ML20209E537

Forwards Request for Addl Info Re Small Break LOCA Code, NULAP5,per Connecticut Yankee Atomic Power Co 870319 & 0416 Responses to NRC 870212 & 0312 Requests.Info Requested Should Be Submitted within 30 Days of Ltr Receipt

ML20209E537
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	04/27/1987
From:	Frank Akstulewicz Office of Nuclear Reactor Regulation
To:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
References
TAC-45830, NUDOCS 8704300071
Download: ML20209E537 (10)

Text

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April 27, 1987 Docket No.: 50-213 Mr. Edward J. Mroczka, Senior Vice President Nuclear Engineering and Operations Northeast Nuclear Engineering Company Post Office Box 270 Hartford, Connecticut 06141-0270

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION CONCERNING THE HADDAM NECK PLANT SMALL BREAK LOCA CODE - NULAP5 - (NRC TAC # 45830)

By letters dated February 12 and March 12, 1987, the staff requested additional information concerning the small break loss-of-coolant accident code for the Haddam Neck Plant. By letters dated March 19, and April 16, 1987, Connecticut Yankee Atomic Power Company (CYAPC0) provided responses to the requested information.

usring our continuing review of this topic, the staff has identified 11 74!tional concerns which need to be resolved in order to complete our

w iew. Enclosure 1 contains the requests for additional information. In orce to complete our review of the NULAP5 code prior to the refueling cutap , the staff requests that responses to these questions be submitted within 30 days of receipt of this letter. If you are unable to meet this schedule, your licensing department should contact me at (301) 492-4790 with a proposed schedule for submittal of the necessary information.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P. L.96-511.

Sincerely, Original signed by Francis M. Akstulewicz, Jr., Project Manager Integrated Safety Assessment Project Directorate Division of Reactor Projects III/IV/V Special Projects

Enclosure:

DISTRIBUTIQN As stated DocketFilj% JLD FAkstulewicz NRC PDR EJordan MShuttleworth cc: See next page Local PDR BGrimes ACRS(10)

ISAPD File JPartlow SSun DCrutchfield NThompson 0FC:ISAPD :LA:ISAPD :D:ISAPD i bhE$Fbstukeic j h.

__________________ g. f. ______________________________________________________________

DATE:04/g7/87 :04/gp/87 :03 7

' e704300071 870427 ONE ME M PDR ADOCK 05000213 P PDR

1. ~ UNITED STATES

!" p, NUCLEAR REGULATORY COMMISSION g :j WASHINGTON, D. C. 20555 g April 27, 1987 Docket No.: 50-213 ,

Mr. Edward J. Mroczka, Senior Vice President Nuclear Engineering and Operations Northeast Nuclear Engineering Company Post Office Box 270 Hartford, Connecticut 06141-0270

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION CONCERNING THE HADDAM NECK PLANT SMALL BREAK LOCA CODE - NULAP5 - (NRC TACf 45830)

By letters dated February 12 and March 12, 1987, the staff requested additional infonnation concerning the small break loss-of-coolant accident code for the Haddam Neck Plant. By letters dated March 19, and April 16, 1987 Connecticut Yankee Atomic Power Company (CYAPCO) provided responses to the requested information.

During our continuing review of this topic, the staff has identified 11 additional concerns which need to be resolved in order to complete our review. Enclosure 1 contains the requests for additional information. In order to complete our review of the NULAP5 code prior to the refueling outage, the staff requests that responses to these questions be submitted within 30 days of receipt of this letter. If you are unable to meet this schedule, your licensing department should contact me at (301) 492-4790 with a proposed schedule for submittal of the necessary information.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required l under P. L.96-511. l Sincerely, __

"^~

Francis M. Akstulewicz, r., Project Manager

, Integrated Safety Assessment Project Directorate Division of Reactor Projects III/IV/V Special Projects

Enclosure:

As stated l cc

See next page i

o . .

Mr. Edward J. Mroczka Connecticut Yankee Atomic Power Company Haddam Neck Plant-cc:

Gerald Garfield, Esquire Kevin McCarthy, Director Day, Berry & Howard Radiation Control Unit Counselors at Law Department of Environmental City Place Protection Hartford, Connecticut 06103-3499 State Office Building Hartford, Connecticut 06106 Superintendent Haddam Neck Plant Richard M. Kacich, Manager RFD #1 Generation Facilities Licensing Post Office Box 127E No.-theast Utilities Service Company East Hampton, Connecticut 06424 Post Office Box 270 Hartford, Connecticut 06141-0270 Wayne D. Romberg Vice President, Nuclear Operations '

Northeast Utilities Service Company Post Office Box 270 Hartford, Connecticut 06141-0270 Board of Selectmen Town Hall Haddam, Connecticut 06103 Bradford S. Chase, Under Secretary Energy Division Office of Policy and Mansgement 80 Washington Street Hartford, Connecticut 06106 Resident Inspector Haddam Neck Nuclear Power Station c/o U.S. NRC P. O. Box 116 East Haddam Post Office East Haddam, Connecticut 06423 l Regional Administrator, Region I . . . - l U.S. Nuclear Regulatory Commission l 631 Park Avenue <

King of Prussia, Pennsylvania 19406 l

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ENCLOSURE 1 Request for Additional Information Concerning the Small Break Loss-of-Coolant Code - NULAPS

1. Northeast Utilities response to question Q.II.5 did not discuss water slug formation due to HpI at the Haddam Neck plant. The question was intended to clarify how well NULAPS calculates water slug formation (filling of a volume with volumes essentially steam filled up- and downstream of the filled volume) in Haddam No:k SBLOCA analyses. To resolve the question, clarify whether NULAPS is capable of modeling water slugs. How sensitive is this modeling to the noding used? Also, clarify whether water slugs were ever calculated in Haddam Neck SBLOCA analyses. If no water slugs were calculated, clarify whether or not this could be due to the nodalization used in the cold legs.

P. It was stated in respnnto tn question Q.IV.2, that the Soniscale 1 1/2 loop pump data was used for the two-phase homologous curves in the'NULAPS model for the Haddam Neck pump because it was the only data available for all the various pump operating regions. An additional source of two-phase pump data is the CE-EPRI 1/5 scale pump data.1 The pump used in this test program had a specific speed of 4209 rpm as compared to a specific speed of 926 rpm for the Semiscale 1-1/2 loop pump. Discuss whether the data from the CE-EPRI tests was considered for use in the Haddam Neck pump model. If this data was considered but not used, clarify why it was not used, i .

3. Northeast Utilities indicrted in response to question Q.IV.3 that the pump model in NULAPS was assessed against a calculated pump coastdown from the Haddam Neck FDSA and a number of assessment calculations for LOFT and Semiscale tests. A review of the LOFT and Semiscale assessment calculation .

results did not find any code / data comparisons (such as loop flow rates, pump speed, pump differential pressure, etc.) that would verify the adequacy -

of the pump model in NULAPS. Provide this type of code / data comparisons for the LOFT and Semiscale assessment calculations, using a time scale that

. allows a meaningful comparison between the code and the data to be made, so that the adequacy of the NULAP5 pump model can be verified.

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4. In response to question Q.V.1, Northeast Utilities stated that NULAP5's ability to calculate single- and two-phase natural circulation was' assessed through comparison to the integral system tests from LOFT and Semiscale. A review of the LOFT and Semiscale assessment calculation results did not find r

any code / data comparisons (such as loop flow rates) that would verify the adequacy of NULAPS to calculate natural circulation. Provide this type of code / data comparisons for the LOFT and Semiscale assessment calculations, in a format that allows a meaningful comparison between the code and the data to be made, so that the adequacy of the NULAPS , natural circulation models can be verified.

5. Additional information on the clad swell and rupture model was requested in question Q.VI.11. In response, Northeast utilities stated that the full description of these models was found in the NULAp5 manual. The section in the NULAp5 manual on the fuel models (Section 3.2.4) was reviewed again and infornation on the clad oxidation model, the gap conductance nodel and the fuel rod internal pressure model was found. Also there was a general description of how modifications were made to the geometry of the heat structures and hydrodynamic components but no informatitn was found describing how NULAP5 calculated the geometry changes. That is, no information was found describing how the clad swell and; rupture models work. Therefore, provide for review a description of the clad swell and rupture models.

6. The response to question Q.VI.27 provided information on the new critical heat flux model in NULAPS. This model used the Biasi correlation to calculate critical heat flux at high inass fluxes and the modified Zuber correlation for low mass fluxes. This raodel was taken from RELAP5/M002.2 '

Because the critical heat flux model used in all previous NULAPS assessment -

calculations was replaced, provide comparisons of NULAPS results to at least .

one set of critical heat flux data applicable to SBLOCAs to ensure the new model has been properly implemented in NULAP5.

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7. Qulstion Q.IX.1 requested Northeast Utilities to explain the differences  !

between a number of equations given in the NULAP5 manual and the RELAP5/ MOD 1 manual.3. An answer to this question was not included in Reference 4.

Provide the answer to question Q.IX.1.

8. In the NULAPS manual, Section 2.0, it was stated that the IBM version of RELAP5/ MODI, cycle 6, was updated to become cycle 14. It was assumed this process included all the updates from cycle 7 to 14. It was then noted in the manual that the code was being updated from cycle 14 to 18. The response to question Q.IX.2 stated that one update to RELAPS/M001 in cycle 18 would not impact the results of the assessment calculations in the NULAPS manual because the original update to RELAP5/M001, cycle 14, was not included in NULAP5. Because of this response, it is not clear whether all the updates to RELAP5/M001 from cycle 7 to 18 have been included in NULAP5.

Question Q.IX.2 also asked Northeast Utilities to provide information on the status of each update to RELAP5/M001 from cycle 19 to cycle 29, the, final released version of the code, with respect to its implementation in NULAPS.

You stated that the updates from cycle 19 to cycle 25 were included in a test version of NULAP5 but a final decision had not been made on the Implementation of these updates in NULAP5. You also stated that known code  !

error corrections would be implemented in NULAPS as they were released by the RELAP5/M001 developers. Because cycle 29 is the final released version of RELAP5/M001, it is clear that all corrections for kn'own code errors have been released by the RELAPS/ MODI developers. These error corrections are included among those listed in the update sununary sent with the esrlier set of questions.5 Clarify the development history of NULAP as it relates to j RELAP5/ MODI and the updates to the RELAPS/M001 code. If any of the cycle 7 to 29 updates to RELAPS/M001 were not included in NULAP5, identify those updates and state why the update was not included. If an update was used in modified form,' provide this information and briefly state why it was . j modified. This information is needed to verify that all known errors in the l RELAP5/M001 base code have been corrected in NULAP5. This must be verified -

before licensing approval of NULAPS can be given.

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9. Northeast Utilities stated in response to question Q.IX.9 that the heat transfer coefficient calculated by the no-return to nucleate boiling logic would be limited to a maximum of 10,000 W/m 2 -K (1761 Stu/hr-ft2.op) based on the maximum post-CHF heat transfer coefficient calculated during an assessment of post-CHF heat transfer regimes. It was also stated that this would result in the calculation of conservative heat transfer _ coefficients by the no-return logic wheh compared to nucleate boiling heat transfer coefficients. However, based on the figure from the next page, which was taken from Reference 6, this does not always seem to be the case. This is because nucleate boiling heat transfer coeffic,ients in the temperature difference range from 10 to 20*F fall below the value selected to limit the heat transfer coefficient calculated by the no-return logic. Provide additional information to demonstrate the no-return logic will yield conservative heat trarsfer coefficients relative to the nucleate boiling regime.

10. Northeast Utilities stated in response to question Q.X.11 that the fuel rod temperature increase terminated at the same time the core two phase level went to zero because the code calculated a transition to mist flow in the core and increased steam volocities in the core during the loop seal clearing process enhanced the cooling of the rods. While this may be what NULAP5 calculated to occur, it is the staff opinion that these phenomena are not real and that the rod hot spot at the top of the core should be heating '

up during the period when the two-phase and collapsed levels are at the bottom of the core. The calculated results for the analyses forming -the basis of question Q.X.11, the 0.1 ft2 discharge leg break with the pumps off and the 0.02 ft2 discharge leg break with the pumps off, should be reviewed in detail to check for the possible calculation of non-physical j phenomena and results. Areas reviewed should, at a minimum, include the ,

interphase drag models, flow regime maps, and heat transfer logic. The -

results of this study should be provided to the NRC for review. .

o EE.T ( ORsM , ,

He9er Mo me P 4 d r-* A Wst. ',

MEAT TMMSFan ItY cONvECTnsN CoNDaNsATioK AND EvAcoltAttorf 31">

i angle if depemt< on the relative magnitude of the different surfare iions. It may be smaller or larger tlum 'nf. In the lint cw the move easily and accurately from a pressure measurement. It is, there- '

fore, more frequently used. The difference between both tran$fer id is said to vvf the surface. When Ihe nuale d i, larger than mf, the cee is considered to be nonisclied. It is frequently a*umed that a coeffierents L., hy the way, small. This hecumes evident fruen 'is.12 4 Figure 12-9 presents heat-transfer coefficients (according to the second

. vapor film exista between a lieguid and a solid nonwetted surface even dennition) measured in pool Imiling with net evaporation 6 water at 3 boiling occurs. It in unelerstandable that the condition of s.urface atmonpheric prea=ure. It can be olnerved that the heat. transfer coeffi-tig is of great lofluence les bubble formation. cientinerenaris at first at a moderate rate with & temperature difference

~ .han been found that a surface initially requires a smaller temperature M. At approximately M - 10 F, the rate of incream becomes conader-vence to transmit a certain amotmt of heat into the hoiling fluid and i

. the required temperature difference gradually ir. creases with time. ably,, larger until at approximately M = in F, a maximum e,, is ra

, maanmed that the gases which originally were adsorbed at the actface fppffeggy , j ,

itate tha bubble formation until they are gradually removed with the p . ,,,,,,,,, g -.., ., 7 bles. The considerationc discusied make it underdandable that the gooo g ag,, , fjm,,, _

Jp ,f;

.netracture of the surface as well as its condition as far as impuritics gooo -- = m.i.si,8 JAwspes

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dsorbed gas films are concerned have a considerable influence on boil- 4,oo, . _ ' 8'** 8 parer i n ff 4~

8 F#ar*ar i On the other hand, the shape of the surface should be of minor zooo --- l ,8'** ,

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' artance, since the thickness of h thermal boundary layer on the goo, -

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y [, gaps , , e .

ace is in most cases determined by the stirring action of the bubbles, g ~

ocess concentrated in a comparatively small space. The growth and 5

f,,, _ ff %g$ g i y, p

ration of a bubble from the surface are also more complicated proc- soo

- 7(*' L.

i .han hee incide a liquid, since the bubble crows into a boundary r  % a steep temperature gradient. It is also probable that the soo 4o0 -

, dz -

/

g- c p"

4 p7 J y

.r: of the Imbble is influenced by inertia forces, especially at high .,m

.ses which cause a rapid growth rate and at higher pressures. ,,,

wrations by Ellion' demandrate this, since they show that bubbles A --

.,copelled into the fluid with considerable velocity from the under6de ,,, ,

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horisontal, elettrically heated ribben. The complexity of this prob. so g,-e Z i Ims ut, to now prevented a sat:sfactory analytical formulation. 80 u

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• hall now consider the heat-transfer process conieected with boiling, o,f f34 8s, t J4 s s, j s ., , , ,,g g f ise 12-6 indicates that the brmal registance in the evaporatiod af, g je. ** d.

i ens la concentrated essentislly in a thin thermal boundary layer at i reu.12.a 11 t.tr re, r ne;,oi, f , ,,,,, i,oihng herineni.I toi,. g.i> .na nested surface. Attention nust, therefore, be Exed upon this regic i hanarmtal r8e'ee (8 nad c)at t aim. (re u.n.uc.i,r.=a,anceTre. i i..,-

j f boibg bat exchange 8& #& AI&'**-Hm B'*k C'"P**8' #" # l'erl,19t2.)

no de6aitions ase found in the literatute for a film heat-transfer Beyond this value of M the heat-transfer coefficient drops off. hfensure.

Icient in boiling. In one of them, the heat flux q at h heating mir- ments which extended the temnerature difference beyrmd the range pre-i is divided by the P= --- ^* b' =-- "P

• R " "" ""a sented in Fig.12-9 showed ht the heat-transfer coeflicient reaches a g,..: . _...w_=_ .== in the E_"".re in the The "a"L8 mmimum at a M of approximately 200 F and then starta rising again.

< r definition uses the difference between the surface tempervure and Visual observation provided h explanation for this peculiar behavior.

I Suid bulk ternperature. This last definitioni agrees better with the It could be observed that in h region 0 <. M < 10 F bubbles occur only

. eustosnarily used in convection without change of phase. The first on a few selectal apots of the heating surface and riso in widely separated

! saa the advantage in that the saturation temperatute enn he obtained columns. It was reasonod by 141. Jakob that the small nmuher of Imbides een have only a minor innuence on heat transfer and that the heat-

f. F HEon, Ph.D. timals, Cn!Isornia Inseitete of Technoloc,1911. transfer coefficient should be determined mainly by the free convection i

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ns strer tuANarEu DT CONYECTidf COMDMsATioN AND EVAronNri'"**

. in the liquid by the temperature differences. Ev:poration in s and with it ate are reachal. A r. light inert .f the helt i ts is, therefore, called frre.comection boiling. The numbec of spots beyond this value, however, maken the temperature rise until a : -

on which bubbles start becomes larger with increasing Af. and at a tem- equilibrium condition alightly above point. C is establiehed.

• perature difference beyond of == 10 F the heating surface is so densely corresponding temperature difference ear is usually no high that l

populated with bubbles that their separation should cause a considerable temperature of the heating surface is beyond the melting point of rr l stirring setion in the fluid which increases the heat transfer. This is con- rnetals, in which case the surface is dentroyed. Point B is therel sidered the reason for the steeper increase of the heat-transfer coefficient referred to as burnouf point. The trend to use high ly at fluxes causes in the reaion 10 F < at < 40 F which is referred to as nucleafe boilino engineer to design equipment so that it operates close to the burn For the temperature region beyond 200 F in which the heat-transfer point, and the exact knowledge of this point ham, therefore, great engine coef5cient rises again with incremaing temperature difference, the evapo- ing importance.

ratio i rate has become so high that a continuous vapor blanket covers the If the assumption is correct that heat transfer in the free.comect surface and the vapor bubblea grow out of this blanket. Hoiling in this boiling reginn is determined by the free. convection currenta in the liqi region is called flat boiling. The low coinluetivity of the vapor film then it must be possible to calculate the heat-transfer coemeient in I through which the heat most be transportal explains the lower values of region by relations of the form the heat-transfer coefficient for this region. At the highest temperature differences the energ; transport is increased ley radiatiuti. The fart that K u = ftG,Ps) (12-a vapor film covers the henting nurf ace at high In-st 11uses han been known describ.ing free-convect. ion heat transfer. The vihape of the funct.io for n considerable time. Each reader han probably innde the observation will depend on the geonietry of the heating surface. M. Jakobi that whe.1 a dmp of water in sprayed onto a glowing surface, it does not demonstrated that the known relations for iree convection currelate me touch the surface but fionta on a vapor film and that the druplet, taken a ured hentetransfer coeffietents for free-convectmn bolhng satisf actori13 considerable time to evaporate. This in called the Leidenfrost effect In the nisclease heiling region it has been assumed that the stirr becanne it was reported and explained by Leidenfrost in 1756. The action of the bubbles is the determialns factor for the heat-tram range in F < at < 200 F in which the heat-transfer coefficient decreanes promes. This annumption was supporied by experiments by F with inerensing temperature difference is a transition region in which part Cunther and F. Kreith'in which it was found that the bubbles left -

of the surface is envered by bubbles and part by a film. Evaporation in surface with velocWes up to 15 fps In addibon, it has been establist this region is referred to as transition boiling or parfiof ffm imiling, that the major port,on i of the heat flows in this region from the heat The heat flow q per unit surface sudace mto the hquid and from there mto the vapor bubbles. T area and unit time can be deter. '""*"* II'"' O' " * *" "

• I'** "

• e mined Irom Fig.12-9 by multiply- connidered as one by forceil ennvet.""'

k ion m a h.ipud where the converti

"'E ' ***#""

ing the heat.tinmfei cucifie lent S - - - - -

! d-- with the temper ..ae difference af.

is supplied by the movement of the bubbles and that the hear trans coeft eient should be described by a relation of the form Nu - f(Re,P When this is uone, it is found f that, m the temperature range Recent attempts at a theoretical treatment of heat transfer in nucles

, y, _,,_ . u . . .  :

, , g ,,,,, , a _ %

s - --. , an n s ya e onn u a.~s.

• n . .-

action by the growth of the bubbles.*

• The convection will, howev

{ g also drops w.th i .in creas.mg af.' ~As a no depend on the number of bubbles generated per unit time and u I i illustrated in Fig.12-10, this has- surface area, and the connection of this value with the microstructure '

'

• an important consequence in en- the surface makes its prediction difficult. Semiempirical correlatid Fm.12-te. limt finn g for hobg se E" "E "EE"## ' " " have been presented by Rohoenow* and by Forster and Zuber.' Bott funct' son of irmpermiitre differeam Af.

of $hme the heat flow g? ." "the quantity which is controlled. Let g % ,,g .g.g .. John wiler a isons, Inc New York.1949.

us nasume that the heat flux is adjusted to the value qA in Fig.12-10.

• F. c. Cunti er anil F. Kreith, IIce: Tran.rce and Muid Mechaniemi Institute The difference between the temperature of the heating surface and that <> ner w er, cent., m n of the lieuid is at 4. When, now, the heat flux is gradually increased, a W. M. hhsenow. Trene. .tSJf R,14.% 0952L

• II. K. I'ornier and N. Zeber. . tin. InsL CArm. Kapre. J.1:Sil-535 (1955).

then the temper'ature' c'lifferer. 2 at rises stendily until the value is

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11. Question 4 of the additional questions submitted to Northeast Utilities at the February 3,4, 1987 meeting with the NRC asked how application of the return to nucleate boiling lockout and the fuel behavior models to only the hot channel in the core met Appendix K requirements I.A.5 and I.B.

Northeist Utilities' answer to question 4 requested clarification from the NRC staff on the Appendix K requirements concerning the application of these models to the average core channel in the Haddam Neck plant model for SBLOCA licensing analyses. The stsff opinion is that these models should be applied to both the average and hot core channels in order to meet Appendix K requirements I.A.5 and I.8 unless it can be shown that applying these models only to the hot channel would be conservative. Therefore, to resolve this issue, Northeast Utilities must apply the nucleate boiling lockout and the fuel behavior models to both the average and hot core channels or provide for review sufficient information to show that applying these models to only the hot channel is conservative.

REFERENCES

1. W. G. Kennedy, et al., pump Two-Phase Performance procram, Volumes 1 through 8, EPRI NP-1556, September 1980.

2. V. H. Ransom, et al., RELAP5/ MOD 2 Code Manual. Vol. 1, NUREG/CR-4312, EGG-2396, August 1985.

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3. V. H. Ransom, et al., RELAP5/M001 Code Manual. Vol. I and 2, NUREG/CR-1826. EGG-2070, March 1982. - . .

li li 4. Letter E. J. Mroczka, CYAPCO, to NRC, "Haddam Neck Plant Response to l Requests of Additional Information on NULAPS," Docket No. 50-213 March 19, 1987.

5. Letter P. D. Wheatley, INEL, to S. Sun, NRC, " Questions Resulting from l the Review of NULAPS," PDW-12-86, December 12, 1986.

6. Eckert and Drake, Heat and Mass Transfer, 1959.

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