In the case of nuclear disaster which of the following options for cooling the nuclear reactors may be adopted ? 1. Pumping of water to the reactors. 2. Use of boric acid. 3. Taking out the fuel rods and keeping them in a cooling pond. Select the correct answer using the code given below :

In a nuclear disaster, multiple emergency cooling strategies are employed. Pumping water into the reactor core is the primary method to remove residual heat and prevent core meltdown [t2, t9]. Boric acid is frequently added to this emergency cooling water because boron acts as a potent neutron absorber, which helps to shut down the nuclear chain reaction by reducing reactivity [t1, t5, t10]. Additionally, fuel rods can be transferred to a cooling pond (spent fuel pool) to manage heat. During the Fukushima disaster, fuel assemblies were stored in such pools where water is continuously circulated to remove decay heat and provide radiation shielding [t4, t7, t8]. While moving fuel rods during an active disaster is extremely difficult, it remains a standard technical option for cooling and isolating radioactive material from the reactor vessel [t3, t7]. Therefore, all three methods are valid options for cooling.

Sources

1. [1] https://www.sciencedirect.com/science/article/abs/pii/S0306454923000014
2. [2] https://www.nrc.gov/docs/ML2415/ML24159A227.pdf
3. [3] https://en.wikipedia.org/wiki/Fukushima_Daiichi_units_4,_5_and_6
4. [4] https://www.ncbi.nlm.nih.gov/books/NBK373721/
5. [5] https://www.nrc.gov/docs/ML0902/ML090220255.pdf