Accident-related fuel experiments in Halden --- HRP LOCA Test Series IFA-650

Transcription

1 Accident-related fuel experiments in Halden --- HRP LOCA Test Series IFA-650 TWGFPT Orientation 24 April 2014 W. Wiesenack 1

2 LOCA test overview Issues to be addressed with the HRP LOCA tests Fuel fragmentation, relocation and dispersal Cladding overheating and oxidation due to fuel relocation Secondary transient hydriding near the burst region Release of iodine and caesium Tests carried out (IFA-650 test series) 3 system commissioning and system check test 5 tests with PWR high burnup fuel 4 tests with BWR and high burnup fuel 2 tests with VVER -high burnup fuel 14 LOCA tests in total Sep. 2013: high burnup BWR fuel (IFA ) Balloon without failure 2

3 Commissioning, fresh fuel (useful for code benchmarking) System check-out test with fresh fuel Target PCT ( C) Tests carried out 1, = important test parameters Fuel type PWR PWR PWR VVER BWR PWR PWR VVER BWR BWR BWR Rod ident. V1-515/3 14D/7 V1-515/7 J13 AEB- 070-E4 14D/3 F08/3 J13/3 AEB 072 E4 Span no AEB 072-4C Fuel length (cm) Cycles Burnup (MWd/kgU) Oxide thickness ( m) ~5 < ~ Hydrog., ppm Cladding Dout/thickness (mm) Zry-4/ Zry-4/ Zry-4/ Zry-4/ E110 LK3/L 1.47%Sn 1.47%Sn 1.47%Sn 10.75/ / / / / 0.63 AEB 072-J9 Zry-4 E110 LK3/L LK3/L LK3/L 1.47%Sn 10.75/ Liner ( m) No Yes 100 No No Yes Yes Yes Heat treatment SRA SRA SRA stand. stand. SRA SRA stand. stand. stand. stand. pressure (bar) / / / / /

4 Experimental Single fuel rod in a pressure flask connected to a water loop Low level of nuclear power simulates decay heat Electrical heater surrounding the rod simulates the heat from neighbour rods Rod instrumented with 2 3 clad thermocouples pressure sensor clad elongation detector Thermocouples in the heater Neutron detectors for power distribution 4

5 purification system LOCA loop F 631 P 630 T l VA 6308 HA 6301 VA 6300 VA 6307 PA 6300 VA 6306 spray system HA 6303 VA 6302 VA 6301 P 632 VA 6305 VA 6331 VA 6328 VA 6327 VA 6303 He55 15kW VA 6304 T 630 P 634 P 631 VA 6333 Mon 40 TA6301 VB 606 HA 6302 T 633 VB 605 IFA-650 VA

6 6 Typical response to blow-down and heat-up

7 Fuel relocation Major fuel relocation observed in two experiments burnup > 82 MWd/kg strong fuel fragmentation large burst opening No or only minor relocation observed in the remaining tests burnup 0 72 MWd/kg mainly coarse fuel fragments small to burst opening In the example to the right, if missing fuel moved into the balloon (10 cm), the average mass increase is about 10% and the average packing density is about 55% 7

8 not envisaged Fuel fragmentation test # burnup, MWd/kg balloon strain, % radiography ceramography fragment size coarse coarse coarse coarse coarse & some fine coarse coarse (?) 8

9 Fuel dispersal test # burnup, MWd/kg balloon strain, % ballon area, mm ? 1, fragment size coarse coarse coarse coarse coarse & some fine coarse coarse (?) gamma scan flask bottom HBS width dispersal (qualitative) none none none none some some more nearly none much much more much more 9

10 Fuel relocation and temperature increase TCC3 TCC2 TCH3 TCH2 TCC1 TCH1 Ballooning and fuel relocation can cause the cladding temperature to increase as observed in IFA

11 Cladding oxidation inside IFA-650 experiments aimed at reaching high peak clad temperatures: 5 (1100 C), 7 (1100 C), 9 (1100 C) 11 (1000 C) Only IFA developed a large balloon filled with relocated fuel More inside oxidation close to the balloon 11

12 Pressure drop IFA In some experiments, a slow pressure drop was observed The fuel maintained tight contact with the cladding along a certain length The cracking pattern depends on position 12

13 Hydraulic diameter The concept of hydraulic diameter is used in Halden reactor fuel testing to assess the permeability of high burnup fuel columns In a LOCA test, as long as general cladding distension has not opened the fuel-clad gap, (parts of) the fuel stack will hinder gas flow In this situation, ballooning will be driven by the locally available gas and gas pressure IFA and IFA can be evaluated with respect to gas flow The derived hydraulic diameter (30 35 µm) is typical of high burnup fuel 13

14 HRP LOCA data for FUMAC The IAEA has asked to include IFA-650 LOCA tests in FUMAC Proposed experiments IFA (PWR) challenge the codes ability to render the dynamic (temperature) development IFA (PWR) a «benign» case with very moderate fuel fragmentation and dispersal IFA (VVER) for VVER particiants, even more benign than IFA At its meeting in Korea (3 April 2014), the Halden Programme Group (HPG) was positive to this request 14

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