Fuel Performance and Fission Product Release Studies for Defected Fuel Elements

Lewis, Brent J.; MacDonald, R.D.; Ivanoff, Nicholas V.; Iglesias, F.C.

doi:10.13182/nt93-a34845

Cited by 49 publications

(26 citation statements)

References 33 publications

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“…On the other hand, Mo is readily soluble under aqueous conditions so that it will be rapidly washed out of the defective rod as MoO 2À 4 . In fact, these predictions are consistent with observations from experimental loop irradiations at the CRL with defective fuel rods [15,24]. In addition, in agreement with Section 2.2, leaching experiments were performed on spent CANDU rods to measure the combined gap and grain-boundary inventories of 137 Cs, 129 I, 90 Sr, 99 Tc and 14 C, which suggested that technetium is not a volatile species and was unlikely to be found in the gap [25].…”

Section: Fission Product Release Modelsupporting

confidence: 86%

“…This work involves the computed isothermal phase equilibrium of Mo and Tc in liquid water as portrayed in Pourbaix diagrams, and the volatility of these species in a steam atmosphere with a Gibbs energy minimization procedure [5][6][7]. Based on insights provided by the thermodynamic analysis, a fission product release model is developed considering the physical mechanisms of release from defective fuel elements and uranium contamination on in-core surfaces [8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic considerations and prediction of the primary coolant activity of 99Tc

Lewis

Thompson

Akbari

et al. 2005

Journal of Nuclear Materials

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Section: Fission Product Release Modelsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Thermodynamic considerations and prediction of the primary coolant activity of 99Tc

Lewis

Thompson

Akbari

et al. 2005

Journal of Nuclear Materials

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“…Rods A and B were irradiated longer than 10 days after hole formation. Besides primary defects (e.g., debris fretting), each rod also had secondary defects, caused by hydride cracking along the interior of the tube wall [2][3][4][5].…”

Section: Fuel Rods With Clad-defectsmentioning

confidence: 99%

Characterization of fuel oxidation in rods with clad-holes

Verrall

Mouris

2005

Journal of Nuclear Materials

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“…The power-law dependence of the emission of 131 I and other fission products from the fuel assemblies into the coolant on the reactor power, the number of defective fuel assemblies on the temperature, and the specific energy content of fuel elements is confirmed for different types of reactors by data obtained by many authors, and the exponent in the equations of the (3) form varies from 2.5 to 5.5 [4][5][6][7]. The authors of one physical model link the emission of fission products from fuel assemblies to the size of the fuel granules, which is determined by the temperature.…”

mentioning

confidence: 99%

Behavior of Radioactive Iodine Isotopes in the Multiple Forced Circulation Loop in an RBMK Reactor

2005

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The flow of iodine, including 131 I, into the coolant water in a nuclear power plant with an RBMK-1000 reactor under normal operating conditions and during transient regimes is analyzed. It is shown that under normal operating conditions the specific activity of 131 I in the coolant is correlated with the iron concentration. During shutdown, its content increases by factors of 30-200. The emission of 131 I into the coolant can be decreased by factors of 10-15 and the degree of unsealing of fuel elements can be decreased if before shutdown the reactor is held for 2-5 days at 50% of the nominal power level. Recommendations are made for decreasing 131 I emissions into the atmosphere. The adoption of these recommendations at the Leningrad nuclear power plant has reduced the 131 I emissions into the atomsphere by a factor of 17.The iodine concentration in the water coolant is correlated with the change in the reactor power and increases sharply at the moment a reactor is shut down. The specific activity of 131 I in RBMK-1000 coolant is observed to increase by factors of 30-200 during the first few days after shutdown (Fig. 1, Table 1).The yield of the ith fission product from unsealed fuel assemblies is described by the relationwhere K is the coefficient of proportionality, which depends on the reactor power; Y i is the total yield on fissioning, arb. units; λ i is the decay constant of the radionuclide, sec -1 ; b is an exponent which assumes values from 0 to 1, depending on the degree of defectiveness of the fuel elements: • b = 1 for an equilibrium mechanism of emission of fission products (the constant characterizing the emission of a radionuclide into the coolant is somewhat less than the decay constant of the radionuclide; a constant or equilibrium content of fission products is established in the fuel); point defect; no correlations between emission and power; • b = 0.5 with a diffusion mechanism of emission (the emission constant into the coolant is much greater than the decay constant); slit-shaped defects; exponential power dependence of the emission of the radionuclides; • b = 0 in the absence of emission; no defects; the radionuclides enter the coolant as a result of surface contamination of the fuel elements by uranium; the emission of fission products is proportional to the reactor power [1]. Once stationary equilibrium is reached, the rate of entry of fission products into the loop becomes equal to the sum of their rates of decay and removal from the loop. The equilibrium specific activity of the ith radionuclide in the coolant can be expressed by the formula (2) A KY M i i i i = + λ λ λ 0 5 0 . ,

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Fuel Performance and Fission Product Release Studies for Defected Fuel Elements

Cited by 49 publications

References 33 publications

Thermodynamic considerations and prediction of the primary coolant activity of 99Tc

Thermodynamic considerations and prediction of the primary coolant activity of 99Tc

Characterization of fuel oxidation in rods with clad-holes

Behavior of Radioactive Iodine Isotopes in the Multiple Forced Circulation Loop in an RBMK Reactor

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