ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Robotics & Remote Systems
The Mission of the Robotics and Remote Systems Division is to promote the development and application of immersive simulation, robotics, and remote systems for hazardous environments for the purpose of reducing hazardous exposure to individuals, reducing environmental hazards and reducing the cost of performing work.
Meeting Spotlight
ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
April 2025
Fusion Science and Technology
Latest News
Norway’s Halden reactor takes first step toward decommissioning
The government of Norway has granted the transfer of the Halden research reactor from the Institute for Energy Technology (IFE) to the state agency Norwegian Nuclear Decommissioning (NND). The 25-MWt Halden boiling water reactor operated from 1958 to 2018 and was used in the research of nuclear fuel, reactor internals, plant procedures and monitoring, and human factors.
V. K. Paré, J. T. Mihalczo
Nuclear Science and Engineering | Volume 56 | Number 2 | February 1975 | Pages 213-218
Technical Note | doi.org/10.13182/NSE75-A26662
Articles are hosted by Taylor and Francis Online.
A theory is developed for the cross-power spectral densities between the signal from an ionization chamber containing a 252Cf neutron source, which provides the initiation of fission chains in a reactor or neutron multiplying assembly, and the signals from detectors of particles from fission chains in the reactor. Previously derived spectral densities between two detectors are modified to include the effects of the inherent and 252Cf source in the reactor. Calculations of the amplitude of the coherence function for noise measurements, both conventional and 252Cf, for the reactor at the Fast Flux Test Facility are presented and can be used to estimate the time required for a measurement with a given precision. The equivalence between the expressions developed here and those previously developed for time-domain measurements of this type is also shown. Use of a 252Cf chamber makes possible a new method of determination of the reactivity which is independent of the inherent source strength and detection efficiency. This method does not require a calibration near delayed criticality as do the previously used methods such as break frequency or coherence amplitude noise analysis and modified source multiplication measurements. It requires the knowledge of some properties of the ionization chamber containing 252Cf which can be determined outside the reactor. Since this method does not require a calibration near delayed criticality, it may be used in the initial loading of a reactor to determine the reactivity before criticality is achieved. The independence of detection efficiency also makes it useful during initial loading, since large changes in detection efficiency can occur with loading. The independence of the method on the inherent source would be advantageous during refueling of a reactor when the inherent source in the fresh fuel inserted may be much less than that of the burnt-up fuel removed. The method may also be useful in determining the reactivity of assemblies where sufficient fuel to achieve criticality is not available.
