ML20209G035
| ML20209G035 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 05/31/1999 |
| From: | Chelliah E NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20209F261 | List: |
| References | |
| GL-88-20, NUDOCS 9907160221 | |
| Download: ML20209G035 (6) | |
Text
TECHNICAL EVALUATION REPORT ON THE REVIEW OF THE THREE MILE ISLAND NUCLEAR STATION, UNIT 1, INDIVIDUAL PLANT EXAMINATION FOR EXTERNAL EVENTS (IPEEE)
SUBMITTAL ON HIGH WINDS, FLOODS, AND OTHER EXTERNAL EVENTS (HFO)
ERULAPPA S. CHELLIAH PRAB/DRAA/RES/USNRC May 1999
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TECHNICAL EVALUATION REPORT ON THE REVIEW OF THE THREE MILE ISLAND NUCLEAR STATION, UNIT 1, INDIVIDUAL PLANT EXAMINATION FOR EXTERNAL EVENTS (IPEEE)
SUBMITTAL ON HIGH WINDS, FLOODS, AND OTHER EXTERNAL EVENTS (HFO)
===1.
Background===
Three Mile Island Nuclear Station, Unit 1 (TMI-1) is a Babcock and Wilcox-designed pressurized water reactor (PWR) plant located on Three Mile Island in the Susquehanna River, in eastern Pennsylvania. Harrisburg is the largest nearby city. The U.S. Atomic Energy Commission (USAEC) issued an operating license to the TMI 1 facility on April 19,1974, and the plant began commercial operation on September 2,1974.~ Since the Standard Review Plan (SRP) and other regulatory guides (RGs) were completed for additional regulations at a later time by the U.S. Nuclear Regulatory Commission (NRC), the TMI-1 facility was categorized as a i
systematic evaluation program (SEP) plant in order to address specific safety issues and site-related issues. The licensee's IPEEE process made use of the requirements of staff-issued Generic Letter (GL) 88-20, Supplement 4, along with the proceqiural guidance of the NUREG-1407 report in developing its response to information on high winds, floods, and other external events (HFO) related severe accidents. The licensee's IPEEE used the progressive screening approach described in NUREG-1407 and focused on identifying design and operational vulnerabilities due to postulated HFO events. The licensee's evaluation of HFO events also considered current plant design (Final Safety Analysis Report, Amendment 11) and the updated HFO-related historical databases that were developed since the OL of the TMI-1 facility.
2.
High Winds and Tomados The licensee evaluated the current plant design and operational provisions against high winds and tornados in the vicinity of the TMI-1 site and determined that it was in conformance with the design-related regulatory guides (e.g., RG 1.117) that were used as part of the original licensing process. The high winds evaluation included a review of historical high winds and tornado data for the period 1917 thru 1969 (a total of 52 years), an analysis of tornado data characterization by L. A. Twisdale (documented in Reference 3 of Section 5.1 of the IPEEE), an assessment of tornado missiles applicability by L A. Twisdale (documented in Reference 6 of Section 5.1 cf the IPEEE), and an evaluation of the ex-plant walk-down findings of tomado-exposed structures and components. The design basis tornado speed for the TMINS-1 facility is 360 miles per hour. The IPEEE noted that the borated water storage tank (BWST) and the condensate storage tank (CST) are located outside the plant safety related buildings and are susceptible to high intensity tornado wind loads and tomado missile loads. The licensee performed a simplified probabilistic risk analysis (PRA) using the high intensity tornado data and evaluated the susceptibility of the outdoor structures to tornado wind loads and tornado missiles (e.g., loss of offsite power, the BWST failure, and the CST failure). The core damage frequency (CDF) estimates for tornado wind loads and tornado missile loads were computed accordingly, and the total tornado-induced CDF was estimated to be about 7.36E-7 per year.
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This estimate was found to be lower than the NUREG-1407 screening criteria of 1E 6 per year.
This estimate was dominated by tornado missiles, and the tornado missile-induced CDF was found to be 4.3E 7 per year. The licensee did not identify any tornado-related vulnerabilities.
The licensee did.not identify any plant improvements to combat against severe tornados (higher than the original design basis). The staff finds that the licensee's high winds and tornado evaluation is consistent with the guidance provided in Section 5.2 of NUREG-1407.
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External Floods The licensee evaluated the current plant design and operational provisions against Susquehanna River floods and the probable maximum precipitation (PMP) flood and determined that it was in conformance with the design-related RGs'(e.g., RGs 1.59'and 1.102) i that were used as part of the originallicensing process. The external flood evaluation included a review of historical river flood levels in the site area (including the updated river flood data from the OL date of 1974 to 1994), an analysis using the Department of Commerce (DOC) data on rainfall to evaluate the flood exceedence frequency, an evaluation of potential upstream dam l
failures, and an evaluation of potential flooding of the Susquehanna river from debris blockage
. events. The design basis flood level for the TMI-1 facility is elevation 310 feet. Flooding of the site is prevented by protective dykes that have been built around the facility. The CDF l
estimates of sequences due to three postulated flood levels (below 305 feet,305 to 310 feet, j
and above 310 feet) were computed, and the total flood-induced CDF was found to be about 8.1E-5 per year. This estimate was dominated by the river flood exceeding the 310-foot level, which was estimated to be 6.4E 5 per year. The licensee did not find any flood-related vulnerabilities. However, the licensee identified plant improvements to combat against severe river floods (a flood level higher than the original design basis flo:>d level). Flood-related plant improvements are discussed in Section 7.0 of this technical evaluation report. The staff finds that the licensee's external flood evaluation is consistent with the guidance provided in Section 5.2 of NUREG 1407.
4.
Transportation and Nearby Facility Events 4.1 Chemical Release Events The licensee " evaluated the main control room (MCR) design and operational provisions against postulated chemical release events (onsite and offsite chemical releases) within five miles of the site boundary. The chemical release events evaluation included a review of the data on storage problems associated with onsite chemicals and offsite chemicals (primarily railroad-related chemical spills documented by the Department of Transportation and the safety management reports developed by Conrail). The original MCR design basis for chemical release protection was based en t riteria documented in RGs 1.78,1.91 and 1.95. As part of the IPEEE, the licensee li, led applicable chemical sources (a total of 18 sources) shipped by the Con Ran system and evaluated the chemical spill events in the vicinity of the site. The IPEEE estimated the hazard frequency of the above chemicals using the methods documented in the Pickard, Lowe,
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and Garrick (PLG)-0370 report. The hazard frequency of all applicable chemicals was estimated to be about 8.1E-6 per year. Based on a probabilistic credit for the current MCR isolation features and recoverv of MCR operations followed by incapacitation of all
4 five operctors in the MCR due to a postulated chemical release event, the IPEEE estimated a chemical release event induced CDF of about 1.6E-7 per year. This estimate was found to be lower than the NUREG-1407 screening crlteria of 1E 6 per year. The licensee did not identify any plant operational vulnerability due to postulated chemical release events. The staff finds that the licensee's chemical release events evaluation is consistent with the guidance provided in Section 5.2 of NUREG-1407.
4.2 Air Transportation Events The licensee evaluated the current building design features (e.g., turbine building) and plant operational provisions against three groups of postulated aircraft crash events (very large aircraft crashes, large aircraft crashes, and small aircraft crashes) within five miles of the site boundary. The air transportation hazard evaluation included a detailed evaluation of historical data on aircraft crashes (primarily documented in the reports developed by the National Transportation and Safety Board and the Annual Reports ieveloped by the Department of Transportation for years 1978 thru 1987), general aviation data on the total number of aircraft landings and departures for all airports, and the data for the projected number of landings and departures for the Harrisburg Airport
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(estimated by the Harrisburg Airport Authority as part of its long term aviation planning).
The original building design basis for postulated aircraft impact included consideration of more than two-foot thick concrete walls and roofs for all safety related buildings at the TMI 1 facility. As part of the IPEEE, the licensee identified applicable aircraft and characterized them into three groups (very large aircran, large aircraft, and small aircraft) and estimated a crash event frequency for the three aircrah groups based on the evaluated crash events data, general avionics data, and the projected airport growth data.
The crash events frequency estimates were found to be about 1.7E-8 per year,2.8E-6 per year, and 2E-4 per year for very large aircraft, large aircraft, and small aircraft respectively. The IPEEE also estimated aircraft crash events-induced CDFs of about 1.7E-8 per year,3.6E-7 per year, and 2E 8 per year for very largo aircraft, large aircraft, and small aircraft, respectively. The overall CDF estimate of 4E-7 per year for all three aircraft groups was found to be lower than the NUREG 1407 screening criteria of 1E-6 per year. The overall aircraft crash events induced CDF was dominated by large aircraft crashes. The licensee did not identify any plant design or operational vulnerability due to postulated aircraft crash events. The staff finds that the licensee's aircraft crash events evaluation is consistent with the guidance provided in Section 5.2 of NUREG 1407.
4.3 Highway Transportation Events The licensee also assessed other events involving transpoitation hazards, including those on highways within five miles of the site, and found that these events would have an insignificant impact on safety-related buildings.
4.4 Other Transportation Events The licensee indicated that no Susquehanna River barges that carry a significant quantity of explosives were found within five miles of the site boundary. The Susquehanna River is considered to be too shallow for transportation of medium to large barges.
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5 5.
Other External Events 5.1
- Postulated Rupture of Pipelines Carrying Combustible Gas and/or Flammable Liquids The licensee indicated that no new pipelines (buried or exposed) that carry a significant quantity of combustible gas or flammabable liquid were found near the TMI-1 site.
NUREG-1407, in Section 2.12, notes that all licensees should confirm that no plant-unique external events known to the licensee at the time of their IPEEE submittal with potential severe accident vulnerability are being excluded from their IPEEE. The licensee for the TMI-1 facility has stated in Section 2.2 of the IPEEE submittal that no other plant unique -
external events, including lightning strike events, and associated vulnerabilities have been i
identified.
6.
Generic Safe y issues (GSis) 6.1 GSI 103, " Design for Probable Maximum Precipitation (PMP)"
The licensee evaluated potential safety problems to be addressed as part of GL 89-22, dated October 19,1989. These problems involve the adequacy of building roofs to withstand the loads imposed during postulated local high intensity rainfall in very short
- time intervals, and the adequacy of plant site drainage system during local high intensity
' rainfall. The licensee's evaluation and assessment of the GL 89-22-requested response and action are documented in the TMI-1 engineering calculations (Refer to TMINS-1-90-9108) which are currently maintained at the TMI-1 technical center. It is the staff's understanding that the updated PMP calculations made use of the updated rainfall data documented in applicable hydro meteorological reports (HMRs) (e.g., HMR 52 i
published in' August 1982 by the NOAA/ Department of Commerce) for the TMi-1 site. The licenses concluded that the new PMP data was not a concern for TMI-1. The staff finds
_ that the licensee's GSI-103 evaluation is consistent with the guidance provided in Section 6.2.2.3 of NUREG-1407.
6.2 GSI 156, " Systematic Evaluation Program (SEP)"
There are four SEP-related issues related to the HFO aspects of the TMI-1 IPEEE The licensee's IPEEE submittal contains information addressing the following SEP-related site issues: (1) site hydrology and ability to withstand floods (Section 5.2.3), (2) industrial hazards (Section 5.3.1), (3) tomado missiles (Section 5.1.5), and (4) severe weather effects on structures (Section 5.1). The IPEEE also evaluated HFO-related design and operational vulnerabilities associated with these issues. No potential vulnerabilities were found, and no plant improvements were identified.
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6.3 GSI 172," Multiple System Responses Program (MSRP)"
1 There is one MSRP issue related to the HFO area which is titled, " Effects of Fiooding l
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6 and/or Moisture intrusion on Non-safety Related and Safety Related Equipment." The effects of flooding on safety related equipment and non safety related equipment were addressed in the licensee's IPEEE submittal (Sections 5.2.3 and 5.2.4). The IPEEE also evaluated HFO related design and operational vulnerabilities for this issue. No potential vulnerabilities were found, and no plant improvements also were identified.
' 7.
Unique Plant Features, Potential Vulnerabilities, and improvements TMI-1 is located on an island in the Susq ehanna River, and the site is designed with dykes j
around the plant to protect against Susquehanna River floods (up to 310 foot level). The external portion of the IPEEE evaluated all applicable river floods including the PMP floods and their impact on plant safety. The licensee did not define a potential HFO-related vulnerability for i
TMI-1, and no extemal flood-induced vulnerabilities were identified. The IPEEE Identified flood-1 related plant improvements to mitigate the consequences of higher river flood levels (i.e., beyond the design basis flood level of 310 feet).~ However, the IPEEE submittal did not specify what equipment would be installed. Thw license also planned to develop flood mitigating guidelines in l
the event of severe flooding of the Susquehanna River. The IPEEE did not identify other plant improvements for HFO events.
8.
Conclusions Noteworthy strengths in the IPEEE submittal in the HFO area include detailed probabilistic modeling of chemical release events and aircraft crash events in the vicinity of the TMI-1 facility.
Other strengths of the IPEEE include its overall clarity and completeness. The origina! design of the TMl-1 facility along with recent plant design changes were evaluated with a clear description of the probabilistic analysis methods and results. No weaknesses in HFO examination methods or associated documentation were found.
The IPEEE provided plant specific information to address the resolution of GSI-103. The IPEEE submittal also provided information to address the resolution of four GSI 156 (Systematic Evaluation Program) issues and one GSI 172 (Multiple System Response Program) issue. No plant vulnerabilities were identified for HFO events, but some improvements were planned as discussed above, it is concluded that the licensee's TMI-1 IPEEE submittal for the HFO events meets the intent of GL 88 20, Supplement 4, including the procedural requirements of NUREG-1407.
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