ML20062G537

Forwards Request for Addl Info Re Topical Rept XN-NF-78-30 in Order to Complete Review of Reload Conditions.Req Info Should Be Submitted W/In 45 Days

ML20062G537
Person / Time
Site:	Prairie Island
Issue date:	12/19/1978
From:	Ippolito T Office of Nuclear Reactor Regulation
To:	Owsley G SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER
References
NUDOCS 7812290236
Download: ML20062G537 (6)

Text

_ _ _ _

Mc_ ?, X( '. ~

....., N,t

,F e

UNITED STATES V

NUCLEAR REGULATORY COMMISslON g/ O *'

E P V. M%, 'Up/l WASHINCTON, D. C. 20655 U-CECEVIER 1 9 O

/o g$

)

~

6~0' bO

~ *

~

f3 yfu

'[j ('i [) /

Mr. G. F. Owsley, Manager Reload Licensing

/

'l Exxon Nuclear Company, Inc.

P. O. Box 130-Richland, Washington 99352

Dear Mr. Owsley:

We are reviewing Topical Report XN-NF-78-30, " Exxon Nuclear Company WREM-Based Generic PWR ECCS Evaluation Model !);date ENC WREM II-A",

4 August 1978. This code is designed to replace the existing RELAP4-EM/ FLOOD portion of Exxon's approved ENC-WREM-II model which will then be identified as ENC-WREM-IIA.

4 From our review of this topical report to date, several items of additional information are required to assist our review. These items i

are described in the enclosure to this letter. Please provide the requested information described in the enclosure to this letter within I

45 days of your receipt so that we may complete our review of the Prairie Island reload.

Sincerely, f-t

.,f2 cc Thonias A. I ppolito, Chief Operating Reactors Branch #3 Division of Operating Reactors

Enclosure:

Request for Additional Informa tion 1

I 7812290,236 f

i

. ~ _,

_,=

~. _. - _

.a

4

)

RE00EST FOR ADDITIONAL INFORMATION i

Report Number: XN-NF-78-30 Report

Title:

Exxon Nuclear Company WREM-Based Generic PWR ECCS Evaluation Model Update ENC WREM-IIA Report Date: August,1978 Originating Organization: Exxon Nuclear Company The following items of additional information are required to assist the NRC review of the subject topical report. The needed information l

is identified by page number and paragraph where the subject ~in question is discussed initially in the report.

1.

Page 1, First Paragraph Identify the unnecessary calculations in RELAP4-EM/ FLOOD that have been omitted in REFLEX.

i 2.

Page 2, First Paragraph j

Identify the differences in reflood rates computed in the Ginna reflood analysis using RELAP4-EM/ FLOOD and REFLEX, and identify the source of these differences.

3.

Page 3, Table 1.1 f

Provide a discussion presenting the sources of the differences in 3

g PCT between ENC models shown on this table includin~g a graphical l

comparison of core coolant level and PCT transients for each a

plant during reflood.

Identify the break size and discharge coefficient condition selected for the lD.C. Cook plant comparison, and discuss the reason for the reduced PCT shown for D.C. Cook plant when using REELEX.

i I

4 y---

y

-r w

yy-

,w, - -, _... - - -,....

...~,-.-~.nr,

T e

2

' 4.

Page 4, Second Paragraph Describe the functions of the inputs'to REELEX from the T00DEE2 hot assembly and hot pin calculations shown as steps 7 and 8 on Figure 2.1.

I 5.

Page 5, Second Paragraph Justify the use of apriori -tabular input for fills, cr leak flows, and 4

t enthalples which are affected by varying. conditions during LOCA's, 2

and may vary as functions' of break size and location.

6.

Page 6, First Paragraph i

Justify the neglect of elevation terms in the momentum equation when applied to components other than the core and downcomer over the spectrum of breaks analyzed with REFLEX.

t 7.

Page 6, Ecuation 4 I

Discuss the manner by which the average density term in this equation is determined, and justify the use of a single average i

density in both legs of the manometer formed by.the core and l

downcomer.

1 8.

Page 7, First Paragraph i

Justify the use of the loss ccefficient, K, in REFLEX when this-coefficient is determined in the blowdown model calculation for balancing initial flow conditions. What restrictions, if any, are i

placed on an acceptable X value relative to the remaining -terms within the brackets in equation 6 on page 6.

t 4

l i

.~

4 l '

'9.

Page 9, First Paragraph Describe the limitations imposed on combining series nodes into equivalent nodes when leaks, fills, or heat transfer phenomena occur in the uncombined nodes.

10. Page 9, First Full Paragraph Describe the core rodel used for determining energy addition to the j

coolant during reflood. Provide and justify the criteria by which a conservative fixed core outlet enthalpy is selected for use in REFLEX for the reflood calculation.

Describe or reference the sensitivity studies performed to confirm the conservative characterization of the outlet enthalpy selection.

i

11. Pace 11, First Paragraph Provide a complete description of the frictional pressure drop calculation used to compute core pressure drop in the presence of single and two-phase fluids in the core.

12.

Page 11. 3rd Paraaraph Justify the assumption used in the downcomer model that downcomer fluid will be at saturation conditions for the existing downcocer pressure.

13. Page 15, Ecuation 16 Justify the assumption used in the ECC mixing model that injected ECC fluid is at saturation conditions as implied by this equation.

14.

Page 15, Equations 17 and 18 Justify the steam and water separation model imposed by these two equations as part of the ECC mixing model.

i

15. Page 15, Line 13 Justify the assumption of equal friction pressure loss for the two phases in the broken loop cold leg when stratified steam and liquid flow occurs from downcomer overflow.

l

16. Page 15, Equation 19 Provide the derivation of this equation and a definition of the constants -1 and n-1 given ou side of the brackets.

17. Pages 16 and 17, Equations 21 and 24 Justify the use of a fixed coefficient for the exponential term in these equations in view of heat transfer regime and flow rate 4

changes occurring on the primary side of the steam generator during blowdown, and the heat transfer regime cha'nge occurring on the secondary in the latter stage of blowdown.

18. Page 16, Equatiorg 22 and 23 Justify the diflerences in fluid enthalpy used in these equations and identify the enthalpy used in equation 23.

i

~

i l

19.

Page 17, Line 9 I

Justify the assumptien of equal enthalpy changes between steam

]

generator primary and secondary liquids in a given time step.

20. Page 17 and 18 Saturation Properties Ecuations Provide an indication of the errors for each quartile in the range 10 to 100 psia for the saturation properties equations in addition to that given at 50 psia on Table A-1 1

O 5-

21. Page 25, First Paragraph Provide a discussion of the method used for determining the pump locked rotor flow resistance in REFLEX for reflood transient calculations.

22.

Pace 35, Second Paragraph Provide a description of which nodes of the blowdown model on Figure 4.1 are combined to generate the reflood model of Figure 4.4.

23. Page 37, Third Paragraph Provide transient comparisons for the GINNA plant analyses between ENC-WREM-II and IIA for the parameters shown on Figures 4.24 to 4.28.

24. General Model justification for the reflood calculation with REFLEX in ENC WREM-IIA is based in Section 3.0 of the topical report on model compliance with Appendix K of 10 CFR 50, and on comparisons with results conputed with the previously approved RELAP4/Efi/ FLOOD in 2

ENCWREMII.

As compliance to the rule, and comparisons against previous model results do not identify the degree of conservatism contained in computer results with this code, additional justification demon-strating conservatism is required. Comparison studies using REFLEX to predict reflood transients in Semiscale tests S-04-6, and S-07-6, and in the FLECHT Lcw Flooding Rate - Skewed Power experiments will serve to provide this justification. The specific experiments selected by ENC for this comparison should require use of all REFLEX features that will be used in licensing applications.

____._________m_

_ _. - - _ _ _ _ _ _ - _ _ _. _ _ _ _ _ _ - _