Information Notice 1991-84, Problems with Criticality Alarm Components/Systems

Problems with Criticality Alarm Components/Systems

ML031190217
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, 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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	12/26/1991
From:	Cunningham R NRC/NMSS/IMNS
To:
References
IN-91-084, NUDOCS 9112190113
Download: ML031190217 (5)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C.

20555

December 26, 1991

NRC INFORMATION NOTICE 91-84: PROBLEMS WITH CRITICALITY ALARM

COMPONENTS/SYSTEMS

Addressees

AllNuclear Regulatory Commission (NRC) fuel cycle licensees, interim spent

fuel storage licensees, and critical mass licensees.

Purpose

NRC is issuing this notice to remind licensees of the importance of adequate

reviews of plant modification, installation, maintenance, and response actions, to ensure that required criticality alarm systems meet their intended purpose.

It is expected that recipients will review this information for applicability

to their facilities, distribute it to responsible staff, and consider actions,- as appropriate, to avoid similar problems. However, suggestions contained in

this information notice do not constitute any new NRC requirements, and no

written response is required.

Description of Circumstances

The following cases are recent events involving problems with licensee's

criticality alarm systems that have been reported to, or discovered by, NRC.

Case 1:

During a routine test of the criticality alarm system, a licensee

discovered that several of the site's audible alarms ("howlers") did not

actuate.

The licensee found that wiring to the alarms had been accidentally

broken while other electrical cables were being pulled through the cable run

that contained the criticality alarm wiring.

The licensee's system provided

indication, prior to the next scheduled test, that some of-the audible alarms

had been disabled.

Case 2:

Engineering drawings describing modifications at a licensed facility

specified removal of "heat detectors (radiation)." The licensee's review of

the modification package did not recognize that it included removal, rather

than relocation, of criticality alarm system detectors.

When the specified

detectors were removed no alarm was generated at the system monitoring panel.

Subsequent investigation disclosed that the alarm panel was wired in such a

way that, although a "failure" light was activated at an intermediate panel (an

unmanned location), a "loss of power/loss of detector" signal was not generated

at the monitoring panel in a normally manned area.

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IN 91-84 a

December 26, 1991 Case 3: A licensee experienced an activation of the plant's criticality alarm

system, but no criticality accident had actually occurred.

Investigation

found that the alarm had been generated when the uninterruptable power

supply (UPS) circuit that powered the alarm system was turned off by means of

a switch in the facility's main computer room.

The switch had been backfitted

to the system to allow for cutoff of all power to the computer room in

emergency situations and was not intended to affect power to the criticality

alarm system.

The modification review associated with the addition of the

switch did not identify the fact that the planned location was between the UPS

source and the primary criticality alarm system circuit.

Case 4:

During an electrical storm, the criticality safety alarms at only

the Waste Treatment Facility (WTF) sounded because of a momentary power

interruption.

Personnel in the WTF did not evacuate, but instead called

Security, who then notified Radiation Control and Electrical Shop personnel.

Electricians then entered the WTF to silence the alarms before obtaining

clearance from Radiation Control.

An investigation of the incident determined

that the personnel in the WTF did not evacuate in accordance with procedures

required by 10 CFR 70.24, and that the electricians made an uncontrolled entry

into the WTF to silence the alarms prior to getting clearance from Radiation

Control.

Case 5:

During a routine NRC inspection of a licensee's criticality accident

monitoring system, the inspector found that:

(1) since 1970, no evaluation had

been performed to demonstrate that the system provided adequate monitoring

coverage for facility modifications or additions where large quantities of

special nuclear material were being stored or used; (2) the licensee did not

have a system to ensure that such technical evaluations were performed and

documented; and (3) no program existed to limit the storage of intervening

shielding materials between the neutron criticality detectors and the monitored

areas.

Case 6:

During maintenance, a licensee discovered that under design basis'

accident conditions (greater than 1 E+15 fissions) its criticality alarm

system might not function as intended.

The alarm system used Geiger-Mueller

detectors that could become electronically saturated in a high radiation

field and not function.

As a result, the licensee declared an Unusual Event

and discontinued transfers of fissile materials within the facility.

The

licensee terminated the Unusual Event after connecting anti-saturation

circuitry to the criticality alarm system.

Discussion

All licensees are reminded of the importance of maintaining operable

criticality detection, monitoring, and annunciation capabilities, as well as

procedures and training for response to criticality alarms.

As the forementioned

cases indicate, a lack of detailed knowledge of the system's configuration and

routing of detector or power circuits can result in failure to recognize the

possible impact of installation, modification, or maintenance activities on

the criticality alarm system. Physical and electrical modifications have the

S

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I

IN 91-84 December 26 1991 clear potential to degrade or disable all or part of this important safety

system.

Licensees should ensure that they have established a comprehensive

testing program, both on a routine basis and after maintenance and modification

activities, and a method of continuously monitoring the integrity of

criticality alarm system lines and components, through line supervision, to preclude failure of criticality alarm system capabilities. These activities

should include clearly written implementing procedures, and a training program

to ensure appropriate implementation.

This information notice requires no specific action or written response. If

you have questions about the information in this notice, please contact one of

the technical contacts listed below or the appropriate regional office.

Richard E. Cunningham, Director

Division of Industrial and

Medical Nuclear Safety, NMSS

Technical contacts:

Scott Pennington, NMSS

(301) 504-2693

Gerald Troup, RII

(404) 331-5566 Attachments:

1. List of Recently Issued NMSS Information Notices

2. List of Recently Issued NRC Information Notices

K>~

i 4

.

Attachment 1

IN 91-84

December 26, 1991 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Intormation

Date ot

Notice No.

Subject

Issuance

Issued to

91-71

91-66

91-65

91-60

91-49

91-44

91-39

91-35 Training and Supervision

11/12/91 All NRC medical licensees.

of Individuals Supervised

by an Authorized User

(1) Erroneous Data in

10/18/91 All fuel cycle licensees,

"Nuclear Safety Guide, critical mass licensees, TID-7016, Revision 2,"

interim spent fuel storage

(NUREG/CR-0095, ORNL/

licensees, and all holders

NUREG/CSD-6 (1978)) and

of operating licenses or

(2) Thermal Scattering

construction permits for

Data Limitation in the

test, research, and nuclear

Cross-Section Sets Provided

power reactors.

with the KENO and SCALE Codes

Emergency Access to

10/16/91 All NRC licensees.

Low-Level Radioactive

Waste Disposal Facilities

False Alarms of Alarm

09/24/91 All Nuclear Regulatory Com- Ratemeters Because of

mission (NRC) licensees

Radiofrequency Interference

authorized to use sealed

sources for industrial

radiography

Enforcement of Safety

08/15/91 All Nuclear Regulatory Com- Requirements for Radiographers

mission (NRC) licensees

authorized to use sealed

sources for industrial radi- ography.

Improper Control of Chemicals 07/07/91 All nuclear fuel facilities.

in Nuclear Fuel Fabrication

Compliance with 10 CFR

06/17/91

All Nuclear Regulatory

Part 21, "Reporting of Defects

Commission (NRC) material

and Noncompliance"

licensees.

Labeling Requirements for

06/07/91

All U.S. Nuclear Regulatory

Transporting Multi-Hazard

Commission (NRC) licensees.

Radioactive Materials

l

Attachment 2

IN 91-84

December 26, 1991 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

91-83

91-18, Supp. 1

91-82

91-81

91-80

91-79

88-92, Supp. 1

91-78

90-57, Supp. 1 Solenoid-Operated Valve

Failures Resulted in

Turbine Overspeed

High-Energy Piping Failures

Caused by Wall Thinning

Problems with Diaphragms

in Safety-Related Tanks

Switchyard Problems that

Contribute to Loss of

Offsite Power

Failure of Anchor

Head Threads on Post-

Tensioning System During

Surveillance Inspection

Deficiencies in the

Procedures for Instal- ling Thermo-Lag Fire

Barrier Materials

Potential for Spent

Fuel Pool Draindown

Status Indication of

Control Power for

Circuit Breakers Used

in Safety-Related Appli- cations

Substandard, Refur- bished Potter & Brum- field Relays Repre- sented as New

12/20/91

12/18/91

12/18/91

12/16/91

12/11/91

12/06/91

11/29/91

11/28/91

11/27/91

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

OL = Operating License

CP = Construction Permit