ML20054K522
| ML20054K522 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 06/29/1982 |
| From: | Caruso R Office of Nuclear Reactor Regulation |
| To: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| References | |
| TASK-03-05.B, TASK-3-5.B, TASK-RR LSO5-82-06-118, LSO5-82-6-118, NUDOCS 8207020277 | |
| Download: ML20054K522 (11) | |
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June 29, 1982 j
V Docket !!o.50-029 L505-82-06-118 fir. J. A. Kay Senior Engineer - Licensing Yankee Atomic Electric Company 1671 Worcester Road Franinghan, Massachusetts 01701
Dear fir. Kay:
SUBJECT:
SYSTEllATIC EVALUATI0tl PROGRAM TOPIC III-5.B. PIPE BREAK OUTSIDE CONTAINMENT FOR YANKEE NUCLEAR POWER STATION In your letter dated January 21, 1982, you submitted a safety assessnent report on the above topic. We have completed our evaluation, which is enclosed.
Based on our review of your safety assessment report, we conclude that the Yankee fluclear Power Station is adquately protected from the dynamie.
effects of pipe break outside containment subject to resolution of the following in the Integrated Assessment.
1.
Effects of rain steam line break on adjacent non-return hydraulic operator.
2.
Jet inpingement on the switchgear roon block wall from a break in the No. 2 feedwater heater extraction stean line on the nezzanine level.
The need to actually implement changes as a result of these itens will be detemined during the integrated safety assessnent. This safety evaluation may be revised in the future if your facility design is changed or if HRC criteria relating to this topic are nodified before the integrated assessment is completed.
Sincerely' osa aaadi)
Ralph Caruso, Project Manager /o/4/ h.6 Operating Reactors Branch No. 5 8207020277 820629 PDR ADOCK 05000029 livision of Licensi 1
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Enclosure:
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. Mr. James A. Kay CC Mr. James E. Tribble, President Yankee Atomic Electric Company 25 Research Drive Westborough, Massachusetts 01581 Chairman Board of Selectmen Town of Rowe Rowe, Massachusetts 01367 Energy Facilities Siting Council 14th Floor One'Ashburton Place Boston, Massachusetts 02108
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U. S. Environmental Protection Agency.
Region I 6ffic'e ATTN:
Regional Radiation Representative JFK Federal Building Boston, Massachusetts 02203 Resident Inspector Yankee Rowe Nuclear Power Station c/o U.S. NRC Post Office Box 28
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Monroe Bridge,* Massachusetts 01350 Ronald C. Haynes, Regional Administrator
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Nuclear Regulatory Commission, Region I 631 Park Ave'nue King of Prussia, Pennsylvania 19406
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d SEP EVALUATION OF i
PIPE BREAK OUTSIDE CONTAINMENT TOPIC III-5.B FOR YANKEE ATOMIC POWER STATION
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TABLE OF CONTENTS I.
INTRODUCTION II.
REVIEW CRITERIA III.
RELATED SAFETY TOPICS AND INTERFACES IV.
REVIEW GUIDELINES V.
EVALUATION f
A.
Background
B.
Approach and Criteria C.
Interaction Studies D.
Modifications CONCLUSION 9
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I.
INTRODUCTION The safety objective of Systematic Evaluation Program (SEP) Topic
!!I-5.B, " Pipe Break Outside Containment," is to assure that pipe breaks would not cause the loss of required function of " safety-related" systems, structures and components and to assure that the plant can be safely shutdown in the event of such breaks.
The required function of safety-related systems are those functions required to mitigate the effects of the pipe break and safely shut-down the reactor plant.
II.
REVIEW CRITERIA General Design Criteria 4 (Appendix A to 10 CFR Part 50) requires in part that structures, systems and components important to safety be appropriately protected against dynamic effects, such as pipe
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whip and discharging fluids, that may result from equipment failures.
The current criteria for review of pipe breaks outside containment are contained in Standard Review Plan 3.6.1, " Postulated Piping Failures in Fluid Systems Outside Containment," including its
, attached Branch Technical Position, Auxiliary Systems Branch 3-1,
. Break Locations and Dynamic Ef fects Associated with the Postulated
' Rupture of Piping," including its attached Branch Technical Position, Mechanical Engineering Branch 3-1 (BTP MEB 3-1).
111. RELATED SAFETY TOPICS A'ND 1hTERIACES 1
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1.
This review complements that of SEP Topic VII-3, " Systems Required for Safe Shutdown."
2.
The environmental effects of pressure, temperature, humidity and flooding due to postulated pipe breaks are evaluated under Unresolved Safety Issue A-24, " Qualification of Class lE Safety-Related Equipment."
3.< The effects of potential missiles generated by fluid systems ruptures and rotating machinery are evaluated under SEP Topic III-4.C, " Internally Generated Mi ssiles."
4.
The original plant design criteria in the areas of seismic input, analysis design criteria are evaluated under SEP Topic III-6,
" Seismic Design Considerations."
IV.
REVIEW GUIDELINES The licensee's break location criteria and methods of analysis for evaluating postulated breaks in piping systems outside containment have been compared with the currently accepted review criteria as described in Section 11 above.
The review relied upon information submitted by the licensee, Yankee Atomic Electric Company (YAEC),
in References 1, 2 and 3.
, The scope of review under this topic was limited to avoid duplication of effort since some aspects of the topic were previously reviewed by the staff or are included under other SEP topics (See III above).
t,' hen deviations from the review criteria are identified, engineering judgement is utilized to evaluate the consequence of postulated pipe break and to. assure that pipe break would not cause the loss of needed function of " safety-rel ated" systems, sf ructures and. components.
and to assure that the plant can be safely shutdown in the event of such break.,
V.
EVALUATION
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A.
BACKGROUND In December 1972, the staff sent letters (Reference 4) to all power reactor licencees requesting an analysis of the effects of postu.
lated failures of high energy lines outside of containment.
In response to our letter, the licensee submitted an initial report.
concerning postulated high energy pipe rupture outside containment (Reference 1) dated July 2,1973.
Subsequent information was received on September 12,1973 (Reference 2).
In Reference 5, the staff found the licensee's analyses and actions acceptable with respect to the Giambusso letter of December 18,1972, and concluded that upon completion of necessary plant modifications as described in Reference 1 Yankee would withstand the consequences of postulated ruptures in high energy fluid piping outside con -
tainment without loss of the capability to initiate and maintain safe shutdown of the plant. The licensee's SEP reevaluation of pipe break outside containment (Reference 3), therefore, includes the following.
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Approach and Criteria v-2.
Interaction Studies 3.
Modi fications B.
APPROACH AND CRITERIA The licensee utilized the effects-oriented approach in its original high energy line break (HELB) study (Reference 1).
The following assumptions were made by the licensee.
1.
High energy fluid systems are systems with operating tempera-ture > 200F or operating pressure > 275 psig.
In accordance with Tranch Technical Position (BTP) MEB 3-1, breaks are not e
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postulated in piping of systems that qualify as high energy systems for only short operational periods (i.e., less than 2% of the time the system operates as a moderate energy system or less than 1% of the time that the plant operates).
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2.
The worst, unrelated, single active failure occurs simultaneously with the pipe break. Unrelated passive failures are not considered in the short-term.
3.
A simultaneous, unrelated, pipe failure is not postulated with the hign energy pipe break.
4.
The effects of pi,pe whip or jet impingement will not damage equal diameter or larger piping with equal or greater wall
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thickness.
5.
The piping boundary is taken as the first normally closed valv.e, check valve, relief / safety valve or first' capable of remote or automatic closure.
6.
Effects of pipe whip and jet impingement from rupture of piping 1" nominal pipe size and smaller are not required to be analyzed.
7.
The effects of pipe whip, jet impingement, or leakage from moderate energy pipe systems are not required.
Our review of the licensee's assumption as described above indicates that assumptions 1, 4 and 7 require clarification.
With respect to assumption 1, the staff concurs that in general, breaks need not be postulated in piping systems which qualify as high energy systems for only short operational periods.
BTP MEB 3-1 e defines an operational period as short if the fraction of time that the system operates within the pressure-temperature conditions e-specified "for high energy fluid systems is about 2% of the time that the system operates as a moderate energy fuid system (e.g.,
systems such as the reactor decay heat removal system qualify as moderate-energy fluid systems; however, systems such as auxiliary feedwater systems operated during PWR reactor startup, hot standby, or shutdown qualify as high-energy fluid systems).
At Yankee, the emergency feedwater water system is not used for reactor startup or shutdown, but it is used only when main feedwater is not available.
Therefore, it satisfies the less than 2% opera-tional period and pipe breaks need not be considered in this system.
Pressurized portions of the emergency feedwater piping (i.e.,
on the generator side of isolation valves) are considered under Topic III-5.A.
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.. With respect to assumption 4, the staff concurs that the effects of pipe whip will not damage equal diameter or larger piping with equal or greater wall thickness.
However, in accordance with staff positions transmitted on January 4,1980 (Reference 6), the effects of jet impingement should be considered and evaluated regardless of the ratio of impinged and postulated broken pipe sizes. -In thei r ef fects-oriented review, the licensee depended on physical separa.
tion as the main basis for availability of safe shutdown equipment.'
Any components and piping in the vicinity of the high energy line were not credited for safe shutdown.
Therefore, this assumption of jet impingement loads on piping should not change the evaluation.
With respect to assumption 7, current criteria require that through-wall leakage cracks be postulated in Seismic Category I and non-seisnic moderate-energy line (MEL) piping (<-200F and < 275 psig).
The licensee has not addressed this subject in this SEP topic assess-ment.
The effects of failure in non-safety related piping were reviewed by the staff in Reference 7.
The staff concluded that i
Yankee had adequate design features for protection against the rupture of such components or piping. The flooding study included an analysis of the vulnerability to flooding of Class lE equipment required for a safe shutdown.
Each location in the plant containing safety-related equipment was examined in the study for possible flooding sources and mitigating features.
Therefore, we conclude that the flooding effects of cracks in moderate-energy lines have been adequately addressed.
C.
INTERACTION STUDIES The licensee concluded th.at there were negligible differences between the criteria used in its 1973 analysis and the current
, criteria.
Therefore, as part of this topic, the licensee has
.done an effects-oriented analysis of high energy piping systems which were added since the original report.
The licensee has concluded that these additions have resulted in increased ability to safely shutdown the plant.
However, the licensee has identified two areas where potential problems arose.
Based on its evaluation, the licensee concluded that the effects of a main steam line rupture on the non-return valve operators still require further evaluation.
The licensee has also reviewed the analysis performed in the original report (Reference 1) and has concluded that a jet impingement shield plate may have to be added to the switchgear room wall in the area of the No. 2 feedwater heater extraction steam line and further evaluation is required.
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_ The safety injection (SI) recirculation piping is in close proximity to the No. 4 main steam line.
Rupture of the Si line would violate containment integrity.
As shown in Topic XV-2, a main steam line break does not result in fuel damage.
The SI recircu-lation line is not needed to mitigate the event.
Any offsite dose rates will be below 10 CFR 100 limits.
Therefore, the staff considers this interaction to be acceptable.'
D.
MODIFICATIONS As a result of the original investigation (Reference 1), several modifications were found necessary to assure safe plant shutdown.
These modifications as described in Reference 1 have been completed.
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As identified in Section VI.C of Reference 3, the licensee has made several major modifications since 1975 which provide additional assurance that the plant can be safely shutdown in the event of a pipe break outside containment.
These modifi~ cations include:
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Automatic closure of main steam non-return valves.
2.
Addition of two full-capacity motor driven emergency feedwater pumps.
3.
Addition of feedwater flow path via blowdown piping which is outside the turbine building.
4.
Addition of atmospheric dump valves.
The automatic closing of the main steam non-return valves would prevent l
l blowdown of all four steam generators following high energy line breaks.
l The other features described above enb.nce the plant capability to
, remove decay heat.
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VI.
CONCLUSION
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Based on the information submitted by the licensee, we have reviewed the criteria pertaining to the locations, types and effects of postulated pipe breaks in high energy piping systems outside contain-ment.
We have concluded that the criteria used to define the break locations and types are in accordance with currently accepted standards.
We have also determined that it is acceptable under current SEP criteria to use the interaction study to evaluate the effects of postulated pipe breaks and to determine the acceptability of plant response to pipe breaks.
. Two areas have been identified which require further evaluation:
1.
Effects of main steam line break on adjacent non-return hydraulic valve operator.
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2.
Jet impingement on the saitchgear room block wall from a break in the No. 2 feedwater heater extraction steam line on the mezzanine level.
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REFERENCES 1.
Report, " Effects of a Piping System Break Outside Containment at Yankee Nuclear Power Station, Rowe, Massachusetts, The Yankee Atomic Electric Company," dated July 2,1973.
2.
Supplemental information to the above report, dated September 12, 1973.
3.
Report, "SEP Topic III-5.B, Ef fects of High Energy Piping System Breaks Outside Containment at Yankee Atomic Power Station, The Yankee Atomic Electric Company," dated January 21, 1982.
4.
Letter, A. Giambusso (NRC) to YAEC, " General Information Required of the Ef fects of a Piping System Break Outside Containment," dated December 18, 1972.
5.
Letter, D. J. Skovholt (NRC) to D. E. Vandenburgh (YAEC), " Safety Evaluation Concerning Rupture of High Energy Lines Outside Contain-men $, Yankee Atomic Electric Company," dated December 13, 1973.
6.
Let.ter, D. Ziemann (NRC) to R. Groce (YAEC), " Evaluation of Pipe Whip Impact and Jet Impingement Effects of Postulated Pipe Braks for SEP Toapics III-5. A and III-5.B," dated January 4,1980.
7.
Letter, D. Crutchfield (NRC) to J. Kay (YAEC), " Safety Evaluation Report Concerning Susceptibility of Safety Related Systems to Flooding from Failure of Non-Category I Systems for Yankee Nuclear.
Power Station," dated December 29, 1980.
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