Detailed descriptions are provided for safety-class and safety-significant SSCs and SACs
in Chapter 4 of the DSA because of the importance of their safety functions. Descriptions
result in the definition of functional requirements and associated performance criteria used
to derive TSRs. TSRs are safety controls developed in accordance with the precepts of 10
CFR 830. TSR and SSC commitments encompass the following:
Technical safety requirements. TSRs comprise: (1) safety limits (SLs); (2)
operational limits consisting of limiting control settings (LCSs) and limiting conditions
for operation (LCOs) and associated surveillance requirements (SRs); (3) ACs, (4)
SACs, (5)use and application provisions, (6) design features, and (7) Bases Appendix.
Based on the results of hazard and accident ana lysis TSRs are designated for: (1)
safety-class SSCs and controls established on the basis of application of the Evaluation
Guideline; (2) safety-significant SSCs; (3) defense in depth in accordance with the
screening criteria of DOE G 423.1-1; and (4) safety management programs for defense
in depth or worker safety. The Bases Appendix provides the linkage to the DSA.
It is important to develop TSRs judiciously. TSRs should not be used as a vehicle to
cover the many procedural and programmatic controls inherent in any operation.
Excessive use of TSR limits to manage operations will result in distortion of the
regulatory structure DOE is attempting to develop and will dilute the emphasis
intended for the most critical controls.
SLs should be limited in number and designated with caution. In accordance with
Table 4 of Appendix A to Subpart B of 10 CFR 830, SLs are generally reserved for
limits on process variables associated with those safety-class physical barriers,
generally passive, that are necessary for the intended facility function and that are
required to guard against the uncontrolled release of radioactive materials. The
associated operating limits apply to active SSCs that prevent exceeding SLs. The only
candidates for SLs should be safety-class SSCs and any non-SSC controls established
on the basis of the application of the Evaluation Guideline. Nuclear industry precedent
is that only a limited subset of safety-class SSCs, if any, require definition of
associated SLs, which are intended to pre vent significant accidents as opposed to
mitigating their effects.
TSRs assigned for defense in depth or safety-significant SSCs do not have SLs and are
not required to use operational limits (i.e., LCSs, LCOs). They should, however,
receive coverage in the administrative control section of TSRs as a minimum.
Judgment should be used to determine what controls warrant use of operational limits.
When TSR administrative controls are used for purposes other than generic coverage
of safety management programs (e.g., SAC), descriptions should be sufficiently
detailed that a basic understanding is provided of what is controlled and why. Beyond
safety-significant SSCs designated for worker safety and their associated TSR
coverage, additional worker safety issues should be covered in TSRs only by
administrative controls on overall safety management programs.
Safety-class structures, systems, and components. The Rule defines safety-class
designation for SSCs that are established on the basis of application of the Evaluation
Guidelines. This designation carries with it the most stringent requirements (e.g.,
enhanced inspection, testing and maintenance, and special instrumentation and