ML20041C155
| ML20041C155 | |
| Person / Time | |
|---|---|
| Site: | General Atomics |
| Issue date: | 02/22/1982 |
| From: | Mowry W GENERAL ATOMICS (FORMERLY GA TECHNOLOGIES, INC./GENER |
| To: | John Miller Office of Nuclear Reactor Regulation |
| References | |
| 38-67-3052, NUDOCS 8202260275 | |
| Download: ML20041C155 (8) | |
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JNERAL ATOM a="' ' '-- :A ~ % w+w --m+ -- -
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- wem, GENERAL ATOMIC COMPANY P.O. 00X 81608 In Reply SAN DIEGO, CALIFORNIA 92138 (714) 455-3000 February 22, 1982 Refer To: 38/67-3052 3
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N E C W,. 3' Mr. James R. Miller, Chief
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Standardization and Special Projects Branch
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Division of Licensing Nuclear Regulatory Commission g
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Washington, D.C. 20555
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Subject:
Revision to Application for License Amendment:
50-89 and 50-163; Licenses R-38 and R-67 respectively.
Dear Mr. Miller:
As you may be aware, Dr. Whittemore, our reactor physicist-in-charge, has several recent telephone discussions on the above referenced application for license amendments with Jim Wilson of your staff and M. Urizer from Los Alamos. These discussions culminated in the line-by-line review of the suggested clarifying changes in the related Technical Specifications for the Mark I and Mark F reactors and the corresponding Safety Analyses.
It is our understanding that you will initiate the agreed upon changes in the Technical Specifications but will confirm with us the final changes before their issue. On the other hand, we agreed to make the agreed upon changes in the two Safety Analyses and to submit the revised sections.
In this submittal, we present new pages with the slightly revised wording suggested by M. Urizer for the Safety Analyses. These changes basically describe more correctly the modern propellants. We trust that the revisions will be sufficient and that the requested license amendments can nov be issued in a timely manner.
If you have additional questions, please feel free to call us.
Very truly yours, William R. Mowry Licensing Administrator Nuclear Materials Control Division WPJi:he
Attachment:
Revised pages to Application for License Amendment,
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8202260275 820222 PDR ADOCK 05000089 P
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SAFETY ANALYSIS Neutron Radiography of Class B and C Explosive Devices at Mark I (R-38)
1.0 INTRODUCTION
This Safety Analysis supports the request to extend the quantity of ex-plosive that can be radiographed in the Mark I Facility from 0.2 pound (91 gram) equivalent TNT to 1.0 pound (454 gm) equivalent TNT. The type of ex-plosive devices remains the same; namely Class B and/or Class C explosives which are mainly propellant type explosives that do not detonate or produce shock waves, blast, or fragmentation in the normal mode of operation. As a group, Class B explosives are composed of a mixture of chemicals or chemical compounds that burn rapidly when ignited and are capable of producing con-siderable pressure but will not detonate.
In Attachment 2, the reader can find a copy of the current Bureau of Explosives' Tariff No. BOE-6000-A, issued May 1981, which describes Classes A, B and C explosives.
2.0 IRRADIATION CONDITIONS For the radiography of explosive devices totaling at one time in the beam no more than 91 gram equivalent TNT, the reactor control system will be protected by a single blast shield of 3/4-inch plywood plus 1/4-in. steel layer inserted between the explosive device and-the control system. The top l
of the beam port will be closed with an aluminum sheet of approxinately 1/8-inch thickness to prevent the device from falling to the bottom of the port and hence near (%16 inches) to the top of the core. An apron will l
protect the top of the reactor pool so that no explosive device (s) can fall through the tank water to the vicinity of the reactor core. A partial vall 56 inches high made from solid concrete blocks 15-inches thick located near i
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A the reactor pool protects the reactor operator and other personnel in the area. A massive beam stop will be placed above the explosive device. This beam stop is 20-inch diameter and 36-in. high with a 10-in. reentrant hole.
The stop contains several inches of lead with the remainder paraffin and weighs about 800 pounds.
For the radiography of explosive devices totaling more than 91 grams equivalent TNT but no more than 1.0 pound, the protection against the ef-fects of an accidental explosion are the following:
a.
Protection from the excess pressure will be provided by a wooden enclosed region at the top of the beam port constructed from 3/4-in.
plywood with an aluminum window at the bottom and top to pass the neutron beam. This will absorb the shock and such recoiling de-vices as occur and will direct the over pressure out one side of the enclosure and away from the reactor control system, operator, and other personnel in the area.
b.
The top of the beam port will be sealed with an aluminum plate of
~1/8-in. thickness to prevent explosive devices from falling in-side to the bottom of the beam port.
An apron will protect the top of the reactor pool so that no ex-c.
plosive device (s) can fall through the tank water to the vicinity of the reactor core.
d.
The partial wall of concrete blocks described above will also be in place to protect personnel, A massive beam stop also described above will be mounted above e.
the shock absorbing enclosure to control the radiation.
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3.0 STORAGE OF EXPLOSIVES The maximum amount of Class B or Class C explosive devices that will be stored for use.with the Mark I NR facility will be in accordance with the applicable regulations for~the City and County of San Diego. The amount of explosive stored outside the Mark I reactor room will be included in the.
100-pound limit justified separately for-the Mark F (R.-67) reactor facility.
(See Safety Analysis for NR of Explosives with Mark F Reactor). The require-ments for acceptable storage (quantity and distance) will also be the same as those established for the Mark F Facility.
No explosive beyond the amount approved for irradiation in the NR beam at one time shall be stored in the Mark I reactor room. Transport of the explosive to be radiographed shall be with a dolly or cart providing a box-like volume constructed from 3/4-in. plywood open on one side. This transportation system shall be used to transport the explosives from the outside preparation area to the reactor beam port and return'to the outside.
The procedures for handling and radiographing'the explosives described herein will be prepared and submitted for approval to the Reactor' Safety Committee and the General Atomic Site Industrial Safety Supervisor prior to conduct of NR operations.
4.0 MAXIMUM CREDIBLE ACCIDEhT
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The energy release by the discharga of a typical Class.C explosive device is about 1750 calories for 25 grains (1.62 grams) of explosive. The metal cladding dissipates the major amount of the released energy and is shock resistant.
Class B as well as Class C explosives in normal use are not designed to detonate and thus will not produce a shock wave, blast, or fragmentation.
It burns vigorously and, if contained..can produce large pressure. When used
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- -in a jet' thruster, a directed thrust-is produced but in a unit with up to one pound of propellant, the thrust and gas pressure is easily managed. The energy release of such a device is typically 18,000 BTU /lb and burns for about 1 second. With the exposure facility described above, the' exposure-volum-with its vent is _ large enough to prevent large pressure buildup dur-ing the propellant burn and will absorb the recoil of the case.
Since'no shock wave or fragmentation projectiles are anticipated, and since provision is made to prevent. explosive devices from reaching the core region, no chance exists to rupture the clad on any fuel elenent.
In the incredible incident where'all control rods are driven'out of the core.the consequences would be those_already analyzed and found to be safe.
for this and all other TRIGA reactors. The TRIGA prompt negative tempera-ture coefficient limits the peak pulsed or steady state power level to values already analyzed and licensed as routine operation for this facility..For the R-38 facility, routine pulses are made with reactivity insertions of
$3.00 which is about as large as the typical routine core excess reactivity in the facility. Furthermore, accidental flooding of the beam port has no effect on the core excess reactivity because the beam port is entirely _out-<
side the reflector: region of the core and does not alter the excess reactiv-ity. For details of the beam port location and construction see Reference 1.-
5.0 HAZARDS INDUCED IN EXPLOSIVES BY IRRADIATION
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As will be shown below, irradiation does not cause detonation or dis-charge of explosives and, furthermore, the changes in chemical composition caused by gamma rays, fast or tiow neutrons, are of no consequence until 6
doses >>10 Rads (gamma), >10 nyt (fast and slow neutrons) are applied.
i For NR where the gamma doses are typically a few hundred R and the neutron 10 doses are typically 10 -10 nyt, no significant radiation damage is pro-duced.
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2.2 Hazards induced in Explosives by Irradiation As will be shown below, irradiation does not cause detonation or dis-charge of explosives and, furthermore,'the changes in chemical composition caused by gnmma rays, fast or slow neutrons, are of no consequence until 16 doses >>10 Rads (gamma), >10 nyt (fast and slow neutrons) are applied.
For NR where the gamma doses are typically a few hundred R and the neutron 9
10 doses are typically 10 -10 nyt, no hazards are induced by NR.
The exposure times required to induce physical and chemical ek nges in th'e characteristics of explosives have been reviewed (Refs. 2 and 3).
It is important to separate two distinct possible effects due to irradiation of explosives. One is the possibility that the irradiation will induce a spontaneous detonation; the other is the change in the physical and/or chem-ical characteristic of the explosive caused by the irradiation.
On the for-mer, so far as the literature indicates and experience with neutron radio-graphy confirms, no explosive has been detonated by irradiation. In fact, since extremely high heating rates are required to deposit enough energy (50 to 60 cal / gram to explode RDX or TNT), it is impossible for steady-state neutron beams and/or gnmna ray beams to attain this energy deposition in a short time.
On the latter, however, irradiation does-cause changes in characteristics of explosives. These have been studied in great detail for gamnn irradiation (Ref. 3).
The available literature gives a considerably lecs clear picture of the situation for neutron irradiation, but the overall result is cicar; namely, neutron doses of >10 to 10 n/cm are required to cause measurable effects.
It may be useful to note that primary explosives such as lead azide are relatively more affected by nuclear irradiation but.not enough to af-feet their safety during neutron radiography. By contrast, nain charge explosives are relatively less affected. Of these, RDX and 72DC are espec-i ially stable. The tests that are used to evaluate chemical and physical characteristics as they depend on nuclear irradiation are described by Avrami and Voreck (Ref. 2); these tests are:
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v easily stopped by absorbing material such as a heavy blanket (e.g., bomb blanket) or by layers of steel totaling less than 1 inch thickness.
(d) Sympathetic Explosions Explosive devices containing an ounce or so of propellants are not likely to set off sympathetic explosions in neighboring devices.
In a deliberate test of this characteristic, Yuma Proving ground placed several cartridges each with 50 grams of EDC in contiguous configuration. When one cartridge was exploded, it moved only a few inches and did not cause explosion of any other cartridges.
.This test was repeated in several forms with the same result.
For safety, large quantities of propellant must nevertheless be' stored with prescribed weight-distance requirements (see for example Ref. 4).
Detonation devices vary considerably in their ability to set off.
sympathetic detonations. This variation depends not only on the type of high explosive but on its form, packing and containment vessel. Experimental tests are required for each given high ex-plosive, quantity, and device to determine the safe distance to prevent sympathetic detonation. For neutron radiography of devices containing high explosive (not Class C), only one device will be radiographed at one time.
3.
Safety Consideration for Radiography of Explosives with the Mark F Reactor The Mark F (R-67) reactor uses TRIGA fuel mounted in gridplates support-ed by an aluminum shroud from a movable bridge that mounts the control rod drives and supports the upper ends of the power nonitor channels.
The reactor is operated in a 26-foot deep tank with about 20 foot of water covering the reactor. Neutron radiography is performed with a vertical beam port assembly inserted into the reactor tank beside the reactor asseubly and extending to the top of the tank.
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pass unattenuated down the beam port. However, the presence of the 3-inch g
layer of aluminum HEXCEL lining the port will completely attenuate the shock wave before it reaches the bottom of the port.
Figure 4-2 shows the details of the lower end of the beam port.
In the unlikely event that any fragment were to pass through the upper end of the port and travel down the port, protection is provided by the steel layers (backed by foam) or by an equivalent mass of lead across the bottom of the enlarged section of the port and by the vertical steel plate on the reactor side of the port.
In the further unlikely event.that a fragment is able to hit the 2-inch neutron hole, it would still have to penetrate many inches of massive ductile material such as lead. Furthermore, this region is still several feet above the reactor core.
In view of all the protection provided there is no chance for damage at the bottom of the beam port and hence no likelihood for any damage to the core.
It may be useful to note that the NR beam port is positioned entirely outside the core and that a one-inch layer of water reflector completely isolates the beam port fram any significant effect on the core excess re-activity. Therefore accidental flooding of the beam port for whatever reason could produce no significant effect on the reactor perfornance.
3.2 Control and Mitigation of an Accidental Explosion The data in Section 2.2 shows that the explosion of a propellant causes only moderate concern because no shock wave or blast is expected in normal
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operation and, in the case of devices containing ~50 grams propellant, the recoil of the device itself is of little consequence.
It was also shown i
that detonations of devices containing 5 pounds or less of explosive produce shock waves, blasts, and fragment projectiles that are easily mitigated with only modest preparation. The detonations of devices of the sizes in ques-tion are routinely handled by bonb disposal squads in U.S. cities. A few layers of thick padding (such as horse blankets) will sufficiently danp and absorb the blast, shock wave and fragments. Therefore,,this approach is the one selected for protecting the reactor to be used during IF of high explosives.
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