CANDU Safety #1 - CANDU Nuclear Power Plant Design Dr. V.G. Snell Director Safety & Licensing

Transcription

1 CANDU Safety #1 - CANDU Nuclear Power Plant Design Dr. V.G. Snell Director Safety & Licensing 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 1

2 What Accident is This? 28 killed, 36 injured, 1821 homes and 167 buildings destroyed 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 2

3 Or this? It could take months to determine what caused an explosion early Wednesday at Hawthorn power plant. The generating plant, which produces 15 percent of Kansas City Power & Light's electricity, will be out of operation for an extended period of time 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 3

4 What is CANDU? CANada Deuterium Uranium - the name gives the design started as the Canadian contribution to the War effort: to produce plutonium using natural uranium and heavy water the first reactor to go critical outside the U.S. was ZEEP in too late for the War but started the Canadian nuclear civilian power programme 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 4

5 ZEEP - Canada s First Reactor Right - ZEEP building at Chalk River Laboratories near Chalk River, Ontario, as it appeared around the time of the first startup in Left - ZEEP taken during the 1950s. Experiments were conducted on fuel for early CANDU designs, including NPD and Douglas Point 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 5

6 CANDU Genealogy Darlington MW Class Reactors Bruce A Bruce B CANDU 9 Power (MWe) MW Class Reactors Pt Lepreau Embalse Gentilly 2 Wolsong 1 Pickering A Pickering B Cernavoda Wolsong 2,3,4 Qinshan 1&2 - RAPP 1, NRU Douglas Point KANUPP Research & Prototype Reactors ZEEP NRX NPD /05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 6 Years 2010

7 Reactor CANDU PWR 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 7

8 Reactor CANDU 380 small diameter (10 cm), thin (4.2 mm) pressure tubes horizontal orientation heavy water coolant (312 C) separate heavy water moderator (65 C) reactivity devices in low pressure moderator large core, low energy density (11 MW / m 3 ) PWR 1 large diameter, thick pressure vessel vertical orientation light water coolant (329 C) coolant is the same as the moderator, both hot reactivity devices in high pressure coolant / moderator small core, high energy density (60 MW / m 3 ) 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 8

9 Fuel CANDU PWR 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 9

10 Fuel CANDU natural uranium low burnup short bundles (0.5 metres) on-power refuelling remove defected fuel during operation PWR enriched uranium high burnup long bundles (3.8 metres) shut down to refuel remove defective fuel only when shut down to refuel 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 10

11 Fuel Channel CANDU fuel bundles lie inside the pressure tube a calandria tube separates the pressure tube from the moderator a gas gap between the pressure tube and the calandria tube provides thermal insulation 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 11

12 Fuel channel 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 12

13 Heat Transport System COMPARISON OF HEAT TRANSPORT SYSTEMS PHWR PWR Headers * SMALL PIPING - LOW STRESSES * SIMPLE PIPING, LARGE PRESSURE VESSEL * SAFETY RODS IN MODERATOR * SIMPLE FUELLING - ONCE PER YEAR * ON-POWER FUELLING * LARGE REACTIVITY CHANGE IN OPERATION * FULL-PRESSURE RHR LOOPS * ECC NEEDED TO STOP MELTING AFTER LOCA 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 13

14 Heat Transport System CANDU each channel is individually connected to collectors (headers) above the core pumps, steam generators above the core each particle of fluid goes through the core twice before it gets back to where it started one or two loops operating pressure ~10 MPa PWR the pressure vessel is a large pot containing all the core water in one place pumps, steam generators above the core each particle of fluid goes through the core once before it gets back to where it started two, three or four loops operating pressure ~15.5 MPa 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 14

15 Moderator cold: 65 C C heavy water, large inventory: ~260 Mg cooling capacity: 100 MW(th th) ) or about 4.6% of full power Calandria Relief Pipe Calandria Vault Pump 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 15

16 Reactivity Control short-term: term: in-core devices (absorber & adjuster rods, light water) long-term: on-power refuelling no absorber in coolant little absorber in moderator except during startup after a long shutdown routine control: dual redundant digital computers 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 16

17 Reactivity Control Slave Master 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 17

18 Secondary Side conventional nuclear steam generators and turbine / generator the steam generators have heavy water on the primary side steam conditions: 4.7 MPa and 260 C Manway Secondary Separators Primary Separators U-Bend Shroud Support Plate Cold leg Preheater Feedwater Inlet D 2 O Outlet Main steam nozzle Shroud cone Tube bundle Hot leg Tubesheet D 2 O Inlet 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 18

19 Auxiliary Systems CANDU has systems not found in PWRs automated refuelling & fuel handling system annulus gas system (leak-before before-break) break) shield cooling system heavy water vapour and liquid recovery and systems that are found in PWRs primary pressure & inventory control shutdown cooling system shutdown systems, Emergency Core Cooling, containment, emergency power etc. 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 19

20 Systems CANDU Does Not Need Some PWR systems are not needed in CANDU or are much simpler no boron control system in the coolant no boron addition to ECC water no criticality concerns outside the reactor for new or used fuel simpler core, reactivity devices 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 20

21 Summary 24/05/01 8:14 AM CANDU Safety - #1 - CANDU Design.ppt Rev. 1 vgs 21