ML20216C630
| ML20216C630 | |
| Person / Time | |
|---|---|
| Issue date: | 06/10/1987 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Bates J HOUSE OF REP. |
| Shared Package | |
| ML20216C635 | List: |
| References | |
| NUDOCS 8706300321 | |
| Download: ML20216C630 (6) | |
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The Honorable James Bates-Member, United States House M 10 W of Representatives 9430 Davidson. Street, Suite A Chula Vista, California 92010 p.' .
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Dear Congressman Bates:
Your letter of April 30,1987 requested our reply to a constituent's interest' in the use of a " hydrogen match" to prevent nuclear power plant disasters.
The enclosed discussion responds to this matter.
Sincerely.
Original signod by Victor Stello Victor Stello, Jr.
Executive Director for Operations
Enclosure:
Hydrogen Control in U.S.
Commercial Power Ret.ctors DISTRIBUTION:
Central Files NRC PDR PSB Reading.
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s Hydrogen Control in U.S. Commercial Power Reactors The importance of addressing combustible gas generation, principally hydrogen, as a consequence of reactor accidents has been recognized in the U.S. since the early days of commercial power reactors. Hydrogen is of concern in reactor safety since the combustion of hydrogen can threaten the integrity of the containment structure which encloses the nuclear reactor or cause the failure of important safety equipment inside the containment. Hydrogen is generated during such accidents principally as a result of the reaction of steam with overheated fuel rods. Basically, the metal fuel rod reacts with water in the vapor phase (steam) to produce a metal oxide and hydrogen gas.
Early requirements for dealing with hydrogen production, developed during the 1960s, required the operators of nuclear plants to provide safety systems to deal with the various sources of hydrogen produced during an accident. The TMI-2 accident focused attention on the potential consequences of generating hydrogen during severe accidents. As a consequence of the TMI-2 accident and in consideration of more severe accidents, the NRC issued new regulations requiring additional hydrogen safety systems.
A variety of strategies are used at U.S. nuclear plants to deal with potential hydrogen generation. Small volume containments (Mark I and II) used for boiling water reactors are made inert with nitrogen; i.e., nitrogen is substituted for air inside the containment building, so that combustion is prevented. Medium volume containments used to enclose reactors in boiling water reactor Mark III ;
plants and pressurized water reactor ice condenser plants have installed {
electrical igniters to burn the hydrogen before it reaches threatening levels. '
Large volume containments, by virtue of their size, and strength, are judged to have sufficient inherent capacity to withstand the effects of hydrogen ;
combustion.
l The " hydrogen match" referred to in the magazine article (published in
" Breakthrough by Boardroom Reports") was developed at Sandia National Laboratories i as part of an extensive research program on hydrogen related issues conducted '
for the NRC. As noted, the owners of boiling water reactor Mark III plants l and pressurized water reactor ice condenser plants have already installed ;
electrical igniters to control large releases of hydrogen. These igniters 1 utilize the same basic approach to hydrogen control as that intended by the
" hydrogen match"; i.e., burn hydrogen before it accumulates to unsafe levels. '
The difference between these alternative ignition devices lies in the ;
difference in the detailed engineering principles of operation, not in the l l
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-2 ultimate design objective. The electrical igniters installed in nuclear power
, plants have been tested and shown to be reliable for igniting hydrogen at safe levels. The igniters developed at Sandia National Laboratory would require l additional extensive testing ir Srder to demonstrate a similar level of ,
reliability.
Following the reactor accident at Chernobyl, the NRC initiated an investigation to determine if there were any implications from the Chernobyl accident on the safety of U.S. commercial reactors. With regard to hydrogen combustion, the generation of large quantities of hydrogen was apparently not considered as part of the Soviet design. In the Chernobyl plant, large amounts of zirconium in the reactor core coupled with high temperatures during the accident resulted in hydrogen generation.
A significant difference between the Chernobyl plant and nuclear plants in the U.S. is the presence of graphite in the reactor core. Only one U.S. commercial reactor (Fort St. Vrain Nuclear Generating Station) uses a graphite _ moderator.
The design of this reactor is significantly different than the Chernobyl plant.
The Fort St. Vrain Nuclear Generating Station uses helium as a primary coolant and does not use metal fuel rod cladding, thus reducing the potential for the reaction producing hydrogen during accidents associated with water cooled or moderated reactors. The Chernobyl reactor was a water cooled reactor with metal fuel rod cladding. There is no analogy, therefore, between what happened at Chernobyl and the consequences of postulated accidents at the Fort St. Vrain plant with respect to potential hydrogen generation. er l
The NRC has concluded, following the preliminary evaluation of the Chernobyl accident, that no additional efforts relative to hydrogen control in commercial power reactors in the U.S. are warranted. As a corollary, the NRC has determined that our current regulatory position and research program in conjunction with the study of severe accidents at U.S. reactors is adequate to ensure the public health and safety. j
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1 The Honorable James Bates 430 Davidson Street, Suite A Chula Vista, California 92010
Dear Congressman Bates:
Your letter of April 30, 1987 requested our reply to a constituent's interest in the use of a " hydrogen match" to prevent nuclear power plant disasters.
The enclosed discussion responds to this matter. '
\ j !
Victor Stello, Executive Director for Opera ions
Enclosure:
Hydrogen Control in U.S. / )
Comercial Power Reactors / -
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DIS IBUTION Docke File
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EDO PRINCIPAL CORRECPONDENCE CONTROL-t FROM: DUE: 05/27/87 EDO CONTROL: 002856 DOC DT:'04/30/87 y REP._ JIM BATES. FINAL REPLY:
- TO: b OCA FOR. SIGNATURE OF: ** GREEN ** SECY NO: 87-561 EXECUTIVE ~ DIRECTOR
'DESC: ROUTING:
ENCLOSES LETTER.FROM' MICHAEL FEITLER CONCERNING USE OF HYDROGEN' BURNERS IN GRAPHITE MODERATED-NUCLEAR REACTORS'
/ v DATE: 05/12/87 g ASSIGNED TO: NRR ' CONTACT: MURLEY SPECIAL INSTRUCTIONS OR REMARK 9x - l}
REF.'EDO 2850 REPLY TO CHULA VISTA, CALIFORNIA OFFICE.
NRR' RECEIVED: 5/12/87
- ACTION:. TDESTiSHAdh*
NRR ROUTING: MURLEY/SNIEZEK MIRAGLIA STAROSTECKI BLAHA' FUNCHES 7 nOSSauaG t/ ACTION DUE TO NRR DIRECTOR'S OFRCE BY -7/17h'/
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OFFICE OF THE SECRETARY CORRESPONDENCE CONTROL TICKET
. PAPER NUMBER: CRC-87-0561~ ' LOGGING DATE: May 11'87-
- ACTION OFFICE:' EDO AUTHOR:- J. Bates--Const Ref
. AFFILIATION:- U.S. HOUSE OF REPRESENTATIVES
/ LETTER DATE: Apr 30 87 FILE CODE: C&R-2 BP.
SUBJECT:
Use of a hydrogen match to prevent nuc power-plants disaster ACTION: Direct Reply DISTRIBUTION: OCA'to Ack SPECIAL HANDLING: None NOTES: M Feitler 2DATE DUE: May 25.87' SIGNATURE: . DATE SIGNED:
AFFILIATION:~
Ra(d Off. EDO f
., Date 5-f217 Tinn l I l o -
- 002 856