Build and score your RTA matrix
Weight the ten key elements and their topics, score each candidate design from 1 to 5, and see the ranking, the element-by-element picture and how sensitive the result is to your weights. New to the method? Read Running the RTA matrix first.
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Set up
Name the assessment, pick starting weights, and list the candidate designs (2 to 5).
Starting weights convert IAEA Table 7 ratings (High = 3, Medium = 2, Low = 1, N/A = 0) into percentages, with topics weighted equally. They are a starting point only — replace them with your own rationale. Applying them keeps your scores and notes.
Compare like with like: the IAEA advises separate assessments for large water-cooled reactors and for SMRs.
Topic weights and scores are taken from the IAEA Annex example for large WCRs in the fictitious country "Retasland" (Tables A-1 to A-18), with sub-topics combined by their weights. Element weights follow the Annex's High / Medium / Low ratings. The Annex notes each table may describe a different set of designs, so these totals demonstrate the mechanics only — they are not an IAEA result.
1 · Key element weights
Write the rationale first, then set the weights. They should add up to 100%; results always use the normalized shares.
| Key element | IAEA Table 7 rating for the selected context | Weight % | Share used |
|---|
2 · Score the key topics
Scores: 1 = least meets your rationale … 5 = best fit. Leave "–" until you have evidence, and use the pencil to record the evidence and mark any score as provisional pending vendor answers. Topic weights within each element should add up to 100%; set 0 for topics that do not apply.
3 · Results
Totals are on the 1–5 scale. Treat them as a guide: check knock-outs, sensitivity and the issues numbers cannot capture.
Ranking
Weighted total per design. The leader is highlighted.
Element-by-element scores
Each cell is the design's weighted score within that key element (1–5). Hover or focus a cell for its contribution.
Possible knock-outs
Scores of 1–2 on the most heavily weighted topics. If any of these is disqualifying, treat it as an exclusion rather than averaging it away.
Completeness
Share of total weight that has been scored for each design. Totals below 100% are provisional.
Sensitivity to element weights
Who leads if one element's weight is halved or raised by half (others rescaled), and the weight at which the leader would change.