Russia may default on its "debt" denominated is currencies other than its own, but that may prove to be a good thing to counter sanctions placed upon it. It cannot default involuntarily in any debt denominated in the currency it can create at will, so it can always "afford" anything it can resource from its private sector, which is just about anything in such a large and resource rich country.

The entire concept of debt for a country with a sovereign fiat currency is largely misunderstood, but I'm betting Putin has no delusions about it. Such a country only has what debt it owes in foreign currencies to worry about, and at this time that is the problem of those holding that debt, not Putin or the Russian people.