Talk:Iodine pit

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Disputed claim: Chernobyl operators did not know the reactor was poisoned
The article says operators were "unaware of the poisoned condition of the reactor", a frankly incredible claim. All reactor operators are intimately familiar with xenon poisoning, which is a fundamental aspect of reactor operation, especially startup. Even more so with large reactors which (as the article already notes) are subject to oscillations due to non-uniform poisoning.

The problem was that they were trying to restore the reactor to operation despite the (known) poisoning. Reading the INSAG-7 report, poisoning is mentioned in passing (e.g pp. 63–64 "it proved necessary for some of the ORM rods to be withdrawn in order to compensate for the additional negative reactivity caused by xenon poisoning of the core at low power"), but it appears to be so understood by the writers and their intended audience that it's not described in detail; the analysis focuses on the unstable state engendered by the recovery efforts. INSAG mostly talks about the core state in terms of delayed neutron fraction, β, and reactivity margin.

Unless someone objects, I'm going to rewrite the section to say something like "struggling to recover from a poisoned condition".

FWIW, the source of the disputed claim appears to be http://hyperphysics.phy-astr.gsu.edu/hbase/NucEne/xenon.html which says "They apparently did not have the understanding that the failure to increase was due to the absorption of neutrons by the xenon". If we don't delete the claim, a citation is needed, and that's the best I've found for it, but as mentioned above, I don't believe it. 167.88.12.231 (talk) 01:36, 30 June 2019 (UTC)


 * Hyperphysics seems to be a reliable source. The source you have given doesn't contradict the claim made. Why don't you believe it? Andrewa (talk) 06:50, 7 February 2021 (UTC)

What is Dk/k?
Section "Iodine Pit Behavior": I don't understand the following sentence: "As the core reactivity reserve is usually limited to 10% of Dk/k, ..." What is Dk/k? -- Wassermaus (talk) 09:23, 29 April 2021 (UTC)

An abbreviation for "delta-k divided by k." The k factor is the number of additional fissions caused by one fission. At one, exactly, you have a reactor in a steady state. Less than one, the reactor power is falling, more than one, reactor power is increasing. Delta (Δ) is the fourth letter of the Greek alphabet, commonly used to indicate change. So Δk/k is the rate of change of the reactor's power level. If less than one, the reactor is shutting down, if more than one the reactor is building up power.

The "core reactivity reserve" is the amount of extra reactivity the operator has available to increase fissions in the reactor when he/she wants to increase power generation.

That help?Saintonge235 (talk) 17:12, 22 January 2022 (UTC)