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SIMULATION OF CORROSION PRODUCT ACTIVITY IN PRIMARY COOLANT OF A TYPICAL PWR UNDR LINEARLY AND NON-LINEARLY RISING CORROSION RATE AND FLOW RATE TRANSIENTS.

Rafique, Muhammad (2005) SIMULATION OF CORROSION PRODUCT ACTIVITY IN PRIMARY COOLANT OF A TYPICAL PWR UNDR LINEARLY AND NON-LINEARLY RISING CORROSION RATE AND FLOW RATE TRANSIENTS. PhD thesis, Pakistan Institute of Engineering & Applied Sciences, Islamabad.

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Abstract

In comparison with emerging nuclear power systems, the Pressurized Water Reactors (PWRs) have many times higher post shutdown radiation levels, mainly due to the corrosion product activity (CPA), prolonging the maintenance resulting in substantial economic penalties. The advent of high-power fuel with higher potential for crud deposition has aggravated this problem further. Recent studies have also identified corrosion cracking, corrosion fatigue, stress corrosion, and erosion-corrosion as major safety concerns in these systems requiring reliable estimates of corrosion products in both normal as well as transient conditions. In this work, a detailed methodology has been developed for modeling and simulation of corrosion product activity in primary loops of typical PWRs. This is based on system of differential equations governing the kinetics of dominant CPAs throughout the primary loop. In view of experimentally observed variation of corrosion rates with plant aging, temperature and pressure, models have been developed for both linearly and non-linearly rising corrosion rates. Also flow rate perturbation has been added in order to take in to account various transients. This methodology has been implemented in a fortran-77 based computer program CPAIR-RC has been found in good agreement with the corresponding experimental data. Similarly, the value of the activity ratios for 58Co to 60Co calculated by CPAIR-RC program compare well with the corresponding results found by using CRUDSIM/MIT code. The linearly rising corrosion rates tend to smear-out the effect of flow rate perturbations on the specific activity of the primary coolant. Also considerable changes have been observed on specific activity in reactor transients when linearly rising corrosion rate model is replaced with non-linearly rising model. The saturation values of specific activities due to 24Na, 59Mn, 59Fe, 58Co, 60Co and 99Mo have been found to depend on changes in flow rate as well as on the corrosion rate. The time required to reach saturation level has been found to depend strongly on flow rates and efficiencies of filters, dematerializing units etc. to remove CPAs.

Item Type:Thesis (PhD)
Uncontrolled Keywords:pressurized water reactors (pwrs), corrosion product activity, corrosion rates, coolant
Subjects:Physical Sciences (f) > Mathematics(f5) > Applied Mathematics(f51)
ID Code:523
Deposited By:Mr. Muhammad Asif
Deposited On:28 Sep 2006
Last Modified:04 Oct 2007 21:01

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