Shielding Codes Group

Calculations used a two-dimensional model based on the KARE diffusion theory code and WOXX three-group cross sections. Homogenization (self-shielding) factors were determined from fine structure calculations using the Tranvar thermal transport code. Several other cross section schemes and transport codes in common usage were also Investigated, but no significant differences were noted. 

The angular flux spectrum was computed using the DTF-IV code in an approximation (Lobatto quadrature) to the transport equation. The GAM-]1 code was used to obtain 27-group, P, cross sections Cor the constituents of the subcritical assembly. Energy self-shielding calculations for were performed with the... 

Extensive criticality calculations have been done for this rack to ensure that it meets the applicable criteria under all conditions. The calculations were performed using a four-energy-group, X-Y representation of the racks in the PDQ-07 (Ref. 4) program. Cross sections fo>r the POQ-07 model were obtained from LEOPARD (Ref. 5) super cell calculations, which also yielded fast and thermal spectra for use in RODWORTH (Ref. 6), a blackness theory code which was modified to account for boron particle self-shielding. The resulting cross sections were then - used in a PDQ-07 calculation which explicitly modeled the system geometry. 

The ALICE Monte Carlo Neutron Transport Code uses the probability table method for all 175 energy groups which span the energy range from thermal to 20 MeV. The code is used for criticality as well as shielding problems. 

The neutron multiplication factor (Keff) of each benchmark core was calculated using the Monte Carlo criticality code KENO IV. The 123-group XSDRN cross-section set was used. Resonance self-shielding was accounted for in the U isotope only. Self-shielding corrections were made with the NIT AWL code from the AMPX package. ... 

W. R. COBB, 123-Group Neutron Cross Section Data Generated from ENDF/B-II Data for Use in the XSDRN Discrete Ordinates Spectral Averaging Code, DCL-16, Radiation Shielding Information Center (1971). 

All of the analyses utDized the SCALE 27 neutron-group cross-section library based on ENDF-IV. The resonance isotopes were corrected for resonance self-shielding via the Nordheim Integral treatment in the NITAWL code. Prior criticality studies using this library on several EPRI critical experiments indicated that for rite coolant-to-fuel voliune ratio and corresponding lattice pitch of the TMI design cote, the K-effective calculated would range from 0.98 and 0.99. 

For each experiment, the effective multiplication factor keff is computed by running the three-dimensional Monte Carlo code KENO IV (Ref. 5), with a 16-group Hansen and and Roach CTOSs-section library, taking into account reso-tuinces, self-shielding, and the Dancoff correction. 

The most widely used computer code to process evaluated nuclear data into group cross section libraries is the NJOY code [4.2]. In addition, a code may be needed to convert the data produced by NJOY into the form required by a particular code scheme. For the treatment of resonance shielding auxiliary codes can be required to produce the appropriate parameters (e.g. the CALENDF code [4.6] for subgroup parameter calculations). There are other processing codes, such as GRUCON [4.3], AMPX [4.4] and ETOE [4.5] which are used mainly in the nuclear research centres where they were originated. 

However, before doing that, it is appropriate to note that this distinction of the two types of engineering projects has a significant influence on some of the characteristics we discussed, such as the role in society and the code of ethics. That arises out of the fact that development projects are, to an extent, shielded from direct interaction with society outside of the project the group of direct stakeholders is very limited. As a result, engineers in development projects have... 

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