Impact of PWR spent fuel variations on back-end features of advanced fuel cycles with tru-fueled VHTRs Ayodeji B. Alajo ⇑ , Pavel V. Tsvetkov Department of Nuclear Engineering, Texas A&M University, 129 Zachry Engineering Center, MS 3133 TAMU, College Station, TX 77843-3133, USA article info Article history: Received 26 April 2010 Accepted 18 August 2010 Available online 9 September 2010 Keywords: VHTR Advanced fuel Nuclear waste management Transmutation abstract Alternative strategies are being considered as management option for current spent nuclear fuel transu- ranics (TRU) inventory. Creation of transmutation fuels containing TRU for use in thermal and fast reac- tors is one of the viable strategies. Utilization of these advanced fuels will result in transmutation and incineration of the TRU. The objective of this study is to analyze the impact of conventional PWR spent fuel variations on TRU-fueled very high temperature reactor (VHTR) systems. The current effort is focused on prismatic core configuration operated under a single batch once-through fuel cycle option. IAEA’s nuclear fuel cycle simulation system (VISTA) was used to determine potential PWR spent fuel composi- tions. Additional composition was determined from the analysis of United States legacy spent fuel that is given in the Yucca Mountain Safety Assessment Report. A detailed whole-core 3-D model of the prismatic VHTR was developed using SCALE5.1 code system. The fuel assembly block model was based on Japan’s HTTR fuel block configuration. To establish a reference reactor system, calculations for LEU-fueled VHTR were performed and the results were used as the basis for comparative studies of the TRU-fueled systems. The LEU fuel is uranium oxide at 15% 235 U enrichment. The results showed that the single-batch core life- times ranged between 5 and 7 years for all TRU fuels (3 years in LEU), providing prolonged operation on a single batch fuel loading. Transmutation efficiencies ranged between 19% and 27% for TRU-based fuels (13% in LEU). Total TRU material contents for disposal ranged between 730 and 808 kg per metric ton of initial heavy metal loading, reducing TRU inventory mass by as much as 27%. Decay heat and source terms of the discharged fuel were also calculated as part of the spent fuel disposal consideration. The results indicated strong potential of TRU-based fuel in VHTRs. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction This paper is part of a body of work performed to investigate the potential use of TRU-based advanced fuels in a Generation IV nu- clear energy system. The focus herein is the impact of a TRU-fueled system on the back-end of the nuclear fuel cycle. This is analyzed vis-à-vis the current LWR back-end scenario. 1.1. Spent fuel management The United States’ spent nuclear fuel (SNF) inventory is primarily from LWRs in Commercial nuclear power plants. The United States does not reprocess commercial SNF – a decision made in the 1970s. The SNFs are currently stored on-site awaiting final disposal at a repository. The present renaissance in nuclear energy has prompted consideration of SNF reprocessing to insure nuclear energy sustain- ability. The TRU recovered through reprocessing can be fabricated into advanced fuels for use in new reactors in the near future. 1.2. Advanced fuels The long term radiotoxicity concerns associated with SNF are attributable to its HLW, which consists of long-lived fission prod- ucts (LLFP) and TRU. Assuming reprocessing, the recovered TRU holds potential source of energy in its fissile and fertile nuclides. The ability to tap into the latent energy held by the TRU requires deployment of technologies for the fabrication of TRU into usable fuel forms (USDOE, 2003a). This is the subject of advanced fuel de- sign, which is outside the scope of this study. The advanced fuels fabricated from the TRU will provide a means of destruction of the toxic nuclides while deriving addi- tional benefits from the energy recovered through its utilization (USDOE, 2003a). It should be noted that the new fuels will be sig- nificantly difference from existing uranium based fuels. Hence the advanced fuels may need to be deployed in new reactor systems. 1.3. Advanced nuclear systems An international collaborative effort led by the United States Department of Energy (DOE) established the Generation IV 0306-4549/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.anucene.2010.08.013 ⇑ Corresponding author. E-mail address: dejialajo@neo.tamu.edu (A.B. Alajo). Annals of Nuclear Energy 38 (2011) 88–97 Contents lists available at ScienceDirect Annals of Nuclear Energy journal homepage: www.elsevier.com/locate/anucene