The Tech Specs don’t include the basis used to explain and justify them. Those explanations are contained in the Tech Specs Bases. That raises a question: what is the foundational purpose of the Tech Specs?
The TS Bases reveals this purpose. By doing so, it sheds light on the NRC’s primary focus for protecting the public health and safety:
GDC 10 (Ref. 1) requires that specified acceptable fuel design limits are not exceeded during steady state operation, normal operational transients, and anticipated operational occurrences (AOOs).
The NRC’s mission is to keep the public safe by ensuring it isn’t exposed to excessive radiation. The source of danger to the public is the radioactive nuclear fuel that lies within the reactor core.
The restrictions of this SL [“safety limit” — JL] prevent overheating of the fuel and cladding, as well as possible cladding perforation, that would result in the release of fission products to the reactor coolant.
Nuclear fuel (refined uranium-dioxide powder) is formed into small pellets. Those pellets are loaded into a long metallic tube similar to how a cluster of BBs is loaded into the barrel of a BB gun. The long tube assembly is called a fuel rod and is (usually) made of a corrosion-resistant zirconium alloy. The alloy, when shaped into a tube, is called a cladding. The fuel rod cladding has a very high melting point and resists degradation when exposed to the extreme heat and radiation levels produced during the fission reaction.
While undergoing the fission process, the fuel breaks down over time into other elements that are highly radioactive. These elements are called fission products. The fission products accumulate inside the fuel rods. Or, to put it another way, the fuel rods contain or trap the fission products. The cladding forms a boundary between the fuel and the reactor coolant. The nuclear fuel produces heat during the fission process, which is its designed purpose. The heat is transferred from the fuel into the cladding, and the reactor coolant’s temperature rises as it extracts this heat while circulating around the fuel rods. The heated coolant is pumped away from the core and then converted to steam that drives an electric turbine that powers the grid.
If the cladding develops holes, the extremely radioactive fission products will escape the fuel rods and disperse into the coolant. Or, if the rods overheat (because the coolant flow has stopped or diminished), they can turn into molten metal and melt through the reactor vessel. This is a nightmare scenario. At that point, two of three primary containment barriers have failed: the cladding and the reactor vessel and its associated piping. All that’s left standing between the public and the radioactive fuel and fission products is the Containment building.
 Westinghouse, Standard Technical Specifications, Volume 2: Bases, Rev. 4, released as NUREG-1431 (Washington, D.C.: Office of Nuclear Reactor Regulation, 2012), Section B 2.1.1, “Reactor Core Background.”
 The melting point for Zircaloy-2 is 3360 degrees fahrenheit and similar for other zirconium alloys. See C.L. Whitmarsh, “Review of Zircaloy-2 and Zircaloy-4 Properties Relevant to N.S. Savannah Reactor Design” (Oak Ridge, Tennessee: Oak Ridge National Laboratory, 1963). Link: http://web.ornl.gov/info/reports/1962/3445605716311.pdf. See also: http://www.osti.gov/scitech/biblio/4827123.
 It is thought that, at Fukushima, even the Containment building has been breached. The fuel melted through the cladding and through the reactor, and the Containment building has holes in it which makes it possible for contaminated water to leak into the ocean. All of this because the emergency diesel generators were destroyed by the tsunami, meaning that there was no electricity available to power the pumps which were supposed to circulate coolant through the core. Link: http://www.pbs.org/newshour/bb/inside-fukushima/