This randomized phase III trial studies radiation therapy and cisplatin with triapine to see how well they work compared to the standard radiation therapy and cisplatin alone in treating patients with newly diagnosed stage IB2, II, or IIIB-IVA cervical cancer or stage II-IVA vaginal cancer. Radiation therapy uses high energy protons to kill tumor cells and shrink tumors. Drugs used in chemotherapy, such as cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Triapine may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. It is not yet known whether radiation therapy and cisplatin are more effective with triapine in treating cervical or vaginal cancer.