Information Notice 1987-17, Response Time of Scram Instrument Volume Level Detectors

Response Time of Scram Instrument Volume Level Detectors

ML031130725
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, 05000371, Zimmer, 05000383, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	04/07/1987
From:	Jordan E NRC/IE
To:
References
IN-87-017, NUDOCS 8704030045
Download: ML031130725 (5)

SSINS No.: 6835 IN 87-17 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 April 7, 1987 IE INFORMATION NOTICE NO. 87-17: RESPONSE TIME OF SCRAM INSTRUMENT VOLUME

LEVEL DETECTORS

Addressees

All General Electric boiling water reactor (BWR) facilities holding an

operating license or a construction permit.

Purpose

This notice is to alert addressees of the potential for long response times in

level detection instruments used to measure the water volume in the scram

discharge instrumented volume of BWRs. These instruments are intended to cause

a timely scram prior to filling of the scram discharge volume (SDV).

Recipients are expected to review the information for applicability to their

facilities and consider actions, if appropriate, to preclude similar problems

occurring at their facilities. However, suggestions contained in this

information notice do not constitute NRC requirements; therefore, no specific

action or written response is required.

Background

On June 28, 1980 during a routine shutdown of the Browns Ferry Unit 3 reactor, a manual scram from about 36 percent power failed to insert approximately 40

percent of the control rods. The root cause was isolated to a problem with the

SDV header. The followup to this event at other BWRs revealed a number of

deficiencies that were discovered with the SDV headers.

The corrective measures to this problem are divided into a short-term program

and a long-term program. The short-term actions were implemented by IE

Bulletins 80-14 and 80-17 and their supplements. The long-term program was

addressed by a Generic Safety Evaluation Report (SER) dated December 1, 1980.

The objective of the long-term program was the improvement of the SDV design.

(SDV design details vary from plant to plant.) One of areas of concern

addressed by the long-term program was that the reliability of the float

switches in the instrumented volumes needed to be improved. The recommended

solution was the addition of redundant and diverse water level sensors.

Description of Circumstances

More recently, the NRC reviewed the licensee's corrective actions taken at the

Browns Ferry units as a result of the earlier event and identified a

potentially generic concern with the response time of the level detectors for

870

IN 87-17 April 7, 1987 the instrumented volume. As an interim solution to issues raised by the 1980

event, the licensee installed a circuit to scram the reactor upon sensing low

air header pressure. As a long-term fix, the licensee then installed differential

pressure (DP) detectors as a diverse means of sensing a full instrumented

volume and causing a scram. The DP detectors back up the float switches in the

instrumented volume that also can cause a scram.

Testing by the licensee showed a response time of about 70 seconds for the

installed DP detectors in the instrumented volume. This was unacceptable (see

discussion). The licensee replaced the DP detectors with resistance-temperature

detectors (RTDs). Comparison of the response time of the RTDs with the float

switches showed that the float switches had a response time of about 20 seconds.

This was also unacceptable. The licensee has consequently upgraded the scram

on low air header pressure instrumentation to a permanent installation that is

environmentally qualified and covered by technical specifications.

Discussion:

Although the SER did address the minimum capacity of the SDV, the potentially

generic concern is that the SER did not address the response time of the level

detection instruments in the instrumented volume. There is a direct correlation

between the response time of these instruments and the capacity of the SDY.

Under degraded air conditions, the scram outlet valve for each control rod

drive may leak as much as 5 gpm to the SDV without rapid rod motion. The

extent and timing of water accumulation in the SDV can slow or stop rod

insertion on scram. (GE has experimentally shown that if water has accumulated

to about 85 percent or greater of the SDV header volume, scram is effectively

stopped.) The instrumented volume level instrumentation are intended to

generate a timely scram signal such that the reactor is scrammed before water

leaking by the scram outlet valves fills the SDV.

No specific action or written response is required by this information notice.

If you have questions about this matter, please contact the Regional Adminis- trator of the appropriate NRC regional office or this office.

ard Jordan, Director

Divis f Emergency Preparedness

and ngineering Response

Office of Inspection and Enforcement

Technical Contacts: Eric Weiss, IE

(301) 492-9005 Charles Patterson, NRC Resident Inspector

Browns Ferry Nuclear Power Plant

(205) 729-6196 Attachment:

List of Recently Issued IE Information Notices

- Attachment 1 IN 87-17 April 7, 1987 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

87-16 Degradation of Static "O" 4/2/87 All LWR facilities

Ring Pressure Switches holding an OL or CP

87-15 Complaince with the Posting 3/25/87 All power reactor

Requirements of Subsection facilities holding

223b of the Atomic Energy a CP and all firms

Act of 1954, as Amended supplying components

or services to such

facilities

87-14 Actuation of Fire Sup- 3/23/87 All power reactor

pression System Causing facilities holding

Inoperability of Safety- an OL or CP

Related Ventilation Equipment

86-106 Sup. 2 Feedwater Line Break 3/18/87 All power reactor

facilities holding

an OL or CP

87-13 Potential for High Radiation 2/24/87 All power reactor

Fields Following Loss of facilities holding

Water from Fuel Pool an OL or CP except

Fort St. Vrain.86-106 Sup. 1 Feedwater Line Break 2/13/87 All power reactor

facilities holding

an OL or CP

87-12 Potential Problems With 2/13/87 All power reactor

Metal Clad Circuit Breakers, facilities holding

General Electric Type AKF-2-25 an OL or CP

87-11 Enclosure of Vital Equipment 2/13/87 All power reactor

Within Designated Vital facilities holding

Areas an OL or CP

87-10 Potential for Water Hammer 2/11/87 All BWR facilities

During Restart of Residual holding an OL or CP

Heat Removal Pumps

87-09 Emergency Diesel Generator 2/5/87 All power reactor

Room Cooling Design facilities holding

Deficiency an OL or CP

OL = Operating License

CP = Construction Permit

IN. 87-.XX

AprilI, 1987 No specific acztiQ.n or written.response is required by this iTnformatian notice- If you -have questions about this matter. please contact the Regimonl .Adminis- trator of the appropriate. NRC: regional offi.ce.Qr this office..

Edward L. Jordan, .irec.or

ODivsion of Emergency Preparedness

and Engineering Response

.Office of Tospection.and Enforcement.

Technical Contacts: Eric Weiss) IE.

(301) 492-9005 Charles Patterson, NRC Resident Inspector

Browns Ferry. Nuclear Power Plant.

(2,5) 729-6196 Attachment: List of Recently Ts~sued, IE.Information Notices

-by phone IQ U.S CONCURRENCE,

• EAB.JDEPER:1.E Region II *H. -DEPER: IE *EGC8:OEPER: IE 0 R: . D.. LE

Algnatoni.asGable. JRosenthal RMBaer S tz rdan

eiss3 -ew -/87\ q 4//87

0X3/3/87 OV/ /87 03/30/87 ,03/3% 03/ /87

IN 87-XX

March , 1987 No specific action or written response is required by this information notice.

If you have questions about this matter, please contact the Regional Adminis- trator of the appropriate NRC regional office or this office.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Technical Contacts: Eric Weiss, IE

(301) 492-9005 Charles Patterson, NRC Resident Inspector

Browns Ferry Nuclear Power Plant

(205) 729-6196 Attachment: List of Recently Issued IE Information Notices

• SEE PREVIOUS CONCURRENCE

• EAB: DEPER: IE Region II *IE EAB:DEPER:IE *EGCB:DEPER:IE DD:DEPER:IE D:DEPER:IE

EWWeiss: ew AIgnatonisDGabl JRosenthal RLBaer SASchwartz ELJordan

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