[HN Gopher] Nuclear Reactor Simulator
       ___________________________________________________________________
        
       Nuclear Reactor Simulator
        
       Author : loopion
       Score  : 256 points
       Date   : 2023-12-04 09:50 UTC (1 days ago)
        
 (HTM) web link (dalton-nrs.manchester.ac.uk)
 (TXT) w3m dump (dalton-nrs.manchester.ac.uk)
        
       | loopion wrote:
       | Just played this game and honestly I'm impressed how it's made.
       | Interesting to see how it works even if it's simplified.
        
         | gus_massa wrote:
         | I tried, but I see only a loading page, it never starts.
        
         | adamredwoods wrote:
         | I was hoping I'd have to source the fuel, too, but they didn't
         | get into that.
        
           | foobarian wrote:
           | https://www.satisfactorygame.com/
        
       | OedipusRex wrote:
       | https://store.steampowered.com/app/1428420/Nucleares/
       | 
       | Another nuclear plant simulator, haven't played too much but
       | diving into later today with a friend.
        
         | nullhole wrote:
         | Wow, they got their own steam-themed domain name and
         | everything!
        
       | Elias-Braun wrote:
       | My first thought on the Title "Play and learn how a nuclear plant
       | works." this is was lead to this:
       | 
       | https://en.wikipedia.org/wiki/Windscale_fire
        
       | kingnothing wrote:
       | That's certainly a curious decision for this random site to ask
       | for my full name, age, gender, home town, and email address in a
       | form before showing the content.
       | 
       | No thanks.
        
         | johndhi wrote:
         | agreed, though note that you can click "skip."
        
         | FergusArgyll wrote:
         | 100% I wrote: city: noneof email: yourbusiness@gmail.com
        
           | user_7832 wrote:
           | Did you miss the skip button, or hover your cursor over why
           | they ask for the information?
           | 
           | The website is of a university, not Facebook. I doubt
           | overworked/underpaid researchers have any interest in
           | tracking people.
        
             | KomoD wrote:
             | > have any interest in tracking people
             | 
             | Yet it injects google analytics and asks for your personal
             | details?
        
         | forward1 wrote:
         | For me it's just a logo with an empty "Loading" bar, Firefox
         | 120 with strict tracking protection. Likely not worth my time
         | debugging.
        
       | John23832 wrote:
       | The reactor keeps tripping for me before I'm out of the first
       | "setup".
        
       | cratermoon wrote:
       | The very first nuclear plant simulator I ever played with was a
       | primitive text-based program, running on a DEC 11/780. To win the
       | game you had to average a certain number of MWh over each turn
       | (days). It seemed easy, just turn it on and let it run, but there
       | was a catch. The game simulated normal fatigue, meaning that the
       | longer it ran, the more likely something would go wrong. Also,
       | the higher power you ran, the faster things would fatigue. The
       | game required you to shut the reactor down for maintenance
       | periodically. The longer you ran it, the longer the maintenance
       | cycle. Success involved balancing uptime and power generation
       | with required maintenance downtime.
       | 
       | As an aside, I learned about how nuclear reactors generate power
       | when I was pretty young, so I was surprised to learn, just this
       | past year, that there were people who didn't know that nuclear
       | reactors just heat up water to make steam, same as any other
       | power plant. There's people out there who (quite reasonably,
       | IMNSHO) have a model of nuclear reactors directly generating
       | electricity from the reaction.
        
         | MadnessASAP wrote:
         | Might it have been Oakflat Nuclear Power Plant Simulator[1]
         | you're thinking of? I'm not aware of a version that ran on the
         | DEC but it might very well have existed and it sounds quite
         | similar. I can certainly credit it for developing my unhealthy
         | fascination with nuclear power. Also perhaps my unhealthy
         | tendency to push buttons and see what happens!
         | 
         | [1] https://www.mobygames.com/game/62490/the-oakflat-nuclear-
         | pow...
        
           | cratermoon wrote:
           | Nope, much more primitive than that. I played it on paper
           | terminal in the late 70s/early 80s.
        
         | dekhn wrote:
         | I didn't understand how nuclear reactors work until I was in
         | grad school and even then I was aghast. You'd think if we could
         | split an atom, we'd have a better way to make electricity than
         | to make steam to turn a turbine. Of course, there are RTGs, and
         | https://en.wikipedia.org/wiki/Betavoltaic_device
        
           | jtriangle wrote:
           | It's an incentives problem. Nearly all of the world's power
           | is generated by spinning a turbine with steam, so, we have a
           | direct, actionable, incentive to make that process as
           | efficient as possible, and we have indeed done this and
           | continue to do this. Modern steam turbines are wildly
           | efficient.
           | 
           | That doesn't mean that they are the only thing that _can_ be
           | efficient, just that they 're the current best option, and,
           | any other option is going to have to show immense promise in
           | order to get the funding to catch up to where we are now with
           | steam.
           | 
           | The only thing on my radar that bypasses steam entirely is
           | what Helion Energy is doing up in washington with their
           | experimental fusion devices. The basic idea being that you're
           | using a pulsed fusion reaction and intentionally not
           | containing it, instead using the energy produced to push back
           | on the magnetic containment and generate power. No idea if
           | it'll work out to be viable, but it at least makes sense on
           | paper.
        
       | mikewarot wrote:
       | I got Pi as a score (314) on my first run-through. I've played
       | simulators like this in the past, this is the first one that
       | required interacting between multiple parameters interactively
       | like this, well done!
        
       | staplung wrote:
       | Seems impossible to make it meltdown and explode. Shutting off
       | the coolant just makes it automatically SCRAM. No incoming
       | tsunamis threaten to swamp your diesel generators, no xenon pits
       | to slowly climb out of. Booooring. ;-)
        
         | Obscurity4340 wrote:
         | My biggest beef with nuclear (and I've always said this) is its
         | just so unsexy. No mushroom shapes, no passionate explosions
         | followed by restful oblivion at the end. Its just reliable and
         | faithful and keeps on pluggin' away. I like to live a little
         | dangerously, and you should too!
        
           | jplrssn wrote:
           | I'm not so sure. There was a news article today about a leaky
           | storage site for nuclear waste, coincidentally not too far
           | from Manchester. [0] There are more ways than explosions to
           | cause ecological devastation.
           | 
           | [0] https://www.theguardian.com/business/2023/dec/05/sellafie
           | ld-...
        
           | dekhn wrote:
           | Nuclear isn't just reliable and faithful and just keeps on
           | plugging away- the modern reactor designs require
           | extraordinary engineering to be reliable and require
           | continuous maintanence and monitoring.
        
             | Obscurity4340 wrote:
             | That too, I don't normally indulge in high-maintenance ;)
        
         | rzzzt wrote:
         | There are some user-submitted levels in The Powder Toy that
         | cover a subset of your requirements:
         | https://powdertoy.co.uk/Browse/View.html?ID=5170
        
         | francisofascii wrote:
         | They should have a "Chernobyl mode" where it CAN happen. Add
         | graphite tips to the control rods (or whatever else was the
         | problem)
        
         | benjojo12 wrote:
         | I am one of the programmers that worked on this port back in
         | 2013, I can assure you that we (the programmers) also wanted to
         | make a scenario where the plant would explode, however given it
         | was designed to promote nuclear technology to school children
         | (generally speaking), the people funding the project were not
         | so keen to have nuclear technology shown off in that way!
        
           | einpoklum wrote:
           | > however given it was designed to promote nuclear technology
           | to school children
           | 
           | ... and that was not a problem for you ethically?
        
         | krelas wrote:
         | Yeah at least let us put graphite tips on the control rods.
        
       | dctoedt wrote:
       | No time to check this out now, but I'll be interested in
       | reactions from my fellow (ex) Navy nukes ....
        
         | niekze wrote:
         | I gotta be both the reactor operator _and_ the throttleman?!?
        
         | djmips wrote:
         | I have a friend who was a 'Navy nuke' but was discharged for
         | wiring up the superbowl for the crew while on duty. You don't
         | see THAT in the simulators!
        
       | weinzierl wrote:
       | I must seem completely seem out of place nowadays, but I actually
       | learned that in school in Germany. Not to the nitty gritty
       | detail, of course, but we spent a double lesson on every reactor
       | type. What I've taken from it and remember to this day is that
       | you usually can determine the reactor type from the shape of the
       | building.
        
         | Symbiote wrote:
         | Here's the BBC's revision guide for 16 year olds in England and
         | Wales. Only one reactor type:
         | 
         | https://www.bbc.co.uk/bitesize/guides/zyqnrwx/revision/2
        
       | hot_gril wrote:
       | It's neat. What exactly am I controlling with the steam generator
       | lever, the pump at the bottom? With the control rods it's more
       | obvious since they move on the diagram.
        
         | scrlk wrote:
         | You're controlling the flow of water through the steam
         | generator.
        
       | barkingcat wrote:
       | The Music is awesome.
       | 
       | reminds me of
       | 
       | https://www.youtube.com/watch?v=rEgrn7vopZU
        
       | djmips wrote:
       | This is cool and takes me back to one of the first cool sim games
       | I ever played as a child. Muse software's Three Mile Island for
       | the Apple II. Mastery of this sim was an amazing feeling at the
       | time.
       | 
       | Manual https://archive.org/details/ThreeMileIslandAppleIIManual
       | 
       | Game (Note view 7 save/reset state seems to be broken - avoid)
       | 
       | https://archive.org/details/a2_Three_Mile_Island_Special_Ver...
        
         | alyandon wrote:
         | Was that the one where you had to perform maintenance on the
         | heat exchanger and coolant loops to prevent fouling?
        
           | djmips wrote:
           | Yes, planning maintenance out into the future was a huge part
           | of mastering the sim.
        
             | alyandon wrote:
             | What an awesome game that was - even more awesome to know
             | there are people that remember it. :-D
        
       | rzzzt wrote:
       | My favorite classic NPP simulator is SIMULA-C by Ralph Reuhl. I'm
       | only finding this report [1] (from my comment history, hah), but
       | both the C source code as well as MS-DOS executables were
       | available. Back when I knew what the URL is, the Wayback Machine
       | could fetch the .exe files but not the source archive.
       | 
       | Anyone remember this one? A screenshot can be found in the PDF at
       | the end.
       | 
       | [1] https://inis.iaea.org/search/search.aspx?orig_q=RN:29043408
        
       | Buttons840 wrote:
       | This reminds me of a game idea I have.
       | 
       | I want to build a game where players assemble various components
       | into engines or systems. Building the required system is itself a
       | bit of a puzzle, but then players must also demonstrate that they
       | can control the system using sensors and switches, etc, despite
       | failures of various components. Can you build a reactor? If
       | something breaks, can you figure out what broke using the sensors
       | you placed? Can you fix the system with the switches you placed?
       | 
       | My favorite thing about flight simulators was always the
       | simulated avionics. I get to click simulated buttons and watch
       | simulated gauges, I love it.
        
         | rzzzt wrote:
         | Injured Engine is a similar game where you have to maintain a
         | car engine and repair any part that breaks due to wear (but
         | don't need to put it together):
         | https://en.wikipedia.org/wiki/Injured_Engine
        
         | abraae wrote:
         | When I studied "computer engineering" (a very long time ago)
         | one of our classes involved hardware debugging on PDP-8
         | minicomputers (which were old even at the time).
         | 
         | The lecturer would use a craft knife to make a tiny cut in a
         | PCB trace somewhere in the machine. Then we would write
         | debugging code, use oscilloscope and multimeter etc. to isolate
         | the failure. A blob of solder repaired it.
         | 
         | That was such great fun and some powerful learning. It would be
         | great if there was an online game/logic simulator that could do
         | something similar.
        
           | Levitating wrote:
           | Wow that must've been really fun!
        
         | J5892 wrote:
         | It's not really similar to your idea, but your idea unlocked a
         | memory of playing Gizmos and Gadgets as a kid.
         | 
         | Edit: So I decided to go and play it on an online archive site.
         | It's just as fun as I remember.
        
         | spydum wrote:
         | I mean that's kind of what some security CTFs are built this
         | way. They build a working system/application with some flaws,
         | and you find them and break them. Sometimes in the more
         | advanced CTFs like NetWars, you have to also fix the flaws and
         | defend against your competitors.
        
       | benjojo12 wrote:
       | How bizarre! Me and a colleague ( who's still a good friend )
       | wrote this in like, 2012-2013! Well, more accurately we ported
       | this from a older Delphi/Pascal program that was using raw OpenGL
       | calls ( a legitimately very impressive bit of code for what it
       | was written in ) into WebGL ( a relatively new piece of
       | technology at the time )
       | 
       | The primary reason for porting this to a modern platform was ( as
       | far as I understood ) so that it could be run on interactive
       | events for schools and such. It's definitely more optimised for
       | fun than realism. I remember a few good memories of various
       | people who were actually nuclear engineers complaining that
       | realistically the demand would never change that fast on any
       | commercial nuclear power plant!
        
         | jtriangle wrote:
         | I think the idea is that this is sped up significantly.
         | 
         | Also, in real life, there's not a human twisting the dials for
         | "more steam" or "more reactor", that's undoubtedly handled with
         | PIC controllers and software. Humans are just keeping an eye on
         | things and running checklists when the software doesn't respond
         | properly.
        
       | niekze wrote:
       | Former US Navy submarine nuclear reactor operator here.
       | 
       | Adjusting the steam output was kind of strange. On a submarine,
       | the steam used to propel the submarine dwarfs all the other steam
       | loads. As a result, there's a throttleman who controls that.
       | 
       | Even though this simulation is simplified, it's not too bad. It
       | does hide some of the really interesting aspects of a water
       | cooled/moderated nuclear reactor. The most interesting thing is
       | that water makes the reactor self-regulating because of its
       | negative temperature coefficient of reactivity. I'll explain.
       | 
       | When a uranium-235 atom absorbs a stray neutron, it becomes
       | unstable and splits. This releases more neutrons. Very few of
       | these neutrons will be absorbed by surrounding uranium-235 atoms.
       | This is a good thing. Most will escape the fuel, and some will
       | bounce around in the surrounding water. This slows the neutrons
       | down, and some of them will bounce back into the fuel to be
       | absorbed for more fission reactions.
       | 
       | Let's say 1,000 fission reactions occur. If the result is that
       | 800 neutrons from those fission reactions are absorbed by other
       | uranium-235 atoms, you'll have 800 more fission reactions. The
       | reactor is sub-critical as the reaction will not be self-
       | sustaining.
       | 
       | If 1,000 fissions cause 1,200 neutrons to be absorbed and react,
       | you'll have 1,200 resulting fission reactions. The reactor is
       | super-critical as the number of fissions will increase.
       | 
       | If 1,000 fissions occur and the result is that 1,000 neutrons are
       | absorbed and cause 1,000 more fission reactions, the reactor is
       | critical. "The reactor is critical" means the number of fission
       | reactions is self-sustaining and neither increasing nor
       | decreasing.
       | 
       | How can we affect how many neutrons bounce back into the fuel? We
       | can change the density of the water. It makes sense if you thing
       | about it. The denser the water, the more likely neutrons will hit
       | a water molecule and head back into the fuel.
       | 
       | How can we change the density of the water? We change the
       | temperature of the water. If the water is colder, it is denser
       | and the more likely neutrons will bounce back into the fuel.
       | 
       | How do we change the temperature of the water? We pull more/less
       | heat of out it by using more/less steam.
       | 
       | Putting this all together, as steam demand goes up, more heat is
       | pulled out of the water. This causes colder water to enter the
       | reactor. Colder water will reflect more neutrons. More neutrons
       | means more fission. More fission means more heat. More heat means
       | warmer water and this will attenuate the increase in fission
       | until an equilibrium is reached.
       | 
       | If you're creating too much power, the coolant temperature will
       | increase and the power output will lower. If you're creating too
       | little power, the coolant temperature will decrease and the power
       | output will rise. That's why water is a great coolant/moderator:
       | its negative temperature coefficient of reactivity.
        
         | tiffanyg wrote:
         | Thank you so much for sharing that! Beautiful / elegant and
         | simple!
         | 
         | It's been decades since I looked at any of the details involved
         | in any of the various types of reactors that have been
         | designed. When I did, in the past, I hadn't even encountered
         | concepts like "control theory" or spent any time with the
         | subject matter of "systems engineering" or even "chemical
         | engineering". I.e., areas where you start thinking about how to
         | combine all of the different simple "laws"* and properties and
         | such of energy and matter to create "robust" (ideally) or even
         | just practical "systems".
         | 
         | Although I had read about the Chernobyl disaster, and "run-
         | away" that occurred - the massive volumes of water being pumped
         | in, partly as a result of such levels, at near boiling ... the
         | steam voids, etc. I'm not entirely sure whether I really
         | encountered the point about temperature and density, but,
         | certainly, it didn't 'click' quite the way it did now when I
         | read your description.
         | 
         | I love this kind of stuff - the "how it all fits together" from
         | what can otherwise be these seemingly dry / 'dead' "laws" and
         | such that can seem too simple / narrow / etc. to do much of use
         | with - even if your teachers spend as much time as possible
         | giving you homework questions etc. that certainly seem
         | practice-oriented - but who gives a rat's-keister about whether
         | comparing the weight of a duck to a putative witch might
         | establish flammability and hence witchcraft when they're 15,
         | right? ;)
         | 
         | * Simplified models describing various types of matter and
         | physical processes - models that are valid (for some definition
         | of ... as the mathematicians &/ Humpty-Dumpty [Alice in
         | Wonderland / Lewis Carroll] might say) given certain
         | assumptions / pre-conditions (on scale, frame of reference,
         | etc.)
        
           | ok_dad wrote:
           | The Chernobyl disaster was partly because the design was
           | graphite moderated, which does not have the safety that water
           | does since it's not self regulating due to the GPs
           | explanation about that above. When the reactor started to go
           | supercritical, it was reinforced by the moderator working
           | better to create more neutrons, the opposite of what you'd
           | want.
        
             | tiffanyg wrote:
             | Excellent point - you are 100% correct, parent comment etc.
             | were specifically about water-moderated types.
             | 
             | I was too grabbed by some of the later description and just
             | connected it somewhat haphazardly to not very organized or
             | accurate info rattling around in my head from years ago.
             | 
             | Thanks for pointing that out!
        
             | paulnpace wrote:
             | Additionally, they were ordered to disable all safety
             | mechanisms and run the reactor in a known unsafe condition,
             | causing a massive long-term disaster in... the Ukraine.
             | 
             | The way I attempt to explain the difference between the
             | negative and positive coefficient of reactivity is it's
             | like one car accelerates by pressing the gas pedal and the
             | other car has an engine running WFO and all you ever do is
             | press the brake pedal. It isn't a perfect analogy, but I
             | think it gets the general concept across.
        
               | dgroshev wrote:
               | As an aside, "the Ukraine" has mildly offensive
               | connotations. https://en.wikipedia.org/wiki/Name_of_Ukrai
               | ne#English_defini...
        
         | paulnpace wrote:
         | > If the water is colder, it is denser and the more likely
         | neutrons will bounce back into the fuel.
         | 
         | My memory is that the denser water thermalizes the neutrons in
         | a shorter period of time and this is why reactivity is
         | increased.
        
         | Ericson2314 wrote:
         | I know land vs sea is different, but after decades of nuclear
         | submarines working beautifully it's just so sad to me we don't
         | have abundant SMRs by now.
        
           | exabrial wrote:
           | Agree... although I do believe part of the problem is that a
           | lot of US Naval reactors run on weapons grade uranium.
           | Someone here probably knows more about this.
        
             | niekze wrote:
             | The fuel in US Naval nuclear reactors is enriched to a much
             | higher percentage than civilian reactors due to size and
             | longevity considerations. It has to fit the ship and
             | refuels take months/years. A ship undergoing a refuel isn't
             | a ship you can use.
             | 
             | In a civilian plant, you can have multiple reactors and
             | refuel them on a rotating schedule to avoid downtime,
             | having a larger reactor vessel isn't a problem, and all of
             | that is also going to be less expensive - which is a huge
             | factor.
        
           | shagie wrote:
           | I am of the understanding that part of this is because there
           | are different profit margins in mind with a civilian reactor
           | generating power to be sold and a military reactor powering a
           | vessel.
           | 
           | When that is combined with deregulation (or an anti-
           | regulatory mindset) where things like insulation on water
           | intake is deferred or ignored because it impacts the
           | economics of the power plant, then building one becomes
           | difficult.
        
         | 39 wrote:
         | Dope explanation!
        
         | gosub100 wrote:
         | I have a question about the control rods: are they normally
         | removed completely when you want the reactor to run? If they
         | are partially inserted, that would seem to mean that the
         | reactor fuel would burn unevenly, with the pellets at the
         | bottom used up sooner than the top. Is that true, and is it a
         | problem that has mitigations?
        
           | niekze wrote:
           | The rods are not completely removed. Control rods ravenously
           | gobble up free neutrons. As they're pulled up, more neutrons
           | get to the uranium. You are correct in that fuel at the
           | bottom is used up sooner. As more fuel is used, the rods will
           | have to be pulled up higher than they were before for the
           | same effect. The design takes this into account.
        
           | philipkglass wrote:
           | Regardless of control rod use, there is non-uniform burnup.
           | Fuel manufacturers use different enrichment levels in fuel
           | pellets throughout the length of the rod to partially
           | compensate for the non-uniformity.
           | 
           |  _The majority of PWR fuel assemblies have similar axial-
           | burnup shapes - relatively flat in the axial mid-section
           | (with peak burnup from 1.1 to 1.2 times the assembly average
           | burnup) and significantly under-burned fuel at the ends (with
           | burnup of 50 to 60% of the assembly average). Figure 1 shows
           | a representative PWR axial burnup distribution. As is
           | typical, the burnup is slightly higher at the bottom of the
           | assembly than at the top. This variation is due to a
           | difference in the moderator density. The cooler (higher
           | density) water at the assembly inlet results in higher
           | reactivity (which subsequently results in higher burnup) than
           | the warmer moderator at the assembly outlet._
           | 
           | Quoted from "ORNL/TM-1999/246: Review of Axial Burnup
           | Distribution Considerations for Burnup Credit Calculations"
           | 
           | https://www.osti.gov/servlets/purl/763169
        
           | vectoral wrote:
           | Former submarine nuke with a masters in NucE here (it's fun
           | to see us come out of the woodwork for this).
           | 
           | Rods are always in the core. To start a reactor that is shut
           | down (with the rods are all the way on the bottom), you
           | withdraw them slowly until the reactor is self-sustaining.
           | From there, you increase power by increasing steam demand (as
           | described in the parent comment above) and continue raising
           | rods to increase or maintain temperature.
           | 
           | When the reactor is operating at power, the control rods are
           | used primarily to 1) control steady state coolant temperature
           | and 2) provide a safe and reliable way to shut the reactor
           | down quickly (by dropping them to the bottom of the core --
           | this is called a reactor scram). If you have a short-duration
           | power transient for any reason, you can "shim" the rods in to
           | prevent a power spike that might cause a protective action to
           | occur (you shouldn't really ever have to do this except for
           | during emergency drills).
           | 
           | If the rods were drawn outside of the fuel region at power,
           | they wouldn't be able to absorb any neutrons and wouldn't
           | give you any way to control temperature or power. During some
           | specific maintenance when the reactor is shut down, you
           | sometimes might pull one rod further out for testing.
           | 
           | Your question on uneven burning of fuel is insightful. That
           | can happen, and it's caused by an uneven neutron flux (# of
           | neutrons traveling through a unit surface area per unit time)
           | distribution. The core designers take rod positioning into
           | account when determining how to distribute fuel throughout
           | the core in order to maintain a "flat" flux profile.
        
       | spacecadet wrote:
       | Yeees, bring on the simulation tools.
        
       | Apocryphon wrote:
       | This reminds me that I have a disc somewhere of a ton of
       | different Java applets, one of which was a basic nuclear reactor
       | simulator. There was a dining philosophers one too.
        
       | exabrial wrote:
       | 12 year old me went in with a single purpose: make it go bang.
       | 
       | Damn safety systems are messing up my fun.
        
       | goodpoint wrote:
       | There's a bit of propaganda going on...
        
         | 39 wrote:
         | Please explain
        
       | einpoklum wrote:
       | "Pro nuclear power propaganda game for kids"
       | 
       | Did you know? It's perfectly clean and very safe! And is in no
       | way related to the UK's nuclear weapons program either! And don't
       | you worry your pretty little head about the price.
        
         | EdwardDiego wrote:
         | How is it propaganda?
        
       | nickt wrote:
       | Here's a link to a video of a ZX81 version, in a similar vein.
       | 
       | https://youtu.be/tB6CC8UbJLU
        
       | yason wrote:
       | The only destined purpose of a nuclear reactor simulator is to
       | gradually let a massive meltdown happen, with gauges slowly
       | increasing in tandem with thrill in anticipation of the upcoming
       | drama and fireworks until you discover a bit too late that...
       | it's too late.
        
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       (page generated 2023-12-05 23:00 UTC)