SPERT-III: REACTIVITY INSERTION ANALYSIS WITH SIMULATE-3K

Transcription

1 SPERT-III: REACTIVITY INSERTION ANALYSIS WITH SIMULATE-3K Gerardo Grandi 2012 International Users Group Meeting Charlotte, NC, USA May 2-3, 2012

2 2 Overview Introduction Special Power Excursion Reactor Test (SPERT) Analysis Results Maximum reactor power Energy release at time of maximum power Reactivity compensation at time of maximum power Conclusions

3 3 Introduction S3K suitable for reactivity initiated accidents (RIA) Benchmarks Feedback models Validation of CASMO5 and SIMULATE-3K for superprompt RIA

4 4 Special Power Excursion Reactor Test Nuclear research facility constructed to analyze the reactor s kinetic behavior under initial conditions similar to those of commercial LWRs fuel type moderator coolant flow rate system pressure. Initial test conditions cold start-up hot start-up hot standby hot full power

5 5 SPERT-III core Design characteristics Oxide fueled PWR 4.8% enriched UO 2 fuel rods Stainless steel clad Active fuel length is ~ 97 cm. Core diameter is ~ 66 cm. Rated power: 20 MW Rated flow: 1.26 m 3 /s Design pressure: MPa

6 6 SPERT-III core loading Number of fuel assemblies rod assembly rod assembly 4 CR assembly with fuel follower 8 Overall dimensions 25 rod assembly cm 16 rod assembly cm 4 CR assembly cm

7 7 5x5 Fuel assembly

8 8 Control rod fuel assembly with follower

9 9 Transient control rod

10 10 CASMO5 / SIMULATE-3K model Explicit representation of the 60 fuel assemblies 1 node per assembly ( x 7.6 cm.) 52 axial nodes ( z 1.9 cm.) Cruciform rod inserted from core bottom SPERT core was modeled as a BWR core with 3 different fuel types Nuclear data calculated with CASMO5 / ENDFB-VII rev0 Segments were modeled as PWR lattices Option S3C was not used Ad-hoc case matrix at atmospheric pressure

11 11 Cold start up tests Initial conditions All 30 cold start up tests were simulated Atmospheric pressure and room temperature Low initial power and zero mass flow For the purpose of the simulations Initial power: 50 W Flow: ~1 kg/s Initial positions of the four control rods and of the transient control rod were not specified Reactor state (P, T), and initial reactivity insertion were specified Rapid reactivity insertion varying from 0.77$ to 1.21$

12 12 Procedure to perform the S3K calculations Compute the position of the four control rods that make the reactor critical at the given operating conditions (P, T) Determine the position of the transient control rod such that its reactivity worth matches the reported initial reactivity Move the four control rods (with fuel followers) to preserve the criticality in the core The power excursion was initiated by ejecting the transient control rod from the core

13 13 Reactor power and reactivity Super-prompt critical case Reactivity 1.2$

14 14 Initial reactivity insertion and reactor period Sub-prompt critical: inserted reactivity below 0.97$ Reactor period greater than s Tests belong to this category Super-prompt critical: inserted reactivity > 1.03$ Reactor period lower than s Tests belong to this category Critical: inserted reactivity between 0.97$ and 1.03$ Reactor period between s and s Tests belong to this category.

15 15 Maximum reactor power Tests 22 14: reactivity below 0.97$ Tests 39 20: reactivity between $ Tests 75 43: reactivity above 1.03$

16 16 Reactivity compensation at peak power Tests 22 14: reactivity below 0.97$ Tests 39 20: reactivity between $ Tests 75 43: reactivity above 1.03$

17 17 Super-prompt critical cases Initial reactivity

18 18 Super-prompt critical cases Peak power Bias +1.6% Standard deviation of 7.4% Maximum difference 13% Experimental uncertainty 15 %

19 19 Super-prompt critical cases Energy release Bias -7.1% Standard deviation of 3.8% Maximum difference 13% Experimental uncertainty 17 %

20 20 Super-prompt critical cases Reactivity compensation Bias $ Standard deviation of 0.005$ Maximum difference 0.01 $ Experimental uncertainty < 0.02$

21 21 Summary Objective validate CASMO5 / SIMULATE-3K for super-prompt RIA applications feedback models recommended by Studsvik for LWR applications Good agreement with experiments at cold zero power conditions. Differences within experimental uncertainty Future work hot start-up hot standby hot full power

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