Burnable Poison Designs for a Soluble-Boron-Free Civil Nuclear Marine PWR Core


In an effort to de-carbonise commercial freight shipping, there is growing interest in the possibility of using nuclear propulsion systems. Nuclear-powered propulsion allows ships to operate with low fuel costs, long intervals between refueling, and minimal emissions; however, currently these systems remain largely confined to military vessels. It is highly desirable that a civil marine core not use soluble boron for reactivity control, but it is then a challenge to achieve an adequate shutdown margin throughout the core life while maintaining reactivity control and acceptable power distributions in the core. We have considered several potential and novel burnable poison (BP) design strategies for reactivity control in this study: (Case 1) a composite BP: gadolinia (Gd2O3) or erbia (Er2O3) with 150 μm thickness ZrB2 integral fuel burnable absorber (IFBA); (Case 2) Pu-240 or Am-241 mixed homogeneously with the fuel; and (Case 3) another composite BP: Pu-240 or Am-241 with 150 μm thickness ZrB2 IFBA. The results are compared against those for a high-thickness 150 μm 25 IFBA pins1 design from a previous study. We arrive at a design using 15% U-235 fuel loaded into 13 x 13 assemblies with Case 3 BPs for reactivity control. Taking advantage of self-shielding effects, this design maintains low and stable assembly reactivity with minimal burnup penalty. Case 3 provides ∼10% more initial reactivity suppression with ∼70% less reactivity swing compared to the IFBA-only design for UO2 fuel while achieving almost the same cycle length. Finally, optimized Case 3 assemblies were loaded into a 3D reactor model in PANTHER. The PANTHER results show that the designed core can achieve the target lifetime of 15 years while minimizing the reactivity swing to a greater extent and providing a ∼30% lower radial form factor and ∼28% lower total peaking factor compared to the IFBA-only core.

Meeting Name

Physics of Reactors 2016, PHYSOR 2016: Unifying Theory and Experiments in the 21st Century (2016: May 1-5, Sun Valley, ID)


Nuclear Engineering and Radiation Science

Keywords and Phrases

Boron; Nuclear propulsion; Pressurized water reactors; Propulsion; Reactor shielding; Ship propulsion; Ships; Burnable absorber; Burnable poisons (BP); Design strategies; Military vessels; Nuclear propulsion system; Power distributions; Reactivity control; Self shielding effect; Fuels; Civil marine propulsion; Composite BP; Soluble-boron-free (SBF) design

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


File Type





© 2016 American Nuclear Society (ANS), All rights reserved.

Publication Date

05 May 2016

This document is currently not available here.