ML19343C296
| ML19343C296 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/11/1978 |
| From: | Skibitsky W CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-78-03, IEB-78-3, NUDOCS 8103060338 | |
| Download: ML19343C296 (3) | |
Text
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f General omces: 212 West Macmigan Avenue. Jackson. Micnigan 49201. Area Coce S17 788-05S0 April 11, 1978 Mr James G Keppler Office of Inspection and Enforcement Region III US Nuclear Regulatory Co= mission T99 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - RESPONSE TO IE BULLEIIN 78-03 IE Bulletin 78-03 discusses the potential for accumulation of explosive gas mixtures in Eoiling Water Reactor Off-Gas System Operations and requests that Consumers Power Company review and respond to specific areas of concern relat-ing to this system. The purpose of this letter is to provide the requested response.
ITEM Review the operations and maintenance procedures related to the off-gas system to assure proper operation in accordance with all design parameters.
Include in this review measures you have taken or vill take to prevent inadvertent actions (such as are strikes) which might cause ignition of the mixture of gases contained in the off-gas piping.
RESPONSE
Big Rock Point Operating, Maintenance and Administrative procedures relating to the off-gas system have been reviewed and, where necessary, appropriate precuations were added to preclude inadvertent ignition of potentially ex-plosive gases.
ITU4 Review the adequacy of the ventilation of spaces and areas through which off-gas system piping containing explosive mixtures of gases pass. The review should consider ventilation losses and off-normal off-gas system operation, such as lack of dilution stea=, lost loop seals, blevn rupture disks, by-
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passing reco=biners and leakage of off-gas into isolated portions of systems.
p.3141978 T (O S Ofoo33 8
2
RESPONSE
A review of the design of the off-gas systen at Big Roch "oint indicates that there are two notential areas that could possibly be affected b/ off-gas release. These areas are the pipe tunnel and the radvaste area. Both areas are well ventilated; the pipe tunnel having a flow of 5,000 cfm to lh,100 cf= (design) and the radvaste area frc= 1,500 cft to h,000 cf: (de-sign).
In order to reach an explosive concentration in these areas, the hydrogen concentration vould have to exceed h% and, based on the ventilatien flow rates, this vould correspond to a hydrogen escape rate of 60 cfm and 200 cfh for the radvaste area and pipe tunnel, respectively. Since these are significantly higher flow rates than nc=inally exist in the off-gas holdup line (10 cf=), it is highly unlikely that the li=it(s) can be exceeded.
Note: The analysis deriving these flow rates assu=es =ini=u= design ventila-tion flow and unifor= =ixing.
ITU4 For those spaces and areas identified, describe what action you have taken or plan to take to assure that explosive mixtures cannot accu =ulate, that
=onitoring equip =ent vill varn of such an accu =ulation and that disposal of such =ixtures vill be controlled without resulting in a da= aging explosion.
RESPONSE
g There are no plans to alter off-gas syste= or ventilation syste= design at Big Rock Point. There are no hydrogen detectors in either the radvaste area or pipe tunnel and the only ventilation flow indication available in the con-trol roo= is ventilation supply and exhaust fan alar =s.
Rovever, because of the extremely low potential for explosion based on both the analysis perfor=ed in the previous response and Big Ro:k Point's long operating history with no significant off-gas problems, it is concluded that current procedures, design and operation are adequate to preclude a ds= aging explosion.
ITH4 Loop seals are potential off-gas leakage paths following a pressure transient in the off-gas systes piping. Describe your design features to =inimize and detect the loss of liquid fro: loop seals and describe operating procedures which assure pro =pt detection and reseal of the blevn loop seals.
RESPONSE
There is no =ethod available to verify whether an off-gas loop seal is full.
Analysis has shown that off-gas pressure is no=inally one to two ounces per square inch, necessitating a four-inch loop seal to ensure sealing integrity.
Since all off-gas loop seals at Big Rock Point are approximately two feet or longer, the possibility of seal failure is re=ote.
If a loop seal should fail however, it vould auto =atically refill via =oisture collection fro = within
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the syste= and without any procedural action required.
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Review operating and emergency procedures to assure that your operating staff has adequate guidance to respond properly to off-gas system explosions.
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RESPONSE
There are no Big Rock Point Plant procedures that deal specifically with off-gas syste= explosions. However, both the Operating Procedures and the Site Emergency Plan address and adequately cover plant fires. Further, the Plant Operating Procedures also address abnormal off-gas and stack gas releases as vell as off-nor=al procedures for other systems.
Based on this, it is cen-cluded that the required response to a postulated off-gas explosion is ade-quately addressed.
In su-wy, the operatioa and design of the off-gas syste= at Big Rock Point has been reviewed for tne potential of =aintaining accumulations of explosive gases. The review has produced no evidence that syste= design or operation should be altered based upon safety deficiency.
Since further, and = ore de-tailed, review in this area vill be conducted during the Syste=atic Evalua-tion Progra= (SEP), it is requested that any other required evaluation be coordinated with this effort.
Willia S Skibitsky (Signed)
Willia S Skibitsky Senior Licensing Engineer CC: Director, Office of Nuclear Reactor Regulation Director, Office of Inspection and Enforcement