ML20037B661
| ML20037B661 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/03/1961 |
| From: | Bryan R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20037B660 | List: |
| References | |
| NUDOCS 8010270607 | |
| Download: ML20037B661 (3) | |
Text
--.
en U
1:
-l 5
DOCKET NO. 50-10
!~
HA2.ARDS ANALYSIS BY THE RESEARCH AND 00FR REl.CTOR S/r"TY ERI.!:CH i
..l DIVISION OF LICENSING AND REGULATICN i:.
IN THE MATTER OF i:
.l CCM'OWEALTH' EDISON COMPANT F
[.
- DRESDEN HIGH V03) TEST i
Introduction Commonwealth Edison in a letter dcted Septenber 6,1c61 proposed to cor. duct
[
c high core void content test in the Dresden reactor. Suppler.entary infernatien
~
concerning this test was submitted to the Cor:=ission in docu ents dated September
[..
13,1%1; September 16,1%1 (transmittal letter dated Septe:ber if,1961);
Septe=ber 22,1%1; and September 26, 1961.
l Description
[-
The test proposed involves operating the Dresden reactor ct less then rated I
power and at less than rated recirculation flow rate. With pri= cry eteem flev 1:
increased relative to secondary steam flow, this operation will result in a higher percentage of steam in the reactor core than for rated conditions.
Analysis
[.
p There cre two rajor safety areas involved in this test which were of concern j
i to the staff. One is the situation which vculd fc11cv the cudden c1ccure of the turbine c.dzission valve. Such closure would csure the rescter preuure to increate, an effect vnich tends to cause steam bubb1cs to ecllspre. The cellspec I.
of bubbles within the core, in turn, adds reactivity which causes the rec:ter iL I
po: er to rire rather sharply. The General Electric Co pany her analyzed thir i
trecrient fer the preposed teet conditiene usinC rn en 1ct cerputcr ric1rtien.
The rerultr of their cnalycic ir.diccte c r.ild trcr.rient vhich it unlikely to
.8.0.10270 (O2 L
n 2-cause any da= age to the reactor fuel elements.
Although the General Electric Co=pany has used, in thic entlycis, come o
assu=ptions and approximations which have not been proved to be entirely valid, the computer has ir the past simulated actual Dresden trantients fairly well.
i Furthermore, it is clear that there are design features of the plant, the effects i
of which were not censidered in the si=nitation, which eheuld act to prevent f
.t
{
core damage in the event of accidental closure of admissien valves. These l-features are an automatic primary steam bypass to the turbine and a high neutron flux level scram. In consideration of these factors we believe that the cudden closure of turbine admissien valves would not result in darece to reactor fuel and that this accident presents no hazard censiderations not described or i=nlicit i
in the license application, as amended.
The other principal area of concern is the possibility thct, with rore steem present in the core, a hydrodynamic instability could occur which would involve i
an oscillation of the stec= void content in various regicns of the core. Such l
an oscillation could result in coolant starvation of one er more ehtnnels, followed by clad melting and fission product release to the primary rycte=.
n Although various analytical approaches to this proble= in boiling v ter
['
reactors have been atte=pted, and although General Electric ectir.ctes thet the high void test conditiens vill not result in such an instability, it ir generally agreed that there is at present no rethod availtble Ly which cne ccn predict, pricr to the test, the onset or ncture of such oscillcticns with cny degree of certainty. The safety of such tests lies chiefly in the care vith which they are conducted, the ressurerents to be teken at each rtep, and the
- t. cursey of crtrtpoltting frc ressurerente et enc step tc detr.ine the tcfety c' rduncirc to the ncrt step.
~
q T
' 1 Particularly in the September 22 submittal, the licensee has described the a
measure:nents and extrapolations which will be made at each etep fer this purpose.
With the relatively :=n11 steps provided by the authori:ctien, cnd with the procedures and conditions for test termination described in the varicus sub-l' mittals, we believe that the in-core instn: mentation proposed for this test
[
should enable determination of approaching instability prior to the attninment of unstable conditions and in tira to terminate the test prior to core der.are.
i Experience with se=ewhat similar tests on other boiling water reacters supperts i-this belief.
p Y
Burnout heat fluxes for these low flow conditions have been estimated, i.
and checks vill be made to ensure that burnout ratios are naintained creater j
]
than the licensed value of 2.0.
We believe that the plans for this are i
acceptable.
Conclusion e
In crar opinion, the proposed test, conducted as deecribed in the above sub-I mittals and subject to the additional conditions contained in the proposed j
authorization, does not involve significant hazards not described or implicit in the license application as scended and that there is recscnable arrurtnce s
thtt thic test can be perfomed withcut undue ri:1: to Tne hn.ith cnd refety of the public.
I:
Dr.ter cetober 3, ic61 Robert H. Bryan, Acting Chief Reseerch & Fever Reactor Sr.fety I'rt.nch Divisien of Liccnrinr end 5:r.detien t
.