The most famous example is the Apollo 13 lander which was used as a lifeboat. After it was jettisoned it crashed into the Pacific Ocean.
It had a plutonium-238 RTG. Radiation from it has never been detected.
RTG's are designed to crash.
I'm not familiar with this particular reactor, but I'm familiar with many analogues of reactors of this type.
This reactor will be a fission reactor and not an RTG, and thus will almost certainly not be critical during launch, and probably not all that radioactive. Most likely the fuel would be designed to be a "breed and burn" type device, meaning that the critical materials will be present in rather small amounts, I'd suspect a U-235 core with either thorium or depleted uranium as a blanket.
My son interned at ORNL and in the last week got a tour of the HFIR, which is not in operation owing to the use of a new fuel manufacturing technology that led to the fuel not being the right size. The core, he told me, is about 30 cm in diameter, which gives a feel for how small reactors can actually be. It's roughly the size of a paint can.
As the ocean naturally contains a little less than 5 billion tons of uranium, owing to its oxygen atmosphere, this is not a particularly risky device.
The ocean also contains about 500 million curies of potassium-40, naturally. In fact, if a human being didn't contain radioactive potassium, he or she would die since potassium is an essential element and all of it radioactive.
The public fear of radiation is absurd and rather ignorant. This ignorance is quite literally killing the planet.
In spite of deliberate public ignorance, egged on by uneducated journalists, I'd like to see more terrestrial "breed and burn" reactors. The concept makes nuclear fission fuel basically inexhaustible.
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