OPAL CNS Moderator Performance Weijian Lu OPAL CNS Reliability from - - PowerPoint PPT Presentation

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Oct 02, 2022 36 likes •216 views

OPAL CNS Moderator Performance Weijian Lu OPAL CNS Reliability from Commissioning (Nov 2006) to Present 100 90 80 70 CNS Reliability (%) 60 50 40 30 20 10 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51

SLIDE 1

OPAL CNS Moderator Performance

Weijian Lu

SLIDE 2

10 20 30 40 50 60 70 80 90 100 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 CNS Reliability (%) Reactor Cycle No.

OPAL CNS Reliability from Commissioning (Nov 2006) to Present

CNS Reliability (%) OPAL Reliability (%)

SLIDE 3

OPAL Reactor Facilities

SLIDE 4

What Happened to CNS Flux?

In early 2017, neutron users have noticed a

significant drop in cold neutron flux ~ -20%

Possible causes

– Neutron guides (fault discovered in 2011) – Source flux

SLIDE 5

Heat Load vs Reactor Power

SLIDE 6

85% 90% 95% 100% 105% 110% 115%

CNS Heat Load vs Reactor Power

Nuclear Heat Load (normalised to 3.6 kW) OPAL Thermal Power (normalised to 20 MW)

SLIDE 7

Helium Temperature Sensor Drift

Sensors had recently been checked
Measured a stable bias of ~1 K subject to slow

drift (years), but no evidence for cycle-to-cycle “oscillation”

Process Conditions (nominal) Sensitivity Typical Operational Variation by Conservative Estimation Resultant CNS Flux Variation Helium temp. sensor drift 15%/K ~ -1 K

SLIDE 8

200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400

CNS Heat Load (watts)

Heat Load (watts)

SLIDE 9

CNS Flux Sensitivity (1)

Process Conditions (nominal) Sensitivity Typical Operational Variation by Conservative Estimation Resultant CNS Flux Variation D2O purity (99.5%) 6.66%/% ±0.5% ±3.33% D2O temp. (35 °C)

0.0228%/°C

±1 °C ±0.0228% D2O gap between CNS thimble and beam tube (1 mm)

5.52%/mm

negligible negligible LD2 temp. (24.5 K)

4.38%/K

±0.5 K ±2.2% LD2 ortho/para ratio (3:1) 0.288%/% Unknown but expected to be small ±1% (order of magnitude estimation)

SLIDE 10

MCNP Calculation vs Measurement

0,95 0,96 0,97 0,98 0,99 1,00 1,01 1,02 1,03 1,04 1,05 1,06 1,07 1,08 1,09 1,10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Ratio Neutron Wavelength

CNS Gain from 20.5 K to 19.6 K (4 Dec 2016)

BILBY 5-Dec / 3-Dec MCNP Calc.

SLIDE 11

CNS Flux Sensitivity (2)

Process Conditions (nominal) Sensitivity Typical Operational Variation by Conservative Estimation Resultant CNS Flux Variation Control rod positions (critical positions for the first core) 5.58% between actual configuration and that after 180° rotation Control rod movement pattern is repeated in every reactor cycle N/A Reactor core (first core and equilibrium core) 4.56% between the two cores Fuel management strategy To be assessed further

SLIDE 12

Fuel Management Programs

Cell code: CONDOR
Diffusion code: CITVAP

– Flux and power density – Reactivity – Poison transients – Adjoint flux – Kinetic parameters

SLIDE 13

Core Power Density – Flux Tilt

CG4 beam tube CG1-3 beam tube D2O moderator D2 moderator Reactor Core

SLIDE 14

0,90 0,95 1,00 1,05 1,10 85% 90% 95% 100% 105% 110% 115%

CNS Heat Load vs Reactor Power

Nuclear Heat Load (normalised to 3.6 kW) OPAL Thermal Power (normalised to 20 MW) Flux Tile N-S biased to average

SLIDE 15

Conclusions

CNS heat load is an excellent indicator of

source flux

Core configuration can have a significant

impact on the CNS flux

Can be predicted by numerical calculations

SLIDE 16

SLIDE 17