Criticality safety analysis

DOE 0 420.1 Facility Safety Requires fire hazard analysis and natural phenomena analysis for all facilities. For Hazard Category 2 or 3 nuclear facilities only, requires a criticality safety evaluation. Criticality Safety Analysis Fire Hazard Analysis Effects of natural phenomena hazards on facility systems, structures, or components (SSCs) included as part of safety analysis documented in the Safety Analysis Report (SAR), Basis for Interim Operation (BIO), or Auditable Safety Analysis (ASA). 

N. F. Landers and L. M. Petrie, CSAS4 An Enhanced Criticality Safety Analysis Module with an Optimum Pitch Search, Sect. C4 of SCALE A Modular Code System for Performing Standardized Computer Analyses for Licensing Evaluation, NUREG/CR-0200, Rev. 4 (ORNL/NUREG/CSD-2/R4), Vols. I, II, and III (draft Febmary 1990). Available from Radiation Shielding Information Center as CCC-545. 

V11.15. Computational methods that directly solve forms of the Boltzmann transport equation to obtain k j are preferred for use in the criticality safety analysis. The deterministic discrete ordinates technique and the Monte Carlo statistical technique are the typical solution formulations used by most criticality analysis codes. Monte Carlo analyses are prevalent because these codes can better model the geometry detail needed for most criticality safety analyses. Well documented and weU validated computational methods may require less description than a limited-use and/or unique... 

VII.63. The use of INF isotopics in the criticality safety analysis means that any computational methods used to predict the isotopics should be validated, preferably against measured data. The reduced reactivity in INF is due to the decrease in fissile inventory and the increase in parasitic, neutron absorbing nuclides (non-fissile actinides and fission products) that build up during bumup. Broadhead [V11.23] and DeHart [V11.24] provide information to help identify the important nuclides that affect the reactivity of PWR irradiated fuel. The INF nuclides that can be omitted from a safety analysis are the parasitic absorbers that can only decrease k jj further if included in the analysis. Neutron absorbers that are not intrinsic to the fuel material matrix (gases, etc.) must also be eliminated. 

VII.37] DEHART, M.D., PARKS, C.V., Issues Related to Criticality Safety Analysis for Bumup Credit Applications , Nuclear Criticality Safety, ICNC 95 (Proc. 5th Int. Conf., Albuquerque, 1995), Univ. of New Mexico, Albuquerque, NM (1995) lb.26-36. 

A series of experiments and complementary calculations using the KENO program on boOi bare and thick-polyethylene-reflected, graphite-moderated cubic arrays of 8 nominally 15.7 kg 17(93.2) metal cylinders, has been started. Data from these experiments supplement that on unmoderated and hydrogenously moderated arrays of the same metal cylinders, and so will be valuable in the analysis of the effects of array moderation and reflection. Also, the data provide valuable check points lor validation of calculational techniques, such as the KENO program, that are used in nuclear criticality safety analysis. This summary presents data calculational results on the first several ejqperlmentsiin the series. 

The odier major vantageof the method is the abiliiy to use very detailed cross-section information instead of group-averaged cross sections. While much work is done usii% detailed cross sections, the lack of extensive validation of particular sets of data has thus far.prohibited the use of such data in routine criticality safety analysis. 

Criticality Safety Analysis of an LWR Fuel Assembly Shipping Container, E. Foss (Gulf-UNFC), R. Kr<4 p (UNC-New Haven)... 

H. TOFFER, Fuel Storage Basin Criticality Safety Analysis Report and Technical Basis, DUN-7624, Douglas United Nuclear (December 1071). 

A criticality safety analysis was carried out using a combination of experimental aw o h-tb-critical data for PuOk-UOk fuel pins similar to those to be transported in the Model 60 and computer code c dilations (see Table I). This analysis showed that a Mpdd 60 may be loaded with up to 120 FFTF driver fuel pins and that a sin e Fissile Class n shipment may consist of up to 12 loaded containers. 

The criticality safety analysis of the F-144-1 showed that the critical number of undamaged containers is 51 and that, under hypothetical accident conditions, the maximum of four damaged containers is 0.73 [0.697 4. 007)]. The addition of a fifth container would not significantly Increase keff under hypothetical accident conditions consequently, fiie transport index was conservatively taken to be 50/5 10. 

C. L. BROWN, Criticality Safety Analysis-Model 60 Shipping Package for FFTF Driver Fuel Pins, BNWL-1512, Battelle-Northwest (Nov. 1970). 

An Engineering Approach to Criticality Safety Analysis in an Irradiated uel Cosk,... 

There are different ways to i roach the nuclear criticality safety analysis of an irradiated fuel cask. This is true in terms of the analytical tools and nuclear data used as well as in the case of hiel configurations considered. In the former case, approaches range from that of a pure "physics" approach in which keff is calculated to a bi degree of accuracy with specialized codes and a multigroup cross-secti< set to that of an "engineering" approach in which keff is determined with a generalized code and a few-group cross-section set to a less accurate but more conservative value. 

Criticality Safety Analysis of the Special BNW Nuclear Materials Storage Facility,... 

The results of the criticality safety analysis show that most of the fissionable material placed in the Battelle-Northwest storage facility is safe geometry in the tubular storage array provided the U or effective Pu enrichment is limited, and that either moderation or fissile density is limited. In a few cases it is necessary to limit the fissile mass placed in storage tubes to provide criticality safety. The tubular storage array was constructed with a minimum amount of concrete between adjacent locations to maximize the amount erf fuel that may be stored. Consequently, a Monte Carlo analysis of the entire array was performed which determines the... 

Fine Group Master Cross-Section library for Criticality Safety Analysis... 

H. TOFFER, Criticality Safety Analysis Report Sub-critical Measurements in the Hanford N Reactor Fuel Storage Basin, DUN-7824 ADD.l, United Nuclear Industries, Inc. (Jan. 1975). 

Finally, a computer code provides only a value of keff, not a criticality safety analysis. The safety engineer must identity possibly hazardous situations, such as spills, flooding, or double batching, and use the computer code to evaluate them. Use of Monte Carlo calculations together with experimental data and calculatlonal models serves to reduce the number of computer calculations and to provide a cross check of results. 

G. R. HANDLEY, Some Effects of Water l rinklers on Array Criticality Safety Analysis, Nuct. TechnOl.,... 

Operations that involve the handling, processing, and storage of fissionable materials have an element of risk for accidental criticality. This risk is kept acceptably low by applying properly established limits and controls on equipment design and procedural operations to assure subcriticality. These limits and controls are established by criticality safety specialists using a procedure com monly referred to as criticality safety analysis. 

When a criticality safety analysis is Completed, those who are reviewing and applying the results and those who are to perform the operations need assurance that the analysis is correct. If not correct, a potential criticality hazard could exist... 

Certain parts of a criticality safety analysis must be correct and complete or the analysis is null and void. These essential parts are as follows ... 

The goal of any quality assurance program in criticality safety is to ensure that limits have been accurately established and will contribute to a safe operation. Computers are relied on to a great extent in most criticality safety programs and consequently are a key element in quality assurance programs in criticality safety. Computers are used at the Lawrence Livermore Laboratory (LLL) not only directly in criticality safety analysis but also in management of numerical and bibliographic criticality data that are needed for the validation of computational methods. 

The purpose of this presentation is to describe some common errors in nuclear criticality safety analysis un- j covered during the review of license an>llcation8 made in... 

QA in Criticality Safety Analysis Needs Experimental Studies, P. R. LScorchi, J. P. LeQerc, J. C Puit (C -France)... 

In normal operation, plutonium nitrate solutions may be concentrated to 300 to 400 g Pu/litre. The maximum expected concentration is 600 g/litre. The nitric acid content will range from I to 10 For the criticality safety analysis, it is as.sumed that the concentrator contains plutonium nitrate. Plutonium concentration is not limited however, for the calculations, the most reactive concentration from the standpoint of criticality is assumed to be 175 g Pu/litre, as experiments have shown the minimum critical volume for Pu(N03)4 solutons to occur at about this concentration. -... 

H. TOFFER, Nuclear Criticality Safety Analysis and Technical Basis for the Storage of N Reactor Fuels in K Reactor Basins 1900 Ton Capacity, UNI-283 Addendum 1 (Apr. 1976). 

SCALE System Cross-Section Validation for Criticality Safety Analysis, 4. M. Hathout (Al-Azhar Univ Egypt), R. M. Westfall (UCC-ND), H. L. Dodds. Jr. (Univ of Term)... 

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