ML20087L310

Ao:On 740821,recheck of Control Panel Indicated Above Normal Operating Pressure & Water Level Conditions Existed in Blowdown Evaporator.Caused by Steam Leaking at Steam Supply Control Valve

ML20087L310
Person / Time
Site:	Point Beach
Issue date:	08/30/1974
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20087L295	List: ML20087L293 ML20087L310
References
NUDOCS 8403270133
Download: ML20087L310 (3)

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WISCORSin Electitc eaaracoueur 231 WEST MICHidAN,MI1.WAUKEE, WISCONSIN 53201 Q L u t y$ Y y,*fj

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\ August 30, 1974

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Mr. Edson G. Casa, Deputy Director Directorate of .bii;ensing t; U. S. Atomic Energy Commission

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Washington, D. C. ~20545

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Dear Mr. Caso:

p DOCKET NOS. 50-266 AND 50-301 POINT BEACH NUCLEAR PLAUT UNSCHEDULED RADIOACTIVITY RELEASE FROM _B_ LOWDOWN EVAPORATOR This letter is to report the details of an abnormal occurrence at the Point Beach Nuclear Plant,, Units 1 and 2, Facility Operating License Nos. DPR--24 and DPR-27, as defined g(

by Section 15.1.a.C of the Technical Specifications. This writ-ten report, filed in'accordance lvrith Section 15.6.6.A.2 of the '}

Technical Specifications, follows an oral report on the subject to Mr. Dwane Boyd of Region III Regulatory bperations on August 21, 1974, per Section 15.6.A.1 of the Point Beach Nuclear Plant Technical Specifications. I y

At 2:30 A.M. on August 21, 1974, the radioactive waste @

system 35 gpm b1osdown evapo'.ctor was, shut down following a period

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of normal operation. The control valve supplying steam to the evaporator was closed remotely from the evaporator control panel. 9 Shortly therdafter, when normal cooldown temperatures and pres-sur6s were observed for the evaporator, the service water cooling supply to the evaporator was also secured. In later reviewing this series of events, the operator came to the conclusion that following.the final shutdown of the evaporator he failed to reset all annuncintor alarms on the control panel before leaving the area.

The operator then continued with other shift duties until approximately 3:30 A.M. when a recheck-of the control panel indi-p cated that above normal operating pressure and' water level condi- ,

tions existed in the evaporator. Cooling water was immediately returned to the unit and the evaporator was againcooled to its l

, shutdown condition. The rise in the evaporator pressure and tem-perature was later traced to steam leaking at the unit's steam supply control valve. The inleakage was stopped by closing the .

upstream manual isolation valve at the control valve. .

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Mr. Edson G. Case August 30, 1974 l '

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A local inspection of the evaporator relief valves verified that both valves had lif ted during the pressure tran-sient. This was confirmed by an examination of evaporator  ;

temperature and pressure recording charts which showed a 50 '

psig pressure over a 30 minute period with five " spikes" in-dicating valve lifting. i Releases from the evaporator relief valves are un-monitored. However, under normal stable operation, such re-1casco are expected to be extremely infrequent events and, indeed, none has been experienced to date. Radiation monitors i capable of withstanding the thermal shock, high temperature and humidity associated with this type of service are not, to the best of our knowledge, available at this time.

To assess the magnitude of the radioactive release from the blowdown evaporator, a sample of the evaporator bot-toms was taken, boiled off and its steam's isotopic concentra- i tions analyzed. The following table indicates the results: g Concer.tration Quantity Released Isotopo (uc/ml) UC1  ;

H-3 5.04 x 10-2 899 I-131 7.39 x 10-5 1.32 f Xc-133 9.16 x 10-4 16.3 The mass of steam released was based upon five lift-ings of the relief valve. Each lifting operation reduced the evaporator pressure from the 50 psig blowoff pressure to the valve's rescating pressure of 43 psig for a total steam release of 39.25 pounds.

The analysis indicates that the radioactivity released as a result of this occurrence is negligible and does not con-stitute an exposure at the site boundary. We believe there was no significant risk to the health and safety of the public occasioned by this event. '

To prevent a recurrence of this event, the following measures have been taken: ,

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A modification request has been issued to install a high temperature alarm which will annunciate in the event a I

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O Mr. Edson G. Case August 30, 1974 blowdown evaporator relief valve lifts and the temperature of the relief valve discharge piping is raised.

2. A modification request has been issued to install a high pressure alarm on the evaporator, which device also closes the steam supply valves to the unit.

3. The operating procedure for the evapora-tor is under review. A step will be in-cluded in the shutdown phase of operation to effect more positive steam isolation to the evaporator by means of a manual isolation valve rather than the control valve.

4. The operations Superintendent has reviewed with all his personnel the necessity of resetting all annunciator alarms on the evaporator panel fcllowing shutdown or similar operations.

Very truly yours,

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Sol Burstein Execu ive Vice President cc: Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations, Region III -

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