in boiling water reactor moderator is mcq

Can operate at lower core power density levels using natural circulation without forced flow. So it uses natural uranium as the fuel and heavy water as the moderator. Boiling Water Reactor (BWR) BWR is a light water reactor using ordinary water as coolant and moderator similar to the PWR except it only has a single circuit connecting the reactor and the turbine without a steam generator. [12] Since the BWR is boiling water, and steam does not transfer heat as well as liquid water, MFLCPR typically occurs at the top of a fuel assembly, where steam volume is the highest. This is done through uranium enrichment—which increases the concentration of Uranium-235 from 0.7% to around 4%. Which of the following statement is true? C Heavy water is used both as coolant as well as moderator . C. pressurised water is pumped into the core. 77. October 20, 2020 by Admin. Take the Quiz for competitions and exams. Reactors designed for propulsion applications are designed for. The "wet" steam goes through a tortuous path where the water droplets are slowed and directed out into the downcomer or annulus region. So as to prevent this from happening, it is required that the decay heat stored in the fuel assemblies at any one time does not overwhelm the ECCS. From about 0.5% power to 100% power, feedwater will automatically control the water level in the reactor. In comparison, there is no significant boiling allowed in a pressurized water reactor (PWR) because of the high pressure maintained in its primary loop—approximately 158 atm (16 MPa, 2300 psi). D. No moderate is used. During the first nuclear heatup, nuclear fuel pellets can crack. a) Regenerative reactor. As flow of water through the core is increased, steam bubbles ("voids") are more quickly removed from the core, the amount of liquid water in the core increases, neutron moderation increases, more neutrons are slowed to be absorbed by the fuel, and reactor power increases. Nuclei with low mass numbers are most effective for this purpose, so the moderator is always a low-mass-number material. In this double failure scenario, assumed to be extremely unlikely prior to the. Water in the reactor is kept at a lower pressure of about 75 bars such that it will boil at about 285 degree C. Larger pressure vessel than for a PWR of similar power, with correspondingly higher cost, in particular for older models that still use a main steam generator and associated piping. [citation needed] That is, there would need to be 3 million ESBWRs operating before one would expect a single core-damaging event during their 100-year lifetimes. a. 7. (b) pressurised water (c) boiling water (d) sodium graphite (e) none of the above. The "dry" steam then exits the RPV through four main steam lines and goes to the turbine. Q14. 78. Which of the following is used as a moderator in nuclear power plants? (c) boiling water (d) sodium graphite (e) none of the above. A BWR can be designed with no recirculation pumps and rely entirely on the thermal head to recirculate the water inside of the RPV. Enriched uranium is required as a fuel in a nuclear reactor, if light water is used as moderator and coolant, because light water has (A) High neutron absorption cross-section (B) Low moderating efficiency (C) High neutron scatter cross-section (D) Low neutron absorption cross-section Ans: a. At the top of the riser area is the moisture separator. This concern led to the US's first research effort in nuclear power being devoted to the PWR, which was highly suited for naval vessels (submarines, especially), as space was at a premium, and PWRs could be made compact and high-power enough to fit in such, in any event. At low power conditions, the feedwater controller acts as a simple PID control by watching reactor water level. Multiple Choice Question (MCQ) of Electronics page-17:241. The ABWR was developed in the late 1980s and early 1990s, and has been further improved to the present day. APLHGR is monitored to ensure that the reactor is not operated at an average power level that would defeat the primary containment systems. The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator – furthermore a solid form of fissile elements is used as fuel. c) Heavy water. (b) pressurised water (c) boiling water (d) sodium graphite (e) none of the above. b. Coolant water boils in the core of the reactor . For new fuel, this limit is typically around 13 kW/ft (43 kW/m) of fuel rod. The first nuclear power plant in India is located at. In a nuclear power station using boiling water reactor (BWR), water used as, 13. 3. Dense water C. Fresh water D. Heavy water. The coolant water boils in the core of the reactor. Another example was the Isolation Condenser system, which relied on the principle of hot water/steam rising to bring hot coolant into large heat exchangers located above the reactor in very deep tanks of water, thus accomplishing residual heat removal. Most of the radioactivity in the water is very short-lived (mostly N-16, with a 7-second half-life), so the turbine hall can be entered soon after the reactor is shut down. Cost of fuel used is much lower than that used in pressurized water or boiling water reactor. The coolant water is pressurised to work as moderator. For example, if the reactor got too hot, it would trigger a system that would release soluble neutron absorbers (generally a solution of borated materials, or a solution of borax), or materials that greatly hamper a chain reaction by absorbing neutrons, into the reactor core. This also requires more instrumentation in the reactor core. When the voids collapse in the reactor, the fission reaction is encouraged (more thermal neutrons); power increases drastically (120%) until it is terminated by the automatic insertion of the control rods. Q7. It is contained in a pressurized piping loop. Reactor pressure in a BWR is controlled by the main turbine or main steam bypass valves. Lower risk (probability) of a rupture causing loss of coolant compared to a PWR, and lower risk of core damage should such a rupture occur. In a nuclear power station using boiling water reactor (BWR), water used as. In the boiling water reactor the same water loop serves as moderator, coolant for the core, and steam source for the turbine.. In a BWR, ordinary water acts as both coolant and moderator. Yet another example was the omission of recirculation pumps within the core; these pumps were used in other BWR designs to keep cooling water moving; they were expensive, hard to reach to repair, and could occasionally fail; so as to improve reliability, the ABWR incorporated no less than 10 of these recirculation pumps, so that even if several failed, a sufficient number would remain serviceable so that an unscheduled shutdown would not be necessary, and the pumps could be repaired during the next refueling outage. B. NRC assessments of limiting fault potentials indicate if such a fault occurred, the average BWR would be less likely to sustain core damage than the average PWR due to the robustness and redundancy of the. Typical computer simulations divide the reactor core into 24–25 axial planes; relevant quantities (margins, burnup, power, void history) are tracked for each "node" in the reactor core (764 fuel assemblies x 25 nodes/assembly = 19100 nodal calculations/quantity). Enriched uranium is required as a fuel in a nuclear reactor, if light water is used as moderator an... Hydraulics and Fluid Mechanics MCQ - … Approximately 22% of the nuclear reactors installed in the different nuclear power plants use the BWR reactor.. ), The power control by reduction of the moderator density (vapour bubbles in the water) instead of by addition of neutron absorbers (boric acid in PWR) leads to, Due to their single major vendor (GE/Hitachi), the current fleet of BWRs have predictable, uniform designs that, while not completely standardized, generally are very similar to one another. Learn Power Plant Engineering MCQ questions & answers are available for a Mechanical Engineering students to clear GATE exams, various technical interview, competitive examination, and another entrance exam. A boiling water reactor vessel contains two primary pieces: the reactor core and the steam dryer assembly. Categories Mechanical Engineering MCQs Post navigation. Foxoyo MCQs. Submitted by: Farjan Ahmed Soomro. Light Water Reactors Boiling Water Reactor This section describes boiling water nuclear reactors . Their approach is to simulate worst case events when the reactor is in its most vulnerable state. January 1977. Parallel to the development of the ABWR, General Electric also developed a different concept, known as the simplified boiling water reactor (SBWR). Experimental data is conservatively applied to BWR fuel to ensure that the transition to film boiling does not occur during normal or transient operation. PCIOMR analysis look at local power peaks and xenon transients which could be caused by control rod position changes or rapid power changes to ensure that local power rates never exceed maximum ratings. The water then goes through either jet pumps or internal recirculation pumps that provide additional pumping power (hydraulic head). c) Pressurized water. The feedwater subcools the saturated water from the moisture separators. eval(ez_write_tag([[300,250],'electricalvoice_com-large-leaderboard-2','ezslot_12',123,'0','0'])); 10. 5. A. acts both as an efficient coolant as well as a moderator. 1 Country with the highest uranium resources; 2 Nuclear power plants approximately consume how many gallons of water per MWh; 3 Reactors which don’t need a moderator; 4 Boiling water reactor contains number of loops; 5 AGR reactors use which coolant This may be due to the fact that BWRs are ideally suited for peaceful uses like power generation, process/industrial/district heating, and desalinization, due to low cost, simplicity, and safety focus, which come at the expense of larger size and slightly lower thermal efficiency. Then, either all of the A control rods or B control rods are pulled full out in a defined sequence to create a "checkerboard" pattern. Q6. Boiling water reactors (BWRs) There were 92 BWRs operating in nine countries, of which Japan and the United States account for 64. If the core is uncovered for too long, fuel failure can occur; for the purpose of design, fuel failure is assumed to occur when the temperature of the uncovered fuel reaches a critical temperature (1100 °C, 2200 °F). Moderator but not as a coolant; Coolant but not as a moderator; Both moderator and coolant C. The coolant water is pressurised to prevent boiling of water in the core. Ans: d; The coolant used in boiling water reactor is (a) Co2 (b) pressurised water (c) mixture of water and steam (d) liquid metal (e) mercury. Boiling water reactor uses the following as moderator, coolant and working fluid (a) ordinary fluid (b) heavy water (c) molten lead (d) hydrogen gas (e) none of the above. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR), which is also a type of light water nuclear reactor. This is because light water absorbs too many neutrons to be used with natural uranium, so the fuel content of fissile Uranium-235 must be increased. [9] This extraordinarily low CDP for the ESBWR far exceeds the other large LWRs on the market. Water exiting the fuel channels at the top guide is saturated with a steam quality of about 15%. The relative properties of these materials are compared below. b) The saturation voltage V CE for germanium transistor is more than silicon transistor. (a) Interference with spawing and migration of fish (b) Pollution and health hazard in the estuary due to blockage of flow of polluted water into the sea (c) Navigational hazard Reactor water level is controlled by the main feedwater system. During film boiling a volume of insulating vapor separates the heated surface from the cooling fluid; this causes the temperature of the heated surface to increase drastically to once again reach equilibrium heat transfer with the cooling fluid. The tank containing the soluble neutron absorbers would be located above the reactor, and the absorption solution, once the system was triggered, would flow into the core through force of gravity, and bring the reaction to a near-complete stop. 20.2 Features and types of boiling water reactors – boiling water reactor (BWR) and advanced boiling water reactor (ABWR) A BWR plant utilizes enriched uranium (about 3%) as fuel and light water as coolant/moderator. 1) coolant water boils in the core of the reactor., 2) fuel is natural uranium and heavy water acts both as moderator & coolant., 3) use of moderator is not required, 4) coolant water is pressurised to prevent bulk boiling of water in the core, 5) NULL BPWS separates control rods into four groups, A1, A2, B1, and B2. 211) A boiling water reactor is the one, in which the. Answer/ Hint The probability that fission will occur depends on incident neutron energy. (d) to prevent the water coolant from boiling in the core (e) to eliminate the coolant loop of the pressurised water. General Electric Corporation, CS1 maint: BOT: original-url status unknown (, Learn how and when to remove this template message, Economic Simplified Boiling Water Reactor, reduced moderation boiling water reactors, "Core damage frequency perspectives for BWR 3/4 and Westinghouse 4-loop plants based on IPE results", "Upgrade your BWR recirc pumps with adjustable-speed drives", https://www.osti.gov/servlets/purl/4115425, "Advanced Boiling Water Reactor (ABWR) fact sheet", https://www.nrc.gov/reactors/new-reactors/design-cert/esbwr.html, "Next-generation nuclear energy: The ESBWR", COMMENTARY: Crucial vents were not installed until 1990s, Boiling Water Reactors, US Nuclear Regulatory Commission, "Technical details and features of Advanced BWRs", Small sealed transportable autonomous (SSTAR), https://en.wikipedia.org/w/index.php?title=Boiling_water_reactor&oldid=995062277, Short description is different from Wikidata, Articles needing additional references from July 2011, All articles needing additional references, Pages using multiple image with auto scaled images, Articles with unsourced statements from August 2015, Articles with unsourced statements from March 2011, Articles needing expert attention from December 2014, Technology articles needing expert attention, CS1 maint: BOT: original-url status unknown, Creative Commons Attribution-ShareAlike License. Because they are hot both radioactively and thermally, this is done via cranes and under water. Most significantly, the ABWR was a completely standardized design, that could be made for series production.[7]. But other researchers wanted to investigate whether the supposed instability caused by boiling water in a reactor core would really cause instability. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR), which is also a type of light water nuclear reactor. In a pressurised water reactor (PWR) A. Out of the following plant categories: eval(ez_write_tag([[250,250],'electricalvoice_com-box-4','ezslot_6',121,'0','0'])); 6. Within the reactor core, a nuclear reaction is started to produce heat. At high power conditions, the controller is switched to a "Three-Element" control mode, where the controller looks at the current water level in the reactor, as well as the amount of water going in and the amount of steam leaving the reactor. Reportedly, this design has been advertised as having a core damage probability of only 3×10−8 core damage events per reactor-year. Ans: a. Unlike a PWR, where the turbine steam demand is set manually by the operators, in a BWR, the turbine valves will modulate to maintain reactor pressure at a setpoint. By using the water injection and steam flow rates, the feed water control system can rapidly anticipate water level deviations and respond to maintain water level within a few inches of set point. Reactor start up (criticality) is achieved by withdrawing control rods from the core to raise core reactivity to a level where it is evident that the nuclear chain reaction is self-sustaining. 36. 3rd generation BWRs: BWR/6 with Mark-III containment. The nuclear power plant at Tarapur has the following reactor. The BWR uses ordinary water (light water) as both its coolant and its moderator. Ans: c 35. The main difference between a BWR and PWR is that in a BWR, the reactor core heats water, which turns to steam and then drives a steam turbine. Due to the limitations of the manual control system, it is possible while starting-up that the core can be placed into a condition where movement of a single control rod can cause a large nonlinear reactivity change, which could heat fuel elements to the point they fail (melt, ignite, weaken, etc.). In the boiling water reactor (BWR), the water which passes over the reactor core to act as moderator and coolant is also the steam source for the turbine. 36. This is known as "going critical". Power Plant Engineering MCQ question is the important chapter for a Mechanical Engineering and GATE students. 16MPa). Electrical Engineering MCQ. The moderator used in fast breeder reactor is. a) The saturation voltage V CF of silicon transistor is more than germanium transistor. 1 Country with the highest uranium resources; 2 Nuclear power plants approximately consume how many gallons of water per MWh; 3 Reactors which don’t need a moderator; 4 Boiling water reactor contains number of loops; 5 AGR reactors use which coolant eval(ez_write_tag([[336,280],'electricalvoice_com-banner-1','ezslot_11',122,'0','0'])); 8. Apart from the GE designs there were others by ABB, MITSU, Toshiba and KWU. all (a), (b) and (c). Getting started. b) Fast breeder reactor. d) Any type of uranium . Older BWR designs use a manual control system, which is usually limited to controlling one or four control rods at a time, and only through a series of notched positions with fixed intervals between these positions. The ABWR was approved by the United States Nuclear Regulatory Commission for production as a standardized design in the early 1990s. eval(ez_write_tag([[250,250],'electricalvoice_com-leader-1','ezslot_13',124,'0','0'])); 12. A boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power. For the equation of state, see, Type of nuclear reactor that directly boils water, Cross-section sketch of a typical BWR Mark I containment, Economic simplified boiling water reactor, Maximum fraction limiting critical power ratio (MFLCPR), Fraction limiting linear heat generation rate (FLLHGR), Average planar linear heat generation rate (APLHGR), Pre-Conditioning Interim Operating Management Recommendation (PCIOMR), NEDO-21231, "Banked Position Withdrawal Sequence," The steam reheaters take some of the reactor's steam and use it as a heating source to reheat what comes out of the high-pressure turbine exhaust. In the BWR the water in the reactor core is permitted to boil under a pressure of 75 atmospheres, raising the boiling point to 285°C and the steam generated is used directly to drive a steam turbine. MCQ quiz on Nuclear Power Plant multiple choice questions and answers on Nuclear Power Plant MCQ questions on Nuclear Power Plant objectives questions with answer test pdf for interview preparations, ... boiling water reactor ... Gas cooled reactor uses following materials as moderator, and coolant . The reactor vessel and associated components operate at a substantially lower pressure of about 70–75 bars (1,020–1,090 psi) compared to about 155 bars (2,250 psi) in a PWR. The condensate is then pumped through feedwater heaters that raise its temperature using extraction steam from various turbine stages. The ultimate result of the passive safety features of the SBWR would be a reactor that would not require human intervention in the event of a major safety contingency for at least 48 hours following the safety contingency; thence, it would only require periodic refilling of cooling water tanks located completely outside of the reactor, isolated from the cooling system, and designed to remove reactor waste heat through evaporation. In a BWR, ordinary water acts as both coolant and moderator. They are cooled and moderated by high-pressure liquid water (e.g. The height of this region may be increased to increase the thermal natural recirculation pumping head. Larger-scale tests were conducted through the late 1950s/early/mid-1960s that only partially used directly-generated (primary) nuclear boiler system steam to feed the turbine and incorporated heat exchangers for the generation of secondary steam to drive separate parts of the turbines. 12. As control rods are inserted, neutron absorption increases in the control material and decreases in the fuel, so reactor power decreases. The remaining fuel assemblies are shuffled to new core locations to maximize the efficiency and power produced in the next fuel cycle. When the turbine is offline or trips, the main steam bypass/dump valves will open to direct steam directly to the condenser. Several calculated/measured quantities are tracked while operating a BWR: MFLCPR, FLLHGR, and APLHGR must be kept less than 1.0 during normal operation; administrative controls are in place to assure some margin of error and margin of safety to these licensed limits. 36. Correct Answer : D. One development spurred by the success of the ABWR in Japan is that General Electric's nuclear energy division merged with Hitachi Corporation's nuclear energy division, forming GE Hitachi Nuclear Energy, which is now the major worldwide developer of the BWR design. APLHGR is commonly pronounced as "Apple Hugger" in the industry. BWR designs incorporate failsafe protection systems to rapidly cool and make safe the uncovered fuel prior to it reaching this temperature; these failsafe systems are known as the Emergency Core Cooling System. Moderator in nuclear plants is used to (a) reduce temperature (b) extract heat from nuclear reaction (c) control the reaction (d) cause collision with the fast moving neutrons to reduce their speed (e) moderate the radioactive pollution. Nuclear fuel could be damaged by film boiling; this would cause the fuel cladding to overheat and fail. Lack of standardization remains a problem with PWRs, as, at least in the United States, there are three design families represented among the current PWR fleet (Combustion Engineering, Westinghouse, and Babcock & Wilcox), within these families, there are quite divergent designs. In boiling water reactor, moderator is . The heating from the core creates a thermal head that assists the recirculation pumps in recirculating the water inside of the RPV. See List of boiling water reactors. The moderator, which is of importance in thermal reactors, is used to moderate, that is, to slow down, neutrons from fission to thermal energies. However, like any system, the ECCS has limits, in this case, to its cooling capacity, and there is a possibility that fuel could be designed that produces so much decay heat that the ECCS would be overwhelmed and could not cool it down successfully. Fuel is natural uranium and heavy water acts both as moderator & coolant B. Coolant water boils in the core of the reactor C. Coolant water is pressurised to prevent bulk boiling of water in the core D. Use of moderator is not required MCQ quiz on Nuclear Power Plant multiple choice questions and answers on Nuclear Power Plant MCQ questions on Nuclear Power Plant objectives questions with answer test pdf for interview preparations, freshers jobs, and competitive exams. In the Fukushima reactor incident this became problematic because water was lost from one or more spent fuel pools and the earthquake could have altered the geometry.

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