CNS Fuel Technology Course: Fuel Design Requirements

Transcription

1 4525 Lakeshore Road Burlington, Ontario L7L 1B3 Phone: FAX: CNS Fuel Technology Course: Fuel Design Requirements Al Manzer, B.Sc., M. Eng. Senior Fuel Specialist CANTECH Associates Ltd Best Western Hotel Oshawa, ON 2014 Oct 6-7

2 Outline Original Design Criteria and brief CANDU Fuel History Fuel Design Requirements for 1970s Fuel Design Requirements for 1980s Fuel Design Requirements for 1990s+ Future Trend

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4 Birth of CANDU Fuel (1950s) Original NPD Reactor Design in 1954: 10 MW Plant Vertical pressure vessel Off-power refuelling Long fuel assemblies (= core length) Uranium metal as fuel material Stainless steel fuel cladding being considered NPD redesigned, construction halted in 1957: 20 MW Plant Horizontal with Zr alloy pressure tubes On-power refuelling Short fuel bundles (19.5 inches long) Uranium Dioxide ceramic as fuel material Zr alloy fuel cladding

5 Criteria for Fuel Development (1950s) W.B. Lewis stated that CANDU Fuel: Must be safe, reliable, low risk of release of radioactive fission products» no systematic fuel failures Must have good neutron economy, i.e.,» low neutron absorption materials Must meet power specifications, i.e.,» 1 MW per fuel bundle» no distortion in 1-4 years in-reactor Must be easily handled Must be cheap» 1 mils/kwh (0.1 cents/kwh)

6 CANDU Fuel Bundle Types (Past) 7 Element NPD (1st Charge) NPD 19 Element (9 reactors) 18 Element CANDU BLW (1 reactor) Raps 1 NPD Raps 2 KANUPP Maps 1 Douglas Point Maps 2 Gentilly 1 Naps 1 Naps 2

7 CANDU Fuel Bundle Types (Present) 28 Element Pickering (8 reactors) Pickering 1 Pickering 5 Pickering 2 Pickering 6 Pickering 3 Pickering 7 Pickering 4 Pickering 8 37 Element Bruce/Darlington (12 reactors) Bruce 1 Bruce 5 Darlington 1 Bruce 2 Bruce 6 Darlington 2 Bruce 3 Bruce 7 Darlington 3 Bruce 4 Bruce 8 Darlington 4 37 Element CANDU 6 (11 reactors) Pt Lepreau Gentilly 2 Embalse Wolsong 1-4 Cernavoda 1-2 Qinshan 1-2

8 Other CANDU Fuel Bundle Types 43 Element CANFLEX (1979) (replacing 37 Element) Demonstration Irradiations ( ) AECL/KAERI/Bruce Power Project 37M Element (improved operating margins) Implemented in Bruce and Darlington (~2013) OPG/Bruce Power Projects

9 Fuel Design Requirements (1970s) CANDU Fuel must meet the requirements imposed by the reactor interfacing systems: Heat Transport System (or Primary Coolant Circuit) Fuel Channels Fuel Handling Systems Fuel Management (Nuclear Design, or Reactor Physics) Reactor interfacing systems must meet requirements imposed by CANDU Fuel

10 Fuel Duty Cycle

11 Heat Transport System Requirements on Fuel Design 1. The pressure drop over fuel bundles in each fuel channel must be compatible with the design allowance of the heat transport system. 2. The fuel must withstand flow induced vibration. 3. The thermal performance of the bundle must be acceptable for all normal operating conditions. 4. The fuel elements must withstand the coolant pressure during normal operation. 5. The fuel elements must contain fission products during normal operation. 6. The uranium contamination on surfaces of the asmanufactured fuel bundles must be minimized.

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14 Fuel Channel Requirements on Fuel Design 1. The bearing pads must not reduce the wall thickness of the pressure tube below the design allowance. 2. The fuel bundle must withstand the loads caused by the coolant hydraulic drag (and the fuelling machine ram). 3. The fuel bundle must not jam in the fuel channel.

15 On-Power Refuelling

16 Full Length Fuel Channel

17 CANDU 6 Fuelling Scheme

18 Fuel Loading Sequence (Upstream End) FLOW ---> SHIELD PLUG REMOVED, 1st BUNDLE PAIR LOADED N N st NEW BUNDLE SW EPT BY COOLANT 2nd NEW BUNDLE PUSHED INTO POSITION REFUELLING IMPACT N N N N nd BUNDLE PAIR LOADED N N N N rd BUNDLE PAIR LOADED N N N N N N FUEL COLUMN DISPLACED TO ALLOW F/M MAGAZINE ROTATION N N N N N N th BUNDLE PAIR LOADED N N N N N N N N 1 2 3

19 Fuel Unloading Sequence (Downstream End) N N N N N N N N Bundle 12 loaded against Sidestops SIDESTOPS INSERTED SHIELD PLUG UNLOADED st BUNDLE PAIR UNLOADED nd BUNDLE PAIR UNLOADED rd BUNDLE PAIR UNLOADED N N Bundle 4 loaded against Sidestops 4th BUNDLE PAIR UNLOADED N N N N SHIELD PLUG READY FOR LOADING N N N N

20 Fuel Unloading Sequence (Upstream End) N N N N N N N N Bundle 12 loaded against Sidestops Coolant Drag > Friction Bundle 4 loaded against Sidestops

21 Fuel Handling System Requirements on Fuel Design 1. The fuel bundle must not jam in the fuel handling systems. 2. During refuelling, the fuel bundle must withstand the loads caused by cross flow in the liner hole region of the endfittings. 3. The fuel bundle must withstand refuelling impacts. 4. The fuel bundle must have sufficient flexibility to allow for differential expansion of the fuel elements and parallelogramming (or tilt of bundle) within a sagged pressure tube.

22 Fuel Management Requirements on Fuel Design 1. The ends of the fuel bundles must minimize neutron absorption and withstand end flux peaking due to the gap between the UO 2 in adjacent bundles. 2. The fuel bundles must be able to operate at high powers continuously. 3. The fuel bundle must withstand power changes due to refuelling and movement of the reactivity control mechanisms refuelling impacts.

23 Fuel Design Requirements on Other Systems 1. The interfacing systems must not cause systematic fuel failures. (translates to at least 22 specific requirements!) 2. The components of the fuel channel and fuel handling systems must have sufficient allowance to protect against damage due to the interaction of fuel. (translates to at least 4 specific requirements!)

24 Fuel Design Requirements (1980s) In response to the seismic requirements of a potential CANDU reactor client, AECL agreed to include one more fuel design requirement 1. Fuel bundle must be able to withstand seismic loads while inside the pressure boundary of the heat transport system. For a design basis earthquake, the fuel must maintain coolable geometry and the fuel elements must contain fission products.

25 Fuel Design Requirements (1990s+) In recent years some CANDU users (Bruce Power) have developed new requirements for LVRF which had new design features: 1. Higher operating margins for dryout (CHF buttons). 2. Lower power pulses during Loss of coolant accidents. 3. Lower coolant void reactivity (Fuel enrichment, burnable poisons)

26 50 Year Trend on Fuel Design Requirements ACR, LVRF C6s, Bruce B, 1250 MW Darlington, CANDU 3 CANDU9 EC6? AFCR? TCR? NPD, DP, G1, Pick, Bruce NPD, DP, G1, Pick, Bruce 26

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