Hello. I am trying to model a vessel with several nozzles. A couple of the nozzles are a case of d/D > 0.5, therefore WRC 297 will not work. This tells me I am to model (using cnodes at the troublesome nozzles, I believe) an anchor with stiffnesses in all diretions. We do not have an FEA program; so how am I to determine what the stiffnesses are?

Thanks for any and all assistance.

I guess you want to check that the local loadings in the vessel shell are OK. Try using sec 16 of EN 13445 [or App G Sec2.8 "alternative method" of PD5500 - it's roughly the same thing]. This more modern method has a wider range of applicability than WRC 107/297 /PD5500 Ap G, and you may well not have to allow for shell flexibilities in order to meet your criterea.
The other advantage of this method, is that it does not rely on graphs to use, so it is easily implemented by a computer. I generally use a MathCAD sheet to do the calcs.