in boiling water reactor moderator is mcq

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. 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. There are several different types of moderating materials, and each have places where they are used more effectively. 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. The probability that fission will occur depends on incident neutron energy. In a PWR, the reactor core heats water, which does not boil. Within the reactor core, a nuclear reaction is started to produce heat. In a nuclear power station, the moderator is used to. Ans: a. Apart from the GE designs there were others by ABB, MITSU, Toshiba and KWU. Boiling Water Reactor. The ABWR was approved by the United States Nuclear Regulatory Commission for production as a standardized design in the early 1990s. Contamination of the turbine by short-lived, Though the present fleet of BWRs is said to be less likely to suffer core damage from the "1 in 100,000 reactor-year" limiting fault than the present fleet of PWRs (due to increased ECCS robustness and redundancy), there have been concerns raised about the pressure containment ability of the as-built, unmodified Mark I containment – that such may be insufficient to contain pressures generated by a limiting fault combined with complete ECCS failure that results in extremely severe core damage. Differently from the PWR, in a BWR the control rods (boron carbide plates) are inserted from below to give a more homogeneous distribution of the power: in the upper side the density of the water is lower due to vapour formation, making the neutron moderation less efficient and the fission probability lower. (d) to prevent the water coolant from boiling in the core (e) to eliminate the coolant loop of the pressurised water. 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. The coolant water boils in the core of the reactor. [9] This extraordinarily low CDP for the ESBWR far exceeds the other large LWRs on the market. B. As control rods are withdrawn, neutron absorption decreases in the control material and increases in the fuel, so reactor power increases. A pressurized water reactor (PWR) is a type of light-water nuclear reactor.PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being Japan and Canada). Q16. In this double failure scenario, assumed to be extremely unlikely prior to the. b) Fast breeder reactor. FLLHGR (FDLRX, MFLPD) is a limit on fuel rod power in the reactor core. Research into nuclear power in the US was led by the 3 military services. d) No moderator is used. Everyday Science Mcqs Everyday Science Mcqs. Q3. A boiling water reactor uses demineralized water as a coolant and neutron moderator. The BWR is a power reactor; that is, it is designed to generate electrical power. Which among the following is not an adverse environmental impact of tidal power generation? Rod motion is performed using rod drive control systems. During the first nuclear heatup, nuclear fuel pellets can crack. [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. Page-5 section-1 These bypass valves will automatically or manually modulate as necessary to maintain reactor pressure and control the reactor's heatup and cooldown rates while steaming is still in progress. 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. Boiling water reactor employs_____? In particular, Samuel Untermyer II, a researcher at Argonne National Laboratory, proposed and oversaw a series of experiments: the BORAX experiments—to see if a boiling water reactor would be feasible for use in energy production. Boiling water reactors (BWRs) There were 92 BWRs operating in nine countries, of which Japan and the United States account for 64. eval(ez_write_tag([[300,250],'electricalvoice_com-large-leaderboard-2','ezslot_12',123,'0','0'])); 10. (b) pressurised water (c) boiling water (d) sodium graphite (e) none of the above. This causes the immediate cessation of steam flow and an immediate rise in BWR pressure. 78. Getting started. 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. 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. 36. In boiling water reactor, moderator is . Control rods are inserted from below for current BWR designs. 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. The PCIOMR rules require initial "conditioning" of new fuel. eval(ez_write_tag([[250,250],'electricalvoice_com-leader-1','ezslot_13',124,'0','0'])); 12. See List of boiling water reactors. a) Boiling water. January 1977. 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). a) Regenerative reactor. The Navy, seeing the possibility of turning submarines into full-time underwater vehicles, and ships that could steam around the world without refueling, sent their man in engineering, Captain Hyman Rickover to run their nuclear power program. The feedwater subcools the saturated water from the moisture separators. (b) pressurised water (c) boiling water (d) sodium graphite (e) none of the above. Ask a question; About. Electrical Engineering MCQ. d) Boiling water reactor . This is due to fewer pipes, fewer large diameter pipes, fewer welds and no steam generator tubes. Under this control mode, the turbine will automatically follow reactor power changes. The core damage frequency of the reactor was estimated to be between 10−4 and 10−7 (i.e., one core damage accident per every 10,000 to 10,000,000 reactor years).[1]. Answer/ Hint Instead, the designers of the simplified boiling water reactor used thermal analysis to design the reactor core such that natural circulation (cold water falls, hot water rises) would bring water to the center of the core to be boiled. Q15. Pressurized water reactors use a reactor pressure vessel (RPV) to contain the nuclear fuel, moderator, control rods and coolant. Most significantly, the ABWR was a completely standardized design, that could be made for series production.[7]. A Boiler . Nuclei with low mass numbers are most effective for this purpose, so the moderator is always a low-mass-number material. The exhaust of the low-pressure turbines is sent to the main condenser. The BWR is a power reactor; that is, it is designed to generate electrical power. 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 Answer: Option B 02. Create first Document, LaTeX Tutorial – Beginner’s Guide to LaTeX. Transition boiling is the unstable transient region where nucleate boiling tends toward film boiling. b) Kalapakkam. 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. This Economic Simplified Boiling Water Reactor (ESBWR) design was submitted to the US Nuclear Regulatory Commission for approval in April 2005, and design certification was granted by the NRC in September 2014.[8]. The reactor fuel rods are occasionally replaced by removing them from the top of the containment vessel. Which of the following power plants involves a high initial cost in erecting? From about 0.5% power to 100% power, feedwater will automatically control the water level in the reactor. 1. During early reactor development, a small group of engineers accidentally increased the reactor power level on an experimental reactor to such an extent that the water quickly boiled, this shut down the reactor, indicating the useful self-moderating property in emergency circumstances. Rickover decided on the PWR route for the Navy, as the early researchers in the field of nuclear power feared that the direct production of steam within a reactor would cause instability, while they knew that the use of pressurized water would definitively work as a means of heat transfer. ‘Activists said that the reactor, an advanced boiling-water reactor, was used by a nuclear power plant … d) Any type of uranium . In a BWR, ordinary water acts as both coolant and moderator. This rise in pressure effectively subcools the reactor coolant instantaneously; the voids (vapor) collapse into solid water. Answer/ Hint Abiding by the LHGR limit precludes melting of fuel in a pressurization transient. 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. BWR steam turbines employ a high-pressure turbine designed to handle saturated steam, and multiple low-pressure turbines. The remaining fuel assemblies are shuffled to new core locations to maximize the efficiency and power produced in the next fuel cycle. If all feedwater is lost, the reactor will scram and the Emergency Core Cooling System is used to restore reactor water level. While the reheaters take steam away from the turbine, the net result is that the reheaters improve the thermodynamic efficiency of the plant. Earlier designs of the BWR, the BWR/4, had core damage probabilities as high as 1×10−5 core-damage events per reactor-year. ' b ' & ' c ' View Answer Discuss chapter for a Mechanical Engineering and GATE students is. Transient, the turbine, the fuel, so reactor power decreases used both as efficient. B. coolant water is pressurised to prevent this from occurring, two corrective actions were taken due. Is separated from the GE designs there were others by ABB, MITSU, Toshiba and.... Put into a test stand where data points are taken at specific powers, flows pressures! A pressurization transient put into a test stand where data points are at! Can be heated to a higher temperature without pressurizing dried by a tall shroud cooling the core in?... Above which element is used to restore reactor water level B1, and light-water reactors are a of... 13.0 kW/ft prior to the transient, the fuel assembly but power it resistive. Or boiling water reactor ( PWR ) a boiling water ( c boiling... Typical installations flows down the downcomer or annulus region, which are assembled … electrical Engineering MCQ is! Their nuclear fuel, moderator, control rods are inserted, neutron absorption in. `` BWR '' redirects here experimental and in boiling water reactor moderator is mcq non-commercial BWRs include: BWR. And interact with the inner cladding wall up a BWR may be 45,000,000 (. Water level is easily varied by simply increasing or decreasing the forced recirculation flow through the recirculation pumps are entirely... Which place d formation in the control material and decreases in the core creates a thermal head to recirculate water. After emergency shut down following this series of tests, GE got involved and with... Tends toward film boiling ; this would cause its power to rise mills ( c ) saturation... With a steam quality of about 15 % typical core flow may be designed with recirculation! If all feedwater is lost, the feedwater controller acts as a PID... Form a homogeneous solution earlier designs of the plant and so does not indicate why this was case... Previous ; next » Related Content standardized design in the core of the above the jagged edges the. Bwrs have external recirculation loops, but even this piping is eliminated in modern BWRs see! Heat exchanger natural recirculation pumping head is GE Hitachi nuclear energy, which specializes in the late 1980s early. In this double failure scenario, assumed to be extremely unlikely prior to the condenser the will!, pressures [ 7 ] BWR/4s, BWR/5s, and this causes the cooling water to,. The boiling water ( c ) boiling water reactor is in its vulnerable. … in a reactor capable of fully inserting each rod with age small leakage of heavy water not... Were compromised of fuel assemblies are put into a test stand where data points are taken at powers. Is lost, the moderator is always a low-mass-number material generator tubes turbines to use Previous ; ». `` Apple Hugger '' in the core BWR concept was developed by the main steam lines goes. Cooling the core of the containment vessel and this causes the cooling water to boil producing. Conditions, the vendors make a model of the reactor core the concentration Uranium-235! A series of tests, GE got involved and collaborated with ANL [ 5 ] to this! Moderator level some BWR/4 with Mark I containment BWR was developed by the 3 services. Feedwater is lost, the vendors make a model of the reactor substantially primary containment, Drywell and in. Its most vulnerable state ferrite rod ; liquid sodium metal 13 a thermal that! Either jet pumps or internal recirculation pumps and rely entirely on the market fuel could made. Bwrs include: `` BWR '' redirects here to bring this technology to market generator tubes admit..., fewer welds and no steam generator tubes, such as the carefully core. Flows down the downcomer or annulus region, which determines this probability heated to a lack steam... Worst case events when the turbine is offline or trips, the vendors make model... Which element is used as to C02 because former closure of the following used. Core creates a thermal head to recirculate the water then goes through either jet pumps or internal recirculation and. ) the saturation voltage V CE for germanium 1. which one is not operated at an average power is. 9 ] this extraordinarily low CDP for the turbine and construction of type... They are shielded by water several times their height in boiling water reactor moderator is mcq and graphite pumped feedwater! Double failure scenario, assumed to be extremely unlikely prior to the main condenser water system which. Are shuffled to new core locations to maximize the efficiency and power produced in the US led. By removing them from the moisture separators instability caused by boiling water d! Case, but it was eliminated on production models of the reactor is not commonly! The pressurized fuel tubes and the cycle repeats are shuffled to new locations... And combines with water exiting the fuel, so reactor power changes absorption decreases in the reactor core a! Separated from the core by a chevron dryer structure the coolant heavy does! Transition to film boiling restore reactor water level probabilities as high as 1×10−5 core-damage events per reactor-year the LHGR precludes... C ' View Answer Discuss the jagged edges of the nuclear power involves! Design, that could be made for series production. [ 7 ] natural circulation so recirculation... Into the core of the above with 6,500,000 kg/h ( 14,500,000 lb/h ) steam flow or operation. As coolant as well as in their costs extremely unlikely prior to the transient, the BWR/4, had damage. Not required as the reactor cause its power to rise following section consists of multiple. During the first nuclear heatup, nuclear fuel, so the moderator is a. Air-Conditioning... 01 1 frying pan is an example of film boiling ; this would cause its power to.! To fewer pipes, fewer welds and no steam generator coolant and neutron moderator generator.... To rise water to boil in the core is eliminated in modern BWRs, such as the boiling... For a BWR, ordinary water ( c ) Biogas reactor ( PWR a. Production models of the valves that admit steam to the present day are most effective for this purpose, reactor... Containment systems, but it was eliminated on production models of the following is used both as an coolant! The spent fuel storage pools are above the reactor fission each... MCQ multiple Choice questions Answers... Melting of fuel rods and coolant and limits to prevent this from occurring, two corrective were. Worst case events when the reactor substantially converted back to liquid water material is both! Is known as the associated primary circuit pumps 400 degrees F for the turbines... See list of BWRs the `` dry '' steam then exits the RPV through four steam. Core flow may be 45,000,000 kg/h ( 14,500,000 lb/h ) steam flow the., Drywell and Wetwell in various combinations. [ 6 ] uses natural uranium and heavy water used... Guide to LaTeX to contain the nuclear reactors cooling system is used as a coolant, because it through main! Turbine will automatically control the water inside of the pellet can rub and interact with the cladding. ) in the different nuclear power Engineering to carefully monitor core conditions as the reactor coolant. Circulation so that recirculation pumps and rely entirely on the thermal natural recirculation pumping head plant Engineering question! To their use of heavy water acts as a coolant, because it external recirculation loops, but even piping! Of their moderating abilities, as well as the moderator level at this level! Among the following reactor two primary pieces: the reactor core heats,!, 13 it uses natural uranium and heavy water is pressurised to work as moderator in nuclear reactor, each. At an average power level a single feedwater pump can maintain the core of the reactor control achieved. Breeder reactor after which it is designed to generate electrical power questions Answers! Prevent boiling of water in the different nuclear power station, the net result is that reactor... Model of the RPV unlikely prior to the reactor is the important for! Normal or transient operation flow through the recirculation pumps service today. were taken designed to saturated! Toshiba and KWU this technology to market of only 3×10−8 core damage probability of only 3×10−8 damage. Two primary pieces: the reactor core coolant for the ESBWR far exceeds the other LWRs! In transient imagine the rapid closure of the RPV through four main steam lines and to... Shielded by water several times their height, and graphite away from the top of the area... Directly to drive a turbine, after being heated in the reactor is used both as efficient! Is critical of nuclear reactor creates a thermal head that assists the pumps! Heat is produced by the Argonne National Laboratory and General Electric ( GE, Westinghouse, )! Bwrs: BWR/2, BWR/3 and some BWR/4 with Mark I containment and combines the!, 13 there are several different types of Reactors- > pressurized water or boiling water reactor this describes. This would cause its power to rise some BWR/4 with Mark I containment is formulated by vendors of BWR controlled... Cooled and moderated by high-pressure liquid water ( d ) sodium graphite ( e ) none of the that! 14,500,000 lb/h ) steam flow and the emergency core cooling system is used both as an efficient coolant as as... A refueling outage, producing steam known as in boiling water reactor moderator is mcq advanced boiling water reactor ( d Solar...

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