Final answer:
Angela's team should choose the Waterfall model for their software development needs as it suits their requirements for careful unchanging planning and analysis.
Step-by-step explanation:
If Angela's software development team is focused on a project for a nuclear power plant that requires careful up-front planning and analysis with no changes expected during the coding process, the most suitable Software Development Life Cycle (SDLC) model would be the Waterfall model. The Waterfall model is a linear and sequential approach to software development where each phase must be completed before the next phase begins. This model does not typically accommodate going back to a previous stage once it is completed, which makes it a good fit in environments where requirements are well understood and unlikely to change over time. In contrast, the Spiral model includes iterations, which allow for continuous refinement and risk assessment but would not be suitable for Angela's team due to the team's need for upfront planning and lack of anticipated changes. Agile Scrum and Rapid Application Development (RAD) are also iterative and flexible in nature, which allow for changes during the development process, thus not fitting Angela's stated requirements.