Leak-before-break: Global perspectives and procedures

Bourga, Renaud; Moore, Philippa; Janin, Yin Jin; Wang, Bin; Sharples, John

doi:10.1016/j.ijpvp.2015.02.004

Cited by 26 publications

(16 citation statements)

References 40 publications

(45 reference statements)

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“…As an alternative, the "Leak before Break" (LBB) concept [6][7][8] would allow avoiding the provision of SG and piping supports and restraints designed to mitigate the dynamic effects of a piping rupture. Further discussion of such considerations will be presented in Section 5 below, as part of the emergency core cooling system presentation.…”

Section: Reactor Coolant Pressure Boundary (Rcbp)mentioning

confidence: 99%

A new direction in PWR simplification

Bonhomme¹

2021

EPJ Nuclear Sci. Technol.

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A new approach to PWR simplification is presented, in which a compact Reactor Coolant System (RCS) configuration is introduced, particularly suited for a power level in the range of 600 MWe. Customary PWR primary system components are eliminated to achieve this RCS simplification. For example, RCS pressure control through a “self-pressurization” mode, with core exit at saturation temperature with less than 1% steam, allows elimination of a pressurizer. Also, mechanical control rods are replaced by reactivity control using negative moderator void and temperature coefficient together with variable speed primary pumps, and with an upgrade in the safety boration function. Decay heat removal in shutdown conditions is realized through the secondary side rather than through primary side equipment. The compact RCS can be installed in a small volume, high-pressure containment. The containment is divided into two leak-tight zones separated by a partition plate. Safety equipment installed in one of the two zones will be protected against adverse ambient conditions from leaks or breaks in the other zone. The partition facilitates management of coolant inventory within the RCS and the containment following RCS leaks or breaks. In particular, the safety injection system as commonly known, consisting of accumulators and multiple stages of injection pumps can be discarded and replaced by gravity-driven flooding tanks. Space available around major RCS components is adequate to avoid compromising accessibility during maintenance or in-service inspection operations. In addition, the two-zone, high-pressure containment provides extra margins in severe accident mitigation. Finally, the proposed containment has a much smaller size than customary large dry containments in PWR practice and it can be anticipated that Nuclear Island building size will similarly be reduced.

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Section: Reactor Coolant Pressure Boundary (Rcbp)mentioning

confidence: 99%

A new direction in PWR simplification

Bonhomme¹

2021

EPJ Nuclear Sci. Technol.

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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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“…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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Leak-before-break: Global perspectives and procedures

Cited by 26 publications

References 40 publications

A new direction in PWR simplification

A new direction in PWR simplification

The technological challenge for current generation nuclear reactors

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

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