05000346/LER-1994-001, :on 940608,discovered That TS Safety Features Actuation Sys Setpoint Required in Mode 6,refueling Calibr at Greater than Required Setpoint.Caused by Incorrect Evaluation.Trip Setpoints Will Be Adjusted

:on 940608,discovered That TS Safety Features Actuation Sys Setpoint Required in Mode 6,refueling Calibr at Greater than Required Setpoint.Caused by Incorrect Evaluation.Trip Setpoints Will Be Adjusted

ML20070F044
Person / Time
Site:	Davis Besse
Issue date:	07/08/1994
From:	Miller D, Jeffery Wood TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AB-94-0025, AB-94-25, LER-94-001, LER-94-1, NP-33-94-002, NP-33-94-2, NUDOCS 9407180145
Download: ML20070F044 (5)

LER-1994-001, on 940608,discovered That TS Safety Features Actuation Sys Setpoint Required in Mode 6,refueling Calibr at Greater than Required Setpoint.Caused by Incorrect Evaluation.Trip Setpoints Will Be Adjusted

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x)
3461994001R00 - NRC Website

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TOLEDO. OHIO 43652 0001 AB-94-0025 NP-33-94-002 Docket No. 50-346 License No. NPF-3 July 8, 1994 United States Nuclear Regulatory Commission Document Control Desk Vashington, D. C.

20535 Gentlemen:

LER 94-001 Davis-Besse Nuclear Power station, Un3t No. 1 Date of Occurrence - June 8, 1994 i

Enclosed please find Licensee Event Report 94-001, which is being submitted to provide 30 days written notification of the subject occurrence. This LER is 3

being submitted in accordance with 10 CFR 50.73(a)(2)(1)(B).

V truly yours, w

I

~ Jo n K. Vood P ant Manager Davis-Besse Nuclear Power Station 1

JKV/ eld Enclosure ec:

Mr. John B. Martin Regional Administrator USNRC Region III Mr. Stan Stasek DB-1 NRC Sr. Resident Inspector Utility Radiological Safety Board 9407:e0145 9407o3 PDR ADDCK 05000346

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DOCKET NUMBER (21 PAGE (3) 05000 -346 10F 03 Davin Rocce %clea* Pnver Starinn. Unit'No. 1 TITL1 (a)

Inoperable Saferv Features Actuation System Instrument Strines EVENT DATE (5)

LER NUMBER (6l REPORT NUMBER (7)

OTHER FACILITIES INVOLVED (8)

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LEVEL (10) 99 20 405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii)

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LICENSEE CONTACT FOR THIS LER (12) sAME TELEPHONE NUMBER Pcluce Area Cooe)

Dale L. Miller. Senior Fncineer - Licensine (419) 321-7264 I'

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

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ABSTRACT (Limit to 1400 spaces. Le., approximately 15 single-spaced typewritten imes) (16)

On June 8, 1994, with the Reactor operating at approximately 100 percent Rated Thermal Power (RTP), it was discovered that a Technical Specification (TS)

Safety Features Actuation System (SFAS-JE) Channel 4 trip setpoint required in Mode 6, Refueling had been calibrated at greater than the required setpoint during past Refueling operations. Technical Specification 3.3.2.1, SFAS Instrumentation, requires a minimum of 3 high containment radiation instrument strings operable. The trip setpoint and allovable value for a containment radiation string is required to be less than 2 times background. The background radiation readings at the location of RE2007 are approximately 2 to 3 millirem per hour. The containment radiation high setpoint for RE2007 during Mode 6, Refueling operations had been calibrated at 15 mrem /hr.

1 Channel 2 SFAS radiation instrument string was inoperable during core

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alterations conducted between October 1 and 7, 1984. Vith the channel 4 setpoint incorrectly calibrated, only 2 SFAS containment high radiation strings were operable. The cause of this occurrence is incorrect evaluation of the required setpoint implemented as a result of a facility change in 1982.

This occurrence has had no impact on the health and safety of the public or plant personnel. Background radiation for RE2007 was confirmed to be approximately 2.5 mrem /hr on July 1, 1994.

Prior to conducting core alter 7tions or movement of fuel in containment, trip setpoints vill be adjusted, as necessary to comply with Technical Specifications.

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uaNAGEMENT AND BJDGET. Wa$mNGTON, DC 70$C3 F ACILfTY NAME 08 DOCKET NUMBER (n LgR NUMBER qs) pagg g3, RAR 05000 -346 02 or 03 Davis-Besse Unit No. 1

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ana> v n Description of Occurrence:

i On June 8, 1994, at Davis Besse Nuclear Power Station (DBNPS) with the Reactor operating at approximately 100 percent Rated Thermal Power (RTP), it was discovered that a Technical Specification (TS) Safety Features Actuation System (SFAS-JE) setpoint required in Mode 6, Refueling had been calibrated at i

greater than the required setpoint during past Refueling operations. This i

discrepancy vas. discovered during the performance of a Systems Based-2 Instrument and Control Inspection by DBNPS Independent Safety Engineering.

i TS 3.3.2.1,.SFAS Instrumentation, requires a minimum of 3 high containment J

radiation instrument strings operable during core alterations or movement of irradiated fuel within containment to be able to automatically close the containment purge and exhaust isolation valves.

The Trip Setpoint and Allovable Value for a containment radiation string is required to be less than 2 times background at Rated Thermal Power (RTP).

The SFAS channel 4 (RE2007) radiation monitor is installed in containment during refueling operations.

Backgcound radiation readings in containment at the location of RE2007 at RTP' are approximately 2 to 3' millirem per hour (mrem /hr). The containment j

radiation high setpoint for RE2007 during Mode 6,' Refueling operations had been calibrated at 15 mrem /hr. The setpoints for the other 3 containment high radiation instrument strings meet the requirement of Jers than 2 times background.

l l

Research into the operability of the other three channels of SFAS high radiation instrument strings revealed that SFAS channel 2 (RE2005) was also inoperable during core alterations conducted from October 1, 1984 until l

October 7, 1984.

Radiation instrument RE2005 was inoperable because readings i

taken during the channel calibration of the SFAS channel were out.of tolerance. The detector was replaced and declared operable on l

October 11, 1984.

l l

Since only 2 channels of SFAS high radiation instrumentation were operable during core alterations and Technical Specification require a minimum of three channels, the Technical Specifications were inadvertently violated during this period. This LER is being submitted in accordance with 10CFR50.73(a)(2)(1)(B).

1 Designation of Ap' parent Cause:

l l

A plant design change implemented by Facility Change Request (FCR) 82-0034 l

established fixed setpoint values for each individual instrument string.

These values were based on an assessment of the fuel handling accident found l

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Designation of Apparent Cause (Continued):

in the Safety Analysis Report. The Safety Evaluation for FCR 82-0034 calculated the dose rate at RE2007 when located in containment as a result of the fuel handling accident. Conservatively, 25 percent of this value was added to the estimated background in containment when the reactor was shutdown. The final setpoint value was 15 mrem /hr. The Safety Evaluation for FCR 82-0034 i

l incorrectly assumed the background radiation for RE2007 was approximately 200 l

to 300 mrem /hr at RTP and the 15 mrem /hr setpoint would not approach the requirement of less than 2 times background. Therefore, the cause of this occurrence is incorrect evaluation of the required setpoint.

Analysis of Occurrence:

l This occurrence has had no impact on the health and safety of the public or l

plant personnel. The setpoint of 15 mrem /hr for isolation of containment is i

conservative with respect to 10 CFR 100 offsite dose guidelines.

The fuel handling accident described in the Updated Safety Analysis Report (USAR) takes no credit for automatic enntainment isolation. Therefore, the consequences of a postulated fuel, handling accident inside containment with the inoperable channels are bounded by the USAR analysis, i

l

Corrective Actions

l On July 1, 1994, background radiation dose rate measurements were taken at the l

location of RE2007 in containment during refueling operations.

The background radiation reading at approximately RTP vas confirmed to be approximately 2.5 mrem /hr.

Prior to conducting core alterations or movement of fuel in containment, trip setpoints vill be adjusted, as necessary, to comply with l

Technical Specifications.

Failure Data:

i Licensee Event Report 90-012 was submitted on August 13, 1990 for a non-conservative SFAS containment high radiation setpoint, at 100 percent RTP.

l However, there have been no LERs in the -last seven years for incorrect SFAS radiation setpoints in Mode 6.

NP-33-94-002 PCAO No. 94-0514

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