Allow pin pitch in HexBlocks to fall back to pitch defined by a grid

[keckler]

The pin pitch is gotten by HexBlock.getPinPitch() by examining the clad and wire dimensions:

armi/armi/reactor/blocks.py

Lines 2420 to 2464 in 8768dec

	def getPinPitch(self, cold=False):
	"""
	Get the pin pitch in cm.
	Assumes that the pin pitch is defined entirely by contacting cladding tubes and wire wraps.
	Grid spacers not yet supported.
	.. impl:: Pin pitch within block is retrievable.
	:id: I_ARMI_BLOCK_DIMS6
	:implements: R_ARMI_BLOCK_DIMS
	This implementation requires that clad and wire Components are present.
	If not, an error is raised. If present, the pin pitch is calculated
	as the sum of the outer diameter of the clad and outer diameter of
	the wire.
	Parameters
	----------
	cold : boolean
	Determines whether the dimensions should be cold or hot
	Returns
	-------
	pinPitch : float
	pin pitch in cm
	"""
	try:
	clad = self.getComponent(Flags.CLAD)
	wire = self.getComponent(Flags.WIRE)
	except ValueError:
	raise ValueError(
	"Block {} has multiple clad and wire components,"
	" so pin pitch is not well-defined.".format(self)
	)
	if wire and clad:
	return clad.getDimension("od", cold=cold) + wire.getDimension(
	"od", cold=cold
	)
	else:
	raise ValueError(
	"Cannot get pin pitch in {} because it does not have a wire and a clad".format(
	self
	)
	)

This implicitly assumes that every HexGrid has a wire wrap. This is not universally true. It also assumes that there is only one type of clad and one type of wire in the block. This is certainly not universally true.

If we look at the parent class method, Block.getPinPitch() will actually check if the block has a grid defined, and it will use that to get the pin pitch within the block:

armi/armi/reactor/blocks.py

Lines 1270 to 1276 in 8768dec

	def getPinPitch(self, cold=False):
	"""
	Return sub-block pitch in blocks.
	This assumes the spatial grid is defined by unit steps
	"""
	return self.spatialGrid.pitch

This implementation on the parent class allows for the pin pitch to be gathered, independent of the assumptions that I outlined above. It just requires the user to define a grid in the blueprints.

I propose that the HexBlock subclass of getPinPitch() falls back to the parent method implementation if it fails to find the pin pitch using the current method. So basically just adding another try/except clause in there, and then pointing to super().getPinPitch(). This would allow for a lot more flexibility in geometric definition.

[jakehader]

Maybe related #1402?

[keckler]

Maybe related #1402?

Yeah, you're definitely correct, I forgot about that older ticket 😄

I don't think they are exactly the same issue, but probably resolving one will resolve them both.

[john-science]

Thanks, Chris! I see what you mean about the assumed wire wrap, and I like your solution.

I think it will take more time to write sufficient unit tests to prove the solution works, then to actually implement the solution. But that's fine, it still won't be that onerous.

[drewj-tp]

See also #252