Nuclear Performance of Liquid-Metal Fast Breeder Reactors Designed to Preclude Energetic Hypothetical Core Disruptive Accidents

Bailey, H.S.; Lu, Yonghao

doi:10.13182/nt79-a32239

Cited by 4 publications

(2 citation statements)

References 2 publications

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“…Merk [3] using different arrangements of a ZrH moderator material to enhance feedback coefficients and the global performance of the core. Other moderator materials have been proposed, such as beryllium, not only for improving feedback effects [4] but also for reducing clad irradiation damage caused by fast neutrons [5]. Figure 1, which has been derived from a parametric study, shows the variation of K Doppler as a function of moderator material type and content in an SFR core fuelled with PuO 2 -UO 2 .…”

Section: Physical Principle Of the Cador Concept (Reinforced Doppler mentioning

confidence: 99%

CADOR “Core with Adding DOppleR effect” concept application to sodium fast reactors

Zaetta

Fontaine

Sciora

et al. 2019

EPJ Nuclear Sci. Technol.

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Generation-IV sodium fast reactors (SFR) will only become acceptable and accepted if they can safely prevent or accommodate reactivity insertion accidents that could lead to the release of large quantities of mechanical energy, in excess of the reactor containment's capacity. The CADOR approach based on reinforced Doppler reactivity feedback is shown to be an attractive means of effectively preventing such reactivity insertion accidents. The accrued Doppler feedback is achieved by combining two effects: (i) introducing a neutron moderator material in the core so as to soften the neutron spectrum; and (ii) lowering the fuel temperature in nominal conditions so as to increase the margin to fuel melting. This study shows that, by applying this CADOR approach to a Generation-IV oxide-fuelled SFR, the resulting core can be made inherently resistant to reactivity insertion accidents, while also having increased resistance to loss-of-coolant accidents. These preliminary results have to be confirmed and completed to meet multiple safety objectives. In particular, some margin gains have to be found to guarantee against the risk of sodium boiling during unprotected loss of supply power accidents. The main drawback of the CADOR concept is a drastically reduced core power density compared to conventional designs. This has a large impact on core size and other parameters.

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Section: Physical Principle Of the Cador Concept (Reinforced Doppler mentioning

confidence: 99%

CADOR “Core with Adding DOppleR effect” concept application to sodium fast reactors

Zaetta

Fontaine

Sciora

et al. 2019

EPJ Nuclear Sci. Technol.

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“…Here, we compared the dpa levels in long-life fast-reactor cores with and without beryllium in the fuel and reflectors. Beryllium was proposed as an additive to uranium dioxide fuel for light-water reactors in order to improve its thermal conductivity [8], and beryllium reflectors were used in studies of liquid-metal-cooled fast reactors to improve their safety [9,10]. We showed that the addition of beryllium reduced the peak dpa in a mixed-oxide-fueled core from 225 dpa to 203 dpa, and in a metal-fueled core from 273 dpa to 230 dpa.…”

Section: Introductionmentioning

confidence: 96%

Reducing Irradiation Damage in a Long-Life Fast Reactor with Spectral Softening

Osborne

Deinert

2018

Energies

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Long-life fast reactors receive considerable attention for their potential of using uranium efficiently, and because they can operate for extended periods without refueling. However, the main obstacle to achieving maximum operating times and fuel burnup is the neutron radiation damage that accumulates in the cladding and structural materials. Simulations of metal-fueled high-burnup fast reactors showed that the damage in these reactors' cladding material reached 200 displacements per atom (dpa) long before the maximum burnup was achieved. One possibility for overcoming this problem is spectral softening, which would reduce the kinetic energy imparted to reactor materials when neutrons collide with them. In this work, we compared the peak irradiation damage in metaland oxide-fueled fast reactors with that in equivalent reactors containing beryllium in the fuel and reflectors. We showed that the peak damage to the cladding in a metal-fueled reactor was reduced from 273 dpa to 230 dpa when beryllium was included in the core. In an oxide-fueled reactor, the peak damage to the cladding was reduced from 225 dpa to 203 dpa. All four reactors were operated with a core-average burnup of 112 MWd/kg of initial heavy metal (IHM), without reshuffling or refueling, and contained the same initial actinide mass profiles.

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Kinetics, Reactivity Effects, and Control Requirements

Tsvetkov

Waltar

Todd³

2011

Fast Spectrum Reactors

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Values for reactivity effects are required both for transient safety analysis and for control requirements during normal operation. Reactivity effects of importance in fast reactor design and safety include (1) effects of dimensional changes in core geometry, (2) the Doppler effect, (3) effects of sodium density changes or loss of sodium, and (4) long-term reactivity loss from fuel burnup.The reactor control system must compensate for these reactivities during normal operation and provide sufficient margin to handle off-normal situations.We begin this chapter with a review of the reactor kinetics equations (Section 6.2). We then proceed to discuss adjoint flux and perturbation theory (Section 6.3) since these are needed for an understanding of reactivity effects. Kinetics parameters β and l, the effective delayed neutron fraction and the neutron lifetime respectively, are then discussed and the differences in these values between fast and thermal reactors are presented (Section 6.4). Sections 6.5 through 6.7 cover the first three categories of reactivity effects. Section 6.8 is addressed to reactivity worth distribution, and the final section discusses the control requirements for a fast reactor. A detailed discussion of the fourth category of reactivity, that associated with fuel burnup, will be delayed until Chapter 7, although sufficient information will be summarized in this chapter to define the control requirements. Reactor KineticsReactor kinetics equations for both fast and thermal reactors are identical. However, point kinetics approximations can be used more effectively for fast reactors than for thermal reactors because fast reactors are more tightly coupled neutronically. Tighter coupling implies that the neutron flux is more nearly separable in space and time, which is a necessary condition for point kinetics approximations to be valid. Fast reactor safety codes to date have therefore generally employed point kinetics. 1 Inevitably, as commercial fast reactors reach the 1,000-2,000 MWe range, and particularly if they employ heterogeneous cores, problems involving space-time kinetics will arise. Such considerations, however, are beyond the scope of this text.

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Nuclear Performance of Liquid-Metal Fast Breeder Reactors Designed to Preclude Energetic Hypothetical Core Disruptive Accidents

Cited by 4 publications

References 2 publications

CADOR “Core with Adding DOppleR effect” concept application to sodium fast reactors

CADOR “Core with Adding DOppleR effect” concept application to sodium fast reactors

Reducing Irradiation Damage in a Long-Life Fast Reactor with Spectral Softening

Kinetics, Reactivity Effects, and Control Requirements

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