ML20149G852
| ML20149G852 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/10/1997 |
| From: | Reyes L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Kingsley O TENNESSEE VALLEY AUTHORITY |
| Shared Package | |
| ML20149G854 | List: |
| References | |
| 50-327-97-05, 50-327-97-5, 50-328-97-05, 50-328-97-5, EA-97-232, NUDOCS 9707240098 | |
| Download: ML20149G852 (5) | |
See also: IR 05000327/1997005
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July 10,1997
EA 97 232.
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Tennessee Valley Authority
ATTN: Mr. Oliver D. Kingsley, Jr.
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President, TVA Nuclear and
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Chief Nuclear Officer
6A Lookout Place
1101 Market Street
Chattanooga, TN 37402 2801
SUBJECT:
(NRC SPECIAL INSPECTION REPORT NOS. 50 327/97 05 AND 50 328/97 05)
Dear Mr. Kingsley:
This refers to the special inspection conducted on March 24 through
May 22, 1997, at the Sequoyah facility. The purpose of the inspection was.to
review asmets of the Unit 1 reactor coolant system (RCS) inadvertent drain
down whic1 occurred on March 24, 1997. The results of the inspection were
sent to'you by letter dated May 27, 1997. An open, predecisional enforcement
conference was conducted in the Region II office on June 27, 1997, with you
and members of your staff, to discuss the apparent violations' the root
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causes, and corrective actions to preclude recurrence. A list of' conference
attendees-and copies of the Nuclear Regulatory Commission's (NRC) and
Tennessee Valley Authority's (TVA) presentation materials are enclosed.
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Based on the information developed during the insmction and the information
that was provided during the conference, the.NRC 1as determined that
violations of NRC requirements occurred. The violations are cited in the
enclosed Notice of Violation (Notice), and the circumstances surrounding them
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are described in detail in the subject inspection report.
The RCS. drain down event occurred during an evolution to reduce pressurizer
level to 25%, following plant ' shutdown. You stated that the evolution
included a rapid RCS depressurization which caused voids in the reference leg
for the cold calibrated pressurizer level instrument and erroneous indication
of pressurizer level in the control room. Operators relied on the erroneous
. indication and inadvertently drained the pressurizer and subsequently the RCS
to a. level just below the top of the reactor vessel head.
Two violations were identified as a result of the event. Violation A involved
two examples of the failure to identify and take adequate corrective actions
for a significant condition adverse to quality.
In the first example of
Violation A TVA failed to identify and correct deficiencies in the control of
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RCS.. inventory during a reduction of pressurizer level. The root cause of this
example of the violation was the failure of TVA management to provide the
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9707240098 970710
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proper combination of operator training and procedural guidance necessary to
identify the discrepancy in the pressurizer level indication. As a result,
although the operators appeared to be attentive to their duties and were
monitoring the hot calibrated and cold calibrated pressurizer level
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instruments, they failed to identify a malfunction of the cold calibrated
pressurizer level instrument.
It is also of particular significance that
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although the operators questioned the conflicting indications including
receiving and acknowledging alarms in the control room indicating letdown
isolation and low pressurizer level, they failed to stop the evolution
promptly and determine if further actions were necessary to effectively
analyze the conflicting level indications. The operators continued the
pressurizer drain down until a reactor operator, assuming shift duties after a
shift change, noted the discrepancy between pressurizer level and a reactor
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vessel level indication and initiated corrective actions. A weakness was also
noted in implementation of corrective actions for a loss of RCS inventory
control in 1993. TVA had determined that procedural controls for RCS
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inventory control should be enhanced, based on a previous event review for a
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1993 Sequoyah Unit 1 inadvertent RCS drain down. These controls included
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measures to ensure (1) positive inventory control, (2) use of a pressurizer
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level correction curve which showed the relationship between the hot and cold
calibrated instruments, and (3) use of multiple independent channels to
confirm the accuracy of instruments relied on during the drain down.
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However, the corrective action for the 1993 event focused on
3recluding
inventory control events only at low pressurizer levels and t1e procedure for
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operatinn in normal pressurizer level bands was not revised.
In the second example of Violation A, TVA failed to identify that two previous
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backfills'of the pressurizer level instrument reference legs that occurred
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after rapid RCS depressurization evolutions were evidence of the pressurizer
level instrument's susceptibility to voiding during rapid RCS
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depressurization. As a result, corrective actions were not taken to ensure
that adequate indication of RCS inventory was available during reductions in
RCS inventory.
Violation B involved failures to log correctly and accurately the plant's
status as required by plant operating procedures.
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The NRC is concerned that, when faced with the discrepant indications, the
operators failed to take immediate corrective actions to determine actual RCS
inventory. The operators also failed to take precautionary steps, such as
consulting the pressurizer level correction curve which was available in the
control room, or implementing positive inventory controls prior to commencing
the RCS drain down evolution.
In addition, the NRC is concerned that previous
opportunities to identify the level instrument failure mode were lost when you
failed to evaluate the circumstances surrounding two previous cold calibrated
reference leg backfills due to voiding in the pressurizer level reference leg.
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The March 1997 Unit 1 RCS drain down event is also of particular concern to
the NRC because of the similarity of this event to the 1993 Unit 1 RCS drain
down. Although, the actual safety consequences of both events were low, the
recurrence of this event, as a result of operator errors and failure to
provide adequate procedural or training guidance, represents a significant
regulatory concern.
In light of the potential consequences of the loss of
reactor coolant inventory, licensees should take aggressive action to ensure
that appropriate procedures and training are provided to ensure that RCS
inventory is effectively controlled, particularly during evolutions involving
planned reductions in RCS inventory.
Additionally, corrective action
effectiveness has been an ongoing concern at Sequoyah. Therefore, the
violations have been categorized in the aggregate in accordance with the
" General Statement of Policy and Procedures for NRC Enforcement Actions"
(Enforcement Policy). NUREG 1600, as a Severity Level III problem.
In accordance with the Enforcement Policy, a base civil penalty in the amount
of $55,000 is considered for a Severity Level III problem occurring after
November 12, 1996.
Because your facility has
enforcement actions within the last two years, peen the subject of escalated
the NRC considered whether
credit was warranted for Identification and Corrective Action in accordance
with the civil penalty assessment process described in Section VI.B.2 of the
NRC determined that credit was warranted for
Identification in that the violations were identified by your staff. At the
conference, your staff stated that corrective actions taken or initiated
included the following:
(1) reinforce management expectations of Operations
personnel: (2) revision of the general operating procedure to control backfill
of the cold calibration level channel reference leg, ensure use of multiple
level indications during drain down and ensure positive inventory controls:
(3) enhanced training and evaluation of crew performance: (4) self-assessment
of Operations including an independent assessment conducted by peers from
other operating plants. Based on the above, the NRC determined that the
corrective actions appeared to be comprehensive and that credit was warranted
for the factor of Corrective Action.
Therefore, to encourage prompt identification and comprehensive corrective
actions for violations, I have been authorized, after consultation with the
Director, Office of Enforcement, not to propose a civil penalty in this case.
However, significant or further repetitive violations in the future could
result in a civil penalty.
'Two Severity Level III problems and proposed civil penalties of $50,000 each
were issued on December 24,1996. (EA 96 414) for inadequate corrective actions
related to maintenance of reactor trip breakers and other equipment. A Severity
Level III violatien and proposed civil penalty of $50,000 was issued on November 19,
1996, (EA 95-269) related to fire protection program deficiencies. A Severity
Level II violation and proposed civil penalty of $80,000 were issued on February 20,
1996, (EA 95 252) related to employee discrimination in Department of Labor Case
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You are required to respond to this letter and should follow the instructions
specified in the enclosed Notice when preparing your response.
In your
response, you should document the specific actions taken and any additional
actions you plan to prevent recurrence of the violation. After reviewing your
response to this Notice, including your proposed corrective actions and the
results of future inspections, the NRC will determine whether further NRC
enforcement action is necessary to ensure compliance with NRC regulatory
requirements.
In accordance with 10 CFR 2.790 of the NRC's " Rules of Practice," a copy of
this letter and its enclosure will be placed in the NRC Public Document Room.
Sincerely.
Original signed by
Bruce S. Mallett for
Luis A. Reyes,
Regional Administrator
Docket Nos. 50-327, 50 328
Enclosures:
2. NRC Presentation Materials
3. TVA Presentation Materials
4. List of Attendees
cc w/encls:
0. J. Zeringue, Senior Vice
President
Nuclear Operations
Tennessee Valley Authority
6A Lookout Place
1101 Market Street
Chattanooga, TN 37402-2801
Jack A. Bailey, Vice President
Engineering & Technical Services
Tennessee Valley Authority
6A Lookout Place
1101 Market Street
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Chattanooga, TN 37402 2801
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cc w/encls: (See page 5)
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TVA.
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cc w/encls cont'd:
M. Bajestani
Site Vice President
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Sequoyah Nuclear Plant
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Tennessee Valley Authority
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P. O. Box 2000
Soddy Daisy, TN 37379
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General Counsel
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Tennessee Valley Authority
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400 West Summit Hill Drive
Knoxville, TN 37907.
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Raul R. Baron, General Manager
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Nuclear Assurance and Licensing
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' Tennessee Valley Authority
4J Blue Ridge
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1101 Market Street
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Chattanooga, TN
37402 2801
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Pedro Salas, Manager
Licensing and Industry Affairs
Tennessee Valley Authority
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4J Blue Ridge'
1101 Market Street
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Chattanooga, TN 37402 2801
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Ralph H. Shell, Manager
Licensing and Industry Affairs
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Sequoyah Nuclear Plant
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P. O. Box 2000
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Soddy Daisy TN 37379
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J. T. Herron, Plant Manager
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Sequoyah Nuclear Plant
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Tennessee Valley Authority
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P._0. Box 2000
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Soddy Daisy, TN 37379
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Michael. H. Mobley, Director
Division of Radiological Health
3rd Floor, L and C Annex
401 Church Street
Nashville, TN 37243-1532
County Executive
Hamilton County Courthouse
Chattanooga, TN 37402