You could, but its not producing that much heat. Moreover, a normal reactor has two loops. The first is an internal loop that moves heat from the core to a hea

You could, but its not producing that much heat. Moreover, a normal reactor has two loops. The first is an internal loop that moves heat from the core to a heat exchanger. The second is an external loop that takes heat from the heat exchanger and turns it into steam that goes to a turbine. This is done because the internal loop gets rather contaminated with radioactive materials. Turning that contaminated water to steam and venting it to the outside world is... bad.