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#1 2017-11-26 20:18:35

Oldfart1939
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Registered: 2016-11-26
Posts: 979

NASA and DOE to test kilopower nuclear reactor for space applications

In a press release reported by www.spaceflightinsider.com , earlier today, the collaboration between NASA and the Department of Energy to test a kilopower nuclear reactor was announced. The reactor uses a combination of liquid sodium and Stirling engines to develop electric power, according to the linked article.

http://www.spaceflightinsider.com/space … r-reactor/

Last edited by Oldfart1939 (2017-11-26 20:22:24)

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#2 2017-11-27 05:22:25

elderflower
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Registered: 2016-06-19
Posts: 558

Re: NASA and DOE to test kilopower nuclear reactor for space applications

a liquid sodium leak will catch fire, even in 100% CO2 and will continue to burn in Nitrogen. Just sayin'.

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#3 2017-11-27 09:24:53

Oldfart1939
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Re: NASA and DOE to test kilopower nuclear reactor for space applications

elderflower wrote:

a liquid sodium leak will catch fire, even in 100% CO2 and will continue to burn in Nitrogen. Just sayin'.

Uh....no. Sodium fires are extinguished with carbon dioxide extinguishers. Check the MSDS from Fisher Scientific. I've dealt with sodium fires in my own laboratory that way, as well and a metallic potassium fire. Where did you get your information?

Sodium is reactive with water and oxygen.

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#4 2017-11-27 11:41:24

elderflower
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Posts: 558

Re: NASA and DOE to test kilopower nuclear reactor for space applications

I was trained to put sand on it as it reacts vigorously with CO2 (they said) and with water. Maybe soda could smother it. Certainly magnesium will burn in CO2. I've seen that demonstrated and sodium is more reactive than magnesium.

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#5 2017-11-27 15:38:39

Oldfart1939
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Registered: 2016-11-26
Posts: 979

Re: NASA and DOE to test kilopower nuclear reactor for space applications

I've been unable to either write an equation wherein CO2 reacts with Na, or find a reference to one thereof. In my own experience while teaching organic laboratories in grad school, in addition to reading the MSDSs from the suppliers of Na, there is no evidence I've seen to offer any support to your statement. Potassium, K, is more reactive than Na, but the one K fire in my own laboratory was effectively extinguished by a CO2 extinguisher. Neither CO2 nor N2 will support any form of combustion. Period. That's why many extremely hazardous reactions are blanketed with either N2 or Ar. CO2 isn't used because there are various reactions wherein the intermediate formed could incorporate the elements into the reaction pathway leading to undesirable by-products.

I don't usually get this emphatic, but this is MY discipline; my doctorate is in chemistry. Sorry.

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#6 2017-11-27 17:02:36

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 10,650

Re: NASA and DOE to test kilopower nuclear reactor for space applications

SpaceNut wrote:

All the more reason to build on mars with insitu steel....

Back to Nuclear to which Nasa has continued to work on the kilopower system as a deliverable to mars.

NASA's Kilopower project to test providing energy to pioneering manned missions to Mars

http://www.firstpost.com/wp-content/upl … sa-380.jpg

The pioneering Kilopower reactor represents a small and simple approach for long-duration, Sun-independent electric power for space or extraterrestrial surfaces.

Offering prolonged life and reliability, such technology could produce from one to 10 kilowatts of electrical power, continuously for 10 years or more, Mason pointed out. The prototype power system uses a solid, cast uranium-235 reactor core, about the size of a paper towel roll. Reactor heat is transferred via passive sodium heat pipes, with that heat then converted to electricity by high-efficiency Stirling engines.

NASA’s Kilopower Program Can Help Colonize Mars

Kilopower hardware will be put through detailed, step-by-step testing which will last about 28 hours. The testing will be conducted at the U.S. Department of Energy’s (DOE) Nevada National Security Site.

    “The upcoming Nevada testing will answer a lot of technical questions to prove out the feasibility of this technology, with the goal of moving it to a Technology Readiness Level of 5. It’s a breadboard test in a vacuum environment, operating the equipment at the relevant conditions,

https://ntrs.nasa.gov/archive/nasa/casi … 012354.pdf

https://www.nasa.gov/directorates/space … Red_Planet

https://www.nasa.gov/sites/default/file … -06805.jpg

https://www.researchgate.net/publicatio … xploration

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#7 2017-11-27 17:25:29

SpaceNut
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Re: NASA and DOE to test kilopower nuclear reactor for space applications

Some fires involve metals that burn at a very high temperature and react violently with water. Firefighters try to smother metal fires with a material such as sand. They also would use the same extinguisher as that to one used on Lithium, tungsten  which is a class D.
Fire Safety and Fire Extinguishers

Those who work with flammable metals may also have a specialized Class D dry powder extinguisher for use on fires (in a pinch, a bucket of dry sand will do, but you really should have a Class D unit if you work with such materials).

Class D fires involve combustible metals, such as magnesium, titanium, potassium and sodium as well as pyrophoric organometallic reagents such as alkyllithiums, Grignards and diethylzinc. These materials burn at high temperatures and will react violently with water, air, and/or other chemicals. Handle with care!!

Now back to kilopower reactors to which we need a cooling material compatible with mars, low mass of launch and possibly from insitu materials.

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#8 2017-11-27 18:36:09

Oldfart1939
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Registered: 2016-11-26
Posts: 979

Re: NASA and DOE to test kilopower nuclear reactor for space applications

After one has read Robert Zubrin's book, Entering Space, it makes a person wonder why it has taken NASA this long to get on board with use of a nuclear power source compatible with both Mars surface exploration and the outer Solar system deep space probes. Zubrin equates available power with data transmission rates, so instead of the very expensive radioisotope decay thermal generators producing a mere 300 watts, we could have increased the data return from the Pluto probe by a factor of 100 to 1000, simply by using a reactor instead of a RTG.

Last edited by Oldfart1939 (2017-11-27 19:31:03)

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#9 2017-11-27 18:47:11

SpaceNut
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From: New Hampshire
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Re: NASA and DOE to test kilopower nuclear reactor for space applications

Not to meantion the size for most homes is under the 50kw size output and would last a life time on the fuel loading for most home ownership. The other part of that is mass production would cause the price per unit to drop such that you could afford to purchase one for the intended use.

So what is the total mass of a 100kw unit with cooling ready for use landing on mars surface?

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#10 2017-11-27 19:29:32

Oldfart1939
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Re: NASA and DOE to test kilopower nuclear reactor for space applications

Neither the output wattage nor the gross weight of the unit being tested was mentioned in the article referenced.

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#11 2017-11-27 21:09:33

kbd512
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Posts: 1,187

Re: NASA and DOE to test kilopower nuclear reactor for space applications

Oldfart1939,

The 100% scale design is 10kWe.  I believe they're testing a 10% scale design (1kWe) because that's the output power level that the test site can accommodate without modifications of any kind.  The 100% scale design will weigh 1,544kg complete (core, cooling, shielding, control).  It's almost entirely metal, with very little in the way of ceramics or plastics, so the masses of the individual components are fairly well known quantities.

NASA’s Kilopower Reactor Development and the Path to Higher Power Missions

Take note of how well KiloPower trades with PV and batteries, with respect to mass, even at landing sites favorable for using PV power.  That whole 50% further from the Sun than the Earth is turns out to be a real bummer.

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#12 2017-11-28 21:13:01

SpaceNut
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Posts: 10,650

Re: NASA and DOE to test kilopower nuclear reactor for space applications

A quick read of the link it appears that its more like a high temperature RTG with stirling generators.

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#13 2017-11-29 10:13:48

Oldfart1939
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Registered: 2016-11-26
Posts: 979

Re: NASA and DOE to test kilopower nuclear reactor for space applications

kbd512-

Not only is it unaffected by distance from the sun, but it also doesn't have a nighttime slumber party. It operates 25/7.

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#14 2017-11-29 11:42:13

elderflower
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Registered: 2016-06-19
Posts: 558

Re: NASA and DOE to test kilopower nuclear reactor for space applications

Oldfart1939 wrote:

I've been unable to either write an equation wherein CO2 reacts with Na, or find a reference to one thereof. .

Could it be 2Na + CO2 > Na2O + CO?
If it isn't really a vigorous reaction, perhaps they were just playing safe by saying to do the sand thing with all commonly met metal fires.

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#15 2017-11-29 12:50:03

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 2,712
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Re: NASA and DOE to test kilopower nuclear reactor for space applications

I actually have seen thin magnesium ribbon burn in CO2.  It's not very vigorous,  and very smoky (black soot). 

Magnesium also burns very vigorously indeed with water.  An accidental fire in a propellant lab cell long ago resulted from too much friction heat while coring a sample of a fuel rich solid propellant that was 65% magnesium.  As a motor,  it burned at around 2000 F,  producing a stream of polluted mag vapor for subsequent combustion with air.  In the work cell,  the accidental fire triggered the emergency water deluge,  which then sent combustion into the 5000-6000 F range.  We lost a lot of steel that day.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#16 2017-11-29 16:26:27

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: NASA and DOE to test kilopower nuclear reactor for space applications

Sodium/CO2 reaction was a concern in the development of heat exchangers for fast reactors using an S-CO2 secondary coolant.  But that was CO2 at high pressure and density.

Combustion isn't just about theoretical ability of two chemicals to react.  The combusting surface must release heat at sufficient rate to keep temperature high enough to maintain sufficient reaction rates, when radiated heat release is accounted for.  A CO2 atmosphere will have lower heat of combustion than oxygen, because two strong double bonds must be broken rather than just one.  Now account for the fact that the Martian atmosphere is 100 times thinner and it becomes highly unlikely that sodium could sustain combustion in the Martian atmosphere.

One of the biggest issues with sodium fast reactors is keeping air away from the primary circuit.  Not so much for fire, but for contamination.  Sodium oxide is highly abrasive and will rapidly scour the inside of the primary circuit of the reactor.

Last edited by Antius (2017-11-29 16:34:48)

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#17 2017-11-29 17:39:33

Antius
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From: Cumbria, UK
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Posts: 974

Re: NASA and DOE to test kilopower nuclear reactor for space applications

The 4+1 kilopower concept weighs about 9 tonnes.  That's half as much as the competing solar concept even at a good location for solar.

However, this is still a far cry from Zubrin's proposed 4te 100kwe reactor concept in Case for Mars.  NASA research from the early 90s suggested a mass of 6te for a 100kwe SP-100 reactor.

It would appear that these systems scale up much better than they down.

Last edited by Antius (2017-11-29 17:39:59)

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#18 2017-11-29 19:43:07

SpaceNut
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Posts: 10,650

Re: NASA and DOE to test kilopower nuclear reactor for space applications

Post #11 and 17 have quite the disparity of wattage and mass for the complete unit let alone being way under practicle usefull power levels....Seems like we need lots more work on this final design.

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#19 2017-11-30 10:46:11

kbd512
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Registered: 2015-01-02
Posts: 1,187

Re: NASA and DOE to test kilopower nuclear reactor for space applications

SpaceNut,

Antius posted the total tonnage for multiple units.  I posted the tonnage for a single 10kWe KiloPower unit.  That's probably where the disparity comes from.  I presume the 1,800kg includes the requirement for power cabling and conditioning equipment, rather than just the complete 10kWe output reactor, which would be 1,544kg.  In practice, these things would be set up some distance away from whatever it is that they're powering, and from each other, and likely partially buried.

Someone needs to do a trade study on what a mix of solar (no batteries) and nuclear power can provide, wherein solar panels produce during the day and nuclear provides constant cooling for the LOX/LCH4 plant and uses remaining capacity to produce or provide power.

If we had a pair of 10kWe fission reactors and 3,000kg worth of our best panels, then what are our daily production numbers?

Is there some way to use CO2 as both a coolant for the reactor and hot feed stock for SOXE in order to get rid of the heavy radiator panels?  For example, could a small CO2 compressor cool the reactor by driving the compressor with a working fluid or gas.  I'm not talking about collecting CO2 in a tank, I just want to know if it's possible to actively cool the unit, simultaneously compressing and heating CO2, and then feeding the hot CO2 to a SOXE cell heated by the reactor.  Think of it as a miniature turbofan / generator running atop the unit on magnetic bearings.  Instead of something 3.3m in diameter, we now have a package closer to 1.5m tall and .75m in diameter.

Everyone has seen the Vortex Powerfan, right?  Imagine that sitting on top of the reactor.  The heat pipe system from the reactor drives an internal turbine connected to the compressor.  The fan compresses the incoming CO2, heats it a bit in the process, and then feeds it to a SOXE cell that also uses heat from the reactor to keep the cell hot.  A smaller electric generator rotating on a common shaft provides electrical power for the cell.  The compressor forces most of the CO2 over a radiator to cool the reactor and bleeds the rest through the SOXE cell to produce CH4.  The reactor is 40kWt, so there is plenty of thermal power for heating.

We're making rocket propellant, not baby food, so if there's a little contamination from its brief pass through the reactor it should still be fine.  The reactor happens to be running at about the right temperature for the SOXE cell to use, and so presumably less electrical power would be required to keep the cell at the correct temperature.

Anyway, it's just a thought for getting us above 25% output efficiency for this particular use case.  Even if the cooling system fails entirely, the reactor won't melt down as a function of its surface area to volume ratio and the materials used.

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#20 2017-11-30 18:28:16

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 10,650

Re: NASA and DOE to test kilopower nuclear reactor for space applications

I think there is a way to use the heat from the heat pipes and up draft chimney design simular to the solar units but using the heat from the reactor to create the cooling and motion of the atmospher to create compression in the length of the chimney. I have seen designs that use the inward draft at the base of the chimney to create power.

solar_tower_03.gif

ave-chimney.png

lapaz_img1-550x301.jpg


https://solarthermalmagazine.com/learn- … aft-tower/

https://architecture.mit.edu/sites/arch … roject.pdf

Web.eng.hawaii.edu/~panos/444_09_5_7.pdf

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#22 2017-12-01 05:35:54

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: NASA and DOE to test kilopower nuclear reactor for space applications

kbd512 wrote:

Is there some way to use CO2 as both a coolant for the reactor and hot feed stock for SOXE in order to get rid of the heavy radiator panels?  For example, could a small CO2 compressor cool the reactor by driving the compressor with a working fluid or gas.  I'm not talking about collecting CO2 in a tank, I just want to know if it's possible to actively cool the unit, simultaneously compressing and heating CO2, and then feeding the hot CO2 to a SOXE cell heated by the reactor.  Think of it as a miniature turbofan / generator running atop the unit on magnetic bearings.  Instead of something 3.3m in diameter, we now have a package closer to 1.5m tall and .75m in diameter.

Everyone has seen the Vortex Powerfan, right?  Imagine that sitting on top of the reactor.  The heat pipe system from the reactor drives an internal turbine connected to the compressor.  The fan compresses the incoming CO2, heats it a bit in the process, and then feeds it to a SOXE cell that also uses heat from the reactor to keep the cell hot.  A smaller electric generator rotating on a common shaft provides electrical power for the cell.  The compressor forces most of the CO2 over a radiator to cool the reactor and bleeds the rest through the SOXE cell to produce CH4.  The reactor is 40kWt, so there is plenty of thermal power for heating.

We're making rocket propellant, not baby food, so if there's a little contamination from its brief pass through the reactor it should still be fine.  The reactor happens to be running at about the right temperature for the SOXE cell to use, and so presumably less electrical power would be required to keep the cell at the correct temperature.

Anyway, it's just a thought for getting us above 25% output efficiency for this particular use case.  Even if the cooling system fails entirely, the reactor won't melt down as a function of its surface area to volume ratio and the materials used.

A direct cycle nuclear gas turbine is an interesting idea.  The problem with using Martian atmospheric CO2 as a direct cycle reactor coolant is its low density – about 0.02kg/m3.  The specific heat (Cp)of CO2 at 250K is 791J/KgK; @300K it is 846J/KgK, which increases to 1075J/KgK at 600K.  Let's say about 0.9KJ/KgK on average, between 250-600K.  To remove 30kW of waste heat would require 0.095kg/s flowrate.  That means compressing 4.76m3 of atmosphere and blowing it through the reactor or heat exchanger every second.  Assume that we compress the CO2 to roughly 10bar.  Lets use the idea gas law to work out the power requirement:

PV=nRT

W = PdV

Rearranging and integrating gives:

W=P1V1 x (ln[V1]-ln[V2])

P1 = 0.6KPa, V1 = 4.76, V2 = 4.76 x (P1/P2) = 0.0029m3.

W=600x4.76 x (1.56--5.86) = 21.2kW

That's the amount of energy needed to compress an ideal gas.  The critical temperature of CO2 is 304K.  The inlet temperature is taken here to be 250K.  My compressibility chart only goes down to a TR of 1, for which compressibility factor is 0.2 at critical pressure.  So the actual compressor work could be reduced by a factor of 5 or more if intercooling is used – so compressor power ~4kW.  At night, the compressor would be even more efficient – in fact there may be a problem with dry ice deposits at low temperatures and high pressure.

Let's say the back-end of the turbine converts 60% of thermal power into mechanical work (24kW).  The compressor power is ~4kW.  So, a Martian direct cycle nuclear gas turbine could be up to 50% efficient from a mechanical power viewpoint and perhaps 48% efficient from an electrical power viewpoint.

I initially assumed a 40kW heat source producing 30kW of waste heat at 600K.  It would need to compress 4.76m3 of Martian air per second.  Let's assume we take advantage of Martian winds to deliver the required gas to the front of the compressor.  Since average Martian wind speed is about 5m/s, the frontal area of a 19kWe nuclear gas turbine would need to be about 1m2.  So a direct cycle nuclear gas turbine may be a more mass optimum idea than a closed cycle sodium cooled reactor with a radiator.  But there are a few obvious downsides:

1)    The bombardment of oxygen with neutrons generates N-16.  This has a half-life of 7 seconds, but is a powerful gamma emitter.  The gas turbine must be located some distance away from the settlement and preferably downwind;

2)    In the event of fuel damage, there is no containment.  Less of an issue on Mars than it would be on Earth, but could be a hazard to the crew or any future explorers visiting the site;

3)    The reactor would only be useful for surface missions on Mars, whereas the Kilopower concept is useful for a huge range of missions to solar system bodies.

Future nuclear reactors built on Mars could use a direct cycle CO2 coolant.  As CO2 absorbs very few neutrons, the fuel used could be natural uranium, probably canned in zircalloy cladding.  The moderator would either be graphite or heavy water and the fuel would be housed in pressure tubes, rather like a CANDU.

Integrating the reactor into the propellant plant makes sense from an energetic efficiency viewpoint, but may not be the cost optimum thing to do.  This is because (1) It is a very bespoke solution that requires a separate development programme; (2) Safety analysis for the reactor must concern itself with interactions between the reactor and propellant plant.  It may turn out to be cheaper to develop a nuclear electric plant and simply feed the ISRU plant with electric power remotely, rather than building the reactor into it.

Last edited by Antius (2017-12-01 07:24:27)

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#23 2017-12-01 19:52:00

kbd512
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Registered: 2015-01-02
Posts: 1,187

Re: NASA and DOE to test kilopower nuclear reactor for space applications

Antius,

The idea was to obtain significantly more useful work from the reactor.  Something similar to this has been done before in the nuclear powered aircraft program, which also required significant output from a compact and lightweight reactor.  Given the low quantity of energy we can extract from the Uranium metal before it starts to crack (1.314MWh over 15 years), I think the reactor should be significantly more efficient.  Slightly radioactive rocket fuel is a small price to pay for a compact, multi-purpose power plant that runs 24/7.  Here on Earth, nobody lives near a rocket fuel plant, nor should they on Mars, for obvious reasons.

Is there a way to do this without running the Martian atmosphere directly through the core?  In the nuclear aircraft program, I seem to recall that a heat exchanger with two sets of pipes in separate loops were used to transfer heat to drive the turbojets.  There would be some activation of the coolant, but it's in the core for a fraction of a second.

I believe those rough calculations show this is a feasible way of reducing the size and possibly the mass of the reactor.

Since everyone is always asking for exact masses and dimensions, I'll provide the link to NASA / LANL's document that provides this information:

KiloPower Project - KRUSTY Experiment Nuclear Design

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