Accumulator Research Articles

Modeling and analysis of selected organization for economic cooperation and development PKL-3 station blackout experiments using TRACE

Abstract A series of tests dedicated to station blackout (SBO) accident scenarios have been recently performed at the Primarkreislauf-Versuchsanlage (primary coolant loop test facility; PKL) facility in the framework of the OECD/NEA PKL-3 project. These investigations address current safety issues related to beyond design basis accident transients with significant core heat up. This work presents a detailed analysis using the best estimate thermal–hydraulic code TRACE (v5.0 Patch4) of different SBO scenarios conducted at the PKL facility; failures of high- and low-pressure safety injection systems together with steam generator (SG) feedwater supply are considered, thus calling for adequate accident management actions and timely implementation of alternative emergency cooling procedures to prevent core meltdown. The presented analysis evaluates the capability of the applied TRACE model of the PKL facility to correctly capture the sequences of events in the different SBO scenarios, namely the SBO tests H2.1, H2.2 run 1 and H2.2 run 2, including symmetric or asymmetric secondary side depressurization, primary side depressurization, accumulator (ACC) injection in the cold legs and secondary side feeding with mobile pump and/or primary side emergency core coolant injection from the fuel pool cooling pump. This study is focused specifically on the prediction of the core exit temperature, which drives the execution of the most relevant accident management actions. This work presents, in particular, the key improvements made to the TRACE model that helped to improve the code predictions, including the modeling of dynamical heat losses, the nodalization of SGs' heat exchanger tubes and the ACCs. Another relevant aspect of this work is to evaluate how well the model simulations of the three different scenarios qualitatively and quantitatively capture the trends and results exhibited by the actual experiments. For instance, how the number of SGs considered for secondary side depressurization affects the heat transfer from primary side; how the discharge capacity of the pressurizer relief valve affects the dynamics of the transient; how ACC initial pressure and nitrogen release affect the grace time between ACC injection and subsequent core heat up; and how well the alternative feeding modes of the secondary and/or primary side with mobile injection pumps affect core quenching and ensure stable long-term core cooling under controlled boiling conditions.

An improved simplified method of evaluating severe accident source term in the containment of AP1000

This paper focuses on the source term estimation in AP1000 Nuclear Power Plant (NPP) under severe accident condition. Methods that utilize MELCOR code can evaluate the source term, but the evaluation process is time-consuming. Also, the reference values in NUREG-1465 can be directly used as the severe accident source term; however, it was initially proposed for second–generation reactors and it has difficulty in simulating changes in release fraction along with accident process. In this paper, the Improved Simplified Source Term (ISST) code was developed based on the IAEA’s Simplified Source Term model (SST) presented in IAEA-TECDOC-1127. In addition, the models for core uncovery stage and adiabatic heating-up stage were optimized in this work; taking into account the Accumulator (ACC) and the Core Makeup Tank (CMT) of the emergency core cooling system. Moreover, four fission products release evaluation models were integrated into ISST, making it applicable for the source term evaluation of AP1000 reactor under severe accident initiated by LBLOCA condition. To verify the developed ISST code, the IAEA’s SST, MELCOR and the reference source term in NUREG-1465 were differently used to evaluate the source term released into the containment in a LBLOCA of the AP1000 nuclear power plant. The results obtained from the models in the ISST code were analyzed and compared with each other, and with those obtained from NUREG-1465, IAEA’s SST and MELCOR. Compared with results calculated with the IAEA’s SST, the results calculated with ISST are closer to those calculated using MELCOR. ISST is computationally faster than MELCOR, hence it gives the source term calculation results quicker. Compared with results calculated with MELCOR, the results calculated with ISST are more conservative for Cs and I while the result derived from NUREG-1465 for noble gases is more conservative.

Factory testings of silver obtaining from silver-lead-zinc accumulators by two-stage smelting

Factory testings of silver obtaining from silver-lead-zinc accumulators by two-stage smelting

Passenger accumulator fed railcars in regional railway traffic

This paper is focused on contemporary posibilities of replacement diesel-powered railcars by accumulator powered railcars in regional railway traffic. In...

Thermal Operating Machine

A thermal machine with reverse cycle and steam compression and its operating method are described; the machine comprises: a condenser (2) downstream of and in fluid communication with a main compressor (6); a main lamination valve (9) downstream of the condenser (2); an evaporator (10) downstream of and in fluid communication with the lamination valve (9); an electric generator (13); an electric charge accumulator (15, 17); an automatic time-changing switch (14) configured depending on hourly production and consumption slots of an electric market, connected downstream of the electric generator (13) and before the accumulator (15, 17); at least one expander (7) connected to at least one alternator (8) in fluid communication between the evaporator (10) and the main compressor (6); and at least one heat exchanger (5) having a hot branch connected downstream to the condenser (2) and before the lamination valve (9) and a cold branch connected downstream to a second lamination valve (4) and upstream to the expander (7).

ROSA/LSTF Tests and RELAP5 Posttest Analyses for PWR Safety System Using Steam Generator Secondary-Side Depressurization against Effects of Release of Nitrogen Gas Dissolved in Accumulator Water

Two tests related to a new safety system for a pressurized water reactor were performed with the ROSA/LSTF (rig of safety assessment/large scale test facility). The tests simulated cold leg small-break loss-of-coolant accidents with 2-inch diameter break using an early steam generator (SG) secondary-side depressurization with or without release of nitrogen gas dissolved in accumulator (ACC) water. The SG depressurization was initiated by fully opening the depressurization valves in both SGs immediately after a safety injection signal. The pressure difference between the primary and SG secondary sides after the actuation of ACC system was larger in the test with the dissolved gas release than that in the test without the dissolved gas release. No core uncovery and heatup took place because of the ACC coolant injection and two-phase natural circulation. Long-term core cooling was ensured by the actuation of low-pressure injection system. The RELAP5 code predicted most of the overall trends of the major thermal-hydraulic responses after adjusting a break discharge coefficient for two-phase discharge flow under the assumption of releasing all the dissolved gas at the vessel upper plenum.

Simulation of the small modular reactor severe accident scenario response to SBO using MELCOR code

Advanced small modular reactors (SMRs) use different design in the systems, structures, components from large reactors for achieving a high level of safety and reliability. In present work, the SMRs severe accident caused by the station blackout (SBO) was modeled and analyzed using MELCOR code, and the simulation of the accident scenario response to SBO was conducted. Based on the steady state calculation, which agrees well with designed values, we introduced the SBO accident for transient calculation. First, the case of the SBO accident without the passive core cooling system (PXS) was calculated. The progression and scenario in the reactor pressure vessel (RPV) and the containment were simulated and analyzed, including the transient response, cooling capacity and thermal-hydraulic characteristics and so on. The station black-out transient in the SMR can be simulated accurately, and the main failure model in the accident process can be concluded. Then three other cases of the SBO accident with different passive safety systems (core makeup tank (CMT), accumulator (ACC), passive residual heat removal system heat exchanger (PRHR HX), automatic depressurization system (ADS)) of the PXS were calculated respectively, and the results for different passive safety systems were compared. The passive core cooling system can not only provide water to the primary coolant system, but also take away the reactor decay residual heat. So in a station black-out transient, we can get more time for restoring AC power, and effectively prevent the accidents such as Fukushima.

On board accumulator model for power flow studies in DC traction networks

This paper presents a detailed model of a DC train to be applied to an unified AC/DC power flow analysis. The model will consider the regenerative braking of the train and the squeezing control that derives part or all regenerated power to the rheostatic braking system depending on the catenary voltage. The model also considers an on board accumulator (ACR) that can be charged with the regenerated power, depending on the network and train parameters. When the train is in traction mode, both the network and the ACR can contribute in feeding the train traction system.

CES 발전소의 최적운용 알고리즘 개발

Recently due to the increasing of the importance on the green energy is getting higher by implementing EERS(Energy Efficiency Resource Standards) and NA(Negotiated Agreement) such as lacks of natural resources and The United Nations Framework Convention on Climate Change. And the most practical solution is CHP(Combined Heat and Power) which performs the best energy efficiency.<BR> This paper developed optimal operation mechanism of CES(Community Energy System) for enhancement of energy efficiency using CHP(Combined Heat and Power), PLB(Peak Load Boiler) and ACC(ACCumulator) capacities. This method optimally operated these capacities calculated the maximum profits by Dynamic Programing. Through the case studies, it is verified that the proposed algorithm of can evaluate availability.

Very Simple BICM-ID Using Repetition Code and Extended Mapping with Doped Accumulator

This paper proposes very simple bit-interleaved coded modulation with iterative detection (BICM-ID) as a spectrally efficient signal transmission scheme, where irregular repetition code and extended mapping with rate-1 doped accumulator (ACC) are combined to achieve a clear turbo-cliff. Doped ACC is used for close matching of the demapper and decoder’s extrinsic information transfer curves. Although the proposed BICM-ID system is very simple, it can achieve excellent performances and completely eliminate bit-error-rate floor. An exemplifying result for extended non-Gray mapped 4-quadrature amplitude modulation symbol shows that with 0.916 bits/channel use, turbo-cliff happens at 1.27 dB away from the Shannon limit.

Positron injector for LEPTA

The injector of the low energy positrons for accumulator LEPTA is being assembled at JINR. The key elements of the injector have been tested. The cryogenic source of slow positrons has been tested with a test isotope 22 Na of the initial activity of 0.8 MBk. The continuous slow positron beam intensity of 5.8 · 10 3 s −1 with average energy of 1.2 eV and width of a spectrum 1 eV has been obtained. The achieved moderator efciency is about 1%. The accumulation process in the positron trap was investigated with electronux. Th e lifetime of the electrons in the trap, τlife 80 sa nd capture efciency e ∼ 0.4 have been obtained. The maximum number of the accumulated particle was Nexp =2 · 10 8 at the initialux of 5 · 10 6 e − /s. ‚ �ˆŸˆ § ¢¥·I ¥E¸O ¸iμ·± ¨³¶E²O¸´μ£μ ¨´|¥± Eμ· ¶μ§¨E·μ´μ¢ ´¨§±μ° O´¥·£¨¨ ¤²O E¸E - ´μ¢±¨ LEPTA. �·μ¢¥¤¥´μ O±¸¶¥·¨³¥´E ²O´μ¥ ¨ ¸¸²¥¤μ¢ ´¨¥ · iμEO μ¸´μ¢´OI E§²μ¢ ¨´|¥±Eμ· . ˆ¸¸²¥¤μ¢ ´ · iμE ±·¨μ£¥´´μ£μ ¨¸EμI´¨± ¶μ§¨E·μ´μ¢ ¸ E¥¸Eμ¢O³ ¨§μEμ¶μ³ 22 Na, ±E¨¢´μ¸EOO 0,8 Œ±. �μ²EI¥´ ¶EIμ± ³¥¤²¥´´OI ¶μ§¨E·μ´μ¢ ¨´E¥´¸¨¢´μ¸EOO 5,8 · 10 3 c −1 ¸μ ¸·¥¤´¥° O´¥·£¨¥° 1,2 O‚ ¶·¨ I¨·¨´¥ ¸¶¥±E· 1 O‚. "μ²O § ³¥¤²¥´´OI ¶μ§¨E·μ´μ¢ ¸μ¸E ¢¨² 1% μE ¶μ²´μ£μ ¶μ- Eμ± . �·μ¢¥¤¥´μ ¨¸¸²¥¤μ¢ ´¨¥ ¶·μI¥¸¸ ´ ±μ¶²¥´¨O I ¸E¨I ¢ ²μ¢EI±¥ ´ O²¥±E·μ´ I. ‚ ·¥§E²OE E¥ μ¶E¨³¨§ I¨¨ ¶ · ³¥E·μ¢ ²μ¢EI±¨ ¤μ¸E¨£´EEμ ¢·¥³O |¨§´¨ ´ ±μ¶²¥´´OI O²¥±E·μ´μ¢ τlife 80 ¸, OEE¥±E¨¢´μ¸EO § I¢ E e ∼ 0,4, IEμ ¸μμE¢¥E¸E¢E¥E ´ ¨²EII¨³ ·¥§E²OE E ³, ¶μ²EI¥´´O³ ¢ ²μ- ¢EI± I ¶μ¤μi´μ£μ E¨¶ . �·¨ OEμ³ ³ ±¸¨³ ²O´μ¥ I¨¸²μ ´ ±μ¶²¥´´OI I ¸E¨I Nexp =2 · 10 8 ¶·¨ ¶¥·¢μ´ I ²O´μ³ ¶μEμ±¥ 5 · 10 6 e − /¸.

Experimental Study on the Performance of the Passive Safety Injection in an IIST

A passive core cooling system (PCCS) has been installed at the Institute of Nuclear Energy Research Integral System Test facility. It includes three core makeup tanks (CMTs), three accumulators (ACCs), a four-stage automatic depressurization system (ADS), a passive residual heat removal (PRHR) heat exchanger submerged into an in-containment refueling water storage tank (IRWST). The purpose of this research is to study the performance of the PCCS with passive injection during either a pressure balance line (PBL) break or a direct vessel injection (DVI) line break. Five experiments were performed simulating break area ratios of 0.5 to 2.0% (1.88 to 3.77 mm) at either a PBL or a DVI line. The general system response and the interactions of CMT, ACC, PRHR, and IRWST to the effect of core heat removal are observed and discussed. The experimental results show long-term core cooling can be reached for the cases of the PBL break and the DVI-line break following the PCCS actuation procedures.

Collectors, Accumulators, Hoarders, and Hoarding Perspectives

Collectors, Accumulators, Hoarders, and Hoarding Perspectives

RELAP5/MOD3 Code Analyses of LSTF Experiments on Intentional Primary-Side Depressurization Following SBLOCAs with Totally Failed HPI

The effectiveness of intentional depressurization of a pressurized water reactor primary system as a means to maintain core cooling during a small-break loss-of-coolant accident (SBLOCA) was studied. The investigation was based on experiments conducted at the Rig of Safety Assessment-V (ROSA-V) Large Scale Test Facility (LSTF) and RELAP5/MOD3 code calculations performed for LSTF geometry, together with single lumped-volume model calculations - all simulating hypothetical total failure of the high-pressure-injection system. For cold-leg breaks ≶2.5% of the leg cross-sectional area, experimental and analytical results have shown that the break discharge depressurizes the primary system to the accumulator (ACC) and low-pressure-injection (LPI) system injection pressures, and thus the core cladding temperature would be maintained below ~1000 K. For break areas ≤1.0%, on the other hand, additional depressurization means are needed to initiate the ACC injection before the core is overheated. RELAP5/MOD3 calculations have shown that steam venting through the pressurizer power-operated relief valves would be effective in depressurizing the primary system to the ACC and LPI pressures. However, for break areas <0.5%, the peak cladding temperature would finally reach the safety criterion of 1473 K.

Nitrogen in a steam generator of a PWR under SBLOCA conditions: Experimental investigations in the PKL test facility and comparison with analytical studies

Since 1976, extensive investigations of the thermal hydraulic behavior of a pressurized water reactor (PWR) during various accident scenarios have been carried out by Siemens/KWU at the integral test facility PKL, which simulates a typical four-loop 1300 MWe PWR of KWU design. One major topic of the current investigations includes tests under small break loss of coolant accident (SBLOCA) conditions, postulating additional system failures. During plant cool down in the course of SBLOCAs, besides other measures, the subsystems of the emergency core cooling system are initiated. Below a primary pressure of 26 bar, the accumulators (ACCs) automatically inject water into the primary system. With the postulation of additional system failures in the presented PKL experiment, nitrogen (N 2) can enter the primary system at a primary pressure > 10 bar before the ACCs are shut off. Under these very hypothetical SBLOCA conditions, nitrogen can accumulate in the steam generator U-tubes, whereby the heat removal mechanism changes from natural circulation to reflux-condenser mode. This phenomenon is analyzed in detail; interesting two-phase flow patterns were observed with heat removal under water-steam countercurrent flow with nitrogen present. This PKL experiment shows that a sudden stagnation of natural circulation in all loops caused by nitrogen at considerably reduced inventory does not impede heat removal from the core; it results in the very effective reflux-condenser mode. The system stabilizes itself at a specific pressure and temperature level, and consequently the removal of the core power is ensured for a given period, until further measures are initiated.

工場廃熱利用昼間発電型CO&lt;sub&gt;2&lt;/sub&gt;回収発電システムの構成とその基本的特性

A CO2-capturing power generation system utilizing waste heat was proposed for increasing electric power generated in the daytime. In the system, relatively low temperature saturated steam is produced by using industrial waste heat at nighttime and is stored in a steam accumulator (AC). At daytime the steam from the AC is used as the working fluid of a gas turbine power generator in which generated CO2 is captured based on the method of oxygen combustion. The system has no process of compressing the working fluid gas, that is the process to be extremly power consuming one. Hence the system has high power generation efficiency. The generated CO2 can be captured by using oxygen combustion method, so that high CO2 capturing ratio near 100% as well as no thermal NOX emission characteristics can be attained. It has been shown through a case study of using waste heat generated in a urban waste incineration plant that the proposed system has total net exergetic efficiency of 31.1% and that the power generation efficiency is 51.1%, when the amount of utilized waste heat is neglected, being higher than 17.5% compared with that of the conventional power plant with the efficiency of 43.5%.

Intentional Depressurization of Steam Generator Secondary Side during a PWR Small-Break Loss-of-Coolant Accident

The consequence of intentional depressurization of the steam generator (SG) secondary side during a small break loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR) was studied using the ROSA-IV Large Scale Test Facility (LSTF). The LSTF is a 1:48 volumetrically scaled full-height model of a Westinghouse-type PWR. The experiment simulated a 0.5% cold leg small-break LOCA with total failure of high pressure injection (HPI) system. The SG secondary-side atmospheric relief valve (ARV) was latched open after the core top region was uncovered. Then, the primary pressure closely followed the secondary pressure and dropped to the accumulator (ACC) injection pressure of 4.51MPa before the core became severely overheated. A post test analysis, which was performed using the RELAP51 MOD2 code with modifications made by the authors, predicted well the primary and secondary side responses during this experiment.

A Neural Network for Feedforward Controlled Smart Structures

A neural network and adaptive algorithm suitable for driving non-linear feedforward control systems used with "smart" structures to actively control sound and vibration is presented. The neural network/algorithm combination can be viewed as an extension to the commonly used transversal filter/filtered-x LMS algorithm combination, in that the neural network is essentially a transversal filter with a non-linear hidden layer placed between the input delay chain and output ac cumulator. The algorithm accommodates the transfer function and time delay between the control signal output and error signal input. The arrangement is shown in simulation to be capable of sup pressing a primary distrubance, which is a non-linear function of the reference signal fed to the con trol filter, and of suppressing harmonics introduced into a system by a control actuator exhibiting non-linear performance characteristics. The results are compared to those similarly obtained using a linear adaptive control arrangement, which is incapable of providing attenuation in either case.

PWR Cold-Leg Small-Break LOCA with Total HPI Failure

Cold-leg small-break loss-of-coolant accident (LOCA) tests were performed at the ROSA-IV Large Scale Test Facility (LSTF), a 1/48 volumetrically-scaled model of a pressurized water reactor (PWR). The tests were conducted for break areas ranging 0.5–10% of the scaled cold leg area, and simulated hypothetical total failure of the high pressure injection (HPI) system. One of the tests, conducted with 1% break area, included an intentional depressurization of the primary system that was initiated after the onset of core dryout. A simple prediction model is proposed for prediction of times of major events, namely, loop seal clearing, core dryout, accumulator (ACC) injection and actuation of low pressure injection (LPI) system. Test data and model calculations show that intentional primary system depressurization with use of the pressurizer power-operated relief valves (PORVs) is effective for break areas of approximately 0.5% or less, is unnecessary for breaks of approximately 5% or more, and might be insuffic...

PWR Cold-Leg Small-Break LOCA with Total HPI Failure. Effect of Break Area on Core Dryout and Intentional Depressurization for Prevention of Excess Core Dryout.

Cold-leg small-break loss-of-coolant accident (LOCA) tests were performed at the ROSA-IV Large Scale Test Facility (LSTF), a 1/48 volumetrically-scaled model of a pressurized water reactor (PWR). The tests were conducted for break areas ranging 0.5–10% of the scaled cold leg area, and simulated hypothetical total failure of the high pressure injection (HPI) system. One of the tests, conducted with 1% break area, included an intentional depressurization of the primary system that was initiated after the onset of core dryout. A simple prediction model is proposed for prediction of times of major events, namely, loop seal clearing, core dryout, accumulator (ACC) injection and actuation of low pressure injection (LPI) system. Test data and model calculations show that intentional primary system depressurization with use of the pressurizer power-operated relief valves (PORVs) is effective for break areas of approximately 0.5% or less, is unnecessary for breaks of approximately 5% or more, and might be insuffic...