OECD Transient Benchmarks: Preliminary Tinte Results TINTE Preliminary Results

Transcription

1 OECD Transient Benchmarks: Preliminary Tinte Results

2 Presentation Overview The use of Tinte at PBMR Tinte code capabilities and overview Preliminary Tinte benchmark results (cases1-6)

3 The use of Tinte at PBMR (1) TINTE (Time Dependent Neutronics and Temperatures) is mainly used to model time-dependent transient events that can occur at PBMR. These events can be slow (DLOFC over 24 hours, Xenon oscillations over a few days), or fast (single CR ejection over 1 second). Normal operation (steady state and load follows), as well as a wide variety of design and beyond design scenarios can be modeled with Tinte Tinte provides transient temperature data for core component design and design limits (fuel, reflectors, CR, SAS, etc) SAR analyses (DLOFC / PLOFC, CR transients, SSE, etc)

4 The use of Tinte at PBMR (2) Tinte advantages: 1. Relatively fast (e.g. 72 hours DLOFC real time in 40 minutes CPU time, 5 days Xenon oscillation in 4 hours) 2. Accurate neutronic and thermal hydraulic solvers (2 neutron energy groups in 2 spatial dimensions) 3. Explicit time-dependence modeling of complex components (burst discs, ROMO model for CR movement) 4. One of very few HTGR codes worldwide that can perform timedependent coupled neutronic, thermal hydraulic and chemical interactions, e.g. air/water ingress into an operating reactor Tinte restrictions: 1. Limited secondary system modeling capabilities 2. Azimuthal dependence not currently possible (r-z only)

5 Basic Code Structure of Tinte Tinte consists of 5 main modules, coded as more than 50 subroutines: Control Module Neutronics Module Temperature Module Fluid-Dynamics Module Corrosion Module

6 The Tinte Neutronics Module 2-D r-z, time-dependent neutron diffusion equations, with coarse mesh finite difference solver 1-D leakage iteration method on fine mesh: transverse leakage coupling of radial and axial fluxes and currents 2 Neutron energy groups (3.07 ev thermal cut-off) and neutron XS data, created from MUPO XS library and coupling with VSOP Fuel element burn-up history (for calculation of decay heat) and spatial isotopic distribution are supplied by VSOP. Coupling with VSOP is via interface codes that also prepare the Tinte XS polynomials and reference XS sets. 6 Groups of delayed neutrons Local and non-local heat deposition Time-dependent Iodine-Xenon dynamics

7 The Tinte Temperature Module 2-D r-z heat transport Gas and solid temperatures calculated seperately from neutronic power in subroutines FE surface temperatures from the effective heat conductivity in pebble-bed and convective heat transport Fuel element burn-up history (for calculation of isotopic decay heat) supplied by VSOP Volume heat transfer from solid to cooling gas Convective heat transport in cooling gas

8 The Tinte Fluid Flow Module Calculation of pressure fields using simplified continuity-, momentum- and energy equations (Navier-Stokes) Mass flow from pressure gradient Calculation of natural or forced convection Calculation of gas mixtures possible Simulation of primary loop by a network of 1-D nodes. Secondary loop only possible in simple approximations.

9 TINTE Benchmarks and Applications Tinte has been used for the following applications: Transient analysis of the HTR-MODUL plant Water and air ingress into the AVR and HTR MODUL designs At PBMR: DLOFC and PLOFC, TCRW, load follow, Xenon oscillations, cold helium inlet injections, eartquake (bed compaction) events Benchmarks with CFD and Flownex codes

10 Preliminary Tinte Results: Case 1 Case 1: DLOFC without Scram All convective heat transfer disabled at t=0 sec. (This is a faster option in Tinte than doing the explicit 1 bar DLOFC event). No scram was used reactor will go re-critical (example shown). Increase in maximum fuel temperature from 1058 o C to 1573 o 34 hrs, and average fuel temperature from 760 o C to 1138 o C. Maxiumum steady-state delta over fuel sphere (i.e. T max T surface ): 300 o C. Decay heat of 1.4 MW generated at t=100 hrs.

11 Tem perature (C) Case 1: DLOFC without Scram event Maximum and average fuel temperatures Time (hrs) Ave. Core temp. Max. Core temp.

12 DLOFC without Scram example Maximum temperature for PBMR 400 design Tem perature (C ) Time (hrs)

13 Fission p ower (% ) DLOFC without Scram example Re-criticality phase for PBMR 400 design Time (hrs)

14 Case 1: DLOFC without Scram event Total and decay power in first 600 seconds Pow er (MW) Time (sec) Total pow er Decay heat (MW)

15 Case 1: DLOFC without Scram event Fuel centre and surface spatial temperature difference at t=0 sec r/z (cm)

16 Preliminary Tinte Results: Case 2 Case 2: DLOFC with Scram Identical to Case 1, except for the insertion of all Control Rods at t=13 seconds. Insertion causes slightly lower temperatures than Case 1: Increase in maximum fuel temperature for case 2 from 1058 o C to 1553 o 35 hrs (20 o C lower than Case 1), and average fuel temperature from 760 o C to 1133 o C (5 o C lower than Case 1).

17 Tem perature (C) Maximum and average fuel temperatures - Case 1 and Case 2 compared Time (hrs) Ave Core temp: Case 1 Max Core temp: Case 1 Ave Core temp: Case 2 Max Core temp: Case 2

18 Total and decay power in first 600 seconds - Case 1 and Case 2 compared Power (MW) Time (sec) Total pow er: case 1 Decay heat: case 1 Total pow er: case 2 Decay heat: case 2

19 Preliminary Tinte Results: Case 3 Case 3: PLOFC with Scram Identical to Case 2 (DLOFC with Scram), except for reactor inlet pressure kept constant at 60 bar, from t=13 seconds onwards. Larger gas inventory available results in increased heat transfer by natural convection: fuel temperatures lower than DLOFC cases, and the maximum values are reached earlier. Increase in maximum fuel temperature from 1058 o C to 1300 o 25 hrs, and average fuel temperature from 760 o C to 1055 o C.

20 Tem perature (C) Case 3: PLOFC with Scram Maximum and average fuel temperatures, compared with Case Time (hrs) Ave Core temp: Case 3 Max Core temp: Case 3 Ave Core temp: Case 2 Max Core temp: Case 2

21 Preliminary Tinte Results: Case 4 Case 4: % Load Follow PBMR load follow from 100% power to 40% power and back again simulated with decrease in mass flow rate and power. 100% to 40% at t=0 sec, over 8 seconds. This state is held until t=6 hours, when power is returned to 100%. Small variations in maximum and average fuel temperatures: from 1058 o C to 934 o C and average fuel temperature from 760 o C to 856 o C. Main purpose was calculation of Xenon dynamic reactivity effect (sample plots).

22 Case 4: Load Follow Fission power and Xenon absorption levels Total pow er (% ) Core average Xenon absorption (% of total absorptions) Time (hrs) P-FISS./% XE-135-AB/%

23 Case 4: Load Follow Fission power and reactivity behavior Total power (%) Reactivity (% ) Time (hrs) Fission Pow er Reactivity (%)

24 Case 4: Load Follow Fission power and fuel temperatures Tem perature (C) Fission Power (%) Time (hrs) Max f uel temp Avg mod temp Avg fuel temp Fission Pow er

25 Case 4: Load Follow Relative Xenon concentration in top (z=125 cm) and bottom (z=825) areas of core 1.60 Relative Xenon concnetration (to steady-state values) Time (hrs) r=109, z=125 r=109, z=825

26 Preliminary Tinte Results: Case 5 Case 5a: Total Control Withdrawal Withdrawal of all 24 Control Rods in 200 seconds. At this stage only PBMR400 design results available (no benchmark results). Case 5b: Total Control Rod Ejection Ejection of all 24 Control Rods in 0.1 seconds. Focus in this event on data from the first 100 seconds. Doppler feedback limits fission power increase. Benchmark results not satisfactory at this stage- further investigation needed into implementation of neutron lifetime and velocity data. Sample data from PBMR400 design also shown.

27 Case 5a: Slow CR withdrawal example Temperature and fission power increases for PBMR 400 design Max fuel temp Rod withdraw over 202 sec Fission power Time (sec) 100 Max Fuel Temp ( C ) Fission Power (%)

28 Case 5b: Fast CR ejection Temperature increases Tem perature (C) Time (s) Max f uel temp Avg moderator temp Avg fuel temp Outlet temperature

29 Case 5b: Fast CR ejection Fission power comparison between benchmark and design cases Pow er (% ) Time (s) Case 5 fission pow er PBMR 400 Fission pow er

30 Case 5b: Fast CR ejection Max Fuel temperature comparison between benchmark and design cases Tem perature (C) Time (s) Max fuel temp: Case 5 Max fuel temp: PBMR400

31 Preliminary Tinte Results: Case 6 Case 6: Overcooling event Helium gas temperature at reactor inlet decreases 50 o C in first 10 seconds; from 500 o C to 450 o C. Colder temperature kept constant for 300 seconds, then increased back to 500 o C again. Increase in reactor power to 444 MW (111%) during first 5 minutes due to colder gas. Average and maximum fuel temperatures vary within bands of 5 o C and 25 o C during this event, respectively. (Max fuel temp from 1058 o C to 1082 o C, average fuel temp from 760 o C to 765 o C).

32 Case 6: Overcooling event Fission power, maximum and average fuel temperatures Temperature (C) Fission Power (%) Time (min) Max Fuel temp Avg Fuel temp Fission pow er (%)

33 Conclusions Basic implementation demonstrated in Tinte Typical behavior of TH phenomena well represented. Some temperature oscillations (PLOFC) need further investigation. TH correlations vs constant thermal conductivity and specific heat Neutronic kinetic parameters 1/v parameters units to be corrected. Final test on neutron lifetimes and Betas to be performed. Kappas not yet implemented. Neutronic behavior Lack of re-criticality in DLOFC to be investigated. Fission power spike (CR Ejection) amplitude lower than expected. Benchmark definition must be adjusted to show expected PBMR design behavior.