\subsection{Changes from CDR}

Measurements of titanium samples at CANFRANC (and elsewhere, for LUX) show inconsistency in achieving radiopurities for U,Th in the 100 $\mu$Bq/kg range; as a result our confidence has waned and we have elected to build a stainless steel vessel, using material in the 1-2 mBq/kg range, of 6 cm larger radius, lining the inside with 6 cm radiopure copper shielding. This saves considerable time and money in building the vessel, as more vendors become available, since the special fabrication facilities and certifications for Ti fabrication are not needed. The extra weight of the copper supported by the vessel does not require significant extra thickness in flanges or shells.

The vessel design paramaters are shown in table \ref{pv_params}

\begin{tabular}{|p{ 8cm}|c|c|}\hline
		Maximum Operating Pressure (MOP) &14&bargauge \\ \hline
		Maximum Allowable Pressure (MAWP) 110\%MOP&15.4&barg\\ \hline
		Maximum Allowable External Pressure (MOPE)&1.5&barg\\ \hline
		Vessel Material Stainless Steel Alloy &304L,316L&&
		Vessel Inner Diameter&122&cm\\ \hline
		Vessel Wall thickness&10&mm \\ \hline
		Torispheric Head thickness &10&mm\\ \hline
		Flange Outer Diameter&133&cm
		
		Flange Thickness&30&mm\\ \hline
		Bolt Material&Inconel 718&&\\ \hline
		Bolt Diameter and pitch&M14-1.0(FT)&\\ \hline
		Number of bolts per flange&120&&\\ \hline
		
		 \hline
		 
	\end{tabular}












\subsection{Vessel Contracting process}

The pressure vessel design, fabrication and certification will be done to ASME pressure vessel Code, section VIII division 2, as much as is possible. Any exceptions must be fully reviewed and approved by an appropriate technical committee.

The vessel design,contracting and fabrication process (individual responsibilities) is defined in ASME code and is as follows:

1. We, collaboration write a User's Design Specification for the Vessel which includes all ( user required) dimensions, media, conditions, loads, load history, etc. that the vessel will be subject to. ASME PV code sec VIII div. 2, par. 2.2.2 is a specification for what needs to be included, and allows for additional requirements. We will add additional conditions that allow us to assure quality in particular, for radiopurity, from material purchase, through all cleaning, joint preparation, welding, pressure testing step. Normally the Manufacturer performs (or contracts) the calculations to determine wall, flange and nozzle thicknesses, however by agreement, we can perform these. However, the Manufacturer is still responsible for the pressure retaining integrity of the Vessel (par. 2.3.1.1), and may well want to to do their own.

2. The User's Design Specification must then be certified by an Independent Certification Authority to assure that the vessel is fully specified. The individual(s) in charge of certifying the Users Design Specification must be licenced professional Engineers 

3. The Manufacturer must provide a Manufacturer's Design Report, which includes final as-built drawings, design calculations, analyses and all material and welder certifications, inspection, NDE reports and test reports. This Manufacturer's Design Report must be certified by a Certifying Authority. So, even if the manufacturer, by agreement accepts our calculations, they must be Certified. 

3. A Certified Inspector must be hired to inspect all stages of the fabrication, and certify the vessel is being built in accordance with Specification; we will also perform our own inspections of the fabrication process. The Certification firm can provide the Inspector.

4. The Manufacturer must be certified to perform all the operations specified in the Specification. They must have a certified Quality Assurance Program in place that can track progress and demonstrate compliance with the requirements for fabrication.

Due to the nature of the vessel, we are taking a much stronger hand in the design and fabrication than is usually done (this will be made clear in the user's Design Specification), however this does not absolve Manufacturer of their responsibilities, so they may well elect to do all their own calcs.