ML19347C452
| ML19347C452 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 09/23/1977 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Grocer R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8011190461 | |
| Download: ML19347C452 (1) | |
Text
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NUCLEAR REGULATORY COMMisslON f ':f>*"6i E
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Yankee Atomic Electric Company or ATTN: Mr. Robert H. Groce I
Licensing Engineer 2
20 Turnoike Road i
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Westborough, Massachusetts 01581
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Gentlemen:
The enclosed IE Circular 77-13 is fontarded to you for information.
If there are any questions related to your understanding of the suggested actions, please contact this office.
Sincerely,
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Boyce H. Grier Director
Enclosure:
IE. Circular 77-13 cc w/ encl:
H. Autio, Plant Superintendent Donald G. Allen, President O
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20555 IE Circular 77-13 Date:
September 23, 1977 Page 1 of 3 REACTOR SAFETY SIGNALS NEGATED DURING TESTItiG On July 12, 1977, the Commonwealth Edison Ccmpany reported that while conducting a surveillance test at Zion Unit 2, test signals were simul-taneously injected into several sensors which affected both protection and control systems.
Injection of these test signals resulted in:
(1) the loss of instrument indications for the affected protection anc' control systems, (2) the loss of autcmatic control capability for the affected control systems, and (3) the loss of automatic protection capability for the affected protection systems.
f At the time of the event, the unit was in a hot shutdown condition and preparations for start-up were underway.
Station management decided to perform a surveillance test of the reactor protection logic circuitry.
l A combination of test procedure inadequacies and the failure to follow
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prescribed administrative controls related to instrumentation testing led to the insertion of test signis which replaced the actual signals fr.om three pressurizer water level sensors, three water level sensors in each of the four steam generators, four pressurizer pressure sensors and three flow sensors in each of the primary coolant loops.
The test signals had been inserted for approximately 40 minutes when, due to
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unexpected indications of the main coolant pump seal flow rate and other anomalous indications, the operator requested that the test l
observed that the pressurizer water level 'had dropped below the range signals be removed. When the test signals were removed, it was l
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of indication.
The drop in pressurizer water level resulted from the pressurizer water level test signal being slightly higher than the autenatic pressurizer level control set point.
In response to this condition the charging pump flow was automatically reduced to the minimum pump flow rate, which was maintained until the test signals were remo'.ed.
During this 40 minute period the letdown flow remained constant.
Consequently, the rate at which coolant was being removed frcm the prinary coolant system was approximately 75 gpm greater than the rate at which coolant was being returned to the system. Approximately 5300 gailens of water were required to bring the pressurizer water level back to its original level of 22 percent.
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'O IE Circular 77-13 Date:
September 23, 1977 Page 2 of 3 As mensioned above, operator action in response to other available instrumention indications terminated the event.
Subsequent investiga-tion by the licensee revealed that no damage to plant equipment was sustained during or after the event.
This incident represents an example of an event which resulted from a series of errors involving lax management control and improper attentice l
of plant personnel to established procedures.
1 All holders of operating licenses should be aware of the potential for adverse operational events which can occur during performance of parti-cular surveillance tests.
For example, if an excessive number of safety sensors are disabled simultaneously as was the case in this event, automatic action may no+ occur as intended.
Care must be taken to assure that test signals do not negate automatic initiation of protection systems.
It is recommended that the following considerations be incor-parated in your reviews of this matter.
1 Facility procedures should specifically identify the limitations and restrictions which are required for each mode of operation during which testing or surveillance activities may be conducted such that required safety protection systems will remain operable in accordance with the facility Technical Specifications.
2.-
In order to provide additional assurance that required-safety related capabilities of plant systems are not defeated during testing or surveillance activities, training programs for opera-
'l tions and craft personnel should include sufficient information to assure an indepth understanding of system functions, system interactions, and Technical Specification requirements.
3.
Management controls should be strengthened as necessary to assure adherence to administrative procedures involving reviews, approvals, and ccmmunication between plant supervi-sion, operators and craft personnel performing testing and surveillance activities.
Such controls should consider the
" man-machine" interfaces, and should assure that the human ccaponent of this pair is not overburdened.
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IE Circular 77-13 TJ Date: September 23, 1977 5
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flo written response to this Circular is required.
If you require i
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additional information regarding this matter, contact.the Director
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IE inspectors will review Q
this natter with licensees during future inspections.
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Enclosure:
List of IE Circulars Issued i,n 1977
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