Heat the oven to 350ºF.
Put the cranberries and the orange juice in a small bowl and let sit at room temperature for at least 30 minutes.
Spread the walnuts in an even layer on a rimmed baking sheet and toast in the oven until golden brown, about 12 minutes.
Transfer the nuts to a plate to cool. When cool, crumble the nuts into smaller pieces.
Bring the water and the kosher salt to boil in an 8-quart stock pot.
Put the beans in the boiling water, stir once or twice to distribute them, and cook until tender throughout, 4 to 5 minutes, depending on their size and freshness.
Drain the beans well in a colander and set aside.
Strain the cranberries and reserve the juice.
Melt the butter in a large (preferably 12-inch) skillet over medium-high heat until bubbling but not browned.
Add the green beans and spread them out in the pan. Let them cook for 2 to 3 minutes without stirring.
Add the toasted walnuts and strained cranberries.
Toss all together and cook, stirring occasionally, for 2 minutes more, to let the ingredients warm and their flavors mingle.
Add the reserved orange juice, stir well, and cook until most of the liquid has evaporated, about 1 minute more.
Taste and season with salt and pepper as needed. Transfer to a serving dish and serve immediately