Bohunice V-2 power plant mixed core licensing and operation experiences Ondrej Grežďo

Transcription

1 operation experiences Ondrej Grežďo TM Vienna, 12/2011

2 Information about our NPP BOHUNICE NPP TYPE: 2 * VVER in operation 2* VVER in decomisioning 1* A-1 in decomisioning 2

3 Contents Why? - Reasons for fuel change How? - Sequence of fuel introduction Operational experiences with mixed zones 3

4 Why? - Reasons for fuel change Economic - outage shortening from 40 to 20 days - lifetime prolongation - from 30 to 50 or 60 years - power increasing from 1375 to 1471 Mwt - number of fuel assemblies minimalization- high active nuclear waste Power increasing and outage shortening increasing energy requirements of loads. Lifetime prolongation resulted in change of loads philosophy (low low neutron leakage loads). 4

5 Why? - lenght of cycles 3.unit Lenght of cycle (FPD-1375 MW) Increased power Finished cycles Future cycles Number of cycle 5

6 Why? - Number of fresh fuel assemblies 3.unit Finished cycles Future cycles Number of fresh fuel assemblies Number of cycles 6

7 Why? - Avg. and maximum burnup and fresh fuel consuption 3. and 4.unit 7

8 Why? -Neutron flux on the reactor vessel surface Neutron flux on the reactor vessel surface dropped to the 70 percent of original projected neutron flux. FZ,N V calculated or measured neutron flux FS,Z - calculated neutron flux of original project loads 8

9 Why? Reasons for fuel change Other Technical + Safety + Legislative - fuel integrity - technical progress (new materials, new manufacturing technologies) - operational experiences (e.g. power peak in the upper part of CA fuel supplier starting use hafnium plate in this part ) 9

10 Why? - Number of leaky fuel assemblies 3.unit and 4.unit Bohunice NPP 10

11 Why? - Number of leaky fuel assemblies 1.unit and 2.unit Bohunice NPP unit 17 2.unit blok 1.blok 11

12 Fuel for WWER-440 reactors 1/6 of core WWER-440 reactor Power:1471 Mwt(107%) Number: 349 FA+CA FA: 312 CA:37 Hexagonal shape with shroud 210 assemblies have Outlet temperature measurement 36 asseblies contains 7 SPND detector in central tube ALL TYPES FUEL COMES FROM RUSSIA TVEL. 12

13 Fuel types used in NPP Bohunice II.generation I.generation /2011 operation experiences

14 Next type of fuel from 2012 average enrichment 4,87 % 14

15 How? - Sequence of new type of fuel introduction. What is new type of fuel (Safety manual of state authority)? Fuel which changed - structure( e.g. space grid,nozzle) - thermo-hydraulics (e.g. flow rate,mixing of coolant ) - neutron- physical characteristics ( e.g. water-uranium ratio) - material composition It is two possibilities introduction of new fuel Introduction of fuel which is not used in the same type of reactor core before. Introduction of fuel which is used in the same type of reactor core before. Fortunately we used second type of introduction. In next slide you can see schedule of GD II4,25% enrichment fuel introduction. 15

16 How? - Schedule of GD II type of fuel introduction. 16

17 How? - What we need for licensing. Before using: Safety analysis report Chapter 4 (reactor core) Chapter 15 (safety analysis) Chapter 16 (limits and conditions power distribution and control and safety rod position, maybe boron acid cocentraton in spent fuel pond or during refueling, assemblies outlet temperature) Analysis for fresh fuel transport and storage technology. Analysis for spent fuel transport and storage technology. Subcriticality analysis during refueling. List of internal instruction in connection with fuel change. After: Verification of calculating values. 17

18 Verification of calculation - Materials for state authority Results of standard physical and energetic start-up. Results of all non-standard test done during physical and energetic startup. Operational history of power distribution - power peaking factor, DNBR, q lin, maximal subchanel temperature... Every 100. FPD Cycle evaluation After end of cycle Power distribution,critical boron acid concentration, burn-up, on-line monitoring of isotops in coolant 18

19 Verification during calculation Neutron-phyisical characteristics and safety significant parameters of first (second) transitional cycle are calculated by - fuel and chapter 4. supplier (TVEL- Kurchatov inst. ) - VUJE plc. Kurchatov inst. use BIPR code VUJE plc use BIPR code (same code but as spectral code use HELIOS, KI use KASSETA) Next transitional cycles is calculated only by VUJE plc. In 2012 our company planned buy code BIPR for independent verification of all cycles. 19

20 Verification during physical start-up Standard parameters for verification during start-up - Critical concentration of boric acid ± 0.4 g/kg - Efficiency of boric acid ± 17 % - Integral 6.CA group efficiency ± 17 % - Izotermical temperature reacitivity coefficient ± e-2 %/C - Connection between CA and control rod drive ρ<= -0,03βef - Hydraulic parameters zero power - Core symetry energy level - Safety system eff. ± 21 % - Rod drop time 8-13 s -Thermo-hydraulic parameters measurement near 100% Non- standard parameters - Safety system eff. without worst rod ± 21 % - Eff. of ejected control rod ± 21 % - Asymptotic period ± 30 % 20

21 Verification during physical start-up -Safety system eff. all rods and without worst rod Safety rod eff.- all Safety rod eff.- without worst 5 Deviation [ %] Cycle number 21

22 Verification during physical start-up Critical borid acid deviation 0,2 0,1 Deviation [g/kg] 0-0,1-0, ,3-0,4 Cycle number 22

23 Verification during start-up Coolant flow-rate and reactor heating-up at 100% 23

24 Verification during operation Parameters for verification - boric acid concentration lenght of borid acid cycle - power distribution radial asembly-wise power peaking factors - pinwise power peaking factors - maximal linear power - burn-up We compare measured values with values calculated by BIPR code. For internal control we use in-core measurement system SCORPIO internal code MOBY-DICK. 24

25 Verification during operation maximal radial asembly-wise power peaking factor 25

26 Verification during operation Maximal pin-wise power peaking factor 26

27 Verification during operation maximal linear power 27

28 Verification during operation - critical boric acid concentration during cycle (mixed core with gd) 6 0, CB measur. CBBIPR CB SCORPIO Cbdev 0,40 0,30 cb [g/kg] 3 0,20 0,10 2 0,00 1-0,10 0-0, Tef [dni] 28

29 Verification during operation - critical boric acid concentration during cycle (core with profiled fuel) 29

30 Verification of calculation Every month we prepare input data for our caculation supplier - power history for previous month - measured power distribution power peaking factors - boric acid concentracion Supplier compare measurement and calculated values and results send back. 30

31 Summary In Slovakia we dont have any special requirements for mixed cores. Only for new type of fuel. To this time we use fuel which is used in the same type of reactor before (Russia). It is possible, but it is difficult. For operative control of reactor core we have three limits» Pin-power [kw]» Maximal linear power (depends on pin burn-up)[w/cm]» Outlet temperature of fuel assemblies[c] Long-term monitoring of deviation between caculated values and measured values are elementary for calculated value evaluation. Our monitoring of this deviation shows, that accuraccy of computer codes used to core calculation is stable. 31

32 Thank you for your attention! 32