Radiolabeled Monoclonal Antibody Therapy, Fludarabine Phosphate, and Low-Dose Total-Body Irradiation Followed by Donor Stem Cell Transplant and Immunosuppression Therapy in Treating Older Patients With Advanced Acute Myeloid Leukemia or High-Risk Myelodysplastic Syndromes

Inclusion Criteria:

* Patients with advanced AML defined as beyond first remission, primary refractory disease, or evolved from myelodysplastic or myeloproliferative syndromes; or patients with MDS expressed as refractory anemia with excess blasts (RAEB), refractory anemia with excess blasts in transformation (RAEBT \[Note: classification removed under current World Health Organization \[WHO\] classification system\]), refractory cytopenia with multilineage dysplasia (RCMD), RCMD with ringed sideroblasts (RCMD-RS), or chronic myelomonocytic leukemia (CMML)
* Patients in relapse must have documented cluster of differentiation (CD)45 expression by their myelodysplastic or leukemic cells to be studied and treated with 131I-labeled BC8 antibody; patients in remission do not require phenotyping and may have leukemia previously documented to be CD45 negative
* Patients should have a circulating blast count of less than 10,000/mm\^3 (control with hydroxyurea or similar agent is allowed)
* Patients must undergo a 24-hour urine collection with documented creatinine clearance \> 50 ml/min
* Bilirubin \< 2 times the upper limit of normal
* Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 2 times the upper limit of normal
* Karnofsky score \>= 70 or Eastern Cooperative Oncology Group (ECOG) =\< 2
* Patients must have an expected survival of \> 60 days and must be free of active infection
* Patients must have a human leukocyte antigen (HLA)-identical sibling donor or an HLA-matched unrelated donor who meets standard Seattle Cancer Care Alliance (SCCA) and/or National Marrow Donor Program (NMDP) criteria for peripheral blood stem cell (PBSC) donation; related donors should be matched by molecular methods at the intermediate resolution level at HLA-A, B, C, and DRB1 according to Fred Hutchinson Cancer Research Center (FHCRC) Standard Practice Guidelines and to the allele level at DQB1; unrelated donors should be identified using matching criteria that follows the FHCRC Standard Practice Guidelines limiting the study to eligible donors that are allele matched for HLA-A, B, C, DRB1, and DQB1 (grade 1), and accepting up to one allele mismatch as per standard practice grade 2.1 for HLA-A, B, or C; PBSC is the only permitted hematopoietic stem cell (HSC) source
* DONOR: Donors must meet HLA matching criteria as outlined above as well as standard Seattle Cancer Care Alliance (SCCA) and/or NMDP criteria for PBSC donation

Exclusion Criteria:

* Circulating antibody against mouse immunoglobulin (human anti-mouse antibody \[HAMA\])
* Prior radiation to maximally tolerated levels to any normal organ
* Patients may not have symptomatic coronary artery disease and may not be on cardiac medications for anti-arrhythmic or inotropic effects
* Inability to understand or give an informed consent
* Patients who are seropositive for human immunodeficiency virus (HIV)
* Perceived inability to tolerate diagnostic or therapeutic procedures, particularly treatment in radiation isolation
* Patients who have previously undergone marrow or PBSC transplantation