This phase I trial studies the side effects and maximum tolerated dose of yttrium Y 90 anti-cluster of differentiation 45 (CD45) monoclonal antibody BC8 (90Y-BC8) followed by donor stem cell transplant in treating patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), ormyelodysplastic syndrome (MDS) that is likely to come back or spread. Giving chemotherapy drugs, such as fludarabine phosphate (FLU), and total-body irradiation (TBI) before a donor peripheral blood stem cell (PBSC) or bone marrow transplant helps stop the growth of cancer or abnormal cells and helps stop the patient's immune system from rejecting the donor's stem cells. Radiolabeled monoclonal antibodies, such as 90Y-BC8, can find cancer cells and carry cancer-killing substances to them without harming normal cells. When the healthy stem cells from a donor are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. Sometimes the transplanted cells from a donor can make an immune response against the body's normal cells. Giving FLU, 90Y-BC8, and TBI before the transplant together with cyclosporine and mycophenolate mofetil after the transplant may stop this from happening.