ML20009D879
| ML20009D879 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/14/1981 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Bradford P NRC COMMISSION (OCM) |
| Shared Package | |
| ML20009D880 | List: |
| References | |
| NUDOCS 8107240457 | |
| Download: ML20009D879 (4) | |
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'z HEHORANDUM FOR: Commissioner Bradford
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FROM:
William J. Dircks, Executive Director for Operations
SUBJECT:
HILLSTONE UNIT 1 RADI0 ACTIVE RELEASE VIA STORM DRAIN On June 21, 1981, the licensee reported an unmonitored release of radioactivity from Millstone Unit 1 through the storm sewers into Niantic Bay. Based on this, and the Tsuruga event, you wanted to know if the Hillstone Storm Drain System is " representative and allowable".
The requirements of HRR are that during normal reactor operation, including anticipated operational occurrences, all major and potentially significant paths for release of radioactive material should be monitored (10 CFR 50, App. ~ A, GDC 64; R. G.1.21, C.2). Plants are designed, reviewed and Technical Specifications are provided to assure that, during normal operation and anti-cipated operational occurrences, all such related paths are monitored.
The Hillstone 1 release involved a system which had not previously been identified generically as a potential source for release of radioactive materials and, therefore, had not been specifically included as such in plant designs, NRR reviews, or in the Technical Specifications. The specific system is the turbine lubricating oil drain oil / water separator. Drain water had never, in approximately 10 years of operation at Hillstone 1, been observed to drain from the system. The radioactive water was actually condensed primary reactor steam, which is used in older boiling water reactors as sealing steam for the turbine gland seals and for valve stem seals in large steam valves.
The system overflow drain was connected to a turbine building drain system which was connected to the plant storm drain. Apparently, a sealing steam leak occurred in a turbine bypass valve; condensate from this leak accumulated in the lubricating oil recovery system and flowed to the oil / water separator, resulting in the unmonitored discharge, as described above.
Our preliminary review indicates the potential for similar leakage at other plants is limited to older boiling water reactor designs. Newer boiling water reactors utilize " clean" steam for sealing systems, with the non-radio-active steam being provided by auxiliary boilers. Pressurized water reactors utilize clean secondary-side steam for sealing systems.
The Office of Inspection and Enforcement is assessing the generic implications of the Hillstone 1 event to determine if either a circular or bulletin should be issued to plants having a potential for similar releases.
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$ A brief description of the circumstances surrounding the Hillstone 1 event and additional relevant information are provided in the enclosure.
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J. J. Shea Ext. 27231 cc:
Chairman Palladino Comissioner Gilinsky Comissioner Ahearne L. Bickwit, OGC
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y MEMORANDUM FOR: Peter A. Bradford FROM:
William J. Dircks, Executive Director for Operations
SUBJECT:
HILLSTONE UNIT 1 RADI0 ACTIVE RELEASE VIA STORM DRAIN s
On June 21, 1981, the licensee reported an unnonitored release of radioactivity from H111 stone Unit 1 through the storm sewers jnto Niantic Bay. Based on this, and the Tsuruga event, you wanted to know if the Millstone Storm Drain System is " representative 'and allowable".
The requirements of NRR are that during normal reactor operation, including anticipated ojierational occurrences, all major and potentially significant paths for release of radioactive material should be monitoried (R.G.1.21, C.2,( 10 CFR 50, App. A, GDC-64). Plants dre designed, reviewed and Technical Specifications are provided to assure trydt, during normal operation and anti-cipated operational occurrences, all such related paths are monitored.
The HillstDrelease involved a sy tem which had not previously been identified generically as a potential source for release of radioactive materials and, thereforc, had not b6en specifically included as such in plant designs, NRR reviews, or injthe Technical Specifications. The specific system is the turbine lubricating oil drain oil / water separator. Drain water had never, in approximately 10 years of operation at Millstone 1, been observed to drain from the system. Thegadioactive water was actually condensed primary reactor steam, which is used ih older boiling water reactors as sealing steam for the turbine gland seals add for valve stem seals in large steam vahes.
The system overflow drain was connected to a turbine building drain system flantstormdrain. Apparently, a sealing steam which was connected to the/ bypass valve; condensate from this leak accumulated leak occurred in a turbine in the lubricating oil r covery system and flowed to the oil / water separator, resulting in the unmoni red discharge, as described above.
Our preliminary revie indicates the potential for similar leakage at other plants is limited to ider boiling water reactor designs. Newer boiling water reactors util e " clean" steam for sealing systems, with the non-radio-active steam being rovided by auxiliary boilers. Pressurized water reactors utilize cican sec ndary-side steam for sealing systems.
The Office of Inspection and Enforcement is assessing the generic implications of the Millstone 1 event to determine if either a circular or bulletin should be issued to plants having a potential for similar releases.
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NRC P ORM 3181tO/80l NRCM G240 OFFICIAL RECORD COPY
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MEMORANDUM FOR: Peter A. Bradford FROM:
William J. Dircks, Executive Director
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SUBJECT:
MILLSTONEUNIT1RADIOACTIVERELEASEVIASTOPIDRAIN
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On June 21, 1981, the licensee reported an unmonitored release of radioactivity from H111 stone Unit 1 through the storm sewers into Niantic Bay. Based on this, and the Tsuruga event, you wanted to know if the Hillstone Storm Drain System is " representative and allowable".
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Plants are designed and Technical Specifications re provided to assure that during normal operation all effluent release paths are monitored. The Office of Inspection and Enforcement is assessing the' generic implications of the Hillstone Unit 1 event.
It should be noted,tihat pressurized water reactors have a secondary (steam) side isolated from the primary side. Newer boiling water reactors utilize " clean" steam for, seals from auxiliary boilers.
Consequently the unmonitored leak path,at Hillstone 1 may be representative of about 10 to 20 older boiling waterfeactors.
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The requirements of HRR are that during normal operation all potentially radioactive effluent paths are to,be monitored. The investigation of IE is continuing into whether this concern is generic.
A brief description of the circ /
umstances surrounding the Hillstone 1 event and additional relevant infor6ation are provided in the enclosure.
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Willian J. Dircks, Executive Director j
for Operations DISTRIBUTION: SECY OGC J. J. Shea//
Docket TShedlosky 01&E (3)
Contact:
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MEMORANDUM FOR: Peter A. Bradford FROM:
William J. Dircks, Executive Director f
for Operations
SUBJECT:
MILLSTONE UNIT 1 RADI0 ACTIVE RELEASE VIA STORM DRAIN f
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On June 21, 1981, the licensee reported an unmonitored release of radioactivity from Hillstone Unit 1 through the storm sewers into Niantic Bay. Based on this, and the Tsuruga event, you wanted to know if the Millstone Storm Drain System is " representative and allowable".
Plants are designed and Technical Specifications are provided to assure that during normal operation all effluent release paths are monitored. The Office of Inspection and Enforcement is assessing the generic implications of the Millstone Unit 1 event.
It should be noted that pressurized water reactors have a secondary (steam) side isolated from the primary side. Newer boiling water reactors utilize " clean" steam for seals from auxiliary boi-lers.
Consequently the unmonitored leak path at Hillstone 1 may be representative of about 10 to 20 older boiling water reactors.
The requirements of NRR are that during normal operation all effluent paths are to be monitored. The investigation of IE is continuing into whether this concern is generic.
A brief description of the circumstances surrounding the Millstone 1 event and additional relevant information are provided in the enclosure.
f William J. Dircks, Executive Director for Operations DISTRIBUTION: SECY OGC Cont:ct: J. J. Shea Docket TShedlosky 01&E (3)
Ext. 27231 NRC PDR RKermig ACRS (10)
LPDR EJordan SCavanaugh cc:
TERA HThornburg (EDO-10622)
Chairman Palladino NSIC DBangert DNottingham Com4sioner Gilinsky WDircks PStoddart ORB #5 RF Comissioner Ahearne HDenton DLepinski ORB Subject File L. Bickwit, OGC ECase LHiggenbortan TRehm DEisenhut EBlackwood VStello (D.Rathbun,0GC S. Chilk, SE Glainas J01shinski Cornell DCrutchfield GHolahan SHanauer ED0 Dlp'fD/SA JShea KWichman TMurley WJDircks Gr.ainas D
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s MEMORANDUM FOR: Peter A. Bradford FROM:
William J. Dircks, Executive Director for Operations
SUBJECT:
NILLSTONE UNIT 1 RADI0 ACTIVE RELEASE VIA Sf0RM DRAIN
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On June 21, 1981, the licensee reported an unmonitored release of radioactivity from Millstone Unit 1 through the storm smers'into Niantic Bay. Based on this, and the Tsuruga event, you wanted to know f'the Hillstone Storm Drain System is " representative and allowable".
- Plants are designed and Technical Specifications are provided to assure tht during normal operation all effluent release paths are monitored. The Office i-of Inspection and Enforcement is' assessing the generic implications of the Millstone Unit 1 event.
It sh6uld be noted that pressurized water reactors utilize " clean" steam for peals from auxiliary boilers. Consequently, the unmonitored leak path at M111 stone 1 may be representative of about 10 to f
20 older boiling waterfreactors.
The requirements of/NRR are that for during normal cperation all effluent paths are to be p6nitored. The investigation of IE is continuing into whether this concern is generic.
A brief desc/
ription of the circumstances surrounding the Hillstone 1 event and addi ional relevant information are provided in the enclosure.
William J. Dircks, Executive Director for Operations DISTRIBUTION: SECY OGC
Contact:
J. J. Shea Docket TShedlosky 01&E (3)
Ext. 27231 NRC PDR RKermig ACRS (10)
LPDR EJordan SCavanaugh cc:
TERA HThornburg (ED0-10622)
Chairman Falladino NSIC DBangert DNottingham Comissioner Gilinsky WDircks PStoddart ORB #5 RF Comissioner Ahearne HDtaton DLepinski 0RB Subject File L. Bickwit 0GC ECase LHiggenbortan TRehm D. Rathbun, OGC DEisenhut EBlackwood VStello S. Chilk, SECY Glainas J01shinski Cornell DCrutchfield GHolahan SHanauer JShea KWichman TMurley 7
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DISCUSSION OF MILLSTONE UNIT 1 RADI0 ACTIVE RELEASE THROUGH THE STORM DRAIN t
The Millstone 1 4..t returned to low power production on June 17, 1981, followi% an eight and one half month outage (refueling, extensise modifica-tions and turbine repair). With the plant operating at full thermal power, the licensee reported an unplanned release of radioactive water through the storm j
drain system to Niantic Bay during the period Jene 19-22, 1981. The source of i
the leakage was observed to be from one of the curbine bypass valves. Because I
of the insulation on the valve that prevents direct visual observation and l
high radiation levels in the area while at power that restrict personnel access to the valve, it cannot be dotermined whether or not the leakage is due to valve stem seal degradation or other cause.
The radioactive water was released to the storm sewers through a lubricating oil / water separator-water drain. The turbine lubricating oil system includes an oil conditioner to remove water and particulate contaminants.
In addition to oil from the main turbine oil sump, the oil conditioner accepts drains from the oil sump vapor extractor and from several drip pans located beneath hydraulically-actuated valves, such as the turbine bypass valve. Under normal plant operation the water level in the oil separator is nearly constant.
Operators have reported that it is sometimes necessary to add wrter to main-tain water level in the desired range. The water level is visLally checked twice per shift. Abnormal conditions at this separator were first noticed when the roving plant cperator noticed an unusutlly high water level and took corrective action to lower the level to normal by drawing off some of the water to radioactive storage. Subsequently, an operator noticed that the level was overflowing. He traced the water to the storm sewer and obtained water samples at the oil, separator water drain and storm sewer.
Isotopic analysisland radioactivity measurements of the water from the oil separator support' the observed leakage of condensed reactor steam as the source of radioactive water. The total ragioactivity of the water at the only 4.7 x 10 g was reported to be 3 x 10-separator deai microcuries per milliliter but microcuries per milliliter in the storm sewer whera the unmonitored release of radioactivity to the environment had been detected.
Since there was little dilution (no rain) prior to and during the period of 4 x 10-6)the magnitude of the significant reduction (i.e. 3 x 10-2 concern to cannot be explained at this time.
The licensee has sealed the storm drain system, flushed and cleaned it. The flushing water was sent to the plant's radioactive waste handling systems.
Two flushes lowered activity levels in the storm sewer below measurable values.
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2-Water from the separator was measured at 4 gallons per hour and has been diverted to the plant radioactive waste system as plant operation continues uninterrupted at the rated thermal power level. On the basis of measured water flow rate from the oil / water separator, the time since plant startup, and the span of time between water level observations at the oil / water separator, it is estimated that up to 50 gallons of radioactive water could have been dis-charged into Niantic Bay and diluted prior to entering Long Island Sound.
This is the first reported incident at Hillstone 1 involving an unmonitored release of water drained from the oil / water separator during more than 10 years of connercial operation. The total amount of radioactivity released from the plant and diluted in Niantic Bay before entering the waters of Long Island Sound was negligibly small and the effect on the health and safety of the public is insignificant.
The Office of Inspection and Enforcement is continuing its investigation to assess generic implications, if any. However, it should be noted that 1) all pressurized water reactors (PWRs) utilize a primary / secondary coolant system, and 2) newer boiling water reactors (BWRs) use fossil-fired units to generate auxiliary steam. For these plants, the steam for gland seals is " clean", i.e.
nonradioactive - not reactor steam. The specific reactor steam condensate sneak radioactive water to storm sewer path discovered at Hillstone 1 may involve only plants that use reactor steam for gland seals.
In contrast to the Tsuruga incident:
o The release did not go undetected for days at H111 stone 1.
o The operator checked for unplanned rei ase of radioactivity imediate'y when unmonitored drainage of radioactive waste was discovered.
o The incident was reported to H111 stone 1 management and NRC upon discovery.
o Not more than 50 gallons of unmonitored radioactive waste escaped to the environment compared to 500 gpm at Tsuruga.
o The Tsuruga incident resulted from seepage through floor cracks into site drainage systems not known to the operators after radwaste collection tanks had overflowed.
o The Tsuruga incident resulted in measurable radiation exposure to cleanup workers. No measurable Hillstone 1 worker exposure ocurred.
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