Swimming Pool Reactor Research Articles

Seismic performance of base-isolated structures for swimming pool reactors under different foundation conditions.

The swimming pool reactor (SPR) is an innovative and environmentally friendly heating source. An SPR building was selected as the research subject, and a 3D dynamic interaction model incorporating the liquid sloshing effect was created using ANSYS software and the secondary development characteristics of user-programmable features (UPFs). Energy dissipation from scattered waves was accounted for using viscous-spring boundary elements, while the dynamic hydraulic effect was modeled via the Housner equivalent mechanical model. Considering soil-structure interaction (SSI) effects, this study examines the impact of isolation measures on the structure's seismic mitigation performance. It investigates how varying foundation conditions affect the seismic resistance of the isolated structure. Results indicate that seismic isolation ratios for acceleration, floor response spectra, displacement, and base shear diminish as site stiffness decreases. However, regarding sloshing wave height, seismic isolation amplified the height under all conditions but remained within safe limits. These findings offer valuable insights for seismic design across different SPRs.

Teaching in a Swimming Pool

In the 1950s, American public universities began training a vast new cadre of nuclear engineers, technicians, and scientists in specially designed and built “teaching reactors.” As this article describes, a generation of nuclear engineering undergraduates and graduate students were exposed to an open, accessible, and above all, visible demonstration of nuclear energy through educational “swimming pool”–style reactors. Distinct from reactors for either weapons or power production, the swimming pool reactor was specifically configured to be a pedagogical tool. Educational programs were created around federally and industrially sponsored reactors for training, part of the massive Cold War era transformations of Midwestern, Western, and Southern public colleges and universities. This article offers the Ford Nuclear Reactor at the University of Michigan as an example of how the peaceful pedagogical atom developed after the 1950s. As I argue, teaching reactors were one product of the conservative compact made between government, public universities, and private industry in the early 1950s that underpinned the famed Atoms for Peace movement, with its technology and information sharing and international training priorities. Indeed, teaching reactors resolved for Eisenhower’s administration the tension between a desire for centralized control of the atom and the powerful vision of a future of prosperity brought about by open education and use of nuclear materials. This paper is part of a special issue entitled “Revealing the Michigan Memorial–Phoenix Project.”

Control rod drop-time reduction in typical swimming pool research reactors

Control rods play an important role in the safety of nuclear reactors, due to the fact that in the emergency situations, they are to be inserted into the reactor core and scram the reactor secure and fast. As far as safety concerns, drop-time of control rods should be minimized as much as possible. In this paper as a case study, TRR (Tehran Research Reactor) data is chosen as a typical swimming pool reactor and drop-time of control safety rod is to be minimized. Present fork type control rods are more prone to entanglement than former tube type. Methods to ease this problem are considered. Several approaches are studied and proposed in this work aimed to decrease the drop-time of control rods especially in case of emergency. Changing control rod shape into a more aerodynamic form, helps to reduce drag force and thus decreasing drop-time in an aqueous medium. Further improvement is achieved by provision of several holes in the head section. As fluid dynamic computations suggest, drop-time may reduce as much as 6% due to geometry modification. Focusing on electronic part, improved design on magnet (Coil and its core together) could reduce the lag time between scram signal issuance till control rod release. Using magnet with modified air gaps showed that existing drop-time from about 800 ms, could be reduced by as much as 34%. Moreover, by using amorphous core instead of existing one, drop-time is expected to reduce from 800 ms by as much as 30%.Measurements showed that existing electromechanical circuitry of relays, has an inherent 3 ms delay which is not so much compared to 800 ms total scram time. Therefore, working on this part is not a big deal with respect to other modifications and therefore is disregarded.

Design and computational analysis of passive siphon breaker for 49-2 swimming pool reactor

Design and computational analysis of passive siphon breaker for 49-2 swimming pool reactor

Utilization of high-density fuel and beryllium elements for the neutron flux enhancement in typical MTR type research reactors

Pakistan Research Reactor-1 (PARR-1) is a typical MTR type swimming pool reactor utilizing low enriched uranium (LEU), i.e. 19.99% enriched in 235U, silicide dispersion fuel of density 3.28 gU/cm 3. This simulation study was conducted by employing the standard reactor physics simulation codes WIMS-D/4, CITATION, and a burnup analysis code FCAP along with a reactor thermal hydraulic simulation code PARET. The present study shows that by directly substituting LEU silicide dispersion fuel of density 4.8 gU/cm 3 in place of fuel currently in use in PARR-1 and by loading beryllium elements at the unused 9 × 6 position of PARR-1 grid plate, a smaller equilibrium core can be designed that can provide 82% higher neutron fluxes at the central flux trap position at 14% lower cost than the existing core. Fuel cycle length of this core is also two days larger than the existing core and this core can be operated safely at the existing power of 10 MW with the existing coolant flow rate of 1000 m 3/h. A possible use of LEU U–Mo monolithic fuel of density 15.3 gU/cm 3 with some adjustment in fuel to moderator ratio and use of Be reflector would provide 89% higher neutron flux in PARR-1 at 29% lower cost. Fuel cycle length of this core will be five days shorter than the existing core and it will require 48% more coolant flow rate for its safe operation at 10 MW.

A 16N/19O Monitor for Leak Detection in a Steam Generator

This paper describes a new system for monitoring leaks in a steam generator. The new system extends the traditional 16N monitor to detect both the rate and the location of a leak. Because the transit time is different for radioactive 16N and 19O to travel from the reactor core via the hot bottom side, cold bottom side, or bend region of the U-tube in a steam generator to the gamma-ray detector, the new system uses the different transit times to identify the location of leaks. Specifically, the ratio S0 of 16N to 19O activities in the reactor core of a swimming pool reactor was calculated by combining the cross sections σnp(E) and σnγ(E) with the neutron spectra ϕn(E). The ratio S1 of 16N to 19O activities in the measurement room was also calculated and measured by the high-purity germanium and NaI(Tl) detectors. The result of the calculation agrees with the measurement within an acceptable range.

Conductive heating and melt circulation in pyrometallurgy

Melt circulation and conductive heating are introduced in relation to the then new imperial smelting furnace (ISF) for the production of zinc in a blast furnace. The focus then changes to projected development of a recently proposed continuous steelmaking process, in which pools of molten iron/steel are created inside residual solid ferrous material to form a cascade of interconnected melt circulation loops. These pools are maintained at the liquidus temperature by melt circulation with the thermal requirements being provided by conductive heating, during start-up, stand-by or planned shut-downs. During operation, the various 'swimming pool reactors' process well-mixed iron bearing materials (virgin ore or secondary material) with granular/pulverised coal and flux, deposited as charge on the moving surface of the iron-making loop. A solid raft of metallised material is first formed and then projected by drag forces onto the surface of the first of the steelmaking loops, in which melting and slag/metal separation occurs along with partial decarburisation and desulphurisation. The continuous overflow by a hot metal siphon is treated in at least one further melt circulation loop to produce refined steel ready for continuous casting. Key features of hot metal siphons, emphasising the requirements for conductive heating, are discussed in detail.

The international atom: evolution of radiation control programs.

Under the Atoms for Peace program, Turkey received a one MWt swimming pool reactor in 1962 that initiated a health physics program for the reactor and a Radiation Control Program (RCP) for the country's use of ionizing radiation. Today, over 13,000 radiation workers, concentrated in the medical field, provide improved medical care with 6,200 x-ray units, including 494 CAT scanners, 222 radioimmunoassay (RIA) labs and 42 radiotherapy centers. Industry has a large stake in the safe use of ionizing radiation with over 1,200 x-ray and gamma radiography and fluoroscopic units, 2,500 gauges in automated process control and five irradiators. A 48-person RCP staff oversees this expanded radiation use. One incident involving a spent 3.3 TBq (88 Ci) 60Co source resulted in 10 overexposures but no fatalities. Taiwan received a 1.6 MWt swimming pool reactor in 1961 and rapidly applied nuclear technology to the medical and industrial fields. Today, there are approximately 24,000 licensed radiation workers in nuclear power field, industry, medicine and academia. Four BWRs and two PWRs supply about 25% of the island's electrical power needs. One traumatic event galvanized the RCP when an undetermined amount of 60Co was accidentally incorporated into reinforcing bars, which in turn were incorporated into residential and commercial buildings. Public exposures were estimated to range up to 15 mSv (1.3 rem) per annum. There were no reported ill effects, except possibly psychological, to date. The RCP now has instituted stringent control measures to ensure radiation-free dwellings and work places. Albania's RCP is described as it evolved since 1972. Regulations were promulgated which followed the IAEA Basic Safety Standards of that era. With 525 licenses and 600 radiation workers, the problem was not in the regulations per se but in their enforcement. The IAEA helped to upgrade the RCP as the economy evolved from one that was centrally planned economy to a free market economy. As this transition takes place, public radiation exposures in the medical field will continue to be high until the old x-ray equipment is phased out. A small conscientious health physics staff works with limited resources to keep radiation exposures at acceptable levels. These three country RCPs, as they have evolved, have some commonality. Today, all radiation installations are licensed, both for radioactive material and x-ray equipment. Radiation workers are individually licensed or registered. All RCPs have, or are striving to have, their radiation regulations conform to ICRP 60 recommendations as spelled out in the Basic Safety Standard (1996). Finally, all three countries have as yet to find a permanent solution for their radioactive waste.

Automated fault tree synthesis by semantic network modeling, rulebased development and recursive 3-value procedure

A concept of flow is introduced to represent any material, information, energy, activity, or phenomenon which can move or propagate along flow paths to cause events specific to the system to be analyzed. A graphical equipment library is given to represent typical types of ‘generation rate’ and ‘aperture’ controllers. The system is modeled by a semantic network with labeled arrows showing effect to cause (backward) relationships between flow and equipment nodes. A correspondence between the equipment library and the system components is established, and the semantic network is constructed by integrating network fragments in the library. Fixed and/or free boundary conditions can be specified explicitly for flow or equipment nodes. Forward-chaining event development rules locally trace the labeled arrows, while a 3-value procedure guides the FT generation by recursive rule applications. The rules are obtained from tables and equipment definitions. The 3-value logic is used to truncate FTs according to the boundary conditions. Different FTs are generated for different top events and boundary conditions, given a semantic network model. FT modules and their hierarchies can be identified by examining network theoretic properties of flow nodes. The proposed approach is demonstrated for a relay system, a hypothetical swimming pool reactor and a chemical reactor.

Composite space charge density functions for the calculation of gamma sensitivity of self-powered neutron detectors, using Warren's model

In the calculational model developed by Warren and Shah for the computation of the gamma sensitivity ( S γ ) it has been observed that the computed S γ value is quite sensitive to the space charge distribution function assumed for the insulator region and the energy of the gamma photons. The S γ of SPNDs with Pt, Co and V emitters (manufactured by Thermocoax, France) has been measured at 60Co photon energy and a good correlation between the measured and computed values has been obtained using a composite space charge density function (CSCD), the details of which are presented in this paper. The arguments are extended for evaluating the S γ values of several SPNDs for which Warren and Shah reported the measured values for a prompt fission gamma spectrum obtained in a swimming pool reactor. These results are also discussed.

Measurement of Thermal Neutron Cross Section and Resonance Integral of the Reaction137Cs(n, γ)138Cs

Abstract To obtain fundamental data for the research of the transmutation of nuclear waste, the thermal neutron cross section and the resonance integral of the reaction 137Cs(n, γ)138Cs have been measured by means of a modified Cd-ratio technique. Targets of about 0.4 MBq 137Cs were irradiated with neutrons in the JRR-4 swimming pool reactor by using a pneumatic tube equipped with a movable Cd shield, and neutron fluxes and their epithermal neutron fractions were monitored with activation detectors (Co/Al and Au/Al) whose sensitivity to epithermal neutrons differed from each other. After irradiation, the 137Cs samples were purified chemically and their γ-ray spectra were measured with a high purity Ge detector. The resulting yields of 138Cs for different neutron spectra and the neutron flux data have yielded that the thermal neutron cross section (for 2,200 m/s neutrons) is 0.25±0.02b and the resonance integral 0.36±0.07b. The results are consistent with the effective cross section (σ=0.250±0.013b) of our...

Development of a digital reactor control and protection system

Abstract For automation of routine monitoring and control duties and for retrofitting the aging control and protection system of the 33-year-old swimming-pool reactor SAPHIR at PSI, a digital data aquisition and control system, based on microprocessors with intelligent and remote multiplexing capabilities and strictly cyclic and deterministic signal processing is being developed. The implementation of this functionally and geographically distributed system leads to an improved man/machine interface and is welcomed by the Swiss regulatory authorities as a contribution to the nuclear qualification of digital reactor protection systems for future reactor facilities like district heating reactors or gas-cooled high temperature reactors. The demonstration and testing on an already operating research reactor with a proven, conventional protection system as a backup has the benefit of not being subject to the time critical licensing procedures for new reactors.

Determination of As, Cd, Hg, Cu and Zn in biological samples by radiochemical neutron activation analysis

In this work, a simple group separation scheme based on extraction for NAA determination of trace of As, Cd, Hg, Cu and Zn in biological materials is described. For this purpose, zinc-diethyldithiocarbamate, Zn(DDC)2, and methyl isobutyl ketone-iodide have been chosen as reagents. The elements can be extracted successively and quantitatively from strong mineral acids without adjusting pH of the solution, and separated into two groups suitable for gamma-ray spectrometry. Samples of 100–200 mg dry weight were double-sealed into polyethylene bags and irradiated in a swimming pool reactor with a thermal neutron flux of 1013n·cm−2·s−1 for 44 hours. After a cooling period of 1–3 days, the samples were digested with microgram quantities of carrier in concentrated nitric acid and sulfuric acid at 150°C for 3.5 hours in a teflon bomb, then extracted as described above. The reliability of the analytical method was checked using reference materials Horse Kidney IAEA H-8, Human Hair NIES-5 and Tomato Leaves NBS-1573. Most of the results obtained for reference materials agreed with the certified values12. Chinese autopsy samples of hair and liver were presented.

Investigation on the applicability of Piety's on-line PSD-pattern recognition algorithm to boiling detection by neutron-noise at a swimming-pool reactor

The neutron noise signal of an initiation-of-boiling experiment performed at a swimming pool research reactor has been analyzed by the PSD-pattern recognition algorithm of Piety (1977); the results indicate that the onset of boiling can be detected by this method. Improved confidence statements for the statistical decision discriminants are given.

Probabilistic analysis of some safety aspects of a swimmingpool reactor

A probabilistic risk analysis of some safety aspects, not including radioactivity release, has been performed for the 10 MW (thermal) swimmingpool research reactor SAPHIR. This study concentrates on seven international initiating events found to be relevant with respect to accident sequences that could result with core melt due to the loss of coolant or overcritically. The results are given as core melt frequencies for the accident sequences. It could be demonstrated that the core melt hazard of the reactor is extremely low.

Selected inorganic chemical composition of mainstream cigarette smoke as a function of aerodynamic particle size

Described is a new method for studying the inorganic chemical composition of various fractions of mainstream smoke separated according to particle diameter. University of Kentucky 1R1 reference cigarettes were neutron activated in a 2MW swimming pool reactor. These activated cigarettes were then smoked on a conventional reverse puffing machine and the smoke immediately diluted 200: 1 with clean air. The diluted smoke was then separated into fractions based on particle diameter in a spiral centrifuge. The separate fractions were subsequently counted on a Ge(Li) detector coupled to the proper electronics, multichannel analyzer, and dedicated computer system. Data is presented showing the relative concentration ratios of K, Na, Cl, Br and Mn. Total sulfur was assayed by long-term low-background scintillation counting. The neutron activation analyses results show that the relative ratio of Na, Cl, Br, and Mn to K remains constant regardless of size from 0.1 to 2 μm aerodynamic particle diameters. Sulfur shows a definite chemical variability compared to the other measured inorganics and is enriched in the smaller particle sizes below 0.3 μm. Total carbon was also analyzed and data is shown which compares the relative ratios of K, Na, Cl, Br, S and Mn to the total carbon content. Sulfur is enriched compared to carbon in the 0.5 μm and smaller particles. The K, Na, Cl, Br and Mn show depletions compared to carbon in both the small and large particles, but an enrichment in the 0.3–0.7 μm particles. A comparison of the inorganic ratios in dropped cigarette ash and the ionic portions of the sized mainstream smoke aerosol is presented. A possible mechanism is presented to explain how the major mass amounts of the inorganics studied are transferred to smoke. This mechanism is one of a mechanical “entrainment” of pieces of inorganic residue that during the cigarette puff, break off from the coal and are transferred into the smoke stream. The “entrained” inorganic residue is subsequently regulated in its size distribution by the normal impaction filtration mechanisms of the tobacco column. These sized “entrained” inorganics then exit in the mainstream smoke. Because the bulk of these particles is made up of the “entrained” inorganic residue, they account for the major chemical mass of the inorganics studied, while the other mechanisms of inorganic transfer (volatilization, condensation, and nuclei contributions) are shown to be of minor importance to the overall chemical transfer.

Physics on the Fontenay-aux-Roses Vinka low temperature irradiation facility: A short review

Vinka is an irradiation facility working at temperatures between 17 and 25 K in the Triton swimming pool reactor. A brief review is presented of the main experiments which have been performed by our group in this facility.

Investigation of space-energy effects in the reactivity measurement by neutron noise with excore detectors in a reflected LWR

Practical application of the zero-crossing correlation method for measuring slightly-subcritical reactivities in a swimming-pool reactor required the use of detector locations in the reflector zone near to the core boundary. Experimental investigations of neutron-noise cross-power spectra showed significant deviations from the point-reactor model at higher frequencies (> 100 Hz). Nevertheless, the use of the point-reactor model was found to be a useful approach in the analysis of the zero-crossing correlation method, yielding results which agreed well with those obtained from the rod-drop method. The theoretical part of the work is concerned with a space-dependent model calculation in two-group diffusion theory to support the experimental findings. The model calculation can explain the trends observed in the neutron-noise spectra as well as the applicability of the point-reactor model to the zero-crossing correlation method. To obtain better insight, the calculations have been extended to neutron-noise spectra when one or both detectors are located in the core zone. In the case of a large core and widely-spaced detectors, with at least one detector in the core zone, a sink frequency appears in the spectra. This effect is well known in coupled-core kinetics.

Use of tetracycline as complexing agent in radiochemical separations

The use of the antibiotic agent tetracycline for analytical purposes in solvent extraction procedures is presented. Individual extraction curves for the lanthanides, zinc, scandium, uranium, thorium, neptunium and protactinium were obtained. Separation of those elements one from another, and of uranium from selenium, bromine, antimony, barium, tantalum and tungsten was carried out. In all cases benzyl alcohol was the diluent used to dissolve tetracycline hydrochloride. Sodium chloride was used as supporting electrolyte for the lanthanide separations and sodium perchlorate for the other elements mentioned. Stability or formation constants for the lanthanide complexes as well as for thorium complex with tetracycline were determined by using the methods of average number of ligands, the limiting value (for thorium), the two parameters and the weighted least squares. For the lanthanides, the stability constants of the complexes Ln(TC)3 go from 9.35±0.22 for lanthanum up to 10.84±0.11 for lutetium. For the Th(TC)4 complex the formation constant is equal to 24.6±0.3. Radioisotopes of the respective elements were used for the determinations. When more than one radioelement was present in an experiment, a multichannel analyser coupled to Ge(Li) or NaI(Tl) detectors was used for counting the activities. When only one radioisotope was used, counting of the radioisotopes was made with a single-channel analyser (integral mode counting) coupled to a NaI(Tl) detector. Uranium was determined by activation analysis (epithermal neutrons). Radioisotopes of the elements were obtained by irradiation in the IPEN swimming-pool reactor. The natural radioisotope2 3 4Th was used as label in the thorium experiments. In some separation procedures such as in the case of the pair uranium-neptunium, and of the pair scandium-zinc, the separation was obtained by properly adjusting the pH value of the aqueous phases, before the extraction operation. In other cases, addition of masking agents to the extraction system was required in order to perform the separation between the elements under study. In this way ethylenediaminetetraacetic acid (EDTA) was used as masking agent for scandium and the lanthanides in order to allow separation of uranium from those elements. Diethylenetriaminepentaacetic acid (DTPA) was used as masking agent for thorium in order to extract uranium into the organic phase. Separations of protactinium from thorium, and of uranium from protactinium and thorium, were accomplished by using sodium fluoride as masking agent for protactinium and DPTA as masking agent for thorium and protactinium at the same time. In the case of the separation of the lanthanides one from another it is necessary to resort to a multi-stage extraction procedure since the stability constants for those elements are too close.

A radiochemical investigation on the existence of polyneutron nuclei in the thermal neutron fission of 235U

A radiochemical search for polyneutron species X n has been made in the thermal neutron fission of 235U in the core of the swimming pool reactor, APSARA at Trombay. The study has been made using two probes viz. Pb and Rb using nuclear reactions of the type ( X n, Y. n ) where X = 8–16. It is concluded that if bound polyneutrons exist, they are not emitted in the thermal neutron fission of 235U with a yield of more than ∼10 −12/fission.