ML20057C392

Responds to NRC Re Violations Noted in Insp Rept 50-306/93-15.Corrective Actions:Issued Operations Note, Stating D5/D6 HVAC Sys Essential Support Sys

ML20057C392
Person / Time
Site:	Prairie Island
Issue date:	09/20/1993
From:	Antony D NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9309280302
Download: ML20057C392 (4)

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. tjorthem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401-1927 Telephone (612) 330-5500 September 20, 1993 10 CFR Part 2 Appendix C U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PIANT Docket No. 50-306 License No. DPR-60 Response to Notice of Violation NRC Inspection Report No, 306/93015(DRP)

Removal from Service of Both Trains of DS/D6 Buildinr. HVAC Your letter of August 19, 1993, which transmitted NRC Inspection Report No.

306/93015(DRP), requested a response to a violation. The following is offered in response to the violation.

Violation Technical Specification 3.7.B.6 states that, "one 4 kV safeguards bus (and its associated 480 V buses including associated rotor control centers) or  ;

one 480 V safeguards bus including associated safeguards motor control I centers may be inoperable or not fully energized for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> provided the i redundant 480 V safeguards buses are verified OPERABLE and the diesel l generator end safeguards equipment associated with the redundant train are

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OPERABLE." Technical Specification 3.7.B.1 states, in part, that, "one diesel generator may be inoperable for 7 days provided. (b) all engineering safety features equipment associated with the operable diesel generator are OPERABLE.. "

Contrary to the above, on July 19, 1993, both trains of the DS/D6 building I HVAC system, a necessary attendant system required for operability of the Unit 2, 4 kV and 480 V safeguards buses and emergency diesel generators, were secured for approximately 15-1/2 hours, and the respective Technical Specification limiting conditions for operation were not applied and followed.

This is a Severity Level IV Violation (Supplement I).

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• 4 Northem States Power Company USNRC September 20, 1993 Page 2 l

Response

Backcround l

l A description and background of the event can be found in NRC Inspection l Report No. 50-306/93015.

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l The following provides further information regarding the " engineering-based thought process" used to arrive at the conclusion that removing from cervice l

HVAC associated with the DS and D6 Diesel Generator building was acceptable. ,

Questions regarding the need for continuous operation of the D5/D6 building HVAC system arose during the dual unit outage ^(end of 1992) prior to turnover of the new diesel systems to the plant. During that time, D5 and D6 were considered "available" sources to Buses 25 and 26 in conjunction 'with the outage safety assessment plan. Discussions with the project engineering group and the system engineer focused on the Design Report and the HVAC system's-effect on safeguards equipment operability. It was concluded at that time that

1) safeguards bus operability with regard to room cooling is a function of room temperature, not the operating status of the ventilation fans, and 2) approved Alarm Response procedures provided adequate time and guidance to the l operations staff and were an acceptable mechanism to start the fans if their operation were required.

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The decision to turn off both trains of HVAC on. July 19, 1993 was based on l this prior engineering judgement.

l Reason for the violation The primary reasons for the violation are (1) an insufficient formal analysis on the D5/D6 building rooms substantiating the acceptability of operation without forced ventilation, (2) insufficient translation of DS/D6 design l information into procedural guidance for the operations staff, (3) inadequate i guidance'to the operators to implement the definition of operability relative to essential support equipment, and (4) lack of detailed condition-specific procedures, and operator training on those procedures, when using manual operator actions to substitute for automatic equipment response.

l Contributing reasons for the violation are 1) the lack of clear definition of l the terms "AVAILABLE" and "0PERABLE", where the term "AVAILABLE" is typically l used in the shutdown safety assessment, and the term "0PERABLE" is used for.

Technical Specification compliance, 2) a mindset of past practices, carried over from the D5/D6 construction period.

Corrective steos taken and results achieved The.immediate corrective action taken was to issue an " Operations Note" stating that the D5/D6 HVAC systems were essential support systems and one set of the systems for each train was to be operated continuously .

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' j Northem States Power Company j USNRC September 20, 1993 Page 3 On July 23 the plant Operations Committee reviewed the question of operability of the D5/D6 equipment with no support fans running. Using the guidance provided in Generic Letter 91-18, the Operations Committee determined that ,

operability should be based on room temperature, and not whether the fans were l running. There are several alarms to indicate the need for ventilation, and j the OC concurred that there would be adequate time to respond using Alarm i Response procedures. The Operations Committee concurred that the electrical )

equipment was operable for the 15-1/2 hours in question.

After the Operations Committee meeting, 1) a Daily Order was issued addressing l all safeguards HVAC and equipment operability, directing operator response to the appropriate Technical Specification action statement upon a HVAC system being out of service, and 2) letters were issued to, and a management meeting was held with, the plant engineering staff on the importance of essential support equipment and its impact on the operability of parent components, and on the specific requirements for using manual operator action in place of automatic equipment action.

A formal analysis of D5/D6 building heatup with no ventilation was initiated to support future operation.

Procedures associated with D5/D6 HVAC were revised to reflect that it is unacceptable to have both sets of HVAC associated with each train inoperable without entering the appropriate Technical Specification action statements.

l The ections taken for the ventilation systems are effective in meeting l Technical Specifications for essential support system operability. l Corrective steps to avoid further violations Further violations relating to essential support equipment will be avoided by

, implementing the following act. ions:

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! a. A review of the DS/D6 Design Reports will be performed to assure there are no other occurrences of insufficient translation of design information into operating procedures,

b. The term "AVAILABLE" will be clearly defined to apply only to shutdown safety assessment and not relating to operability determination of l equipment. l

c. The guidance provided in Generic Letter 91-18 will be placed in procedures. Specifically, procedures will provide:

- guidance for addressing operability assessments, .

- guidance for use of manual operator actions replacing automatic equipment actions, and

d. Procedures will also be issued to provide guidance regarding the l

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Nodhem States Power Company .

USNRC September 20, 1993 Page 4 I

definition and treatment of essential support equipment. This guidance l will define which support systems are necessary to ensure the operability I of main systems and components that perform specified safety functions. 1 l

e. Training on the above procedures will be provided to the Operations and Engineering staff.

Date when full compliance will be achieved Full compliance was achieved at 16:05 on July 19, 1993, when the DS/D6 HVAC system was returned to service.

In this response, we have made several new NRC commitments: they are items a, b,c, d , and e , contained under the heading " Corrective steps to avoid further violations" Please contact Jack Leveille (612-388-3962, Ext. 4662) if you have any questions related to our response to the subject inspection report.

[j'S y . p% s4 Doug as D Antony c/

Vice President l Nuclear Generation l

! c: Regional Administrator III, NRC

Senior Resident Inspector, NRC

! NRR Project Manager, NRC

! J E Silberg i

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