ML20248C545
| ML20248C545 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/02/1995 |
| From: | NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| Shared Package | |
| ML20248C400 | List: |
| References | |
| GL-88-20, NUDOCS 9806020184 | |
| Download: ML20248C545 (15) | |
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. l MILLSTONE UNIT 3 STAFF EVALUATION REPORT ON IPEEE REVIEW 1.0 BACKGRODMD Generic Letter 88-20, Supplement 4 (with enclosed NUREG-1407,
" Procedural and Submittal Guidance," Ref. 1) was issued by the NRC on June 28, 1991, which requested that all licensees perform individual plant examination of external events (IPEEE) to identify plant-specific vulnerabilities, if any, to severe accidents and report the results together with any licensee-determined improvements and corrective actions to the commission.
Northeast Utilities System, the licensee operating Millstone Unit 3 (Millstone 3), submitted a summary report to the NRC in August 1990, entitled " Millstone Unit 3 Individual Plant Examination (IPE) for Severe Accident Vulnerabilities" (Ref. 2). This summary report also addressed external events as part of the IPE program consistent with the option provided in " Individual Plant Examination: Submittal Guidance" (NUREG-1335, Ref. 3), Section 2.5, and provided a cross-referencing " road map" to the detailed ,
supporting information, the " Millstone Unit 3 Probabilistic Safety Study" (PSS, Ref. 4), which was submitted to the NRC in August 1983. The PSS was submitted _ prior to the IPE initiation date, as allowed by response to question 11.3 in Appendix C of NUREG-1335.
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The PSS was the cornerstone on which the IPE/IPEEE was conducted.
l The PSS is based on a Level III probabilistic risk assessment (PRA) and includes flooding, seismic, and other external events.
The original PSS and two of its' revisions (April and November 1984) were extensively reviewed by the staff (documented in NUREG-1152, " Millstone 3 Risk Evaluation Report," Ref. 5) and contractors (BNL, LLNL, Refs. 6 & 7). The PSS is being updated continuously to ensure that the model is in conformance with the as-built plant configuration (i.e., a living PRA).
Upon staff review of the Millstone 3 IPEEE submittal and its associated documentation, a request for additional information (RAI) was sent to the licensee in April 1994 (Ref. 8). The additional information requested pertains to the enhancements discussed in NUREG-1407 to overcome deficiencies of some of the past PRAs when these PRAs are used to satisfy requirements of the IPEEE program. The licensee responded to the RAI on June 6, 1994 (Ref. 9). The response subsequently was reviewed by the staff.
This Staff Evaluation Report documents the staff review of the Millstone 3 IPEEE. Internal fire is not addressed in this report.
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9906020184 990526 PDR ADOCK 05000423 P PDR
e 2.0 3BIsMIC.ZYENTS 1
2.1 MILLSTONE 3 PSS Results In the Millstone 3 PSS, the licensee estimates that the mean annual core damage frequency (CDF) due to internal and external events is about 5E-5/yr and 2E-5/yr respectively. The total contribution to CDF from seismic events is 9.1E-6/yr, which is 13% of the total CDF including both internal and external events.
Of the CDF attributable to seismic events (seismic CDF),
! approximately 45% is from 0.45g and 0.55g peak ground acceleration level earthquakes, let is from 0.35g level, 13% is from 0.65g level, 9% is from 0.80g level, 74 each is.from 0.25g and 0.75g level, and less than 14 is from 0.15g level. It is to )
be noted that Millstone 3 is designed to withstand a safe '
shutdown earthquake (SSE) of 0.17g peak ground acceleration.
The modeling of accident sequences in the seismic risk analysis was accomplished by utilizing logic similar to that employed in the internal event analysis. The internal initiating event categories were examined to determine their applicability cs seismic induced initiators following an earthquake. This effort, combined with a additional analysis of seismic-induced initiators, resulted in the identification of four categories of seismic-induced initiators, which are:
(3) Loss of Offsite Power (LOSP) Transient "T", and (4) LOCA with Containment Bypass "V3" These 4 seismic initiators yielded 19 discrete plant damage states (PDSs). The 19 PDSs were subsequently modeled by fault trees. Both seismic and random failures were postulated to occur as the result of an earthquake.
In terms of PDSs, the percentage contribution to total seismic CDF is as follows:
(1) V3 = 1.1%
(2) AE = 7.2%
(3) SE = 20.9%
(4) TE = 63.0% :
(5) All others = 7.8% :
The "E" above in the PDSs signifies "early core-melt" due to failure of injection.
The major contributor to mean CDF and latent fatalities are found by the licensee to be station blackout (caused by LOSP and loss of onsite AC power) induced RCP seal LOCAs and ATWS events.
These events are small LOCAs with no containment cooling.
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The major contributor to early fatalities due to seismic events
{ is dominated by the release classes M4 and M6. The release class
' M4 is attributed to a scenario in which a LOCA occurs together with a loss of containment isolation due to the collapse of the containment crane wall for seismic events far beyond the SSE.
The dominance of the release class M6 is attributed to the PDS AE which results from a large LOCA followed by early core-melt. ,
2.2 Methodoloav For the seismic review of the IPEEE (hereafter referred to as
" seismic IPEEE"), Millstone 3 was classified by Supplement 4 of GL 88-20 as "0.3g Focused scope" plants east of the Rocky Mountains.
l The licensee used an existing seismic PRA contained in the PSS together with enhancement submitted in Reference 9. This approach was one of the two methodologies listed in~ supplement 4 of GL 88-20 for the seismic IPEEE and was found by the staff to i
be acceptable. These enhancement are described below for l
Millstone 3 seismic IPEEE.
2.3 GL 88-20. Sueolement 4 Enhancements 2.3.1 Mazard Selection
- NUREG-1407 stated that for PRAs at sites east of the Rocky l Mountains that did not use the LLNL and EPRI mean hazard i estimates, sensitivity studies should be conducted to determine if the use of these results would affect the delineation or ranking of seismic sequences.
l In Reference 9 the licensee acknowledged that the 1989 LLNL l hazard curves predicted higher frequencies of exceedance compared l to the Dames & Moore (1983) hazard curves used in the Millstone 3 PSS over the entire range of acceleration values. The licensee however stated that the use of LLNL hazard curves would not have l led to conclusions or vulnerability insights different from those l that were obtained using the Dames & Moore curves, since the i contributors to the frequencies of occurrence of significant PDSs l by earthquakes in the range of 0.25g to 0.35g are small even when the LLNL curves were used. This conclusion was based on a comparison of PDS frequencies derived using the 1989 LLNL curves and two additional revisions (1984 and 1993) of the LLNL hazard model. Thus, additional sensitivity studies addressing the 1989 and 1993 LLNL hazard curves are not justified. The licensee further stated that when the excessive conservatism is removed from the LLNL curves (utilizing the revised hazard models) the results are comparable to those obtained using the Dames & Moore curves, as presented in Table 4 of Reference 9.
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2.3.2 Plant Walkdowns f I 1
Millstone 3 plant is relatively new (Co date is April 1986), and there is in general a higher requirements on the seismic design >
and construction on these newer plants as compared to the older )
vintage ones.
j In spite of the new vintage of the plants, Northeast Utilities l I
did conduct seismic walkdowns (Ref. 9). The seismic walkdowns were performed during the late 1983/early 1984 time period. The ;
team that performed the walkdown of the structures was led by D. )
A. Wesley of Structural Mechanics Associates (SMA). The taam '
that performed the walkdown of the electrical and mechanical components was led by R. D. Campbell of SMA. Northeast Utilities staff participated in the seismic walkdowns.
After the seismic fragilities report (Ref. 10) was submitted, NRC contracted Dr. John Reed of Jack Benjamin Associates to perform a i valkdown for the purpose of an independent review of seismic ,
fragility, wind and external flooding.
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2.3.3 Relay Chatter l Relays, in this context, include components such as electric I relays, contactors, and switches that are prone to chatter. !
NUREG-1407 stated that for non A-46 plants (Millstone 3 being one) in the focused scope, the low-seismic-ruggedness relays (bad ,
actor list) should be located and evaluated. l In the NRC Millstone 3 Risk Evaluation Report (NUREG-1152, Ref.
5), the staff recommended that the licensee develop operator I training and/or procedures to recover from earthquake-induced relay chatter. In Reference 9, the licensee stated that, taking into consideration the staff recommendation on relay chatter, it completed an upgrading of Abnormal Operating Procedure AOP-3570,
" Earthquake," to identify potentially vulnerable relays whose status would be verified after an earthquake to ensure against inadvertent operation. Reference 11 was submitted to NRC which documents how relay chatter issue was resolved for Millstone 3.
2.3.4 Liquefaction NUREG-1407 statM that for plants in the focused scope, EPRI NP-6041 contains guidance for soil failure analyses; a review based on appropriate design and construction records is considered adequate. A detailed analysis, as necessary, will be performed if soil failure is deemed significant.
In Reference 9, the licenses quoted statements made in the Millstone 3 FSAR. The FSAR stated thatt
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(1) Detailed studies of potential soil liquefaction were performed to support licensing of Millstone Unit 3.
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(2) The soils most susceptible to liquefaction are the beach and glacial outvash sands adjacent to the circulating and Service Water Pumphouse. A conservative case assumption is to consider that these soils would fail in a seismic event and the consequences considered. In the worst case scenario it was determined that the operation of the service water pumps would not be impaired in the unlikely event that the soil did fail.
Based on these studies and conclusions, the licensee concluded that no further analysis of soil liquefaction is required for the Millstone Unit 3 IPEEE. -
2.3.5 HCLPF Calculations Table 5 and 6 were provided in the licensee-submitted Reference 9, which lists High confidence of Low Probability of Failure (HCLPF) values of key safety-related structures and equipment in Millstone 3. Which are derived from Tables 3-1A and 3-1B of Reference 12. Median capacities and uncertainty parameters (logarithmic standard deviations using lognormal distribution) of these structures and equipment were calculated in the fragility analysis, and these information were then used to calculate the HCLPF values.
2.4 containment Performance NUREG-1407 stated that all licensees should ensure that the performance of containment and containment systems are addressed in the IPEEE's.
In Reference 9 the licensee stated that both the containment structure and the systems that impact post core-melt containment performance (e.g., quench spray pumps, header and piping, containment recirculation system piping, pumps, and heat exchangers) belonged to the scope of investigations for the Millstone 3 seismic PRA. These investigations determined the containment systems and structures possess adequate strength so that no seismically unique vulnerabilities exist. From the seismic point of view, the weakest components of the containment recirculation system are the heat exchangers, which have a HCLPF value of 0.21g. However, the weakest component of the quench spray system which is a diverse system for containment heat removal, has a HCLPF value of 0.46g (quench spray piping).
Therefore, there is adequate ruggedness for the containment heat removal function. The seismic PRA did not uncover any other seismically unique containment performance vulnerabilities.
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2.5 staff conclusions (1) Independent of the Millstone 3 PSS, the staff performed its own risk evaluation (NUREG-1152, Ref. 5) on Millstone 3. The staff estimated the mean annual CDF due to earthquakes to be about 6E-6 using fragilities from the PSS and the PSS hazard curves (Dames & Moore curves). This is very close to the estimation of 9.1E-6 made by the licensee in its PSS.
(2) Regarding seismic PRA methodology enhancements to address IPEEE concerns, the licensee response (Ref. 9) described in Section 2.3 above uns reviewed by the staff and following are the conclusions:
(a) Hazard Selection The staff generally agrees with the licensee assessment that additional sensitivity studies addressing the 1989 and 1993 LLNL hazard curves are~not needed. However the staff found the statement made in Reference 9, that when the excessive conservatism is removed from the LLNL curves the results are comparable to those obtained using the Dames & Moore curves as shown in Table 4 of Reference 9, questionable. Table 4 shows that for PDS V3, the Dames & Moore curves give an estimated value for the annual frequency of PDS that is respectively, two and one order of magnitude lower than the values derived using the two modification of the LLNL curves. For PDS AE, the comparative differences are 25 times and 2.5 times lower, and for PDS SE, 12.5 and two times lower. For PDS TE, the values are, respectively, five times lower and the same.
(b) Plant Walkdowns The staff concludes that walkdowns conducted during the PSS development satisfy the intent of GL 88-20, Supplement 4.
(c) Relay Chatter The staff concludes that the updated Abnormal operating Procedure satisfies the intent of GL 88-20, Supplement 4.
(d) Liquefaction The staff agrees with the licensee statement and concludes that no further analysis of soil liquefaction is required for Millstone 3 IPEEE.
(e) HCLPF calculations The staff concludes that the HCLPF values provided by the licensee in Tables 5 and 6 of Reference 9 to be adequate.
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(3) Regarding containment performance, based on the HCLPF value
( of the weakest component of quench spray system reported by the licensee in Reference 9 (0.46g for quench spray piping, which is 2.7 times the SSE value), the staff agrees that there is adequate seismic ruggedness for the containment heat removal function, and that the containment systems and structures possess adequate strength so that no seismically unique vulnerabilities exist.
(4) In accordance with NUREG-1407, the IPEEE submittal should contain information to address other seismic issues such as USI A-45, GI-131 and USI A-46. Millstone 3 is not an A-46 plant, therefore USI A-46 is not applicable. Reference 9 provided licensee input on USI A-45 and GI-131.
Regarding USI A-45, the staff concludes that the information provided, including that in Tables 5 and 6, supports the licensee conclusion that Millstone 3 has no vulnerabilities related to the seismic aspects of USI A-45 and that there are no known components whose seismic capability degrades the auxiliary feedwater (AFW) or feed and bleed functions.
Regarding GI-131, the staff concludes that the information provided adequately documents that GI-131 is closed for Millstone 3.
(5) In Reference 5, the staff mentioned that it believes there are cost-effective improvements in prevention and mitigation of a station blackout caused by an earthquake beyond the SSE. The staff recommended that the licensee perform an engineering 3 analysis of the costs, benefits, uncertainties, and competing risks of upgrading the diesel generator lube oil cooler anchorage system.
In its IPE submittal (Ref. 2), the licensee stated that from its study it agreed the only potential vulnerability discovered that required modifications was the replacement of anchor bolts on the diesel generator oil coolers with bolts of stronger material, and this replacement has already been completed. The staff, therefore, considers this concern resolved.
3.0 EITERNAL FLOODS 3.1 MILLETONE 3 PSS Results Section 2.4 of Millstone 3 Final Safety Analysis Report (FSAR, Ref. 13) on external floods stated that it meets the criteria of 1975 Standard Review Plan (NUREG-75/087, Ref. 14). l In addition, the PSS (Ref. 4) and IPE Summary Report (Ref. 2) considered external flooding to be an insignificant contributor to risk due to the following:
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f (1) There are no major rivers or streams in the vicinity of I Millstone 3, nor are there any water courses on the site.
(2) The North Atlantic coastline has an extremely low probability of tsunamis.
(3) In view of the maximum stora surge flood levels, the very low frequency associated with these events, and the plant features designed for protection against such extreme flooding condition, tidal flooding is an insignificant contributor.
(4) In view of the maximum precipitation intensities, the very low associated frequencies, and the plant features designed to withstand such conditions, intense precipitation is an insignificant contributor.
3.2 Staff Conclusions one of the acceptable methodologies for performing external floods evaluation of IPEEE, as stated in NUREG-1407 (Ref. 1), is for the licensee to show that 1975 Standard Review Plan (NUREG-75/087, Ref. 14) criteria are met.
l Since Millstone 3 FSAR (Ref. 13) stated that Section 2.4 on l
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external floods meets the criteria of 1975 Standard Review Plan, and the PSS also gave qualitative reasons why external floods are considered insignificant contributors for risk at Millstone 3 site, the staff agrees that external flooding is not an issue of concern.
l 4.0 OTEER EXTERNAL EVENTS 4.1 MILLSTONE 3 PSS Results l
4.1.1 High Winds The PSS (Ref. 4) and IPE Summary Report (Ref. 2) considered high winds to be an insignificant contributor to risk due to the following:
(1) The frequency of exceeding the design tornado wind speed of 360 mph at Millstone 3 is calculated to be approximately 5.35E-6/yr.
(2) All Millstone 3 safety-related structures are of reinforced concrete with wall thicknesses of at least 2 feet.
(3) Compressive stresses induced in the walls due to the weight ,
of the roof and above floor loads reduce the tendency toward the !
development of tensile stresses in the concrete.
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Furthermore, the licensee concluded that tornado missiles do not
( constitute a significant risk to the safe opsration based on the following:
(1) The estimated frequency of a tornado missile striking a l
safety-related structure and the frequency of missile-induced backface scabbing of 12"-18" reinforced concrete wall for Millstone 3 are 3.5E-5/yr and 1.7E-6/yr, respectively.
(2) Since all Millstone 3 safety-related walls have thickness exceeding 24" and since scabbing and penetrations do not necessarily lead to loss of vital components leading to core-melt, the frequency of a missile induced core-melt is estimated to be one to several' orders of magnitude below 1.7E-6/yr.
4.1.2 Aircraft Crash The PSS (Ref. 4) End IPE Summary Report (Ref. 2) considered aircraft crash to be an insignificant contributor to risk due to the following:
(1) The risk from aircraft accidents due to near-airport accidents and inflight accidents was estimated using information on nearby air facilities and airways. The Millstone 3 PSS estimated the aircraft crash frequency at the Millstone 3 site form general aviation, commercial aviation, and military aviation to be 1.5E-6/yr, 1.2E-7/yr, and 3.4E-9/yr, respectively. These frequencies were estimated in accordance with procedures described in Section 3.5.1.6 of Rev. 2 (July 1981) of the NRC Standard Review Plan (Ref. 14). Since completion of the Millstone 3 PSS, one of the two airports near the Millstone site (Waterfore-New London) has closed. Therefore, these risks are even lower.
(2) It has been estimated that a general aviation crash could initiate a LOSP, but a core melt accident would further require the independent random failure of onsite power. In view of the extremely low frequencies associated with this scenario, and with commercial and military aircraft crashes, it is concluded that aircraft hazards do not constitute a significant contribution to core melt risk.
4.1.3 Transportation and Other External Hazard The PSS (Ref. 4) and IPE Summary Report (Ref. 2) considered transportation and turbine missiles to be insignificant contributors to risk due to the following:
(1) After detailed consideration of road, rail, and waterway traffic routes, and the potential for dancge to safety-related~
structures attributed to transportation of hazardous materials,
! potential missile generations, vapor cloud explosions, and
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control room uninhabitability, it was determined that
( transportation accident pose an insignificant risk.
Storage of large quantities of hydrogen and liquid chlorine were viewed as potential contributors to risk. (Since publication of the Millstone 3 PSS, the chlorine system has been replaced by a less hazardous sodium hypochlorite system.) After evaluations, the risk due to storage of these hazardous materials were found to be insignificant.
(2) The frequency of significant damage to safety-related structures and equipment from turbine missiles was estimated to i be approximately 7.5E-9 for the 30-year lifetime of the plant, and is considered an insignificant contributor to risk. This above number was generated after estimating the frequency of turbine missile generation due to the two plausible mechanisms, ductile fracture and stem corrosion. This frequency was coupled with estimates of conditional probabilities of turbine missile striking a critical structure and the conditional probability of the striking missile to cause significant damage.
4.2 Staff Conclusions The following staff evaluation is taken from the contractor's report N5dG/CR-4142 (Ref. 7).
(1) A qualitative screening analysis in the PSS concluded that effects of high winds at Millstone 3 are not significant contributors to CDF. The basis for this finding is that the governing wind event is the occurrence of severe tornadoes, and all safety-related structures have been designed to resist tornado loads and resultant missiles for wind speeds up to 360 mph. The minimum thickness of reinforced concrete in the walls and roofs of these structures is 2 feet.
The site hazard for tornado winds exceeding 360 mph is given as 5.35E-6/yr. The staff believes this figure to be conservative and that justification exists (not provided in the PSS) to show that this probability is less than 1E-8/yr. This frequency of structural failure or missile-induced damage, given a 360 mph tornado, would be smaller than 0.1.
The staff therefore agrees that high winds are not significant external events even though no fragility curves were developed, no systems analysis was performed, and no uncertainty analysis was included.
(2) The quantitative assessment of the frequency of onsite I aircraft crashes performed in the Millstone 3 was done in accordance with the NRC Standard Review Plan (Ref. 14). The ,
total frequency estimates for onsite accidents of 1.6E-6/yr is !
dominated by a contribution of 1.5E-6/yr from general aviktion 1 10
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Q (light aircraf t), whose damage potential is limited to the
(- switchyard. The FSAR otates that no increase in air traffic is projected in the vicinity of the site, but the PSS does not
, address this topic.
The staff judges the effective plant area and structures considered susceptible to damage by the various classes of aircraft to be reasonable and conservative. The staff also judges the analysis of crash frequencies to be conservative choices for the numbers and types of flights considered.
The conclusion that aircraft crashes are not significant contributors to core melt accidents, based on their low frequencies and the low likelihood of such an accident resulting in core melt, is judged to be reasonable and acceptable.
(3) For transportation and storage of hazardous materials, the Millstone 3 PSS considered road, rail and water transport routes, and offsite and onsite storage facilities and pipelines.
Numerical estimated of potential risk were made only for rail shipments of propane (a small contributor) . All other potential sources were dismissed. l The conclusion that all of these accident types are relatively insignificant contributors to core melt is judged to be correct, but inadequately justified, particularly for accidents involving storage of chlorine in railroad tank cars.
(4) For turbine missiles, the Millstone 3 PSS concluded it to be insignificant contributor to CDF on the basis of their low frequencies.
1 In an analysis supplied by General Electric (Ref. 15), it is found that the use of a frequency of 1.4E-8/yr of missile generating turbine failures results in a frequency of significant damage to critical structures or components of 2.5E-10/yr. This low frequency does not account for-recent NRC concerns with stress corrosion cracking. 4 Acknowledging this concern, a second calculation was pe rformed in the PSS using lE-4/yr for missile-generating turbine failures, as recommended in NRC Regulatory Guide 1.115 (Ref. 16). The result is a frequency of 1.8E-6/yr for significant damage to critical structures or components, which the PSS judges to be acceptable due to conservatism in the overall analysis. The staff agrees that this conclusion is reasonable.
5.0 OVERALL STAFF CONCLUSIONS (1) The original PSS and two of its revisions (April and November 1984) were extensively reviewed by the staff (Ref. 5) and
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( contractors (Refs. 6 & 7). The staff in Reference 5 estimated
, the mean annual CDF due to earthquake to be about 6E-6 using fragilities from the PSS and the PSS hazard curves (1983 Dames &
Moore curves), and this compares favorably with licensee's own estimation of 9.1E-6 in its PSS (Ref. 4) . The PSS further estimated the contribution to CDF from seismic events is about 13% of the total CDF including both internal and external events.
(2) The staff in Reference 5 recommended that the licensee develop operator training and/or procedures to recover form earthquake-induced relay chatter. The licensee responded in Reference 9 that the Abnormal Operating Procedure A0P-3570,
" Earthquake," was upgraded to identify potentially vulnerable relays whose status would be verified after an earthquake to ensure against inadvertent operation. The staff judges this response to satisfy the intent of GL 88-20 regarding relay chatter.
(3) The staff concludes that the licensee in general has carried out external event analyses using acceptable state-of-the-art approached used in many recent PRAs.
(4) The general purpose of the IPEEE, as mentioned in GL 88-20, Supplement 4, is for each licensee (a) to develop an appreciation of severe accident behavior, (b) to understand the most likely severe accident sequences that could occur at its plant under full power operating conditions, (c) to gain a qualitative understanding of the overall likelihood of core damage and radioactive material release, and (d) if necessary, to reduce the overall likelihood of core damage and radioactive material releases by modifying hardware and procedures that would help '
prevent or mitigate severe accidents. The licensee's PSS (Ref.
- 4) and IPE Summary Report (Ref. 2) are considered detailed enough to meet these objectives.
In Reference 5, the staff stated that it believes there are cost-effective improvements in prevention and mitigation of a station blackout caused by an earthquake beyond the SSE. The staff recommended that the licensee perform an engineering analysis of the costs, benefits, uncertainties, and competing risks of upgrading the diesel generator lube oil cooler anchorage system.
The licensee stated in its IPE submittal (Ref. 2) that it agreed the only potential vulnerability discovered that required modifications was the replacement of anchor bolts on the diesel generator oil coolers with bolts of stronger material, and it has already done so by replacing the original diesel generator oil cooler anchor bolts (SAE-Grade 2) with the stronger material (ASTM A-325) bolts. The staff, therefore, considers this potential concern resolved.
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6.0 REFERENCES
- 1. USNRC Generic Letter 88-20, Supplement 4, " Individual Plant Examination of External Events (IPEEE) for severe Accident Vulnerabilities - 10 CFR 50.54 (f)," with enclosed NUREG-1407,
" Procedural and Submittal Guidance," June 28, 1991.
- 2. Northeast Utilities, " Millstone Unit 3 Individual Plant Examination for Severe Accident Vulnerabilities," August 1990.
- 3. USNRC NUREG-1335, " Individual Plant Examination Submittal Guidance," August 1989.
- 4. Northeast Utilities, " Millstone Unit 3 Probabilistic Safety Study," August 1983.
- 5. USNRC NUREG-1152, " Millstone 3 Risk Evaluation Report," June 1986.
- 6. USNRC NUREG/CR-4143, " Review and Evaluation of the Millstone 3 Probabilistic Safety Study: Containment Failure Modes, Radiological Source Terms and Offsite Consequences," M. Khatib-Rahbar et al., Brookhaven National Laboratory, September 1985.
- 7. USNRC NUREG/CR-4142, "A Review of the Millstone 3
, Probabilistic Safety Study," A. Garcia et al., Lawrence Livermore r National Laboratory, April 1986.
- 8. Letter dated April 6, 1994 from V. L. Rooney of USNRC to J. F.
opeka, dortheast Utilities System, subject: Request for Information Concerning Review of IPEEE for External Events.
- 9. Letter dated June 6, 1994 from J. F. Opeka of Northeast Utilities System to USNRC, subject: Millstone Nuclear Power Station, Unit No. 3, Response to Request for Additional Information Concerning the Review of the Individual Plant Examination for External Events.
- 10. Appendix 2-I to " Millstone Unit 3 Probabilistic Safety Study
- Seismic Fragilities of Structures and Components at the Millstone 3 Nuclear Power Station," D. A. Wesley, et al.,
Structural Mechanics Associates, March 1984.
- 11. Letter dated January 15, 1988 from E. J. Mroczka of Northeast Utilities System to USNRC, subject: Millstone Nuclear Power Station, Unit No. 3, Procedure - Earthquake Induced Relay Chatter.
- 12. "A Program to Determine the Capability of Millstone 3 Nuclear Power Plant to Withstand Seismic Excitation Above the Design SSE,' M. K. Ravindra, et al. , Structural Mechanics Associates, November 1984.
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s, I.' 13. Northeast Utilities, " Millstone Nuclear Power Station Unit 3 Final Safety Analysis Keport," Volumes 1 & 2, updated July 1993.
- 14. USNRC NURIG-75/087, " Standard Review Plan for the Review of Safety Analysis Report for Nuclear Power Plants," LWR edition, December 1975.
- 15. General Electric Company, Hypothetical Turbine Missiles -
Probability of occurrence, Memo Report, March 1983, cited in G.
C. K. Yah, " Probability and containment of Turbine Missiles,"
Nuclear Engineering and Design, Vol. 37, 1976.
- 16. USNRC, " Regulatory Guide 1.115, Protection Against Low Trajectory Turbine Missiles," Rev. 1, July 1977.
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O APPENDIX 2 STAFF EVALUATION REPORT ON INTERNAL FIRE PORTION OF I
INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) SUBMITTAL FOR MILLSTONE 3 NUCLEAR POWER PLANT e
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