Pakistan’s nuclear technology base that extends from the front-end fuel cycle technologies to enrichment and fuel fabrication can readily extend into the energy domain by taking an initiative on compact and advanced reactors known as the Small Modular Reactors (SMRs) with power production as low as ~20 MWe. Globally, such new and innovative concepts represent a renaissance in nuclear energy with a promising market acceptance. This is therefore an opportune moment for Pakistan to take the initiative and embark upon a program with handsome economic benefits.
Pakistan’s peaceful nuclear program, established in 1956, received its first research reactor, under the “Atoms for Peace” program by the then US President Franklin D. Roosevelt and later in 1969 the Canadian CANDU reactor, the Karachi Nuclear Power Plant (KANUPP-1) was commissioned to produce 137 MWe. In spite of its technological sophistication in nuclear weapons development, Pakistan’s nuclear energy program moved slow and now relies on Chashma I, II and III reactors (300 MWe PWRs each), the vintage KANUPP (137 MWe) and two planned KANUPP II and KANUPP III (PWRs of 1100 MWe capacity each). With a population of 210 million, 21 GW installed capacity, and a “diverse” north-south grid, large parts of the population are still ‘off-grid’ and hence industrial growth is stagnant. The impediments in development, compounded by water scarcity and fears on the future caused by India’s construction of dams on Pakistan’s three eastern rivers compels the country to look for diverse and extensive energy options based on newer technologies.
Currently, there are 447 nuclear power reactors operating globally, with an average installed capacity of 885 MW(e) supplying over 11% of the world’s electricity. This number will increase with the completion of the 52 under-construction reactors to an average installed capacity of ~1050 MW(e). In addition to these, over 54 new designs are under consideration at the lower range, up to 300 MW(e), classified as SMRs by the International Atomic Energy Agency (IAEA).
Thus, impetus for developments towards small size, safe and environmentally acceptable high power density systems has attracted the attention of industry with solutions being presented for market acceptance. Even below the SMR range, considerable work is being carried out on very small modular reactors (vSMR) of ~20 MWe capacity. These micro-nuclear reactors are nearing design completion also in preparation for market acceptance. One such design is “Evinci” by Westinghouse which is being designed to be attractive for decentralized micro-grids. These vSMRs draw heavily from concepts of earlier space programs and incorporate evolutionary, innovative and passive safety features.
The knowledge base for vSMR’s, including the Evinci design, comes from US and the former USSR space nuclear powered systems. NASA is presently, with national laboratories, completing the “Kilopower Reactor using Stirling Technology” (KRUSTY) for missions to moon and Mars. Similar work is also under progress in Russia, China and Europe. In addition to space systems, small nuclear systems form the power base for submarines and surface ships which use smaller more efficient nuclear engines to substitute large volume fuel oils. The revived interest in micro-nuclear power reactors for space exploration focuses on kilowatt systems with minimum moving components such as pumps and turbines. Space reactor concepts have led to small designs that are likely to be attractive for micro-grids due to their small size, mobility and safe and simple operation and maintenance. In such designs, there new options on heat removal technologies and power conversion systems are under development. For heat removal, in a ‘fast’ reactor core, metal coolants such as lithium, potassium and sodium are attractive candidates in two-phase heat pipes for operating without forced convection while for power conversion, options include solid-state thermoelectric generation and the conventional Stirling engine. At higher power levels, better options are the Rankine and Brayton cycles while accounting for size and weight. The operating requirements of both technologies differ vastly in terms of the quality of heat, costs, efficiency, operation and overall simplicity. In such advanced systems, heat removal using lithium in heat pipes is most suitable to provide the required performance for a micro-nuclear reactor of the size of ~ 35 kWe with a uranium fuel inventory of ~149 kg out of which ~104 kg is U-235. The size of such systems is small with the core fitting in a barrel of radius 35 cm and height 40 cm.
With the potential of being the next big future and the new frontier in nuclear power, it is within the reach of Pakistan’s expertise if the initiative is taken at this opportune moment
Such non-commercial systems form the basis on which small nuclear reactors could replace power systems in decentralized micro-grids. Examples of commercially viable factory manufactured and easily transportable systems are Evinci and NuScale which could soon gain market acceptance. These are larger than space systems with ~2400 kWt, 120 kWe 70% enriched Uranium Nitride (UN) fueled reactor with 310 kg core and a thermoelectric generator (TEG). An advantage of using high-density UN fuel is a reduction in the core size. In another conceptual design, a 500 kWt, 25 kWe 65% enriched UN fueled Heat pipe reactor (HPR) is given with a core weight also of 310 kg.
Pakistan’s case for the development of vSMR’s is strong for the following reasons: one, development of specific-purpose compact nuclear plants for defense establishments and space satellites; two, getting leverage on indigenization of the development of off-grid nuclear energy stations; three, utilization of KRL fuel enrichment facilities for production of LEU and HEU fuel in small quantities; four, realizing commercial benefits from the sale of vSMR’s for specific non-military applications such as desalination and cogeneration.
For Pakistan, the development of a vSMR would be a natural extension of its capabilities in most technologies required for its’ development. Ground-based vSMRs would use LEU while for space or specialized applications requiring small size, HEU, possibly as high as 70% enriched U235, would be required. Thus, fuel for both cases would be available from national labs.
The materials required would depend on the design selected, in case of “thermal” systems,” the experience of moderator, coolant, and power conversion from CHASNUPP would be relevant while for “fast” systems, new facilities such as advanced fuel manufacturing facilities, liquid metal coolants and electromagnetic pumps would be required. Space systems, of the “fast” HEU specifications, would also require cermet fuels, metal liquids in heat pipes, power conversion based on thermoelectric generators or Sterling cycles and high-temperature materials such as zirconium alloys with molybdenum rhenium compounds, beryllium oxide reflectors, and shielding such as tungsten and lead. It is anticipated that within the next decade, such SMRs will gain widespread market acceptance. With the potential of being the next big future and the new frontier in nuclear power, it is within the reach of Pakistan’s expertise if the initiative is taken at this opportune moment.
Zafar ullah Koreshi is a professor in the Department of Mechatronics Engineering at Air University, Islamabad. Rizwana Abbasi is an associate professor in the Department of International Relations at National University of Modern Languages, Islamabad