What causes persistant leg cramps primarily in one leg (right)?

Muscle irritation. Cramping comes on when muscles become irritated after heavy working, exercise, prolonged standing. A frequent cause is venous incompetence, and the leaky valves within veins allow reverse flow of blood down the legs, resulting in swelling, subsequent cramping. See www.Phlebology.Org and see a phlebologist who can help you out.
? Blood flow. Low electrolytes can cause cramps but lack of arterial blood flow can also. Will need comprehensive blood test and possibly arterial doppler.