1) OUTLINE OF CURRENT/ADVANCED V&V

DOMAIN OF SIMULATION FOR SYS TH CODES

	 Precision Objectives

	 Qualitative and Quantitative Accuracy Evaluation



CONSIDERATION OF 116 TH PHENOMENA



SCALING PART OF V&V – RECENT FINDINGS



INDEPENDENT ASSESSMENT & ASSESSMENT OF ASSESSMENT



2) THE MOTIVATION FOR V&V&C



3) THE DEFINITION OF ‘C’  = CONSISTENCY 

	

4) THE ROADMAP FOR V&V&

D'Auria, F.

Lanfredini, M.

English

1) OUTLINE OF CURRENT/ADVANCED V&V
DOMAIN OF SIMULATION FOR SYS TH CODES
	 Precision Objectives
	 Qualitative and Quantitative Accuracy Evaluation

CONSIDERATION OF 116 TH PHENOMENA

SCALING PART OF V&V – RECENT FINDINGS

INDEPENDENT ASSESSMENT & ASSESSMENT OF ASSESSMENT

2) THE MOTIVATION FOR V&V&C

3) THE DEFINITION OF ‘C’  = CONSISTENCY 
	
4) THE ROADMAP FOR V&V&

D'Auria F.

Lanfredini M.

Archivio della Ricerca - Università di Pisa

Panel Session: V&V and more in Nuclear Thermal-Hydraulics F. D’Auria M. Lanfredini University of Pisa DESTEC-GRNSPG Nuclear Research Group in San Piero a Grado (Pisa)- Italy NUTHOS-12 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics  Qingdao (PRC) - Oct. 14-18, 2018 2/29 PREFACE CONNECTION     NUCLEAR TECHNOLOGY & NRS  SYS TH   V & V  1950: NPP designed, no computers, no SYS TH 1960:  Fundamental TH, computers appeared 1970:  Complex TH, numerical codes appeared 1980:   V & V needs, experimental Data Base available 1990:   Uncertainty Methods (UM) appeared, V & V ‘finalized’ (SYS TH words) 2000:   UM, V & V, Best Estimate Plus Uncertainty (BEPU) attempts 2010:   Domain for BEPU   INDUSTRY & REGULATORS ACCEPTANCE NEEDED FOR BEPU V & V   ESSENTIAL  3/29 LIST OF CONTENT 1) OUTLINE OF CURRENT/ADVANCED V&V DOMAIN OF SIMULATION FOR SYS TH CODES   Precision Objectives   Qualitative and Quantitative Accuracy Evaluation  CONSIDERATION OF 116 TH PHENOMENA  SCALING PART OF V&V – RECENT FINDINGS  INDEPENDENT ASSESSMENT & ASSESSMENT OF ASSESSMENT  2) THE MOTIVATION FOR V&V&C  3) THE DEFINITION OF ‘C’  = CONSISTENCY    4) THE ROADMAP FOR V&V&C  IDENTIFICATION                      +  OF KEY TOPICS 4/29 OUTLINE OF CURRENT V&V IDENTIFICATION OF KEY TOPICS   1 of 4  1. Design of system thermal-hydraulic codes: – Domain of simulation  – Precision objective  – Attributes for safety analyses  – Scaling requirements   2. The development of codes implies the consideration of the following elements: – Physical models Fundamental models for thermal-hydraulics Special thermal-hydraulic models   Non-thermal-hydraulic systems (noticeably nuclear fuel and neutron physics) – Numerics – Code implementation    Structure   Programming    Software Quality Engineering – Code assessment strategy within the development process  – Code manual  – Life cycle   Quality Assurance 5/29 OUTLINE OF CURRENT V&V IDENTIFICATION OF KEY TOPICS  2 of 4 3. The following areas form the Verification: – Numerical algorithm and numerical solution    Numerical scheme   Verification matrix for numerical algorithm and solution    Types of verification solutions   Accuracy definition and numerical error estimation    Qualitative    Quantitative  Checklist for review and inspection – Source code   Tools for verification    Portability of the code    Review and inspection  – Development of nodalization 6/29 OUTLINE OF CURRENT V&V IDENTIFICATION OF KEY TOPICS 3 of 4  4. The following areas form the Validation: – Physical laws and closure relations – Validation matrix   Basic tests   Separate Effect Tests    Integral Effect Tests   Large scale experiments   Containment experiments   NPP data   Scaling Code-to-code comparison – Accuracy definition Qualitative Quantitative – Validation report  Assessment of validation – Use of validation for uncertainty Sources of uncertainty – Sensitivity tests – Qualification of nodalization Thresholds of acceptability – User effect – User guidelines 7/29 OUTLINE OF CURRENT V&V IDENTIFICATION OF KEY TOPICS 4 of 4 5. Independent assessment must be connected with code maintenance and improvement: – Independent assessment (meaning of) The matrix Use of sensitivity analyses   Assessment of validation – Maintenance (meaning of)  6. Code application in nuclear technology implies the consideration of the following topics: – Key applications Licensing and V & V    Technology consistent independent assessment matrix   Assessment of an individual calculation   Documents for user qualification – Code application and uncertainty 8/29 NPP FEATURES NEEDS FOR THE  OPERATION & DESIGN THE DBA  ENVELOPE OTHER NEEDS • TH PHENOMENA • OPERATOR TRAINING • SCALING • USER FRIENDLY • ETC. ENTERING THE DIAGRAM IN  THE NEXT SLIDE OUTLINE OF CURRENT V&V DOMAIN OF SIMULATION FOR SYS TH CODES 9/29                              NPP DBA OPERATION MULTI- PHYSICS PHENOMENA SUB-SYSTEMS AND MODULES  RELEVANT ASPECTS        RANGE           OF PARAMETERS I II III IV V SPECIFIC  PLANT  DESIGN TH* NP CH FP GT B&NVFP ME I&C  *definitions   in the text  Example:  TH - pressurizer   emptying  GT - accumulation   in upper head Example:  TH - natural circulation - pump performance  B&NVFP - boron dilution NEEDS CODE FEATURES & CAPABILITIES Nomenclature in next page OUTLINE OF CURRENT V&V DOMAIN OF SIMULATION FOR SYS TH CODES 10/29 OUTLINE OF CURRENT V&V NOMENCLATURE & PRECISION OBJECTIVES The precision objectives shall be fixed in relation to each of the listed disciplines, making reference to:   • Steady state. • Transient at qualitative level. • Transient at quantitative level. Nomenclature / Disciplines of Multi-physics Precision objectives 11/29 OUTLINE OF CURRENT V&V PRECISION OBJECTIVES Acceptance criteria for Nodalization Qualitative Accuracy Quantitative Accuracy – Application of FFTBM 12/29 0.300.590.080.690.190.660.010.160.010.270.530.590.540.750.190.010.480.000.020.150.450.070.000.330.050.480.020.000.360.250.310.270.310.260.280.270.280.300.230.380.280.000.100.200.300.400.500.600.700.800.901.001.10CEA [C25]IRSN [C25]NRI-2 [A20]GRS [A12]KFKI [A20]UPI [R5]NRI-1 [R5]UPC [R5]KINS [R5]TAEK [R5]PSI [TR4]EDO [T97]JNES [TM55]KAERI [M23]Organization's NameGlobal Acceptability Factors & AATOTQaQb(AA)tot1.44Qa , Qb(AA)totResults related to the “acceptability of input deck” are reported in the same diagram as results of “acceptability of calculation results”. OUTLINE OF CURRENT V&V PRECISION OBJECTIVES – Nodalization & Calculation Acceptance 13/29 OUTLINE OF CURRENT V&V CONSIDERATION OF 116 PHENOMENA Excerpt from list of 116 CROSS-LINK WITH  ACCIDENT SCENARIOS  PARAMETERS 14/29 OUTLINE OF CURRENT V&V SCALING 15/29 OUTLINE OF CURRENT V&V INDEPENDENT ASSESSMENT & ASSESSMENT OF ASSESSMENT QUALIFIED CODE USER / USER GROUP (demonstration of) INDEPENDENT ASSESSMENT SENIOR EXPERT (not involved with calculation preparation-outcomes)                     PHENOMENA RTA PARAMETER RANGES  CODE AREAS BASIC TEST SET ITF TESTS NPP TESTS RESULTS & DOCUMENTATION  Each item of code structure is relevant Accuracy evaluation with acceptability thresholds Assessment of validation DBA framework (demonstration of) ASSESSMENT OF ASSESSMENT 16/29 [FLUID  DOM.]TH BALANCEEQS.[SOLID  DOM.]FOURIEREQS.[CORE  DOM.]NK DIFFUSIONEQS.State eqs.Constitutive eqs.Material properties- HT  surface- frictionInterfacialFluid-wall- t i -- flow regimes- virtual mass- etc.  HTCq’’’-a- T- etc.SpecialModelsComponent- Pump- Separator- Etc.Thermal-hydraulics- ‘K’- TPCF- CCFL- Etc.NODALIZATIONBICNPP... Plus Qualification... Plus UncertaintyCV +J approachAveragingI & CBoron & GasTransportChemistryFuelRadiation HTMechanicsOUTLINE OF CURRENT V&V (RESULTING) ATTRIBUTE FOR A SYS TH CODE  (unchanged in 40+ years) 17/29 NUMERICS COMPUTER-COMPILER ISSUES USER CONVENIENCES INPUT - OUTPUT QUALITY ASSURANCE LIFE CYCLE UNCERTAINTY USER EFFECT USER QUALIFICATION MULTI-DISCIPLINARY MULTI-PHYSICS MULTI-SCALE MULTI-ACTORS  CONTEXT SCALING SEVERAL INTERCONNECTED TOPICS  OUTLINE OF CURRENT V&V 18/29 THE MOTIVATION FOR V & V & C Thermal-hydraulic model capabilities are found to lag behind industry needs, requiring innovative ideas and investigations; the following log-frame to be considered:                                                           V&V Capability  Development and Qualification. 1) Accuracy of NTH models lags behind technological needs  DESIGN LEVEL INDUSTRY PROPOSAL FOR NEW RESEARCHES (e.g. spacer grids, CHF margins)    SAFETY LEVEL NC FLOWRATE  (e.g. Max NC flow,  Conditions for flow reversal in SG U-tubes)  PRIORITIZATION OF RESEARCH  NEEDED  (to confirm adequacy of  research strategy and needed V&V)  NOT DONE! (method available)  19/29 THE MOTIVATION FOR V & V & C (showing) NARROW PARAMETER RANGES FOR VALIDATION 2) Inadequate experimental database (EXP-DB) - 1 of 2  X Y REGION where model is expected to be validated  or  validation is needed REGION known to be outside the validation range actual validation regions Trajectory during  transient application 20/29 THE MOTIVATION FOR V & V & C CSNI SETF & ITF  EXP-DB COVERS (<) < 1% parameter ranges / combinations  expected in DBA of WCNR    Situation may be worse looking at 116 TH phenomena. 2) Inadequate experimental database (EXP-DB) - 2 of 2 EXP DB ESSENTIAL FOR VALIDATION, BUT NOT ENOUGH SURROGATE OF EXPERIMENTS  NEEDED 3) Inadequate V & V role: (a) - TPCF   1980 2015 DATA OWNED BY  FONESYS NETWORK 21/29 THE MOTIVATION FOR V & V & C 3) Inadequate V & V role: (b) – CHF & FILM BOIILING 500700900110013001500170020 30 40 50 60 70 80 90 100 110 120Clad Temperature, KTime, sRELAP5 UNIPIATHLET-2M GRSATHLET-drift GRSAPROS VTTMARS KAERISPACE KAERICATHARE3 CEA2015 CURRENT V & V NOT ENOUGH TO IMPROVE MODELING CAPABILITIES NEED TO ENLARGE  THE SCOPE FOR V&V   ‘C’ DATA OWNED BY  FONESYS NETWORK 22/29 THE DEFINITION OF ‘C’ = CONSISTENCY The rudimentary and broad definition for consistency is: ‘Consistency is an activity connected with the development and the qualification of numerical codes which covers topics not considered by current V&V’.   A detailed definition is expected to cover the above issues, to take into account of (fundamental) physical laws even in the absence of experimental evidence, to provide a hint for the development of computational tools and to not contradict the current V&V (rather being complementary to the existing procedures):  . : ‘Consistency aims at filling gaps of V&V in nuclear thermal-hydraulics, with focus:    a) to connect the modeling features and the technological needs,   b) to take into account of the limitations of the experimental database mainly in terms of the space covered by parameter ranges,   c) to streamline the conditions for developing improved capability models’. 23/29 THE DEFINITION OF ‘C’ = CONSISTENCY 24/29 THE ROADMAP FOR V&V&C Step I – THE ELEMENTS (consistent geometry and material properties parameter ranges)  Step II – THE LOGFRAME (cross linking phenomena and models)  Step III – THE REQUIREMENTS (consistency requirements for models)   I) THE ELEMENTS CLASSIFYING SSC FOR CORE, RPV, PS, SS, BOP, AND CONTAINMENT,  (including materials)  IDENTIFYING/CHARACTERIZING N (> 100)  II) THE LOGFRAME  N (geometry-material) ELEMENTS 116 TH PHENOMENA M (a few dozen) MODELS L (a couple dozen) PARAMETERS  CROSSLINKING N-116-M-L III) REQUIREMENTS  …. NEXT SLIDE …. 25/29 THE ROADMAP FOR V&V&C THE REQUIREMENTS FOR [V&V&]C IIIa – General requirements (selected) Any model should be applicable inside the resulting parameters space, i.e. inside and outside the range of validation in relation to which experimental data exist. Outside the range of validation, model predictions should be physically sound (according to the best available information).  Pressure drops at GD for 1 and 2-phase: fluid velocities (from zero to values corresponding to TPCF or to sound speed in both directions) and void fraction (from zero to one) at the minimum section should be independent parameters; the generation of cavitation conditions should be detected (e.g. as a function of subcooling) where necessary.  Each phenomenon shall have at least one associated model. Special models and models forming the set of constitutive equations can be distinguished.  A study of each mathematical function (M-Models) must be performed checking for peaks, valleys and singular points (including cliff-edge effects and\or conditions for bifurcations); the study shall include the derivative(s) of the function, e.g. ϑ(output quantity) / ϑ(input quantity). Continuity shall be demonstrated or discontinuities justified.  Each model shall be checked for zero and negative fluid velocities, different liquid and steam velocities, the full range of pressure and temperature (etc.).   Acceptability criteria, shall be established in relation to each requirement.  26/29 THE ROADMAP FOR V&V&C THE REQUIREMENTS FOR [V&V&]C IIIb – Requirements  for individual TH phenomena (one example)    Topic / Parameters Activity Requirements  Systematic calculations, rows 1-11, varying upstream pressure (p0) and void (a), rows 12-13, varying local pressure drop at pipe inlet, to derive:  1 Liquid and steam velocities (wg, wf) and Slip ratio (S) curves of wg, wf and S at CS A) Demonst rate continuity of functions, derivatives, etc. (Step IIIa, requirement 5.4) 2 B)  Justify differences related to the condition S=1 3 C)  At critical pressure, S must be unity 4 D) Derive and explain differences between wg, wf and sound speed. 5 Supersonic flow downstream the CS values of wf and wg in supersonic conditions E) This must be computed by the model, together with return to subsonic flow. 6 Energy transfer across the CS kinetic and thermal energy values F) Thermal plus kinetic energy a t pipe inlet must be consistent at pipe outlet  7 End of “critical conditions” at CS occurrence of criticality conditions at CS G) Demonstrate that non -critical flowrate ≥ critical flowrate (TPCF) 8 pressure at CS (pcr) H) Demonstrate that if containment  pressure (p co) > p cr, non -critical flowrate occurs 9 Derivative  ϑ(p0-pco) / ϑ(TPCF) derivative in first column I) Demonstrate continuity (or explain discontinuities) 10 Model a reservoir and a containment–blowdown analysis (isolated-ideal system, no structures) entropy of the ‘isolated system’ J) Demonstrate the total entropy increase in the isolated system 11 K) Demonstrate peak pressure in containment not depending upon TPCF 12 Cavitation at pipe inlet pressure along the pipe L) Demonstrate depend ency of TPCF upon subcooling in reservoir  13 M) Demonstrate the possibility of occurrence of TPCF at pipe inlet 27/29 CONCLUSIONS (advanced V&V) • V & V TARGETS DERIVED FROM CODE DEVELOPMENT, NPP FEATURES & DBA ENVELOPE  • THE NODALIZATION IS A TARGET FOR V & V AND A SOURCE OF ERRORS   • ADDRESS THE SCALING ISSUE IS PART OF V & V  • CONNECT INPUT & OUTPUT ERRORS AND ERROR ACCEPTABILITY  • DISTINGUISH, WITHIN THE V & V PROCESS, BETWEEN SENSITIVITY AND UNCERTAINTY AND CONSIDER BOTH  • RECOGNIZE THE NEED OF QUALIFIED USERS FOR V & V, THEN ‘INDEPENDENT ASSESSMENT’ AND ‘ASSESSMENT OF ASSESSMENT’  28/29 CONCLUSIONS (V&V&C) The current V&V proved inadequate for model improvement & the supporting experimental DB for validation covers only a small portion of the parameters space characterizing NPP nominal and transient conditions..  V&V&C is a (large) human-and-financial resource-consuming approach.  Checking the physical validity of the results in a parameter space where experimental data are not available, creating crosslink matrices involving parameters, phenomena, NPP components and models and imposing conditions to the mathematical formulation of models, can be used for a snapshot characterization of the ‘C’ field.   ‘C’ covers both Verification and Validation. V&V&C will have a role in model development while V&V only proves model capabilities.   The change from V&V to V&V&C appears an epochal change in the area of code development and validation,  29/29 MESSAGE  V&V&C IS NOT A TECHNOLOGY BY ITSELF   V&V&C MAY REVEAL  AS  A  MULTIDISCIPLINARY  TASK  V&V&C MUST BE ADAPTED TO ANY TECHNOLOGY 

V&V and more in Nuclear Thermal-Hydraulics

https://arpi.unipi.it/bitstream/11568/941847/1/39-NUTHOS-12_v%26v%26c-2018.pdf

V&V and more in Nuclear Thermal-Hydraulics

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