Leak-before-break analyses of PWR and BWR piping concerning size effects

Heckmann, Klaus; Sievers, J.

doi:10.1016/j.nucengdes.2017.11.027

Cited by 11 publications

(3 citation statements)

References 9 publications

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“…LBB is based upon the experimental observation that detectable fluid leakage from a large diameter pressure pipe is expected before disruptive double ended break, see e.g., Heckmann andSievers 2018, andBourga et al 2015. The LBB may have a wide range of applicability in nuclear technology, e.g.…”

Section: The Lbb Theoremmentioning

confidence: 99%

The technological challenge for current generation nuclear reactors

D'Auria¹,

Debrecin²,

Glaeser³

2019

NUCET

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The present paper deals with the proposal of an additional safety barrier for the class of large (1000 MWe or more) Light Water Reactors (LWR) now in operation, in construction, or under design. Emphasis is given to the motivations or the needs for the barrier. Two main parts of the paper can be distinguished. The following topics are discussed in the former part (section 2): (a) the weakness of the barrier constituted by the current design of nuclear fuel; (b) the continuously increasing complexity of the system, with main reference to the Instrumentation and Control (I&C); (c) the role that the Large Break Loss of Coolant Accident (LBLOCA) had for arriving at the current layout of the Reactor Coolant System (RCS). Furthermore avoiding the severe accidents in 1979, 1987 and 2011, is at the basis of the proposal. In the latter part (sections 3 and 4), the elements of the proposed technological safety barrier are discussed: the As-Low-As-Reasonably-Achievable (ALARA) principle, the Best Estimate Plus Uncertainty (BEPU) approach, the Extended Safety Margin Detection (E-SMD) hardware, the Emergency Rescue Team (ERT) strategy (or a virtual entity for the reactor) and the Independent Assessment (IA) concept. The additional safety barrier, although not demonstrated in the paper, is expected to reduce for a factor in the range 10–1000 the probability of core melt and to have a cost in the order of 1% the cost of a nuclear reactor unit.

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Section: The Lbb Theoremmentioning

confidence: 99%

The technological challenge for current generation nuclear reactors

D'Auria¹,

Debrecin²,

Glaeser³

2019

NUCET

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show abstract

“…LBB is based upon the experimental observation that detectable fluid leakage from a large diameter pressure pipe is expected before disruptive LOCA including double ended break, see e.g., Heckmann &Sievers, 2018, andBourga et al, 2015. The LBB has a wide range of applicability in nuclear technology, e.g.…”

Section: The Leak Before Break (Lbb) Theoremmentioning

confidence: 99%

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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“…Because they are built using ductile materials, this evaluation is made through the concepts of Elastic-Plastic Fracture Mechanics (EPFM). Through a fundamentally technical justification, the LBB concept has been widely applied in nuclear installation projects in several countries [2,3,4,5].…”

Section: Introductionmentioning

confidence: 99%

Leak-Before-Break methodology applied to different piping materials: a performance evaluation

Silva

Andrade

Monteiro

2019

Frattura Ed Integrità Strutturale

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This paper presents a study of the application of Leak-Before-Break (LBB) to nuclear piping using three different materials. Although had been introduced more than three decades ago, through a fundamentally technical justification, the LBB concept currently has been widely applied in nuclear installations projects in several countries. Based on the fracture mechanics, the LBB concept considers that a leakage from a crack can be detected before it reaches a critical size that implies the pipe failure, that is, the LBB analysis demonstrates through a technical justification that the probability of pipe rupture is extremely low. Among the aspects that involve the application of LBB, the main ones are: the definition of the material properties, which are obtained through tensile and fracture tests; the leakage analysis, which determines the rate of leakage due to the presence of a through-wall crack; and the analysis that verifies if the crack is stable considering the failure modes by ductile tear and plastic collapse. The materials SA-508 Cl. 3, SA-106 Gr. B and SA-376-TP304 were evaluated in relation to their performances for LBB. Data obtained from literature cases were used for the materials properties, and for the geometry and loadings of the pipe, all corresponding to the primary circuit of a PWR reactor. After application of the LBB, it was verified that all three materials met the limits established in the methodology. SA-508 Cl. 3 and SA-376-TP304 steels showed the best performance for ductile tear failure and plastic collapse failure, respectively, and SA-106 Gr. B steel had the lowest performance in both. All three materials presented plastic collapse as the most likely failure mode. In general, SA-376-TP304 steel presented the best performance for the LBB among the three materials evaluated in this work.

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Leak-before-break analyses of PWR and BWR piping concerning size effects

Cited by 11 publications

References 9 publications

The technological challenge for current generation nuclear reactors

The technological challenge for current generation nuclear reactors

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

Leak-Before-Break methodology applied to different piping materials: a performance evaluation

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