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Event sequences that would lead to an early radioactive release or a large radioactive release are required to be practically eliminated in HAF102—2016. But there are lack of specific acceptance criteria and demonstration method of practical elimination in China. Safety requirement of practical elimination was studied, and some insights, acceptance criteria and demonstration method of practical elimination were proposed in this paper. Demonstration of practical elimination for HPR1000 was evaluated. The main conclusions are as follows: 1) Practical elimination is a higher requirement for the safety design of nuclear power plants. It is not a requirement that accident conditions have no release, but the plant states that could lead to an early or a large radioactive release have been practically eliminated. And conditions that have not been practically eliminated should be fully considered in the design to ensure its radiological consequences limited. 2) With reference to international practice and the relevant requirements of emergency plans and preparations in China, it is the first time to propose the deterministic and probability acceptance criteria for practical elimination in China at this stage. The radiological release acceptance criteria at this stage are suggested that there is no evacuate action beyond 3 km from the site boundary, and no sheltering action beyond 5 km. It is recommended that the DEC�B design requirement is less than 100 TBq equivalent 137Cs. This criterion is also the criterion for large radioactive release in the level 2 PSA. 3) Demonstration method of practical elimination was proposed in this paper, and demonstration of practical elimination for HPR1000 was evaluated. In the final analysis, DBA is effectively mitigated by defence�in�depth, and severe accident prevention and mitigation measures are considered sufficiently for HPR1000. Even if severe accident considered in design is happened, the containment could be intact. Practical elimination is realized on HPR1000.

Engineering the glycerol‐3‐phosphate pathway could enhance erythritol production by accelerating glycerol uptake. However, little work has been conducted on the alternative dihydroxyacetone (DHA) pathway in Yarrowia lipolytica. Herein, this route was identified and characterized in Y. lipolytica by metabolomic and transcriptomic analysis. Moreover, the reaction catalyzed by dihydroxyacetone kinase encoded by dak2 was identified as the rate‐limiting step. By combining NHEJ‐mediated insertion mutagenesis with a push‐and‐pull strategy, Y. lipolytica strains with high‐yield erythritol synthesis from glycerol were obtained. Screening of a library of insertion mutants allows the identification of a mutant with fourfold increased erythritol production. Overexpression of DAK2 and glycerol dehydrogenase GCY3 together with gene encoding transketolase and transaldolase from the nonoxidative part of the pentose phosphate pathway led to a strain with further increased productivity with a titer of 53.1 g/L and a yield 0.56 g/g glycerol, which were 8.1‐ and 4.2‐fold of starting strain. Take Away: The genes involved in the alternative dihydroxyacetone route were detected and then analyzed by GC/MS and RNA‐seq studies.Dihydroxyacetone kinase DAK2 catalyzes the rate‐limited step in the alternative glycerol uptake route.Diverse Yarrowia lipolytica strains had different adaptability to the alternative glycerol uptake route.53.1 g/L of erythritol production and a yield of 0.56 g/g glycerol were achieved by performing a push‐pull strategy in Yarrowia lipolytica M09. [ABSTRACT FROM AUTHOR]

Abstract: Squalene, a valuable acyclic triterpene, can be used as a chemical commodity for pharmacology, flavor, and biofuel industries. Microbial production of squalene has been of great interest due to its limited availability, and increasing prices extracted from animal and plant tissues. Here we report genetic perturbations that synergistically improve squalene production in Saccharomyces cerevisiae. As reported previously, overexpression of a truncated HMG‐CoA reductase 1 (tHMG1) led to the accumulation 20‐fold higher squalene than a parental strain. In order to further increase squalene accumulation in the tHMG1 overexpressing yeast, we introduced genetic perturbations—known to increase lipid contents in yeast—to enhance squalene accumulation as lipid body is a potential storage of squalene. Specifically, DGA1 coding for diacylglycerol acyltranferase was overexpressed to enhance lipid biosynthesis, and POX1 and PXA2 coding for acyl‐CoA oxidase and a subunit of peroxisomal ABC transporter were deleted to reduce lipid β‐oxidation. Simultaneous overexpression of tHMG1 and DGA1 coding for rate‐limiting enzymes in the mevalonate and lipid biosynthesis pathways led to over 250‐fold higher squalene accumulation than a control strain. However, deletion of POX1 and PXA2 in the tHMG1 overexpressing yeast did not improve squalene accumulation additionally. Fed‐batch fermentation of the tHMG1 and DGA1 co‐overexpressing yeast strain resulted in the production of squalene at a titer of 445.6 mg/L in a nitrogen‐limited minimal medium. This report demonstrates that increasing storage capacity for hydrophobic compounds can enhance squalene production, suggesting that increasing lipid content is an effective strategy to overproduce a hydrophobic molecule in yeast. [ABSTRACT FROM AUTHOR]