SMR Design #2 (IMSR) Flashcards
IMSR stands for
itegral molten salt reactor
MSRs are _____ fueled reactors
liquid fueled
Flows between ___ and ____ to transfer heat to ______
a critical core and primary heat exchanger to transfer heat to a secondary “clean” salt
___ temperature couples well to ___/____ with ____ efficiency
high (700C)
to steam / gas brayton
high (up to 50%)
What is used to moderate
typically graphite
but fast spectrum concepts as well as using chlorides
can be configured as ________ or _____ using ____ _____ Uranium
thorium breeders (MSR-Breeder)
simplified burners (MSR-Burner)
Low Enriched Uranium
Related concept is ______
MSR-Cooled (FHR)
Solid Fuels (TRISO) cooled with ___ which replaces ___ _____ ____
FLiNe salt
high pressure helium
Advantages of Fluoride Salts
-wide range of uranium and thorium solubility
-stable thermodynamically
do not undergo decomposition
-have very low vapor pressure at operating temp
-with redox control, low corrosion for stainless or nickel based alloys used for circulating salt plumbing
-no adverse reactions with air/water
-excellent thermal properties
-transparent
-very high boiling points
advantages of MSR - main 4
safety
reduced capital cost
long lived waste issues
resource sustainability and low fuel cycle
advantages of MSR - safety
enhanced ability for passive decay heat removal
inherent stability from strong negative reactivity coefficients
low pressure and no chemical driving force
cesium and iodine relativity stable within fuel slat
advantages of MSR -reduced capital cost
inherent safety simplified entire facility
low pressure, high thermal efficiency, superior coolants (smaller pumps, heat exchangers), no complex refuelling mechanisms
advantages of MSR - long lived waste issue
ideal system for consuming existent transuranic wastes
even msr-burner designs can see almost no transuranics going to waste
advantages of MSR - resource sustainability and low fuel cycle cost
thorium breeders obvious but msr burners also very efficient on uranium use
Liquid Fuel Affords Inherent Stability: Negative Temperature Reactivity Coefficients
negative feedback to a power and temp increase
values range up to -15pcm/C (pcm=10^-5 K)
Liquid Fuel Affords Inherent Stability: Very Low Reactivity control Requirements
online fuel makeup mean very little reactivity change with time
xenon 135 effects quite small as it bubbles out of salt
typical total shim requirements perhaps 0.5% dk?K (5mk =500 pcm)
Liquid Fuel Affords Inherent Stability:Control Rods in many cases viewed as optional
-reactor power can be controlled by amount of heat removed
- core average temp stays const, input - output temp varies
-steam island can effectively drive reactor
US Historic Timeline
- first envisaged in 1940s
1950s leading candidate in well funded aircraft reactor program (successful ARE test reactor operates in 1954 up to 860C)
1960-1970s MSBR “Thorium Breeder” (thought breeders needed due to uranium shortage, sodium fast breeder and molten salt breeder dominate, successful 8MWth 1965-69 minor issues uncovered
1970s falling of political axe (cancelled 1970s, work on MSR-Burner reactor the DMSR 1979-1980
aircraft nuclear propulsion program: initiated work on molten salt tech (1946-1961)
$1B Investment pioneering work
- molten salt fuels
liquid metal heat transfer
light weight metals
advanced I&C
high temp corrosion resistant materials
successful 2.5MWth aircraft Reactor experiment 1954
operating experience: MSRE successful demonstration
operation date
design features
moderator
piping
achievements
1965-1969 at ORNL
8MW thermal output
single fluid, simple bare core design
fuels…
graphite moderated
hastelloy N vessel and piping
first use of U-233 Fuel
first use mixed U/Pu salt fuel
on line refuelling
>13000 full power hours
end goal of ORNL Program the graphite moderated molten salt breeder reactor (1968-1976)
thorium to U233 Breeder
2250 MWth for 100MWe
single fluid with on sire chemical processing to remove fission products and collect excess U233
Breeding ratio 1.06 smaller than sodium fast reactor but low fissile loading meant comparable 20 yrs doubling time
off gas rapidly removed to lower losses to xenon
high power density given 4 yrs graphite lifetime leading to full core replacement
Early msr outside US: france
significant program through 1970s similar to ORNL
Early msr outside US: UK
modest efforts studying fast chloride systems
Early msr outside US: india
expanding collaborations with ORNL , major PuF3 chemistry facilities built
Early msr outside US:china
first reactor in china a zero power MSR
Early msr outside US:Russia
major program and only 1 continues well into 1980s (chernobyl led to cut back of most advanced reactor concepts)
generation IV Forum Goals: Sustainability 1
minimize and manage waste, reduce long term stewardship burden
generation IV Forum Goals
sustainability 1
sustainability 2
economics 1
Economics 2
safety and reliability
proliferation resistance and physical protection
generation IV Forum Goals: Sustainability 2
resource sustainability
generation IV Forum Goals: Economics 1
compete directly on cost with other energy systems
generation IV Forum Goals: Economics 2
finance risks similar to other energy systems
generation IV Forum Goals: safety and reliability
- excel in safety
- core damage frequency
- avoid offsite emergency response
major challenges of 1970’s MSR Breeder Design
online fission product removal
tritium control
reactivity temperature coefficients (only weak negative)
use of highly enriched uranium in Th/U233 cycle
off gas management
ling term corrosion or radiation damage
graphite replacement operations
why breeders
uranium is abundant (quoted resources are only what is confirmed by expensive drilling, more exploration equals more resources. higher U price means lower grade ores opened up as resource)
even large fleet expansion will not require breeder operations at least in intermediate term
msr burner approach of running of low enriched uranium solves many challenges
last major work of ORNL in late 1970s was MSR bURNER THE DENATURED MOLTEN SALT REACTOR (DMSR)
Issues solved by MSR-Burner Approach
fission product removal
reactivity coefficients
tritium control
HEU Use and Proliferation
Issues solved by MSR-Burner Approach: fission product removal
no need for salt processing
fuel salts used over long duration with periodic fuel additions
Issues solved by MSR-Burner Approach: reactivity coefficients
msr-burners have superior reactivity coefficients of temp
Issues solved by MSR-Burner Approach: tritium control
tritiums ability to pass through hot metal makes it a management challenge
able to avoid Li or Be use to virtually eliminate tritium production
NaF, KF, RbF and ZRF4 among low cost salts to accomplish goals
3rd nitrate salt loop employed, blocks tritium access to steam cycle
Issues solved by MSR-Burner Approach: HEU Use and Proliferation
uranium always LEU (denatURED)
STANDARD assay LEU <5% can be employed for startup and makeup fuel.
avoids need to construct new high assay lEU (HALEU) FACILITIES FOR ABOVE 10% enrichment needed by most other GEN IV systems
Pu content builds up to high 240-242 content and never separated even if fuel eventually recycled
can avoid all of thorium and thus U233 issues
slide 20 : tritium management
remaining challenges are material related
long term corrosion or radiation damage
graphite replacement
long term corrosion or radiation damage
high nickel alloys, 316 and 304 perform well if chemistry control is maintained
proving 30+ yr lifetime is challenge for reactor vessel and primary heat exchanger
graphite replacement
unclad graphite use gives very strong advantages
very low enrichment fuel (2% enrichment LEU)
makes out of core criticality virtually impossible
protects vessel wall from high neutron flux
its lifetime however is directly related to power density
integral molten salt reactor ISMR
by terrestrial eng
msr burning design, 2% LEU startup and <5% LEU makeup
integrates all primary systems into sealed reactor vessel
7yr replaceable core unit lifetime approach t graphite lifetime
planned as 442 MWth (195 MWe)
4.1m wide core unit for easy transportation
alternate salt for low tritium and new gas approach
passive decay heat removal in situ w/out dump tanks
safety at forefront-cost innovation
how imsr power plant works - see slide 23
imsr consists of 2 parts for efficient industrial use
ismr heat and power facility (non nuclear parts)
ismr nuclear facility (nuclear systems)
ismr heat and power facility (non nuclear parts)
supplies heat and power for industrial end-user as a standalone facility
engineered to pair with nuclear facility
initially supplied with natural gas and grid electric power (including wind and solar gen)
flexibility in design as regulated by industry construction codes and standards
ismr nuclear facility (nuclear systems)
generates high quality heat from nuclear fission ( in op regulates natural gas and grid electric supply to back up role for heat and power facility)
transfers heat to heat and power facility
modular and standardized design as regulated by nuclear codes and standards
transformative power plant economics enables with iMSR
molten salt
lower CAPEX
Higher revenue (see slide 25)
pragmatic innovation of ISMR
7 yr core unit replacements allows advantages of graphite moderation and simplifies vessel and HX quals
inexpensive carrier salt to avoid tritium production of LiF
similar fuel economy to PWR and planned evolution such as eventual use of LiF that can reduce this to small fraction
passive decay heat removal featuring closed cycle natural circulation
designed with strongly negative temp coefficients for inherent load following (control rods not needed) and passive shutdown
shutdown rods are used but not credited for safety
soft spectrum allows 2% startup and 4.95% standard assay makeup
partial reuse of fuel salt minimizes used salt volume
waste management: common sense is often better than innovation
clearly stated the IMSR is proposing a once through fuel cycle (improved by direct partial reuse)
IMSR not picky - ability to self consume own production of Pu in used fuel ( makeup of LEU plus recycled Pu) Can close its won fuel cycle with aid of minor additions of LEU
Pu from CANDU or LWR can be consumed as part of makeup fuel
straight forward dry process
STILL NUCLEAR PROCESSING
waste management: waste from conditioning
on-site storage of used fluoride fuel during facility lifetime is not challenge
fluorides salt does have low solubility in water - not ideal for direct disposal options
vitrification possible but specialized methods require fluoride content
preferred - conversion ceramic mix through synroc technique of mineralization developed at ANSTO in Australia
Synroc Basis (See slide 29)
capable of stabilizing liquid or solid wastes
starting op for OPAL reactor Moly 99 production liquid wastes
DOE Record of Decision made in favour for several wastes including weapons grade Pu but not approved by congress
steps mechanically straightforward and engineered for full post contamination - waste mixed with proprietary additives to from minerals
review of world MSR Activities
imsr leader in msr space and all advanced reactors- clear leader in raising or private financing
euratom (france) decade long work on fluoride salt fast concept MSFR on thorium to U233 cycle
russia major program for fluoride fast system (MOSART) specialized for deconstruction of minor actinides (AM, Np) to be co-located with an existing PUREX facility to combine with MOX use for overall transuranic consumption
france (CEA) looking at chloride fast system on U-Pu cycle with similar goals of russia
us - first new msr in western world likely very small experimental reactor at ACU
china largest program begun in 2011 with 2 small MWth experimental reactor
gen V goals self assessment for IMSR : SUSTAINABILITY 1
resource sustainability
- good uranium usage with future ability to evolve to fraction LWR or CANDU needs
no uranium resource or SWU bottleneck (there is one for high assay LEU needed for almost all other advanced reactors)
gen V goals self assessment for IMSR : ECONOMICS 1
compete directly with other energy systems
- projections for nth of kind IMSR at 54$/MWh highly competitive
gen V goals self assessment for IMSR : ECONOMICS 2
finance risk similar to other energy systems
-projected facility costs are ordinarily financeable. current fleet relies on sovereign funding
gen V goals self assessment for IMSR : SUSTAINABILITY 2
minimize and manage waste and improve long term stewardship burden
- fuel waste volume, mass and activity on par with LWR per unit energy and superior to CANDU
-partial fuel salt reuse minimizes volume, carrier salt choice minimizes tritium production
- major player in Pu or TRU consumption by once through has much attractiveness
work towards conditioning used fuel to highly durable form for long term stewardship
work towards OPEX solutions for graphite alloys and OFF GLASSES
gen V goals self assessment for IMSR : safety 123
excel in saftey, core damage frequency, avoid of site emergency response
gen V goals self assessment for IMSR : proliferation resistance and physical protection
arguably the most proliferation resistance and best physical protection of any reactor
safeguards require different approach but clear path and OPEX of processing facilities
