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Startup_Procedure_U2.md

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The reactor can be operated in three modes: SRM, IPR, and Run. The Run mode can be enabled above 5% reactor power and can be used without any restrictions between 4% to 100% of reactor power (it will SCRAM below 4%). SRM/IPR modes are used for startup only and have several restrictions.

  • Only one rod can be pulled at a time, following a predefined pattern.
  • The next rod becomes available when the previous rod is pulled to 20%.
  • When all rods are at 20%, the rods can be pulled to 40%, and so on.
  • Autocontrol and autobalancer are not available.

SRM mode is used for low-power startup. SRM should be lowered into the core by a few percent, and the SRM indicator should be monitored. As the equivalent rod's position increases, SRM should be lowered to reach a depth similar to the equivalent rod's position. This way, SRM can be monitored in the region just above the rods. Once SRM reaches half of the scale, the reactor mode should be changed to IPR.

  • IPR will scram the reactor if it goes out of range (below 10% or above 90%).
  • The IPR level has to be incremented when the power reaches the blue region to prevent a scram.
  • Once the power is above 5%, the reactor should be switched to Run mode to avoid a scram due to IPR being out of range.

This procedure is introduced in BWR reactors because they tend to be unstable at low powers, where no negative coefficient plays a role yet. It is also used to balance out reactivity in the entire core. The pattern is coded into a system, and the flashing rod should be selected, then pulled to around 20%. Beyond that value, the rod block will prevent any further pulling. Meanwhile, another rod will begin flashing, indicating the sequence. This procedure should be repeated until 5% power is reached.

IPR has 8 levels, and they must be incremented when the indication nears the 90% red line. However, it cannot be switched to a high level immediately, as it would also scram the reactor when the indication is below the red 10% line. When reaching the 8th level, the reactor must be switched to Run mode to prevent a scram from IPR. Additionally, remember to change IPR to level one after a scram to enable a restart.