DOE 2000. - Waste Isolation Pilot Plant - U.S. Department of Energy

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
The ultimate safety objective of the first, or primary layer of WIPP defense-in-depth is accident
prevention. The reduction of risk (as the product of frequency and consequence) to both workers and the
public from WIPP RH TRU waste handling and emplacement operations is primarily achieved by
reducing the frequency of occurrence of postulated abnormal events or accidents. The conservative
design of the facility’s SSCs, with operations conducted by trained/qualified personnel to the standards
set forth in approved procedures, provides the first layer. Specific preventative measures are identified in
Appendix C for each postulated deviation as identified in the HAZOPs, 4,5 and in Table 5.1-10 for each
deviation considered for quantitative accident analysis.
The occurrence frequency for each postulated deviation as identified in the HAZOPs, 4,5 and in
Table 5.1-10 for each deviation considered for quantitative accident analysis, is primarily derived from
the initiating event. To reduce the frequency of equipment failure, the facility design, fabrication, and
construction will be undertaken in accordance with applicable codes and standards, based on the design
classification of SSCs established in Chapter 4. Extensive pre-operational tests will be conducted to
verify that SSCs perform their design function. This will be followed by in-service and pre-operational
checks and inspections, and preventive maintenance and quality assurance programs.
The WIPP employs configuration management change control and modification retest to ensure quality
throughout facility life. For hazards associated with underground operations, a substantial array of
ground control planning and practices, support systems, instrumentation, monitoring, and evaluation
exist to reduce the frequency of potential Underground accidents. Technical Safety Requirement (TSR)
Administrative Controls (ACs) are derived in Chapter 6 and required in the WIPP TSR Document
(Attachment 1 to the SAR) to ensure that the high level of design is maintained throughout the facility
lifetime.
Additionally, as identified in the HAZOPs, 4,5 accident prevention for process inherent events, is achieved
administratively through the RH WAC 10 which restricts waste elements (such as the presence of
pyrophorics) which may be initiating events for accidents.
The following provide administrative controls to prevent the risk from postulated accidents from being
unacceptable: (1) RH WAC limits on the radionuclide and fissile content of each waste canister, (2)
waste canister integrity provisions ensure the robustness reflected in the waste canister accident release
analyses, and (3) criticality safety is a designed in-storage and handling configuration that ensures (in
conjunction with waste characteristics ) that active criticality control is not required.
Prevention of human error as an initiating event is achieved by the extensive training and qualification
programs, operational procedures, and conduct of operations programs. TSR ACs are derived in Chapter
6 and required in the WIPP TSR Document (Attachment 1 to the SAR) to ensure that these programs are
maintained, and operations continue to be conducted with highly qualified and trained personnel using
current approved procedures.
The second layer of defense-in-depth provides protection against anticipated and unlikely operational
events that might occur in spite of the protection afforded by the first layer of defense. The second
defense layer is characterized by detection and protection systems, and controls that: (1) indicate
component, system, or process performance degradation created by compromises of the first layer, and
(2) provide adequate mitigation and accommodation of the consequences of those operational accidents
which may occur.
5.1-19 January 22, 2003