ML20045G441
| ML20045G441 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/23/1992 |
| From: | Jeffrey Riley GENERAL ELECTRIC CO. |
| To: | Scace S NORTHEAST UTILITIES SERVICE CO. |
| References | |
| G-EH-92-052, G-EH-92-52, NUDOCS 9307130351 | |
| Download: ML20045G441 (2) | |
Text
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'JUN-3-93 THU 9:40 Gen. Facil. Licensing FAX N0' 203 665 5896 P.02'
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aw GE Nuclear Energy n in :m.f
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G-EH-92-052 December 23, 1992
(({y{h l
Mr.
S.E.
Scace utC 3 01992 Vice President - Millstone Station Millstone Nuclear Power Station PROJECTsERVICES DEPARTM Northeast Utility Service Co.
H.P.RISLEf P.O.
Box 128
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Waterford, CT.
06385
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Subject:
Postulated _Hydrocen h losion in a Non - United States Reactor Turbine Building Mezzanine
Dear Mr. Scace:
A BWR/3 utility located outside of the U.
S.,
recently informed GE that a post _ulated hydrogen gas line break in the plant's_ Turbine u
guilding mczzanine co~ul'd result in a hydrogen detonation.
U. S.
BWR utilities may have similar turbine building configuration /cquipment arrangements which could result in a similar condition.
However, thi',
portion of the plant is in the utility's Architect Engineer's scope'c.i supply and therefore cannot be evaluated by GE within the context of i
the U.S.
Code of Federal Regulations 10 CFR Part 21.
GE is, therefore, obligated, under the requireEtruf--le-c3 Part 21, to j
pass this information on to the potentially affected BWR utilities sc that they can review the following information for applicability to i
their unique plant design.
At the subject plant, the pipe lines which carry hydrogen gas to cool {
the generator are routed from the hydrogen bottles outside the turbin i building to the hydrogen controls in the turbine building mezzanine l
area and up to the' generator.
It was postulated that if a break-occurred in one of these lines, up to 16,000 cubic feet (459 cubic meters) of hydrogen gas would rapidly blow down into the mezzanine (a semi-enclosed area).
This room has a volume about 56,000 cubic feet i
(1,600 cubic meters) of oxygen so that even with uniform mixing, the i
average hydronen concentration could easily exceed 251 by volume, which is well above the lower limit of a-detonatable mixture-(13% by i
volume).
A scoping calculation indicated that hydrogen gas could enter the roo from a major pipe break at an initial rate of about 10,000 cubic feet' per. minute (cfm), and release all 16,000 cubic feet in about three minutes.
If all of the hydrogen were retained in the room, a detonatable concentration would exist.
HowcVer,.the mczzanine at thiJ plant is well ventilated with a ducted flow of 2,000 cfm of air and'a j total flow of about 30,000 cfm coming from other sources.
Thus, a j
~
more realistic calculation yielded an average hydrogen concentration.
i in the room of about 10%, which is equivalent to about 30 pounds of l
This 10% concentration can be ignited and result in-an explosion.
9307130351 921123 O
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' JUN-3-93 TiiU 9:41 Gen. Facii. Licensing FAX 0. 203 665 5896 P.03 At the subject plant, the room below the generator contains the hydrogen piping and generator output busses, their cooling and air conditioning systems, and the generator auxiliary equipment.
This includes the piping containing hydrogen and oil mixtures.
An opening in the structure supporting the generator indirectly exposes some of the plant's 1E and non-1E clectrical busses to the effects of an explosion or a fire.
Based on the above estimated average hydrogen gas concentration of 10% by volume in a part of the mezzanine, a conservatively estimated blast pressure of 40 psi would have to be contained at the opening to prevent blast waves from exiting this area and damaging the vital bucces.
To avoid the possibility of consequential damage, a recommendation will be made to the utility to provide a blast shield or ignitors to mitigate or prevent a potential blast.
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/ GE recommends that all BWR utilities perform an evaluation to postulated generator coolant hydrogen explosion determine if a represents a substantial safety hazard at their facility.
Northeant Utilitics chould evaluate this information as it relates to existing or future plant equipment, conditions, procedures or plans.
GE cannot determinc if this information affects U.
S.
BWR utilities.
GE is, therefore, notifying all U.
S. BWR owners of this information.
The owners of GE BWRs located outside the U.
S.
also will receive this information.
Sincerely,[_
wdWu
'J
,7 M.P. Riley J
Nuclear Services Manager GE Nuclear Energy cc:
P.A.
Blasioli L.D.
Davison E.A.
DeBarba f
R.T.
Harrin i
- 11. F. llaynes i
H.P.
Risley W.D.
Romberg R.W.
Tobin. GE Site Notice This 10 CFR Part 21 information pertains only to GE BWRs.
GE Nuclear Energy (GE-NE) has not considered or evaluated the applicability, if any, of this information to any plant or facility other than GE BWRs.
.