Calculation of plasma volume [BUG]

[mkovari]

From: 홍봉근 bghong@jbnu.ac.kr
Sent: Wednesday, March 6, 2024 10:25
To: Muldrew, Stuart stuart.muldrew@ukaea.uk
Subject: Inquiry on the calculation of plasma volume in PROCESS

Dear Dr. Muldrew,

Hello. I am Bong Guen HONG, a professor at Jeonbuk National University in KOREA. I also work for KFE (Korea Institute of Fusion Energy) to develop conceptual design of K-DEMO with systems analysis.
Recently I read your FED paper (conceptual design workflow for the STEP prototype power plant) with interest. Regarding the systems code, PROCESS, I would like to inform you of an error I found in old TETRA code during the K-DEMO scoping studies. I think the old TETRA is a basis of PROCESS. We also have developed our systems code based on old TETRA. The error occurred in the calculation of plasma volume; at the function fvol, where the equation, c2 = rc2 – R + a was wrong and it should be c2 = rc2 + R – a. You can find the wrong equation was written in page 3059 of FED 89 (2014). I hope you already fix this error in PROCESS.
...
Bong Guen HONG

The equation referred to is in the PROCESS physics paper:

According to @chris-ashe , the code error is found in the “fvol” method which is not run by PROCESS when calculating plasma volume. The “xvol” method is used instead.
@stuartmuldrew

There are other issues relating to plasma volume. Investigate.

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[cjwgriesel]

The calculation of the surface area of the plasma and the volume is wrong and there are inconsistencies in these calculations. This also affects the calculation of the volume and mass of the first wall armour thickness, first wall and blanket since the surface area of the plasma is used for these calculations. The original plasma surface area calculations were based on two circular arcs that crossed near the the diverters. A possible fix for this is to use the inner and outer surfaces of a rotated elliptical torus as the basis of the surface area calculation. This can also be then used for the components adjusting for the distance such as the first wall armour thickness, first wall blanket etc

[mkovari]

I have now implemented a new plasma volume formula which is used if icurr=8 - see #392.
@cjwgriesel @chris-ashe