ISSN:0550-3043    

DOI:10.13182/NT69-A28474

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Handling of spherical fuel elements in a pebblebed reactor requires unique designs for the mechanisms involved. Once fuel elements are dropped on top of the core their motion follows statistical rules and they remain untouched and unchecked until, after approximately six months, they reach the bottom of the core; hence, the external fuel handling and monitoring facility.

ISSN:0550-3043    

DOI:10.13182/NT69-A28475

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

A method for accurate calibration of control rods of very small worth starts with a record of flux vs time produced by moving the rod back and forth between its stops a large number of times. This record is converted to reactivity by an inverse-kinetics calculation. The reactivity is fitted to a series of Legendre polynomials in rod position and a series of Gram polynomials in time, the latter to allow for reactor drift.

ISSN:0550-3043    

DOI:10.13182/NT69-A28476

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Measurements of fuel stack and cladding length changes by means of differential transformer elongation detectors on more than 50 fuel rods irradiated in the Halden Boiling Heavy Water Reactor (HBWR) have resulted in the following general conclusions regarding in-pile dimensional behavior of fuel rods.When a fuel rod is brought to power for the first time, the clearance between pellet stack and cladding will decrease with power due to the larger thermal expansion of the fuel.The radial temperature distribution through the fuel will be parabolic and the originally flat-ended cylindrical fuel pellets will therefore change to hourglass-shaped bodies with convex ends.The pellet stack will expand freely inside the cladding until at some power level the“corners”of the hourglass-shaped, hottest fuel pellets will first touch and then make force contact with the cladding.The force system set up between the fuel stack and cladding will increase with power and affect their dimensional changes so that these are no longer decided by individual thermal expansion alone.The mechanical interaction will increase with power and the cladding will finally be permanently deformed to fit the external dimensions of the pellet stack, and the fuel rod will at this point look like a bamboo rod.Mechanical interaction will later take place only if the power is increased beyond its previous level, as long as fuel swelling has not affected the fuel outside dimensions.Knowing that the cladding material loses ductility because of irradiation damage and chemical attack, the conclusion is reached, therefore, that fuel should be operated hard when new so that the bamboo ridges and other forms of strain concentrations caused by interaction are formed when the cladding is ductile.To avoid further interaction, the power should preferably be tapered off gradually with burnup so that part of the volume used to accommodate thermal expansion can be made available for the volume increase because of fuel swelling.

ISSN:0550-3043    

DOI:10.13182/NT69-A28477

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

The deposition of iodine on low chromium-alloy steel (1% Cr—¼% Mo alloy) has been investigated in vacuo at 316, 400, and 482°C using a pseudoisopiestic (static) method. An adsorption isotherm was obtained at 400°C over an iodine (monotomic) pressure range of 2.9×10−9to 5.1×10−7atm. The levels of iodine deposition at 400°C ranged from 3.8 to 23.2µg I/cm2; these values are in agreement with data obtained using transpiration techniques.The low-level sorption data are interpreted on the basis of the dissociation of I2to yield monatomic iodine as well as the interaction with the steel surface to form volatile iron iodides, which were deposited in cooler regions of the apparatus. The high-level sorption behavior of iodine on steel is in accord with the expected behavior based on the thermodynamic properties of FeI2(s).

ISSN:0550-3043    

DOI:10.13182/NT69-A28478

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

By applying a statistical environment definition at the initiation of multifuel capsule radioisotope thermoelectric-generator development, the continual high cost expenditure attributed to redesign common to programs advancing the state-of-theart can be minimized. The design synthesis is accomplished by first establishing environmental conditions (e.g., peak reentry temperature) based upon statistically combining the characteristic variables required to define the environment. Selected values from this range of probable environmental conditions along with the structural characteristics are then applied to establish the design requirements of the system. The technique to acquire this result is illustrated by an example system design. A description of the many environmental factors and design requirements imposed on these systems are also discussed in this paper.

ISSN:0550-3043    

DOI:10.13182/NT69-A28479

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Microwave techniques, as used for the detection and measurement of moisture in reactor coolant gases, operate because of the resonant frequency change of a microwave cavity (sensor) through which the sample gas flows, due to the corresponding change in its dielectric constant. For the experimental system, a moisture detection sensitivity of 15 ppmv/µV for sample gas at STP results for 10 mW of microwave oscillator power. The minimum moisture detection level of about 2 ppmv depends upon total system noise. Gas transport time limits the speed of response, as does the time constant of the synchronous demodulator of the sample phase-lock amplifier. For thermal equilibrium conditions, the maximum instrument drift for a one-hour interval equates to an equivalent moisture concentration range of 10 ppmv.

ISSN:0550-3043    

DOI:10.13182/NT69-A28480

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

A method for the determination of oxygen in carbon and organic materials, employing the16O(3T,n)18F reaction, is described. The technique is applicable for amounts of12O as low as 0.1 mg, and the application of the method to the determination of the oxygen content in activated carbon is reported.

ISSN:0550-3043    

DOI:10.13182/NT69-A28481

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Apparatus for the detection and measurement of small amounts of deuterium in small-sized samples by the photoneutron reaction is described. With a 25-Ci24Na gamma-ray source, a net response of 7 counts/ min per microgram of deuterium in sample sizes from 0.1 to 1.0 ml is obtained. The lower detection limit in such samples is ~1.7µg of deuterium, or the amount in 0.05 ml of natural water.

ISSN:0550-3043    

DOI:10.13182/NT69-A28482

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

To measure the evaporation rate of solids in vacuum, the evaporating substance was condensed on a water-cooled lead plate. The plate with the condensate was removed, irradiated by neutrons, and etched in a mixture of nitric and hydrofluoric acids, and the radioactive isotopes in the solution were identified.The possibilities of the method are illustrated by the measurement of the molybdenum metal and zirconium carbide evaporation rates. The amount of molybdenum (99Mo) was determined by directγ-spectrometry of the solution. In the case of zirconium, radiochemical isolation of95Zr from the mixture of antimony, zinc, tantalum, and hafnium present in the solution in amounts commensurable with that of zirconium was suggested.The vaporization experiment was carried out in a vacuum ~10−5to 10−6Torr. The measured values of the molybdenum and zirconium carbide evaporation rates in the temperature range ~1900 to 2400°C are given.

ISSN:0550-3043    

DOI:10.13182/NT69-A28483

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor