MIT NUCLEAR REACTOR LABORATORY an MIT Interdepartmental Center

Task 3: Core Instrumentation Planning and Benchmarking Lin-wen Hu, David Carpenter, Kaichao Sun

Nov.  2-­‐3,  2016  –  TREAT  IRP  Biannual  Mee<ng,  MIT  

Task 3 Overview

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Ø Instrumentation Plan o Identify TREAT core monitoring needs o Select sensors and requirements o Develop instrumentation plan

Ø Benchmarking o Design and testing of in-reactor instrumentation o Modeling (performance and safety) o Validation experiments

— Steady-state and transient tests o Analyze data and develop instrumentation report

Instrumentation Plan

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Ø Draft of Plan completed – next step to get feedback from INL

Ø Review of instrumentation layout and types: o Neutron flux, o Thermal power, o  In-core temperatures.

Ø Suggesting new types of sensors o Miniaturized sensors for in-core locations o  Improved fidelity over critical power ranges o Higher spatial resolution

Ø Calibration and readiness

Ø Operational reactor power measurements use radial instrumentation ports o Terminate outside of permanent graphite reflector o Ion chambers and proportional counts for neutron flux

Ø In-core thermocouple-instrumented assemblies for assembly clad, reflector, and fuel block temperatures

Ø Calibration of neutron detectors to reactor power uses steady-state power ~80 kW, o Heat balance with air-

cooling system, o Requires extrapolation to higher power

TREAT Instrumentation

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14  6”  Radial  Instrumenta3on  Ports  

INL/EXT-­‐15-­‐35372  

Startup Testing and Calibration

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Ø During TREAT physics testing fission chambers were positioned within the core (coolant channels and element centers)

Ø Fission chambers, activation foils, and thermocouples moved to various radial and axial positions o  Drive system mounted on reactor top shield to move

detectors and foils o  Core configuration dependent

Ø Measurement of vital parameters o  Temp and flux profile o  Reactivity coefficients o  Detector power calibration o  Neutron spectrum o  Transient response

ANL-­‐6173  

INL/EXT-­‐15-­‐35372  

Updating Instrumentation

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Ø TREAT updating ion chambers in-place Ø Advanced ion/fission chamber technology

o  Micro-Pocket Fission Detectors for local measurement of neutron flux – spectrum differentiation

o  Gas-filled cylindrical FC probes (e.g. CEA) o  Self-powered detectors sensitive to neutron or

gamma flux – rapid response SPND tested in TREAT previously

Ø Temperature measurement o  Traditional thermocouples reliable for most point

measurements o  IR pyrometry can evaluate surfaces o  Fiber-optic measurement (temperature or strain)

possible to interrogate multiple locations along a single fiber

Photonis  FC  probes  

MPFD  design  (Unruh,  2012)  

Thermocoax  SPD  

MITR Experiment Plan

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Ø  Instrumenta<on  Plan  –  DraD  Completed  (FY16)  o  Instrumenta<on  assembly  for  in-­‐pile  tests  to  be  designed  –    Ongoing  (04/2017)  

Ø  Experiment  Loca<ons  and  Transient  Selec<ons  –  Completed  (FY16)  o  Total  of  6  in-­‐core  loca<ons  o  2  types  of  transient  

Ø  Reactor  Safety  Analysis  for  Proposed  Transients  –  Ongoing    o  Transient  analysis  using  PARET/ANL  (fixed  inlet  temperature)  –  Completed    o  MITR  RELAP5  system  model  valida<on  for  steady-­‐state–  Ongoing  (11/2016)  o  Transient  analysis  using  RELAP5  –  To  be  done  (12/2016)  o  MITR  Safeguards  CommiYee  Mee<ng  (12/2016)  o  Reactor  experiment  approval  (03/2017)  

Ø  Safety  Evalua<on  Report  (SER)  for  MITR  Experiments  (06/2017)  

Ø  Performing  Instrumenta<on  Test  Experiments  at  MITR  (07/2017)  

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Experiment Locations

1.  Total  of  6  Projected  Loca3ons:  Ø  2  A-­‐ring  (innermost  ring)  posi3ons  

Ø  1  B-­‐ring  (middle  ring)  posi3on  

Ø  2  axial  loca3ons  at  each  posi3on    for  different  fast-­‐to-­‐thermal  ra3os  

Ø  2  out  of  6  loca3ons  run  transients  

-­‐30

-­‐20

-­‐10

0

10

20

30

0.0E+00 5.0E+13 1.0E+14 1.5E+14 2.0E+14 2.5E+14 3.0E+14

Distance  to

 Core  Ce

nter  (cm)

Neutron  Flux  (n/cm2/s)

Thermal  Flux  (<1  eV) Fast  Flux  (>  0.1MeV)Total  Flux  (full  energy  range)

v  Static measurements / calibrations will be performed at all 6 locations.

v  Transient tests will be performed for “A-1 Higher ” and “B-3 Lower” for small and large fast-to-thermal ratios, respectively.

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Experiment Test Plan 2.  Sta3c  Measurements  (6):  Ø  The  MITR  operates  at  steady  power  of  

60  kW  (LSSS  at  100  kW)  with  top  lid  open  and  natural  convec3on  mode.  

Ø  Different  in-­‐core  and  ex-­‐core  posi3ons  could  be  used  for  instrument  test.  

3.  “Slow  Posi3ve”  Transient  (2):  Ø  Withdrawing  Regula3ng  Rod  (~  200  mβ  worth)  to  

create  a  posi3ve  period  more  than  50  s  (LSSS  at  7  s).  

Ø  Steady  power  levels  prior  and  a[er  the  transient  are  planned  to  be  600  W  and  60  kW  (LSSS  at  100  kW).  

4.  “Fast  Nega3ve”  Transient  (2):  Ø  Using  Shim  Blade  Drop  and  Scram  to  create  nega3ve  

period  less  than  0.5  s.  

Ø  Steady  power  levels  prior  the  transient  is  planned  to  be  60  kW.  

Unit:  n/cm2/s  Thermal  Flux    

(<  1  eV)  

Fast    Flux    

(>  0.1  MeV)  

Total    Flux  

MITR  at  100  kW   6.17E+11   2.22E+12   4.63E+12  

MITR  at  6  MW   3.70E+13   1.33E+14   2.78E+14  

TREAT  at  100  kW   5.79E+11   2.72E+11   1.45E+12  

TREAT  peaks  at    18,000  MW   1.04E+17   4.90E+16   2.61E+17  

Instrument Calibration

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Ø Pre-irradiation testing o  Sealed gamma and neutron sources o  Spectrum-characterized beamlines

Ø Neutron Activation Analysis Lab o  Gold, Fe, 304 foils and wires for fluence o  Cadmium ratio

Ø Verify instrument response curves Ø Calibration requirements part of instrumentation plan

NAA  Lab  

Mul3-­‐sensor  Beamline  

Exis3ng  calibrated  instruments  for  rad  work