SCALE Training Course

Registration forms and other information are included in the back of this Newsletter. Those who have preregistered for the course via the form in the last Newsletter must return the enclosed registration forms with payment prior to March 15 to keep their reserved space at the course. Those who have not preregistered should return the registration forms and payment as soon as possible to be placed on a waiting list on a first-come basis.

SCALE-4.3 to be Released this Summer

Several SCALE modules are being added to the PC version for the first time, including the SAS1 1-D shielding analysis sequence, the SAS2 depletion/decay sequence, ORIGEN-S, XSDOSE, and COUPLE. In the PC version only, there will be a new shielding control module, QADS (NUREG/CR-5468, ORNL/CSD/TM-270), that automates the use of the QAD-CGGP code for 3-D point kernel calculations.

SCALE-4.2 Minor Modifications

KENO-V.a: (1) Corrected error that permitted a case with a negative radius to run. (2) Added calculation of the energy corresponding to the average lethargy causing fission and made the printing of this information (i.e., NUB=YES) a default parameter. (MRR 94-030)

All Control Modules: Modified MIPLIB to check for resonance data on the cross-section library used to determine whether to perform resonance corrections for a nuclide. Previously, a flag in the Standard Composition Library was used to make this determination. (MRR 94-032)

All Control Modules: (1) Corrected calculated thickness ("lbar") of cylindrical and spherical annuli for input to BONAMI. (2) Modified reading of Dancoff factor keywords in MORE DATA to detect and prevent erroneous keyword input. (3) Changed the label "lbar" printed by CSAS in PARM=CHECK output to "abar." (4) Replaced the 123GROUP and 218GROUP cross-section-library keywords with 44GROUP and 238GROUP. The former libraries, which were the least used of the standard SCALE libraries, were removed as defaults so the new ENDF/B-V libraries, which give more accurate results, could be accessed directly via keyword input. (MRR 94-025 and 026)

COUPLE: Corrected an error that occurred when only fission product yield data were being updated. Note that this error does not occur when using COUPLE in the SAS2 sequence. (MRR 94-023)

XSDRNPM: (1) Modified to scale the weighting flux so that minimum value is 1E-20. This modification was made to reduce the likelihood that an underflow would occur when creating a weighted cross-section library for problems where there are large variations in the flux (many orders of magnitude). (2) Corrected an error that caused broad-group-flux edits to print bad values. (MRR 94-020)

KENO-V.a: Corrected errors in the starting points edit obtained when PSP=YES. (MRR 94-019)

AIM: Corrected error that created a bad magic word in a binary library if a magic word position occurred as the last position of a transfer array in the BCD data. (MRR 94-021)

The changes to the Standard Composition Library were very extensive and fall into several categories. Additions were made so that nearly all the elements are given by both their full name and by their chemical symbol. The full-name elements are all given as naturally occurring abundance nuclides, while a few of the chemical symbol nuclides are given as the principal isotope. For instance, HYDROGEN would include trace amounts of deuterium, while H would be 100% H-1.

The isotopic distribution table was changed to include most of the elements. Arbitrary materials may now contain more than one multiple-isotope nuclide. In addition, the specially weighted elements in stainless steel and in Inconel were added, specifying the natural abundance of each.

Atomic masses for isotopes were taken from ENDF/B-VI, if available. Atomic masses for naturally occurring elements were taken from ENDF/B-V, if available. Remaining atomic masses were taken from GE Chart of the Nuclides or the CRC Handbook of Chemistry and Physics.

SCALE and RSIC Staffs Now in Same Division at ORNL

Words to the Wise...

Don't Use the 123-Group Library for High-Enriched Systems

The 123-group cross-section library in the SCALE system was recently observed to have a non-conservative discrepancy of approximately 3.0 to 3.5% for an array of packages containing high-enriched uranium. The calculated discrepancy is in comparison with other calculations performed with MONK using point data and with SCALE/KENO-V.a using both the 27-group ENDF/B-IV library and the more recently developed ENDF/B-V multigroup libraries. A simple, infinite system of UO2F2/H2O was selected as a representative system that could be used to assess the cause of the discrepancy. The approach was to analyze the system using both the 123- and 238-group libraries for a range of hydrogen-to-fissile material ratios (H/X) and for U-235 enrichment values of 99.99 wt % and 5.0 wt %. The variation in H/X values provided a change in the system spectrum from thermal (H/X > 200) to fast (H/X < 10), whereas the enrichment variation was needed to assess whether the discrepancy occurred for low-enriched systems.

The results for the high-enriched cases indicate that for well-thermalized systems (H/X > 200) the 123-group library yields k-infinity values that are approximately 0.5% lower than values obtained with the 238-group ENDF/B-V library. However, as H/X decreases and the spectrum hardens, the difference in k-infinity results between the 123-group library and the ENDF/B-V libraries increases. The discrepancy increases from <1% for H/X=100 to approximately 5.5% for H/X values in the range of 5 to 10. For the low-enriched system, a comparison of the 238- and 123-group results indicated agreement within 0.5% for the entire range of H/X.

The cause of the discrepancy was determined by observing that the 123-group U-235 cross sections are generally higher in the resonance energy range between 1 and 100 eV. The reason for the high cross sections in the resonance region can be traced back to a lack of resonance parameters for U-235 in the 123-group library. The U-235 data as taken from GAM-THERMOS were pre-shielded at infinite dilution. Thus, the same U-235 cross sections are used for all cases. The use of a single value is incorrect in general, but is especially bad for the high-enriched cases with low H/X values. The cause of the discrepancy was confirmed by using ENDF/B-V data to generate a new set of U-235 cross-section data for the 123-group library. The results indicated that the modified 123-group library provided excellent agreement with the 238-group library for all the high-enriched UO2F2/H2O systems.

The SCALE staff recommends that the 123-group library not be used for analysis of high-enriched systems because of the deficiency of the 235U data. In fact, any calculations performed with the 123-group library should be considered biased until demonstrated otherwise. Careful consideration should be given to the range of validation and applicability of the validation to the systems at hand. The recently developed 44- and 238-group libraries provide rigorous treatment of the well-tested ENDF/B-V data and should be better libraries for use with high-enriched systems. Similarly, the SCALE 27-group library has been demonstrated to perform well for high-enriched systems. However, for systems with an average energy causing fission (AEF) outside the range of available critical data, independent analyses with other codes and data should be investigated and trends in k-eff as a function of AEF should be carefully studied.

REGISTRATION FORM

SCALE Training Course

Pollard Auditorium, Oak Ridge, Tennessee

April 24-28, 1995

Name _____________________________________________

Citizenship ______________________________________

Organization _____________________________________

Mailing address __________________________________

__________________________________________________

__________________________________________________

Telephone: _________________________ Fax: _________________________

__ I preregistered for the course

__ I did not preregister, please place me on the waiting list

Please enclose registration fee of $400 payable to: SCALE Training Course

Please mail form and payment to:

Steve Bowman

SCALE Training Course

Oak Ridge National Laboratory

P.O. Box 2008, MS 6370

Oak Ridge, Tennessee 37831-6370

The registration fee entitles the registrant to attend all conference functions, including working lunches on Monday through Thursday and a reception on Monday evening. DOE employees are exempt from the registration fee but must pay for group meals provided with the course. If you are a DOE employee, you will be sent more information upon receipt of your registration form.

Please fill out the attached SCALE Experience / Preferences Form and return along with this registration form. This form will aid the instructors in planning work groups prior to the course.

NOTE: Course attendance is limited.

To those who preregistered by January 24: You must return this registration form with payment by March 15 to keep your reserved space at the course. No refunds will be made, but you may send a substitute in your place. After March 15, any remaining spaces will be available to those who did not preregister on a first-come basis. To those who did not preregister by January 24: Return your registration form and payment as soon as possible. You will be placed on a waiting list on a first-come basis. After March 15 you will be notified whether you will be able to attend the course. If there are no vacancies available, your registration payment will be returned to you. PLEASE REGISTER EARLY!

SCALE Experience/Preferences Form

Organization

HOTEL REGISTRATION FORM

Return to:

GARDEN PLAZA HOTEL

215 S. Illinois Avenue

Oak Ridge, Tennessee 37830

Telephone: 615/481-2468

Fax: 615/481-2474

Please reserve a room in my name in the block of rooms available for the SCALE Training Course.

Block room rate: $54 per night, including tax. Deadline for reserving a room at this special rate is March 15.

Name _____________________________________________

Organization _____________________________________

Credit card No. __________________________________

Arrival date and time: ___________________________

Departure date and time: _________________________

Airline Discount for SCALE Training Course

10% discount off regular coach fares

5% discount off any published domestic fare

(except group, inclusive tour, military, government,

senior citizen, zone and Visit USA fares)

Some restrictions will apply and seats are limited. To obtain these special fares, call or have your travel agent call 1-800-241-6760. Refer to File No. I-5355. Reference to meeting title is not necessary.

SCALE Training Course Agenda

Registration, Opening Remarks, System Overview

Cross Section and Material Processing - Lecture and Problem Session

Criticality Safety Sequences - Lecture and Problem Session

Tuesday

Criticality Safety Sequences - Lecture and Problem Sessions

Wednesday

Depletion/Decay Sequences - Lecture and Problem Session

1-D Shielding Analysis Sequences - Lecture and Problem Session

Thursday

3-D Monte Carlo Shielding Analysis Sequences - Lecture and Problem Sessions

Friday morning

Parallel sessions (attend one of your choice)

Heat Transfer Sequence - Lecture and Problem Session

Criticality Safety Sequences - Question and Answer

Depletion/Decay and Shielding Analysis Sequences - Question and Answer

Address all correspondence (including address additions or changes) to: