Xjyuk

What are the consequences for a developed nation to not accept any refugees? Are there grave consequences for not accepting any refugees?

I am asking, because almost every country on the planet accepts refugees as if they were forced to do so, yet I don't see any law that forces any country to do so. What are the factors that compel countries to do so?

An important factor here is the treaties a country has signed up to. In this case, a relevant one is the 1951 Refugee Convention. From UNHCR:

The 1951 Refugee Convention is the key legal document that forms the basis of our work. Ratified​ by 145 State parties, it defines the term ‘refugee’ and outlines the rights of the displaced, as well as the legal obligations of States to protect them.

The core principle is non-refoulement, which asserts that a refugee should not be returned to a country where they face serious threats to their life or freedom. This is now considered a rule of customary international law.

Then there is the 1967 convention, which Wikipedia has the following about:

Where the 1951 United Nations Convention Relating to the Status of Refugees had restricted refugee status to those whose circumstances had come about "as a result of events occurring before 1 January 1951", as well as giving states party to the Convention the option of interpreting this as "events occurring in Europe" or "events occurring in Europe or elsewhere", the 1967 Protocol removed both the temporal and geographic restrictions. This was needed in the historical context of refugee flows resulting from decolonisation.

Many countries are party to those treaties, as illustrated by the image below:

_{Image from Wikipedia, in the public domain}

The legend: Light Green = party to only the 1951 Convention Yellow = party to only the 1967 Protocol Dark green = party to both

Really the compulsion is a moral and practical one, rather than something enforced by international law: refugees tend to arrive in large numbers, turning them away is both difficult and tends to get them killed. It may be difficult to deport people to a war zone, e.g. if there are no functioning airports.

The shadow of the Holocaust hangs over 20th-century refugee policy. Before WW2, lots of Jewish refugees were turned away. It became clear afterwards that this was complicity with their mass murder.

This can be complicated. Some countries recognize other countries as decent, safe nations. Some countries on this planet only border safe countries and may have established "safe third country" treaties with them where neither country will recognize refugee claims by anyone who travels through the other country and arrives at the border. (The idea being that they are already at a safe country and therefore can't seek asylum since they are already safe.) This is further complicated by other factors of course like countries that allows free travel among eachother.

I bring this up because in the modern conversations around European and North American refugee claimants, some people and governments (cough Trump) have asserted they shouldn't accept refugees who have traveled through safe countries (cough Mexico) because the refugee was in a safe country before arriving.

My own country, Canada, is in a particularly nasty situation where for the past number of years we've had people cross our southern border then claim refugee status. If we deny them refugee status, where do we deport them? The US won't be happy and we can't ship them to the country they are fleeing from. If we accept them, we're tarnishing our relationship by functionally calling the USA an unsafe country.

I believe your premise is incorrect. For instance, neither Japan nor China accept many refugees.