Preheat the oven to 350°. In a pie plate, toast the walnuts for 8 minutes or until fragrant. Let cool, then coarsely chop.
In a medium saucepan of boiling salted water, blanch the sugar snaps until bright green and crisp-tender, about 2 minutes. Drain and rinse under cold water to stop the cooking. Pat dry and transfer to a large bowl. Add the toasted walnuts, celery, radishes, olive oil, lemon juice and dill and toss well. Season the salad with salt and pepper and serve.