Information Notice 1987-20, Hydrogen Leak in Auxiliary Building

Hydrogen Leak in Auxiliary Building

ML070180059
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, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	04/20/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-87-020, NUDOCS 8704160059
Download: ML070180059 (4)

SSINS No.: 6A35 IN 87-20

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 April 20, 1987 NRC INFORMATION NOTICE NO. 87-20: HYDROGEN LEAK IN AUXILIARY BUILDING

Addressees

All nuclear power reactor facilities holding an operating license or a con- struction permit.

Purpose

This notice is to alert addressees of the potential for a hydrogen leak in

portions of the plant where the potential for the leak may not have been

adequately considered. 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.

Description of Circumstances

On February 20, 1987, the Vootle nuclear power plant reported a hydrogen leak

inside the auxiliary building. This plant was recently licensed, had never

been critical, and was In cold shutdown at the time of the event.

The discovery of this problem was as a result of an unassociated event involving

the activntion-of a chlorine monitor in the control building. -When additional

samples inuicated no chlorine gas, the shift supervisor ordered further investi- cation into other plant areas. Because there was no installed detection

equipment, portable survey instruments were used to determine gaseous mixtures.

Hydrogen was detected in the auxiliary building and indicated about 20 to 30

percent of the lower flammability limit (LFL) for hydrogen. A level of about

30 percent of LFL rorresponds to about 1.2 percent hydrogen by volume. This

reading was erroneously reported to the control room as 20 to 30 percent hydrogen

by volume. The on-shift supervisor declared an unusual event (UE) with a

subsequent report to the NRC via the emergency notification system (ENS).

When hydrogen was discovered in the auxiliary building, the licensee isolated

the cryogenic hydrogen skid outside the turbine building and soon located the

source of the leak as packing on a globe valve in a small line to the volume

control tank (VCT). The licensee opened doors that quickly caused the hydrogen

to dissipate. The globe valve was of a conventional design and had no special

packing. The globe valve was located in a vertical pipe chase where little

8704160059Ll~

IN 87-20

April 20, 1987 ventilation was present because of ongoing HVAC testing. Besides being used

as a cover gas in the VCT, hydrogen from the skid also is used in the plants

waste gas system and to cool the generator.

Discussion:

The lessons of this event fall into five categories: (1) proper in-plant

communications during events, (2) proper valve application for use with

hydrogen, (3) excess flow check valve set point, (4) heating ventilation and

air conditioning (HVAC) maintenance and flow testing, and (5) hydrogen line

routing.

The licensee is examining ways to improve communications in the plant during

events and the training of personnel in reading portable instruments.

As another corrective measure, the licensee is examining the use of other types

of valves, such as valves with a diaphragm or bellows rather than conventional

stem packing, in lines containing hydrogen.

The licensee also is examining the set point for the excess flow check valves

in the hydrogen lines. These check valves are designed to limit the flow of

hydrogen in the event of a large leak so that when combined with proper ventila- tion in rooms with hydrogen lines, hydrogen levels would remain within specified

limits throughout the plant.

This plant had HVAC flow balancing problems during the preparation for plant

startup. Generally HVAC flow balance is based on the heat loads and the

resultant room temperatures under normal and accident conditions. However, this

event demonstrates that hydrogen concentrations also may need to be considered

to set a lower limit on the ventilation in rooms that contain hydrogen lines.

Although this licensee has reexamined the routing of hydrogen lines throughout

the auxiliary building and found no problems, licensees with older plants may

not have examined this question in detail.

The NRC staff is currently reviewing an EPRI/BWROG topical report titled

"Guidelines for Permanent BWR Hydrogen Water Chemistry Installation," 1987 revision. Included in this document are guidelines for design, operation, maintenance, surveillance, and testing of hydrogen supply systems.

Other Recent Reactor Events Involving Hydrogen

On March 3, 1987 an unusual event was reported at Waterford Unit 3 plant.

While unloading hydrogen from a truck into the storage tank, the storage tank

rupture disc failed and a deflagration and fire ensued. The fire burned itself

out in about an hour with no apparent damage to the storage facility.

IN 87-20

April 20, 1q87 On January 12, 1987,1 an explosive mixture of hydrogen and oxygen was discovered

in the number 1 holdup tank of the gaseous radwaste system at Zion Unit 1.

Prompt action was taken to isolate the tank and dilute the gaseous content with

a nitrogen purge to reduce the hydrogen concentration below explosive limits.

Investigation showed that the holdup tank was placed in service on January 6,

1987. However, the tank was left isolated from the automatic waste gas

analyzer until January 12, 1987. This violated the technical specifications

requiring daily analysis of the waste gas system for oxygen and hydrogen.

A report that may be useful in considering hazards and some methods for improving

the safe handling of pressurized gas is NUREG/CR-3551, ORNL/NOAC-214 "Safety

Implications Associated with In-Plant Pressurized Gas Storage and Distribution

Systems in Nuclear Power Plants," published in May 1985.

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

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

Cares . ossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Eric Weiss, AEOD

.(301) 492-9005 Frank Witt, NRR

(301) 492-q440

Attachment: List of Recently Issued IE Information Notices

IN S7-tO I

A~ttcic~.t

April 20, 1t7 LIST Of RECENTLY. ISSUtO

l1 INiFOO1ATION NOTIC[S 197 informtion IN't' of

No+tic !2. 'lly~fte I+.+* 1.lyid t

BS-41 kisllintstratiens to 4/15/8? All IiCOnlHI

Sup. I Patients Ulndergoing Thyroid authorized to use

Scoan byproduct material

87,14, Perfrortlon and Cracking I@ 4/4/97 All Westinghouse

Rod Clutter Control Asemblies power PVI facilitiel

holding An AL or CP

8.18 iUnauthorized Service on 4/18/87 All NRC Ilifcense

Telethorapy llnitsby Non. authorized to use

licensed Maintenance Personnel radioactive material

In telotherapy units

A7-17 Response Time of Scram 4/7/87 All GE oRw facilities

Instrument Volume Level holding on OL or CP

Detectors

87-ti Deogradation of Static "0" 4/218? All LWO facilities

king Pressure Switchet holding in AL or CP

87-IS Compliance with the Posting 3/?5/87 All pooer reactor

Requlrcawnts of Subsection facilities holding

7?3b of the Atomic Energy a CP and all firms

Act of 1954. as Aernded supplyinq components

or servIces to such

facilities

A7.14 Actuation of Fire Suppression 3/73/87. All power reactor

System Causing Inoperability facilities holding

of Saflty-Ralated Ventilation an O or CP

Eoul ient

A6-106 Feedwater Line Break 3/18/87 All reactor

Power

Sup. 2 facilities holding

in IL or CP

87.13 Potential for High Radiation 21/?U/A7 All powwerreactor

Fields Following Loss of facilities holding

Water from Fuel Pool, an ql.or CP except

Fort St. ¥rain

UL a pDerating License

CP

• Construction Permit

UNITED STATES FIRST CLASS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE 6 FitS PAIO

uSpnRC

WASHINGTON, D.C. 20555 WASH CC

PERMIT No 847 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $30