ML19275A036
| ML19275A036 | |
| Person / Time | |
|---|---|
| Issue date: | 08/02/1979 |
| From: | Zuber N NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Chen P, Fabic S, Shotkin L Office of Nuclear Reactor Regulation, NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| NUDOCS 7908300591 | |
| Download: ML19275A036 (14) | |
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E WASHINGTON, D. C. 20555 AUGc 2 3979 Those On The Attached List
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Gentlemen:
The next meeting of the Advanced Code Review Group will take place on September 5 and 5,1979 in Room 106, NRC Willste Building, Silver Spring, Maryland.
In response to repeated requests made by several consultants, the forth-coming ACRG meeting will deal primarily with the " physics" in the TRAC-P1 A code. The objectives of the meeting are therefore:
- 1) To determine whether the current thennohydraulic models in TRAC-PlA require modification, and
- 2) To determine whether additional effects are of sufficient importance, for system analysis, to require inclusion in future versions of TRAC.
The agenda of the meeting is enclosed; it follows the format outlined by the questionaire in Attachment 1.
The latter was prepared by S. Fabic in order to facilitate the assessment of current models as well as to help in following the progress and improvements made in future versions of TRAC.
The justification of all models and relations used in the TRAC-P series will have to be made eventually by LASL. However, in order to alleviate the present heavy work load at LASL, S. Fabic has asked BNL also to prepare answers to the questions listed in Attachment 1.
Since BNL's role in the independent assessment of TRAC, is directed at examining the treatment of basic thennohydraulic phenomena, this request will help BNL as well as the members and consultants of the ACRG, in the review and assessment process.
BNL's answers to the Attachment I questions, will be distributed as the time of the meeting.
In addition to the modeling in TRAC-PlA, the meeting will be addressed also to questions raised during the ACRG January 1979, session. Some of these questions were concerned with the fast running version of TRAC (see Attach-ment II) the others' with problems listed in Attachment III.
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Those On The Attached List With so many important topics to be discussed, the forthcoming meeting should be a fruitful one. We are therefore looking forward to your active participation and contributions.
Sincerely, N.
W N. Zuber, Chainnan Advanced Code Review Group Division of Reactor Safety Research
Enclosures:
as stated 2031 220 e
Addressees for Letter Dated S. Fabic, NRC/RES L. Shotkin, NRC/RES P. Y. Chen, NRC/NRR C. Graves, NRC/NRR P. Norian, NRC/NRR g
F. Odar, NRC/NRR L. J. Agee, EPRI S. G. Bankoff, NW G. Birkhoff, HU G. Carrier, HU P. Chambre, UCB P. Griffith, MIT R. T. Lahey, RPI P. Lax, NYU S. Levy, SLI F. Marble, CIT K. Miller, UCB V. E. Schrock, UCB C. Truesdell, JHU I. Catton, NRC/ACRS A. E. Dukler, NRC/ACRS T. Theofanous, NRC/ACRS F. Aguilar, B&W J. Betancourt, CE G. Dix, GE J. O. Cermak, W J. F. Jackson,' LASL W. Ka to, BNL M. Berman, Sandia J.
Dearien,
EG&G P. North, EG&G
Agenda September 5,1979 8:30 - 9:00 a.m.
Overview of Current TRAC Development Program and g
Activities LASL 9:00 - 9:30 a.m.
Status of Problems Discussed at the January 1979 Meeting of ACRG (see Attachment III).
LASL 9:30 - 12:00 p.m.
Answers to Questions Raised at the January 1979 Meeting of ACRG Concerning the Simplified, Fast, Running TRAC (see Attachment II).
12:00 - 1:00 p.m.
Lunch Thermo-Hydraulic Models in Vessel Module of TRAC P1A (see Attachment I).
LASL 1:00 = 1:30 p.m.
Flow Regime Recognition Criteria 1:30 - 2:15 p.m.
Liquid / Vapor Mass Exchange Models 2:15 - 3:00 p.m.
Liquid / Vapor Momentum Exchange Models 3:00 - 3:30 p.m.
Solid to Fluiu Momentum Exchange Models 3:30 - 3:45 p.m.
Liquid Entrainment and Depc.ition 3:45 - 4:00 p.m.,
CCFL and Liquid Fallback at the Core Support Plate 4:00 - 4:45 p.m.
Energy Transfer between Liquid and Vapor Fields 4:45 - 5:30 p.m.
Energy Transfer between Solids and Fluid 203i 122
September 6, 1979 Thermo-Hydraulic Models in Loop Components of s
TRAC PlA (see Attachment I)
LASL 8:30 - 9:00 a.m. Flow Regime Recognition Criteria 9:00 - 9:45 a.m. Liquid / Vapor Mass Exchange Models and Noncondensible Gas 9:45 - 10:15 a.m. Liquid / Vapor Momentum Exchange Models 10:15 - 10:45 a.m. Solid to Fluid Momentum Exchange Model 10:45 - 11:00 a.m. Liquid Entrainment and Deposition Model 11:00 - 11:15 a.m. CCFL 11:15 - 12:00 p.m. Liquid / Vapor Energy Transfer Model 12:00 - 1:00 p.m. Lunch 1:00 -
2:00 p.m. Solid to Fluid Energy Transfer Models 2:00 -
5:00 p.m. Discussion 2031 223 e
Attachment I List sf Questions Concerning the Basic Thermo-Hydraulic Models in TRAC code.
Part A: Liquic'! Vapor and Fluid / Solids Interactions in Vestel Modole of TRAC.
Pari 0: 1.iquid/ Vapor end Fluid / Solids Interactions in other System Components.
Detailed an:,urs are requested to all questions that are relevant to the TRAC-PlO code released a the public during the first half of calendar yeat 1979.
In, future answers to similar questions, related to future versions of TRAC, please indicate either "no change" or give details of the changes tr.ade.
The Advanced Code Review Group may recommerH changes to this questionnsire since not all of the listed effects may be thought important enough to require their consideration in the systems code. However, in the first iteration, en TRAC-P1 A, answers to all questions 3re urged.
At the end of each section in Parts A and B, describe, wherever possible, the dato base used in fortnulating models and assigning coefficients.
Indicate the range of applicability and discuss limitations and uncertainties.
A.
LIQUID / VAPOR AND FLUID / SOLIDS INTERACTIONS IF VESSEL MODULE OF TRAC.....
1.0 Flow Regirre Recognition Criteria.
1.1 Describe General Criteria 1.2 Describe specific criteria, if such exist in code, for:
Vessel Region Regime of LOCA Very low flows as in (Blowdown, Refill, Reflood)
Small Breaks Downcomer Lower Plenum Core Upper Plenum
- Enter "No" when spe:ific criteria are not used. Otherwise indicate subsection number where the criteria are described in this document.
1.3 Describe how transition is handhd in the code between adjacent flow regimes.
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e, 2.0 Liquid / Vapor Mass Exchange Models. Also Source / Sink Terins for Non-Condensible Gas.
2.1 Describe (a) Evaporation Model(s)
(b) Condensation Model(s) 2.2 How are they related to general flow regime criteria?
2.3 How are they related to specific flow regime criteria indicated in Table on pg.1, or any other criteria?
2.4 How related to flow magnitude (turbulence level)?
2.5 Describe models for source and sink terins for noncondensible gas, where applicable.
2.6 Do mass exchange models account for the presence of (a) solids (nucleation sites), (b) noncondensible gas, and how?
2.7 Are nucleation delays or superheat thresholds handled?
3.0 Liquid / Vapor Mpmentum Exchange Models 3.1 Describe the models for momentum exchange at liquid / vapor or liquid / gas interfaces, as functions of generalized flow regime map.
3.2 As functions of specific flow regime criteria related to vessel region and/or regime of LOCA and/or very low flows (small break).
3.3 Are they functions of flow orientation (upflow, downflow, lateral ar1/or inclined flow)? If so give details.
4.0 Solids (Walls or Embedded Hardware) to Fluid Momentum Exchange Models 4.1 Describe models as function of generalized flow regime map.
4.2 Also as functions of specialized flow regirre criteria if such are employed.
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,, 4.3 Give details of treatment for inclined and lateral flow in reactor core and in Upper Plenum, as functions of flow regime.
How are the form losses calculated and how are friction losses calculated in single and two-phase flow regimes?
4.4 How are two-phase pressure drops calculated for abrupt changes in flow area (e.g. at core inlet and outlet support plates, core grids, junctions between nozzles and vessel plena and/or downcomer)?
4.5 If more than one phase (or fluid component) are adjacent to solids within the same computational cell, how is the momentum exchange partitioned?
4.6 Is the momentum exchange a function of solid's surface temperature (that indicates whether the solid can be wetted by the liquid or not)?
5.0 Liquid Entrainment and Deposition Describe the models if'such are used in the code and indicate dependance on flow orientation, magnitude of absolute ar.J/or relative flow (between liquid and steam), flow path geometry, temperatures, pressure, etc.
6.0 Counter-Current Flow Limitation and Liquid Fallback at the Core Support Plates Give modeling details and, if special, empirically based models are used describe the criteria which trigger their use.
7.0 Energy Transfer Between Liquid and Vapor Fields c
7.1 Describe the models used to obtain heat flux to, or from, the bulk fluid and the liquid / vapor interface within the computational cell.
7.2 Indicate how these are related to the mass exchange moMal(s).
7.3 Indicate how the energy transport models, at interfaces, are related to generalized and/or specialized flow regimes.
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e, 8.0 Energy Transfer Between Solids (Walls, Internal Structure, Fuel Rods) and Fluid 8.1 Describe the models and relate them to flow and heat transfer regimes.
8.2 List all heat transfer regimes considered for the reactor core and indicate if all, or a selected subgroup, are employed for treatment of heat transfer to and from the walls and internal structures.
8.3 Define selection criteria used to identify each heat transfer regime.
8.4 Describe heat transfer correlations for each regime, indicating dependance on flow and fluid state parameters.
8.5 How is heat transfer handled for flow (component) perpendicular to fuel rods?
8.6 In flow regimes where both liquid and vapor are adjacent to solids in the same computational cell, indicate how the energy is partitioned.
Such situations occur, for example, when liquid, or froth, interface is traversing any computational cell containing walls or solid structures.
8.7 Describe model(s) for quench front propagation and indicate if multiple (two or more) quench fronts can be monit red.
8.8 How does the quench front propagation model handle flow reversals and the effects of grid spacers?
B.
LIQUID / VAPOR AND FLUID / SOLID INTERACTIONS IN LOOP COMPONENTS OF TRAC....
1.0 Flow Regime Recognition Criteria 1.1 Describe general criteria 1.2 Describe specific criteria, if such exist, for steam generatnr, pressurizer, horizontal vs. vertical pipes, etc., and if functions of LOCA r'egimes.
Is special treatment being used, and where, for very small break '0CA and for natural circulation (of Reflux Boilertype).
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i
, 1.3 How are transitions handled between flow regimes?
2.0 Liquid / Vapo Mass Exchange Models and Noncondensible Gas Source / Sink Tems 2.1 Describe (a) Evaporation model (b) Condensation model 2.2 How are the evaporation and condensation models related to the flow regime criteria and is special treatment being used for 1'ndividual loop components? If so, please give details.
2.3 Are turbulence effects modeled (either directly or indirectly)?
Any other flow magnitude effects?
2.4 Is the presence of embedded solids and walls taken into account and how?
2.5 Are the effects of noncondensible gas treated and how?
2.6 Is nucleation delay (or incipient superheat) handled, and how?
2.7 How are the mass exchange models related to the interfacial energy exchange models and, where appropriate, to solids / fluid energy exchange models?
2.8 How are sources and sinks for noncondensible gas described (for example, for gas coming out of solution or being forced back into solution)?
3.0 Liquid / Vapor Momentum Exchange Models 3.1 Describe the model(s) and' indicate which is used in what flow regime and whether special treatment is given to some loop components.
3.2 Are the models functions of flow orientation (upflow, downflow, horizontal flow, and counter-current flow) and, if so, give details?
3.3 What steps are taken to prevent smearing of the liquid / vapor interface
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in analysis of small breaks (to assure that (a) proper heat transfer regimes are handled and proper fluid fluxed to nozzles)?
4.0 Walls-to-Fluid Momentum Exchange Models 4.1 Describe models as functions of flow regimes and indicate if any special treatment is given in particular loop components.
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e, 4.2 Describe treatment of two-phase flow pressure drop for flow area expansion, contraction, otifices.
4.3 How is the void fraction distribution handled for flow through Tees, and also for flow into steam generator tubes, in steady and transient flow conditions? If these effects are handled through liquid / vapor momentum exchange models (or through vapor drift models) please indicate these answers in Section 3.0.
4.4 If more than one phase are adjacent to walls within the same computational cell (as during the rise or fall of liquid leul or in stratified flow in the horizontal pipes), how is the wall-to-fit.id momentbm exchange partitioned? This particular question is pertinent to the two-fluid formulation.
5.0 Liquid Entrainment and Deposition Models Is entrainment and deposition of liquid modeled in the code (for loop components) and, if so4 how?
6.0 CCFL Are any special models being used to account for counter-current flow limitation? If so, give details.
7.0 Models for Energy Transfer Between Liquid and Vapor 7.1 Descr'ibe the models and indicate how are they related to flow regimes?
7.2
..sw are they related to interfacial mass transfer models?
8.0 Energy Transfer Between Solids (Walls) and Fluid 8.1 Describe the models and relate them to flow and heat transfer regimes.
8.2 1.ist all heat trsnsfer regimes considered in (a) Steam generator primary and the secondary side, (b) other loop components.
8.3 Define' selection criteria used to identify each heat transfer regime including the S.G. secondary side.
8.4 Describe the heat transfer correlationf that are different from those shown in Part A.
Otherwise indicats that they are the same.
8.5 In flow regimes where both liquid and vapor are adjacent to solids in the same computational cell, indicate how the energy is partitioned.
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Attachment II LASL is in the process of (a) improving the detailed (3-D vessel) version of TRAC - here designated as TRAC-PD2 ("P" stands for PWR, "D" for " detailed"),
and developing a fast running version of TRAC - here designated TRAC-PF1 -
that is not constrained to 3-D description of the reactor vessel region.
g Questions and/or infonnation needs were generated on various aspects related to
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both the detailed and simplified LOCA analyses now under development. The needed infonnation is here organized in a tabular form indicating, via an asterick, where answers are needed. When supplying the answers please bear in mind that the fast running code will also be used for analyses of very small break LOCA and for natural circulation analyses of the " reflux bo.iler" type wherein steam is generated in the core (that may be partially uncovered) and condensed within the steam generator.
Information Needed Simplified, Fast Running Code PWR Vessel description simplifications, including the treatment of Upper Head injection Field equations and the constitutive relationsfor droplet field (s) if such are being considered ji, Details of core quenching treatment including quench front propagation and pre-curso y cooling Liquid separation in upper plenum and fallback through upper core support plate Counter-current flow limitation at the upper -
core support plate Downcomer penetration model for use with 1-D noding of the PWR downcomer Simplified choked flow 203!
230 model 4
2_
It is understood that LASL may not have " frozen" some of the models or concepts that are now under development. Nevertheless, the reviewers would like to see the description of the ideas that are now being pursued so that constructive and helpful feedback could be generated on their part, in timely manner.
LASL's ideas /models and reviewer's feedback will be discussed at the next advanced code review group meeting.
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0 e
a Attachment III During the January 1979 meeting of the Advanced Code Review Group, the review group members and consultants voiced particular concern related to TRAC-PlA treatment of (a) Thermodynamic property routine.
LASL attributed significant mismatches in the calculated vs. measured flow rates and temperature profiles in the 1
LOFT L2-2 test, to possible inaccuracy in the thermodynamic property routine. Other causes, however, could have played a role and, if so, they needed to be identified and resolved.
More recently, BNL has also had difficulties in obtaining some steady-state calculations with TRAC-PIA which were communicated to LASL. The reviewers stressed the need for adequate steady-state calculation. This need will become particularly important for calculation of very small break LOCA and for natural circulation studies. Please indicate if this issue has been resolved, and how.
(b) The reviewers concluded, and LASL agreed, that the fuel rod gap conductance treatment was too crude in TRAC-PlA and recommended speedy removal of this weakness, without resort to full scale integration of the FRAP-T code with TRAC which was thought to lead to severe complexity and running time impact.
Please indicate how this issue is being resolved in TRAC detailed and simplified (fast running) code versions.
(c) Professor Schrock indicated certain inadequacies, and one error, in the treatment of the decay heat.
Please indicate if this issue has been resolved and how.
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