. In the analysis, the chosen group lateral force vill be a p nlied in one direction, l

e.g,, 8 = 0. A group a t era ral force value acting in that direction (having the desired exceedance probability) is required. The underlying group lateral force distribution for the pro b a bility statement s can be formed by considering a series of pool chugs. In th e firstrs pool chug, a different random single dovncomer latera1 force is applied to each downcomer in the g rou p in a random orientation. The single dovncomer force distribution is stated and the orientation distribution is assumed to be uniform around aroun 3603 . The resultant of the group lateral force can be found, but v v ill have only a certain component acting in tthee 8 = 0 orientation being analyzed. Repeating this process for each pool chug vould build up a histogram of group lateral forces in the 8 = 0 orientation. Equivalently, the histogram of group lateral force at 8 = 0 could be formed by finding gus J t th e 8 -" 0 component of each single downcomer umming these over all dovncomers in the group, for each lateral force, an d summ pool chug. {Rather than carrying ou t this simulation procedure, the probability distribution of group lateral force at 8 = 0 is actually found by convolution, as described belov.) The resulting distrxbution of o g rou p lateral force oriented to 8 = 0 is then treated in the manner described in NED- NEDE-21061-P to fulfillthe desired probability s t a t emen t for many pool chugs, and the dovncomer group lateral force required for the analysis in the 8 = 0 orientation is obtained.

The same probability statement applies to dovncome mer gr ou p lateral forces in other orientations to be investigated. Moreover, over due to the assumption that single dovncomer lateral forces are uniformly distributed in 8, the foregoing ans1ysis at 8 = 0 is equally applicable at any other o 8; it need nor be repeated for the other va1ues o f 6'h ; e same s group force value is used for analysis in the other orientations.

For information, the convolution method actually used to form the histogram of group lateral force at 8 = 0 is described as follows. Two maJor stages of convolution are used. In the first stage,, the distributions of single downcomer lateral force F and of orientation component cos 6 are discretized into cells. To find the component in the 6 = 0 orientation of each F in the distribution, F " cos 8 is required (8 being measured from 8 = 0). To form the distribution of F " cos 8 (in place of the distribution of F), F " cos 6 is found exhaustively for all combinations of F and cos 6 cells; at the same time, the probability of each F " cos 8 product is the product of the probability in each F and cos 8 cell, since F and 8 values are assumed to occur independently. Collecting F " cos 6 products into cells and summing the probabilities for each entry gives a histogram of F " cos 9 for a single downcomer, as required. This is the distribution of single downcomer lateral forces oriented in one chosen 8 = 0 orientation. In the second stage, F " cos 6 values are summed over all downcomers in the group by the same convolution process of forming the sums, over the number of downcomers in the group, of all combinations of F " cos 8 cells exhaustively, together with the corresponding probabilities found as theproducts of the probabilities of the participating cells. In this way, a histogram of lateral force of the group of downcomers in the 8 = 0 orientation can be formed,.

This explanation of how the group lateral force distribution for a particular orientation is found, and. used clarifies why the group force probability distribution in a particular orientation rather than the resultant group force distribution is appropriate for the application.

UESTION 020.68 Based on our reviev of the 4T test reports (HEDE-13442P-Ol, NEDE-13468P) and the Phase I, II, III Applications Memorandum dated January 1977, it is our position that the specification for maximum pool svell elevation account properly for observed trends with submergence and state ofthe blovdovn fluid. We require that the maximum pool svell elevation speci-fication consist of the maximum of either 1.5 times submergence or that predicted by the pool swell analytical model using a polytropic exponent of 1.2 for vetvell air compression.

RESPONSE

The pool swell analytical model is used to predict bulk pool svell trans-ient velocity and acceleration for purposes of calculating impact and drag loads on structures located vithin the svell zone. The model is excessively conservative for prediction of maximum pool swell height or vetvell airspace compression. The specification of maximum svell height in NEDO-21061 vill be modified to be the greater of:

1. 1.5 vent submergence or

2. the elevation corresponding to the dryvell floor uplift differential pressure used for design assessment The pool surface elevation corresponding to this maximum vetveU. airspace compression vill be calculated assuming a polytropic process vith an exponent of 1.2.

QUESTION 020. 6o Our reviev and analys s o f the data base (4T tests and EPRI results) for upvard ~P suggests th a t thee 2.5 psi specification is inadequate for certain Mar k XI p lants. Ve require that the current specification be replaced by:

Q PUP = 8.2 - 44F {psi) OCF~(0.13

+PUP "- 2.g {psi) F) 0.13 vhere P is a plant unique parameter defined by ABiAP VS F = 2 VD (AV)

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vtth AB -" break area AP = net pool area AV = total vent area VS = vetvell air space volume VD = dryvell volume

RESPONSE

The plant unique parameter correlating pool svell sv up lift differential pressure on the dry- fl drwe 11 ooor vill be calculated by each applicant and provided for NRC reviev on an individual basis.

gUPSTy00 020.70 The DFFR (NEDO-21061) methodology for estmating stead s y state drag loads on submerged structures is unacceptable for thosse cases where the structures I

represent signa'fican t blockage to the pool water slug motion. Ve require that the drag coefficients used to compu m utee the loads be modified according to traditional literature references which take ake account of the effect of blockage.

RESPONSE

i Structures such as the brac ng that a ssupport downcomer vents experience drag loads as a ressuit oof thee pool water slug motion. The distance between bracing i es ranges from virtually touching to far apart. Thee bracing lieses in n a plane er endicular perpen c to the pool slug motion, i.e.,e. an orientation or en a known in the literature f'tion as a side<<by-side con xgura The d ag coefficien tss. C d

for this condition ea xze ccase of two cylinders locate d sp can be analyzed by considering the idealized s dee by side (see Figure 1).

flow For values of9 > approximately 1 3d , thee literature shows no interference effects, and t h e dr ag is accurately predicted by co nsideri ng the cylinders independently of each other. r. For vvalues ues oof P less than approximately 3 d the effects of the sheer layer in t eracction between the lower boundary la er of k'1 layer with the upper boundary layer of t22 resu resu1tss inn a lowering of the values of CD (see Figure 1).) Mhen J= d, (or when the cylinders touch,, thee C c can be D

estimated as that of a flat plate of length 2d.

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RESPONSE TO QUESTION 020.70 - continued Another idealized situation called the tandem arrangement is discussed in the literature. Although this arrangement is not directly applicable to vent bracing, it may be representative of other submerged structures located in some suppression pools. The tandem arrangement is illustrated in Figure 2.

FLOW Figure 2 The discussion can be simplified by considering three separate regions:

a) J'>> approximately 30d, no interference, b) approximately 3d~ g (

approximately 30d partial interference, and c) d C' g approximately 3d mutual interference. For region a), no interference effects exist and the structures can be analyzed independently of one another. For region b) partial interference occurs; only the dovnstream structure 82 is affected. (see Figure 2).

The upstream structure P1 does not "see" the downstream one. In all cases of interference, the drag coefficient CD is less than it vould be without the influence of the upstream cylinder. This is because the vake of the upstream cylinder introduces turbulence into the incoming flov; that the downstream cylinder experiences this turbulence hastens the onset of boundary-layer transition on P2, thereby lowering the value of C ~ For region c) mutual interference occurs vith CD for 82 being lover while CD for k'1 is larger.

D for 81 increases because of deleterious interference effects on the vake formation. Hovever, the maximum increase is'bout 20/~ and. occurs at about Summarizing the above discussion, for evaluation of submerged structure drag loads the steady-state drag coefficient, C, should be treated as follovs:

(i) Case 1 (Figure 1):

~ For g ~~ 3d, use steady-state C as before, For l.ldllJ 43d, use steady-state C as before.

~ For J 4 1 . ld,, use steady-state C for a flat plate of width 2d normal to flov

e 11 RESPONSE TO QUZSTIOH 020.70 - continued

{ii) Case 2 (Figure 2):

e For g <<~ 30d, use steady-state CD as before.

~ For 3d 4 $ ~ 30d, use steady-state C as before.

o For.d C3d, multiply the steady-state C by 1.2 , for structure b'1; for structure 8'2 - use CD as before.

Among the more important references used were the following:

1. C. Dalton and J. M. Szabo, "Drag on a Group of Cylinders" Transactions of the ASME, Journal of Pressure Vessel Technology, PAGES 152 - 157, Feb. 1977.

2. M. M. Zdravkovich, "Review of Flow Interference Between Two Circular Cylinders in Various Arrangements", Transactions of the ASME, Journal of Fluids Engineering, page 16, Dec. 1977

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QUESTION 020.71 In the response to NRC ques tions M020.58(4) (NRC questions dated January 14 t -1977) it is stated that tt ool svell for Hark II contain-Calculations of pool ments using the ana lyti yt ca 1 mo del utilize the appropriate cal'culated dryvell pressure response (NEDM-10320) as an input. )I It i,s our position osition that the specification of pressure history xs an essential t'al element of the DFFR methodology and that the particular choice cited above has not been demonstrated as no to be appropriate.

To )ustify require such use, ve req that pool svell calculations be made for selected. 4T tests using dryvell pressure response nse corn p uted according to NEDM-10320 in lieu of the measured dryvell pre ressure histories. The selected 4T tests are the tvo saturated liquid blovdowns made during the phase II test series (Runs ( 3 6 an d 37). The response (pool svell elevation, veloc ity, bu bblee pressure) calculated in this manneer should be compared vith measured values and vith similar calculations made using the measured, dryveell pressure histories.

RESPONSE

For Mark II plant design assessment, the calculate dryvell p ressure response (NEDM-10320) has been conservatively chosen as in np ut to the Mark II pool svell model. To illustrate this conservatism, the poool sswell model calculations vere erformed for 4TT test performed es runs 36 and 37 using the computed, dryvell pressure response (according to NEDM-10320) as'input. These calculations ons vere compared to both the measured 4T pool svell response and the poo ool swell calculations using the measured 4T drywell pressure histories. The correspon s ondi ng p ool swell elevation, velocity, and bubble pressure are plotted in the attached figures.

The pool surface elevation curvess (Figures (Fi res 1 an and 2) shov that results using NEDH-10320 dryvell pressures yield pool svell eelevations vhich exceed the measured 4T test d a t a, an d also exceed the results obtaine d usi ng the 4T-measured dryvell pressure.

The pool surface velocity (Figures 3 and 4) curves illustrate that the maximum velocities calculated using HEDM-10320 pressures are greater (as in run 37) or comparable (as in run 36) to those measured in the 4T tests.

Additionally, pool surface velocities using HEDM-10320 input consistently exceed the velocities calculated using the 4T measured dryvell pressures.

4 The bubble pressure curves (Figures 5 and. 6) shov that bubble pressures calculated using HEDM-10320 dryvell pressures provide an upper bound on both the measured 4T data and the calculated values using the measured 4T dryvell pressure.

Based. on the above results, using the calculated dryvell response {using HEDM-10320) for pool swell calculations results in conservatively-predicted pool swell parameters for design assessment.

pooL SURFACE ELEVATION RESPONSE WITH 4T

MEASOREO ORYWELL RUN BACK 36 PRESSURE INPUT RESPONSE WITH 18 NEDM-10320 INPUT RUN BAH 56 4 T TEST DATA 16 14 12 CD 10

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UESTION 020.72 The DFFR impact 3.oad specification for small structures is inadequate. The current load specification consists of a peak pressure-velocity correlation developed from the Mark III PSTF tests. The peak pressure is used in con)unction with an "average" 7 msec duration to completely define a pressure pulse. The use of the same 7 duration for all situations has not been )ustified, thus the current specifications are incomplete. We require that the load specification be modified so as to establish a conservative pulse for all Mark II anticipated situations of target geometry, target size, pool flatness and pool approach velocity.

RESPONSE

The impact pressures presented in Figures 4-34, 4-35, and 4-36 of DFFR are actual test data. These pressures do indeed depend on the width of the target and the flatness of, the approaching pool surface. In the Mark II suppression pool the pool surface is relatively flat; therefore all of the PSTF impact test data using circumferential targets are prototypical of the Mark II conditions.

Furthermore, the type and, the sizes of the targets tested were also prototypical of the Mark II plants. The load specification in DFFR is therefore a direct application of the test data without any extrapolation.

With regards to the duration of the load, the DFFR specified 7 milli-seconds-The 7 milli-seconds duration was chosen because it is the most representative time duration based on tests using circumferential targets.

The Brookhaven National Laboratory report "Impact Loads on Structures Above Mark II Containment Pools," George Maise, February 2, 1978, indicates that the peak pressure duration is dependent on target geometry and size, pool flatness, and. pool approach velocity. The Mk II Owners concur that the concerns raised. by the Maise report are technically sound.

The Mark II plants are investigating the effects of the variables mentioned in the Maise report on the structural impact loads and the correspondence between PSTF pool swell and expected, Mark II pool swell. The results of these investigations will be used to verify the current DFFR impact pressure methodology described above.

'd UESTION 022 73 Based on our review of 14 test reports, application memorandums and the pool swell analytical model report (NEDE-21544-P), it is our position that the specification of pool swell velocity according to the analytical model prediction p does not provi e su fficient margin to cover uncertainties in the measurements. We es tima te this uncertainty to be on the order of + 10$ .

Accordingly, we requ ire th e aaddition of a 10P margin to the values predicted

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by the analyses for pool swell velocity.

RESPONSE

In the report NEDZ--21544<

on thxs conserva M020.71 where the calculated meximum pool swell velocit ' is 5>>10'igher by using as the i h forc ng function un the calculated drywell pressure {using NEDM-10320) rather than the 4T-measured drywell ell p ressure. This demonstrates conservatism heretofore not apparent because the model/data comparisons in 'e NZDE-21544-P using "applications assumptions " weree p erformed assuming the measured rather than calculated 4T drywell pressure. Therefore, the current methodology does prov ide su ffi i c en t margin to cover the uncertainties in the computed pool swell velocity. QUESTEON 020 74 The current chugging load specification consists of an oscillatory pressure load derived from a conservative chug in the 4T facility. This load includes the FSI related "ring out" of the test walls. The actual load is an impulsive load resulting from collapse of steam bubbles at the exit of the vents. To confirm that the direct application of the pressure signal to containment valls is conservative, additional information is needed. Vali pressure measurements during a conservative chug at the plane of the vent exit should be used to construct an impulse load, at the vent exit. The impulse load. specification should be used in the'coupled fluid-structure analytical model of the 4T facility described in NEDE 23710-P to confirm the conservative nature of the current chugging va11 load specification.

RESPONSE

The concerns expressed in this question have been addressed in the forthcoming report: "Lead Plant Containment Response to 1'mproved Chugging Load Definition,"

available in July, 1978.

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QUESTION 020 75 The supporting program report REDO 21297 includes an LTP effort to define main vent condensation submerged structure loads. The current DFFR and lead plant program do not include a definition for this load. Either provide a load for steam condensation submerged structure drag for the STP or )ustify deferring this item to the LTP.

RESPONSE

The lead plants have developed individual methods for determining these main vent condensation submerged. structure loads in their plant specific responses to these questions, A Mark II generic program is currently underway to determine the loads due to steem condensation and will be available about the fourth quarter of 1978. This Program will confirm the adequacy of the lead plant assessments and establish a basis for the remaining plants.