Interaction study between MOX fuel and eutectic lead–bismuth coolant

Abstract

h i g h l i g h t s g r a p h i c a l a b s t r a c t Interaction tests are performed between U 0.7 Pu 0.3 O 2 fuel and Pb 0.45 Bi 0.55 liquid metal coolant. Oxygen concentration in liquid metal, stoichiometry of the MOX and interaction temperature are studied. No chemical reaction detected. Less than 0.01% to 0.65% of the pellets is released into the coolant depending to the conditions. a b s t r a c tIn the frame of the MYRRHA reactor project, the interaction between fuel pellets and the reactor coolant is essential for safety evaluations, e.g. in case of a pin breach. Therefore, interaction tests between uraniumeplutonium mixed oxide (MOX) pellets and molten lead bismuth eutectic (LBE) have been performed and three parameters were studied, namely the interaction temperature (500 C and 800 C), the oxygen content in LBE and the stoichiometry of the MOX (U 0.7 Pu 0.3 O 2Àx and U 0.7 Pu 0.3 O 2.00 ). After 50 h of interaction in closed containers, the pellet integrity was preserved in all cases. Whatever the conditions, neither interaction compounds (crystalline or amorphous) nor lead and bismuth diffusion into the surface regions of the MOX pellets has been detected. In most of the conditions, actinide releases into LBE were very limited (in the range of 0.01e0.15 mg), with a homogeneous release of the different actinides present in the MOX. Detected values were significantly higher in the 800 C and low LBE oxygen content tests for both U 0.7 Pu 0.3 O 2Àx and U 0.7 Pu 0.3 O 2.00 , with 1e2 mg of actinide released in these conditions.

Further insights into the chemistry of the Bi–U–O system

“…The HR-XANES spectrum of U IV O 2 has a pronounced peak at 3724.5 (2) eV, due to the electronic transitions from the 3d 3/2 core level to the unoccupied 5f states. The (U IV ,U V ) 4 O 9 HR-XANES spectrum depicts a peak at the same energy position characteristic of U IV and also a peak at 3725.5 (2) eV which corresponds to U V . The (U V ,U VI ) 3 O 8 HR-XANES spectrum exhibits a white line at 3726.2 (2) eV attributed to U VI and a shoulder at the lower energy side with energy position characteristic for U V .…”

“…1 Thus, the phase relations in the Pb-Bi-U-Pu-O system should be studied in detail, in order to identify possible phases that could be formed during inadvertent fuel (MOX)coolant (LBE) interactions. 2 Very few compounds have been identified in the Bi-U-O ternary system to date. Bismuth(III) monouranate, Bi 2 U VI O 6 , is the only compound well characterized from a crystallographic point of view and has been prepared by several high-and lowtemperature procedures.…”

Uranosphaerite: Crystal structure, hydrogen bonding, mechanics, infrared and Raman spectroscopy and thermodynamics

“…Bismuth has also been proposed as a coolant (or as a combined fuel and coolant) to transfer the heat generated in a reactor to the working fluid of a heat engine [1][2]. Liquid bismuth and several closely related heavy liquid metals, including the lead-bismuth eutectic (LBE), are been considered as coolants for Generation IV fast reactors [10][11][12][13][14][15][16][17][18][19][20]. The use of LBE as coolant in uranium-plutonium mixed oxide (MOX) fueled reactors has been assessed [17].…”

“…Liquid bismuth and several closely related heavy liquid metals, including the lead-bismuth eutectic (LBE), are been considered as coolants for Generation IV fast reactors [10][11][12][13][14][15][16][17][18][19][20]. The use of LBE as coolant in uranium-plutonium mixed oxide (MOX) fueled reactors has been assessed [17]. The formation of a protective oxide layer on the steel surfaces in lead bismuth eutectic (LBE) cooled reactors to mitigate their corrosion has been investigated extensively [18][19].…”

Survey of Uranium Nitride and Mixed Oxide Fuels for Microreactor Applications

“…The relatively low thermal conductivity of helium does not cause much issue as smeared density of MOX fuel is higher than metallic fuel (that is narrower gap between MOX pellets and cladding) and MOX has a much higher maximum operating temperature [41]. Also, as liquid lead is compatible with MOX, it may be considered as the bonding material if needed for certain microreactor designs [42].…”