ML20052A816
| ML20052A816 | |
| Person / Time | |
|---|---|
| Site: | Vallecitos Nuclear Center, 05000000, Vallecitos |
| Issue date: | 11/07/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20052A734 | List:
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| References | |
| FOIA-81-483 NUDOCS 8204290220 | |
| Download: ML20052A816 (6) | |
Text
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SAFETY EVALUAT10ll BY THE OFFICE OF 110 CLEAR REACTOR REGULAT GE!!ERAL ELECTRIC C0!' IPA!!Y_
NUCLEAR. TEST REACTOR (UTR)
VALLECITOS B0ltl!!G UATER REACTOR (VBUR)
ESADA-VALLECITOS EXPERllENTAL SUPERHEAT REACTOR (EVESR)
DOCKET 1:05. 50-73, 50-18 and 50-_183 Introduction On October 24, 1977, the Nuclear Regulatory Commission (llRC) issued an Order to Show Cause to tne General Electric Company (GE or licensee) as the licensee for the General Electric Test Reactor (GETR) at GE's Vallec'itos !!uclear Center (VNC) located near Pleasanton, California.
As presented in detail in the Order, the basis for this Order was newThe significanc geologic and seismologic information for the site.this informatio active, the potential ground accelerations at the site are significantly greater than was previously thought to be the case, and offsets of the ground surface, or surface faulting, could be expected to occur at the.
site in the event of a seismic event.
The order acknowleaged that there are a number of other facilities at the Ylic site, including the following reactor facilities licensed under 10the 11 j
CFR Part 50 of the Commission's regulations:
the Vallecitos Boiling Water Reactor (VBWR), and the ESADA-Yallecitos Exper l
mental Superheat Re' actor (EVESR). As stated in the order, prelininary assess-
- ment,s indicated that the potential failure of the structur h
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,of guidelines set forth in Commission regulations) hou.ever, t e s a indicated that it would consider,in greater vetail.the need for furtner The Order docunenteo action, if any, with respect to these facilities. it would orovide to 28, 1977, GE's agrecuent that by Friday, Octoder the I:RC staf f an assesscent of all 1:RC-licensed activities at the V!;C si te.
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2-This assessment for the other reactor facilities at the site was provided to the NRC staff by representatives of GE on Friday, October 28, 1077, in an oral and slide presentation. All the information thus presented will be submitted by GE in writing, under oath and affirmation within seven (7) days.
This prelininary Safety Evaluation is based on the information presented by GE on October 28, 1977.
It presents the NRC staff's evaluation of this information and draws interim conclusions relative to the safety of these other reactor facilities.
Discussion and Evaluation Nuclear Test Reactor (NTR)
The Nuclear Test Reactor (NTR) is a 100 kwt light water-cooled and coderated, graphite-reflected research reactor composed,of highly enriched urantun fuel. The fuel assemblies, cor.sisting of aluminum clad uraniur.i-aluminua alloy discs on aluminun shafts, are arrayed in a horizontal, cylinorical tank centered in a 5 foot cuoe of graphite with a central graphite thermal colu. n.
The reactor is equipped with four safety rods which automatically insert on a scram signal and three control rods (which do not insert on a scram signal.) which are driven horizontally along worm screws through one vertical face of the graphite into the reflector region immediately surrouncir.g the core annulus.
Cadaium poison sheets can be positioned in the graphite reflector around the core annulus.
The reactor is housed in a thick-walled concrete cell within Building 105 of the Vallecitos huclear Center.
The analyses performed previously for this facility did not include major disruption of the reactor and surrounding structures which could be post-ulated to result froa a very large earthquake.
Nevertheless, as discussed below, such an event would not be expected to lead to accidents whose consequences are.significantly different frem those presented in'crevious NRC staf f Saf ety E. valuation reports.
Analyses were performed, however, which involved the release 'of a significant anount of the fission products in the reactbr core. The potential off-site consequences, resulting from t.hese analyses would be within guidelin s set forth in Commission regul a tions.
Even if the reinforced concrete building in which the-reactor
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is located conpletely l'ost'iti integrity, nest damage mechanisms would not resuit ih fuel nelting or fission procuct release.
For exanple, compaction of the fuel would not result in the reactor going critical; water loss from the core container.wculd cause the reactor to becc,e sub-critical; and entry of water into the surrounding graphite matrix would result in the reactor being less able to sustain a chain reaction.
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r Decay heat removal following reactor scram and a loss of water would be by conduction and by radiation from the fuel to the surrounding graphite structure.
Also any contact of fuel and structures caused by earthquake damage would result in improved heat transfer. A criticality
. excursion which resulted in fuel melting would therefore be the only mechanism by which significant fission product release could occur.
In the meeting on October 28, 1977, representatives of the General Electric Company stated that if less than 80 cents in reactivity were available above the critical configuration, fuel heatup could not exceed about 600'F which is well belcw the fuel melt temperature (about 1200*F).
With the present license of the HTR, reactivity insertions greater than 80, cents could be avaliable if all control rods were postulated to be withdrawn as a result of earthquake dcmage.
GE stated that it has taken steps to prevent this. The reactivity available for insertion is now being restricted to 80 cents or less during ' reactor operation by administrative procedures, which include the use of poison shims between the reactor contciner and the surrounding graphite. This limitation on excess reactivity applies to the ccT,bined control rod and experiment worth.
GE also' stated that the poison shims would be fixed in place so that earthauake damage would 6ot cause their removal. With such restrictions on reactor operation we agree that possible reactivity insertions will be maintained at less than the value which could cause core melting and significant fission product release.
GE has indicated that the procedures imposed to limit reactivity insertion on NTR will not be modified without prior NRC approval.
The analyses described by GE will be formally submitted and will be reviewed in detail.
On the basis of our review of these analyses, we will revise the Technical Specifications if necessary to assure that significant fission product release to the offsite environment would not take place even for severe earthquake damage to the NTR facility.
In the interim, we have re-examined the previous analyses perforned by GE apd the staff for the HTR facility which did not take credit for the present reactivity lir;itations that GE has put into effect. A release of 10'i of the halocens and 100% of the noble cases was evaluated in our Safety Evaluation associated with. Anendaent Eo. 9 to the.Hllt license "g
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dated July 22, 1969.
With these assumptions, with a s'ite" boundary
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distance of about 1700 feet, and with the meteorology assumptions of Regulatory Guide 1.4, the offsite exposures woulo not result in consequences in excess of guidelines set forth in Commission regulations.
These calculations were mads assuming continuous operation of the facility at 100 kwt.
A significantly higher release fraction of halogens could still be tolerated when the actual operation of the facility (up to 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> per day) is considered. We therefore, conclude that continued operation until the analyses to be submitted by GE are reviewed is acceptable.
Deactivated Reactors at VHC Th'ere are two shut down and partially dismantied rcactor facilities having possession-only. licenses on the VNC site. The Vallecitos Boiling Water Reactor (VBWR) and _th'e ESADA-Vallecitos Experimental Superheat Reactor (EVESR).
The VBWR was an experimental 50 MWt prototype boiling water reactor used in the develooment of the comercial BWR power reactors. The VBWR was shut'down in 1963 and has been partially dismantled. All fuel has been renoved from the reactor and shipped of fsite and systems were flushed to renove loose radioactive crud.
All other sources of radioactivity have been removed from this facility except what remains of the induced radioactivity in the materials which make up the.struct'ures and components of the facility and which is not expected to be available for release as a result of a seismic event.
The reactor coolant system is sealed and filled with water. GE has stated that this water has an inventory of 2525 gallons and has measured the level of radioactive contamination in that water.
This contamination is on the order of 50 times MPC limits i2 CFR Part 20, Appendix B, Table II) for both Co-60 and for Cs-137.
The hydro-geology of the Vallecitos site following a severe earthcuake and the extent of dilution of this water in natural waters, should it accidently spill,' have.not been established. However, the staff concludes that the accidental spill of this liquid would not present-an undue
. safety hazard. As part of their emergency procedures, the licensee will be required to sample for activity in off-site potable water supplies should a liquid release occur and to reco raend interdiction measurep if they are indicated..The pess.ibility of from one to several orders,,
l of magnitude ~ dilution that is possible in natural vaters and the initial l
low concentrations of activity in the water in VSWP., combined with I
interdiction neasures, make it unlikely that exposures greater than those allowed from routine releases ur. der the provisions of 10 CFR Part 20 of the Conmission's regulations could occur.
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We have also reviewed the latest VBWR annual report submitted to us by GE on February 14, 1977.
That report contained radiation and contamination survey results which indicate that radioactivity levels in all areas surveyed were well below the limits for any significant safety concern. This reactor could not be returneo to operation without the specific approval and fortal licensing action bi NRC.
GE has informed us that there are no plans to r'eactivate this facility.
l The EVESR was an experinental 12.5 Mwt light water moderated BWR reactor i
designed to test sLperheat fuel elements by super heating saturated stean supplied from arother scurce (a gas fired boiler or the VBWR).The EVESR l
was shutdown in 1967 and all fuel and other mooile radioactive sources have been removed from this facility. The only remaining radioactivity l
is*.that which was induced in facility structures and components during operation prior.to the 1967 shutdown. This induced radioactivity is not expected to be available for release in the event of a seismic disturbance at the site. There is' no liquid inventory in the reactor coolant loop.
l Our review of the latest EVESP. annual report submitted to us February 14, l
1977 indicates that the levels of such inauced radioactivity still present were well below the limits for any significant safety concern.
GE has no plans to reactivate this reactor nor would GE be permitted to do so without specific NRC approval and a formal licensing action.
On the basis of our review of VBWR and EVESR as discussed above, we conclude that no action is required at this time with respect to the radioactivity present at these facilities.
Date:
November 7, 1977 l
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- r e A, Ef' CLOSURE 2 e
C0!lFIR'ATORY It!FOR:MTIO.'l Oft flTR TO GE SUBMITTED BY GE The General Electric Company (GE) will provide the following supporting informaticn about the NTR f acility:
- h. ' Provide an analysis that shows the fuel temperature will not exceed about 600*F when excess reactivity equal to S.00 is inserted into the core. The analysis should docutant the discussions of October 28, 1977, with regard to earthquake damage r.echanisms and decay heat rem. oval and present the scenarios which might lead to reactivity insertions.
2.
' Propose technical specifications limiting the excess reactivity available fo.r insertion during reactor operation.
Such a limitation should apply to the combined worth of the control rods ar.d any experiment.
3.
Provide a description.and analysis of the proposed attachment of experiments with the potential to introduce positive reactivity by removal or insertion into the core which precludes their moving independently of the core in the event of earthquahe damage and propose any associated technical specifications.
4.
Provide a description and analysis of the mechanism uhereby the poison shims cannot be removed as a result of earthquake damage.
5.
Propose technical specifications which require that the poison shims be properly attached prior to startup.
6.
Provide on-site meteorological data in the form of joint frequency distribution of uind speed, wind direction, and atmospheric stability.
7.
Verify that your emergency procedures for VCUR include provisions for sampling wa,ter supplies in the' area, if a release of radioactive li4uid should occur.
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