Thermal-hydraulic phenomena for water cooled nuclear reactors

Aksan, N.; D'Auria, Francesco Saverio; Glaeser, H.

doi:10.1016/j.nucengdes.2018.01.035

Cited by 33 publications

(18 citation statements)

References 6 publications

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“…PCT (namely what has been called blowdown PCT) is calculated with a reasonable agreement by various code users; however, precursory cooling conditions for rewet and time of rewet occurrence show large discrepancies among the various calculations.3.4.2. Other Thermal-Hydraulic PhenomenaThermal-hydraulic phenomena in addition to those discussed in the present paper are relevant in case of LBLOCA in PWR (and PHWR) during each of the considered periods, as discussed byAksan, 2017, D'Auria & Galassi 2017, and Aksan et al, 2018. A more comprehensive list of phenomena includes: ECCS bypass, steam binding, CCFL in different locations, pressure drop at geometric discontinuities, broken MCP fluid-dynamic resistance with free or locked rotor, two phase MCP (broken and intact loops) performance, condensation at ECC port, downcomer liquid penetration, mixing in different locations of primary loop, containment thermal-hydraulics.…”

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confidence: 89%

The role of nuclear thermal-hydraulics in the licensing of Atucha-II: The LBLOCA

Mazzantini¹,

Galassi

D'Auria

2019

Nuclear Engineering and Design

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The paper deals with the safety evaluation and the embedded licensing process of the Atucha-II 800 Mwe Pressurized Heavy Water Reactor (PHWR) in Argentina. Atucha-II was designed by Kraftwerk Union (KWU) during the 60's, the related construction was started/stopped in the 90's and restarted on 2006, and was connected to the electrical grid in 2014. Because of market policies, the KWU designer could not be directly involved in the licensing process during the first decade of the 2000 millennium: a licensing suited safety evaluation was performed by the Nucleoeléctrica Argentina (NA-SA), utility owner of the Atucha-II, with support of external experts group. A designer-independent assessment was performed having access to the installed systems and components other than the relevant design documents. Large core size (related to Pressurized Water Reactor-PWR-producing the same thermal power), presence in the core of natural uranium and heavy water fluids, i.e. the coolant and the moderator driven by two circulation loops with different average temperatures, characterize the system design. In those conditions, during the early phase of a depressurization transient, the 'hot' coolant vaporizes and the colder moderator remains in the liquid phase: a positive void coefficient is created. The relevance of the Large Break Loss of Coolant Accident (LBLOCA) in safety assessment is discussed with emphasis given to the system design features, the approach pursued in the analysis and the key results. Break opening time and time of occurrence of the safety boron injection affect, during the early period of the transient, the propagation of (negative) pressure wave, the fluid flashing, the heat transfer and the neutron flux: a fission power excursion is expected to occur. The analysis of a complex three-dimensional situation, considering the unavoidable uncertainties associated with the computation, demonstrates that safety limits are preserved.

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confidence: 89%

The role of nuclear thermal-hydraulics in the licensing of Atucha-II: The LBLOCA

Mazzantini¹,

Galassi

D'Auria

2019

Nuclear Engineering and Design

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“…The need to validate computer codes and the complexity of AS at the basis of the validation brought to the decision to identify and to characterize phenomenological windows and phenomena. The related processes of code validation and phenomena identification started by CSNI in the early 1980's, [3].…”

Section: Background Information For T-hpmentioning

confidence: 99%

“…A parallel investigation within the International Atomic Energy Agency (IAEA) focused on 'advanced' (or 'new') reactor designs. The reader may find details on the topics above and the full reference to T-HP in [3]. A perspective for future use of T-HP might outcome from the CSNI Specialists Meeting scheduled by the end of 2021.…”

Section: Figure 1 Outline Of the History Of T-hp Modified From [1]mentioning

confidence: 99%

“…Those experiments and phenomena provide the best basis for the assessment of thermal hydraulic codes, [2]. A couple dozen reports, in forthcoming two decades, constitute the bases for the identification and the characterization of 116 T-HP, [3]. The description of individual phenomena and the connection between T-HP and AS are the topic of Chapters 6 and 15 of [1].…”

Section: Introductionmentioning

confidence: 99%

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Physical Phenomena in Nuclear Thermal Hydraulics and Current Status

D'Auria¹,

Aksan²,

Glaeser³

2021

TI-IJES

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116 nuclear Thermal-Hydraulic Phenomena T-HP are identified in the present paper, following documents issued during the last three decades by the Committee on the Safety of Nuclear Installations of Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD/NEA/CSNI) and by the International Atomic Energy Agency (IAEA). The derived T-HP list includes consideration of experiments performed in Separate Effect Test (SET) and Integral Effect Test (IET) facilities relevant to reactor coolant system and containment of Water Cooled Nuclear Reactors (WCNR). We consider a dozen WCNR types: Pressurized Water Reactors (PWR), Boiling Water Reactors (BWR), Russian reactors (VVER-440, VVER-1000 and RBMK), pressure tube heavy water reactors by Canada (CANDU) and India (PHWR) and so-called ‘advanced’ reactors (e.g. AP-1000 and APR-1400 designed in US and Korea, respectively). We envisage a variety of applications for the T-HP list. Four of the phenomena are helpful to characterize the current state of art in nuclear thermal-hydraulics: Counter Current Flow Limitation (CCFL), Critical Heat Flux (CHF), reflood and Two-Phase Critical Flow (TPCF). Furthermore, the T-HP identification contributes to addressing the scaling issue, performing uncertainty evaluations, developing constitutive equations and ‘special models’ in codes and prioritizing the research.

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“…A dozen re ports is sued by IAEA and OECD/NEA (all those re ports are listed in ref. [36]) are con sid ered in ad di tion to 13 WCNR types and 47 ac ci dent se quences (top cen tral in the sketch of fig. 2).…”

Section: Phe Nom Ena List and De Scrip Tionmentioning

confidence: 99%

The Best Estimate Plus Uncertainty approach in nuclear reactor safety and licensing: Brief history and the elements after licensing

Francesco

Giorgio

2019

Nucl Technol Radiat Prot

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The best es ti mate plus un cer tainty is, at the same time, an ap proach, a pro ce dure and a framework in nu clear ther mal-hy drau lics and nu clear re ac tor safety and li cens ing. The mo ti va tion at the ba sis of the best es ti mate plus un cer tainty is the lack of knowl edge in the ar eas of sin gle and, mainly, two-phase tran sient ther mal-hy drau lics. In other terms and in tro duc ing some sim pli fi ca tions, the in suf fi cient knowl edge of tur bu lence im poses the de sign of roadmaps for the ap pli ca tion of im per fect (ther mal-hy drau lic) mod els to the eval u a tion of de sign fea tures and of safety for com plex tech no log i cal in stal la tions or sys tems like the nu clear power plants and, more spe cif i cally, the wa ter cooled nu clear re ac tors. Fur ther more, the le gal coun ter part of nu clear re ac tor safety, or the li cens ing, is con cerned: there fore the best es ti mate plus un certainty must ac count for rules and reg u la tions de rived from the fun da men tal radioprotection prin ci ple which im poses the minimization of the im pact of ra di a tions upon hu mans and the en vi ron ment un der any cir cum stance. In the pres ent pa per, the key el e ments of the ap proach are iden ti fied and char ac ter ized. These shall be seen as the sup port for a con sis tent ap pli ca tion of ther mal-hy drau lics to the de sign and safety of wa ter-cooled nu clear re ac tors. Key words: best es ti mate, un cer tainty eval u a tion, best es ti mate plus un cer tainty, li cens ing pro cess, val i da tion, scal ing F. S. D'Auria, et al.: Best Es ti mate Plus Un cer tainty Ap proach in Nu clear Re ac tor .

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Thermal-hydraulic phenomena for water cooled nuclear reactors

Cited by 33 publications

References 6 publications

The role of nuclear thermal-hydraulics in the licensing of Atucha-II: The LBLOCA

The role of nuclear thermal-hydraulics in the licensing of Atucha-II: The LBLOCA

Physical Phenomena in Nuclear Thermal Hydraulics and Current Status

The Best Estimate Plus Uncertainty approach in nuclear reactor safety and licensing: Brief history and the elements after licensing

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