A Passive System Technical Specification for CANDU 6 Generation II Reactor
Bibliographic record
Abstract
The Fukushima accident led to concerns about enhancement of safety for the new design nuclear plants and also for the existing fleet of nuclear power plants (NPPs) by introducing passive safety systems. An important objective is to increase the grace time for a plant operator to establish an alternate heat sink in the case of a station blackout (SBO) accident. Efforts made by RATEN (https://www.raten.ro/?lang=en) in the frame of H2020 PIACE projects were to implement a passive safety system in the CANadian Deuterium Uranium 6 (CANDU 6) project. In this project, RATEN was in charge of the engineering design and computational modeling aspects, required to integrate a passive safety system in the existing CANDU 6 project. In order to design a passive safety system, a 3-day SBO accident was credited to occur at the Cernavoda Unit 2 NPP, a CANDU 6–type reactor. An isolation condenser (IC) system capable of transporting the total energy produced in the reactor core due to decay heat was designed and modeled. The engineering design solutions were made by RATEN CITON (http://www.citon.ro/english_index.html), and the thermal-hydraulic analysis was performed by RATEN ICN (https://nuclear.ro/en/) using the RELAP5 computer code (https://relap53d.inl.gov/SitePages/Home.aspx) to confirm natural circulation both in the secondary and the primary circuits during the SBO accident and heat transfer capability of the IC with and without noncondensable gases. The passive safety system design consists of four (4 × 33%) closed loop independent circuits, one for each steam generator. Each loop has an IC design to transport 0.66% of nominal thermal power of the reactor. In order to avoid a rapid transient during reactor cooldown, the system is endowed with four noncondensable gas tanks (one for each IC), connected to the outlet header of each IC, provided for reducing the IC heat flux simultaneously with reactor core residual heat decrease. The design concept was adapted to the CANDU 6 reactor power and the specific layout of the Cernavoda site, starting from the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED) patent (the demonstrator of lead fast reactor technology) passive system, to increase the plant operator grace time from 23 h (current situation) to more than 72 h.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.028 | 0.018 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".