Nuclear Wastes Technologies for Separations and Transmutation (1996) / Chapter Skim
Currently Skimming:
I HEALTH AND SAFETY
I HEALTH AND SAFETY
Pages 383-412
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 383... ...
The question of likelihood is often a matter needing detailed analysis, since, in many instances, there are too few data to assign statistically based frequencies. The most common approach is to develop frequencies and probabilities based on all available evidence, including detailed logic models that decompose the facility into components for which there are data and increased knowledge, and to do so in such a way as to recognize the uncertainties involved.
|
From page 384... ...
The approach taken is to develop risk and safety summaries of each of the radioactive waste treatment concepts based on studies and reports made available to the Committee on Separations and Transmutation Systems. These summaries are at the end of this appendix.
|
From page 385... ...
The second group of issues lists the selected design features in terms of applicability to waste objectives, unique risk reduction features, unique safety concerns, and major sources of uncertainties. These issues highlight the ability of the technology to address the risks associates!
|
From page 386... ...
The potential for radiation exposure from mining and milling operations is estimated to be approximately 50% of the total exposure from the existing nuclear fires cycle, and the waste management exposure potential is about I% of the total exposure potential. Comparison of the risk implications of selected design features of the various S&T concepts is difficult primarily because of the differences of the specific objectives of the individual technologies.
|
From page 387... ...
The processing rates will not be sufficiently rapid to mitigate the most severe shutdown heating transient on loss of normal cooling. However, the short delay times between transmutation and separation wall result in much higher activities of short-lived fission products in fuel processing equipment.
|
From page 388... ...
The ATW approach to the treatment of radioactive waste is handicapped by a lack of experience and therefore knowledge about safety issues. No significant and quantitative risk assessments have been made on any phase of the ATW concept, much less the integrated system.
|
From page 389... ...
However, it has not yet been demonstrated at a scale required to support an ALMR fuel cycle. While ALMR/DiR technology and its associated safety assessment are much further developed than for accelerator-based concepts, uncertainties remain on the safety of waste reduction processes using fast reactors.
|
From page 390... ...
Also, the ejects of burn-up reactivity swings on the operations of such a reactor remain to be evaluated, together with the power distribution issues characteristic of high thermal-flux systems. Even though no significant safety studies have been performed, the proponents of the PBR believe that many key technologies have been demonstrated by the experience of the HTGRs, despite the fact that power densities for the current graphite reactors are more than two orders of magnitude lower than those proposed for the PBR.
|
From page 391... ...
On the other hancI, much more is known about the operations involved in the short term resulting in greater confidence in the risk results. Taking a purely state-of-knowledge approach to risk and considering each phase of operation as mutually exclusive, the following qualitative risk rankings are offered within each phase in order of increasing risk: · For transmutation, the lowest to highest risk alternatives appear to be light-water reactors, fast reactors, and accelerators.
|
From page 392... ...
RISK AND SAFETY SUMMARIES: RADIOACTIVE WASTE TREATMENT CONCEPTS Concept: Accelerator Transmutation of Radioactive Waste (ATW)
|
From page 393... ...
Processing rates probably will not be sufficiently rapid to mitigate the most severe shutdown heating transient with loss of normal cooling. · Large reactivity swings are expected in going from cold shutdown to hot operating conditions.
|
From page 394... ...
(2) Unique Risk-Reduction Features Reduced source term and decay-heat load as a result of on-line fission- product removal.
|
From page 395... ...
(2) Unique Risk-Reduction Features Concept advocates a mix of facilities that would minimize geologic storage requirements.
|
From page 396... ...
(3) [unique Safety Concerns Decay heat is a concern even with a rapid removal of the proton source.
|
From page 397... ...
(~3) Unique Safety Concerns · Activation of replaceable components may increase short-term storage requirements.
|
From page 398... ...
- While EBR-~l and FFTF experience have been favorable, there have been difficulties with some fast reactors. Specific examples are filed damage in the Fermi reactor and the EBR-l, cracking of primary system components in a U.K.
|
From page 399... ...
(4) Uncertainties · Little experience with liquid-metal fast reactors on a commercial scale.
|
From page 400... ...
,(2) Unique Risk-Reduction Features Processing delayed until the iodine and xenon source terms have decayed, thus greatly reducing major contributors to thyroid dose and external dose.
|
From page 401... ...
(3) Experience Demonstrating Feasibility Considerable commercial operating experience with existing designs that use slightly enriched uranium.
|
From page 402... ...
(2) Quantitative Safety Assessments Risk assessments available for PUREX process.
|
From page 403... ...
(~2) Unique Ri~sk-RecInction Features · Thermal neutron spectrum is the most effective transmutor for many fission products, thus reducing storage requirements for some long-lived isotopes.
|
From page 404... ...
(~3) Unique Safety Concerns · The effects of burn-up reactivity swings on the operations of such a reactor remain to be evaluated, together with the power distribution issues characteristic of high-thermal-flux systems.
|
From page 405... ...
Applicability to Waste Objectives ~ Burn plutonium, MAs, and long-lived fission products. · Store cesium and strontium in an monitored retrievable storage, recycle uranium in EWRs, and recycle unburned plutonium into EWRs as MOX Mel.
|
From page 406... ...
(2) Quantitative Safety Assessments Estimated risk wait be dependent on evaluation of individual reactor types.
|
From page 407... ...
(2) Unique Risk-Reduction Features · Proponents claim CURE with transmutation substantially reduces repository risks for both intrusive and leakage scenarios.
|
From page 408... ...
{2) Unique Risk-Reduction Features · Concept advocates a mix of facilities that would minimize geologic storage requirements.
|
From page 409... ...
(3) Unique Safety Concerns · No transmutation.
|
From page 410... ...
Unique Safety Concerns Magnitude of geologic storage requirements is a prime motivation for this evaluation.
|
From page 411... ...
1992. Impact of Actinide Recycle on Nuclear Fuel Cycle Health Risks.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.