ML19323F362
| ML19323F362 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/02/1980 |
| From: | Wiggington D Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TAC-13049, NUDOCS 8005280850 | |
| Download: ML19323F362 (6) | |
Text
.
8[g nitg o, UNITED STATES NUCLEAR REGULATORY COMMISSION n
y y
WASHINGTON, D. C. 20555
'% *****,o May 2,1980 Docket flo. 50-334 LICEllSEE: Duquesne Light Company
SUBJECT:
MEETING
SUMMARY
- ECCS DECAY HEAT EXCHANGER I'lTEGRITY P1R BEAVER VALLEY UNIT NO. 1 On April 22, 1980, the licensee and Stone and Webster met with the Staff to discuss the consequences of failure and methods to assure integrity of the recirculation spray heat exchanger system for the Beaver Valley Unit No. 1.
The list of attendees is attached (Attachment 1).
The licensee had previously met with the Staff on March 25, 1980.
The details of that meeting and background information are included in the meeting summary dated April 7, 1980. This meeting was held to discuss the consequer.ces of failure of the heat exchanger and components and methods to mitigate unacceptable consequences.
Discussion The consequence analysis performed by Stone and Webster assumed the TID 14844 source term in the reactor containment sump and with the releases held to the 10 CFR 20 limits, the recirculation heat exchanger leak rate can be no more than 2 x 10-4 gpm from the 3400 tubes in the four heat exchangers.
Assuming a dilution factor of 10 in the river, the doses in the drinking water at the Midland water intake would be as follows for one liter of water consumed:
Adult Thyroid Dose 190 mrem Child Thyroid Dose 583 mrem Infant Thyroid Dose 1400 mrem The potential air borne dose would be less than 10-2 mrem /hr at the site boundary when 2% evaporation rate is assumed in the cooling tower.
It is not clear that this accounts for potential iodine releases from the water as the sump leakage pH drops from 8 in the sump to 7 in the cooling tower. The significance of the dose calculations is that almost any lqakage in the heat exchanger would produce unacceptable results. The 2 x 10-'+ gpm leakage is for less than one tube breaking out of the 3400; it is something just larger than a pin hole leak in a single tube.
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Meeting Summary for Beaver Valley,
1 The licensee provided a basic information sheet on the recirculation heat i
exchangers which is attached (Attachment 2).
Stone and Webster investigated the design for vibration damage between the tubes and tubes /baffel plates.
Little potential exists for damage of this type. The tubes are rolled into
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a double grove in the tubesheets and seal welded so that a high initial l
integrity can be assumed. The tubes, baffels, and tubesheets are all 304L stainless steel and operate in an environment which is not expected to produce stress corrosion cracking or other modes of failure.
While it is not apparent that the heat exchanger will deteriorate and fail, there is no assurance against tube degradation and eventual failure over the 30-40 year life of the plant.
The licensee had hydrotested the heat exchanger during construction and due to the containment isolation configuration, they had also performed a type C leak test on the tube side. No failures had been detected by these means.
To provide further assurance of integrity, the licensee performed a freon test on the tube side. Water was drained from both the tube and shell side and about 10 to 20 lbs of freon at 70 psig was applied to the l
tubes. The test was allowed to " soak" for a period of time to allow any freon leak to accumulate on t A portable detection instrument with a sensitivity of 1 x 10 ge shell side.
freon /cc of air did not detect any leakage j
from the four heat exchangers.
The radiation monitors on the discharge river water side are set for a sensitivity of 10-6 p ci/cc with a background of 5 mrem /hr. The licensee did not quantify the expected radiation levels in the area of the monitors following an accident although the largest souce of radiation is expected to be from the sample line from the failed heat exchanger (assuming an accident and a leaking recirculation spray heat exchanger). The radiation monitors are seismic Class I designed to the 1963 ASME Code. The Hi-Hi alarm setpoint is equivalent to-2.2 x 105 cpm which also corresponds to i
l 10 CFR 20 limits.
The monitor pumps, flow indicators and radiation detector /
circuitry are tested and calibrated periodically.
1 The river water piping, the bellows expansion joints, and pressure relief valves were not tested during the freon tests by the licensee. The river water piping is carbon steel. A carbon steel to stainless steel transition joint is employed outside the heat exchanger on the inlet and outlet lines.
Following a LOCA, it is not clear how a leak in the river pipes or bellows expansion joint inside containment would be detected and boron dilution of the sump prevented. The pressure relief valve outside containment on the river water discharge will relieve to the auxiliary building sump. Water
-discharge will be detected by the sump pump operation and by area monitors j
in the auxiliary building.
Conclusions and Positions The licensee proposed an 18 month freon. test of the heat-exchangers tube side, as being adequate to detect leakage and assure integrity.
While the Staff 1
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Meeting Sunnary for Beaver Valley believes the freon test to be highly sensitive to leaks and does provide adequate assurance of the existing leak-tightness, it does not provide information on the required integrity for the subsequent periods of operation should the heat exchanger be called upon. The test recently perfomed by the licensee and the fact that the heat exchangers are relatively young in life led the staff to conclude there is reasonable assurance of continued integrity so that the Beaver Valley Unit No.1 can be returned to power following the current outage without a tube degradation inspection.
The licensee was instructed to include a freon test at each refueling outage (nomal 18 month cycle) to be preceded by a pneumatic or other pressure test along the requirements of Section XI of the ASME Code. This test is expected to produce leaks that are about to occur and then be detected by the freon test. The details of such a test are to be developed by the licensee and included in their Inservice Inspection Program before the second refueling outage.
The test for tube and tubesheet degradation is an open issue.
At some point in the heat exchanger life, the licensee must begin to examine for degradation to assure continued integrity should operation ever be required.
The licensee was instructed to consider means for testing for heat exchanger degradation including a schedule and basis for beginning such testing. The type of test, basis for acceptance criteria, and schedule for periodic performance of the tests is to be developed by the licensee, submitted to the NRC for review, and subsequently included in the licensee's Inservice Inspection Program.
The Staff did not reach a position on the preferred normal condition of the heat exchanger. The licensee was requested to develop a position and provide a technical basis for draining and drying the heat exchanger to include discussion of concentrating chlorine by drying and creating a water hammer problem by having a river water system charging to an empty heat exchanger.
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Dave Wigginton, ject Manager Operating Reactors Branch #1 Division of Licensing Attachments:
1.
List >f Attendees 2.
Heat Exchanger Spec Sheet cc: w/ attachments See next page f
f
o e:eeting Suramary f or Beaver Valley 1 Occket files t&.C PDR Local PDP.
O. sol Reading fiRP, Readit:9 H. Denton E. Case D. Eisenhut R. Tedesco G. Zecn B. Grimes W. Gammill L. Shao J. Miller R. Vollmer T. J. Carter A. Schwencer D. Ziemann P. Cneck G. Lainas D. Crutchfield
- 6. Grimes T. Ippolito R. Reia V. i<conan G. Kriighton
- b. brinkman Project Manager OELO 014E (3)
C. Parrish/P. Kreutzer ACRS (16) fiRC Participants NSIC V
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censee Short Service List I
ATTACHiiENT 1 DECAY HEAT EXCHANGER _
MEETING BEAVER VALLEY POWER STATION 1 APRIL 22, 1980 Name Organi,zation 1
D. Wigginton NRC D. Shum NRC J. D. Sieber DLC - Licensing K. D. Grada DLC-Operations P. C. Hearn NRC Frank H. Timpano VEPC0 R. E. Vanasse Stone and Webster C. E. Ader Stone and Webster R. C. Tappan Stone and Webster C. F. Andreone Stone and Webster W. C. Drotleff Stone and Webster B. Turovlin NRC H. F. Conrad NRC J. E. Rosenthal NRC L. B. Engle NRC R. Woods NRC C. Y. Cheng NRC George Johnson NRC K. R. Wichman NRC J. Zudans NRC Vince Noonan (part time)
NRC
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