ML20133L201
| ML20133L201 | |
| Person / Time | |
|---|---|
| Site: | 07000036 |
| Issue date: | 07/24/1959 |
| From: | Zeitlin F MALLINCKRODT, INC. |
| To: | Johnson L US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20133G976 | List:
|
| References | |
| FOIA-96-343 NUDOCS 9701210522 | |
| Download: ML20133L201 (5) | |
Text
{{#Wiki_filter:l gp 70 - $ $ __ 4,, g M ALLINC K RO DT NUCLEAR SAINT LO UIS 7, M ISSOU RI CENTR AL 1-8980 U.S.A. e CO R PO R ATIO N j 1 July 214, 1959 M i fhs, \\ Q,\\ ,p -Q/- / ce N O . \\@g v - \\ -t '? Mr. Lyall Johnson gy 4 3 Chief, Licensing Branch Division of Licensing & Regulation 8 g\\[ U. S. Atomic Energy Commission Washington 25, D. C.
Dear Mr. Johnson:
Reference is made to your letter of June 26, 1959, 70-36, LRLtC E, requesting further information on the nuclear alam system at Hematite. Pbr background information concerning detailed design of the system and its components, reference to our letter of January 22,1959, and enclosures may be helpful. Your first question concerns the nsponse times of the system for various radiation levels. We have five radiation detectors located at different parts of the plant. They are wired in parallel with each other, and each is set to sound an alarm throughout the plant j should radiation rise to above ten Inilliroentgens per hour. The detector actually does not keep up with an almost instantaneous rise in radiation, but lags to the extent that only 63% of a sudden change is read two seconds after the change has occurred. Thus, if the change is to a point only slightly above 10 mr/ hour the detector will probably not set off an alam until some three or even four seo-onds after the change has occurred. On the other hand, should the change be to the region of, let us say,1000 mr/ hour the detector will trip in a very small fraction of a second after the advent of the rad-intion. This means that the naponse is practically instantaneous in the case of any severe outburst of radiation, although it is slightly delayed in the minimum cases. Your second intenst is in the fail-safe features of the alarm system. Our instruments are so constructed that while some electrical failures will cause the general alarm to sound, others will memly actuate signal lights. In this way, supported by our own close routine inspec-tion of the system, we hope to avoid false alarms and the confusion and anxiety they would cause, while still being immediately aware of any irregularity is the system. l ~ 9701210522 970114 PDR FOIA FLOYD96-343 PDR THE woRLD'S FIRST AND LEADING PRODUCER OF NUCLEAR FUELS 4* ' is )
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ro== w l l l, MALLlHCKRODT NUCLEAR CORPOR ATION i st. L evin i To Mr. Lyall Johnson Page 2 July 2h,1959 i. The instruments are set to operate nomally at a very low range of gamma radiation, most of which is provided by a tiny radiation source i within.each instrument case. A high level electrical contact is actuated if the range being measured by any one of the detectors rises to 10 mr/ hour, and a low level contact is actuated if the range falls to the neighborhood of approximately 0.2 'mr/ hour. If I the high level contact is actuated the alam sounds for evacuation of the work area and office. If the low level contact is actuated ' a light on the main panel of the alarm system comes on, indicating which detector sent in the signal. In addition, an amber light shows in the panel of the detector itself. Attached is a copy of Component Failure Study for Nuclear Measumments Corporation Model GA-2 Gamma Alam". While you will not be interested in each individual condition considered, the study as a whole indicates the overall high safety of our equipment. In the case of about half of the possible failures listed only the low level light will come on. In many of the other cases, the alam will sound. Thus, only the most unusual circumstance could render our equipment inoperative without our being imediately aware that something is wrong. The circuit diagram which accompanies the study is up-to-date. It differs in a few minor details from Drawing C-196 sent you on January 22, which is how supplanted. To adnimize failums, the vacuum tubes will be aplaced every six months on a paventative maintenance basis. The third tube, the photomultiplier, is too expensive to replace at this fmquency, but, as = Pined-above, shonM this tube became inactive the low contact signal 1$sht will come an, idhich will alsrt us to look for the trouble and change the tubei ~ Tho' system is tested weekly by the application'of a gaena source to one of the detector units. The five units are tested in this war in rotation; thus, the entire system is checked in actual praction ten ' times per year. . A practice drill for each work shift is planned to familiarise all, c . pereennelwith the procedure to be fo12 sued in ths event of.an.41mem.' ^ .Thereafter it is not espected thab'practioe' drills will be required '- vl.,i
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i FQses 1373 MALLINCKRODT NUCLEAR CORPORATION l St. Louis Tot Mr. Lyall Johnson Page 3 July 2h,1959 l We will be glad to furnish any further infomation which you may need for your evaluation of our pmposed procedums. Very truly yours,' [ Frank Zeitlin Assistant Vice Pmsident FZhO in quadruplicate Enclosums 8 4 a e e 1 e 9 e f ( ( 9 b l I b e e g s ~.. , b
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