<p class="Paragraph SCXW223396562 BCX7" style="margin: 0px; padding: 0px; font-weight: normal; font-style: normal; vertical-align: baseline; background-color: transparent; color: windowtext; text-align: justify; text-indent: 0px">Development of a&nbsp;modular&nbsp;low-temperature&nbsp;PWR&nbsp;for district heating applications&nbsp;was recently started at VTT Technical Research Centre of Finland.&nbsp;The reactor design combines conventional&nbsp;PWR technology with innovative&nbsp;containment function and&nbsp;passive&nbsp;decay&nbsp;heat removal. This paper covers the neutronics design analyses and fuel cycle simulations&nbsp;carried out for&nbsp;a core variant&nbsp;producing 50 MW heat at low temperature.&nbsp;&nbsp;A general overview of the technology,&nbsp;and&nbsp;thermal-hydraulic design&nbsp;and safety&nbsp;analyses&nbsp;are&nbsp;addressed in separate papers submitted to the ICONE 28 conference.&nbsp;<p class="Paragraph SCXW223396562 BCX7" style="margin: 0px; padding: 0px; font-weight: normal; font-style: normal; vertical-align: baseline; background-color: transparent; color: windowtext; text-align: justify; text-indent: 0px">&nbsp;<p class="Paragraph SCXW223396562 BCX7" style="margin: 0px; padding: 0px; font-weight: normal; font-style: normal; vertical-align: baseline; background-color: transparent; color: windowtext; text-align: justify; text-indent: 0px">The core physics calculations&nbsp;in this study&nbsp;were carried out using&nbsp;the Kraken computational framework, developed at VTT since 2017. Kraken is essentially a versatile multi-physics platform,&nbsp;designed for coupling&nbsp;neutronics, thermal hydraulics and fuel behavior solvers&nbsp;into&nbsp;various high-fidelity and reduced-order computational sequences. The solvers used in this study include the Ants nodal neutronics code, the Kharon&nbsp;closed-channel thermal hydraulics solver and the&nbsp;FINIX&nbsp;fuel behavior module.&nbsp;Group constants&nbsp;for Ants were produced using the Serpent Monte Carlo code. The objectives of the study&nbsp;were: 1)&nbsp;to&nbsp;provide proof-of-concept type demonstration that the&nbsp;Kraken&nbsp;framework can be used for the&nbsp;core physics analyses&nbsp;of the&nbsp;district heating reactor,&nbsp;and 2)&nbsp;to&nbsp;show&nbsp;that&nbsp;the fundamental safety requirements&nbsp;are met for the&nbsp;basic&nbsp;core design. Since the reactor core&nbsp;is comprised of conventional PWR fuel&nbsp;without any exotic design features, the&nbsp;main focus&nbsp;in the&nbsp;study was in the first objective.&nbsp;<p class="Paragraph SCXW223396562 BCX7" style="margin: 0px; padding: 0px; font-weight: normal; font-style: normal; vertical-align: baseline; background-color: transparent; color: windowtext; text-align: justify; text-indent: 0px">&nbsp;<p class="Paragraph SCXW223396562 BCX7" style="margin: 0px; padding: 0px; font-weight: normal; font-style: normal; vertical-align: baseline; background-color: transparent; color: windowtext; text-align: justify; text-indent: 0px">The&nbsp;low operating temperature&nbsp;and high moderator density&nbsp;of the district heating reactor has some effect on the neutronics characteristics&nbsp;of the&nbsp;core.&nbsp;To ensure that the moderator temperature coefficient remains negative, the reactor was designed to&nbsp;be&nbsp;operated without soluble boron. Reactivity control&nbsp;is instead&nbsp;accomplished by movable control rods and burnable absorbers. Another unconventional feature is the relatively low power density compared to&nbsp;traditional&nbsp;PWRs, leading to&nbsp;slow accumulation of fuel burnup, and, consequently, long operating cycle.&nbsp;The Kraken framework was successfully used for simulating the operating cycles from initial core to equilibrium. Feedback coefficients, shut-down margins and other safety-related parameters remained well within their acceptable limits.&nbsp;

A Finnish District Heating Reactor: Neutronics Design and Fuel Cycle Simulations

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.

A Finnish District Heating Reactor: Neutronics Design and Fuel Cycle Simulations

A Finnish District Heating Reactor: Neutronics Design and Fuel Cycle Simulations