NUCLEAR MEASUREMENT OF WATER LEVEL AND FUEL CONCENTRATION

FOR SPENT-FUEL POOLS AND REACTORS

Lessons Not Learned from TMI, LOFT, & Fukushima

Alexander DeVolpi, PhDNuclear Applications Company

Oceanside, California, USA

(Booth at Tech Expo open till about 4pm today)

ANS Anaheim, 11 Nov. 2014

File: C:\Users\Nac\Documents\Nucl Appl Co\ANS Anaheim Nov 2014\ANS Anaheim Monitoring Presentation.025.wpd September 19, 2014

PRM-50-113PETITION

ATTACHMENT 3

RADIATION MONITORING CAPABILITIESCurrently Overlooked (But Feasible)

! Water level can be tracked in real time > in reactors and SFPs> before, during, and after a loss-of-coolant accident

! The instrumentation would be autonomous and robust> ex-vessel (outside RPV —reactor pressure vessel)> not vulnerable (installed inside PCV – reactor containment)

! Other important operating parameters changes can be monitored> water temperature and density (in reactors and SFPs)> fission-product migration (in SFPs) > neutron-absorbers (in SFPs)

! Radiation monitoring has additional technical benefits > measuring axial-burnup profiles for spent fuel in SFPs

> inferring dynamic nuclear-process changes (reactors and SFPs )

> determining post-accident fuel-reconcentration in reactors(e.g., Fukushima)

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GAMMA-RAY EX-VESSEL MONITORING EXPERIENCESubstantial Proven Capability

! Based on well-developed hodoscope nuclear-diagnostic systems> collimated radiation detection> multi-channel, neutron and gamma> real time measurements, good spatial resolution

! Hodoscopes operated at TREAT (INEL) and CABRI (CEA)> ex-vessel destructive and non-destructive experiments> scalable to full-size reactors> starting in the 1960s: decades of experience

! Many ex-vessel nuclear-reactor-safety diagnostic tests conducted> nuclear-accident conditions simulated> at the TREAT reactor (INEL, Idaho) > at CABRI reactor (CEA/EURATOM, Cadarache) > hodoscope tests at a 3rd reactor (PARKA, Los Alamos)

! Gamma-monitoring calculations support monitoring feasibility> based on LOFT (INEL) experiments > independently confirmed by CEA/EURATOM

! TREAT gamma-detector multi-channel hodoscope array > 100 small sodium-iodide hodoscope detector modules > data recorded simultaneous with neutron detectors> fuel, container, and coolant detectable> next slide shows nuclear diagnostic arrangement at TREAT

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! (Next slide is example of time-resolved hodoscope diagnostics)

Schematic With Early Version of 334-channel Hodoscope

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! (Next slide shows ex-vessel experimental results, detected through 2.5 cm steel)

Typical Hodoscope Transient Data Results (Time-resolved “hodographs” for single-pin experiment)

Fuel pin inside thick steel containment, deliberately subjected to destructive high-power transient in TREAT reactor.

Notes: time resolution, milliseconds; spatial resolution, millimeters

(Ex-vessel hodoscope diagnostic system located 5 meters from the fuel pin.)

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DETECTING GAMMA RADIATION (Despite Thick Intervening Steel Wall)

7 0.5-cm fuel pin

7 2.5-cm thick steel

attenuator

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5 m to hodoscope

! (Next 2 slides: change in gamma flux due to loss of coolant)

Extremely Sensitive Gamma-ray Hodoscope Capability

Fuel pin (offset) behind 2.5-cm thick steel attenuator.

(Note: thin inner steel tubing and fuel-pin cladding inferred from measurements made outside reactor at

distance of 5m.)

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LOFT Demonstration of Measurable Coolant Voiding

Escaping reactor gamma flux (top panel)tracks core voiding (middle panel)

and downcomer voiding (bottom panel).

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Gamma Response to PWR Coolant Voiding

(Calculated by CEA/Cadarache)

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Diagram Included in 1987 Patent for Monitoring Water-level in a PWR

Top drawing illustrates axial locations of 10 collimated ex-vessel detectorsmounted inside biological containment.

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TECHNOLOGY HIGHLIGHTS Ex-vessel Gamma-hodoscope Monitoring

! Proven nuclear-reactor diagnostic technology> originated at Argonne National Laboratory> starting in the 1960s: decades of tests in 3 reactors> substantial, relevant database> for reactor water-level monitoring> (also for ex-vessel fuel-debris reconcentration)

! Meets requirements for adaptation to power reactors> experience-based design and function> 3-D tomographic deconvolution and analysis demonstrated> over 100 relevant technical publications

! TMI and Fukushima LOCAs> substantiate the need for ex-vessel water-level monitoring> incomprehensible regulatory indifference to this safety

enhancement

! (Next viewgraph illustrates hypothetical LOCA core-meltdownsequence being comprehensively monitored)

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Ex-vessel Reactor MonitoringWater-Level and Fuel-Reconcentration

(During loss-of-coolant accident)

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SFP Gamma-MonitoringHodoscope Vertical Array,

designed to fit in an SFP gridlocation

CONFIGURATION FOR GAMMA MONITORING (In-vessel for SFPs, Ex-vessel for Reactors)

! Application of proven modularhodoscope technology

! High degree of autonomy andredundancy

! Pre-installed vertical-array gamma-monitoring modular units

! Externally structured like a fuel assembly insertable in SFP grid

! Detects vertical and radial distribution SFP fission-productgamma rays

! Similar configuration could beused for reactor ex-vessel detection > of water level > and fuel reconcentration

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Possible Peripheral Locations for Multiple SFP Gamma-Monitoring Arrays

SFP MONITORING OPTIONS

! SFPs can use very similar gamma-hodoscope diagnostics > collimated detectors adapted for spent-fuel radiation

> sealed vertical arrays installed in SFP grid positions > externally look and handle like partial fuel assemblies

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SFP NUCLEAR-MONITORING EXPECTATIONS

! Multiple objectives could be met> by monitoring spent-fuel gamma radiation> to meet current nuclear-safety & operational requirements> as well as gain derivative benefits

> avoid limitations of non-nuclear (conventional) instruments

! Specific consolidated applications would include > continuous surveillance of neutron absorbers> monitoring water level, density, and temperature changes> profiling spent-fuel-assembly burnup profiles

! Benefit more from Fukushima lessons (than TMI lessons)> adapting technology developed many years ago> in DOE/NEA nuclear-diagnostics programs> for real-time reactor ex-vessel measurements

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IDENTIFIABLE SHORTCOMINGSOF REGULATORY ASSESSMENTS

! Four expensive, traumatic LOCAs (TMI and Fukushima)

! Reactor water-level and fuel-concentration still not measured

! Plus increased concern now about SFP operating conditions

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NUCLEAR-ACCIDENT TECHNICAL ASSESSMENTS (National, Industrial, International)

ALL INDIFFERENT TO COOLANT MONITORING

! TMI Loss-of-Coolant Meltdown 1979:

> accident initiated or aggravated because operators unawareof coolant loss

> post-TMI reports: Rogovin, Kemeny, INPO, IAEA, NRC.... > all fail to prioritize robust, autonomous monitoring of coolant

! Fukushima Loss-of-Coolant Meltdowns 2011:

> accident resulted from tsunami, aggravated by loss-of-power> post-accident reports NRC, IAEA, INPO....> still fail to give high priority to autonomous coolant monitoring> NRC places water-level monitoring in their Tier 3 basement

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NATIONAL ACADEMY OF SCIENCES(First to Prioritize Water-level Monitoring)

! Recently U.S. National Academy of Sciences called for:> robust instrumentation> for monitoring critical thermodynamic parameters> in reactors, containments, and spent-fuel pools> (among highest-level recommendations)

! My experienced Fukushima reactor-diagnostics message:> reactor and SFP coolant level can be, and should be,> reliably and continuously measured

! The technology was proven many decades ago> for fuel, coolant, and material monitoring> from outside containment vessels (ex-vessel)> with time- and space-resolved capability

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SUMMARYUNEXPLOITED ROLE FOR GAMMA-RADIATION MONITORING

(Reactors and SFPs)

! Real-time tracking of coolant level> feasible in reactors and SFPs> before, during, and after a loss-of-coolant accident

! Timely detection of parameter changes in reactors and SFPs > thermodynamic: water temperature and density

> nuclear: neutron-absorbers> fission-products: escape from fuel rods

! Measuring additional parameters in real time

> axial-burnup profiles for spent fuel > inferring dynamic nuclear-processes in reactors and SFPs

> determining post-accident fuel-reconcentration in reactors

! Technology was proven decades ago in three test reactors

! National Academy of Sciences has (at last) recognized the need> for water-level monitoring> (but not preparations for measuring fuel-reconcentration)

! Professional indignation: about 30 years overdue> regulatory indifference to real-time water-level monitoring

QUESTIONS/COMMENTS?

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