ML20009A889
| ML20009A889 | |
| Person / Time | |
|---|---|
| Issue date: | 08/03/1978 |
| From: | Levine S NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Case E Office of Nuclear Reactor Regulation |
| References | |
| RIL-032, RIL-32, NUDOCS 8107140417 | |
| Download: ML20009A889 (8) | |
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NUCLEAR REGULATORY COMMISFION WASHINGTON, D. C. 20585 g
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MEMORANDUM FOR: Edson G. Case. Acting Director i
Office of Nuclear Reactor Regulation 1
FROM:
Saul Levine, Director W
Office of Nuclear Regulatory Research
SUBJECT:
RESEARCH INFORMATION LETTER #32 IMPROVEMENTS IN THE AEROSOL BEHAVIOR CODE FOR RADIOLOGICAL ASSESSMENTS OF LMFBRS
REFERENCE:
J. A. Gieseke, et. al., " Characteristics of Agglomerates of Sodium 0xide Aerosol Particles,"
BMI-NUREG-1977,(August 1977)
Introduction This memorandum transmits the results of completed research on the measurement of sodium oxide aerosol properties.
Sodium oxide is the key aerosol constituent in postulated severe LMFBR accidents. This work was 47, completed as part of the Aerosol Measurements and Modeling program at Mt Battelle Columbus Laboratories under the direction and sponsorship of p'
the Advanced Reactor Safety Research, Office of RES. The work consisted M
primarily of the experimental measurement of the effective density of sodium-oxide aerosols as a function of agglomerate size. The effective density is an important parameter in predicting how an aerosol population will behave in an enclosed containment in tems of natural removal
%i precesses..For the most severe postulated LMFBR accident scenarios (HCDA and core molt), sodium-oxide aerosol represents the highest airborne mass concentrations in the containment vessel and is expected to dominate and govern the behavior of the fuel and fission product acrosol. Therefore, as a first step in improving the aerosol behavior code, HAARM-2, separate effects work was carried out on sodium-oxide i
acrosol.
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The results of these separate effects measurements have been incorporated into the models of the aerosol behavior code HAARM-2, and together with some additional improvements used to generate a new version called HAARM-3. The improved models in HAARM-3 provide a more realistic description of particle characteristics ar.d thereby allow improved estimates of sodium-oxide aerosol behavior during a postulated HCDA. The HAARM code is used by NRR for LMFBR site radiological consequence assessment.
Enclosed is a copy of the HAARM-3 users manual for operation of the code. The code has recently been placed on the Brookhaven computer and Dr. John Long of your staff is familiar with its operation.
Release of the code was expedited to be available for NRR review of the FFTF-FSAR.
The results of the research used in improving the code have been reviewed at Research Review Group meetings with participation by NRR staff.
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Discussion
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An important aspect in performing LMFBR accident analyses for siting evaluations is the postulated release from the containment of radioactivity in the fom of aerosol particles. The prediction of aerosol behavior in containment depends on the microscopic characteristics of the individual particles. Aerosol behan or processes of most interest to LMFBR accident j
analysis are agglomeration and growth of particles and settling.
l Particle shapes and densities have a pronounced effect on the settling j
i velocities of the individual aerosols. Also, certain mechanisms for j
agglomeration are known to depend on the cross sectional areas of the
-1 individual particles, a parameter which is directly related to particle shape and density. Because of the complexity of the processes controlling aerosol behavior, it is nearly impossible to derive information on these aerosol characteristics from integral experiments. Therefore, separate j
effects experiments were perfomed to determine the physical characteristics of sodium-oxide aerosols.
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A Milliken-cell apparatus was chosen for performing measurements because themal forces as well as agglomerate physical properties could be detemined. In addition to the Milliken-thermal cell, agglomerate properties were further characterized through electron microscopy. The 4
primary objective of the measurements was the determination of the sodium-oxide agglomerate effective density. The density of the agglomerate l
differs from that of the actual material in that as the agglomente grows there are voids or holes between the particles and the density is 1ess than that of the solid material. These measurements allow determination of the real radius, which in turn affects the collision area, an important
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parameter in some of the agglomeration processes. As a part of the determination of the effective density, the aerosol primary particle size distribution was determined and the value for the mass median particle radius (0.5 pm) used in the HAARM-3 code was verified. Also another parameter, the first order slip correction factor, was detemined (avalueof1.37)andthisvaluewasincorporatedintothecode.
The primary particle size distr'bution of the sodium oxide was detemined by electron microscopic techniques. The aerosol was generated by
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burning sodium in air. The results indicated that the primary particle size distribution may be modeled by a log normal distribution with a geometric mean diameter of 0.45 pm and a geometric standard deviation of 1.47. Knowing the primary size distribution one may relate +he equivalent i
mass diameter of particles comprising an agglomerate. The equivalent mass diameter is the diameter of a sphere having a mass equal to that of the agglomerate. Using the equation for a log normal distribution and the equation relating equivalent mass diameter to the primary particle size distribution parameters (Ref.1), one can derive an expression for i
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, t s(thedensitycorrectionfactor). This equation permits a direct comparison of a measured values and the theory of Kop et al. (Ref. 1).
Themeasurementsindicatedareasonableagreegenttothetheoryforan average primary particle density of 2.27 g/cm.
Evaluation and Ap;,lication M
The characteristics of sodium oxide agglomerates, available from the measurements, have been incorporated into the computer code. Also, Provisions were made to the code to account for the effect of nonspherical shapes'of agglomerates on the mobility and on the collision cross section.
Calculation of the values of a allow the determination of a new radius instead of using a radius based upon the theoretical density. The increased radius has the effect of enhancing the collision area for gravitational agglomeration and increasing the settling velocity.
Comparison calculations were made showing the differences between.
HAARM-2 and HAARM-3 predictions of airbe ne mass concentrations and leaked mass for various assumed initial aerosol releases in a typical LMFBR containment. The results of these comparisons are attached in Table 1 and Figures 1 and 2.
Using the HAARM-3 code with the improved models there is a reduction in the amount of leaked mass as a function oftime(Figure 2). Also included, Figure 3 is a comparison of predictions of suspended aerosol mass concentration vs. time for each of the two y
codes with an integral acrosol test. This test, the first of a series being performed at the Containment Systems Test Facility (CSTF) at HEDL for DOE, represents the largest known aerosol test performed to date.
The CSTF. vessel is about.21/2 scale model of reactor containment, with respect to vessel height, the key geometry parameter in the agglomeration and settling of aerosols. As can be seen in Figure 3, the HAARM-3 code provides much better agreement with the experimental results.
Future Work work in this area is being directed towards the characterization Currently (U0,) aeroso1'..shich includes the detemination of the aerodynamic of fuel properties bf the particles. With the completion of this work, program emphasis will be placed on the interaction of mixed aerosols (sodium-oxide aad fuel) primarily in large integral tests. The goal of this research is the verification of the HAARit-3 code. A code verification plan is currently being developed to implement the accomplishment of that goal, p
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Recomendations The HAARM-3 code will allow NRR to perform improved estimates of the depletion of sodium and fue,1 aerosol in the reactor building and other containment sp',ces for use in radiological assessments of postulated LMFBR accidents.
It is recommended that NRR use the HAARM-3 code as opposed to earlier versions in performing aerosol calculations in view of the informatici presented in this RIL. For further information on the application ai.d use of HAARM-3 contact Dr. John Larkins in RES.
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Saul Levine, Director Office of Nuclear Regulatory Research
Enclosure:
HAARM-3 Users Manual m
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2 hrs 15 15 I day 68 58 30 days 76 65 10 2 hrs 72 65 1 day 255 110 30 days 269 113 100 2 hrs
- 480 158 I day 865 160 30 days 870 161 Pertinent Input Data:
.h Leak Rate - 0.1 percent per day Initial R50 = 0.5 um Initial cR = 2.0 Cas Temperature - 310 K.
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