First results and prospects of the IRSN DENOPI program devoted to - PowerPoint PPT Presentation

First results and prospects of the IRSN DENOPI program devoted to Spent Fuel Pool Accidents C. MARQUIE, N. TREGOURES, C. DURIEZ, G. BRILLANT , J. MARTIN IRS[N] / Nuclear Safety Division / Safety Research IRSN/FRM-414 ind 3 MEMBER OF IAEA TM on the Phenomenology, Simulation and modelling of Accidents in SFPs, IAEA Headquarters, Vienna, Austria, 2-5 September 2019

Outline ▪ Elements of context ▪ The DENOPI Project ▪ First results with MEDEA facility ▪ First results on Zy oxidation MEMBER OF IRSN DENOPI Program on SFP – September 2019 2

E LEMENTS OF CONTEXT Fukushima Daiichi Unit 4 SFP-LOCA ▪ On 2011/03/11: 1331 spent fuels - decay heat: 2.26 MWth ▪ Time estimation before fuel assembly dry out without counter- measures: end of March 2011 (0D energy balance) ▪ No clear evidence for boiling, no fuel uncovery ▪ Water temp. ~ 80-90 °C during ~4.5 months ▪ Recovery of active heat removal on 2011/07/31 @ water ~ 75 °C MEMBER OF IRSN DENOPI Program on SFP – September 2019 3

E LEMENTS OF CONTEXT International effort on SFP accidents ▪ IAEA: ▪ International Experts Meeting on Strengthening Research and Development Effectiveness in the Light of the Accident at the Fukushima Daiichi NPP , 2015 ▪ … ▪ OECD: ▪ Status Report on Spent Fuel Pools under Loss- of-Cooling and Loss-of-Coolant Accident Conditions NEA/CSNI/R(2015) ▪ PIRT on SFP (2016/2017): NEA/CSNI/R(2018) ▪ … MEMBER OF IRSN DENOPI Program on SFP – September 2019 4

E LEMENTS OF CONTEXT International effort on SFP accidents ▪ European Community – NUGENIA+: Air-SFP Project (IRSN lead) ▪ WP1: Benchmark of SFP transients with SA codes (PSI coordination) ▪ Task 1.1 Analysis of SFP transients carried out in the frame of a benchmark on SFP geometry similar to Fukushima one ▪ Task 1.2 Investigation of criticality phenomena ▪ WP 2: Roadmap for further R&D on SFP accidents (NRG coordination) MEMBER OF IRSN DENOPI Program on SFP – September 2019 5

T HE DENOPI P ROJECT Overview ▪ Framework: Post-Fukushima project, supported by the French government (ANR 11 – RSNR 006) – 2014/2020 ▪ Participants: IRSN and French academic labs ▪ 3 axis representing three scale of interest and 3 different time frames ▪ Axis 1: Pool scale - Before fuel uncovery ▪ Validation of TH models (convection loops, power distribution effect...) ▪ Axis 2: Assembly scale - Partial or total uncovery of fuel assembly ▪ Spray cooling efficiency as a mitigation measure ▪ Axis 3: Fuel clad scale - Degradation of fuel assembly ▪ Clad oxidation under mix air-vapor atmosphere MEMBER OF IRSN DENOPI Program on SFP – September 2019 6

T HE DENOPI P ROJECT Axis 1 – Pool scale ▪ MIDI facility: A 1/6 th scale pool (except in height 1/3 rd ) - Design based on a similarity approach ▪ 21 heating elements for a max total power of 300 kW – possibility to test different power distributions i.e. different loading patterns ▪ Instrumentation: progressive approach ▪ At first: “ classical ” instrumentation (TC, pressure sensors, flowmeters...) ▪ Progressively: evolution with innovative measurements in the upper volume depending of development and qualification ▪ Construction undergoing MEMBER OF IRSN DENOPI Program on SFP – September 2019 7

T HE DENOPI P ROJECT Axis 2 – Assembly scale ▪ MEDEA facility: A full-scale upper part of a fuel assembly (top meter) in its storage cell ▪ 17x17 unheated rods ▪ Air or steam (up to 200°C) injection from the bottom ▪ Modular water spray at the top (flow, shape and temperature) ▪ Measurement of water progression in the assembly / ejected at the top ▪ Two configurations ▪ Water-air tests ▪ Steam-air tests ▪ All tests performed MEMBER OF IRSN DENOPI Program on SFP – September 2019 8

T HE DENOPI P ROJECT Axis 2 – Assembly scale ▪ ASPIC facility: A full-scale assembly in its storage cell ▪ 17x17 electrically heated rods (T clad < 600°C) ▪ Versatile configurations: no, partial or total uncovering ▪ Water spray at the top ▪ Measurements: Temp., pressure, flowrates and levels ▪ Design studies finalized mid-2017 ▪ Construction undergoing: → 2019 ▪ Tests: 2020-2021 MEMBER OF IRSN DENOPI Program on SFP – September 2019 9

T HE DENOPI P ROJECT Axis 3 – Clad scale ▪ Zy 4 oxidation tests under mixed steam/air atmosphere ▪ Effect of pre-oxide layer ▪ Effect of O 2 /H 2 O/N 2 partial pressures ▪ TGA testing 18 O/Raman tests ▪ ▪ In-situ DRX ▪ Mechanical test ▪ In collaboration with Mines Saint-Etienne, LEPMI and LVEEM MEMBER OF IRSN DENOPI Program on SFP – September 2019 10

F IRST R ESULTS – A XIS 2 – A SSEMBLY S CALE Air/water flooding test on MEDEA Q spray Parameters: ▪ Air inlet and spray flowrates ▪ Spray shape ▪ Distance spray / top of Q up assembly Q air ▪ Cross-section of top nozzle Measures (flooding curves): Q down ▪ Water going through the assembly (Q down ) ▪ Overflow water at the top (Q upo ) ▪ Temperatures (RT), pressures MEMBER OF IRSN DENOPI Program on SFP – September 2019 11

F IRST R ESULTS – A XIS 2 – A SSEMBLY S CALE Conclusion of MEDEA first tests ▪ For typical SFP configuration (low spray / gaz flows), the risk of CCFL is unlikely ▪ But with debris on top of the top nozzle, CCFL is observed even with low flowrates. ▪ Steam tests are under analyses MEMBER OF IRSN DENOPI Program on SFP – September 2019 12

F IRST R ESULTS – A XIS 3 – C LAD S CALE Pre-oxidation effect ▪ Pre-oxidation: Objective to simulate oxide layer formed during operation in reactor PO ~ 30 µm 0.07 850°C Bare Zy4 0.06 d( D m/S)/dt (g m -2 s -1 ) 0.05 0.04 0.03 0.02 0.01 0 0 60 120 180 240 300 time (min) ▪ Protective effect from oxide formed at low temperature ▪ Strongly depend on oxidation conditions: positive effect of steam MEMBER OF IRSN DENOPI Program on SFP – September 2019 13

F IRST R ESULTS – A XIS 3 – C LAD S CALE Effect of steam ▪ Air + steam tests with variation of steam partial pressure 850°C 200 1900 air sec 30hPa H2O Prise de masse (g.m- 2 ) 50hPa H2O ECR HT 44-54% 80hPa H2O D [H] (ppm mass.) 150 1400 100hPa H2O mass gain (g.m -2 ) (wt ppm) 280hPa H2O ECR HT 35-41% 100 900 ECR HT 14-17% 50 400 0 -100 0 200 400 600 800 1000 0 60 120 180 240 P H2O (mb) Temps (min) time (min) ▪ No effect of steam (vs. O 2 ) on oxidation kinetic ▪ But steam contributes to the oxidation : H incorporation in the sample MEMBER OF IRSN DENOPI Program on SFP – September 2019 14

F IRST R ESULTS – A XIS 3 – C LAD S CALE Edge effect ▪ HT oxidation is initiated from edges or defects on the oxide layer (with nitrogen) MEMBER OF IRSN DENOPI Program on SFP – September 2019 15

T HE DENOPI P ROJECT Conclusions ▪ Following the Fukushima Daiichi accident, IRSN launched the DENOPI project with support from French Government (ANR) ▪ First results of the DENOPI projects are available concerning clad oxidation and spray tests (CCFL) ▪ The design studies for the last two devices (ASPIC/MIDI) are finalized ▪ ASPIC and MIDI tests are planned in 2020-2021 ▪ International collaborations with Bel V and US-NRC ▪ Collaboration with EDF MEMBER OF IRSN DENOPI Program on SFP – September 2019 16