Section C$.$ Corrosion Mass Change and Generalized Rate Laws

$20$ Marks

You are part of a refurbishment team evaluating C$89,$ a new material, for use in the IX column. In this case, the material is to be used in the cooling circuit to maintain the IX resins at Filtered brackish water is used for a once$-$through cooling fluid. The corrosion rate was measured using up to $5$ coupons at $25$ time intervals in simulated non$-$radioactive solutions. The composition of the solution was varied over $+-2$ of the average composition taken over the lifetimes of all the primary side IX columns used in all the company PWR and PHWR reactors. A linear regression analysis of weight$-$change versus time was aggregated to obtain the best correlation. The regression analysis over $100$ points produced regression constants of:

$0\mathrm{.}21+-0\mathrm{.}06m\frac{g}{c}\frac{m^2}{h^{\frac{1}{2}}}$

$0\mathrm{.}08+-0\mathrm{.}10m\frac{g}{c}{m}^2$

with a $95\%$ confidence interval.

$41.$ write the corrosion rate equation using the information provided.

$1$ Mark

$2.$ Assume the rate is constant after $1a$ of exposure. The oxide layer remains stable and controls the corrosion rate. What is the actual $($instantaneous$)$ corrosion rate at $1$ a$?$

$2$ Marks

A$3.$ What is the total mass loss at $1a?$ Why is this corrosion rate different than the one you determined in part $2?$

$1+4$ Marks

A$4.$ What thickness of material needed for $10$ a of operation before ductile failure of the dryer? Show your work to demonstrate your corrosion allowance is adequate $($over$/$under estimate is acceptable$)$ and show why the rate you used is the most appropriate.

Do not forget to document the critical assumptions necessary and the impact of the assumption $($e$.$g$.,$ it leads to a large error$)$ on the estimate.

$10$ Marks

A$5.4)$ To increase safety, also determine the thickness needed to meet a $1\mathrm{.}5$ safety factor.

$2$ Marks