ML17194B168
| ML17194B168 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/28/1982 |
| From: | Oconnor P Office of Nuclear Reactor Regulation |
| To: | Delgeorge L COMMONWEALTH EDISON CO. |
| References | |
| TASK-03-04.A, TASK-3-4.A, TASK-RR LSO5-82-06-099, LSO5-82-6-99, NUDOCS 8207080441 | |
| Download: ML17194B168 (23) | |
Text
Docket No. 50-237 LSOS-BC-06-099 Mr. L *. DelGeorge Director of Nuclear Licensing Commonwealth Edison Company
- Post Office Box 767 Chicago, Illinois 60690
Dear Mr. DelGeorge:
June 28 ~ 1982
.'\\- \\..~-.... J :
"'SUm'lECT:
- SEP TOPIC II I-4. A, TORNADO MISSILES DRESDEN 2
~~~
Enclosed is our final evaluation of SEP Topic III-4.A. It is based on a Safety Analysis Report which you supplied on December 12, 1981, and other infonnation available on Docket No. 502237.
The evaluation concludes tha'tfthere.are portions of safety... relatfld systems which are not adequately protected from tornado missiles.
The evaluation will be a basic inpJJt to the integrated safet,x:Jasses~
ment of your facility.
It may be_;changed in the future 1.f you~.
facility design is changed or if NRC criteria is modified befo~e 5eoY
~~ u~E,(ff,)
completion of the 1ntegri}ted assessment.
r:
Enclo.iure:
As stated cc w/enclosure:
. See next page 8207080441 820628 PDR ADOCK 05000237 p
PDR 1
~------*. -**-~.!.
NRC FORM 318 (10-80) NACM 0240 I
I Sincerely, c;~
{fiaul O'Connor, Project Manager Operating Reactors Branch No. 5 Division of Licensing 6/-ilof /82 OFFICIAL RECORD COPY
.r-_.
~
f'\\..i Mr:. L. De 1 George
... l.
1..1 cc Robert G. Fitzgibbons, Jr.
Isham, Lincoln & Beale Three First National Plaza Suite 5200 Chicago, Illinois 60602 Mr. Doug Scott Plant Superintendent Rural Route #1 Morris, Illinois 60450
. U. s. Nuclear Regulatory Commission Resident Inspectors Office Dresden Station RR #1.
Morris, Illinois 60450 Mary Jo Murray Assistant Attorney General
.Environmental Control Division 188 W. Randolph Street Suite 2315 Chicago, Illinois 60601 t
Chairman
.Board of Supervisors of Grundy County
- Grundy County Courthouse Morris, Illinois 60450 Illinois Department of Nuclear Safety 1035 Outer Park Drive, 5th Floor Springfield, Illinois 62704 U. S. Environmental Protection Agency Federal Activities Branch Region V Office ATTN:
Regional Radiation Representative 230 South Dearborn Street Chicago, Illinois 60604 The Honorable Tom Corcoran United States House of Representatives Washington, D. C.
20515 John H. Frye, III, Chairman Atomic Safety and Lfoensing Board U. S. Nuclear Regulatory Commission*
Washington, D. c.
20555 Dr. Martin J. Steindler Argonne National Laboratory 9700 South Cass Avenue Argonne, Illinois 60439 Daniel Mintz, Esquire Counsel for Petitioners (Citizens for a Better Environment)
Suite 1600, 59 E. Van Buren Street Chicago, Illinois 60605 Dr. Robert L. Holton School of Oceanography Oregon State University Corvallis, Oregon 97331 James G. Keppler, Regional Administrator Nuclear Regulatory Commission, Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137
ENCLOSURE DRESDEN NUCLEAR POWER PLANT, UNIT NO. 2 SEP TOPIC III-4.A -
T9RNADO MISSILES I.
INTRODUCTION Tornado generated missiles could caus~ sufficient damage to a plant so that the actual safety of the plant is reduced.
Topic III-4.A is intended to review the plant design to assure that those structures, systems and components important to safety can withstand the impact of an appropriately postulated spectrum of tornado generated missiles.
- These include those structures, systems and components required to assure:
- 1.
The integrity. of ~he reactor coolant pressure boundary,
- 2.
The capability to ~hutdown the reactor and maintain it in a safe shutdown condition, and
- 3.
The capability to prevent accidents which could result in unacceptable offsite exposures.
Scope of Review The scope of the review is as outlined in the Standard Review Plan CSRP) Sections 3.5.1.4, "Missiles Generated by Natural*
Phenomena," and 3.5.2, "Structures, Systems arid Components to be erotected Against Externally Generated Missi Les."
An assessment of the adequacy of a plant to withstand the impact of tornado missiles includes:
2 -
- 1.
Determination of the capability ~f the exposed systems, components and structures to withstand key missi Les (including small missiles with penetrating characteristics and Larger missiles which result in an overall structural impact); and
- 2.
Determination of whether any areas of the plant require additional protection.
II.
REVIEW CRITERIA The plant design was reviewed with regard to General Design Criterion 2, "Design :-Sases for Protection Against Natural Phenomena which requires that structures, ~ystems.and components essential to safety be designed to withstand the effects of natural ph~nomena such as tornadoes, and General Design Criterion 4, "En vi ronmenta l and Missile Design Bases" which requires that these same plant features be protected against missiles *. The plant was also reviewed against the guidance contained in R~gula-tory Guides 1.13, "Spent Fuel Storage Facility Design Bases,"
1
- 2 7, " U L t i m a t e H. e a t S i n k f o r N u c L e a r P o w e r. P L a n t s, " 1
- 11 7 "Tornado Design Classification" and 1.76, "Design Basis Tornado for Nuclear Power Plants" with regard to plant protection against tornado missi Les.
I
3 -
III.
RELATED SAFETY TOPICS Topic II-2.A, "Severe Weather Phenomena" describes the tornado characteristics for the plant.
Topic III-2, Wind and Tornado Loadings" reviews the capability of the plant structures, systems and components to withstand wind loadings.
Topic VII-3, "Systems Required for Safe Shutdown" reviews those systems needed to achieve and maintain th~ plant in a safe shutdown condition.
IV.
REVIEW GUIDELINES The review was performed in accordance with Standard Review Plan CSRP) Sections 3.5.1.4 and 3.5.2.
These SRP sections state that the assessment of pos~ible hazards due to missiles generated by the natural phenomena is based on having met the requirements of General Design Criteria 2 and 4 by:
(1) meeting Regulatory Guide
'.1.76, Positions C-1 and C-2 and (2) meeting Regulatory Gui~e 1.117,
'Posftions C-1 and C-3 and its appendix.
SRP 3.5.1.4 further states that plants which were not required at the construction permit stage to design to the missile spectrum in Revision 0 to the SRP should show the capability to withstand the two postulated missiles discussed below.
The following missiles are described in SRP 3.5.1.4 as being appropriate for ev~luating OL applications for :plants which
4 -
were not required to be protected against the full tornado missile spectrum during the CP stage:
- 1.
Steel Rod, 1" diameter, 3' long, 8 lbs., horizontal velocity 0.6 x total tornado velocity.
- 2.
Utility Pole, 13 1/2" diameter, 35' long, 1490 lbs., horizon-tat velocity -
0.4 x total tornado velocity.
The guidelines for systems, structures, and components required to be protected because of their importance to safety are identified f'
in the Appendix to Regulatory Guide 1.117 *
.V.
EVALUATION A.
Tornado Event Description As defined by Regulatory Guide 1.76, the Oresden 2 Plant is in Tornado Region I.
Accordingly, the design basis tornado is characterized by a maximum wind speed of 360 miles per hour with an occurrence frequency of no greater than 10-7 per year.
The tornado characteristics described in SEP Topic II.2.A for the Dresden 2 site are of similar severity.
Therefore, Regulatory Guide 1.76 will provide an adequaie design basis tornado for the Dresden 2 Plant.
5 -
I Therefore, in accordance with SRP 3.5.f~4, Revision O, the total horizontal velocities for the two postulated missiles are:
- 1.
Steel Rod, 317 feet/second.
- 2.
Ut~lity Pole, 211 feet/second.
These missiles are considered to be capable of striking in all directions with vertical speeds equal to BOX of the h~rizontal speeds listed above.
f B.
Structural Considerations In o~r evaluation, we have considered the adequacy of the fol-lowing structures for tornado missile protection:
- 1.
Reactor Building;
- 2.
Turbine~Building;
- 3.
Control Structure;
- 4.
Radwaste Buildings~
- 5.
Diesel Generator Buildings; and
- 6.
Crib House (Intake Structure)
In order to assess the adequacy of tornado missiLJ protection I
of these stru~tures, we have compared their wall and roof I
i thicknesses to the current NRC requirements for the two p6s-1 1
1 tulated mis~i Les for the Region I design basis tof:nado.
For i
I a concrete strength of f'c =4000psi, the requiredjconcrete thicknesses are as stated below:
MISSILE Telephone pole 1" steel rod REQUIRED WALL THICKNESS CINCHES) 12 8
"REQUIRED ROOF THICKNESS CINCHES) 12 8
The external walls of *ll the Dresden 2 pl*nt structures which house the safety-related systems end components ere con-structed of concrete at least 12 inches thick with a concrete strength of SOOD psi.
However, the missile can penetrate barriers made of sidings, such as the reactor and turbine buildings' superstructure and the 11 5/8 -
- nch thick hollo~
concrete walls of t~e crib house.
The letter penetratrable barriers are not considered necessary to pr~tect safe shutdown equipment since no **fe shutdown equip*ent will be affected by missiles penetrating the metal siding alone.
Further penetration of concrete structureswould be necessary to reach safe shutdown equipment.
- c.
Systems Considerations The following structures, systems and components,as listed in the Appendix to Regulatory Guide 1.117,were evaluated to determine their susceptibility to the postulated tornado generated missiles.
- 1.
Reactor Coolant Pressure Boundary The reactor* coolant pressure boundary, up to the outboard ma *i n s t ea m i s o l a t i on v a l v es an d co n t a i nm en t i s o l a t i on valves, is located in the reactor building.
The portion of the reactor coolant system inside the drywell is
7 -
completely enclosed by a 6 1/2 f~ot thickness of rein-forced concrete.
The reactor building walls enclosing the remainder of the reactor coolant system up to the outboard containment isolation valves are reinforced concrete 18 to 36 inches thick.
We conclude that the drywell enclosure and reactor building provide adequate torriado missi Le protec-tion fo.r the reactor coolant pressure boundary.
- 2.
Reactor Core and Individual Fuel Assemblies The reactor vessel which houses the core constitutes a portion of the reactor core pressure boundary which is discussed in Item 1 above.
The fuel assemblies in the/ reactor vessel are adequately protected from tornado missi.le damage by the drywell enclosure and reactor building structure surrounding the drywell.
Pr?tection provided stored spent fuel assemblies is discussed in Item 4 below.
- 3.
Systems or Portions of Systems Required for Atta*ining Safe Shutdown We have reviewed the tornado missile protection provided for the following components and systems *eval~ated in SEP Top i c V1I -I - 3, " S y st ems R e q u i r e d f o r S a f e S h u t d ow n" a s discussed in the Letters from D. M.
Crutchfie~d to J. S.
Abel dated April 24 and July 7, 1981
8 -
- a.
Automatic Pressure Relief System The automatic pressure relief system valves are located within the drywell.
Tornado missile protec-tion is provided by the drywell enclosure and reactor building structure surrounding the drywell as discuss-ed in Item 1 above.
We con~lude that ~fi**~ structures provide.adeQuate protection to the automatic relief v~lyes a9ainst damage from tornado missi Les.
- b.
Low Pressure Coolant Injection/Containment Spray Systems The LPCI/Containment Spray systems' pumps are located on the base elevation of the reactor building.
Piping and valves for these systems are located in the reactor building and inside the drywell.
Protection for these systems is the same as describe~ in Item 1.
We conclude that the tornado gissile protection for the LPCI/Containment Spray Systems is adequate.
- c.
Containment Cooling iervice Water System (Emergency Service Water)
The c.ontainment cooling service water CCCSW) system, which cools the containment cooling heat exchangers, has its pumps located in the condensate pit of the turbine building which is protected by virtue of its below grade elevation in the turbine building and the concrete floor above.
We requested the licensee to verify that the CCSW suction piping in the cribhouse was adequately pro-tected from tornado missiles.
By letter dated March 23, 1982, the licensee stated that the suction piping is located below grade in the cribhouse and is protected by 2 feet of reinforced concrete at grade.
The piping between the crib-house and the turbine building is adequately protected sinr~
it is run in a below gra~e concrete tunnel.
Therefore, we conclude that the CCSW system is adequately protected against tornado generat*d missiles.
- d.
High Pressure Coolant Injection CHPCI) System The HPCI system is located within the tornado protected per-tion of the reactor building with portions of the system within the drywell area.
Thus, we conclude adequate protec-tion is provided as described in Item 1.
- e.
Service Water System The service water system (SWS) supplies a number of loads, two of which may be necessary for shutdown.
These are the control room air conditioning* system and the J
1 auiiliary ~lectrical equipment room ventilation !system.
Our l
I April 24, 1981 safe shutdown evaluation (Topic VII-3) l defers a conclusion on whether or not they are rieeded 1
~
10 -
for safe shutdown and states that such a determina-tion will be made during the ventilation system review.
The draft Technical Evaluation Report (Topic IX-5).from Franklin Research Center dated January 20, 1982 assumes that the auxiliary elec-trical equipment room ventilation system is necessary for safe shutdown and defers a conclusion on the control room ventilati~n system to TMI Item III.D.3.4, "Control Room Habitability."
Based on past experience we have assumed that both these systems are necessary for safe shutdown.
f Assuming th~t the abov~ two ventilation syste*I are necessary for* safe shutdowh. t~en it follows that the service water to the ventilation system wi LL also be needed.
Since portions of this system are located in a non-tornado missile protected por-tion of the cribhouse the SWS is not adequately protected against tornado~missiles.
Based on the above we conclude that with the assump-tion that the control room and auxiliary electrical equi*pment room ventilation systems are necessary for safe shutdown, adequate tornado missile protection is not provided for the ser~ice water sy~tem.
t Protection for the SWS should be considered during I 1 the integrated assessment e aluation.
-*11-
- f.
Diesel Generator Cooling Water CCGCW) System The DGCW system serves the diesel generators and the room coolers for HPCI and LPCI, all of which are considered necessary for safe shutdown.
The system's pumps are located in the cribhouse 8 feet below ground level in an area surrounded by 3 foot thick reinforced concrete walls and are protected from above by a 2 foot thick reinforced concrete slab.
The remaining part of the system's piping and valves traverse t~ and from the missile protected diesel and reactor build-ings via p reinforced concrete tunnel that runs below ground affording adequate tornad~ ~issile protection.
Based on the above we conclude the DGCW system is adequately protected against tornado missiles.
- g.
Emergency Power System - Auxiliary Electrical Equip-ment Room The auxiliary electrical switchgear room houses equipment and systems essential for safe shutdown including the reactor protection system motor-genera-tors and instrumentation and essential relays and'
, 2 -
switchgear.
It is Located at elevation 517'6" in the east end of the turbine building.
Since the east end of the turbine building is constructed of reinforced concrete* ~t Least 12 inches *thi*ck,- u*p to*
elevation 651'6" the auxiliary electrical equipment room is protected from horizontal missiles.
It is also protected from postulated vertical missiles by no Less than 12 inch concrete slabs above.
Based on our review we conclude that the auxiliary elec-trical equipment room is adequately protected against tornado missiles.
t
- h.
Station Batteries The ~tation batteries.supply power for operation of vit~l control.circuits.
Three.stat*ion battery systems are provided.
They are located in a ventilated battery room having co~crete block walls.
The concrete block walls are not sufficient to protect :against the two postulated missiles.
We therefore, conclude that inadequate missile~protection is provided for the station battery systems.
- i.
Emergency Diesel Generators The emergency diesel ~enerators provide emergency power and one unit is assumed to be adequete for safe shutdown in the event of a tornado.
One is housed tn a separate reinforced concrete building that orovides adequate pr~tertion except for the diesel air intake and exhaust.
The other diesel generator is located in a portion of the turbine building that pro-vides adequate protection e~cept for the air intake and exhaust.
The fuel oil storage tank and exterior cabling tp and from the diesel generators are protected against tornado mtsstles by virtue of their location underground.
Based on our review we conclude that the diesel generators except for the intakes and exhausts are adequately protected against tornado missiles.
The need for providing protection of the
§ir i~take~ and exhaust silen~ers sho~*ld be evalY~ted durinp cthe intPprated a~se!sment Of the Dresden 2 plant.
- j.
Instrumentation and Control for Safe Shutdown Equipment Instrumentation and control for safe shutdown equip-ment is located in the control room.
The majority of the cables are routed from.the control room through the missile protected portions of the turbine building and into the reactor building.
Other cables are routed to the switchgear located in the protected portion of the turbine: building.
14 -
We conclude that *the reactor building, turbine build-ing and the control room enclosure walls (located in the turbine building) provide adequate tornado missi l£ protection for the essential cables located in these structures because they provide at least 12 inches of reinforced concrete for protection.
- k.
Space Coolers The space coolers serving safe shutdown equipment are located within compartments housing the safe shutdown /quipment and would have the same protection afforded the safe shutdown equipment as discussed above.
We therefore conclude that the tornado protection provided these units is adequate.
- l.
Reactivity Control System The reactivity control system consists of a control rod drivei.system and the standby liquid control system.
Essential components for these systems are located in the reactor building and drywell.
These components are adequately protected by the 1~
i n ch th i ck reactor bu i l ding w a l ls and th ej dry we l l enclosure.
All cables for the reactivity! control systems are routed from the control room ~hrough a protected portion of the turbine buildi~g and to I
I.,
i j
15 -
the reactor building.
Based on the above considera-tions, we conclude that the reactivity control system is adequately protected against the effects of tor-nado missiles.
- m.
Control Room The control room is adequately protected against the effects of tornado missiles as discussed in Item 3.j above.
However, the control room HVAC system may be vulnerable to damage from tornado missiles.
The safety-related ventilation systems in the reactor building ~onsist of cubicle coolers which are located in protected areas.
The control room ventilation system outside air intake and exhaust ducts are not protected from tornado missi Les.
As a result of a study conducted by Bechtel Power Corporation, "Control Room Habitability Study," a modification is being implemented to add a redundant safety related system to the control room HVAC system.
The equipment is to be installed in such a manner that it will be protected against tornado missiles.
We, therefore, con c l u de t ha t w h.i.l.e. t e e p resent s y st em i s : not pf' o t e ct e d
' I agai~st tor~ad6 missil~s, the proposed mo~ifications shoul~ provide-accept~ble protection.
16 -
- 4.
Systems Whose Failure May Re~ult in the Release of Unacceptable Amounts of Radioactivity
- a.
Standby Gas Treatment Syst~m The standby gas treatment system CSGTS) is not necessary for safe shutdown but is necessary to minimize the release of radioactive materials.
The SGTS units are located on the turbine building mezzanine floor.
The floor immediate~y above this area at elevation 561'6" is an 8 inch reinforced concrete slab.
Above that is the 3 1/2" precast concrete roof slab.
The discharge ducts are routed f
down through protected areas of the turbine building and then underground Cat least 13.feet) to the plant stack which can withstand the postulated missiles and still *remain functional.
Based on our review we conclude that the SGTS is adequately protected against th~ telephone pole missile by virtue of its location above ground and against the steel rod by virtue of the surrounding structures.
- b.
Spent Fuel Pool Cooling System The spent fuel pool cooling system CSFPCS) removes residual heat from the spent fuel stored in the p~ol.
The SFPCS consists of two pumps and two heat exchangers~
and the associated piping and valves.
The spent fuel
- pool cooling pumps draw water from the pool, and
~-
circulate the water through the heat exchangers, returning it to the pool.
The top of the spent fuel pool is located on the reactur building refueling floor, which is enclosed by the reactor building superstructure starting at elevation 613 feet.
Of the two postulated missiles, only the one inch steel rod could be expected to impact the top of the spent fuel pool.
Utility poles are assumed to reach heights not greater than 30 feet above the maximum grade el~vation within one-half.mile of the plant.
The minimum 18 inch thick reactor building walls provide adequate protection against the utility pole and other missiles up to an elevation of 613
- feet.
It is possible for the one inch steel rod to penetrate the spent fuel pool area through the reactor building superstructure above the 613 foot elevation.
- However, the effects of the one inch steel ro~ have been eva-luated in previous analyses (e.g., within staff testimony and responses to interrogations o~ spent fuel pool protection against tornado missilis for North Anna and Palisades).
The results indii:ate t:hat the potential off*site radiological consequences.:are well within 10 CFR Part 100 guidelines.
18 -
In view of the above considerations, we conclude that the Dresden 2 spent fuel'pool is acceptable regarding tornado missile protection.
The spent fuel pool cooling system consists of two pumps, two heat exchangers, filters, piping, valves and instrumentation.
Most of this equipment is located in the reactor building and is protected by the 18 inch thick reinforced concrete structure.
The spent fuel pool cooling system is cooled by the reactor building ctosed cooling water CRBCCW) system.
All RBCCW system components are located in the reactor building.
We therefore conclude that adequate tornado missile protection is afforded the spent fuel pool cooling system ~hd the RBCtW, However, the RBCCW heat exchangers reject spent fuel heat to the service w~ten system which is not adequately protected Csee Item 3.e).
In our judgement, failure of these syste~s because of tornado missiles will not result in sign~ficant radiological consequences *
- c.
Gaseous Radwaste Treatment Sy~tem The Appendix to Regulatory Guide 1.117 recommends that por-tions of the gaseous radwaste treatment storage systems whose failure due to tornado ~ffects could result in poten-tial*offsite exposures greater than 25 percent of the guidelines exposures of 10 CFR Part 100 be protected against tornado effects including tornado missiles.
Although the failure of the gaseous radwaste treatment systems at Dresden 2 would not result in exceeding these limits we have evaluated their protection.
The gaseous radwaste treatment systems include equipment located within the radwaste buil~ing and the holdup volume of the off-gas exhaust stack.
The radwaste building is constructed of reinforced con-crete with a thickness of at least 12 inches.
The gland seal hold up volume is located at the bottom of the exhaust stack which is constructed of 33 inc.h reinforc:ed concrete.
We, t h e r e f o r e, c on c l u d e t h a t a de q u a t e t o r n a do ;m i s s i l e p r o -
I tection is provided for the gaseous radwaste tjreatment system.
l J 'i
. j I
j I
j
~
. l tl.'1JJ **
20 -
IV.
CONCLUSIONS Based on our evaluation of the information provided by the Licensee, we conclude that the following portions of the Dres-den 2 are adequately protected from the effects of tornado missiles:
- 1.
Reactor coolant pressure boundary;
- 2.
Reactor and individ~al fuel assemblies Located within the core;
- 3.
Automatic pr~sure relief system;
- 4.
Low pressure coolant injection/containment spray system;
- 5.
Containment cooling water system (emergency service water);
- 6.
High pressure coolant injection system;
- 7.
Diesel generator cooling water system;
- 8.
Safe shutdown cables (control room, turbine and reactor buildings);
- 9.
~mergency power system;.
- 10.
Space coolers;
- 11.
Control room;
- 12.
Reactivity control systems (including standby Liquid con-trol system);
- 13.
Spent fuel pool;
- 14.
Spent fuel pool cooling system;
' 15.
- 16.
Emergency d;esel generators (except for exhaust silencers)
- 17.
Gaseous waste treatment facilities.
Therefore, the above features meet the requirements General Design Criter;a 2 and 4 w;th respect to protection agaanst tornado missiles.
However, we have concludedthat Dresden 2 does not meet the current criteria for tornado miss;le, protection for the follow-ing areas:
- 1.
Service water system (for air condition;ng purposes>;
- 2.
Station battefy systems;
- 3.
Diesel engine ai~=intake ~nd *exhaust systems; The need for providing addit;onal tornado m;ssile protection for these systems should be evaluated during the intergrated assessment of the Dres~en 2 plant.
- .