Nuclear safeguards are intrinsic and extrinsic features of a facility which reduce probability of the successful acquisition of special nuclear material (SNM) by hostile actors. Future bulk handling facilities in the United States will include both domestic and international safeguards as part of a voluntary agreement with the International Atomic Energy Agency. A new framework for safeguards, the Safeguards Envelope Methodology, is presented. A safeguards envelope is a set of operational and safeguards parameters that define a range, or “envelope,” of operating conditions that increases confidence as to the location and assay of nuclear material without increasing costs from security or safety. Facilities operating within safeguards envelopes developed by this methodology will operate with a higher confidence, a lower false alarm rate, and reduced safeguards impact on the operator. Creating a safeguards envelope requires bringing together security, safety, and safeguards best practices. This methodology is applied to an example facility, the Idaho Chemical Processing Plant. An example diversion scenario in the front-end of this nuclear reprocessing facility, using actual operating data, shows that the diversion could have been detected more easily by changing operational parameters, and these changed operational parameters would not sacrifice the operational efficiency of the facility, introduce security vulnerabilities, or create a safety hazard.