核潜艇核事故艇内放射性应急防护和中子剂量快速评价研究

Study on emergency protection against radioactivity and the method of rapid assessing neutron doses in nuclear accident in nuclear submarine.

目的对核潜艇核事故条件下,建立应急工作允许时间T(m in)或在艇内等待救援的时间TD(m in)与空气中放射性活度浓度相互关系,以及研究中子吸收剂量在核潜艇现场可使用的评价方法。方法利用美国三哩岛核电站释放的放射性裂变产物分布计算出吸入单位活度放射性产生的待积有效剂量,利用剂量限值、每分钟的空气呼吸量建立T和TD的计算公式。中子吸收剂量可以根据中子照射后受照射者头顶处的24Naγ计数率快速评价。结果建立了以下关系式:T=1.41×109Econ以及TD≤-ln(1-7.64×109λEcon÷VI)/λ,这里Econ是控制剂量(SV),VI是空气中131I的活度浓度(Bq.m-3),λ=5.987×10-5/m in,是131I的衰变常数。全身平均中子吸收剂量-Dn(Gy)可以表达为:-Dn=3.47×105fFDN(t),其中,f是与照射和测量时间相关的系数,FD是单位中子注量产生的吸收剂量,N(t)是头顶处测量的24Naγ初始计数率。结论根据测量的VI或N(t)可以快速计算出T和TD,或评价-Dn。

Objective To establish the relationship between acceptable emergence-work time, T（min）, or the waiting rescue time, TD （min） , and the activity concentration in air in nuclear submarine when nuclear accidents happen, and to study the method of assessing neutron absorbed doses that can be suitable for using on site scene . Methods Using committed effective dose produced by inhalation unit activity radionuclide,based on the relative distribution of fission products in the nuclear accident of U. S. Three Island nuclear power station, the dose limits and the sum of inhaling air per minute, formulae calculating T and TD were established. The neutron doses could be assessed rapidly through the original counting rate of ^24Naγ at the head top of the irradiated person after irradiation. Results The following formulae have been established： T= 1.41×10^9Econ/VI and TD≤ -In（1 -7.64 × 10^9AEcon ÷ VI）/A ,where Ecoo is the dose limit （Sv）, VI is activity concentration of ^131I in air（ Bq·m^-3）, and λ= 5.87 × 10^-5/min is the decay constant of ^131I. The mean neutron absorbed dose,-↑Dn （Gy）, is expressed by -↑Dn = 3.47 × 10^5fFDN（ t ） ,where N（ t ） is the original counting rate of ^24Naγ at the top of the head , FD is the absorbed dose produced by per unit neutron flux , f is the coefficient relative to the prolonged-exposure time by neutron and the time measuring N（ t ）. Conclusions T and TD or -↑Dn, can be quickly calculated based on monitored VI or N（t）.