7 ms·

It was a partial meltdown in a pressurized water reactor, it cannot be compared to Chernobyl, it's a completely different technology. PWRs can't explode like wh

It was a partial meltdown in a pressurized water reactor, it cannot be compared to Chernobyl, it's a completely different technology. PWRs can't explode like what happened in Chernobyl.

redprince 3y ago
PWR is a "Pressurized Water Reactor" using (light) water under pressure as the primary coolant. The Chernobyl block #4 RBMK-1000 was certainly a PWR. While the precise mechanism by which the #4 reactor in Chernobyl was destroyed in 1986 was rooted in the flawed design combined with unsafe operation, this does not mean that other reactor designs cannot fail catastrophically with loss of containment and release of radioactive material. Particularly when operated outside of their specification through operator error, accidents or a combination thereof.
- lupusreal 3y ago
  RBMKs are not PWRs, full stop. You're completely wrong. These terms have clear, precise established meanings, you cannot redefine them willy nilly to suit your rhetorical needs.
- beefman 3y ago
  RBMK is not considered a PWR because it is graphite-moderated. Most reactors are classified first by their moderator. PWRs and BWRs are both LWRs, moderated by light water, as opposed to HWRs moderated by heavy water, or graphite-moderated reactors like RBMK, or fast reactors which have no moderator at all. Any reactor can fail and any can be operated safely. The reactivity coefficients of RBMK made it harder to control, perhaps, than a PWR. Modifications made after the Chernobyl accident have improved this. The main issue with Chernobyl 4 was its lack of a containment building. Even so, the response was an over-reaction that made the situation worse.
  - hef19898 3y ago
    RMBKs are an unsafe design. Chernobyl No. 4 was build in an unsafe manner and operated in an unsafe manner. Not sure which response to the accident was an over-reaction in your opinion so.
ChatGTP 3y ago
Isn’t that what physicists thought about the Chernobyl reactor ? Then it exploded ?
- olivermuty 3y ago
  If the HBO show had the science somwhat correct, then the operators did everything they could to make it go boom. In failure modes already defined and warned about.
  - falserum 3y ago
    Gist was, that operator strongly believed hard break was always available.
    - hef19898 3y ago
      That, and the fact that it wasn't was not communicated. The necessary assessments have not been done during Chernobyl No. 4s commissioning, hence not counter measures have beem defined and put in the procedures. The RBMK chief engineering org wanted to adress the incident in Lithuania, and informed operators and authorities about that intention. Chief engineering didn't follow up so, and nobody bothered asking where the announced measures and procedures were. In the end the operators of Chernobyl No. 4 were the fucked ones, their procedures were incomplete, sometimes dangerously wrong. Leadership, incl. Dyatlov, failed to put a safety culture in place. The reactor design was not well understood, operating characteristics at below 50% capacity were never even analyzed or modelled, and inheretly unsafe (missing sensors, bad control rod design and operating procedures...). And the night shift wasn't even briefed on the test to be conducted. One of the conclusions of INSAG-7 was, that the accident could even have happened with properly designed control rods, coolant failure could have led to the same accident. If your equipment is so inherently unstable and fragile, operating procedure, training and operators have to compensate. None of those measures was taken. Heck, in some circunstances RBMK operators had to conduct up to 1,000 manual operations per hour (!) to keep the reactor stable. And by the way, the RBMK design didn't even meet Soviet design and safety requirements applicable in 70s when those reactors were designed. A complete clusterfuck. The circumstances allowing said clusterfuck still exist everywhere, in all countries, industries and organisations to this day.
lazide 3y ago
Something like 20 tons (!) of fuel rods, almost the entire load, melted. [https://commons.m.wikimedia.org/wiki/File:Graphic_TMI-2_Core_End-State_Configuration.png#mw-jump-to-license https://commons.m.wikimedia.org/wiki/File:Graphic_TMI-2_Core...] It took years to find that out though. The containment vessel held, and most of the radiation released was in the form of xenon and krypton gas vented from the reactor. “ It was later found that about half the core had melted, and the cladding around 90% of the fuel rods had failed,[21][76] with 5 ft (1.5 m) of the core gone, and around 20 short tons (18 t) of uranium flowing to the bottom head of the pressure vessel, forming a mass of corium.[77] The reactor vessel—the second level of containment after the cladding—maintained integrity and contained the damaged fuel with nearly all of the radioactive isotopes in the core.” Definitely not Chernobyl, but it was a significant amount of damage to the reactor. It was totaled.
- Animats 3y ago
  There is a lot to be said for big, strong containment vessels. Fukishima's was too small and overpressure broke it open. Chernobyl didn't have one. Three Mile Island had a good one. Many of the "small modular reactor" schemes say they don't need a big, strong, expensive containment vessel because, reasons. You can read those arguments for NuScale in NRC documents. The prototype was going to be built at the Idaho National Laboratory, formerly the National Reactor Testing Station, which is in outer nowhere, just in case.
  - lazide 3y ago
    If I remember correctly, part of the issue has been supply chain - the equipment necessary to forge the large steel parts necessary for these containment vessels are few and far between - and now all foreign. [https://www.newequipment.com/plant-operations/article/21921859/us-cedes-capability-for-largest-nuclear-forgings https://www.newequipment.com/plant-operations/article/219218...]
  - jasonwatkinspdx 3y ago
    Just to be fair, a big reason Nuscale went to the Idaho site is it'd streamline approval.
natmaka 3y ago
> PWRs can't explode like what happened in Chernobyl. No, sadly. PWR's sure can explode (due to hydrogen, vapor...). The root causes will not be identical to Chernobyl's causes, and the containment will probably limit leaks for a while (theoretically at least a few days), but they sure can explode. It also happened at Fukushima. Some protective measures are PACs and containment, however nothing can guarantee that an explosion won't happen, nor that dangerous radionuclides won't leak outside the plant. PAC: https://en.wikipedia.org/wiki/Passive_autocatalytic_recombiner https://en.wikipedia.org/wiki/Passive_autocatalytic_recombin... Containment: https://en.wikipedia.org/wiki/Containment_building https://en.wikipedia.org/wiki/Containment_building

It was a partial meltdown in a pressurized water reactor, it cannot be compared to Chernobyl, it's a completely different technology. PWRs can't explode like what happened in Chernobyl.

redprince 3y ago

PWR is a "Pressurized Water Reactor" using (light) water under pressure as the primary coolant. The Chernobyl block #4 RBMK-1000 was certainly a PWR. While the precise mechanism by which the #4 reactor in Chernobyl was destroyed in 1986 was rooted in the flawed design combined with unsafe operation, this does not mean that other reactor designs cannot fail catastrophically with loss of containment and release of radioactive material. Particularly when operated outside of their specification through operator error, accidents or a combination thereof.

lupusreal 3y ago
RBMKs are not PWRs, full stop. You're completely wrong. These terms have clear, precise established meanings, you cannot redefine them willy nilly to suit your rhetorical needs.
beefman 3y ago
RBMK is not considered a PWR because it is graphite-moderated. Most reactors are classified first by their moderator. PWRs and BWRs are both LWRs, moderated by light water, as opposed to HWRs moderated by heavy water, or graphite-moderated reactors like RBMK, or fast reactors which have no moderator at all. Any reactor can fail and any can be operated safely. The reactivity coefficients of RBMK made it harder to control, perhaps, than a PWR. Modifications made after the Chernobyl accident have improved this. The main issue with Chernobyl 4 was its lack of a containment building. Even so, the response was an over-reaction that made the situation worse.
- hef19898 3y ago
  RMBKs are an unsafe design. Chernobyl No. 4 was build in an unsafe manner and operated in an unsafe manner. Not sure which response to the accident was an over-reaction in your opinion so.

ChatGTP 3y ago

Isn’t that what physicists thought about the Chernobyl reactor ? Then it exploded ?

olivermuty 3y ago
If the HBO show had the science somwhat correct, then the operators did everything they could to make it go boom. In failure modes already defined and warned about.
- falserum 3y ago
  Gist was, that operator strongly believed hard break was always available.
  - hef19898 3y ago
    That, and the fact that it wasn't was not communicated. The necessary assessments have not been done during Chernobyl No. 4s commissioning, hence not counter measures have beem defined and put in the procedures. The RBMK chief engineering org wanted to adress the incident in Lithuania, and informed operators and authorities about that intention. Chief engineering didn't follow up so, and nobody bothered asking where the announced measures and procedures were. In the end the operators of Chernobyl No. 4 were the fucked ones, their procedures were incomplete, sometimes dangerously wrong. Leadership, incl. Dyatlov, failed to put a safety culture in place. The reactor design was not well understood, operating characteristics at below 50% capacity were never even analyzed or modelled, and inheretly unsafe (missing sensors, bad control rod design and operating procedures...). And the night shift wasn't even briefed on the test to be conducted. One of the conclusions of INSAG-7 was, that the accident could even have happened with properly designed control rods, coolant failure could have led to the same accident. If your equipment is so inherently unstable and fragile, operating procedure, training and operators have to compensate. None of those measures was taken. Heck, in some circunstances RBMK operators had to conduct up to 1,000 manual operations per hour (!) to keep the reactor stable. And by the way, the RBMK design didn't even meet Soviet design and safety requirements applicable in 70s when those reactors were designed. A complete clusterfuck. The circumstances allowing said clusterfuck still exist everywhere, in all countries, industries and organisations to this day.

lazide 3y ago

Something like 20 tons (!) of fuel rods, almost the entire load, melted. [https://commons.m.wikimedia.org/wiki/File:Graphic_TMI-2_Core_End-State_Configuration.png#mw-jump-to-license https://commons.m.wikimedia.org/wiki/File:Graphic_TMI-2_Core...] It took years to find that out though. The containment vessel held, and most of the radiation released was in the form of xenon and krypton gas vented from the reactor. “ It was later found that about half the core had melted, and the cladding around 90% of the fuel rods had failed,[21][76] with 5 ft (1.5 m) of the core gone, and around 20 short tons (18 t) of uranium flowing to the bottom head of the pressure vessel, forming a mass of corium.[77] The reactor vessel—the second level of containment after the cladding—maintained integrity and contained the damaged fuel with nearly all of the radioactive isotopes in the core.” Definitely not Chernobyl, but it was a significant amount of damage to the reactor. It was totaled.

Animats 3y ago
There is a lot to be said for big, strong containment vessels. Fukishima's was too small and overpressure broke it open. Chernobyl didn't have one. Three Mile Island had a good one. Many of the "small modular reactor" schemes say they don't need a big, strong, expensive containment vessel because, reasons. You can read those arguments for NuScale in NRC documents. The prototype was going to be built at the Idaho National Laboratory, formerly the National Reactor Testing Station, which is in outer nowhere, just in case.
- lazide 3y ago
  If I remember correctly, part of the issue has been supply chain - the equipment necessary to forge the large steel parts necessary for these containment vessels are few and far between - and now all foreign. [https://www.newequipment.com/plant-operations/article/21921859/us-cedes-capability-for-largest-nuclear-forgings https://www.newequipment.com/plant-operations/article/219218...]
- jasonwatkinspdx 3y ago
  Just to be fair, a big reason Nuscale went to the Idaho site is it'd streamline approval.

natmaka 3y ago

> PWRs can't explode like what happened in Chernobyl. No, sadly. PWR's sure can explode (due to hydrogen, vapor...). The root causes will not be identical to Chernobyl's causes, and the containment will probably limit leaks for a while (theoretically at least a few days), but they sure can explode. It also happened at Fukushima. Some protective measures are PACs and containment, however nothing can guarantee that an explosion won't happen, nor that dangerous radionuclides won't leak outside the plant. PAC: https://en.wikipedia.org/wiki/Passive_autocatalytic_recombiner https://en.wikipedia.org/wiki/Passive_autocatalytic_recombin... Containment: https://en.wikipedia.org/wiki/Containment_building https://en.wikipedia.org/wiki/Containment_building