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PREPARATION OF SAFETY & ENVIRONMENTAL DOCUMENTATION, AND THE APPROVAL PROCESS FOR TFTR DT OPERATIONS • Jerry D. Levine • June 24, 2014
TFTR Environmental Reviews • NEPA Reviews in 1975 (FES) and 1990-92 (EA). • FES: ≤ 1000 equivalent full power D-T pulses per year for 4 years, ~ 3 x 1021 total neutrons produced, 4 person-rem/year within 50 miles, 5.9 mrem/yr routine dose at the site boundary, routine release of 0.74 Ci/yr of tritium, worst case accident release of 1.3 kCi HTO. • EA: About 60 equivalent full power D-T pulses per year for 1-2 years, 1 x 1021 total neutrons produced, 17 person-rem/year within 50 miles, 8.3 mrem/yr routine dose at the site boundary, routine release of 500 Ci/yr of tritium, worst case accident release of 25 kCi HTO.
TFTR Environmental Reviews • Lengthy review and approval process for the EA. • Series of non-concurrent reviews by several levels within the DOE organization (Princeton Area Office; Chicago Operations Office; Office of Fusion Energy; Office of Energy Research; Office of Nuclear Safety; Office of General Counsel; and Office of Environment, Safety & Health). • EA then reviewed by New Jersey Department of Environmental Protection (NJDEP); comments resolved prior to DOE approval. • PPPL had two public meetings at the Laboratory to present the D-T Program and the results of the EA to interested members of the public. • Finding of No Significant Impact (FONSI) by DOE in January 1992.
TFTR Environmental Reviews • Several issues arose at the end of the EA/FONSI process: • Lack of sufficient inventory of large shipping containers for tritium; lead to proposal to construct and operate a Tritium Purification System to recycle tritium and reduce number of annual shipments by factor of 10. • Underestimate of tritium retention rate in torus vacuum vessel (& maximum releasable tritium from the torus) by factor of 2. • Supplemental Analysis (SA) to EA was prepared (beginning Feb. 1992) to address & document these issues. • SA reviewed by several DOE organizations starting July‘92. In January 1993, DOE concluded that based on the SA, the proposed changes to the TFTR D-T Program required no additional review under NEPA.
TFTR Safety Review and Approval • PSAR reviewed/approved by DOE in 1978 for authorization of substantial TFTR construction (i.e., pouring of concrete for the Test Cell which housed the tokamak). 1000 pages modeled on USNRC requirements for commercial nuclear power plants. One year to prepare. • ”Worst case accident" identified (non-mechanistically) as "massive destruction of the Test Cell" when the torus, neutral beams, and the tritium injection assemblies around the torus have their maximum tritium inventories. Maximum offsite dose (at site boundary, 125 meters from torus centerline) is 2.73 rem, < 5 rem design objective. • >300 (DOE) comments, 5 months to review/approve.
TFTR Safety Review and Approval • FSAR approved by DOE to support initial ("first plasma") TFTR operations in December 1982, following a three year preparation and review effort. Same size and format as PSAR. • Upgraded system descriptions, and refined potential accident scenarios and their consequences. • Using data from small onsite meteorological tower, maximum offsite dose due to "worst case accident" (the same accident included in the PSAR) was calculated to be 660 mrem. • ~300 DOE comments, but individual DOE organizations sent comments as they were generated, expediting the review and approval process.
TFTR Safety Review and ApprovalD-T Authorization Basis • Collection of documents that constituted the agreements between DOE and PPPL for safely operating the TFTR “nuclear facility” was known as the Authorization Basis, which was the basis for approval to run the D-T Program. • The TFTR D-T Program Authorization Basis included: • Hazard Classification: Category 3 nuclear facility, potential for only local consequences. Based on 50 kCi tritium inventory limit. • Updated FSAR: Started in 1990, 3 years to complete, >400 comments to resolve. “Worst case accident”: pipe break causing air ingress to the tritium storage beds, pyrophoric reaction between the air and the uranium tritide causing 25 kCi HTO to be released to the environment via the stack, resulting in an offsite dose of 140 mrem. • EA, FONSI, and SA: Includes "worst case beyond design basis accident”; same as updated FSAR but with failure of stack fans causing ground level release of 25 kCi &offsite dose of 390 mrem.
TFTR Safety Review and ApprovalD-T Authorization Basis • Authorization Basis (continued): • Technical Safety Requirements (TSRs): Conditions, safe boundaries, and management or administrative controls necessary to ensure the safe operation of a nuclear facility. For TFTR, these were: no more than 50 kCi of tritium onsite, and no more than 25 kCi in any system or component from which it could be released as a result of a credible accident analyzed in the FSAR. • DOE Safety Evaluation Report (SER): The DOE-prepared Safety Evaluation Report (SER) to document their review of the updated FSAR, and the reasons for their acceptance of his document. • Unreviewed Safety Question Determinations (USQDs): USQDs are performed to determine if proposed facility physical or operational changes, or new information regarding previous safety analyses, impacts the DOE approved Authorization Basis. >400 USQDs were done for TFTR without uncovering a USQ.
Radiological Releases & Offsite Doses During TFTR D-T Program and D&D (1994-2002) • Annual airborne releases of tritium (via stack): range of 62-260 Ci/yr, average was 131 Ci/yr. Limit was 500 Ci/yr. • Annual airborne releases of short-lived activated air products (Ar-41, N-13, N-16, Cl-40, S-37): range of 10-31 Ci/yr, average was 21 Ci/yr (during D-T experiments, 1994-97). • Annual liquid tritium releases (to sanitary sewer system via TFTR Liquid Effluent Collection Tanks): range of 0.071-0.951 Ci/yr, average was 0.322 Ci/yr. Limit was 1 Ci/yr. • Maximum Annual Individual Effective Dose Equivalent (at Site Boundary): range of 0.21-0.68 mrem/yr, average was 0.40 mrem/yr. Limit was 10 mrem/yr.
Site Specific Climatology Study • Projections of offsite consequences from airborne radiological releases can be very sensitive to atmospheric conditions in the vicinity of the release point. This is particularly important for a small site like PPPL which contains a number of large buildings surrounded by trees. Use of standard Gaussian diffusion models significantly overestimate offsite dose. • In July-Sept 1988, NOAA conducted a field measurement program to directly evaluate atmospheric diffusion conditions in the vicinity of PPPL. Four (4) tracer gas release points (exhaust stack & 3 ground level release points) were chosen to simulate potential pathways for release of effluents from the TFTR Facility. 98 receptors collected data within 1 km of TFTR. • Results were data set of source strength normalized concentrations (X/Qs). These proved that maximum projected offsite dose from the worst case accident would be a factor of 16 less than that calculated using the standard models.
Radiation Shielding Evaluation • Original design of the TFTR radiation shield system envisioned a peripheral “igloo” shield surrounding the tokamak device for D-T experiments. Caused much concern about machine access needs. • Through additional detailed analyses, radiation measurements during the extensive TFTR D-D experimental program (1983-93), and simulations using a neutron source, it was determined that the “igloo shield” was not required. • Some supplemental concrete shielding was added at the Test Cell walls. • Projected contribution to annual site boundary dose from neutron/gamma radiation during TFTR D-T experiments with as-built shielding was 1.6 mrem/yr. Actual contribution was 0.027-0.078 mrem/yr (0.05 mrem/yr avg).
Control of Operating Parameters for Safe D-T Operations • PPPL believed it prudent to establish a number of operating parameter requirements (OPRs) for D-T operations to ensure that the engineered detection and mitigation systems would be operating or operable when required. • OPRs were established for: area, stack and glovebox tritium monitors; room pressure differentials; minimum exhaust stack flow and stack negative pressure; fire detection and suppression systems; tritium cleanup systems; standby power system; tritium systems controls; meteorological tower instrumentation; torus and neutral beam vacuum alarms; interlocks for control of tritium gas transfers to injection volumes in the Test Cell; pressure, temperature and atmospheric constituents of tritium glove boxes and waste handling fume hood; Tritium Purification System; radiation monitors at the TFTR facility boundary; and tritium material control and accountability equipment.
Control of Operating Parameters for Safe D-T Operations • OPRs typically required operation or operability of these systems and components, or a particular range of parametrics, in order to enter a mode in which tritium transfer operations (TTOs) were allowed, to initiate specific TTOs, or to continue to conduct specific TTOs. • If a particular OPR condition wasn’t satisfied (e.g., a tritium monitor was inoperable or in alarm), actions to restore the condition (or, in some cases, to provide an approved substitute) must take place within a specified time interval before the relevant TTO must cease and/or actions to mitigate a potential problem must occur (e.g., initiate cleanup processing of a glove box). • Surveillance intervals for systems, components and parametrics were specified to ensure that OPRs were maintained. Failure to perform a surveillance requirement within 125% of the specified time interval constituted failure to satisfy the OPR.